Apparatus and method for deriving power for switching a switch from voltage across the switch

摘要

Apparatus and related method for deriving, from voltage across a power switch, power for a gate drive which opens and closes the power switch in response to a control signal includes a first voltage converter connected in parallel with the power switch and a series combination also connected in parallel with the power switch. The first voltage converter converts a high input voltage which appears across the power switch when the power switch is open to a low output voltage. The series combination includes a second voltage converter for receiving the low output voltage from the first voltage converter, converting it, and providing the converted voltage to the gate drive. The series combination also includes a high-voltage switch, connected in series with the second voltage converter, for opening and closing when the power switch is opened and closed by the gate drive in response to the control signal. The high-voltage switch provides to the second voltage converter a low input voltage which appears across the power switch when the power switch is closed, and the second voltage converter converts the low input voltage and provides the converted voltage to the gate drive.