Laboratory power supply on a 3528 board. Charger based on an ATX power supply. Attention! All work on power circuits must be carried out in compliance with safety precautions.

If earlier the element base of system power supplies did not raise any questions - they used standard microcircuits, today we are faced with a situation where individual power supply developers are starting to produce their own element base, which has no direct analogues among elements general purpose. One example of this approach is the FSP3528 chip, which is used in a fairly large number of system power supplies manufactured under the FSP brand.

The FSP3528 chip was found in the following models of system power supplies:

- FSP ATX-300GTF;

- FSP A300F–C;

- FSP ATX-350PNR;

- FSP ATX-300PNR;

- FSP ATX-400PNR;

- FSP ATX-450PNR;

- ComponentPro ATX-300GU.

Fig.1 Pinout of the FSP3528 chip

But since the production of microcircuits makes sense only in mass quantities, you need to be prepared for the fact that it can also be found in other models of FSP power supplies. We have not yet encountered direct analogues of this microcircuit, so if it fails, it must be replaced with exactly the same microcircuit. However, in retail trading network It is not possible to purchase the FSP3528, so it can only be found in FSP system power supplies that have been rejected for some other reason.

Fig. 2 Functional diagram of the FSP3528 PWM controller

The FSP3528 chip is available in a 20-pin DIP package (Fig. 1). The purpose of the microcircuit contacts is described in Table 1, and Fig. 2 shows its functional diagram. Table 1 shows for each pin of the microcircuit the voltage that should be on the contact when the microcircuit is turned on in a typical manner. A typical application of the FSP3528 chip is its use as part of a power supply control submodule personal computer. This submodule will be discussed in the same article, but a little lower.

Table 1. Pin assignments of the FSP3528 PWM controller

№	Signal	I/O	Description
		Entrance	Supply voltage +5V.
	COMP	Exit	Error amplifier output. Inside the chip, the pin is connected to the non-inverting input of the PWM comparator. A voltage is generated at this pin, which is the difference between the input voltages of the error amplifier E/A+ and E/A - (pin. 3 and pin. 4). During normal operation of the microcircuit, a voltage of about 2.4V is present at the contact.
	E/A-	Entrance	Inverting input of error amplifier. Inside the chip, this input is biased by 1.25V. The reference voltage of 1.25V is generated by an internal source. During normal operation of the microcircuit, a voltage of 1.23V should be present at the contact.
	E/A+	Entrance	Non-inverting error amplifier input. This input can be used to monitor the output voltages of the power supply, i.e. this contact can be considered a signal input feedback. In real circuits, a feedback signal is supplied to this contact, obtained by summing all the output voltages of the power supply (+3.3 V /+5 V /+12 V ). During normal operation of the microcircuit, a voltage of 1.24V should be present at the contact.
	TREM		Signal delay control contact ON/OFF (control signal for turning on the power supply). A timing capacitor is connected to this pin. If the capacitor has a capacity of 0.1 µF, then the turn-on delay ( Ton ) is about 8 ms (during this time the capacitor is charged to a level of 1.8V), and the turn-off delay ( Toff ) is about 24 ms (during this time, the voltage on the capacitor when it is discharged decreases to 0.6V). During normal operation of the microcircuit, a voltage of about +5V should be present at this contact.
		Entrance	Power supply on/off signal input. In the specification for power supply connectors ATX this signal is designated as PS - ON. REM signal is a signal TTL and is compared by an internal comparator with a reference level of 1.4V. If the signal R.E.M. becomes below 1.4V, the PWM chip starts up and the power supply starts working. If the signal R.E.M. is set to a high level (more than 1.4V), the microcircuit is turned off, and accordingly the power supply is turned off. The voltage at this pin can reach a maximum value of 5.25 V, although the typical value is 4.6 V. During operation, a voltage of about 0.2V should be observed at this contact.
			Frequency setting resistor of the internal oscillator. During operation, a voltage of about 1.25V is present at the contact.
			Frequency-setting capacitor of the internal oscillator. During operation, a sawtooth voltage should be observed at the contact.
		Entrance	Overvoltage detector input. The signal from this pin is compared by an internal comparator with an internal reference voltage. This input can be used to control the supply voltage of the microcircuit, to control its reference voltage, as well as to organize any other protection. In typical use, a voltage of approximately 2.5V should be present at this pin during normal operation of the microcircuit.
			Signal Delay Control Contact PG (Power Good) ). A timing capacitor is connected to this pin. A 2.2 µF capacitor provides a time delay of 250 ms. The reference voltages for this timing capacitor are 1.8V (when charging) and 0.6V (when discharging). Those. when the power supply is turned on, a signal PG is set to a high level at the moment when the voltage on this timing capacitor reaches 1.8V. And when the power supply is turned off, the signal PG is set to a low level at the moment when the capacitor is discharged to a level of 0.6V. The typical voltage at this pin is +5V.
		Exit	Power Good Signal - nutrition is normal. High level signal means that all output voltages of the power supply correspond to the nominal values, and the power supply is operating in normal mode. Low level signal indicates a fault in the power supply. The state of this signal during normal operation of the power supply is +5V.
	VREF	Exit	High precision voltage reference with ±2% tolerance. A typical value for this reference voltage is 3.5 V.
	V 3.3	Entrance	Overvoltage protection signal in the +3.3 V channel. Voltage is supplied to the input directly from the +3.3 channel V.
		Entrance	Overvoltage protection signal in channel +5 V. Voltage is supplied to the input directly from channel +5 V.
	V 12	Entrance	Overvoltage protection signal in channel +12 V. Voltage from channel +12 is applied to the input V through a resistive divider. As a result of using a divider, a voltage of approximately 4.2V is established on this contact (provided that there are 12 in channel V voltage is +12.5V)
		Entrance	Input for additional overvoltage protection signal. This input can be used to organize protection via some other voltage channel. In practical circuits, this contact is used most often to protect against short circuits in channels -5 V and -12 V . In practical circuits, a voltage of about 0.35V is set at this contact. When the voltage rises to 1.25V, the protection is triggered and the microcircuit is blocked.
			"Earth"
		Entrance	Input for adjusting the “dead” time (the time when the output pulses of the microcircuit are inactive - see Fig. 3). The non-inverting input of the internal dead time comparator is biased by 0.12 V by the internal source. This allows you to set the minimum value of the “measure” time for output pulses. The “dead” time of the output pulses is adjusted by applying to the input DTC constant voltage ranging from 0 to 3.3V. The higher the voltage, the shorter the operating cycle and the longer the “dead” time. This contact is often used to create a “soft” start when the power supply is turned on. In practical circuits, a voltage of approximately 0.18V is set at this pin.
		Exit	Collector of the second output transistor. After starting the microcircuit, pulses are formed on this contact, which follow in antiphase to the pulses on contact C1.
		Exit	Collector of the first output transistor. After starting the microcircuit, pulses are formed on this contact, which follow in antiphase to the pulses on contact C2.

Fig.3 Basic parameters of pulses

The FSP3528 chip is a PWM controller designed specifically for controlling a push-pull pulse converter system unit power supply for a personal computer. The features of this microcircuit are:

- presence of built-in protection against excess voltage in channels +3.3V/+5V/+12V;

- presence of built-in protection against overload (short circuit) in channels +3.3V/+5V/+12V;

- the presence of a multi-purpose entrance for organizing any protection;

- support for the function of turning on the power supply using the PS_ON input signal;

- the presence of a built-in circuit with hysteresis for generating the PowerGood signal (power supply is normal);

- presence of a built-in precision reference voltage source with a permissible deviation of 2%.

In those power supply models that were listed at the very beginning of the article, the FSP3528 chip is located on the power supply control submodule board. This submodule is located on the secondary side of the power supply and represents printed circuit board, placed vertically, i.e. perpendicular to the main board of the power supply (Fig. 4).

