A20112 Power Supply Schematic

The "A20112" identifier is most commonly associated with a 12V 10A (120W) switching power supply board  often found in DIY 3D printers, CCTV systems, and universal AC-to-DC converters . The "Story" of the A20112 Power Supply

AC Live --- Fuse --- EMI Choke --- Bridge Diode (+) --- Bulk Cap (+) --- Transformer Primary (Pin 1)
                                             |                        |
                                            GND                       MOSFET (Drain)
                                                                           |
                                                                      Source --- Current Sense Resistor --- GND Primary
                                                                           |
                                                                      PWM Controller (CS pin)

Adopts CRM for high efficiency and low switching noise via zero current switching. Interleaving Control: a20112 power supply schematic

(models E72525, E72535, M72625, etc.) and various 12V SMPS modules. Renesas Electronics Core Schematic Functions The "A20112" identifier is most commonly associated with

Q4: Why is there a small blue disc capacitor across the transformer primary?

That is a Y-capacitor (class Y2) for reducing EMI. It is part of the common-mode noise filter. Do not remove it – it’s essential for passing FCC/CE tests. Adopts CRM for high efficiency and low switching

4.3 Cold Solder Joints

  • Symptoms: The unit works intermittently; tapping the case causes power loss.
  • Analysis: Due to thermal cycling, the solder joints on the heavy transformer and the output connector pins often crack.
  • Solution: Reflow solder on the transformer pins, connector pins, and switching transistors.

Conclusion

The A20112 power supply schematic is more than just a wiring diagram—it is a roadmap to understanding the behavior, failure modes, and modification potential of a versatile 12V switching supply. By mastering the flyback topology and the specific component functions detailed above, you can diagnose faults down to the component level, rescue seemingly dead units, and even repurpose them for custom electronics projects.

High-efficiency design that allows for smaller coils and filters .