Patent ID: 8531212
Filing Date: 2013-09-10
Classification: H03K

Abstract:
1. A drive circuit controllable for operating a driven switching device, the drive circuit comprising signal generator circuitry configured to be responsive to an external input signal for generating an operation signal, said operation signal specifying an on state and an off state of said driven switching device during an on-state command interval and an off-state command interval respectively, said command intervals defined by said external input signal, drive circuitry configured to supply a charging current to a control terminal of said driven switching device while said on state is specified by said operation signal, for setting a voltage of said control terminal to an on-state value thereof, and to enable passage of a discharge current from said control terminal while said off state is specified by said operation signal, for setting said control terminal voltage to an off-state value thereof, voltage detection circuitry configured to judge whether said control terminal voltage is above or below a predetermined threshold value, an off-holding switching device connected in an off-holding circuit path between said control terminal and a circuit point held at said off-state value of the control terminal voltage, said off-holding circuit path being separate from each of a charging circuit path and a discharge circuit path respectively utilized by said drive circuitry, and off-holding circuitry coupled to said signal generator circuitry and said voltage detection circuitry, configured to set said off-holding switching device in an off state while said on state of the driven switching device is specified by said operation signal or said control terminal voltage is judged to be above said threshold value, and to set said off-holding switching device in an on state while said off state of the driven switching device is specified by said operation signal and also said control terminal voltage is judged to be below said threshold value; wherein said control signal generator circuitry and said voltage detection circuitry are respectively configured whereby an interval between a first time point and a second time point is made less than a shortest possible duration of said on-state command interval, said first time point being a point at which said control terminal voltage changes from below to above said threshold value, and said second time point being a subsequent point at which said voltage detection circuitry judges that said control terminal voltage has risen from below to above said threshold value.