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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Switching power supply on the STR-S6307 chip. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Телевидение Many switching power supplies of modern TVs are assembled on microcircuits, in particular, on the STR-S6307 and SE110N. However, their internal "stuffing" is often not shown on the circuit diagrams, which makes it difficult to repair such sources. The published article partially fills this gap. The reader will also find in it information about malfunctions, the nature of their manifestation, as well as ways to turn on domestic transformers in various imported TV models. The SANYO STR-S6307 chip is used in the power supplies of such TVs as AIWA: TV-1402, TV-2002, TV-2102; SONY: KV-1435, KV-1485MT, KV-2185MT, KV-RM827S, KV-14DK1, KV-21DK1, KV-RM827B; PANASONIC: TC-21L3RTE, TC-21E1RTE [1], etc. Meanwhile, the lack of descriptions of the very structure of the STRS6307 and SE110N microcircuits created many difficulties in repairing their power circuits. That is why it was necessary to comprehensively study and reveal the construction of these microcircuits. This task was solved by comparing the connection diagrams of STRS6307, STR-S5941 and STR-10006 [2]. To determine the structure of the SE110N, the SE014N chip [3] was taken as a basis. Continuity of STRS6307 and SE110N circuits, a series of electrical tests made it possible to determine the ratings of the elements included in them. To check the correctness of the disclosure of the structure and to determine the possibility of replacing damaged STR-S6307, SE110N microcircuits with their discrete equivalents, as well as the possibility of replacing faulty transformers 36-24409000A (AIWA), SRT (SONY), ET834K407A (PANASONIC) with domestic TPI-8-1 and TPI -5, a power source was assembled on domestic parts and a TPI-8-1 transformer. The device reliably operates under a load of 50...80 W both when assembled from attachments and when using STR-S6307 and SE110N microcircuits. Faults were introduced into the experimental power supply. A description of how the source responds to them is given at the end of the article. A schematic diagram of the AIWA-TV1402/2002/2102 TV power supply is shown in fig. 1 (network and secondary rectifier circuits simplified). Transistor KT847A (VT1 in the IC801 chip) can be replaced with KT872A, BU508A, BU2508A, 2SD1710, transistor 2SA817A (Q801) - with KT361B, transistor 2SC3852 (Q822) - with KT940A, diodes EG1Z and EU1Z (D803-D805) - on KD243D - KD243Zh. Zener diode D807 can serve as D814D.
The source works as follows. The voltage is about 300 V from the capacitor C811 after turning on the TV through the start circuit R803, R804, pin 3 of the IC801 microcircuit is fed to the base of the key transistor VT1 of this microcircuit. The transistor starts to turn on. Through it, the magnetization winding 7-5 of the transformer T803 and the resistor R805 (current sensor) flows a linearly increasing current. In the positive feedback winding (POS) 1-2 of the transformer, an EMF of mutual induction occurs and an increasing base current of the transistor VT1 flows from the output 1 of the transformer through the output 5 of the IC801 chip, the R5R4 divider, the emitter junctions of the transistors VT4 and VT1, the output 2 of IC801 to the output 2 of the transformer. Having reached a certain value, the voltage from resistor R805, applied through pins 2 and 7 of IC801 and resistor R1 to the emitter junction of transistor VT3, opens it. The PIC winding current is closed through the R5R4 divider, emitter junctions of transistors VT4 and VT2, transistor VT3 and resistors R3, R805. Transistor VT2 opens by shunting the emitter junction of transistor VT1 and closing it. The voltages on the windings change polarity. Their positive pulses recharge the filter capacitors of the secondary rectifiers. Then everything repeats. So there are several cycles of opening the key transistor VT1 through the start circuit. After that, the capacitors of the secondary rectifiers are charged almost to the nominal voltage and stop loading the transformer. As a result, the source goes into the self-oscillation mode. In the self-oscillation mode, when the key transistor VT1 is closed, there is a POS voltage on the winding 1-2 of the transformer (positive at pin 2). The capacitors are charged with the current of this winding: C815 - through pin 2 of the IC801 chip, diode VD1, pin 3 of IC801 and resistor R810; C814 - via pin 2 of IC801, diode VD2, pin 4 of IC801 and diode D803; C813 - through resistor R807, pin 9 of IC801, diode VD3 and pin 5 of IC801. When the charging currents of the capacitors of the secondary rectifiers decrease to zero, the voltage on the winding 1-2 of the transformer also becomes equal to