Patent ID: 7348840

Claim:
A feedback controller for a PWM amplifier, the controller comprising: a signal input for receiving a pulse width modulated (PWM) input signal whose duty cycle represents a desired analogue output signal; a feedback input for receiving a feedback signal representing an actual PWM output signal of the amplifier; means for generating a filtered error signal comprising a filtered representation of differences between the input signal and the feedback signal; means for comparing the filtered error signal with a reference to generate a provisional PWM switching control signal for controlling the PWM amplifier; and a pulse conditioner comprising a sequential logic circuit arranged to receive both the provisional PWM switching control signal and the PWM input signal for outputting to the amplifier a conditioned PWM switching control signal comprising the provisional PWM switching control signal modified so as to inhibit a transition in the switching control signal under conditions defined by reference to past transitions in the PWM input signal.