| US 7,521,912 B2 | ||
| Power supply apparatus | ||
| Isao Yamamoto, Kyoto (Japan); and Tomoyuki Ito, Kyoto (Japan) | ||
| Assigned to Rohm Co., Ltd., (Japan) | ||
| Appl. No. 11/792,267 PCT Filed Nov. 18, 2005, PCT No. PCT/JP2005/021241 § 371(c)(1), (2), (4) Date Jun. 04, 2007, PCT Pub. No. WO2006/059500, PCT Pub. Date Jun. 08, 2006. |
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| Claims priority of application No. 2004-350871 (JP), filed on Dec. 03, 2004; and application No. 2005-143522 (JP), filed on May 17, 2005. | ||
| Prior Publication US 2008/0129225 A1, Jun. 05, 2008 | ||
| Int. Cl. G05F 1/40 (2006.01); G05F 1/10 (2006.01); G05F 1/00 (2006.01) | ||
| U.S. Cl. 323—282 [323/284; 323/285; 323/274; 323/273; 327/536; 327/537; 327/535; 327/538; 315/291; 315/307; 315/247; 315/224] | 15 Claims |
| 1. A power supply apparatus for performing constant current driving of a load circuit, comprising:
a constant current circuit which is disposed on a path for driving the load circuit;
a voltage generating circuit which outputs a driving voltage to the load circuit;
a monitoring circuit which monitors a voltage across the two ends of the constant current circuit; and
a control unit which controls the driving voltage that is output from the voltage generating circuit, wherein
the monitoring circuit includes a threshold voltage source which generates a threshold voltage that follows the fluctuation
of the voltage at which the constant current circuit can operate stably, and outputs to the control unit a result obtained
by comparing the voltage across the two ends of the constant current circuit and the threshold voltage generated by the threshold
voltage source, and
the control unit controls the voltage generating circuit on the basis of the output of the monitoring circuit.
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