Drive circuit, operation state detection circuit, and display device
View Patent ↗According to an aspect of the invention, there is provided a drive circuit for driving a capacitive load. The drive circuit comprises an amplification circuit for amplifying an input signal and outputting the amplified signal to the capacitive load and an operation state detection circuit for detecting an operation state of output operation to the capacitive load in the amplification circuit. A variable resistor is connected between the amplification circuit and the capacitive load and changes the resistance value according to the detected operation state.
1. A display drive circuit for driving a capacitive load representing a pixel, comprising:
an amplification circuit for amplifying an input signal and outputting an amplified signal to the capacitive load;
an operation state detection circuit for detecting an operation state of an output operation to the capacitive load in the amplification circuit and outputting a detected operation state control signal; and
a variable resistor connected between the amplification circuit and the capacitive load and comprising a resistance value which changes according to the detected operation state control signal.
2. The drive circuit according to claim 1 , wherein the operation state detection circuit detects whether the operation state of the amplification circuit comprises a drive state in which the capacitive load is charged or discharged, or comprises a non-drive state in which the capacitive load is neither charged nor discharged.
3. The drive circuit according to claim 2 , wherein the amplification circuit comprises an output-stage transistor for outputting the output signal of the amplification circuit, and the operation state detection circuit refers to a control signal of the output-stage transistor and detects the operation state based on a reference signal.
4. The drive circuit according to claim 3 , wherein the operation state detection circuit detects the drive state when the reference signal is greater than a prescribed reference value, and detects the non-drive state when the reference signal is less than the prescribed reference value.
5. The drive circuit according to claim 3 , wherein the variable resistor decreases the resistance value when the detected operation state comprises the drive state, relative to the resistance value of when the detected operation state comprises the non-drive state.
6. The drive circuit according to claim 2 , wherein the amplification circuit comprises an output-stage transistor for putting out the amplified signal of the amplification circuit, and the operation state detection circuit refers to a control signal of the output-stage transistor and detects the operation state based on an electric current corresponding to a reference signal.
7. The drive circuit according to claim 6 , wherein the operation state detection circuit detects the drive state when the electric current corresponding to the reference signal is greater than a prescribed reference value, and detects the non-drive state when the electric current corresponding to the reference signal is less than the prescribed reference value.
8. The drive circuit according to claim 6 , wherein the variable resistor decreases the resistance value when the detected operation state comprises the drive state, relative to the resistance value of when the detected operation state comprises the non-drive state.
9. The drive circuit according to claim 2 , wherein the variable resistor decreases the resistance value when the detected operation state comprises the drive state, relative to the resistance value of when the detected operation state comprises the non-drive state.
10. The drive circuit according to claim 2 , wherein the variable resistor increases the resistance value when the detected operation state comprises the non-drive state, relative to the resistance value of when the detected operation state comprises the drive state.
11. The drive circuit according to claim 1 , wherein the amplification circuit comprises an output-stage transistor for outputting an output signal of the amplification circuit, and the operation state detection circuit refers to a control signal of the output-stage transistor and detects the operation state based on a reference signal.
12. The drive circuit according to claim 11 , wherein the reference signal comprises a current input to the amplification circuit.
13. The drive circuit according to claim 1 , wherein the amplification circuit comprises an output-stage transistor for putting out the amplified signal of the amplification circuit, and the operation state detection circuit refers to a control signal of the output-stage transistor and detects the operation state based on an electric current corresponding to a reference signal.
14. The drive circuit according to claim 1 , wherein the amplification circuit comprises an output-stage transistor for putting out the amplified signal of the amplification circuit, and the operation state detection circuit refers to the output signal of the output-stage transistor and detects the operation state based on a reference signal.
15. The drive circuit according to claim 1 , wherein the amplification circuit comprises an output-stage transistor for putting out the amplified signal of the amplification circuit, and the operation state detection circuit comprises:
an output reference transistor for receiving a control signal for the output-stage transistor;
a comparator for comparing a current value of the output reference transistor and a prescribed reference value; and
a resistance control output circuit for outputting a resistance control signal for controlling the resistance value of the variable resistor based on the output of the comparator.
16. The drive circuit according to claim 15 , wherein the amplification circuit further comprises:
a differential amplifier in a stage prior to the output-stage transistor,
wherein an output of the output-stage transistor is fed back to the differential amplifier.
17. The drive circuit according to claim 15 , wherein the variable resistor comprises a plurality of transistors comprising different resistance values, and switches ON/OFF a transistor selected from the plurality of transistors and changes the resistance value based on the resistance control signal from the operation state detection circuit.
18. The drive circuit according to claim 1 , wherein the amplification circuit comprises a first output-stage transistor and a second output-stage transistor in a push-pull circuit outputting the amplified signal of the amplification circuit, and the operation state detection circuit comprises:
a first output reference transistor for receiving a control signal for the first output-stage transistor;
a first comparator for comparing a current value of the first output reference transistor with a first reference value;
a second output reference transistor for receiving a control signal for the second output-stage transistor;
a second comparator for comparing a current value of the second output reference transistor with a second reference value; and
a resistance control output circuit for outputting a resistance control signal for controlling the resistance value of the variable resistor based on an output of the first comparator and an output of the second comparator.
19. The drive circuit according to claim 18 , wherein the amplification circuit further comprises:
a first differential amplifier in a stage prior to the first output-stage transistor; and
a second differential amplifier in a stage prior to the second output-stage transistor,
wherein the outputs of the first and second output-stage transistors are fed back to the first and second differential amplifiers.
20. The drive circuit according to claim 18 , wherein the variable resistor comprises a plurality of transistors comprising different resistance values, and switches ON/OFF a transistor selected from the plurality of transistors and changes the resistance value based on the resistance control signal from the operation state detection circuit.
21. A display device comprising:
a display panel comprising a plurality of pixels and a plurality of lines for transmitting a plurality of signals to the plurality of pixels; and
a plurality of drive circuits connected to the plurality of lines for outputting a plurality of signals to the plurality of pixels,
wherein each of the plurality of drive circuits comprises:
an amplification circuit for amplifying an input signal and outputting an amplified signal to a pixel of the plurality of pixels via a line of the plurality of lines;
an operation state detection circuit for detecting an operation state of an output operation of the amplification circuit to a capacitive load of the pixel and outputting a detected operation state control signal; and
a variable resistor connected between the amplification circuit and the pixel and comprising a resistance value which changes according to the detected operation state control signal.