TWI415084B - Source drive and method for reducing the image noise caused by the source driver - Google Patents

Abstract

A source drive, powered by a power supply, includes the channels, the output ends, the multiplexer, the charge-sharing switch and the voltage detectors. The multiplexer controls the link between the channels and the output ends, and the charge-sharing switch connects to the output ends. The first provided voltage of the power supply were detected by the voltage detector. If the provided voltage is insufficient, the switch turns on, and the connections between the channels and the output ends are disconnected by the multiplexer.

Description

Source driver and source driver noise suppression method

The present invention relates to a device for a source driver, and more particularly to noise suppression for a source driver.

In recent years, with the advancement of optical technology and semiconductor technology, liquid crystal display (LCD) has been widely used in electronic products. The liquid crystal display has the advantages of high image quality, small size, light weight, low voltage driving and low power consumption. Therefore, it has been widely used in portable computers, personal digital assistants, and color televisions, and has become the mainstream of displays.

Please refer to FIG. 1 , which is a schematic diagram showing a conventional source driver. The source driver 100 includes a channel 108, a multiplexer (MUX) 112, an output 114, and a data bus 118. Channel 108 is coupled to output 114 via multiplexer 112. Channel 108 has a shift register 122, a latch unit 133, a level shifter 128, and a digital/analog converter (DAC) 130. The latch unit 133 includes a first latch 124 and a second latch 126 in series. The data is transmitted on the data bus 118 and stored in the latch unit 133. More specifically, the data may be stored in the first latch 124, stored in the second latch 126, and then transmitted to the display (not shown) via the output 114 to display the corresponding image on the display. .

However, when the source driver 100 is to be turned off, the power supply voltage supplied to the source driver 100 changes, and the source driver 100 is coupled. Improper voltage is supplied to the display, causing abnormal images on the display, such as Line Defects or Band Mura.

There is therefore a need for a new source driver that allows the display to be properly imaged when the source driver is turned off.

Accordingly, one aspect of the present invention provides a source driver that enables a display to be normally developed when the source driver is turned off.

According to an embodiment of the invention, the source driver is powered by a power supply, the source driver comprising at least two channels, at least two outputs, at least one multiplexer, at least one charge sharing switch, and a voltage drop detector. Detector. The multiplexer electrically connects the channel and the output to control the connection between the channel and the output. The charge sharing switch is electrically connected to the output. The voltage drop detector detects whether the first supply voltage is insufficient by the power supply output, and if not, turns on the charge sharing switch, and disconnects the channel from the output terminal by the multiplexer.

Another aspect of the present invention provides a noise suppression method for a source driver that can eliminate shutdown noise generated when a display is turned off by a source driver.

According to another embodiment of the present invention, the noise suppression method determines whether a power supply enters a shutdown state, and when the power supply enters a shutdown state, the power supply is powered by a plurality of output terminals of the source driver. The charge is redistributed.

The source driver and the noise suppression method of the above embodiment can eliminate The image noise generated when the source driver is turned off makes the display develop normally.

The source driver and the noise suppression method of the following embodiments can eliminate image noise generated when the source driver is turned off, and reduce abnormal display of the display.

Please refer to FIG. 2A, which is a schematic diagram of a source driver according to an embodiment of the present invention. The source driver 200 is powered by a power supply 202 that can provide one of a first supply voltage and a second supply voltage at a high potential. The source driver 200 includes a plurality of channels 208, a multiplexer (MUX) 212, and a plurality of outputs 214. The multiplexer 212 is electrically coupled to the channel 208 and the output 214 to control the connection of the channel 208 to the output 214.

The voltage drop detector 204 is electrically connected to the power supply 202 and the controller 206. The voltage drop detector 204 detects the values of the first supply voltage and the second supply voltage to determine the power supply 202 and the source driver 200. Whether the state is starting to be turned on or starting to be turned off, and generating a reset signal RS according to the state detection result to operate the controller 206. Specifically, the voltage drop detector 204 detects whether the values of the first supply voltage and the second supply voltage output by the power supply 202 are lower than a critical value, if the first supply voltage or the second supply voltage is lower than the critical value. The value represents that the source driver 200 is in the off state, and the voltage drop detector 204 generates the reset signal RS.

The controller 206 generates a control signal CN according to the reset signal RS. The control signal CN is transmitted to the charge sharing switch 220 to turn on the charge sharing switch 220. Since the charge sharing switch 220 is electrically connected between each of the two output terminals 214, when the controller 206 turns on the charge sharing switch 220, all the output terminals 214 are electrically connected together, so that the corresponding data on the display The charge of the line is redistributed to an average.

