SCR AC voltage regulator circuit

SCR is a new type of semiconductor device. It has the advantages of small size, light weight, high efficiency, long life, fast action and easy use. Currently, AC voltage regulators mostly use SCR voltage regulators. Here we introduce a thyristor AC voltage regulator with a simple circuit, easy installation, and convenient control. It can be used as a voltage regulating device for household appliances to control lighting, fan speed, and iron temperature. This voltage regulator has an output power of 100W and can be used by general household appliances. 1: Circuit principle: The circuit diagram is as follows. The 　　 　　thyristor AC voltage regulator consists of two parts: a controllable rectifier circuit and a trigger circuit. The original circuit diagram is shown in the figure below. It can be seen from the figure that the diodes D1-D4 form a bridge rectifier circuit, and the double-base diode T1 forms a relaxation oscillator as a synchronous trigger circuit for the silicon controlled thyristor. When the voltage regulator is connected to the mains, the 220V alternating current is rectified by the diodes D1-D4 through the load resistor RL, forming a pulsating DC voltage at the A and K ends of the thyristor SCR. This voltage is stepped down by the resistor R1 and serves as a trigger circuit. DC power supply. During the positive half cycle of the alternating current, the rectified voltage charges the capacitor C through R4 and W1. When the charging voltage Uc reaches the peak voltage Up of the T1 tube, the T1 tube changes from off to on, so the capacitor C is rapidly discharged through the e, b1 junctions of the T1 tube and R2, resulting in a sharp pulse on R2. This pulse is sent to the control electrode of the thyristor SCR as a control signal, causing the thyristor to conduct. The tube voltage drop after the thyristor is turned on is very low, generally less than 1V, so the relaxation oscillator stops working. When the alternating current passes through the zero point, the thyristor switches off automatically. When the alternating current is in the negative half cycle, the capacitor C is recharged...and so on, the power on the load RL can be adjusted. 2: Component selection. The adjusting potentiometer of the voltage regulator is a WH114-1 synthetic carbon film potentiometer with a resistance of 470KΩ. This potentiometer can be directly welded on the circuit board. The resistor except R1 should be made of metal with a power of 1W. In addition to the film resistors, the others all use carbon film resistors with a power of 1/8W. D1-D4 use silicon rectifier diodes with reverse breakdown voltage greater than 300V and maximum rectification current greater than 0.3A, such as 2CZ21B, 2CZ83E, 2DP3B, etc. SCR uses silicon controlled rectifier devices with forward and reverse voltages greater than 300V and rated average current greater than 1A, such as the domestic 3CT series.