Dual feedback control for a high-efficiency class-d power amplifier circuit
First Claim
1. A dual feedback control system for a Class-D power amplifier circuit including a resonant circuit having a variable impedance, comprising:
- a phase control feedback loop, including phase detecting means for detecting the phase angle between the resonant circuit voltage and resonant circuit current, said phase control feedback loop varying the phase angle of the resonant circuit current to tune said resonant circuit under different load conditions; and
an amplitude control feedback loop, including amplitude comparator means for comparing the amplitude of the resonant circuit impedance with a reference amplitude, said amplitude control feedback loop varying the amplitude of the resonant circuit current to tune said resonant circuit under different load conditions.
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Accused Products
Abstract
A dual feedback control system for a Class-D power circuit maximizes efficiency by controlling the magnitude and phase angle of the resonant load circuit using two separate feedback loops. The first feedback loop changes the value of a first variable capacitor in response to difference in magnitude between the actual load impedance and the desired load impedance. The second feedback loop changes the value of a second variable capacitor in response to the phase difference between the actual phase angle and the desired phase angle. In this way, the real and imaginary components of the load impedance are controlled so that the Class-D circuit is in tune, and hence efficiency is maximized, over a wide range of load impedances. The dual feedback control of the present invention may be advantageously employed in the ballast of an electrodeless HID lamp system.
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Citations
8 Claims
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1. A dual feedback control system for a Class-D power amplifier circuit including a resonant circuit having a variable impedance, comprising:
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a phase control feedback loop, including phase detecting means for detecting the phase angle between the resonant circuit voltage and resonant circuit current, said phase control feedback loop varying the phase angle of the resonant circuit current to tune said resonant circuit under different load conditions; and an amplitude control feedback loop, including amplitude comparator means for comparing the amplitude of the resonant circuit impedance with a reference amplitude, said amplitude control feedback loop varying the amplitude of the resonant circuit current to tune said resonant circuit under different load conditions. - View Dependent Claims (2, 3, 4)
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5. A ballast for a high intensity discharge lamp of the type having an excitation coil situated about an arc tube for exciting an arc discharge in an ionizable fill contained in said arc tube, comprising:
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a Class-D power amplifier including two switching devices coupled in series in a half-bridge configuration and having an output resonant circuit coupled at the junction between said two switching devices; a phase control feedback loop, including phase detecting means for detecting the phase angle between the resonant circuit voltage and resonant circuit current, said phase control feedback loop varying the phase angle of the resonant circuit current to tune said resonant circuit under different load conditions; and an amplitude control feedback loop , including amplitude comparator means for comparing the amplitude of the resonant circuit impedance with a reference amplitude, said amplitude control feedback loop varying the amplitude of the resonant circuit current to tune said resonant circuit under different load conditions. - View Dependent Claims (6, 7, 8)
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Specification