Fig.4 Power supply with FSP3528 module

This submodule contains not only the FSP3528 chip, but also some elements of its “piping” that ensure the functioning of the chip (see Fig. 5).

Fig.5 FSP3528 submodule

The control submodule board has double-sided mounting. On the back side of the board there are surface-mounted elements - SMD, which, by the way, give the most problems due to the not very high quality of soldering. The submodule has 17 contacts arranged in one row. The purpose of these contacts is presented in Table 2.

Table 2. Assignment of contacts of the FSPЗ3528-20D-17P submodule

№	Contact assignment
	Output rectangular pulses intended for control power transistors power supply

	Power supply start input signal ( PS_ON)

	Channel voltage control input +3.3 V
	Channel voltage control input +5 V
	Channel voltage control input +12 V
	Short circuit protection input
	Not used
	Power Good Signal Output
	Voltage regulator cathode AZ431
	AZ 431
	Regulator reference voltage input AZ 431
	Voltage regulator cathode AZ431
	Earth
	Not used
	Supply voltage VCC

On the control submodule board, in addition to the FSP3528 chip, there are two more controlled stabilizers AZ431(analogous to TL431) which are in no way connected with the FSP3528 PWM controller itself, and are designed to control circuits located on the main board of the power supply.

As an example of the practical implementation of the FSP3528 microcircuit, Fig. 6 shows a diagram of the FSP3528-20D-17P submodule. This control submodule is used in FSP ATX-400PNF power supplies. It is worth noting that instead of a diode D5, a jumper is installed on the board. This sometimes confuses individual specialists who are trying to install a diode in the circuit. Installing a diode instead of a jumper does not change the functionality of the circuit - it should function both with a diode and without a diode. However, installing a diode D5 may reduce the sensitivity of the short circuit protection circuit.

Fig.6 Diagram of the FSP3528-20D-17P submodule

Such submodules are, in fact, the only example of the use of the FSP3528 chip, so a malfunction of the submodule elements is often mistaken for a malfunction of the chip itself. In addition, it often happens that specialists are unable to identify the cause of the malfunction, as a result of which the microcircuit is assumed to be faulty, and the power supply is put aside in the “far corner” or even written off.

In fact, failure of a microcircuit is quite rare. Submodule elements are much more susceptible to failure, and, first of all, semiconductor elements(diodes and transistors).

Today, the main malfunctions of the submodule can be considered:

- failure of transistors Q1 and Q2;

- failure of capacitor C1, which may be accompanied by its “swelling”;

- failure of diodes D3 and D4 (simultaneously or separately).

Failure of the remaining elements is unlikely, however, in any case, if a malfunction of the submodule is suspected, it is necessary to first check the soldering of the SMD components on the printed circuit board side.

Chip diagnostics

Diagnostics of the FSP3528 controller is no different from diagnostics of all other modern PWM controllers for system power supplies, which we have already talked about more than once on the pages of our magazine. But still, once again, in general terms, we will tell you how you can make sure that the submodule is working properly.

To check, it is necessary to disconnect the power supply with the submodule being diagnosed from the network, and apply all the necessary voltages to its outputs ( +5V, +3.3V, +12V, -5V, -12V, +5V_SB). This can be done using jumpers from another, working, system power supply. Depending on the power supply circuit, you may also need to supply a separate supply voltage +5V on pin 1 of the submodule. This can be done using a jumper between pin 1 of the submodule and the line +5V.

At the same time, on contact C.T.(cont. 8) a sawtooth voltage should appear, and on the contact VREF(pin 12) a constant voltage should appear +3.5V.

Next, you need to short-circuit the signal to ground PS-ON. This is done by shorting to ground either the contact of the output connector of the power supply (usually the green wire) or pin 3 of the submodule itself. In this case, rectangular pulses should appear at the output of the submodule (pin 1 and pin 2) and at the output of the FSP3528 microcircuit (pin 19 and pin 20), following in antiphase.

The absence of pulses indicates a malfunction of the submodule or microcircuit.

I would like to note that when using such diagnostic methods, it is necessary to carefully analyze the circuitry of the power supply, since the testing methodology may change slightly, depending on the configuration of the feedback circuits and protection circuits against emergency operation of the power supply.

U computer unit power supply, along with such advantages as small size and weight with a power of 250 W and above, there is one significant drawback - shutdown in case of overcurrent. This drawback does not allow the power supply unit to be used as a charger for a car battery, since the charging current of the latter reaches several tens of amperes at the initial moment of time. Adding a current limiting circuit to the power supply will prevent it from shutting down even if there is a short circuit in the load circuits.

Charging a car battery occurs at a constant voltage. With this method, the charger voltage remains constant throughout the charging time. Charging the battery using this method is in some cases preferable, since it provides a faster way to bring the battery to a state that allows the engine to start. The energy reported at the initial charging stage is spent primarily on the main charging process, that is, on the restoration of the active mass of the electrodes. The strength of the charging current at the initial moment can reach 1.5C, however, for serviceable but discharged car batteries such currents will not bring harmful consequences, and the most common ATX power supplies with a power of 300 - 350 W are not able to deliver a current of more than 16 - 20A without consequences. .

The maximum (initial) charging current depends on the model of the power supply used, the minimum limit current is 0.5A. The idle voltage is regulated and can be 14...14.5V to charge the starter battery.

First, you need to modify the power supply itself by turning off its overvoltage protections +3.3V, +5V, +12V, -12V, and also removing components not used for the charger.

For the manufacture of the charger, a power supply unit of the FSP ATX-300PAF model was selected. The diagram of the secondary circuits of the power supply was drawn from the board, and despite careful checking, minor errors, unfortunately, cannot be excluded.

The figure below shows a diagram of the already modified power supply.

For comfortable work with the power supply board, the latter is removed from the case, all wires of the power supply circuits +3.3V, +5V, +12V, -12V, GND, +5Vsb, feedback wire +3.3Vs, signal circuit PG, power supply switching circuit PSON are unsoldered from it , fan power supply +12V. Instead of a passive power factor correction choke (installed on the power supply cover), a jumper is temporarily soldered in, the ~220V power wires coming from the switch on the rear wall of the power supply are desoldered from the board, and the voltage will be supplied by the power cord.

First of all, we deactivate the PSON circuit to turn on the power supply immediately after applying mains voltage. To do this, instead of elements R49, C28, we install jumpers. We remove all elements of the switch that supplies power to the galvanic isolation transformer T2, which controls power transistors Q1, Q2 (not shown in the diagram), namely R41, R51, R58, R60, Q6, Q7, D16. On the power supply board, the collector and emitter contact pads of transistor Q6 are connected by a jumper.

After this, we supply ~220V to the power supply, make sure it is turned on and is operating normally.

Next, turn off the control of the -12V power circuit. We remove elements R22, R23, C50, D12 from the board. Diode D12 is located under the group stabilization choke L1, and its removal without dismantling the latter (altering the choke will be written below) is impossible, but this is not necessary.

We remove elements R69, R70, C27 of the PG signal circuit.

Then the +5V overvoltage protection is turned off. To do this, pin 14 of the FSP3528 (pad R69) is connected by a jumper to the +5Vsb circuit.

A conductor is cut out on the printed circuit board connecting pin 14 to the +5V circuit (elements L2, C18, R20).

Elements L2, C17, C18, R20 are soldered.

Turn on the power supply and make sure it is working.

Disable overvoltage protection +3.3V. To do this, we cut out a conductor on the printed circuit board connecting pin 13 of the FSP3528 to the +3.3V circuit (R29, R33, C24, L5).

