Display driving circuit with varying bias voltage and display device including the same
A display driving circuit includes a data driver that outputs a data signal to pixels, and a power supply that generates a driving voltage and a bias voltage. The driving voltage is provided to a first end of a transistor that generates a driving current based on the data signal provided to each of the pixels, and the bias voltage is provided at a second end of the transistor and varies based on a change in the driving voltage.
1 . A display driving circuit comprising:
a data driver configured to output a data signal to a plurality of pixels; and
a power supply configured to generates a driving voltage,
wherein the power supply comprises a bias voltage generator configured to receive a reference voltage and a feedback voltage corresponding to a change in the driving voltage, and to generate a bias voltage based on the reference voltage and the feedback voltage,
wherein the driving voltage is provided to a first end of a transistor that generates a driving current based on the data signal provided to each of the plurality of pixels, and
wherein the bias voltage is provided at a second end of the transistor.
2 . The display driving circuit of claim 1 , the bias voltage generator including:
a first voltage regulator configured to generate a first output voltage corresponding to the reference voltage;
a second voltage regulator configured to receive a first input voltage that varies according to the change in the driving voltage and generate a second output voltage corresponding to the first input voltage; and
a third voltage regulator configured to output the bias voltage corresponding to a divided voltage generated based on the first output voltage and the second output voltage.
3 . The display driving circuit of claim 2 , wherein the first voltage regulator includes:
a first voltage divider configured to generate a first feedback voltage corresponding to the first output voltage;
a first amplifier configured to compare the first feedback voltage and the reference voltage and output a first comparison signal corresponding to a comparison result from the first amplifier; and
a first transistor configured to generate the first output voltage based on the first comparison signal,
wherein the second voltage regulator includes:
a second voltage divider configured to generate a second feedback voltage corresponding to the second output voltage;
a second amplifier configured to compare the second feedback voltage and the first input voltage and output a second comparison signal corresponding to a comparison result from the second amplifier; and
a second transistor configured to generate the second output voltage based on the second comparison signal, and
wherein the third voltage regulator includes:
a third voltage divider configured to generate a third feedback voltage corresponding to the bias voltage;
a third amplifier configured to compare the third feedback voltage and the divided voltage and output a third comparison signal corresponding to a comparison result from the third amplifier; and
a third transistor configured to generate the bias voltage based on the third comparison signal.
4 . The display driving circuit of claim 3 , wherein the third voltage divider includes a plurality of variable resistors connected in series between a ground voltage and an output node that outputs the bias voltage.
5 . The display driving circuit of claim 2 , wherein the first voltage regulator, the second voltage regulator, and the third voltage regulator are low drop-out (LDO) regulators.
6 . The display driving circuit of claim 2 , further comprising a fourth voltage regulator configured to receive a second input voltage and output a third output voltage that shifts a range of a voltage level of the bias voltage based on the second input voltage.
7 . The display driving circuit of claim 6 , wherein the fourth voltage regulator includes:
a fourth voltage divider configured to generate a fourth feedback voltage corresponding to the third output voltage; and
a fourth amplifier configured to compare the fourth feedback voltage and the second input voltage and output a fourth comparison signal as the third output voltage.
8 . The display driving circuit of claim 7 , wherein the fourth voltage divider includes a plurality of variable resistors connected in series between a ground voltage and an output node that outputs the third output voltage.
9 . The display driving circuit of claim 6 , wherein the fourth voltage regulator is a low drop-out regulator.
10 . The display driving circuit of claim 2 , wherein the first input voltage is a maximum gamma voltage that generates a plurality of gamma voltages that determine a luminance of the plurality of pixels.
11 . The display driving circuit of claim 2 , wherein the bias voltage generator further comprises a multiplexer configured to receive the first output voltage and the bias voltage and selectively output the first output voltage or the bias voltage based on a control signal.
12 . A display device comprising:
a display panel that includes a plurality of pixels, each pixel including a light emitting element, a first transistor providing a driving current to the light emitting element based on a driving voltage applied to a first end thereof and a data voltage applied to a gate thereof, and a second transistor providing a bias voltage to a second end of the first transistor, the bias voltage varying a threshold voltage of the first transistor;
a timing controller configured to output a control signal to the display panel to display an image at a first frame frequency and a second frame frequency; and
a bias voltage generator configured to receive a reference voltage and a feedback voltage corresponding to a change in the driving voltage, and to generate the bias voltage based on the reference voltage and the feedback voltage.
13 . A display driving circuit comprising:
a timing controller configured to that output a control signal indicating a driving mode of a display panel including a plurality of pixels; and
a bias voltage generator configured to output a bias voltage that controls a luminance deviation between frames of the plurality of pixels,
wherein the bias voltage generator senses a change in a driving voltage of the plurality of pixels, receives a reference voltage independent of the driving voltage, and a first voltage varying according to the change in the driving voltage, generates a first output voltage with a specific level based on the reference voltage, generates a second output voltage based on the reference voltage and the first voltage, and outputs the first output voltage as the bias voltage when the control signal indicates a high frequency driving mode and outputs the second output voltage as the bias voltage when the control signal indicates a low frequency driving mode.
14 . The display driving circuit of claim 13 , wherein the bias voltage generator comprises:
a first voltage regulator configured to generate a third output voltage based on the reference voltage;
a second voltage regulator configured to generate a fourth output voltage based on the first voltage;
a multiplexer configured to receive a divided voltage generated based on the third output voltage and the fourth output voltage and the reference voltage and output the reference voltage or the divided voltage according to the control signal; and
a third voltage regulator configured to receive the reference voltage or the divided voltage from the multiplexer and output the bias voltage based on the received voltage.
15 . The display device of claim 12 , wherein the bias voltage generator provides the bias voltage with a constant voltage level based on a first control signal indicating the first frame frequency received from the timing controller, and provides the bias voltage with a voltage level varying based on the change in the driving voltage based on a second control signal indicating the second frame frequency received from the timing controller.
16 . The display device of claim 15 , wherein the bias voltage generator comprises:
a first voltage regulator configured to generate a first output voltage corresponding to the reference voltage;
a second voltage regulator configured to generate a second output voltage corresponding to a first voltage;
a third voltage regulator configured to receive a divided voltage generated based on the first output voltage and the second output voltage and generate a third output voltage corresponding to the divided voltage; and
a multiplexer configured to receive the first output voltage and the third output voltage, output the first output voltage based on the first control signal, and output the third output voltage based on the second control signal.
17 . The display device of claim 16 , further comprising a fourth voltage regulator configured to receive a second voltage and generate a fourth output voltage that corresponds to the second voltage and shifts a range of a voltage level of the third output voltage.
18 . The display device of claim 16 , wherein the first voltage is the driving voltage.
19 . The display device of claim 16 , wherein the first voltage is a maximum gamma voltage that generates a plurality of gamma voltages.
20 . The display device of claim 12 , wherein the first frame frequency is a high speed driving frequency, and the second frame frequency is a low speed driving frequency.