Patent ID: 8513985

Claim:
A drive circuit for a semiconductor switching element serving as a drive-target switching element, comprising: a driving-usage power supply that supplies a drive voltage, which is applied between a control terminal and a potential reference terminal of the drive-target switching element; at least one capacitor that is charged by the driving-usage power supply; a connection changeover unit that is connected between the driving-usage power supply and the capacitor, and that switches a connection form between the driving-usage power supply and the capacitor; a resistor element that is connected to the control terminal of the drive-target switching element; a first switching element and a second switching element that are connected in series with each other, wherein a common connection point of the first switching element and the second switching element is connected to the resistor element, wherein a first free wheel diode is connected in parallel with the first switching element so that the first free wheel diode is reverse-connected with respect to polarity of the driving-usage power supply, wherein a second free wheel diode is connected in parallel with the second switching element so that the second free wheel diode is reverse-connected with respect to the polarity of the driving-usage power supply; a positive-side diode whose cathode is connected to an end of the first switching element; a negative-side diode whose anode is connected to an end of the second switching element; a backflow path formation element that is connected between the control terminal of the drive-target switching element and the driving-usage power supply, and that is brought into a conductive state when electric potential of the control terminal changes so as to exceed voltage of the driving-usage power supply; and a current conduction control circuit that controls the connection changeover unit, the first switching element and the second switching element to form (i) a first current conduction path in which the capacitor is charged, (ii) a second current conduction path in which the driving-usage power supply and the capacitor are connected in series with each other, and the control terminal of the drive-target switching element is charged via the resistor element, and (iii) a third current conduction path in which the control terminal of the drive-target switching element is connected to a negative terminal of the driving-usage power supply via the capacitor, and the control terminal of the drive-target switching element is discharged via the resistor element.