| 摘要 |
PURPOSE:To reduce the power loss, by connecting the gate turn off thyristor GTO between the load and the full wave rectifying circuit and providing the zero cross circuit triggered near zero voltage of AC. CONSTITUTION:In case of AC load operation, when the switch 11 is closed, the transistor Tr7 is OFF and the zero cross circuit consisting of Tr8, and resistors 18, 19 is activated. The zero cross circuit constitutes the AND circuit together with the photo coupler 8 and GTO4 is not activated unitl 1 level. When the input signal a reaches 1 level at time t0, the voltage VAk between the anode and cathode is e1, Tr8 is ON and Tr6 is OFF. The power supply voltage is zero at time t1, Tr8 is OFF and Tr6 is ON, the capacitor 9 is charged, gate current flows to GTO4, and GTO4 turns on near the power supply phase zero voltage. In this case, since the base current of Tr8 is small and the trigger time of GTO is small, the power loss at the resistor 18 is small. The switch 11 is open with DC power supply. |
