Power control circuit for MOSFET with source load - has frequency of pulse oscillator feeding boot strap driver reduced for higher widths

摘要

A circuit (4) including a bootstrap circuit purse width modulates the gate voltage of the MOSFET (1). An oscillator (5) with variable frequency produces a pulse sequence as output, and this is fed to the modulation circuit (4). The pulse frequency of the controllable oscillator is controlled in dependence on the pulsse width. The pulse frequency may be reduced with rise of pulse width. The pulse frequency may be hold constant until a set pulse width rise has taken place, and then be reduced. ADVANTAGE - Enables operation of MOSFET via bootstrap circuit up to virtually 100 per cent switch on time.