The key part of any electronic device is the power supply. Any instability or malfunction of the power supply part causes the device to stop working or demonstrate weird behavior. In this article/video, I introduced an AC-to-DC flyback Switching power supply that converts 85V-260VAC to 5VDC-2.5A, which can be used in various applications. The 5V selection for the output makes it friendly for linear regulators that convert 5VDC to lower voltages.

The maximum power delivery of this power supply is around 12W, which means it can handle 2.5A at 5V output. The controller chip is DK1203, which does not need any external supply, a startup resistor, or an auxiliary winding on the transformer. The ferrite core of the transformer is EE20. A potentiometer allows you to adjust the output voltage and set it exactly at 5.0V.

To design the schematic and PCB, I used Altium Designer 23 and shared the PCB project with my friends for feedback and updates using Altium-365. The fast component search engine, Octopart, proved invaluable in quickly obtaining component information and generating the Bill of Materials (BOM). To ensure high-quality fabricated boards, I sent the Gerber files to PCBWay.

I tested the board for voltage drop, current delivery, and output noise. I used Siglent SDL1020X-E DC Load and Siglent SDS2102X Plus oscilloscope to perform all tests. I am confident that building this circuit enhances your knowledge regarding switching power supply design, except for using it for real applications.

Specifications

Input Voltage: 85-265VAC

Output Voltage: 5VDC

Maximum Output Current: 2.5A

Maximum Output Current (continuous): 2A

Output Noise (No load): 1.5mV(rms), 4mV(p-p)

Output Noise (Max Load, 2A): 3mV(rms), 25mV(p-p)

Maximum Voltage Drop (2A load): 50mV

Transformer Type: EE20