TWI415086B - Source driver and driving method thereof - Google Patents

Abstract

A source driver and a driving method thereof are provided. The source driver is adapted to a display panel. The source driver includes an output buffer and a regulating unit. The output buffer has an input terminal and an output terminal. The input terminal of the output buffer receives a pixel signal. The output terminal of the output buffer is coupled to the display panel for outputting an output signal. The regulating unit is coupled to the output terminal of the output buffer, for providing a charging current or a discharging current to the output terminal of the output buffer according to the polarity of the pixel signal. Thereby, the slew rate of the output signal is increased.

Description

Source driver and driving method thereof

The present invention relates to a driving technique for a display, and more particularly to a source driver and a method of driving the same.

In recent years, liquid crystal displays (LCDs) have become the mainstream in the market due to their low power loss, zero radiation and high space utilization. The source driver is an important component in the liquid crystal display, which converts the digital data signal into an analog signal for displaying a picture, and outputs an analog signal to each pixel on the display panel.

In general, an operational amplifier (OP) is configured at the output stage of the source driver to improve the drive capability of the source driver. Operational amplifiers have many specifications, such as unity-gain frequency, phase margin, power consumption, common-mode rejection ratio, and power-supply rejection. Ratio), input common mode range, slew rate, and noise, etc., where slew rate is the rate of change of the output voltage variable, often defined as volts per second (or microseconds).

It is worth noting that the slew rate directly affects the picture quality of the liquid crystal display. The higher the slew rate, the shorter the time required for the source driver to provide the correct analog signal to the display panel. Conversely, the lower the slew rate, the longer the source driver will provide the correct analog signal to the display panel, which may result in image sticking or flicker.

The invention provides a source driver for improving the picture quality displayed by the display panel.

The invention provides a driving method of a source driver, which can provide a charging current or a discharging current to an output terminal, thereby increasing the slew rate of the pixel signal outputted by the source driver.

The invention provides a source driver suitable for use in a display panel. The source driver includes an output buffer and an adjustment unit. The output buffer has an input and an output. The input of the output buffer receives the pixel signal. The output of the output buffer is coupled to the display panel to output an output signal. The adjusting unit is coupled to the output end of the output buffer, and can provide a charging current or a discharging current to the output end of the output buffer according to the polarity of the pixel signal, thereby increasing the slew rate of the pixel signal.

In the above-mentioned source driver, in an embodiment of the invention, the adjustment unit comprises a multiplexer, a first source follower, a first switch, a second source follower and a second switch. The multiplexer can receive the indication signal and generate the first control signal and the second control signal according to the polarity of the indication signal and the pixel signal. The first end of the first source follower is coupled to the first voltage, and the first source is coupled to the control end of the coupler to receive the pixel signal. The first switch has a first end and a second end. The first end of the first switch is coupled to the second end of the first source follower, and the second end of the first switch is coupled to the output end of the output buffer. The first switch can determine whether to conduct according to the first control signal, so that the charging current is supplied to the display panel by the first source follower. The first end of the second source follower is coupled to the second voltage, and the second source is coupled to the control end of the coupler to receive the pixel signal. The first end of the second switch is coupled to the second end of the second source follower, and the second end of the second switch is coupled to the output end of the output buffer. The second switch can determine whether to conduct according to the second control signal, so that the discharge current is supplied to the display panel by the second source follower.

In the above-described source driver, in an embodiment of the invention, the output buffer includes an operational amplifier. The first input of the operational amplifier serves as an input of the output buffer, the first output of the operational amplifier is coupled to the second input of the operational amplifier, and the first output of the operational amplifier is used as the output of the output buffer.

Viewed from another perspective, the present invention provides a method of driving a source driver. The source driver includes an output buffer, wherein the input end of the output buffer receives the pixel signal, and the output end of the output buffer is coupled to the display panel to output an output signal. In the driving method, the signal is enabled in accordance with the scan driving signal associated with the scanning line. When the indication signal is enabled, a control signal is generated based on the polarity of the pixel signal. Then, according to the control signal, a charging current or a discharging current is selectively supplied to the output end of the output buffer to increase the slew rate of the pixel signal.

In the above driving method, in an embodiment of the invention, when the scan driving signal is enabled, the indication signal is enabled, and when the scanning driving signal is disabled, the indication signal is disabled.

In an embodiment of the present invention, when the scan driving signal is disabled, the enable command signal is enabled, and the scan signal is disabled before the scan drive signal is enabled.

