High voltage integrated circuit driver for half-bridge circuit employing a jet to emulate a bootstrap diode

Claim 1

A circuit for driving a half-bridge formed by lower and upper power transistors connected between an output terminal and respective lower and upper rails of a high voltage DC supply, and for charging a bootstrap capacitor having first and second ends, the first end being connected to said output terminal, said circuit comprising: means for generating lower and upper drive command signals for commanding driving said respective lower and upper power transistors to non-contemporaneous conducting states; power supply means for generating at a power supply output a relatively low control voltage with respect to said lower rail; a lower drive module connected to the power supply output for being powered by said relatively low control voltage and comprising means for applying a lower drive control signal between a control electrode of the lower power transistor and the lower rail in response to said lower drive command signal; an upper drive module adapted to be connected to the first end of the bootstrap capacitor for being powered by a bootstrap voltage across said bootstrap capacitor and comprising means for applying an upper transistor control signal between a control electrode of the upper power transistor and the output terminal in response to said upper drive input control signal; and bootstrap diode emulator means for charging said bootstrap capacitor to said bootstrap voltage, said bootstrap diode emulator means comprising a JFET transistor having a source electrode coupled to said power supply output, a drain electrode adapted to be connected to the second end of the bootstrap capacitor, a gate electrode coupled to a further control signal derived from said lower drive command signal for driving said JFET transistor to a conducting state when the lower power transistor is driven to a conducting state.