Patent ID: 7821239
Filing Date: 2010-10-26
Classification: H02M

Abstract:
1. A switching power-supply unit comprising: an inductor or a transformer; a plurality of switching elements arranged to switch a current flowing in the inductor or the transformer and to convert power by turning on and off the plurality of switching elements; and a plurality of switching control circuits arranged to turn on a next one of the plurality of switching elements in accordance with a change of a voltage or a current generated due to turning off of one of the plurality of switching elements in an ON-state, to sequentially turn on and off the plurality of switching elements in accordance with each other, to repeat a series of on-off operations of the plurality of switching elements periodically, to determine an ON-period of each of the plurality of switching elements in accordance with a condition individually provided for each of the plurality of switching elements, and to control the ON-period of each of the plurality of switching elements; wherein the plurality of switching elements includes at least first, second, and third switching elements; the plurality of switching control circuits includes at least first, second, and third switching control circuits; the first switching control circuit determines an ON-period of the first switching element such that a first output voltage is set to a predetermined value; the second switching control circuit determines an ON-period of the second switching element such that a second output voltage is set to a predetermined value; the third switching control circuit determines an ON-period of the third switching element such that a third output voltage is set to a predetermined value; and the predetermined values of the first, second, and third output voltages are different from one another.