| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply, where a depletion type junction FET (JFET) is used and an idling current is zero, and to provide a standby electric power circuit using the power supply and a charging circuit for storage batteries. SOLUTION: The drain of the JFET Q1 is connected to the positive terminal of a DC power supply E as shown in Fig.1, a capacitor C1 is connected between the source of Q1 and the negative terminal (0 point) of E, and voltage, where a gate side is positive, is applied between the gate of Q1 and the 0 point, thus obtaining a power circuit of which the idling current is zero, and setting both the ends of C1 to be the power supply. Both the ends of C1 are connected to the power supply terminal of a control circuit SG as an auxiliary power supply EH. A load circuit RL and a MOS FET Q2 are connected in series between the positive and negative terminals of E from a positive side, and output OP of SG is connected to the gate of Q2 for turning on and off Q2, thus obtaining the standby electric power circuit having an idling current of zero. Fig. 3 and Fig. 4 are other embodiments, and a circuit is applied to an AC power supply. The RL is not connected to the MOSFET, and the storage battery is connected instead of the capacitor C1, thus obtaining the charging circuit for the storage battery. COPYRIGHT: (C)2007,JPO&INPIT
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