Abstract: A power factor correction controller is disclosed which extracts RMS information from a rectified AC input line voltage signal using a sample and hold analog to digital conversion approach. The controller then processes a digital word representing the RMS information through the application of a programmable mathematical function. The result is converted to analog form and provided as an input to an analog multiplier. The controller also monitors the output load power of an isolated boost converter circuit and linearly reduces the overlap delay time of a MOSFET transition switch when the load power decreases.

Abstract: A controller for supplying a switching signal to a switched mode power supply, includes a sinusoidal-like wave generator, and circuitry for selectively shifting a dc level in the sinusoidal-like wave whereby a duty cycle of the sinusoidal-like wave at a predetermined threshold level, corresponding to a turn-on level of a power switch in the switched mode power supply, is effectively controlled.

Abstract: A bridge-type primary switching circuit (12) is represented by a pulsed voltage source (VSW). The primary switched waveform is transformed to secondary circuit (14) using a transformer (T1) with the required turns ratio N and a center-tapped secondary winding (16). Half-bridge rectifier (18) formed by diodes (DR1) and (DR2) rectifies the secondary waveform and feeds the waveform through a low-pass filter (LF) and (CF) to obtain the desired DC output voltage. The snubber circuit (20) is represented by switch-diode-capacitor combinations (SA-DS1-CS1) and (SB-DS2-CS2) across each rectifier (DR1) and (DR2). Capacitances (CS1) and (CS2) are selected large enough such that their voltages remain essentially constant during a switching cycle. The controlled switches (SA) and (SB) are turned ON with a specific delay after the primary voltage reaches a magnitude close to the input voltage in order to allow the rectifier diodes (DR1) and (DR2) to be commutated.