We remove from the power supply board the elements of the rectifier and magnetic stabilizer L9, L6, L5, BD2, D15, D25, U5, Q5, R27, R31, R28, R29, R33, VR2, C22, C25, C23, C24, as well as elements of the OOS circuit R35, R77, C26. After this, we add a divider from resistors 910 Ohm and 1.8 kOhm, which generates a voltage of 3.3V from a +5Vsb source. The middle point of the divider is connected to pin 13 of the FSP3528, the output of the 931 Ohm resistor (a 910 Ohm resistor is suitable) is connected to the +5Vsb circuit, and the output of the 1.8 kOhm resistor is connected to ground (pin 17 of the FSP3528).

Next, without checking the functionality of the power supply, we turn off the protection along the +12V circuit. Unsolder the chip resistor R12. In the contact pad R12 connected to the pin. 15 FSP3528 drills a 0.8 mm hole. Instead of resistor R12, a resistance is added, consisting of series-connected resistors of 100 Ohm and 1.8 kOhm. One resistance pin is connected to the +5Vsb circuit, the other to the R67 circuit, pin. 15 FSP3528.

We unsolder the elements of the OOS circuit +5V R36, C47.

After removing the OOS in the +3.3V and +5V circuits, it is necessary to recalculate the value of the OOS resistor in the +12V R34 circuit. The reference voltage of the FSP3528 error amplifier is 1.25V, with the variable resistor VR1 regulator in the middle position, its resistance is 250 Ohms. When the voltage at the power supply output is +14V, we get: R34 = (Uout/Uop – 1)*(VR1+R40) = 17.85 kOhm, where Uout, V is the output voltage of the power supply, Uop, V is the reference voltage of the FSP3528 error amplifier (1.25V), VR1 – resistance of the trimming resistor, Ohm, R40 – resistance of the resistor, Ohm. We round the rating of R34 to 18 kOhm. We install it on the board.

It is advisable to replace capacitor C13 3300x16V with a capacitor 3300x25V and add the same one to the place vacated by C24 in order to divide the ripple currents between them. The positive terminal of C24 is connected through a choke (or jumper) to the +12V1 circuit, the +14V voltage is removed from the +3.3V contact pads.

Turn on the power supply, adjust VR1 to set the output voltage to +14V.

After all the changes made to the power supply unit, we move on to the limiter. The current limiter circuit is shown below.

Resistors R1, R2, R4…R6, connected in parallel, form a current-measuring shunt with a resistance of 0.01 Ohm. The current flowing in the load causes a voltage drop across it, which op-amp DA1.1 compares with the reference voltage set by trimming resistor R8. The DA2 stabilizer with an output voltage of 1.25V is used as a reference voltage source. Resistor R10 limits the maximum voltage supplied to the error amplifier to 150 mV, which means the maximum load current to 15A. The limiting current can be calculated using the formula I = Ur/0.01, where Ur, V is the voltage on the R8 engine, 0.01 Ohm is the shunt resistance. The current limiting circuit works as follows.

The output of the error amplifier DA1.1 is connected to the output of resistor R40 on the power supply board. Until permissible current load is less than that set by resistor R8, the voltage at the output of op-amp DA1.1 is zero. The power supply operates in normal mode, and its output voltage is determined by the expression: Uout=((R34/(VR1+R40))+1)*Uop. However, as the voltage on the measuring shunt increases due to an increase in the load current, the voltage on pin 3 of DA1.1 tends to the voltage on pin 2, which leads to an increase in the voltage at the op-amp output. The output voltage of the power supply begins to be determined by another expression: Uout=((R34/(VR1+R40))+1)*(Uop-Uosh), where Uosh, V is the voltage at the output of the error amplifier DA1.1. In other words, the output voltage of the power supply begins to decrease until the current flowing in the load becomes slightly less than the set limiting current. The equilibrium state (current limitation) can be written as follows: Ush/Rsh=(((R34/(VR1+R40))+1)*(Uop-Uosh))/Rн, where Rsh, Ohm – shunt resistance, Ush, V – drop voltage across the shunt, Rн, Ohm – load resistance.

Op-amp DA1.2 is used as a comparator, signaling using the HL1 LED that the current limiting mode is turned on.

The printed circuit board (under the “iron”) and the layout of the current limiter elements are shown in the figures below.

A few words about parts and their replacement. Electrolytic capacitors installed on the FSP power supply board, it makes sense to replace them with new ones. First of all, in the rectifier circuits of the standby power supply +5Vsb, these are C41 2200x10V and C45 1000x10V. Do not forget about the forcing capacitors in the base circuits of power transistors Q1 and Q2 - 2.2x50V (not shown in the diagram). If possible, it is better to replace the 220V (560x200V) rectifier capacitors with new ones of larger capacity. The output rectifier capacitors 3300x25V must be low ESR - WL or WG series, otherwise they will quickly fail. As a last resort, you can supply used capacitors of these series with a lower voltage - 16V.

The precision op-amp DA1 AD823AN “rail-to-rail” is perfect for this scheme. However, it can be replaced by an order of magnitude cheaper op-amp LM358N. In this case, the stability of the output voltage of the power supply will be somewhat worse; you will also have to select the value of resistor R34 downward, since this op-amp has a minimum output voltage instead of zero (0.04V, to be precise) 0.65V.

The maximum total power dissipation of current measuring resistors R1, R2, R4…R6 KNP-100 is 10 W. In practice, it is better to limit yourself to 5 watts - even at 50% of maximum power their heating exceeds 100 degrees.

Diode assemblies BD4, BD5 U20C20, if they really cost 2 pcs., there is no point in replacing them with something more powerful; they hold up well as promised by the manufacturer of the 16A power supply. But it happens that in reality only one is installed, in which case it is necessary either to limit the maximum current to 7A, or to add a second assembly.

Testing the power supply with a current of 14A showed that after only 3 minutes the temperature of the winding of inductor L1 exceeds 100 degrees. Long-term trouble-free operation in this mode is seriously questionable. Therefore, if you intend to load the power supply with a current of more than 6-7A, it is better to remake the inductor.

In the factory version, the +12V inductor winding is wound with a single-core wire with a diameter of 1.3 mm. The PWM frequency is 42 kHz, with which the current penetration depth into copper is about 0.33 mm. Due to the skin effect at this frequency, the effective cross-section of the wire is no longer 1.32 mm 2, but only 1 mm 2, which is not enough for a current of 16A. In other words, simply increasing the diameter of the wire to obtain a larger cross-section, and therefore reducing the current density in the conductor, is ineffective for this frequency range. For example, for a wire with a diameter of 2 mm, the effective cross-section at a frequency of 40 kHz is only 1.73 mm 2, and not 3.14 mm 2, as expected. To effectively use copper, we wind the inductor winding with Litz wire. We will make Litz wire from 11 pieces of enameled wire 1.2 m long and 0.5 mm in diameter. The diameter of the wire can be different, the main thing is that it is less than twice the depth of current penetration into the copper - in this case, the cross-section of the wire will be used 100%. The wires are folded into a “bundle” and twisted using a drill or screwdriver, after which the bundle is threaded into a heat-shrink tube with a diameter of 2 mm and crimped using a gas torch.

The finished wire is completely wound around the ring, and the manufactured inductor is installed on the board. There is no point in winding a -12V winding; the HL1 “Power” indicator does not require any stabilization.

All that remains is to install the current limiter board in the power supply housing. The easiest way is to screw it to the end of the radiator.

Let's connect the "OOS" circuit of the current regulator to resistor R40 on the power supply board. To do this, we will cut out part of the track on the printed circuit board of the power supply unit, which connects the output of resistor R40 to the “case”, and next to the contact pad R40 we will drill a 0.8 mm hole into which the wire from the regulator will be inserted.

Let's connect the power supply to the +5V current regulator, for which we solder the corresponding wire to the +5Vsb circuit on the power supply board.

The “body” of the current limiter is connected to the “GND” contact pads on the power supply board, the -14V circuit of the limiter and the +14V circuit of the power supply board go to external “crocodiles” for connection to the battery.

