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US 5,805,020 AGranted
Silent start class D amplifier
AssigneeHarris Corporation
InventorsGeorge Edward Danz, Larry A. King, John K. Fogg
Life of this patent
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Abstract
Start up noise in a class D amplifier--is corrected by adding an analog switch S1 to the integrator circuit A1. A resistor R3 in the feedback path of A1 prevents A1 from saturating. In an alternate embodiment silent start switch connects a variable resistance to the comparator input. The resistance gradually increases.
Claims11
A silent start circuit comprising
- (a) a Class D amplifier having an input for receiving a signal with an audit frequency, means for sampling the audio input signal at a frequency substantially greater than the highest audit frequency in the audio input signal, and means for comparing the sampled audit signal to a reference voltage signal to provide an output series of width modulated pulses, each pulse having the amplitude of the reference voltage signal and a width proportional to the amplitude of the sampled audit signal, the series of pulses having a frequency substantially greater than said audio frequency;
- (b) a bridge driver circuit having an input for receiving the output series of pulses of the Class D amplifier and translating the voltage level of the pulses from the reference voltage to a driver voltage level, and means for generating a power mosfet gate driver signal comprising a series of output driver pulses having pulse widths proportional to the sampled audio signal and pulse amplitudes at the driver voltage level;
- (c) an amplifier having a first input connected to the audio input signal and through a feedback path to the output of the bridge driver circuit and an output coupled to the input of the Class D amplifier, said amplifier selectively switchable between a first mode of operation for integrating the audio input and a second mode of operation for summing the audio input and the Class D amplifier output.
A silent start circuit comprising
- (a) a class D amplifier having
- an input for receiving an input comprising an error signal and audio signal with an audio frequency,
- an integrating amplifier coupled to the input for integrating the input signal to provide a first comparator input signal,
- a comparator for comparing the first comparator input signal to a second comparator input comprising a reference oscillator voltage signal to generate an output series of width modulated pulses, each pulse having the amplitude of the reference voltage signal and a width proportional to the amplitude of the sampled audio signal, the series of pulses having a frequency substantially greater than said audio frequency;
- switch means having
- a disable position for connecting the first comparator input to a reference voltage source to generate a comparator output having a 50% duty cycle saturating the integrating amplifier, and
- an enable position for gradually connecting the output of the integrating amplifier to the first comparator input and gradually unsaturating the integrating amplifier.
4 more elements
Dependencies are inferred from the claim text.