Digital signal processing for linearization of small input signals to a tri-state power switch
First Claim
1. A method for linearizing the output of at least one power switch having switch timing error in an amplifier receiving an input signal and providing a switched output signal, said method comprising the steps of:
- producing a compensated composite waveform by modulating said input signal with a bi-state compensating pulse waveform; and
effecting common mode cancellation of said switch timing error by passing said compensated composite waveform through said at least one power switch having switch timing error to provide said switched output signal.
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Accused Products
Abstract
An all digital switching amplifier wherein linearization of the power switch is accomplished solely by using three states. A small, fixed width, bi-state compensating carrier waveform is added to the leading or training edges of an oversampled main input pulse producing a compensated composite waveform. This compensating carrier linearizes output from a power switch by effecting common mode cancellation of switch time errors. Output pulse width combinations for the compensating carrier are obtained from a look-up table stored in memory. A correction mechanism is implemented to correct for harmonic distortion that is dependent on the modulation level or index and results from the compensating carrier modulation. The correction mechanism applies the inverse of the modulation induced distortion to the oversampled compensated composite input signal to null distortion products resulting from the modulation scheme used to apply the small carrier to linearize the performance of the tri-state power switch. Digital timing control of the power switch'"'"'s deadband ensures accuracy of the timing and sequence in which individual switches within the power switch H-bridge are turned off and turned on, so as to preclude a short circuit across the power supply. A high speed clock used in linearizing the power switch provides a timing reference to generate the necessary deadband timing delays and pulse width increments. The output bridge uses enhancement mode MOSFETs.
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Citations
18 Claims
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1. A method for linearizing the output of at least one power switch having switch timing error in an amplifier receiving an input signal and providing a switched output signal, said method comprising the steps of:
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producing a compensated composite waveform by modulating said input signal with a bi-state compensating pulse waveform; and effecting common mode cancellation of said switch timing error by passing said compensated composite waveform through said at least one power switch having switch timing error to provide said switched output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A tri-state digital switching amplifier receiving an input signal and having a plurality of output modes including a first mode, a second mode and a third mode, and providing a switched output signal, comprising:
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a digital signal processor receiving said input signal and processing said input signal by modulating said input signal with a bi-state compensating pulse waveform to produce a compensated input signal; at least one power switch including switch timing error and effecting switching between said first mode, said second mode and said third mode, said at least one power switch receiving said compensated input signal from said digital signal processor and outputting said compensated input signal in at least one of said first mode, said second mode and said third mode to provide said switched output signal substantially free of said switch timing error. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification