| 摘要 |
PURPOSE:To prevent destruction of switching elements, by switching an NPN transistor (TR) directly coupled between rectified power supplies through the turning on/off of a semiconductor switching element respectively connected to positive and negative power supply buses. CONSTITUTION:An AC power supply 1 is rectified at diodes 3-6 and an NPN TR10 is directly coupled between the power supplies. A positive or negative base current is supplied to the TR10 through the turning on/off of TRs 35, 38 connected between positive and negative power supply buses. Further, a non- linear element 12 is connected between the base and emitter of the TR10. Then, in case of a failure of a choke coil 8 such as short-circuit, only the TR10 is defected and the TRs 35, 38 of the driving circuit can be protected. |
