Patent ID: 6246296
Filing Date: 2001-06-12
Classification: H02M,H03K

Abstract:
A pulse width modulator (PWM) with improved duty cycle during a cycle of operation, comprising:three pairs of power switching devices connected between upper and lower rails of a power source and providing a three-phase output, the upper of each paid of said power switching devices being connected to said upper rail and the lower of each pair of said power switching devices being connected to said lower rail;a bootstrap capacitor, for each of said three pairs of power switching devices, so connected thatsaid capacitor is charged when said lower switching device of a corresponding pair of power switching devices of said three pairs of power switching devices is conductive, andsaid capacitor is discharged to maintain said upper switching device of said corresponding pair of power switching devices in the conductive state when said lower switching device of said corresponding pair of power switching devices is in the nonconductive state; andmeans for controlling the charging of said capacitors so that charging takes place only on selected cycles of the operation when needed as a function of time.