The heyday of optical storage media, such as CDs and DVDs, was bright, but short-lived. Today, after wear or damage, DVD players are no longer repaired, but thrown away or, at best, disassembled into parts. Inexpensive DVD players usually contain a 6...20 W switching power supply as a separate module, which, after a little modification, can be successfully used to power other devices.

One of the components of the VVK DV31851 DVD player is its SKY-P00807 power supply. which is recyclable. It has three output channels (+5 V, + 12 V. -12 V) with a total power of about 14 W. Based on this unit shown on the website, it was possible to produce a charger for various mobile multimedia devices. According to the author, it has significantly better parameters, including reliability, than the numerous ones that come with cell phones, tablet computers, and e-books. MP3 players, navigators and other modern “toys”.

The first stage of refinement of the SKY-P00807 unit was the installation of an interference suppression filter at its network input, assembled according to the circuit shown in Fig. 1. Fuse link F601 was moved from the printed circuit board of the unit to a holder installed on the device body. The previously missing power switch SA1 was also installed on the body. The remaining filter elements were placed on the printed circuit board of the unit.

Now the mains voltage -230 V through the closed contacts of the switch and the fuse-link, as well as through the resistors R1 and R2 that reduce the starting current, is supplied to the LC filter C1L1C2. After the filter, it goes to the network input of the unit. Varistor RU1 protects the device from overvoltages in the supply network.

The installation of limiting resistors made it possible to replace the fuse-link with a current of 1 A with a similar one with a current of 0.25 A. These resistors also reduced the likelihood of damage to the power supply by pulsed network noise. For the same purpose, a high-voltage ceramic capacitor was removed from the block, which connected the common wires of the primary and secondary circuits of the voltage converter. The two-winding inductor L1 is industrially manufactured; any similar small-sized inductor with a winding inductance of at least 1 mH and a total resistance of no more than 40 Ohms is suitable. The higher the inductance. all the better.

During the modification process, a swollen oxide smoothing capacitor of the +5 V voltage rectifier was discovered in the unit. This capacitor with a capacity of 470 μF was replaced with an oxide capacitor with a capacity of 1500 μF. parallel to which a ceramic capacitor with a capacity of 10 μF was soldered. To increase the output voltage from +5 V to 5.6 V in parallel with a 10 kΩ resistor. connected between pins 1 and 2 of the TL431 parallel voltage stabilizer microcircuit in the block, a resistor with a resistance of 43 kOhm was connected.

The integrated circuit TNY275PN pulse voltage converter previously worked with a heat sink only in the form of a section of foil on the board. To facilitate the temperature regime of this microcircuit, an additional heat sink was soldered to its heat sink pins 5-8 - a copper plate with a cooling surface area of ​​3 cm.

Capacitor C601 (Fig. 1) was replaced with a capacitor of the same capacity, but with an operating voltage of 450 V instead of 400 V. This was done in order to move it away from the heating TNY275PN microcircuit due to the long leads of the new capacitor.

During experiments with the power supply, it was found that if the load was connected only to the +5 V output (+5.6 V after modification), the voltage between the plates of the smoothing capacitors of the +12 V and -12 V output voltage rectifiers exceeded 20 V. Since the mentioned outputs of the modified unit The diodes of these rectifiers, designated on its board as D610 and D611, are not used. were dismantled.

If the high-frequency rectifier diodes in the power supply being modified turn out to be faulty, then they can be replaced with diodes from the KD247, UF400x series that correspond to the permissible reverse voltage. They can also replace diodes 1 N4007. A faulty optocoupler EL817 is replaced with any four-pin one with the numbers 817 in the name, for example. LTV817 or PC817. Instead of the TL431 chip, an AZ431 or LM431 in a TO-92 package is suitable.

Filter capacitors C1 and C2 are film or ceramic, capable of operating at an alternating voltage with a frequency of 50 Hz and at least 250 V. Their capacity can be in the range of 4700... 10000 pf. Additionally, oxide capacitors installed in the block are K53-19. K53-30 or imported analogs of capacitors K50-35 and K50-68. Disk varistor RU1 - TVR10471, which can be replaced by MYG14-471, MYG20-471, FNR-14K471, FNR-20K471 or GNR20D471K. Give preference to a varistor in a larger diameter housing.

