| US 7,525,819 B2 | ||
| Switching mode power supply and method for generating a bias voltage | ||
| Hang-Seok Choi, Gunpo (Korea, Republic of) | ||
| Assigned to Fairchild Korea Semiconductor, Ltd., Bucheon (Korea, Republic of) | ||
| Filed on Feb. 28, 2006, as Appl. No. 11/364,711. | ||
| Claims priority of application No. 10-2005-0017238 (KR), filed on Mar. 02, 2005. | ||
| Prior Publication US 2006/0196757 A1, Sep. 07, 2006 | ||
| Int. Cl. H02M 3/335 (2006.01) | ||
| U.S. Cl. 363—16 [363/21.02; 363/21.04; 363/21.08; 363/21.12; 363/49; 323/238; 323/901] | 13 Claims |
| 1. A switching mode power supply including a primary coil of a transformer and a main switch, which generates an output voltage
by switching the main switch, the switching mode power supply comprising:
a bias voltage generator including an auxiliary coil of the transformer and a capacitor electrically coupled to a first terminal
and a second terminal of the auxiliary coil of the transformer;
an initial bias voltage generator, which charges the capacitor from the second terminal of the primary coil of the transformer
during a start-up of the switching mode power supply, wherein a first terminal of the primary coil of the transformer is electrically
coupled to a rectified DC voltage signal and a second terminal of the primary coil is electrically coupled to the main switch;
and
a pulse width modulator controller, which receives a first voltage of the capacitor through a first terminal and starts switching
the main switch,
wherein the pulse width modulator controller comprises:
a time delay circuit, coupled to the initial bias voltage generator, which stops the charging of the capacitor at a second
time, which is a delay time after a first time at which the first voltage is essentially equal to a reference voltage, and
starts switching the main switch.
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