Patent ID: 7206179

Claim:
A control device of switching devices, comprising: driving devices configured to performing drive and control of said switching devices; a snubber circuit configured to suppress a surge voltage generated during a switching operation of said switching devices; a voltage detection device configured to detect a voltage between main electrodes of said switching devices; a detected voltage monitoring device configured to monitor the voltage detected by said voltage detection device to detect said surge voltage; and control state changing devices configured to change a control state of said switching devices based on instructions provided from said detected voltage monitoring device, wherein said detected voltage monitoring device has first and second predetermined values to be compared with said surge voltage, and suppresses said surge voltage by: a provision of instructions to said control state changing devices so that a transition of the control state of said switching devices takes place from a normal control state to a first control state when said surge voltage exceeds said first predetermined value, and a provision of instructions to said control state changing devices so that a transition of the control state of said switching devices takes place from said first control state to a second control state when said surge voltage exceeds said second predetermined value while said switching devices are in said first control state.