A voltage of +6.6 V from the output of the power supply was applied to an additionally manufactured module, the circuit of which is shown in Fig. 2 Three loads with a total current consumption of up to 2 A can be simultaneously connected to its XP1, XS1 and XS2 connectors. The output voltage is about +6 V. When a load is connected to the XS1 socket, the germanium transistor VT1 opens by a voltage drop across the resistor R3 and turns on the HL2 LED. Under room lighting, its glow becomes noticeable already at a load current of 10 mA. The node on transistor VT2 and LED HL3 works in a similar way when the load is connected to the XS2 socket. Schottky diodes VD3 and VD6 limit the voltage drop across resistors R3 and R8 as the load current increases, thereby protecting the emitter junctions of transistors VT1 and VT2.

The XP1 connector is a splitter. equipped with different types of plugs. When a load is connected to it, LEDs HL2 and HL3 will light up simultaneously. Some mobile devices, after charging their built-in batteries, “forget” to close the corresponding electronic key. As a result, the battery voltage is supplied to the external power socket, which can lead to one mobile device with a discharged battery consuming energy from the charged battery of another. To prevent this situation, the power supply outputs are isolated by Schottky diodes VD2. VD4, VD5, VD7.

The limiting diode (suppressor) VD1 protects loads connected to the connectors from damage by high voltage in the event of a power supply failure. The HL1 LED lights up when the device is connected to the network. Filter C1L1L2C3C4 reduces the level of ripple in the output voltage of a switching power supply. Their swing at connectors XP1, XS1 and XS2 does not exceed 10 mV at a load current of 2 A. This is significantly less than that of various ones, where ripples can reach hundreds of millivolts.

Details of the device according to the diagram in Fig. 2 are installed on a mounting plate measuring 75x25 mm. Installation - double-sided hinged. Resistors R5 and R10 are soldered directly to the contacts of sockets XS1 and XS2. LEDs HL2 and HL3 are installed near these sockets. Chokes L1, L2 are industrially manufactured on H-shaped magnetic cores; the higher their inductance and the lower the resistance of the windings, the better. Germanium transistors SFT352 can be replaced with domestic ones from the MP25, MP26, MP39-MP42 series. The diodes included in the MBRD620CT assemblies are connected in parallel to improve reliability, reduce heat, and reduce voltage drop. When selecting diodes to replace them, give preference to powerful low-voltage Schottky diodes. Suitable, for example. MBRD630CT. MBRF835. MBRD320. MBRD330, 1N5820, 1N5821. The P6KE6.8A limiting diodes can be replaced with 1N5342 zener diodes. LEDs can be of any type for general continuous lighting applications, for example, the KIPD40, L-1053, L-173 series.

The device is assembled in a plastic case with dimensions of 172x72x37 mm. The location of its components inside the housing is shown in Fig. 3. Weight of the structure - 240 g without power cords. The manufactured power supply at a network voltage of 230 V consumes a current of 1.5 mA in idle mode and about 26 mA with a load current of 1 A. This was a pleasant surprise. that even without shielding a switching power supply, the described device does not have a noticeable negative effect on the quality of reception of broadcast radio stations of all bands, even if the radio receiver is standing nearby. After all, ordinary telephone chargers often completely jam radio reception with their interference, even on the VHF bands.

In addition to various digital mobile multimedia devices, “four-battery” cameras and video cameras designed for 4.8…6.4 V power supply, radios, and children’s toys can be connected to this power source. Other switching power supplies can be modified and used in a similar way. dismantled from faulty or unnecessary household electronic appliances, for example, the GL001A1 unit. In some cases, modification can be simplified, since many units already have a two-winding inductor at the network input.

In any electronic device, switching power supplies (UPS) occupy one of the leading places in terms of the number of failures. DVD players are no exception, where UPS malfunctions are not much less common than contamination of laser heads. The UPS circuit described in the article is used in at least ten models of DVD players from Samsung Electronics Co., such as: DVD-511, DVD-611, DVD-611B, DVD-615, DVD-711, DVD-718, DVD-811, DVD-812, DVD-818, DVD-818J, DVD-819, etc.

The above models of DVD players produced for Europe and the CIS countries use a flyback switching power supply with PWM, which is designed to operate from a 50/60 Hz AC mains voltage of 85...265 V without additional switching (Free Voltage). The electrical power consumption of the UPS from the network is 17.18 W. A simplified functional diagram of this block is shown in Fig. 1.

