A DC high-power continuously adjustable voltage-stabilized power supply circuit design

Whether it is computer repair or electronic production, a regulated power supply is indispensable. The following introduces a regulated power supply with a DC voltage continuously adjustable from 3V to 15V, and a maximum current of 10A. The circuit uses the high-precision standard voltage source integrated circuit TL431 with temperature compensation characteristics to make the voltage regulation more accurate. If there are no special requirements, it can basically meet normal maintenance use. The circuit is shown in the figure below.

As shown in the figure, the circuit diagram of high-power adjustable voltage-stabilized power supply

Its working principle is divided into two parts. The first part is a fixed 5V1.5A voltage-stabilized power supply circuit. The second part is another high-precision and high-current voltage -stabilized circuit with continuous adjustment from 3 to 15V. The circuit of the first circuit is very simple. The DC voltage after rectification by the silicon bridge QL1 from the secondary 8V AC voltage of the transformer is filtered by the C1 electrolytic capacitor, and then the 5V three-terminal voltage regulator block LM7805 can generate a fixed 5V1A voltage-stabilized power supply at the output without any adjustment. This power supply can be used as an internal power supply when repairing the computer board. The second part is basically the same as the ordinary series voltage-stabilized power supply , but it uses the high-precision standard voltage source integrated circuit TL431 with temperature compensation characteristics, so the circuit is simplified, the cost is reduced, and the voltage-stabilizing performance is very high. In the figure, resistor R4, voltage regulator TL431, and potentiometer R3 form a continuously adjustable constant voltage source, which provides a reference voltage for the base of BG2. The voltage regulator value of the voltage regulator TL431 is continuously adjustable. This voltage regulator value determines the maximum output voltage of the voltage regulator . If you want to expand the adjustable voltage range, you can change the resistance values ​​of R4 and R3. Of course, the secondary voltage of the transformer should also be increased. The power of the transformer can be flexibly controlled according to the output current, and the secondary voltage is about 15V. The rectifier tube QL used for bridge rectification uses a 15-20A silicon bridge with a compact structure and a fixing screw in the middle. It can be directly fixed on the aluminum plate of the casing, which is conducive to heat dissipation. The adjustment tube uses a high-current NPN metal shell silicon tube. Because it generates a lot of heat, if the chassis allows, try to buy a large heat sink to expand the heat dissipation area. If you don’t need a large current, you can also use a silicon tube with a smaller power, so that it can be made smaller. Three 50V4700uF electrolytic capacitors C5 and C7 are used for filtering in parallel to make the large current output more stable. In addition, the capacitors should be relatively large. Those with smaller sizes and the same 50V4700uF mark should be avoided as much as possible. When the voltage fluctuates frequently or they are not used for a long time, they are prone to failure. Finally, let’s talk about the power transformer. If you don’t have the ability to wind it yourself or can’t buy a ready-made one, you can buy a ready-made switching power supply of more than 200W to replace the transformer. In this way, the voltage stabilization performance can be further improved, but the production cost is not much different. There are no special requirements for other electronic components. After installation, it can work normally without much adjustment.