Over-current protection for a switch mode class D audio amplifier

摘要

Circuits and methods for over-current protection of pulse-width modulation systems such as switch mode class D audio systems, DC-to-DC converters, or switch mode power supplies have been disclosed. Over-current protection has been achieved by introducing supply-scalable pulses to bring the modulation index of PWM pulses to a safe level. Additionally to the over-current protection a recovery circuit and method to be applied right after an over-current situation has been disclosed.

主权项

1. A method for detecting and solving an over-current situation of a pulse-width modulated system comprising the steps of:
(1) providing a pulse-width modulated system comprising a filter, means to detect an over-current situation, a PWM modulator, a pulse generator, means to multiplex output from pulse generator with output from PWM modulator; (2) starting normal operation of the pulse-width modulated system; (3) monitoring continuously data stream out of the PWM modulator in order to detect an over-current situation until the pulse modulated system is switched off; (4) checking if an over-current situation is detected and, if so, go to step (5), otherwise repeat step (4); (5) setting an over-current signal; (6) enabling the pulse generator generating pulses having a supply-scalable duty cycle; (7) multiplexing the output of the pulse generator with PWM modulator output; (8) bounding output current by suitable modulation caused by pulses from the pulse generator; (9) resetting over-current signal after over-current situation is solved; and (10) resuming normal operation of the pulse-width modulated system and go back to step (4).