Abstract: A DC-DC flyback converter that has a controlled synchronous rectifier in its secondary circuit, which is connected to the secondary winding of a main transformer. A main switch (typically a MOSFET) in the primary circuit of the converter is controlled by a first control signal that switches ON and OFF current to the primary winding of the main transformer. To prevent cross-conduction of the main switch and the synchronous rectifier, the synchronous rectifier is turned ON in dependence upon a signal derived from a secondary winding of the main transformer and is turned OFF in dependence up a signal derived from the first control signal. In one embodiment the first control signal is inverted and delivered to a logic circuit along with the voltage across the main transformer secondary winding and the voltage across the synchronous rectifier.

Abstract: A DC-DC switching converter device (101), in particular a quarter-brick or eighth-brick device having an industry standard pin out, comprises a pulse-width modulation circuit (132) for driving a power converting switch, a trim connector (109) for adjusting an output voltage of the device, where the device (101) is designed such that the pulse-width modulation circuit (132) is synchronizable to an external oscillator by an external synchronization signal applied to the trim connector. A DC-DC converting circuit comprises a plurality of DC-DC switching converters (101) featuring trim connectors (109) for adjusting output voltages of the converters (101), whereby the converters (101) are connected such that they share a common input bus. It further features a system EMI (electromagnetic interference) filter common to all the DC-DC switching converters (101) and an external oscillator delivering an external synchronization signal to the plurality of DC-DC switching converters (101).

Abstract: The present invention is directed to a switch mode power converter for supplying an output power to a load, which includes a switching device having a switching input, a switching output, and a control input for enabling or disabling the switching device from conducting current from the switching input to the switching output. The converter also includes a network in which the switching device input, the switching device output, and the load are connected together to form a circuit. The converter also includes a bias winding in the circuit for producing a bias voltage representative of the output power, and a control circuit. The control circuit is for (a) determining the rate of change of the bias voltage, (b) characterizing the rate of change, and (c) controlling the control input as a result of the characterization (b).

Abstract: DC-DC converters such as flyback converters achieve self-regulation by communication information between primary and secondary circuits through the power transformer. Operating in accordance with a generalized concept or algorithm, the converter can be bi-directional and self-regulating. Control of the turn OFF times of semiconductor switches in first and second circuits coupled to first and second windings of the power transformer determines whether power flow is in one direction through the converter or the other direction. Turn ON timing of each semiconductor switch is when there is a reverse current through the switch and voltage across the switch is at or near zero. Turn OFF of a switch can be controlled from one or more operating parameters of the converter such as output voltage, in which case the converter's self-regulation is affected through duty cycle variation with variations in output voltage.

Abstract: An improved snubber is electrically switched to close a current path to a capacitor (C) in a series connected RC circuit at the onset of an abrupt voltage change otherwise producing ringing in a resonant circuit to which the snubber circuit is connected. The current path to the capacitor (C) is then interrupted before the capacitor (C) discharges and thereafter at each such voltage change in the resonant circuit the capacitor (C) is no longer charged from its totally discharged state but nevertheless damps the ringing by virtue of current flow to the nearly completely charged capacitor (C). By preventing complete charging and discharging of the capacitor (C) in the RC circuit every cycle, power dissipation in the resistance of the snubber circuit is greatly reduced.

Abstract: A low profile magnetic element used in cooperation with a multilayer printed circuit board has two or more core arms penetrating the board from one outer surface to the other and a series of magnetic core elements, at least one on each side of the board, bridging pairs of the core arms to form a closed, unbranched flux path. Series-connected windings form a transformer primary and are wound on the core arms that penetrate the board. Parallel-connected windings form a transformer secondary and are also wound on the core arms. The series-connected windings and the parallel-connected windings may be buried windings printed on internal surfaces of the multilayer board. The connected in series primary windings all have the same number of turns and the parallel-connected secondary windings all have the same number of turns. The parallel secondary windings are connected in current additive fashion to afford a high current transformer output.

Abstract: A power device such as a forward converter employing a main switch in series with a power transformer coupling an input, primary circuit and an output, secondary circuit has its transformer reset from a reset capacitor that is switched. Switching of the reset capacitor is effected by a reset switch, preferably a MOSFET, the control electrode of which is driven from a reset winding on the power transformer. Current flow between the reset capacitor and the primary winding resets the transformer. The capacitor can be chosen such that flux density in the transformer core is substantially symmetrical about zero. Leakage and magnetizing conductance energy is recycled. Large spikes are not produced across the main switch.

Abstract: A converter topology that eliminates reverse recovery losses in its output rectifying semiconductor devices employs an AC injection voltage source in series with a power transformer primary winding. Input semiconductor switches in the converter's primary circuit are controlled to provide in the power transformer secondary a voltage across the winding or windings in a first direction forward biasing one of the output rectifying devices followed by a lower level reverse biasing voltage produced by the injection voltage. This lower level voltage across the secondary turns off the previously conducting rectifier device and drives carriers out of its semiconductor junction or junctions to eliminate reverse recovery losses occurring when the secondary applies a higher level reverse bias across the non-conducting rectifier device.