zero. The voltage of the capacitor C815 through the resistor R810, winding 1-2 of the transformer and conclusions 2,3 IC801 affects the emitter junction of the transistor VT1 and opens it. The increasing current of the winding 7-5 of the transformer causes a voltage in its winding 1-2 to be positive at pin 1. Through pins 5 and 2 of IC801 and the divider R5R4, it is applied to the emitter junctions of transistors VT4 and VT1. On the elements VT4, R4, R5, VD2, C814, R808, D803, a unit for maintaining the base current of the transistor VT1 is assembled. The winding current 1-2 of the transformer, passing through the emitter junctions of transistors VT4, VT1, opens them. In this case, the capacitor C814 is discharged through them, creating the base current of the transistor VT1. Transistor VT1 is turned off by transistor VT2. It, in turn, is controlled by the current shutdown unit on the VT3, R805, R1, R3 elements and the output voltage stabilization unit on the Q801 transistor, IC802 optocoupler, IC821 chip, D804, D805 diodes and D807 zener diode. The executive part of the stabilization unit is shown in a simplified way in fig. 2. The collector voltage on the transistor Q801 is the sum of the voltages on the winding 1-2 of the transformer and the capacitor C813, charged through the diode VD3 and the resistor R807 with the closed transistor VT1. Elements R811 and C816 make up the lower arm of the Q801 base bias voltage divider. The upper arm is formed by resistor R814 and optocoupler phototransistor IC802. Through the LED of the optocoupler IC802 (see Fig. 1), the output current of the comparison node flows on the transistor VT1 of the IC821 microcircuit. The phototransistor of the optocoupler (see Fig. 2) reduces its resistance with an increase in the output voltage of 112 V. As a result, the emitter current of the Q801 transistor changes, which is part of the base current of the transistor VT2 (see Fig. 1). Transistor VT2 changes the moment of its opening and shunting of the emitter junction of the key transistor VT1.
The protective zener diode D807 is designed to increase the current of the Q801 transistor with a sharp increase in the amplitude of the pulses on the winding 1-2 of the transformer, for example, due to an open load. Diode D805 together with resistors R811, R4, R5 limits the amplitude of the pulses on the winding 1-2. Diode D804, together with resistor R811, serves to recharge capacitor C816 during the closed state of transistor VT1 through the collector junction of transistor VT2, the emitter junction of transistor Q801 and resistor R812. In case of failure of the T803 (AIWA), T601 (SONY) transformer, when it is impossible to get to the damaged winding, a TPI-8-1 pulse transformer can be installed in the power source. The diagram of its connection in the AIWA TV is shown in fig. 3. The voltage of +8,6 V to power the STANDBY +5 V source and the reset signal supply unit on the IC822 chip (ST3050R) is provided by additional elements VD1, C1, C2, DA1.
The simplest one can be called the scheme for connecting the TPI-8-1 transformer to a SONY TV. It uses only four transformer windings: a 19-1 magnetizing winding, a 3-5 POS winding, a 6-12 winding for a 115 V source, and a 16-20 winding for a 15 V source. TPI-801 is suitable for replacing the T5 transformer of a PANASONIC TV. Its connection diagram is shown in fig. 4.
Malfunctions encountered in the device can be divided into two groups: damage inside the IC801 and IC821 microcircuits and defects in attachments. Breaks in transistors VT2 and VT3 of the IC801 chip inevitably lead to a breakdown of the transistor VT1 and blown mains fuse. With a break in resistors R803, R804, the output voltages are zero. The same thing happens when the R810, C815 circuit is broken, winding 1-2 of the T803 transformer. In the event of a break or loss of capacitance of the capacitor C814, the output voltage of the 112 V source drops to 97 V. The same occurs when the resistor R808 breaks. An open diode D803 causes the source voltage to drop to 92 V, and the capacitor C816 to 32 V. On the contrary, a break or loss of capacitance of the capacitor C813 increases the source voltage to 160 V, a rather strong whistle is heard. In the event of a breakdown of the transistor Q801, the voltage of the 112 V source drops to 20 V and a screech is heard. When the emitter of the Q801 transistor, the elements of the IC802 optocoupler or the VT1 transistor in the IC821 chip breaks, the source voltage also rises to 160 V and a strong whistle is heard. Long-term operation with a broken automatic control loop, when the output voltage is 160 V, causes a breakdown of the VT1 transistor in the IC801 chip and the horizontal scanning output transistor. Literature
Author: I.Molchanov, Moscow
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