The driving method described above, in an embodiment of the present invention, when the picture is When the polarity of the number is positive, a charging current is supplied to the output of the output buffer. When the polarity of the pixel signal is negative, a discharge current is supplied to the output of the output buffer. In another embodiment, the amount of current of the charging current and the discharging current can be controlled by the pixel signal.

Based on the above, the present invention provides a charging current or a discharging current to the output end of the output buffer according to the polarity of the pixel signal through the adjusting unit, thereby increasing the slew rate of the pixel signal outputted by the output buffer.

The above described features and advantages of the invention will be apparent from the following description.

In the prior art, the slew rate of the pixel signal is too low, and it is easy to cause image sticking or flickering of the screen displayed on the display panel. In view of this, embodiments of the present invention configure an adjustment unit in the source driver. When the polarity of the pixel signal changes, the adjusting unit can provide a charging current or a discharging current to the output end of the output buffer according to the polarity change of the pixel signal, thereby increasing the slew rate of the pixel signal outputted by the output buffer. In this way, the picture quality displayed on the display panel can be effectively improved. The embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which FIG.

1 is a circuit diagram of a source driver in accordance with an embodiment of the present invention. Referring to FIG. 1 , the source driver 100 is adapted to drive a display panel 120 , such as a liquid crystal display panel or a liquid crystal on silicon (LCoS). The source driver 100 includes an output buffer 110 and an adjustment unit 130. The output buffer 110 is coupled to the adjustment unit 130 and the display The panel 120, wherein the display panel 120 is represented by an equivalent circuit composed of a resistor and a capacitor, for example, a resistance of a line resistance or a pixel switch, and the capacitor is, for example, a storage capacitor or a pixel capacitor. In the embodiment, the output buffer 110 is implemented by, for example, a negative feedback type operational amplifier OP1. The input terminal receives the pixel signal Vin and provides an output signal Vout to the display panel 120 via its output terminal to drive the display. Panel 120.

The adjustment unit 130 is coupled to the display panel 120, and includes a multiplexer 131, source followers 132-133 and switches 134-135, wherein the source followers 132-133 are implemented by transistors M1 and M2, respectively. Switches 134-135 are implemented by transistors M3 and M4, respectively. The source followers 132-133 have the advantages of high input impedance and low output impedance, can be used for impedance matching, and their output signals change with the input signal. The source follower 132 is coupled between the voltage VDDA and the switch 134, and is controlled by the pixel signal to provide a charging current. The switch 134 is coupled between the source follower 132 and the output of the output buffer 110. When the switch 134 is turned on, the source follower 132 provides a charging current to the output of the output buffer 110 via the turned-on switch 134.

Similarly, the source follower 133 is coupled between the voltage VSSA and the switch 135, and is controlled by the pixel signal to provide a discharge current. The switch 135 is coupled between the source follower 133 and the output of the output buffer 110. When the switch 135 is turned on, the source follower 133 provides a discharge current to the output of the output buffer 110 via the turned-on switch 135. The multiplexer 131 receives the indication signal HDR and the polarity signal POL, and generates control signals HDR_P and HDR_N, wherein the indication signal is the drive adjustment unit 130. The signal is made, and the polarity signal POL is the polarity of the pixel signal Vin. In this embodiment, the indication signal HDR is related to the scan driving signal of the scan line.

The following is further described in conjunction with the drawings. 2 is a timing diagram of an indication signal and a scan driving signal in the source driver of FIG. 1 according to an embodiment of the invention. 3 is a flow chart of a method of driving a source driver in accordance with an embodiment of the present invention. Referring to FIG. 1 , FIG. 2 and FIG. 3 , when the scan driving signal TP1 is enabled, the source driver transmits the pixel signal Vin to the pixels on the display panel via the data line. In order to increase the slew rate of the pixel signal outputted by the output buffer 110, when the scan driving signal TP1 is enabled, the indication signal HDR is enabled to drive the operation of the adjusting unit 130 (step S301).

At this time, the multiplexer 131 generates the control signals HDR_P and HDR_N according to the polarity signal POL indicating the polarity of the pixel signal (step S302). In this embodiment, since the transistors M3 and M4 are P-type transistors and N-type transistors, respectively, the control signals HDR_P and HDR_N are in-phase signals to control the conduction of the switches 134 and 135. Those skilled in the art can also implement switches 134-135 by other components, and design control signals HDR_P and HDR_N accordingly, so that switches 134-135 are turned on according to the polarity of the pixel signal. Thereby, the adjusting unit 130 selectively supplies a charging current or a discharging current to the output end of the output buffer 110 according to the actuation of the control signals HDR_P and HDR_N (step S303) to increase the pixel signal output by the output buffer 110. Swing rate.

