Introduction

A small passive DC adjustable constant current (CC) electronic load with temperature-controlled fan to test the constant voltage DC power supply.

Features and parameters:

Passive design

Input voltage: 5 ~ 18V

Constant current: 0 ~ 3A adjustable (set the maximum value through R8, use R1 to adjust the constant current value)

Maximum design power: 25W, measured power: 10W without fan mode, 35W with fan mode

Precautions:

When using USB interface as input, the current should not exceed 1.5A

The fan is recommended to use a low-power model, otherwise it may be difficult or impossible to start.

The two LDOs supplying power to the fan can be selectively welded to one or two groups according to the actual power consumption of the fan.

The temperature control fan starts at about 65 degrees Celsius, be careful of burns! The starting temperature can be fine-tuned by changing the value of R10.

It is strictly prohibited to reverse the power supply, otherwise it will cause irreversible damage.

The heat sink is connected to the ground. Be careful not to touch other electrodes when using it.

When the input voltage is less than 6V, due to the LDO voltage drop, the fan cannot start normally. The power should be reduced.

The power tube can be any type of TO-220 Darlington transistor, as long as it is NPN, but it should pay attention to the upper limit of the voltage resistance and maximum power of the transistor.