Patent ID: 8952730
Filing Date: 2015-02-10
Classification: H03K

Abstract:
1. A driver circuit including a first transistor in which one end of a pair of input-output terminals is connected to a first power-supply voltage, and a second transistor in which one end of a pair of input-output terminals is connected to a second power-supply voltage that is lower than the first power-supply voltage, the first transistor and the second transistor being connected in series, the driver circuit outputting a voltage of an intermediate node between the first transistor and the second transistor, the driver circuit comprising: a first control circuit that includes a high-voltage-side power-supply terminal and a low-voltage-side power-supply terminal, and that outputs a first control signal for controlling on/off of the first transistor to a control terminal of the first transistor based upon an input signal; a second control circuit that has a high-voltage-side power-supply terminal and a low-voltage-side power-supply terminal, and that outputs a second control signal for controlling on/off of the second transistor to a control terminal of the second transistor based upon an input signal; a switching element; and a capacitor that generates a power-supply voltage that is to be supplied to the first control circuit, wherein one end of the capacitor is connected through the switching element to a third power-supply voltage lower than the second power-supply voltage via the switching element, and the other end of the capacitor is connected to the other end of the input-output terminals of the first transistor, the voltage on one end of the capacitor is supplied to the low-voltage-side power-supply terminal of the first control circuit, the third power-supply voltage is supplied to the low-voltage-side power-supply terminal of the second control circuit, the first control circuit outputs the voltage supplied to the low-voltage-side power-supply terminal of the first control circuit as the first control signal, when turning off the first transistor, the second control circuit outputs the voltage supplied to the low-voltage-side power-supply terminal of the second control circuit as the second control signal, when turning off the second transistor, and the switching element is controlled to be in on state when the second transistor is in on state; and wherein the first transistor is a normally-on n-channel FET using a wide-gap semiconductor, and the high-voltage-side power-supply terminal of the first control circuit is connected to the other end of the input-output terminals of the first transistor.