Rice. 1. Simplified functional diagram of UPS for DVD players

Rice. 2. Functional diagram of the STR-G6551 PWM controller chip

The alternating mains voltage is supplied to the bridge rectifier through a noise filter. The rectified voltage is smoothed by a filter and, through the primary winding of the pulse transformer, goes to the drain of the field-effect transistor - the output switch of the PWM controller PICF1 (STR-G6551). To protect the output switch transistor from breakdown by self-induction EMF pulses, a damper is used. To group stabilize the output voltages of the UPS, the STR-G6551 PWM controller receives an error voltage from the control circuit, which is formed from the secondary voltage of +5.8 V.

Description of some UPS elements

The basis of this power supply is a PICF1 PWM controller type STR-G6551.

Table 1. Pin assignments of the STR-G6551 chip

Its functional diagram is shown in Fig. 2, and the assignment of the conclusions is in table. 1.

The STR-G6551 chip contains:

startup circuit (START);

internal voltage stabilizer;

thermal and overvoltage protection circuits;

OR element and trigger - “latch” of the protection circuit;

pulse generator;

pre-output stage (driver);

output switch based on a high-voltage MOS transistor with a damping diode;

comparator pulse-width modulator and overcurrent protection circuit (Comp);

OR element of the PWM control circuit.

The UPS feedback circuit uses a PICS2 type 431 chip (according to the specification, a KA431Z chip from SAMSUNG is used). This chip is often called a “regulated (programmable) zener diode” or a programmable shunt voltage reference. A simplified functional diagram of the microcircuit is shown in Fig. 3.

Rice. 3. Simplified functional diagram of the KA431Z adjustable zener diode

A similar circuit using discrete elements is usually called a comparison circuit or an “error amplifier”. From Fig. Figure 3 shows that the KA431Z contains a 2.5V reference, a comparator, and an open-collector drive transistor. A reference voltage of 2.5 V is supplied to the comparator inputs and, through an external divider, part of one of the secondary positive voltages of the UPS (to pin R). The comparator compares these voltages and, through a transistor, the UPS control unit also controls the output voltages of both pulsed and linear power supplies. The location and purpose of the pins of the KA431Z microcircuit in the TO92 package is shown in Fig. 4.

Rice. 4. Location and purpose of pins (TO-92 housing)

The UPS also uses an opto-pair PICS1 (PC123), an uncontrolled stabilizer -8 V PICS3 type 7908 and controlled stabilizers +8 V PICS4 type 78R08 and +3.3 V PICS5 type PQ3RF23. The so-called digital transistors are used as a series of switches in the block (KSR1101 and KSR1103 - n-p-n structures, KSR2101 - p-n-p structures), each of which, in addition to the transistor itself, contains a resistive base bias divider.

Schematic diagram of the UPS

The schematic diagram of the UPS is shown in Fig. 5.

Rice. 5. Schematic diagram of the UPS

Note. The diagram in this figure uses somewhat unusual designations for positional part numbers.

They all start with the Latin letter P (short for Power), which indicates that the part belongs to the power supply.

There are three or four letters in total in the part designation. The second letter of three or the second and third of four indicate the type of part: D - diode, Q - transistor, R - resistor, C - capacitor, E - oxide (electrolytic) capacitor, F - fuse, L - inductance (choke), B - inductance (choke) in the form of a ferrite tube placed on a jumper or part output (CORE-FERRITE BEAD), T - transformer, V - varistor, Z - zener diode, IC - microcircuit, CN - connector.

