Abstract: A resonant switching power system operates with two resonant frequencies. A first frequency depends on the secondary leakage inductance of an output transformer and capacitor. The first frequency varies with changes in the load because load changes alter the leakage inductance. A second resonant frequency depends on the gate source capacitance of two MOSFET power devices in the circuit and the leakage inductance of the circuit's driving transformer. Power is thereby supplied that is always in phase with the load so that switching in the power supply occurs when current is near zero. High thermal efficiency is thereby achieved.

Abstract: Apparatus and methods for reducing radio frequency interference produced by switching amplifiers, includes a variable-order noise shaper in a system that includes an AM tuner. An alternative implementation involves determining the tuned frequency of a radio signal. A first sampling rate is provided at which the radio signal is to be sampled. The first sampling rate is associated with a plurality of first harmonic frequencies. A second sampling rate is also provided and is associated with a plurality of second harmonic frequencies different than the first harmonic frequencies. The method involves selectively sampling the radio signal at one of the first and second sampling rates, wherein the first sampling rate is selected when the first harmonic frequencies do not coincide with the tuned frequency, and the second sampling rate is selected when the second harmonic frequencies do not coincide with the tuned frequency.

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.

Abstract: Apparatus for compensating an optical sensor utilizing a light emitting diode and a monolithic dual element photodiode as a null position sensor for changes in optical output efficiency or gain due to variations in temperature without knowledge of relative or absolute temperature. The optical sensor includes a light emitting diode and a dual element photodiode spaced apart from the light emitting diode and located so that each element of the dual element photodiode is equally illuminated. A pendulous mass is disposed between the light emitting diode and the dual element photodiode detector such that as it moves the amount of illumination received by each of the dual elements differs. Electrical apparatus is provided for producing a first signal proportional to the difference in output from the two photodiode elements, and this signal is used to null the position of the pendulous mass.