| US 7,577,003 B2 | ||
| Switching power supply | ||
| Masaru Nakamura, Niiza (Japan) | ||
| Assigned to Sanken Electric Co., Ltd., Niiza-shi (Japan) | ||
| Appl. No. 10/594,625 PCT Filed Feb. 14, 2005, PCT No. PCT/JP2005/002139 § 371(c)(1), (2), (4) Date Sep. 28, 2006, PCT Pub. No. WO2005/101630, PCT Pub. Date Oct. 27, 2005. |
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| Claims priority of application No. P2004-100753 (JP), filed on Mar. 30, 2004. | ||
| Prior Publication US 2007/0217234 A1, Sep. 20, 2007 | ||
| Int. Cl. H02M 3/335 (2006.01); H02H 7/122 (2006.01) | ||
| U.S. Cl. 363—21.12 [363/56.01; 363/50; 363/52; 363/55] | 7 Claims |
| 1. A switching power source comprising:
a switching element being connected in series with a primary winding of a transformer connected to a DC power source;
a first rectifying/smoothing circuit configured to rectify and smooth AC power induced by a secondary winding of the transformer;
a second rectifying/smoothing circuit configured to rectify and smooth AC power induced by an auxiliary winding of the transformer
and to provide an internal power source;
an output detection circuit configured to detect an output voltage that is provided from the first rectifying/smoothing circuit
to a load; and
a control circuit configured to control an ON-period of a pulse signal supplied to the switching element according to a feedback
voltage from the output detection circuit, the control circuit including,
an overcurrent detection circuit configured to detect whether or not an overcurrent exceeding a predetermined reference value
is passed through the switching element, and
a constant-current drooping control circuit configured to select one of a first constant current and a second constant current
smaller than the first constant current according to an overcurrent detection result from the overcurrent detection circuit
and to superpose a selected current on the feedback voltage from the output detection circuit, wherein
the control circuit controls the ON-period of the pulse signal supplied to the switching element according to a resultant
feedback voltage provided by a feedback voltage superpose circuit.
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