Indicators HL1 “Power” and HL2 “Limitation” are fixed in place of the plug installed instead of the “110V-230V” switch.

Most likely, your outlet does not have a protective ground contact. Or rather, there may be a contact, but the wire does not go to it. There is nothing to say about the garage... It is strongly recommended that at least in the garage (basement, shed) organize protective grounding. Don't ignore safety precautions. This sometimes ends extremely badly. For those who have a 220V socket that does not have a grounding contact, equip the power supply with an external screw terminal to connect it.

After all the modifications, turn on the power supply and adjust the required output voltage with trimming resistor VR1, and adjust the maximum current in the load with resistor R8 on the current limiter board.

We connect a 12V fan to the -14V, +14V circuits of the charger on the power supply board. For normal operation of the fan, two series-connected diodes are connected to the +12V or -12V wire, which will reduce the fan supply voltage by 1.5V.

We connect the passive power factor correction choke, 220V power from the switch, screw the board into the case. We fix the output cable of the charger with a nylon tie.

Screw on the lid. Charger ready to go.

In conclusion, it is worth noting that the current limiter will work with an ATX (or AT) power supply from any manufacturer using PWM controllers TL494, KA7500, KA3511, SG6105 or the like. The difference between them will only be in the methods of bypassing the protections.

Download the limiter circuit board in PDF format and DWG (Autocad)

Even easier is converting a 350W ATX power supply to FSP3528 PWM. Chip 3528

It's even easier to convert a 350W ATX power supply to FSP3528 PWM

Assembled

at 40V - at least 7A.

texvedkom.org

Charger based on ATX power supply « circuitpedia

A computer power supply, along with such advantages as small size and weight with a power of 250 W and above, has one significant drawback - shutdown in case of overcurrent. This drawback does not allow the power supply unit to be used as a charger for a car battery, since the charging current of the latter reaches several tens of amperes at the initial moment of time. Adding a current limiting circuit to the power supply will prevent it from shutting down even if there is a short circuit in the load circuits.

First, you need to modify the power supply itself by turning off its overvoltage protections +3.3V, +5V, +12V, -12V, and also removing components not used for the charger.

The figure below shows a diagram of the already modified power supply.

For convenient work with the power supply board, the latter is removed from the case, all wires of the power circuits +3.3V, +5V, +12V, -12V, GND, +5Vsb, feedback wire +3.3Vs, signal circuit PG, circuit turning on the PSON power supply, fan power +12V. Instead of a passive power factor correction choke (installed on the power supply cover), a jumper is temporarily soldered in, the ~220V power wires coming from the switch on the rear wall of the power supply are desoldered from the board, and the voltage will be supplied by the power cord.

After this, we supply ~220V to the power supply, make sure it is turned on and is operating normally.

We remove elements R69, R70, C27 of the PG signal circuit.

Then the +5V overvoltage protection is turned off. To do this, pin 14 of the FSP3528 (pad R69) is connected by a jumper to the +5Vsb circuit.

A conductor is cut out on the printed circuit board connecting pin 14 to the +5V circuit (elements L2, C18, R20).

Elements L2, C17, C18, R20 are soldered.

Turn on the power supply and make sure it is working.

Disable overvoltage protection +3.3V. To do this, we cut out a conductor on the printed circuit board connecting pin 13 of the FSP3528 to the +3.3V circuit (R29, R33, C24, L5).

We unsolder the elements of the OOS circuit +5V R36, C47.

Turn on the power supply, adjust VR1 to set the output voltage to +14V.

After all the changes made to the power supply unit, we move on to the limiter. The current limiter circuit is shown below.

The output of the error amplifier DA1.1 is connected to the output of resistor R40 on the power supply board. As long as the permissible load current is less than that set by resistor R8, the voltage at the output of op-amp DA1.1 is zero. The power supply operates in normal mode, and its output voltage is determined by the expression: Uout=((R34/(VR1+R40))+1)*Uop. However, as the voltage on the measuring shunt increases due to an increase in the load current, the voltage on pin 3 of DA1.1 tends to the voltage on pin 2, which leads to an increase in the voltage at the op-amp output. The output voltage of the power supply begins to be determined by another expression: Uout=((R34/(VR1+R40))+1)*(Uop-Uosh), where Uosh, V is the voltage at the output of the error amplifier DA1.1. In other words, the output voltage of the power supply begins to decrease until the current flowing in the load becomes slightly less than the set limiting current. The equilibrium state (current limitation) can be written as follows: Ush/Rsh=(((R34/(VR1+R40))+1)*(Uop-Uosh))/Rн, where Rsh, Ohm – shunt resistance, Ush, V – drop voltage across the shunt, Rн, Ohm – load resistance.

Op-amp DA1.2 is used as a comparator, signaling using the HL1 LED that the current limiting mode is turned on.

The printed circuit board (under the “iron”) and the layout of the current limiter elements are shown in the figures below.

A few words about parts and their replacement. It makes sense to replace the electrolytic capacitors installed on the FSP power supply board with new ones. First of all, in the rectifier circuits of the standby power supply +5Vsb, these are C41 2200x10V and C45 1000x10V. Do not forget about the forcing capacitors in the base circuits of power transistors Q1 and Q2 - 2.2x50V (not shown in the diagram). If possible, it is better to replace the 220V (560x200V) rectifier capacitors with new ones of larger capacity. The output rectifier capacitors 3300x25V must be low ESR - WL or WG series, otherwise they will quickly fail. As a last resort, you can supply used capacitors of these series with a lower voltage - 16V.

The maximum total power dissipation of current measuring resistors R1, R2, R4…R6 KNP-100 is 10 W. In practice, it is better to limit yourself to 5 watts - even at 50% of the maximum power, their heating exceeds 100 degrees.

In the factory version, the +12V inductor winding is wound with a single-core wire with a diameter of 1.3 mm. The PWM frequency is 42 kHz, with which the current penetration depth into copper is about 0.33 mm. Due to the skin effect at this frequency, the effective cross-section of the wire is no longer 1.32 mm2, but only 1 mm2, which is not enough for a current of 16A. In other words, simply increasing the diameter of the wire to obtain a larger cross-section, and therefore reducing the current density in the conductor, is ineffective for this frequency range. For example, for a wire with a diameter of 2 mm, the effective cross-section at a frequency of 40 kHz is only 1.73 mm2, and not 3.14 mm2, as expected. To effectively use copper, we wind the inductor winding with Litz wire. We will make Litz wire from 11 pieces of enameled wire 1.2 m long and 0.5 mm in diameter. The diameter of the wire can be different, the main thing is that it is less than twice the depth of current penetration into the copper - in this case, the cross-section of the wire will be used 100%. The wires are folded into a “bundle” and twisted using a drill or screwdriver, after which the bundle is threaded into a heat-shrink tube with a diameter of 2 mm and crimped using a gas torch.

All that remains is to install the current limiter board in the power supply housing. The easiest way is to screw it to the end of the radiator.

Let's connect the power supply to the +5V current regulator, for which we solder the corresponding wire to the +5Vsb circuit on the power supply board.

Indicators HL1 “Power” and HL2 “Limitation” are fixed in place of the plug installed instead of the “110V-230V” switch.

We connect the passive power factor correction choke, 220V power from the switch, screw the board into the case. We fix the output cable of the charger with a nylon tie.

Screw on the lid. The charger is ready for use.

Download the limiter circuit board in PDF and DWG format (Autocad)

shemopedia.ru

conversion of ATX 350W to PWM FSP3528

Attention! All work on power circuits must be carried out observing safety precautions!