The last third or fourth letter indicates the part belonging to a particular chain. Thus, the letter F denotes parts of primary circuits, and the letter S denotes parts of secondary circuits, etc. The position number of any part (except for the varistor PVA1 and the pulse transformer PTD1) contains five characters. So, a part number with four letters ends with one number, and with three letters it ends with two numbers. For example: PICS3 or PEF12. Let's consider the operation of the UPS according to the diagram in Fig. 5. A network rectifier with an interference protection circuit is quite simple and does not require any special explanation. It is assembled using PDS01-PDS04 diodes. Varistor PVA1 protects the UPS and the entire device from overload when the mains voltage increases significantly. The voltage of 290...310 V (for a 220 V AC network) obtained using a mains rectifier is smoothed out by a PEF10 capacitor and is used to power the UPS converter. Resistor PRF10 limits the charging current of capacitor PEF10, thereby protecting the rectifier bridge diodes from overload when turned on. When the DVD player is connected to the network, the trigger circuit capacitor PEF12 is charged from the network through noise suppression filters, the PDF01 diode and the trigger circuit resistors PRF11, PRF12, PRF13, PRF14. When the voltage on this capacitor and on the pin. 4 microcircuits reaches 16 V, the triggering circuit is turned on and the voltage from the PEF12 capacitor is supplied through this circuit to power the main components of the STR-G6551 microcircuit. In this case, the first positive pulse arrives at the gate of the MOS transistor of the microcircuit, opening this transistor. Since the transistor is loaded onto the primary winding (1-3) of the pulse transformer PTD1, the resistance of which is inductive, the drain current of this transistor will increase. Flowing through the resistor PRF20 (current sensor), the current creates an increasing (sawtooth) voltage drop across it, which is applied to the pin through PRF19. 5 chips STR-G6551, where it adds up with constant voltages supplied there through PRF15 and optocoupler PICS1. When the current of the MOS transistor of the microcircuit increases so much that the voltage at the pin. 5 exceeds a certain limit (1.45 V), the comparator of the microcircuit will issue a command to turn off this transistor, and it will close before the next pulse arrives. The turn-off moment of the MOS transistor depends both on its drain current and on the degree of opening of the phototransistor of the PICS1 optocoupler. The duration and duty cycle of the pulses in transformer PTD1 also depend on this.

Pulses from pin. 4 PTD1 transformers, through the PDF13 diode and the PRF16 resistor, recharge the storage capacitor PEF12, providing the necessary power to the microcircuit and phototransistor of the PICS1 PC123 optocoupler in steady state (operating or standby).

If the circuit is faulty or overloaded, then the pulses on the pin. 4 PTD1 are missing or have insufficient swing to recharge the PEF12 capacitor. The capacitor will discharge and charge again, and the circuit will go into cyclic operation.

To protect the output MOS transistor of the microcircuit from voltage overload, the range of reverse pulses on the primary winding of transformer PTD1 is limited by the circuit PCF11 PFD12 PBD11 PDS11 PRS11 PRS12.

Now let’s look at how group stabilization of UPS output voltages is carried out. Let's assume these voltages increase. The voltage at the input of the PICS2 stabilization stage will also increase, its output current, and therefore the current through the IR optocoupler diode will increase, which will lead to a decrease in the resistance of the optocoupler phototransistor and a decrease in the DC voltage at the pin. 5 chips STR-G6551. In this case, to turn off the output transistor of the microcircuit, a slightly larger value of the sawtooth voltage from the PRF20 current sensor will be required, which means that the MOS transistor will be open longer. This will lead to a decrease in the duty cycle of the pulses at the output of the microcircuit and in the pulse transformer, and to a decrease in the output voltages of the UPS to the previous value. Similarly, but exactly the opposite, the process occurs in the case of a decrease in the output voltages at the output of the converter.

The purpose and features of the elements of secondary UPS sources are given in table. 2.

Table 2. UPS Secondary Power Supplies

Rectifiers	Stabilizers	Purpose	Application
PDS31	PICS1 (7908)	–8 V source	Power supply for AUDIO and VIDEO nodes
PDS32	-	Source +10…+12 V	Auxiliary source for receiving commuting stress
	PICS4 (78R08)	+8 V source	Power supply for AUDIO and VIDEO nodes
PDS33	-	+5.8 V source	Used to power the cascade stabilization, IR diode optocouplers (in the stabilizing OOS circuit) and to get all days off voltage 5 V
	On transistor PQS57	+5 V source	Power supply for the analogue part of AUDIO, VIDEO and other nodes
	On transistor PQS58	+5 V source	Power supply for the digital part AUDIO, VIDEO and other nodes
	No additional stabilization	+5 V source	Power supply to the main components of the device (via PDS52 isolation diode and integral fuse PIC56 N20)
PDS34	PICS5 (PQ3RF23)	+3.3 V source	Power supply for digital part controllers
PDD35	-	Source –28 V	Power supply for fluorescent indicator
PDS36	-	Fluorescent filament voltage source indicator

Let's look at some additional features of the UPS circuit.

To obtain a stabilized voltage of +8 V, a PICS4 chip (78R08) is used, which has a PWR CTL control input (pin 4). This pin is connected through a resistor PRS56 to the cathode of the PDS52 diode (+5 V source). This is done so that if there is no + 5 V voltage, the + 8 V voltage will also be turned off.

