Patent ID: 7221208
Filing Date: 2007-05-22
Classification: H03K

Abstract:
1. A switching circuit having a switching element, comprising: a current detecting circuit having a main switch composed of MOSFET having an on-resistance at on-voltage, wherein a gate terminal thereof is connected to a driving circuit, and further one of a drain terminal and a source terminal thereof is connected to a fixed potential and the other terminal is connected to a load circuit; a first resistance element having higher resistance value than the on-resistance of the main switch; a subsidiary switch composed of MOSFET, the source terminal of which is connected to the first resistance element, an amplifier that amplifies comparatively a first resistance element voltage generated in the first resistance element and the on-voltage of the main switch and generates an output to a subsidiary switch gate terminal of the subsidiary switch; a second resistance element connected to a drain terminal of the subsidiary switch, in which a second resistance element voltage is generated according to an on-current of the main switch; and a third switch, connected between the first resistance element and the subsidiary switch in which a third switch gate terminal of the third switch is connected to the driving circuit so that a gate signal of the third switch is synchronized with that of the main switch.