((exclusive)): A20112 Power Supply Schematic

A very specific request!

Part 6: Modifying the A20112 Schematic for Custom Voltage

Because the A20112 uses a TL431 feedback network, you can modify the output voltage within 20% safely. a20112 power supply schematic

11. Troubleshooting Guide

• No output: check fuse, bridge, bulk cap voltage, controller Vcc/startup.
• Output low or unstable: inspect feedback network, TL431 reference, optocoupler, compensation.
• High ripple: check output caps ESR, diode conduction, switching node waveform.
• Overheating: check component sizing, airflow, shorted traces.
• EMI problems: add snubbers, relocate noisy traces, add common-mode choke.

4. Feedback Loop (Voltage Regulation)

• Components: Optocoupler (Opto-isolator) and a Shunt Regulator (like the TL431).
• Importance: This is crucial for stable voltage. If the output voltage drifts, the feedback circuit tells the input stage to adjust the duty cycle. A faulty optocoupler is a common cause of unstable voltages.

Conclusion

Components

5.2 Adding Current Limiting

Insert a low-value sense resistor on the output return path and use an op-amp to feed back into the optocoupler. Refer to the schematic’s primary-side current sensing as a model. A very specific request

Optocoupler: Sends a signal from the secondary side back to the primary controller while maintaining isolation. No output: check fuse, bridge, bulk cap voltage,

Part 7: FAQ – A20112 Power Supply Schematic

Q1: Is the A20112 power supply isolated?

Yes. The flyback transformer provides 3kV isolation between primary and secondary. The schematic clearly shows a physical gap between optocoupler pins and transformer windings.