On the Internet you can find a lot of descriptions and methods for modifying ATX power supplies to suit your needs, from chargers to laboratory power supplies. The circuit diagram of the secondary circuits of the ATX power supply from the FSP brand is approximately the same:

There is no point in describing the details of the operation of the circuit, since everything is on the network; I will only note that this circuit has an adjustment of the short-circuit protection current. - VR3 trimmer, eliminating the need to add a current detector circuit and shunt. However, if there is such a need, then you can always add such a section of the circuit, for example, using a simple and common op-amp LM358. Often, in power supplies such as FSP, the PWM controller cascade is designed as a module:

As always, the secondary circuits on the board are desoldered:

We check the functionality of the “duty room” and the serviceability of the power inverter, otherwise make repairs first!

The schematic diagram of a converted 15-35 volt power supply looks like this:

A 47k trimmer resistor sets the required voltage at the feeder output. Highlighted in red on the diagram - delete.

Assembled

The radiator of the rectifier diodes is small in area, so it is better to increase it. According to the measurement results at a voltage of 28V, the converted power supply easily delivered 7A, taking into account its initial power of 350W, the calculated load voltage:

at 30V maximum current - no less than 12.5A
at 40V - at least 7A.

Of course, there is always the opportunity to buy a ready-made power supply of such power, but given the cost of such devices, a real economic justification for these costs is necessary...

atreds.pw

Chip BA3528FP

High quality BA3528FP microcircuit in our online store at retail and wholesale at a competitive price!

Until recently, the BA3528FP microcircuit, offered by our online store, was difficult to buy anywhere. But with the advent of specialized stores such as ours, it has become possible to make purchases in any volume: in a single copy or in a batch with fast delivery throughout Russia!

Flexible system payment will allow you to immediately pay for the order + delivery costs online and save on transferring cash on delivery to the bank account of our store! We will deliver your order by Russian Post or Transport Company to the pick-up point or by courier to the Door in the shortest possible time.

Save

More details on Elhow: https://elhow.ru/ucheba/russkij-jazyk/orfografija/pravopisanie-glagolov/sekonomit-ili-sekonomit?utm_source=users&utm_medium=ct&utm_campaign=ct

Previously, our audience was not so large, but today we have expanded our boundaries of cooperation and offer products from the best manufacturers to a wide range of customers. And, it doesn’t matter where you live, you can order the BA3528FP microcircuit from any city in our country with the possibility of delivery to any, even the most remote point.

Currently, there is fierce competition on cost and speed of delivery of orders - we strongly recommend that you choose delivery by a Transport Company. because Although its delivery cost is not significantly higher than that of Russian Post (about 15-20%), but the speed of work completion and the absence of queues, as well as a loyal attitude towards the client, are disproportionately higher! :))

There is no doubt about the quality of the offered product. Microcircuit BA3528FP from famous manufacturer. BA3528FP meets all high quality standards, is factory certified and is therefore in high demand among many of our customers. One category of consumers uses the BA3528FP microcircuit for personal purposes, others for the purpose of running and developing a business.

For each product, we offer detailed characteristics, parameters and instructions for use, so you can choose the lot that is suitable and necessary for you. Microcircuit BA3528FP model BA3528FP. The presented model takes into account the demand and wishes of customers, takes into account the demand for the product on the market, and constantly updates the lineup goods.

You can find the BA3528FP microcircuit in the corresponding subcategory - Radio components / Import microcircuits / BA, using a convenient electronic search. We care about all customers and try to ensure that each client is satisfied with the product, quality of service, favorable delivery conditions, consultation, and cost. Our plans are to help everyone and everyone, and therefore we offer products only from a trusted manufacturer.

We will carefully pack the BA3528FP chip into your order and deliver it as quickly as possible, which is especially important for buyers who need it very urgently. We would like to draw your attention to the fact that the prices for the BA3528FP microcircuit model BA3528FP in our online store are the most optimal and affordable. The need for such products arises as needed. You can postpone the purchase of the BA3528FP microcircuit until later, or you can place an order right now, while the price of the product remains the same - extremely low and profitable. It is always pleasant to make purchases at low prices, especially when the order concerns more than one item of goods - this allows you to profitably save not only money, but also precious time!

radio-sale.ru

Technical characteristics of SMD 3528 Datasheet in Russian

I will continue publishing articles about technical specifications the most popular LEDs. Today, according to my plan, I will talk about the “old” SMD 3528, or rather about their characteristics. I note that the lighting properties of any diode are constantly improving. Therefore there may be some discrepancies. Plus, each manufacturer can add something to the detriment of another characteristic. But this is not critical, because... the majority adheres to a single “nomenclature”. Each manufacturer has its own Datasheet, but the main characteristics remain virtually unchanged.

At the dawn of its appearance, SMD 3528 were widely used in almost all lighting sources. Starting from indicator devices and ending with lighting lamps. And if they looked even more or less tolerable on indicator devices, then LED bulbs left much to be desired. There was little light from them (compared to current technologies). I once wrote that 3528 are beginning to outlive their usefulness. Most manufacturers are abandoning them in lighting lamps, the automotive industry, etc. The process of “leaving” the market is quite long and while these types of diodes can be found in decorative lighting, decorative light bulbs, indicator devices, and of course there is no escape from LED strips. It is thanks to the tapes used in backlights, due to their tolerable glow and virtually absent heating, that SMD 3528 continue to “catch on” to the rapidly developing LED market.

Main characteristics of LED SMD 3528

The LED is available with one crystal. As a result, we get one color: either all shades of white, or colored diodes - red, green, blue, yellow.

The lens used in production is transparent. The chip is based on InGaN. Typically, the lens consists of a silicone compound. The material of the housing is similar to SMD 5050.

If we compare the luminous flux with 5050, then in the diodes we are discussing today it is almost three times less and is only 4.5-5 Lumens. Previously, this was a revolutionary value, but now, looking at these data, I want to smile. And smile in a good way. After all, 3528 did its job and gave rise to the emergence of three-crystal diodes. Therefore, I will not judge them harshly)

I will consider Datasheet from Chinese manufacturer, with which our company constantly works and so far has no complaints about it. At one time they worked only in wholesale quantities, but recently they have expanded to retail. Or rather small wholesale. The minimum order quantity is 200 pieces. Their price is lower than that of Russian sellers, and the quality remains at the same level. We have already produced more than one thousand light sources from LEDs from this company. And... well, they have free delivery to Russia. For those who still don’t believe that China is quietly producing decent products, it’s worth talking to my colleague Konstantin Ogorodnikov, who will tell you why there are holes in bread. He looked through more than one Chinese supplier for us until he found the ones we needed)

Characteristics of white SMD 3528

Optoelectronic data of white diodes

Graphs and dependencies of previously considered white LED SMDs

Cool white SMD 3528

Characteristics of SMD 3528 cool white glow

Warm White SMD 3528

Characteristics charts of warm white SMD 3528

Since only chips with a white glow are the most common, I will omit the Datasheet 3528 SMD with a different color. Yes, it’s not necessary. Something tells me that it’s unlikely that anyone will be interested in these types of diodes. Well, if suddenly... Then you will find all the data at the link that you provided earlier. True, you will have to do the translation yourself. The manufacturer provides Datasheet in Chinese. But by comparing my pictures with symbols and Chinese “waste paper” you will easily understand everything and be able to create technical specifications yourself with your own translation.

Dimensions of SMD 3528

Any LED from the SMD series has a four-digit designation. Based on them, we can immediately obtain information about the sizes of the chips. the first two are length, the second are width. Dimensions are indicated in mm. Different manufacturers have their own errors, but they do not go beyond +-0.1-0.15 mm.

Diodes are produced in 2000 pieces per cassette (roll). If you are constantly engaged in “handicrafts”, then it is more profitable to order by rolls. And more convenient and practical. Especially if you have lamps with these diodes at home and you constantly have to solder them.)

And finally, some cautions when working with any SMD diodes.

This is not my whim or my experience. This is a real warning from the manufacturers!

