Introduction to 3 design methods of the circuit diagram of the DC stabilized power supply
(1) Transistor series DC voltage stabilizer circuit. The circuit block diagram is shown in Figure 1. In this circuit, the output voltage UO is sampled by the sampling circuit to obtain the sampling voltage, and the sampling voltage is compared with the reference voltage to obtain the error voltage. The error voltage adjusts the working state of the adjustment tube, so that the output The voltage changes, which is exactly opposite to the change of the output voltage caused by the change of the supply voltage UI, so as to ensure that the output voltage UO is a constant value (regulated value).
The simple series DC regulated power supply circuit is very simple, but after adding the auxiliary power supply, the circuit is more complicated, and the reliability of the circuit is difficult to guarantee due to the use of discrete components.
(2) Three-terminal integrated voltage regulator circuit is used. He uses a three-terminal integrated voltage stabilizer with adjustable output voltage and internal overload protection. The output voltage has a wide adjustment range. A voltage compensation circuit can be designed to continuously adjust the output voltage from 0 V.
(3) Adjustable DC regulated power supply made by single chip microcomputer. The circuit uses thyristor as the first-stage voltage regulating element, uses regulated power supply chips LM317 and LM337 as the second-stage voltage regulating element, and controls the relay through AT89CS51 to change the resistance value of the resistor network, thereby changing the peripheral parameters of the voltage regulating element , and add a soft-start circuit to obtain 0 ~ 24 V, 0.1 V step, the driving capacity can reach 1 A, and can display the power supply voltage value and output current value at the same time.
The hardware circuit mainly includes transformer, rectifier filter circuit, differential pressure control circuit, voltage stabilizer and output voltage control circuit, voltage and current sampling circuit, important data storage circuit before power failure, single chip microcomputer, keyboard display, etc. part, the schematic diagram of the hardware part is shown in Figure 3.
The function of the positive and negative terminal differential pressure control circuit is to reduce the differential pressure between the input terminal and the output terminal of LM317 and LM337 to reduce the power consumption of LM317 and LM337. The voltage-stabilizing circuit is composed of three-terminal voltage-stabilizing chip LM317 (LM337 for negative pressure) and peripheral devices, and the output voltage control circuit adopts a resistance network controlled by a relay.
The power supply has good stability and high precision, and can output an adjustable DC voltage within the range of ±24 V, and its performance is better than the traditional adjustable DC regulated power supply, but the circuit is more complicated and the cost is higher. Higher, used in occasions with higher requirements. In practice, if the requirements for the circuit are not too high (this is often the case), the second design scheme is mostly used.
