Patent ID: 7852137
Filing Date: 2010-12-14
Classification: H01L,H03K

Abstract:
1. A switching device suitable for use as a bidirectional switch for on-off control of electric circuits, the switching device comprising: (a) a first and a second main terminal to be connected to an electric circuit to be placed under on-off switching control of the device; (b) a normally-on main semiconductor switch comprising a main semiconductor region, a first and a second main electrode on the main semiconductor region, and gate means for controlling current flow between the first and the second main electrodes through the main semiconductor region, the main semiconductor switch having a prescribed threshold voltage; (c) a normally-off first auxiliary semiconductor switch comprising a first main electrode connected to the first main terminal, a second main electrode connected to the first main electrode of the main semiconductor switch, and control means for controlling current flow between the first and the second main electrodes of the first auxiliary semiconductor switch, the first auxiliary semiconductor switch being capable of withstanding voltages not less than the absolute value of the threshold voltage of the main semiconductor switch; (d) a normally-off second auxiliary semiconductor switch comprising a first main electrode connected to the second main terminal, a second main electrode connected to the second main electrode of the main semiconductor switch, and control means for controlling current flow between the first and the second main electrodes of the second auxiliary semiconductor switch, the second auxiliary semiconductor switch being capable of withstanding voltages not less than the absolute value of the threshold voltage of the main semiconductor switch; (e) a first diode connected in parallel with the first auxiliary semiconductor switch, the first diode being oriented for conduction in response to a voltage applied in a first prescribed direction between the first and the second main terminals; (f) a second diode connected in parallel with the second auxiliary semiconductor switch, the second diode being oriented for conduction in response to a voltage applied in a second prescribed direction, opposite to the first prescribed direction, between the first and the second main terminals; (g) a first gate potential switch connected between the first main terminal and the gate means of the main semiconductor switch for determination of a potential for the gate means, the first gate potential switch permitting conduction between the first main terminal and the gate means of the main semiconductor switch in response to a voltage applied in the second prescribed direction between the first and the second main terminal, the first gate potential switch being capable of withstanding higher voltages than the first and the second diode; (h) a second gate potential switch connected between the second main terminal and the gate means of the main semiconductor switch for determination of a potential for the gate means, the second gate potential switch permitting conduction between the second main terminal and the gate means of the main semiconductor switch in response to a voltage applied in the first prescribed direction between the first and the second main terminal, the second gate potential switch being capable of withstanding higher voltages than withstand voltages of the first and the second diode; (i) a first switch control circuit connected between the first main electrode and control means of the first auxiliary semiconductor switch for on-off control of the first auxiliary semiconductor switch; and (j) a second switch control circuit connected between the first main electrode and control means of the second auxiliary semiconductor switch for on-off control of the second auxiliary semiconductor switch.