| 摘要 |
PURPOSE:To attain speedily switching by connecting the secondary coil of a current transformer inserted onto a bypass with polarity supplying a base reverse bias current across the base and emitter of a bipolar transistor. CONSTITUTION:A bias circuit conducted at the time of a power MOSFET 2 off is installed across the base of the 1st bipolar transistor 1 and the emitter of the 2nd bipolar transistor 3, and the current transformer 8 inserted into the bias circuit is connected with the polarity supplying a base reverse bias current across the base and emitter of the 2nd bipolar transistor 3. If the power MOSFET 2 is turned off, the collector current of the bipolar transistor 1 flows through a bypass circuit 11, and its some part turns out to be a reverse bias current IB2 supplied to the 2nd bipolar transistor 3 from the current transformer 8. Due to the existence of diodes 9 and 10, the reverse bias current IB2 never sneaks into the bypass circuit 11 from the current transformer 8. Thus a small- sized drive circuit can obtain a comparatively quick switching speed at less electric power. |
