Tdk Corporation

Masaharu Hatta

Masato Watanabe

Katsuhiko Shimizu

Haruhiko Hatakeyama

A switching power supply which can prevent the output voltage Vout from fluctuating or undershooting when the instruction for stopping the operation is issued is disclosed. A switching power supply according to the present invention employs a transformer having a primary coil and a secondary coil, a switching circuit connected between an input terminal and the primary coil of the transformer, a rectifier connected to the secondary coil of the transformer, a smoothing circuit located at a subsequent stage of the rectifier and including an output capacitor, a control circuit controlling the switching circuit, and an operating voltage generating circuit, responsive to an instruction for stopping a switching operation, for supplying an operating voltage to the control circuit using at least energy stored in the output capacitor. Thus, the switching power supply of the present invention can substantially linearly lower the output voltage Vout.

Switching power supply using a transformer, rectifier, control circuit and voltage generating circuits

A switching power supply unit includes: a switch circuit equipped with a first transistor, the switch circuit converting a DC input into an AC; a transformer for transforming the AC; an output rectifier equipped with a second transistor serially connected to the transformer and a third transistor connected in parallel to the transformer, the output rectifier rectifying the output of the transformer; and a control circuit for controlling ON/OFF of the first to third transistors. The control circuit turns ON the second transistor before turning ON the third transistor and turning ON the first transistor.

Power supply unit and driving method thereof

A plurality of converter circuits A and B are provided. The converter circuits A and B have circuit structures that are identical to each other. In the converter circuit A, a resonant capacitor 31, a resonant inductor 32 and a primary winding 51 of a transformer 5 are connected in series, with the two ends of the serial circuit thus achieved connected between the connecting point of switching elements 11 and 12 and one end of a source 10. The output ends of output rectifier smoothing circuits 7 and 8 are connected commonly. Resonant circuits 3 and 4 of the converter circuits A and B are connected with each other.

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Chuo-ku, Japan

Masaharu Hatta