Another feature of the circuit is the presence of an external SAVE signal. This signal directly controls the switch on the PQL57 transistor. In standby or operating modes, the transistor is open at the log level. “1”, which leads to the opening of the associated output voltage control switches on transistors PQL58 (+ 8 V per AUDIO node), PQL56, PQL55 (-8 V per AUDIO node), PQL51, PQL52 (fluorescent indicator filament voltage) and PQL53 , PQL54 (luminescent indicator supply voltage). If the SAVE signal is low (logical "0"), then the PQL57 transistor and all associated switches will close. This will turn off the listed voltages.

And finally, the last feature. The standby mode of the UPS differs from the operating mode in the absence of a voltage of +3.3 V and two voltages of + 5 V to power the analog and digital parts of the entire device. The device is switched from one mode to another using the ON/OFF signal (log. "1" - on, logic "0" - off). This signal to control the supply of +3.3 V voltage is supplied to the PWR CTL control input (pin 4) of the PICS5 chip (PQ3RF23). The + 5 V voltage stabilizers are controlled using switches on digital transistors PQS56 and PQS55. Level log. "1" in operating mode opens the transistor PQS56, which ensures the opening of the transistor PQS55. Through this transistor, voltage is supplied to the parametric stabilizer on the PZS51 zener diode and the PDS51 diode, connected to the base circuits of the PQS57 and PQS58 transistors, providing two +5 V voltages at the emitters of these transistors.

The device does not turn on. The mains fuse has blown

If the mains fuse has blown, you should not replace it and immediately plug the device into the network. Check the protective varistor for an open circuit, and check the bridge diodes and the output transistor of the PWM controller chip for a short circuit. A broken varistor indicates that there was an overload in the supply voltage. The PEF10 anti-aliasing filter capacitor and the noise protection filter capacitors break through somewhat less frequently. It should be remembered that with this defect, the PRF20 current sensor and the PRF10 limiting resistor may burn out.

The output transistor of the STR-G6551 chip usually fails for the following reasons:

The network voltage is too high;

The optocoupler PICS1 is faulty;

The PICS2 stabilization cascade is faulty.

The device does not turn on. Mains fuse is intact

The power supply may not start for the following main reasons:

There is no +300 V voltage on the capacitor of the smoothing filter PEF10;

Current sensor PRF20 is broken;

Parts of the starting circuit are broken: diode PDF01 or PRF11, PRF12, PRF13, PRF14;

Loss of capacitance or leakage of the PEF12 capacitor;

Short circuit in the circuits of secondary power supplies;

PWM controller chip is faulty.

The device spontaneously switches from operating mode to standby mode

A similar effect can occur due to short circuits in the secondary circuits of the power supply, at the command of the control processor, or when the PEF12 capacity is reduced.

Defects appear in the device due to the lack of certain voltages at the output of the UPS

If one or more output voltages from the power supply are missing, you should check the switches, stabilizers and rectifiers. All these circuits are discussed in sufficient detail in the article.

All radio amateurs at some point begin to regret that they understand electronics. Summer, heat, vacation... But even here, broken household appliances make themselves felt and spoil the long-awaited vacation. And now, just as I was getting ready to go to the river, a friend brought his old one and with a pitiful face asked: “Can you fix it?”

There was nothing to do - we had to save the device, and curiosity kicked in, but what was the problem (you understand what I mean), so I made myself comfortable and heated up a one-kilogram Soviet soldering iron with a hundred watts (alas, there was no more convenient soldering iron in the whole village).

After half an hour, the soldering iron warmed up like an oven. The player itself showed no signs of life. After opening it, it turned out that a fuse had blown, an electrolyte had blown after the diode bridge at the power input, and another electrolyte had blown on the 12 Volt bus, already at the power supply output.

Since the components were tight, the fuse was wrapped in foil and put in place. The electrolyte on the 12 Volt bus with a capacity of 1000 µF was replaced with 470 µF, and the capacitor was found in the power supply from the SEGA console.

The first electrolyte - on the rectifier, turned out to be fully functional, only for some reason it was swollen and was not replaced.

After turning on, the player worked like new, but after examining the power supply board, it became clear that the unit was not working normally - an incomprehensible overheating of the diode bridge, some limiters and even capacitors. I left the player turned on for an hour - the heat generation turned out to be stable, who knows, maybe initially it all got terribly hot, but it works very well. Sincerely - AKA KASYAN