The vast majority of diodes are coated with silicone compound. Despite the fact that he is less susceptible to mechanical stress, it must be handled carefully:

Do not touch the phosphor or silicone with your fingers. To do this you need to use tweezers. In general, it is better to avoid any contact with human sweat and fat deposits. It will give you peace of mind and the diode will last longer.
Do not touch the phosphor with sharp objects, even if carefully. In any case, you leave small “burrs” that will negatively affect the performance of the device in the future.
To avoid damage to chips already mounted on the board, do not stack them. Each board must have its own place so that they do not come into contact with another batch.

Well, that’s basically all the simple rules that everyone should follow. And with this I finish the story about the characteristics of LEDs of the SMD 3528 type and retire to compiling another material that is more interesting to me. Well, I don’t like to write about obvious things, much less characteristics that every self-respecting person who went to school should be able to read))).

Video on installation of SMD LEDs

leds-test.ru

If previously the elemental base of system power supplies did not raise any questions - they used standard microcircuits, now we are faced with a situation where individual power supply developers are starting to produce their own elemental base, which has no direct analogues among general-purpose parts. One example of this approach is the FSP3528 chip, which is used in a fairly large number of system power supplies produced under the FSP brand.

The FSP3528 chip was encountered in subsequent models of system power supplies:

FSP ATX-300GTF-

FSP A300F–C-

FSP ATX-350PNR-

FSP ATX-300PNR-

FSP ATX-400PNR-

FSP ATX-450PNR-

ComponentPro ATX-300GU.

Fig.1 Pinout of the FSP3528 chip

But since the production of microcircuits makes sense only in mass quantities, you need to be prepared for the fact that it can also be found in other models of FSP power supplies. We have not yet come across direct analogues of this microcircuit, therefore, in the event of its failure, a replacement must be made with exactly the same microcircuit. But it is not possible to purchase the FSP3528 in a retail distribution network, therefore it can only be found in FSP system power supplies, rejected for any other reason.

Fig. 2 Multifunctional circuit of the FSP3528 PWM controller

The FSP3528 chip is available in a 20-pin DIP package (Fig. 1). The purpose of the contacts of the microcircuit is described in Table 1, and Fig. 2 shows its multifunctional circuit. In Table 1, for each pin of the microcircuit, the voltage that should be on the contact during a typical switching on of the microcircuit is indicated. A typical application of the FSP3528 chip is its implementation as part of a computer power supply control submodule. This submodule will be discussed in the same article, but a little lower.

Table 1. Purpose of contacts of the FSP3528 PWM controller

Description

Supply voltage +5V.

Error amplifier output. Inside the chip, the contact is connected to the non-inverting input of the PWM comparator. A voltage is generated at this pin, which is the difference between the input voltages of the error amplifier E/A+ and E/A - (pin 3 and pin 4). During normal operation of the microcircuit, the voltage at the contact is about 2.4V.

Inverting input of error amplifier. Inside the chip, this input is shifted by 1.25V. The reference voltage of 1.25V is generated by an internal source. During normal operation of the microcircuit, a voltage of 1.23V should be present at the contact.

Non-inverting error amplifier input. This input can be used to monitor the output voltages of the power supply, i.e. this contact can be considered a feedback signal input. In real circuits, a feedback signal is supplied to this contact, obtained by summing all the output voltages of the power supply (+3.3V/+5V/+12V). During normal operation of the microcircuit, a voltage of 1.24V should be present at the contact.

ON/OFF signal delay control contact (control signal for turning on the power supply). A timing capacitor is connected to this pin. If the capacitor has a capacitance of 0.1 µF, then the turn-on delay (Ton) is about 8 ms (during this period of time the capacitor is charged to a level of 1.8 V), and the turn-off delay (Toff) is about 24 ms (during this period of time the voltage across the capacitor when it is discharged it is reduced to 0.6V). During normal operation of the microcircuit, a voltage of about +5V should be present at this contact.

Power supply on/off signal input. In the specification for ATX power supply connectors, this signal is designated as PS-ON. The REM signal is a TTL signal and is compared by an internal comparator to a 1.4V reference level. If the REM signal drops below 1.4V, the PWM chip starts up and the power supply starts working. If the REM signal is set to the highest level (more than 1.4V), then the microcircuit is turned off, and accordingly the power supply is turned off. The voltage at this pin can reach a maximum value of 5.25 V, although the typical value is 4.6 V. During operation, a voltage of about 0.2V should be observed at this contact.

Frequency setting resistor of the internal oscillator. During operation, there is a voltage at the contact of about 1.25V.

Frequency-setting capacitor of the internal oscillator. During operation, a sawtooth voltage should be observed at the contact.

Overvoltage sensor input. The signal from this pin is compared by an internal comparator with an internal reference voltage. This input can be used to control the supply voltage of the microcircuit, to control its reference voltage, and also to organize any other protection. In typical use, a voltage of approximately 2.5V should be present at this pin during normal operation of the microcircuit.

PG (Power Good) signal generation delay control contact. A timing capacitor is connected to this pin. A 2.2 µF capacitor provides a time delay of 250 ms. The reference voltages for this timing capacitor are 1.8V (when charging) and 0.6V (when discharging). That is, when the power supply is turned on, the PG signal is set to the highest level at the moment when the voltage on this timing capacitor reaches 1.8V. And when the power supply is turned off, the PG signal is set to a low level at the moment when the capacitor is discharged to a level of 0.6V. The typical voltage at this pin is +5V.

Power Good signal – power supply is normal. The highest signal level means that all output voltages of the power supply correspond to the nominal values, and the power supply is operating in normal mode. A low signal level means a faulty power supply. The state of this signal when regular work The power supply is +5V.

High precision voltage reference with less than ±2% tolerance. A typical value for this reference voltage is 3.5 V.

Overvoltage protection signal in the +3.3 V channel. Voltage is supplied to the input directly from the +3.3V channel.

Overvoltage protection signal in the +5 V channel. Voltage is supplied to the input directly from the +5V channel.

Overvoltage protection signal in the +12 V channel. The input is supplied with voltage from the +12V channel through a resistive divider. As a result of using a divider, a voltage of approximately 4.2V is established on this contact (provided that the voltage in the 12V channel is +12.5V)

Input for additional overvoltage protection signal. This input can be used to organize protection via some other voltage channel. In practical circuits, this contact is used, in most cases, to protect against short circuits in the -5V and -12V channels. In practical circuits, a voltage of about 0.35V is set at this contact. When the voltage rises to 1.25V, the protection is triggered and the microcircuit is blocked.

Input for adjusting the “dead” time (the time when the output pulses of the microcircuit are inactive - see Fig. 3). The non-inverting input of the internal dead time comparator is shifted by 0.12 V by the internal source. This allows you to set a small value of the “measure” time for the output pulses. The “dead” time of the output pulses is adjusted by applying a constant voltage from 0 to 3.3V to the DTC input. The higher the voltage, the shorter the operating cycle and the longer the dead time. This contact is often used to create a “soft” start when the power supply is turned on. In practical circuits, a voltage of approximately 0.18V is set at this pin.

Collector of the second output transistor. After starting the microcircuit, pulses are formed on this contact, which follow in antiphase to the pulses on contact C1.

Collector of the first output transistor. After starting the microcircuit, pulses are formed on this contact, which follow in antiphase to the pulses on contact C2.

Fig. 3 Main characteristics of pulses

The FSP3528 chip is a PWM controller designed specifically to control the push-pull pulse converter of a computer system power supply. The features of this microcircuit are:

Availability of integrated overvoltage protection in channels +3.3V/+5V/+12V-

Availability of integrated overload protection (short circuit) in channels +3.3V/+5V/+12V-

The presence of a multi-purpose entrance for organizing any kind of protection -

Supports the function of turning on the power supply by input signal PS_ON-

The presence of an integrated circuit with hysteresis for generating the PowerGood signal (power supply is normal) -

Availability of a built-in precision reference voltage source with a permissible deviation of 2%.

