Design of high power adjustable voltage regulated power supply

introduction

Many electronic devices require a high-precision, high-current, regulated and adjustable DC power supply. This article introduces a general-purpose low-power regulated integrated circuit uA723, which, in combination with appropriate high-power tubes and other peripheral components, forms a high-power adjustable DC regulated power supply, whose maximum output current can reach tens of amperes.

uA723 mainly plays the role of voltage regulation and voltage stabilization in the circuit. Its internal structure is shown in Figure 1.

Figure 1 uA723 internal structure diagram

Figure 2 High-power adjustable voltage-regulated power supply circuit diagram

Figure 2 shows the schematic diagram of the high-power adjustable voltage-stabilized power supply circuit. Its working principle is explained as follows:

uA723 itself is a series adjustable voltage regulator; its features include controllable output voltage Vo=2～37V, output current Iom=0.15A, small output temperature drift, high ripple suppression ratio, short-circuit current limiting protection, etc. Similar to uA723 are LM723, HA17723, CW723, W723, etc. They have metal round shell Y-10 package and dual in-line C-14 package. Different packages have different pin functions, so please pay attention to distinguish them.

This circuit uses uA723 in C-14 package. A 6.2V voltage regulator and a voltage divider resistor are connected to the 8-pin Vref terminal to form a reference voltage circuit; the 4-pin is the inverting input terminal, also known as the sampling terminal. Changing the resistance of the external 10k potentiometer can change the output voltage value of the 10-pin. The voltage output value of the 10-pin determines the Veb potential value and conduction amount of the uA723 external expansion sampling tube VT5, thereby also controlling the output value of the four parallel high-power adjustment tubes VT1-VT4. C3 is an external vibration elimination capacitor, and Rsc is a short-circuit current limiting protection resistor, which can limit the output current of the uA723; the current limiting value ILM=Vse/Rsc (Vse-the voltage value across the current limiting resistor); capacitors C7 and C8 are bypass capacitors to improve AC noise, and R1 is a discharge resistor, which also plays a role in stabilizing the voltage.

Conclusion

The circuit has a simple structure, is easy to maintain, has a good voltage stabilization effect, and is almost unaffected by fluctuations in the AC voltage of the power supply network and the load current. As long as the quality of the device is guaranteed, it is usually not prone to failure. Once the uA723 is damaged, the output voltage may be high or there may be no output voltage. Simply replace it with a new uA723 and re-adjust the output to return to normal.