| 摘要 |
PROBLEM TO BE SOLVED: To prevent the occurrence of a fault such as the breakage of a circuit element caused by the unlimited rise of an output voltage by the effect that a secondary-side output pin is opened due to a product safety test, an unexpected trouble or the like, and a light emitting element for transmitting a voltage signal cannot be lit. SOLUTION: A light emitting diode PD and a shunt regulator SR are connected to a first output line VCC1 of a secondary DC power supply circuit 2B, a voltage determination circuit 7 is connected to the anode side of the light emitting diode PD, power is fed to the light emitting diode PD from a second output line VCC2 when a voltage of the first output line VCC1 is lowered, and the light emitting function of the light emitting diode PD is maintained. The voltage determination circuit 7 is constituted of a voltage drop determining NPN transistor Q1, a reverse NPN transistor Q2, and an on/off-PNP transistor Q3. A third output line VCC3 is connected to a reference terminal SRa of a shunt regulator SR. COPYRIGHT: (C)2007,JPO&INPIT
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