| 摘要 |
PROBLEM TO BE SOLVED: To provide a protecting circuit and a switch-mode power source corresponding thereto capable of operating with high reliability even in a low- powered switch-mode power source. SOLUTION: The protecting circuit has a transformer consisting of a switching transistor T20 and a first winding W1 and its auxiliary winding W2 for feeding a service voltage Vcc to the switching transistor T20. Also for this constitution, there are mounted in the circuit a clamp circuit CL having a switching element T21 that reduces the service voltage Vcc when an error occurs, and a holding circuit HO that feeds the current for the sake of the clamping circuit CL. The current of the holding circuit HO extends a switch-off time when an error occurs and rapidly starts up the power when the service voltage decreases. Hereby, the occurrence of a rapid variation transition (hiccup stage) is avoided.
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