| 摘要 |
PROBLEM TO BE SOLVED: To provide size, weight, and cost reduction, and facilitate mounting into a printed circuit board by building, with a simple structure, a leakage breaking function which requires no current transformer in an inverter power supply unit. SOLUTION: Respective resistance values of resistors R13 and R14 are set so that they are equal, and a connection between the resistors R13 and R14 is generally under a balanced condition in alternating current, where prescribed a.c. voltage is applied. If any leakage occurs in a loading device, an alternating current component is added to the a.c. voltage. If the voltage exceeds the prescribed one, a transistor Q10 is kept under an ON condition. If the ON condition continues in excess of a prescribed time, the resetting condition of a binary counter 806 is released. An oscillator which includes the NAND circuit 804 and an inverter 805 starts to oscillate, so that the binary counter 806 starts to count. When the count value reaches the prescribed one, a capacitor C12 is charged. After the prescribed time has passed, an output stop signal is outputted from a schmitt trigger circuit 807. |
