| 摘要 |
PROBLEM TO BE SOLVED: To provide a power circuit which is so structured as to keep the output voltage constant by indirectly detecting the voltage at the secondary side insulated from the primary side and thereby can output constant output voltage. SOLUTION: This power circuit 1 has a surge detection circuit 70. The surge detection circuit 70 detects the voltage including surge voltage induced between terminals (c) and (d) of a voltage detection winding 42 and then outputs the detected voltage to a voltage control section 6. When the voltage control section 6 is input with larger voltage from the surge detection circuit 70, it increases the energy to be transmitted to a secondary winding 43. Therefore, if an energy loss is generated due to surge voltage in a secondary-side rectifier circuit 3, energy transmitted to the secondary winding 43 is increased to compensate for the energy loss and increase the voltage induced between terminals (f) and (g) of the secondary winding 43 to prevent the decline in the output voltage. Thereby, constant output voltage can be obtained.
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