Patent ID: 7773358
Filing Date: 2010-08-10
Classification: H03F

Abstract:
1. Power output circuitry for a digital audio system, comprising: PWM gate logic for receiving an audio channel pulse-width-modulated control signal; a power amplifier having an input coupled to receive the pulse-width-modulated control signal from the PWM gate logic and having an output for providing current for driving a load; a current sensing circuit, coupled to the output of the power amplifier, for sensing current driven from the power amplifier to the load; an overcurrent threshold detector, having an input coupled to the current sensing circuit and having an output, for comparing the sensed current to an overcurrent threshold; an overcurrent latch, having a set input coupled to the output of the overcurrent threshold detector, having a clear input coupled to the pulse-width-modulated control signal, and having an output coupled to the PWM gate logic, for generating a blocking signal to block the receipt of the pulse-width-modulated control signal by the power amplifier from the PWM gate logic responsive to the sensed current reaching the overcurrent threshold within a cycle of the pulse-width-modulated control signal, and for clearing the blocking signal for a next cycle of the pulse-width-modulated control signal; and overload protection circuitry, having an input coupled to the output of the overcurrent latch, for presenting an overload shutdown signal to the PWM gate logic, responsive to the frequency of cycles of the pulse-width-modulated control signal in which the sensed current reaches the overcurrent threshold, wherein the overload protection circuitry presents the overload shutdown signal responsive to a comparison of a count of cycles of the pulse-width-modulated control signal in which the sensed current reaches the overcurrent threshold to a count of cycles of the pulse-width-modulated control signal in which the sensed current does not reach the overcurrent threshold, and wherein the overload protection circuitry includes: