A switching power supply unit comprising: a transformer having a primary winding and a secondary winding, a capacitor coupled to the transformer, a first switching circuit connected in series with a series circuit of the primary winding and an input power source, the first switching circuit comprising a parallel circuit comprising a first switching element, a first diode and a first capacitor, a second switching circuit connected in parallel with the primary winding, the second switching circuit comprising a parallel circuit comprising a second switching element, a second diode and a second capacitor, first and second switching controlling circuits connected to the first and second switching circuits, respectively for controlling the first and second switching elements so as to turn on/off alternately with a period in which the first and second switching elements turn off being interposed therebetween, a rectifying and smoothing circuit connected to the secondary winding; and voltage detection and voltage reduction circuit having a control signal input terminal and connected to the rectifying and smoothing circuit, the voltage detection and voltage reduction circuit detecting an output voltage of the rectifying and smoothing circuit and outputting a feedback signal to the first switching controlling circuit such that an output voltage of the rectifying and smoothing circuit is stabilized at one of a first voltage and a second voltage lower than the first voltage based on a signal applied to the control signal input terminal.

In accordance with an embodiment of the disclosed matter, a voltage regulator may supply power to a component within a computer system. A timer may be provided. The voltage regulator may operate synchronously, and when the timer expires the voltage regulator may operate non-synchronously. For one embodiment, the voltage regulator may operate non-synchronously when the timer expires and the component is in a sleep state.

In accordance with an embodiment of the disclosed matter, a voltage regulator may supply power to a component within a computer system. A timer may be provided. The voltage regulator may operate synchronously, and when the timer expires the voltage regulator may operate non-synchronously. For one embodiment, the voltage regulator may operate non-synchronously when the timer expires and the component is in a sleep state.

An switching converter, having a transformer having primary, secondary and auxiliary windings, an actively controlled switch, a capacitor and a first passive switch in series across the primary, the auxiliary winding of the transformer and a second passive switch being connected in series to the node between the capacitor and first passive switch, with the active switch being connected to a side of the primary winding opposite the first passive switch. The method energizes a transformer core with the primary winding and discharges a capacitor during an ON state; and clamps a voltage across the active switch with the capacitor, and transfers magnetizing energy to the secondary winding during an OFF state, to efficiently transfer energy corresponding to a switching transient to the load while limiting maximum active switch voltage.

A voltage boost power converter circuit, having an input inductor, active switch, and a transformer having primary, secondary and auxiliary windings. A clamping capacitor and a first passive switch are in series across the primary winding. The auxiliary winding and a second passive switch are in series, connected to the node between the clamping capacitor and first passive switch. The active switch is connected between ground the primary winding. A bulk capacitor forms a series loop including the active switch and primary winding. The method efficiently resets a the transformer, by transferring power to a load through the primary winding, and discharging a clamping capacitor through a separate inductively linked winding of the transformer during an ON state; and clamping the active switch voltage with the clamping capacitor, charging the clamping capacitor with a leakage inductance of the transformer, and charging the bulk capacitor during an OFF state.