| 摘要 |
PROBLEM TO BE SOLVED: To provide a power circuit having a startup circuit capable of improving a power factor under light load and meeting changes in output conditions rapidly without use of external parts, and a short detecting function for a feedback signal. SOLUTION: This power circuit includes an offset adjustment current generating comparator 11 for monitoring the output of an error amplifier 2 to generate offset adjustment current during light load, a sense current comparator 4 for comparing the output signal of a multiplier 3 with the signal of AC line current to generate a reset signal is adjusted so that the offset may be on a minus side by inputting generated offset adjusting current IOS to compensate for output characteristics under light load, thereby improving the power factor. A timer 10 is provided which monitors a zero cross input signal directly, thereby forming the built-in startup circuit capable of meeting the changes in the output conditions rapidly. A short detection comparator 12 is provided which monitors the feedback signal directly, thereby eliminating the need for external parts.
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