Simple electronic load

Simple electronic load, mainly used to test the charger.

The charger can be tested with a PD decoy device.

The simple PD decoy device https://oshwhub.com/47415Y/di-cheng-ben-jian-yi-PD-QCyou-pi
has a maximum power of 100W. It is ok for a short time, but the heat dissipation is not enough for a long time. 40W for a long time is no problem.
The load input voltage is 5-30V, pay attention to the capacitor voltage resistance, you can choose the load self-power supply or external power supply, use switch SW1 to switch, use external power supply (tpyec power supply on the right), the load can be as low as 1V.

The upper and lower potentiometers adjust the current independently. Each channel is about 3A max.

The fan and op amp are powered by HT7463, which is first stepped down to 5V and then stepped up to 12V using MT3608. The efficiency is average, but the cost is low and reliable.

The board is back and testing is complete. . . . . . OK

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Replenish:

1) Choose one of two sampling resistors, 2512 resistor or constantan wire for installation. The one chosen here is 0.1R 3W 2512 resistor.

2) The resistor on TL431 was originally chosen too small, but has been changed to 3K, and the schematic has been updated.

3) Adjust the potentiometer clockwise to the minimum, which may be different from common practice.

4) The power tube uses TO247 MOS tube, and the disassembled GP20B60 is used here.

5) The fan can be selected from 5V or 12V, selected through the two fuse resistors.

6) Happy New Year to everyone.

External USB powered.

load power supply.

Maximum power test.