Adjustable regulated power supply with current limiting protection

Although we can use many integrated circuits to make various power circuits, under certain conditions, we can also consider using discrete components to build some power circuits that suit our needs. The circuit we introduce here can achieve continuous adjustment from 0.7V-24V, and can achieve an adjustable current limit of 50mA-2A. As an experimental power supply, it may be a good choice. The circuit is shown in the figure below.

Here are some production and debugging methods.

P1 is used to set the maximum output current limit. By adjusting it, a current limit of 50mA-2A can be given at the corresponding output voltage.

P2 is used for output voltage adjustment. It must be noted that a logarithmic potentiometer is required. This will improve the adjustability and linearity of the output voltage.

The output voltage and capacity of the power transformer should be selected according to the output voltage and current you need. The best solution is: the transformer secondary voltage is 36, 40, 48V or 50, 75, 80V with a middle tap. The capacity is 100VA.

Capacitor C1 can be selected from 2200-6800uF/35-50V. BC182 is a 50V/100mA/NPN transistor; BD139 is an 80V/1.5A/NPN transistor; BC212 is a 50V/100mA/PNP transistor; 2N3055 is a 60V/15A/NPN transistor.

Q4 must use a heat sink, and it can be replaced by TIP3055