For example, when the polarity signal POL indicates that the pixel signal Vin is from the negative pole When the polarity is changed to the positive polarity, the switch 134 is turned on by the control signal HDR_P, and the switch 135 is controlled by the control signal HDR_N without being turned on. At this time, through the turned-on switch 134, the source follower 132 supplies a charging current to the output of the output buffer 110 to assist in boosting the voltage of the output signal Vout. On the other hand, when the polarity signal POL indicates that the pixel signal Vin is changed from the positive polarity to the negative polarity, the switch 134 is controlled by the control signal HDR_P without being turned on, and the switch 135 is turned on by the control signal HDR_N. At this time, the source follower 133 supplies a discharge current to the output terminal of the output buffer 110 through the on-switch 135 to assist in reducing the voltage of the output signal Vout. In this way, the slew rate of the pixel signal output by the output buffer 110 can be effectively improved. In addition, referring to FIG. 2, after the scan driving signal TP1 is disabled, the indication signal HDR is disabled to disable the operation of the adjusting unit 130.

In the embodiment of FIG. 1, since the positive polarity pixel signal and the negative polarity pixel signal are generally high voltage and low voltage, respectively, in order to avoid the source follower 132 and 133 realized by the transistor, the matrix effect is limited. The current that can be supplied is such that the transistor M1 of the source follower 132 is an N-type transistor, and the transistor M2 of the source follower 133 is a P-type transistor.

It is worth mentioning that although the source driver and its driving method have been drawn out in a possible form in the above embodiments, those skilled in the art should know that each manufacturer has a source driver and a method thereof. The design is different, so the application of the invention is not limited to this possible type. In other words, as long as the charging current or the discharging current is supplied to the output of the output buffer according to the polarity of the pixel signal, it is already in conformity. The spirit of the invention lies.

Although the above embodiment uses the timing of the scan driving signal and the indication signal shown in FIG. 2 as an example to describe the operation of the adjustment unit 130, those skilled in the art can change the timing of the scan driving signal and the indication signal according to the requirements. The invention is not limited to this. 4 and FIG. 5 are another timing diagram of the indication signal and the scan driving signal in the source driver of FIG. 1 according to an embodiment of the invention. Referring to FIG. 4, the timing shown in FIG. 4 is different from that in FIG. 2 in that the indication signal HDR is enabled and disabled along with the timing of the scan driving signal.

Referring to FIG. 5, when the scan driving signal TP1 is disabled, the indication signal HDR is enabled to drive the adjustment unit 130. At this time, the adjustment unit 130 can adjust the slew rate of the pixel signal outputted by the output buffer in advance. After sufficient time (which can be controlled by the pulse width of the indication signal HDR) to increase the slew rate of the pixel signal outputted by the output buffer, the indication signal HDR is disabled before the scan driving signal TP1 is enabled to turn off the adjustment. The operation of unit 130. When the scan driving signal TP1 is enabled, the pixel signal whose slew rate is adjusted can be output from the output buffer and transmitted to the pixels on the panel.

In summary, the above embodiment provides a charging current or a discharging current to the output end of the output buffer according to the polarity of the pixel signal to increase the slew rate of the pixel signal outputted by the output buffer. In addition, in the above embodiment, the charging current and the discharging current are adjusted according to the change of the pixel signal, so that the voltage of the output end of the output buffer is appropriately increased or decreased according to the pixel signal.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and those skilled in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

110‧‧‧Output buffer

120‧‧‧ display panel

130‧‧‧Adjustment unit

131‧‧‧Multiplexer

132, 133‧‧‧ source follower

134, 135‧‧ ‧ switch

OP‧‧‧Operational Amplifier

M1~M4‧‧‧O crystal

VSSA, VDDA‧‧‧ voltage

Vin‧‧‧ Picture signal

Vout‧‧‧ output signal

HDR‧‧‧ indication signal

POL‧‧‧polar signal

TP1‧‧‧ scan drive signal

HDR_P, HDR_N‧‧‧ control signal

S301~S303‧‧‧Steps of driving method of source driver

1 is a circuit diagram of a source driver in accordance with an embodiment of the present invention.

