Abstract: A power supply circuit is disclosed that includes a coil with first and second ends having supply voltage applied to the first end, a first switching element connected between the second end of the coil and ground, a second switching or diode element supplying current to a load after rectifying the current in accordance with voltage generated at the connection of the coil and the first switching element, a driver circuit switching at least the first switching element, a third switching element connected in series to the load, and a power supply stop circuit switching off the first element so as to stop supplying power to the load and switching off the third element so as to stop supplying the current to the load in accordance with an external signal.

Abstract: A power supply circuit is disclosed that includes a coil with first and second ends having supply voltage applied to the first end, a first switching element connected between the second end of the coil and ground, a second switching or diode element supplying current to a load after rectifying the current in accordance with voltage generated at the connection of the coil and the first switching element, a driver circuit switching at least the first switching element, a third switching element connected in series to the load, and a power supply stop circuit switching off the first element so as to stop supplying power to the load and switching off the third element so as to stop supplying the current to the load in accordance with an external signal.

Abstract: A voltage-current conversion circuit outputting a current corresponding to a difference between a first input voltage and a second input voltage, the voltage-current conversion circuit having a first current-mirror circuit supplied with the first input voltage as a power source and comprising at least one pair of transistors, a second current-mirror circuit supplied with the second input voltage as a power source and comprising at least one pair of transistors, a resistor connected between one of the pair of transistors of the first current-mirror circuit and one of the transistors of the second current-mirror circuit, and a third current-mirror circuit having a current source transistor supplying current to one of the pair of transistors of the first current-mirror circuit and another current source transistor supplying current to one of the pair of transistors of the second current-mirror circuit, a current output terminal being connected to one of the current source transistors.

Abstract: A constant-current generating circuit, a power-source voltage being applied thereto, generates a constant current. A voltage generating circuit element is connected between the constant-current generating circuit and a fixed voltage point, is supplied with the constant current which is generated by the constant-current generating circuit, and generates a constant voltage. A control circuit detects the current generated by the constant-current generating circuit, and, using the detected current, controls the constant-current generating circuit so that the current to be supplied to the voltage generating circuit element is the constant current.