| US 7,616,422 B2 | ||
| Over current protection circuit for power supplies | ||
| Tsung-Ming Lee, Nan-Tou (Taiwan); Yu-Feng Fu, Nan-Tou (Taiwan); and Chin-Liang Pai, Nan-Tou (Taiwan) | ||
| Assigned to Universal Scientific Industrial Co., Ltd., Nan-Tou (Taiwan) | ||
| Filed on May 11, 2007, as Appl. No. 11/798,194. | ||
| Claims priority of application No. 95218778 U (TW), filed on Oct. 24, 2006. | ||
| Prior Publication US 2008/0094770 A1, Apr. 24, 2008 | ||
| Int. Cl. H02H 3/00 (2006.01) | ||
| U.S. Cl. 361—94 [361/18; 361/93.1] | 19 Claims |
| 1. An over current protection circuit for a power supply, comprising:
an input detection unit receiving a current sensing signal to generate an input voltage;
a comparison circuit connecting to the input detection circuit and comparing the input voltage with a reference voltage to
generate a compared voltage;
a positive feedback sampling and maintaining unit connecting to the input detection unit and the comparison circuit and providing
a first and a second feedback current based on the compared voltage, wherein the first feedback current is provided to the
input detection unit for further determining the period the over current protection circuit spends operating in normal mode;
a timing circuit connecting to the comparison circuit and the positive feedback sampling and maintaining unit and determining
the operation cycle of the over current protection circuit; and
an output switch connecting to the timing circuit and according to the second feedback current determining whether the over
current protection circuit restrains the outputs of the power supply.
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