JP2009284370A5 - - Google Patents

Claims (10)

A gate driving device for driving a gate voltage of an output transistor,
A voltage detection circuit for detecting a level relationship between the gate voltage and a predetermined threshold voltage, and a switch for conducting / cutting off between the gate of the output transistor and a power supply voltage application terminal based on a detection result of the voltage detection circuit And a gate driving device characterized by comprising:   The voltage detection circuit includes: a threshold voltage generation unit that generates the threshold voltage; a voltage comparison unit that compares the gate voltage with the threshold voltage; and a control signal for the switch based on a comparison result of the voltage comparison unit. The gate drive device according to claim 1, further comprising: an output unit that generates the output unit. The voltage comparison unit, the gate voltage and the threshold voltage to sign addition to the transistor pair forming a current mirror circuit, and sends an output current of the current mirror circuit to the output unit, the output unit, the output The gate driving device according to claim 2, wherein a control signal for the switch is generated by converting a current into a voltage.   4. The gate driving device according to claim 3, wherein the voltage comparison unit applies the gate voltage and the threshold voltage to each source of the transistor pair.   The voltage detection circuit includes a gate voltage cutoff unit that conducts / cuts off between a gate of the output transistor and a gate voltage input terminal of the voltage comparison unit according to a logic level of the gate voltage. The gate driving device according to claim 2.   6. The gate driving apparatus of claim 5, wherein the gate voltage cutoff unit divides the gate voltage and supplies the divided voltage to the voltage comparison unit.   The threshold voltage generation unit generates the threshold voltage lower than the power supply voltage by a predetermined value, and the output unit conducts the switch when the gate voltage becomes equal to or higher than the threshold voltage. The gate driving device according to claim 6.   The gate voltage blocking unit includes a first transistor having a source connected to the application terminal of the power supply voltage via a resistor, a drain connected to the application terminal of the gate, and a gate connected to an application terminal of the control signal; A second transistor having a source connected to the power supply voltage application terminal, a drain connected to the gate voltage input terminal of the voltage comparison unit, and a gate connected to the source of the first transistor; 8. A third transistor connected to a gate voltage input terminal, a drain connected to the gate voltage application terminal, and a gate connected to the control signal application terminal. The gate drive device described in 1.   The threshold voltage generation unit generates the threshold voltage higher than the source voltage by a predetermined value, and the output unit conducts the switch when the gate voltage becomes equal to or lower than the threshold voltage. The gate driving device according to claim 6.   The gate voltage cutoff unit includes a first transistor having a source connected to the application terminal of the source voltage via a resistor, a drain connected to the application terminal of the gate, and a gate connected to the application terminal of the control signal; A second transistor having a source connected to the source voltage application terminal, a drain connected to the gate voltage input terminal of the voltage comparison unit, and a gate connected to the source of the first transistor; and a source of the voltage comparison unit 10. A third transistor connected to a gate voltage input terminal, having a drain connected to the gate voltage application terminal, and a gate connected to the control signal application terminal. The gate drive device described in 1.