Abstract: An AC-DC power converter is provided with two pairs of self-driven synchronous rectifier switches in addition to, or in place of, diode bridge rectifiers for boosting efficiency and reducing cost. An AC sensing circuit is coupled to AC input terminals, and a DC level shifting circuit applies a DC offset to an AC input signal received via the sensing circuit. A comparator circuit determines positive and negative half waves of the AC input signal relative to the DC offset value. Gate drive signals are provided for driving a first set of parallel rectifier switches during a positive half cycle of the AC input signal, and for driving a second and opposing pair of parallel rectifier switches during a negative half cycle of the AC input signal. In an embodiment, high side gate drive signals may be electrically isolated from the active rectifier control circuitry.

Abstract: An AC-DC power converter is provided with two pairs of self-driven synchronous rectifier switches in addition to, or in place of, diode bridge rectifiers for boosting efficiency and reducing cost. An AC sensing circuit is coupled to AC input terminals, and a DC level shifting circuit applies a DC offset to an AC input signal received via the sensing circuit. A comparator circuit determines positive and negative half waves of the AC input signal relative to the DC offset value. Gate drive signals are provided for driving a first set of parallel rectifier switches during a positive half cycle of the AC input signal, and for driving a second and opposing pair of parallel rectifier switches during a negative half cycle of the AC input signal. In an embodiment, high side gate drive signals may be electrically isolated from the active rectifier control circuitry.

Abstract: An open loop half-bridge LLC power converter includes circuitry to reliably increase hold-up time without sacrificing efficiency. An LLC resonant circuit includes resonant inductance, a primary transformer winding, and resonant capacitance. An auxiliary circuit includes an auxiliary transformer winding, an inductor, and a third switching element coupled in series. A controller is coupled across a voltage sensor and effective thereby to determine a holdup time condition. In a “normal” operating condition the controller generates switch driver signals to turn OFF the third switching element and disable the auxiliary circuit, and in a hold-up time condition the controller turns ON the third switching element and enables the auxiliary circuit wherein the output voltage is increased via current supplied from the auxiliary winding. In various embodiments the auxiliary winding may be an auxiliary primary or secondary, or a secondary to an auxiliary primary winding of a second transformer.

Abstract: A snubber circuit and corresponding power converter topology for controlling the voltage across the resonant capacitor at turn on of a control switch so as to suppress a spike at the switch caused by the large current pulse and parasitic inductance of the power converter. The suppression of the spike reduces conduction losses and increases efficiency. According to one embodiment, the snubber circuit in a boost converter topology includes a second winding tapped from the main boost inductor and connected in series with a first diode and a second diode. A resonant capacitor and the second diode are connected in a series combination which is in parallel with the main boost diode. The second winding is connected in series with the first diode and the second diode between the output terminals of the converter. Alternatively, the snubber circuit is used in flyback, buck, and forward converter topologies.

Abstract: A power converter circuit includes an input switching circuit, an isolation circuit, a rectifier circuit that includes a least a pair of rectifiers, and an output circuit. The input switching circuit receives a first voltage and generates an AC voltage. The isolation circuit has a primary side configured to receive the AC voltage from the input switching circuit and a secondary side. The secondary side communicates with the rectifier circuit and the output circuit. The output circuit includes a secondary inductor and a diode. The secondary inductor communicates with a primary inductor and either the rectifier circuit or the secondary side. The diode communicates with the primary inductor, the secondary inductor, and the rectifier circuit. The secondary inductor inhibits current flow through the rectifier circuit and forces current flow through the diode when no voltage is applied to the primary side of the isolation circuit.

Abstract: A power converter circuit includes an input switching circuit, an isolation circuit, a rectifier circuit that includes a least a pair of rectifiers, and an output circuit. The input switching circuit receives a first voltage and generates an AC voltage. The isolation circuit has a primary side configured to receive the AC voltage from the input switching circuit and a secondary side. The secondary side communicates with the rectifier circuit and the output circuit. The output circuit includes a secondary inductor and a diode. The secondary inductor communicates with a primary inductor and either the rectifier circuit or the secondary side. The diode communicates with the primary inductor, the secondary inductor, and the rectifier circuit. The secondary inductor inhibits current flow through the rectifier circuit and forces current flow through the diode when no voltage is applied to the primary side of the isolation circuit.