Over-voltage protection circuit for a drive transistor

摘要

A drive transistor is connected to a resonant load in a low-side drive configuration. The voltage across the conduction terminals of the drive transistor is sensed and compared to an over-voltage threshold. An over-voltage signal is asserted in response to the comparison. The drive transistor is controlled by a PWM control signal in normal mode. In response to the assertion of the over-voltage signal, the drive transistor is forced to turn on (irrespective of the PWM control signal) to relieve the over-voltage condition. Operation of the circuit may be disabled or forced into soft start mode in response to the assertion of the over-voltage signal. Additionally, the pulse width of the PWM control signal may be reduced in response to the assertion of the over-voltage signal.

主权项

1. A circuit, comprising:
a drive transistor having a control terminal configured to receive a drive signal and having a first conduction terminal and a second conduction terminal, wherein said first conduction terminal is configured for connection to a load circuit; a sense circuit configured to sense a voltage across the first and second conduction terminals; a comparator circuit configured to compare the sensed voltage to voltage threshold and generate a signal indicative of an over-voltage condition; and drive circuitry configured to generate said drive signal in response to a pulse width modulation (PWM) signal, said drive circuit including a force on circuit actuated in response to said signal indicative of the over-voltage condition to force said drive transistor to turn on irrespective of the PWM signal.