Isolated gate drive circuit having a switched input capacitor

摘要

An improved gate drive circuit powered by a DC source voltage, the drive circuit having an isolated output stage with a parallel-connected by-pass capacitor and a switched input capacitor circuit that maintains a charge on the by-pass capacitor for driving the gate of a controlled MOS transistor while isolating the by-pass capacitor from the source voltage. In a fully isolated embodiment of the improved gate drive circuit, a bank of controlled switches alternately couples the input capacitor to the source voltage and the by-pass capacitor, while in another embodiment, uni-directional isolation is achieved by replacing one or more of the controlled switches with diodes.