In those power supply models that were listed at the very beginning of the article, the FSP3528 chip is located on the power supply control submodule board. This submodule is located on the secondary side of the power supply and represents integrated circuit, placed vertically, i.e. perpendicular to the main board of the power supply (Fig. 4).

Fig.4 Power supply with FSP3528 module

This submodule contains not only the FSP3528 microcircuit, but also some elements of its “piping” that ensure the functioning of the microcircuit (see Fig. 5).

Fig.5 FSP3528 submodule

The control submodule board has a double-sided installation. On the back side of the board there are surface-mounted elements - SMD, which, by the way, give the most problems due to the not very high soldering properties. The submodule has 17 contacts arranged in one row. The purpose of these contacts is presented in Table 2.

Table 2. Purpose of contacts of the FSPЗ3528-20D-17P submodule

Purpose of contact

Output rectangular pulses designed to control power transistors of the power supply

Power Supply Start Input (PS_ON)

Channel voltage control input +3.3V

Channel voltage control input +5V

Channel voltage control input +12V

Small circuit protection input signal

Not used

Power Good Signal Output

AZ431 Regulator Reference Voltage Input

AZ431 voltage regulator cathode

Not used

Supply voltage VCC

On the control submodule board, in addition to the FSP3528 chip, there are two more controlled stabilizers AZ431 (analogous to TL431) which are in no way connected with the FSP3528 PWM controller itself, and are designed to control circuits located on the main board of the power supply.

As an example of the practical implementation of the FSP3528 microcircuit, Fig. 6 shows a diagram of the FSP3528-20D-17P submodule. This control submodule is used in FSP ATX-400PNF power supplies. It is worth noting that instead of diode D5, a jumper is installed on the board. This sometimes confuses some professionals who try to install a diode into a circuit. Installing a diode in place of the jumper does not change the functionality of the circuit - it should work both with a diode and without a diode. But installing a D5 diode can reduce the sensitivity of the protection circuit against small short circuits.

Fig.6 Diagram of the FSP3528-20D-17P submodule

Such submodules are practically the only example of the implementation of the FSP3528 microcircuit, therefore a malfunction of submodule parts is often mistaken for a malfunction of the microcircuit itself. In addition, it often happens that specialists are unable to identify the cause of the malfunction, as a result of which a malfunction of the microcircuit is implied, and the power supply is put aside in the “far corner” or is generally written off.

In fact, failure of a microcircuit is a rather rare occurrence. Submodule elements are even more susceptible to failures, and, first, semiconductor elements (diodes and transistors).

Today, the main defects of the submodule can be considered:

Failure of transistors Q1 and Q2-

Failure of capacitor C1, which may be accompanied by its “swelling” -

Failure of diodes D3 and D4 (immediately or separately).

Failure of other parts is unlikely, but in any case, if you suspect a malfunction of the submodule, you must first check the soldering of the SMD components on the printed circuit side of the board.

Chip diagnostics

Diagnostics of the FSP3528 controller is no different from diagnostics of all other modern PWM controllers for system power supplies, which we have covered more than once on the pages of our magazine. But nevertheless, again, in general terms, we will tell you how you can make sure that the submodule is working properly.

To check, you need to disconnect the power supply with the submodule being diagnosed from the network, and apply all the necessary voltages to its outputs (+5V, +3.3V, +12V, -5V, -12V, +5V_SB). This can be done using jumpers from another, working, system power supply. Depending on the power supply circuit, you may also need to supply a separate +5V supply voltage to pin 1 of the submodule. This can be done using a jumper between pin 1 of the submodule and the +5V line.

With all this, a sawtooth voltage should appear on the CT contact (pin 8), and a constant voltage of +3.5V should appear on the VREF contact (pin 12).

Next, you need to short-circuit the PS-ON signal to ground. This is done by shorting to ground either the contact of the output connector of the power supply (usually the greenish wire), or pin 3 of the submodule itself. With all this, rectangular pulses should appear at the output of the submodule (pin 1 and pin 2) and at the output of the FSP3528 microcircuit (pin 19 and pin 20), followed in antiphase.

The absence of pulses indicates a malfunction of the submodule or microcircuit.

We would like to note that when using similar diagnostic methods, you need to carefully consider the circuit design of the power supply, because the testing methodology may change somewhat, depending on the configuration of the feedback circuits and protection circuits against emergency operation of the power supply.

alunekst.ru

BA3528AFP/BA3529AFP CHIPS

BA3528AFP/BA3529AFP CHIPS MADE BY ROHM

BA3528AFP/BA3529AFP microcircuits from ROHM are designed for use in stereo players. They operate on a 3V supply and include a two-channel preamplifier, a two-channel power amplifier, and a motor controller. An on-chip reference voltage source eliminates the need for decoupling capacitors when connecting an audio head and headphones. The motor controller uses a bridge circuit to minimize the number of external components, which improves reliability and reduces the size of the device. Brief electrical characteristics of the BA3528AFP/BA3529AFP microcircuits are given in Table 1. Typical scheme inclusions are shown in Fig. 1. The input signal from the playback head goes to the non-inverting inputs of the preamplifiers (pins

Fig.1. Typical switching circuit for m/s BA3528AFP/BA3529AFP

Table 1. Main parameters of m/s BA3528AFP/BA3529AFP

19, 23), and the common wire of the head is connected to the reference voltage source (pin 22). The negative feedback signal is supplied from the outputs of the preamplifiers (pins 17, 25) through the correcting RC circuits to the inverting inputs (pins 19, 24). Boosted signal can be supplied to volume controls via electronic keys (pins 16, 26). The keys are closed if the microcircuit supply voltage is applied to the control input (pin 1). For the BA3529AFP chip, it is possible to enable Dolby noise suppressors in the output circuits of the preamplifiers. After level adjustment sound signal goes to the output power amplifiers (pins 15, 27) with a fixed gain. Its value is a classification parameter and is 36 dB for BA3528AFP and 27 dB for BA3529AFP. From the outputs of power amplifiers (pins 2, 12), the signal is supplied to headphones with a resistance of 16-32 Ohms, the common wire of which is connected to a powerful reference voltage source (pin 11). The main factor that reduces the reliability of a microcircuit and leads to its failure is a violation of its power parameters. The manufacturer limits the power dissipated by the microcircuit to 1.7 W at a temperature no higher than 25 "C, with this value decreasing by 13.6 mW for each degree of temperature rise. A complete replacement for the BA3528AFP/BA3529AFP microcircuits are the BA3528FP/BA3529FP microcircuits.

nakolene.narod.ru

If earlier the element base of system power supplies did not raise any questions - they used standard microcircuits, today we are faced with a situation where individual power supply developers are beginning to produce their own element base, which has no direct analogues among general-purpose elements. One example of this approach is the FSP3528 chip, which is used in a fairly large number of system power supplies manufactured under the FSP brand.

The FSP3528 chip was found in the following models of system power supplies:

- FSP ATX-300GTF;

- FSP A300F–C;

- FSP ATX-350PNR;

- FSP ATX-300PNR;

- FSP ATX-400PNR;

- FSP ATX-450PNR;

- ComponentPro ATX-300GU.

Fig.1 Pinout of the FSP3528 chip

But since the production of microcircuits makes sense only in mass quantities, you need to be prepared for the fact that it can also be found in other models of FSP power supplies. We have not yet encountered direct analogues of this microcircuit, so if it fails, it must be replaced with exactly the same microcircuit. However, it is not possible to purchase the FSP3528 in a retail distribution network, so it can only be found in FSP system power supplies that have been rejected for some other reason.

Fig. 2 Functional diagram of the FSP3528 PWM controller

The FSP3528 chip is available in a 20-pin DIP package (Fig. 1). The purpose of the microcircuit contacts is described in Table 1, and Fig. 2 shows its functional diagram. Table 1 shows for each pin of the microcircuit the voltage that should be on the contact when the microcircuit is turned on in a typical manner. A typical application of the FSP3528 chip is its use as part of a submodule for controlling the power supply of a personal computer. This submodule will be discussed in the same article, but a little lower.

