Semiconductor device which drives low-voltage driven switching device, using low-voltage direct current power source, a diode and a capacitor

摘要

A capacitor (C) and a Zener diode (ZD2) are connected in parallel to a high-voltage side drive circuit (2). when a Zener voltage (VZD2) is set 5V, a voltage which is charged up in the capacitor (C) is determined by the Zener voltage (VZD2). Hence, it is only necessarv to set a voltage (VCC) in a loxv-voltage d.c. power source (4) at a value which is higher than (VZD2+VD+VCE), where VD is a forward-direction voltage to a diode (Di) and VCE is an ON-voltage to a low-voltage side switching device (Q1). Since a variation in a charging voltage which is supplied to a high- voltage side drive circuit is suppressed, it is possible to drive a switching device with 5V.