Double relay 100 ~ 200W automatic voltage regulator circuit - Power Circuit - Circuit Diagram

Probe current voltage pin 420*4450 head diameter 5.0 over current and voltage pin

Photocoupler

When the grid voltage drops below 220V, the normally closed contact of J1 activates the transformer B to boost the voltage. The output remains under 220V, and J2 connects the transformer’s 5th pin. If the grid voltage exceeds 220V, J2 switches to the 4th pin of the transformer for voltage regulation.

When the grid voltage is higher than 220V, resistor R1 samples the voltage, triggering J1 to connect and allowing the transformer to step down the voltage. If the output goes beyond the set threshold, R4 samples the voltage and activates J2, which then closes the circuit on the transformer’s 4th pin to regulate the output.

Component selection is crucial for the regulator's performance. The power handling capability mainly depends on the cross-sectional area of the transformer core and the diameter of the enameled wire used. The iron core size is 19×(24–25), and the coil is wound with high-strength enameled wire ranging from 0.27 to 0.35 mm in diameter. The winding can be done without layering. The first and second windings have around 48 turns, while the second to third has approximately 822 turns. From the third to the fourth pin, use 0.41–0.51 mm enameled wire, and each of the fourth to fifth pins should have about 85 turns.

Transistors BG1 and BG3 are typically small-power 3DG type transistors, while BG2 and BG4 are PNP silicon medium-power transistors. There are no special requirements for resistors and capacitors; standard components can be used without any issues.

This design ensures stable voltage regulation under varying grid conditions. It is suitable for applications where consistent power supply is essential, such as in sensitive electronic equipment or industrial control systems. Proper component selection and careful assembly are key to achieving optimal performance and long-term reliability.