Capacitive load drive circuit and display device including the same
First Claim
1. A capacitive load drive circuit that drives a capacitive load based on an input voltage, comprising:
- a voltage comparison unit that compares the input voltage inputted from an input terminal and an output voltage outputted from an output terminal to output a comparison result voltage in accordance with a comparison result;
a drive control unit that outputs a charge control voltage and a discharge control voltage that are set to initial levels respectively in a first period, and change in accordance with the comparison result voltage in a second period; and
a push-pull output unit including a charge circuit that charges the capacitive load connected to the output terminal, based on the charge control voltage, and a discharge circuit that discharges the capacitive load, based on the discharge control voltage, whereinthe drive control unit includes;
a charge-side amplifier circuit that outputs the charge control voltage to the charge circuit;
a discharge-side amplifier circuit that outputs the discharge control voltage to the discharge circuit;
a charge-side capacitive element to capacitively-couple the output of the voltage comparison unit and an input of the charge-side amplifier circuit;
a discharge-side capacitive element to capacitively-couple the output of the voltage comparison unit and an input of the discharge-side amplifier circuit;
a charge-side setup switch that becomes in an ON state in the first period to supply an OFF voltage to the input of the charge-side amplifier circuit; and
a discharge-side setup switch that becomes in an ON state in the first period to supply an OFF voltage to the input of the discharge-side amplifier circuit, whereinthe drive control unit selectively operates the charge circuit and the discharge circuit so that the output voltage becomes equal to the input voltage, and whereinin the first period, the drive control unit sets the charge control voltage and the discharge control voltage to levels at which the charge circuit and the discharge circuit do not operate, respectively, and in the second period, based on the comparison result voltage, the drive control unit sets the charge control voltage to a level at which the charge circuit operates when the output voltage is lower than the input voltage, and sets the discharge control voltage to a level at which the discharge circuit operates when the output voltage is higher than the input voltage.
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Accused Products
Abstract
A buffer circuit drives a capacitive load based on a voltage Vin. In a setup period, switches are in an ON state, and in a drive period, a switch is in an ON state. A voltage comparison unit compares the voltage Vin in the setup period and a voltage Vout in a drive period to output a comparison result voltage. A push-pull output unit includes a TFT for charge and a TFT for discharge. A drive control unit controls the TFTs to be in an OFF state in the setup period, and in the drive period, selectively controls the TFTs to be in an ON state in accordance with the comparison result voltage. If Vout<Vin, the comparison result voltage rises, the TFT becomes in an ON state, a voltage at a node falls, the TFT becomes in the ON state, and the voltage Vout rises. Thus, there is a provided a small-sized capacitive load drive circuit with low power consumption and robust against process variation.
18 Citations
6 Claims
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1. A capacitive load drive circuit that drives a capacitive load based on an input voltage, comprising:
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a voltage comparison unit that compares the input voltage inputted from an input terminal and an output voltage outputted from an output terminal to output a comparison result voltage in accordance with a comparison result; a drive control unit that outputs a charge control voltage and a discharge control voltage that are set to initial levels respectively in a first period, and change in accordance with the comparison result voltage in a second period; and a push-pull output unit including a charge circuit that charges the capacitive load connected to the output terminal, based on the charge control voltage, and a discharge circuit that discharges the capacitive load, based on the discharge control voltage, wherein the drive control unit includes; a charge-side amplifier circuit that outputs the charge control voltage to the charge circuit; a discharge-side amplifier circuit that outputs the discharge control voltage to the discharge circuit; a charge-side capacitive element to capacitively-couple the output of the voltage comparison unit and an input of the charge-side amplifier circuit; a discharge-side capacitive element to capacitively-couple the output of the voltage comparison unit and an input of the discharge-side amplifier circuit; a charge-side setup switch that becomes in an ON state in the first period to supply an OFF voltage to the input of the charge-side amplifier circuit; and a discharge-side setup switch that becomes in an ON state in the first period to supply an OFF voltage to the input of the discharge-side amplifier circuit, wherein the drive control unit selectively operates the charge circuit and the discharge circuit so that the output voltage becomes equal to the input voltage, and wherein in the first period, the drive control unit sets the charge control voltage and the discharge control voltage to levels at which the charge circuit and the discharge circuit do not operate, respectively, and in the second period, based on the comparison result voltage, the drive control unit sets the charge control voltage to a level at which the charge circuit operates when the output voltage is lower than the input voltage, and sets the discharge control voltage to a level at which the discharge circuit operates when the output voltage is higher than the input voltage. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification