Abstract: The invention provides a switching circuit and a power converter having a built-in power source for a conduction control terminal even if they have a single-arm structure. In the switching circuit having a switching device and a conduction control terminal power source capacitor, a negative terminal of the capacitor is connected to a reference voltage terminal of a main power source and to the gate terminal selectively through a half-bridge circuit and a positive terminal of the capacitor is selectively connected to a positive terminal of the main power source and to a source terminal of the switching device through a half-bridge circuit. The capacitor is charged when the positive terminal is connected to the main power source and discharges when the negative terminal is connected to the gate terminal and the positive terminal is connected to the source terminal and applies voltage to the gate terminal of the switching device.

Abstract: An automatic circuit adjusting system comprises a circuit adjusting tool assembly. The circuit adjusting tool assembly is movable to adjust different orientations of circuit elements. The circuit adjusting tool assembly has a plurality of adjusting tools. The circuit adjusting tool assembly is controlled in its movement and selection of adjusting tools by means of a microprocessor based controller. The controller is so programmed as to shift the circuit adjusting tool assembly to different orientations of circuit elements on a printed circuit board in order according to a preset order. The controller is also preset to schedule selection of the desired one of the adjusting tools corresponding to the position of the circuit adjusting tool assembly. According to the preferred construction, the circuit adjusting tool assembly comprises a single common driving motor for driving a plurality of the adjusting tools.