Table 1. Pin assignments of the FSP3528 PWM controller

№	Signal	I/O	Description
		Entrance	Supply voltage +5V.
	COMP	Exit	Error amplifier output. Inside the chip, the pin is connected to the non-inverting input of the PWM comparator. A voltage is generated at this pin, which is the difference between the input voltages of the error amplifier E/A+ and E/A - (pin. 3 and pin. 4). During normal operation of the microcircuit, a voltage of about 2.4V is present at the contact.
	E/A-	Entrance	Inverting input of error amplifier. Inside the chip, this input is biased by 1.25V. The reference voltage of 1.25V is generated by an internal source. During normal operation of the microcircuit, a voltage of 1.23V should be present at the contact.
	E/A+	Entrance	Non-inverting error amplifier input. This input can be used to monitor the output voltages of the power supply, i.e. This pin can be considered a feedback signal input. In real circuits, a feedback signal is supplied to this contact, obtained by summing all the output voltages of the power supply (+3.3 V /+5 V /+12 V ). During normal operation of the microcircuit, a voltage of 1.24V should be present at the contact.
	TREM		Signal delay control contact ON/OFF (control signal for turning on the power supply). A timing capacitor is connected to this pin. If the capacitor has a capacity of 0.1 µF, then the turn-on delay ( Ton ) is about 8 ms (during this time the capacitor is charged to a level of 1.8V), and the turn-off delay ( Toff ) is about 24 ms (during this time, the voltage on the capacitor when it is discharged decreases to 0.6V). During normal operation of the microcircuit, a voltage of about +5V should be present at this contact.
		Entrance	Power supply on/off signal input. In the specification for power supply connectors ATX this signal is designated as PS - ON. REM signal is a signal TTL and is compared by an internal comparator with a reference level of 1.4V. If the signal R.E.M. becomes below 1.4V, the PWM chip starts up and the power supply starts working. If the signal R.E.M. is set to a high level (more than 1.4V), the microcircuit is turned off, and accordingly the power supply is turned off. The voltage at this pin can reach a maximum value of 5.25 V, although the typical value is 4.6 V. During operation, a voltage of about 0.2V should be observed at this contact.
			Frequency setting resistor of the internal oscillator. During operation, a voltage of about 1.25V is present at the contact.
			Frequency-setting capacitor of the internal oscillator. During operation, a sawtooth voltage should be observed at the contact.
		Entrance	Overvoltage detector input. The signal from this pin is compared by an internal comparator with an internal reference voltage. This input can be used to control the supply voltage of the microcircuit, to control its reference voltage, as well as to organize any other protection. In typical use, a voltage of approximately 2.5V should be present at this pin during normal operation of the microcircuit.
			Signal Delay Control Contact PG (Power Good) ). A timing capacitor is connected to this pin. A 2.2 µF capacitor provides a time delay of 250 ms. The reference voltages for this timing capacitor are 1.8V (when charging) and 0.6V (when discharging). Those. when the power supply is turned on, a signal PG is set to a high level at the moment when the voltage on this timing capacitor reaches 1.8V. And when the power supply is turned off, the signal PG is set to a low level at the moment when the capacitor is discharged to a level of 0.6V. The typical voltage at this pin is +5V.
		Exit	Power Good Signal - nutrition is normal. A high signal level means that all output voltages of the power supply correspond to the nominal values, and the power supply is operating normally. A low signal level indicates a faulty power supply. The state of this signal during normal operation of the power supply is +5V.
	VREF	Exit	High precision voltage reference with ±2% tolerance. A typical value for this reference voltage is 3.5 V.
	V 3.3	Entrance	Overvoltage protection signal in the +3.3 V channel. Voltage is supplied to the input directly from the +3.3 channel V.
		Entrance	Overvoltage protection signal in channel +5 V. Voltage is supplied to the input directly from channel +5 V.
	V 12	Entrance	Overvoltage protection signal in channel +12 V. Voltage from channel +12 is applied to the input V through a resistive divider. As a result of using a divider, a voltage of approximately 4.2V is established on this contact (provided that there are 12 in channel V voltage is +12.5V)
		Entrance	Input for additional overvoltage protection signal. This input can be used to organize protection via some other voltage channel. In practical circuits, this contact is used most often to protect against short circuits in channels -5 V and -12 V . In practical circuits, a voltage of about 0.35V is set at this contact. When the voltage rises to 1.25V, the protection is triggered and the microcircuit is blocked.
			"Earth"
		Entrance	Input for adjusting the “dead” time (the time when the output pulses of the microcircuit are inactive - see Fig. 3). The non-inverting input of the internal dead time comparator is biased by 0.12 V by the internal source. This allows you to set the minimum value of the “measure” time for output pulses. The “dead” time of the output pulses is adjusted by applying to the input DTC constant voltage ranging from 0 to 3.3V. The higher the voltage, the shorter the operating cycle and the longer the “dead” time. This contact is often used to create a “soft” start when the power supply is turned on. In practical circuits, a voltage of approximately 0.18V is set at this pin.
		Exit	Collector of the second output transistor. After starting the microcircuit, pulses are formed on this contact, which follow in antiphase to the pulses on contact C1.
		Exit	Collector of the first output transistor. After starting the microcircuit, pulses are formed on this contact, which follow in antiphase to the pulses on contact C2.

Fig.3 Basic parameters of pulses

The FSP3528 chip is a PWM controller designed specifically to control the push-pull pulse converter of the system power supply of a personal computer. The features of this microcircuit are:

- presence of built-in protection against excess voltage in channels +3.3V/+5V/+12V;

- presence of built-in protection against overload (short circuit) in channels +3.3V/+5V/+12V;

- the presence of a multi-purpose entrance for organizing any protection;

- support for the function of turning on the power supply using the PS_ON input signal;

- the presence of a built-in circuit with hysteresis for generating the PowerGood signal (power supply is normal);

- presence of a built-in precision reference voltage source with a permissible deviation of 2%.

In those power supply models that were listed at the very beginning of the article, the FSP3528 chip is located on the power supply control submodule board. This submodule is located on the secondary side of the power supply and is a printed circuit board placed vertically, i.e. perpendicular to the main board of the power supply (Fig. 4).

Fig.4 Power supply with FSP3528 module

This submodule contains not only the FSP3528 chip, but also some elements of its “piping” that ensure the functioning of the chip (see Fig. 5).

Fig.5 FSP3528 submodule

Table 2. Assignment of contacts of the FSPЗ3528-20D-17P submodule

№	Contact assignment
	Output rectangular pulses designed to control power transistors of the power supply

	Power supply start input signal ( PS_ON)

	Channel voltage control input +3.3 V
	Channel voltage control input +5 V
	Channel voltage control input +12 V
	Short circuit protection input
	Not used
	Power Good Signal Output
	Voltage regulator cathode AZ431
	AZ 431
	Regulator reference voltage input AZ 431
	Voltage regulator cathode AZ431
	Earth
	Not used
	Supply voltage VCC

Fig.6 Diagram of the FSP3528-20D-17P submodule

In fact, failure of a microcircuit is quite rare. Submodule elements are much more susceptible to failures, and, first of all, semiconductor elements (diodes and transistors).

Today, the main malfunctions of the submodule can be considered:

- failure of transistors Q1 and Q2;

- failure of capacitor C1, which may be accompanied by its “swelling”;

- failure of diodes D3 and D4 (simultaneously or separately).

Chip diagnostics

At the same time, on contact C.T.(cont. 8) a sawtooth voltage should appear, and on the contact VREF(pin 12) a constant voltage should appear +3.5V.

The absence of pulses indicates a malfunction of the submodule or microcircuit.

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