Abstract: Differential measurement of a transformer magnetizing current and a delta-modulation technique is used to provide compensation for dc saturation of the transformer core, with faster response times, low losses, and with immunity to dc drift in the measuring electronics. During the half-cycle in which the output voltage transitions from its positive maximum to its negative maximum, the positive peak value of the magnetizing current is determined, and during the half-cycle in which the output voltage transitions from its negative maximum to its positive maximum, the negative peak value of the magnetizing current is determined. The positive peak magnetizing current value is compared to the similar value from the previous cycle, and the onset of core saturation in the positive direction is then determined. The negative peak magnetizing current value is compared to the similar value from the previous cycle, and the onset of core saturation in the negative direction is then determined.

Abstract: Notching in a switch-mode converter is compensated for to restore a sinusoidal output voltage waveform to the output of the converter, regardless of the load current level, power level, or power factor (both distortion and displacement power factor). Waveform smoothing for a waveform in a switch-mode converter having a DC bus voltage and an output filter inductance comprises determining a ripple current in the converter; determining a time-to-zero; determining a turn-on time; determining the lesser of the time-to-zero and the turn-on time; determining a duty cycle modification based on the lesser of the time-to-zero and the turn-on time; and applying the duty cycle modification to the waveform.

Abstract: Apparatus and methods for detecting the direction of a fault in relation to a switch connected between a source and a load are shown to include a voltage sampler for generating samples of the voltage during first and second power cycles. A current sampler generates samples of the current during first and second cycles. A first comparator compares the current samples from the first cycle to the current samples from the second cycle and determines the sign of the difference between the samples. A second comparator compares the sign of the voltage from the first cycle to the sign of the current difference determined by the first comparator and provides an indication of fault direction in relation to such comparison. The apparatus also includes a fault inception determiner, for providing a fault inception indication in relation to the voltage samples from the first and second cycles.