| 摘要 |
PROBLEM TO BE SOLVED: To provide a protection circuit capable of suppressing maximum drain current flowing to an FET(field effect transistor), before a short circuit function of a DC(direct current) power supply device works when a load side is short-circuited, and preventing breakage of the FET and realizing miniaturization. SOLUTION: In an FET switching circuit turning ON/OFF of an output voltage from the DC power supply device with a short circuit cutoff function, a source terminal of an FET Q1 is connected to a positive electrode of the DC power supply device, and a drain terminal is connected to a positive electrode side of the load circuit. Through a resistance R3 and a switch S1, a gate terminal is connected to a negative electrode of the DC power supply device and the negative electrode of the load circuit. A cathode terminal of a shunt regulator IC IC1 is connected to the source terminal, and an anode terminal of the shunt regulator IC IC1 is connected to the gate terminal. To the first resistance R1 dividing a gate voltage of the FET Q1 and the second resistance R2, a reference terminal of the shunt regulator IC IC1 is connected, thus, the protection circuit is constituted, to be set up.
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