Over-voltage protection circuit for control electronics circuit utilized for driving motor of electric power tool, has switch switched when breakdown voltage is reached, and safety device that is triggered when switch is switched

摘要

The circuit (14) has a semiconductor switch (28) i.e. triac, whose power terminals (30, 32) are connected between terminals (12, 13) of a power supply. The switch is controlled by a diode (24) i.e. trisil(RTM: thyristor surge protection device) diode, at a control terminal (34) such that the switch is switched when breakdown voltage of the diode is reached. The breakdown voltage of the diode is 360 volts and rated current of the switch is 40 ampere. A releasable safety device (38) e.g. fuse and resettable safety device, is triggered when the switch is switched.