2 is a timing diagram of an indication signal and a scan driving signal in the source driver of FIG. 1 according to an embodiment of the invention.

3 is a flow chart of a method of driving a source driver in accordance with an embodiment of the present invention.

4 and FIG. 5 are timing diagrams of the indication signal and the scan driving signal in the source driver of FIG. 1 according to an embodiment of the invention.

100‧‧‧Source Driver

110‧‧‧Output buffer

120‧‧‧ display panel

130‧‧‧Adjustment unit

131‧‧‧Multiplexer

132~133‧‧‧Source follower

134~135‧‧‧ switch

HDR‧‧‧ indication signal

POL‧‧‧polar signal

HDR_P, HDR_N‧‧‧ control signal

Vin‧‧‧ Picture signal

Vout‧‧‧ output signal

VDDA, VSSA‧‧‧ voltage

Claims (12)

A source driver is applicable to a display panel, comprising: an output buffer, wherein an input terminal receives a pixel signal, and an output end of the display terminal is coupled to the display panel to output an output signal; and an adjustment unit coupled to the source The output end of the output buffer provides a charging current or a discharging current to the output end of the output buffer according to the polarity of the pixel signal, thereby increasing a slew rate of the output signal, wherein the adjusting unit includes: The device receives an indication signal and generates a first control signal and a second control signal according to the polarity of the indication signal and the pixel signal; a first source follower coupled to the first end of the first source a voltage, and the control terminal receives the pixel signal; a first switch having a first end coupled to the second end of the first source follower and a second end coupled to the output of the output buffer End, wherein the first switch determines whether to conduct according to the first control signal, so that the charging current is supplied to the display panel by the first source follower; a second source follower, the first end thereof Coupling one a voltage, and the control terminal receives the pixel signal; and a second switch having a first end coupled to the second end of the second source follower and a second end coupled to the output of the output buffer The second switch determines whether to conduct according to the second control signal, so that the discharge current is supplied to the display panel by the second source follower. The source driver according to claim 1, wherein the source driver The first source follower includes: a transistor having a gate coupled to the input end of the output buffer, the first source/drain as the first end of the first source follower, and A second source/drain is used as the second end of the first source follower. The source driver of claim 1, wherein the second source follower includes: a transistor having a gate coupled to the input end of the output buffer, the first source/drain As the first end of the second source follower, and its second source/drain as the second end of the second source follower. The source driver of claim 1, wherein the first switch comprises: a transistor, the gate receiving the first control signal, and the first source/drain as the first switch One end and its second source/drain as the second end of the first switch. The source driver of claim 1, wherein the second switch comprises: a transistor, the gate receiving the second control signal, and the first source/drain as the second switch One end and its second source/drain as the second end of the second switch. The source driver of claim 1, wherein the output buffer comprises: an operational amplifier having a first input terminal as an input terminal of the output buffer, and a first output terminal coupled to the first output terminal thereof A second input, wherein the first output of the operational amplifier serves as an output of the output buffer. The source driver of claim 1, wherein the display panel is a germanium-based liquid crystal panel. The source driver of claim 1, wherein the display panel is a liquid crystal display panel. A source driver driving method, wherein the source driver includes an output buffer, the input end of the output buffer receives a pixel signal, and the output end of the output buffer is coupled to a display panel to output an output signal. The driving method includes: enabling an indication signal according to a scan driving signal related to a scan line; when the indication signal is enabled, generating a control signal according to the polarity of the pixel signal; and selecting according to the control signal Optionally providing a charging current or a discharging current to the output of the output buffer to increase a slew rate of the output signal, wherein the indication signal is enabled when the scan driving signal is enabled or disabled. If the indication signal is enabled when the scan driving signal is enabled, the indication signal is disabled when the scanning driving signal is disabled, wherein the indication signal is disabled when the scanning driving signal is disabled. If enabled, the indication signal is disabled before the scan drive signal is enabled. The driving method of claim 9, wherein when the polarity of the pixel signal is positive, the charging current is supplied to an output of the output buffer, and when the polarity of the pixel signal is Negative polarity The discharge current is supplied to the output of the output buffer. The driving method of claim 9, wherein the charging current and the current amount of the discharging current are controlled by the pixel signal. The driving method of claim 9, wherein the charging current and the discharging current are respectively provided by a first source follower and a second source follower.