| 摘要 |
PURPOSE:To reduce the size and the cost of an inverter by switching the power source voltage level of a base current supplying circuit in response to the magnitude of a load, and regulating the supplying base current of a main circuit transistor, thereby alleviating the switching loss. CONSTITUTION:A base current supplying circuit for driving a transistor inverter couples a PWM signal ouput from a PWM signal generator 5 with the primary side of a photocoupler 5, controls to turn ON or OFF a transistor of the secondary side to control ON or OFF a transistor 19 of an inverter. A DC voltage is supplied to the supplying circuit from an AC power source 1 through a power source transformer 30 and a diode rectifier 3. In this case, high and low voltage taps 30H, 30L are provided at the primary side of the transformer 30, and switched by a tap changeover relay 31. Thus, a current sensor 32 is switched to a low voltage tap side when the output current of the inverter is the rated value or lower and to a high voltage tap side when it exceeds the rated value. |
