Production of adjustable regulated power supply composed of TL431

The picture shows a regulated power supply circuit that uses TL431 as the voltage reference and an external field effect transistor K790 as the adjustment tube to form a continuously adjustable 2.5V ~ 30v, and the output current can reach 6A.

Working principle: As shown in the figure, the 220v voltage is stepped down by transformer B, rectified by D1~D4, and filtered by C1. In addition, D5, D6, C2, and C3 form a voltage doubler circuit (making Vdc=60V), RW and R3 form a voltage divider circuit, TL431 and R1 form a sampling amplifier circuit, 9013 and R2 form a current limiting protection circuit, and FET K790 is used for adjustment. tube (can be used directly in parallel) and C5 is the output filter circuit, etc. The voltage stabilization process is: when the output voltage decreases, the potential of point f decreases. The internal amplification of TL431 increases the voltage at point e. After adjustment by K790. The potential of point b increases; conversely, when the output voltage increases, the potential of point f increases and the potential of point e decreases. After adjustment by K790, the potential of point b decreases, thereby stabilizing the output voltage. When the output current is greater than 6A, the transistor 9013 is turned off, limiting the output current to within 6A, thereby achieving the purpose of current limiting.

The resistor R1 of this circuit is 2w, and the resistor R2 is 5w.