Abstract: An amplifier circuit for efficiently driving a tuned resonant load where the amplifier circuit controls the continuously variable resonant frequency of the tuned resonant load so as to match step changes or slower changes in the frequency of the signal with which it is being driven. The circuit includes a tuned resonant load, a driver, a controller and a feedback loop. The driver is coupled to the load and drives it with a driving signal at a frequency under the control of the controller. The controller dynamically controls the resonant frequency of the tuned resonant load in response to an error signal received through the feedback loop. The error signal represents the mismatch in phase between the resonant phase of the load current and the phase of the driving signal, or between the resonant phase of the tuning capacitor voltage offset by 90 degrees and the phase of the driving signal.

Abstract: An amplifier circuit for efficiently driving a tuned resonant load where the amplifier circuit controls the continuously variable resonant frequency of the tuned resonant load so as to match step changes or slower changes in the frequency of the signal with which it is being driven. The circuit includes a tuned resonant load, a driver, a controller and a feedback loop. The driver is coupled to the load and drives it with a driving signal at a frequency under the control of the controller. The controller dynamically controls the resonant frequency of the tuned resonant load in response to an error signal received through the feedback loop. The error signal represents the mismatch in phase between the resonant phase of the load current and the phase of the driving signal, or between the resonant phase of the tuning capacitor voltage offset by 90 degrees and the phase of the driving signal.

Abstract: An apparatus and method for continuous variable reactive impedance control. The apparatus and method enable the continuous variation of the reactive impedance of an oscillating circuit. A reactive component, in one embodiment a capacitor, is switched into the oscillating circuit for a duration at the beginning and end of each half cycle of the oscillation frequency. Through varying the duration, the oscillation frequency is varied between the frequency that occurs without the reactive component in the circuit and the frequency with the reactive component permanently in the circuit. A controller determines the duration and controls a switch coupled to the reactive component. The apparatus and method may be used to adjust the oscillation frequency of a resonant circuit or to match the resonant frequency to a driving frequency in a driven oscillating circuit so as to improve efficiency.

Abstract: An apparatus and method for continuous variable reactive impedance control. The apparatus and method enable the continuous variation of the reactive impedance of an oscillating circuit. A reactive component, in one embodiment a capacitor, is switched into the oscillating circuit for a duration at the beginning and end of each half cycle of the oscillation frequency. Through varying the duration, the oscillation frequency is varied between the frequency that occurs without the reactive component in the circuit and the frequency with the reactive component permanently in the circuit. A controller determines the duration and controls a switch coupled to the reactive component. The apparatus and method may be used to adjust the oscillation frequency of a resonant circuit or to match the resonant frequency to a driving frequency in a driven oscillating circuit so as to improve efficiency.