The non-contact automatic delay AC voltage regulator refers to the replacement of the relay by the bidirectional crystal wide tube. Compared with the contact of the relay, the circuit is simple, the thyristor has a long service life, and there is no contact failure or contact burnout. And the quality is cheap and easy to make. No contacts. The voltage adjustment is accurate and fast, and the universal range is wide: the AC input is 150V~280V. After the oscillation voltage regulator can output 220V voltage, including the output part of the delay circuit with bidirectional thyristor and relay control on and off.
First, the working principle of the circuit is shown in the figure. The circuit is composed of two parts: First, the full-bridge rectification of the mains through the L1 of B1 into VDI~VD4 is added to the conduction angle of the thyristors VS1 and VS1, and is controlled by the single junction transistor Tl. Tl, C1, Rl, R2, R3 and potentiometer WI form a relaxation oscillator. Changing the resistance value of W1 can change the oscillation period.
When the input voltage rises, the voltage applied to T1 rises accordingly, and the oscillation speeds up. The conduction angle of VS1 decreases, the voltage on L1 decreases, and the voltage on L2 decreases. The output voltage drops. Conversely, when the input minimum voltage drops to 150V, the voltage on L1 rises, and the voltage after L2 coupling also rises. This keeps the output voltage constant at around 220V, which is used for color TVs, washing machines, and refrigerators.
The second part is the delay part. The circuit is based on the 555 time base circuit. It consists of few external components and simple circuit. The input AC power is composed of C2+C2, VD6, VD7, C3 and VD8, which are composed of step-down, rectification, filtering and voltage regulator circuits. Get 12V smooth DC voltage for 555 time base circuit operation. When the AC power is turned on, the voltage across the capacitor C4 cannot be abruptly changed. 555 time base circuit 2, 6 feet for high power. 3 feet output low level. If the gate of the bidirectional thyristor vs has no trigger voltage, then vs is blocked, and the power supply loop is blocked, and the power supply is stopped. The power supply charges the capacitor C4 via the resistor R5, after a period of C4 is full of charge. When the 2 pin of the 555 time base circuit becomes a low level, the 3 pin outputs a high level, and the LED 1 is lit to the gate of the triac via the resistor R6, and the vs is turned on. K coil is energized Kl contact closed three eye socket to turn on the output power (Note: the delay circuit is dedicated to the refrigerator).
Second, the selection and requirements of electronic components
The operating current of the diode and unidirectional thyristor of VDl~VD4 and VS1 should be determined according to the capacity of Bl, and there must be a large margin, and the withstand voltage is above 600V. Please note when using VS1: He is a three-pole thyristor without a specified form. VD5 can be used with 1N4007. Transformer BI needs to be self-made. For example, the rated capacity is set to about 300W of the balance regulator. The core cross-sectional area of ​​B1 should be 18cm2, and L1 and L2 are each wrapped with a high-strength enameled wire of 0.51mm for 600åŒ. Wl is best to use a wirewound potentiometer above 3W. After connecting the circuit, adjust potentiometer W1 to make the output 220V. Any model can be used for the 555 time base circuit. The bidirectional thyristor VS2 should be 3A/600V type, such as 3CTS series. Relay K selected Yang JQC-3F model: working voltage is 220V. Medium power relay with contact current of 10A. A metal film resistor is used for R4, R5, R6, and R7. Cl selects the withstand voltage 630VCBB capacitor. VD6, VD7 select lN4007 rectifier diode, VD8 select 12V type Zener diode, such as 2CW14 or 2CW13. C4, c5 use ceramic capacitors.
Kl selects 10A ship type switch, UF selects 3A fuse; 10A two eye socket special color TV and washing machine; three eye socket specializes in refrigerator. V1 and V2 are AC input and output o~300V AC voltmeters respectively. To change the start delay time, adjust the parameters of R5 or C4. Its capacitance and resistance are subject to the icon. If it is not possible to adjust properly, check the line for faults or components. Under normal circumstances, as long as the welding is correct, it can work normally.
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