5L0165R power adapter circuit and troubleshooting

The travel charging power adapter uses a switching power supply and a 4-pin (DIP-8 package) monolithic integrated block 5L0165R, which has the characteristics of simple circuit and small size. Its rated input is 100~240V/300mA, and its output is 5.3V//600mA. See attached diagram for circuit

1. PWM controls   the 220V mains power to obtain a 300V DC voltage through the fuse resistor and BD1 bridge rectifier, C1, L1, C2, and C11 filtering. One channel supplies power to the switching transformer T, and the other channel provides starting power to IC1 ③ pin through R2. IC1 contains PWM pulse width modulation, switching tube and control circuit. Its power output terminal ① and pins ⑥, ⑦ and ⑧ are connected in parallel to the primary of the switching transformer. Pin ④ is the output voltage sampling terminal and pin ② is the ground terminal. When working, pins ① and ⑥, ⑦, and ⑧ output PwM pulses. The transformer's III winding induces a high-frequency voltage that is rectified by R3 and D6 and filtered by C3 to provide working power for IC1 pin ③. The high-frequency voltage induced by the II winding of the transformer is rectified by D5 and filtered by C8 and C9 and then output to provide power for the charging circuit. The photocoupler IC2 (PC817) cooperates with the voltage stabilizing tube ZD2 to complete the voltage stabilization adjustment control, and at the same time isolate the hot bottom (ground) plate from the cold bottom (ground) plate to ensure user safety.

2. Voltage stabilization control   Voltage stabilization tube ZD2, IC2 and resistors R4 and R5 together form a voltage reference source for voltage stabilization and constant current power supply control. The voltage stabilization adjustment control process is: when the output voltage +5.3V ↑ (or ↓) → the leakage of the voltage stabilizing tube zD2 ↑ (or ↓) → the luminous intensity of the light-emitting diodes at the pins ① and ② of IC2 ↑ (or ↓) → IC3 ③, The internal resistance of the phototransistor at pin ④ is ↓ (or ↑) → the current at pin ④ of IC1 is ↑ (or ↓) → the switch conduction time in IC1 is ↓ (or ↑) → +5.3V ↓ (or ↑). According to the component value in the figure, it is a stable 5.3V. In this way, when the output voltage of 5.3V changes, this change is fed back to the ④ pin of IC1 by the optocoupler, thereby controlling the stability of the output voltage. If you want to change the output voltage, you can replace the voltage regulator tube with a different voltage stabilization value or adjust the resistance of resistor R4. Increase the resistance of R4 to increase the output voltage. Otherwise, reduce the output voltage.

3. Overcurrent protection   R7 and R8 are overcurrent sampling resistors. Under normal circumstances, Q1 does not conduct. If overcurrent occurs (>600mA), the voltage at both ends of R7 and R8 will be greater than 0.6V, so Q1 is saturated and conducts, and the light The potential of pin ② of coupling IC2 becomes low, the voltage of pin ④ of IC1 drops to the minimum, the current reaches the maximum, the switch is turned off, the protection operates, and the main output is blocked.