Since the display receives the voltage transmitted by the output terminal 214, if the voltage of the display data line connected to each output terminal 214 can be consistent, the voltage of each display block on the display can also be consistent, thereby avoiding the image displayed by the display. Noise is generated. At this time, the gate driver of the display activates all the scan lines so that the voltages of all the pixels are the same. In addition, the control signal CN generated by the controller 206 can be transmitted to the multiplexer 212 to disconnect the channel 208 from the output 214 when the source driver 200 is turned off. Therefore, when the source driver is turned off, the data signal with abnormal voltage can be prevented from being transmitted to the output terminal, thereby further avoiding image noise on the display.

Please refer to FIG. 2B, which is a schematic diagram of a source driver according to another embodiment of the present invention. The source driver 200 is powered by a power supply 202 that can provide one of a first supply voltage and a second supply voltage at a high potential. The source driver 200 includes a plurality of channels 208, a multiplexer (MUX) 212, and a plurality of outputs 214. The multiplexer 212 is electrically coupled to the channel 208 and the output 214 to control the connection of the channel 208 to the output 214.

In this embodiment, the functions and structures of the voltage drop detector 204, the controller 206, the channel 208, the multiplexer (MUX) 212, and the output 214 are the same as those of FIG. 2A, but the embodiment is Charge sharing switch 220 The voltage switch 222 is further connected to a fixed voltage terminal, such as the ground terminal 224. When the source driver 200 is turned off, the controller 206 generates the control signal CN according to the reset signal RS, and transmits the control signal CN to the charge sharing switch 220 to turn on the charge sharing switch 220 and simultaneously turn on the voltage switch 222. An output 214 is coupled to ground 224. Since the charge sharing switch 220 is electrically connected to the output terminal 214 and the ground terminal 224, when the controller 206 turns on the charge sharing switch 220, all the output terminals 214 are electrically connected and grounded so that the corresponding display The potential of each data line is the ground potential. Thus, when the source driver 200 is turned off, the voltages of the display blocks on the display tend to be uniform, and the image displayed by the display is prevented from generating noise.

Please refer to FIG. 2C, which is a schematic diagram of a source driver according to still another embodiment of the present invention. The function and structure of the source driver of this embodiment are the same as those of FIG. 2B. However, the charge sharing switch 220 of this embodiment is further connected to a fixed voltage terminal, for example, the common voltage terminal Vc, through the voltage switch 222. When the source driver is turned off, the charge sharing switch 220 is turned on, and the voltage switch 222 is also turned on to connect an output terminal 214 to the common voltage terminal Vc. Thus, all the output terminals 214 are electrically connected and connected to the common voltage. The terminal Vc is such that the potential of each corresponding data line on the display is equal to the potential of the common voltage. Thus, when the source driver 200 is turned off, the voltages of the display blocks on the display tend to be uniform, and the image displayed by the display is prevented from generating noise.

Please refer to FIG. 3, which is a schematic diagram of a source driver according to still another embodiment of the present invention. In this embodiment, the power supply 302 provides a source Pole driver 300 power supply. The source driver 300 includes a channel 308, a multiplexer (MUX) 312, an output 314, a data bus 318, a charge sharing switch 320, a voltage drop detector 304, and a controller 306. The voltage drop detector 304 is coupled to the power supply 302 and the controller 306 is coupled to the voltage drop detector 304. Output 314 is coupled to channel 308 via multiplexer 312.

Similar to the source driver of FIG. 2A, the controller 306 generates a control signal CN according to the reset signal RS, and transmits the control signal CN to the charge sharing switch 320 to turn on the charge sharing switch 320. Since the charge sharing switch 320 is electrically connected between the output terminals 314, when the controller 306 turns on the charge sharing switch 320, all the output terminals 314 are electrically connected together, so that the corresponding data lines on the display are The charge redistribution is an average.

Since the display receives the voltage transmitted by the output terminal 314, if the voltage of the display data line connected to each output terminal 314 can be consistent, the voltage of each display block on the display can also be consistent, thereby avoiding the image displayed by the display. Noise is generated. At this time, the gate driver of the display activates all the scan lines so that the voltages of all the pixels are the same. In addition, the control signal CN generated by the controller 306 can be transmitted to the multiplexer 312 to disconnect the channel 308 from the output 314 when the source driver 300 is turned off. Therefore, when the source driver is turned off, the data signal with abnormal voltage can be prevented from being transmitted to the output terminal 314, thereby further avoiding image noise on the display.

Channel 308 has a shift register 322, a latch unit 333, a level shifter 328, and a digital/analog converter (DAC) 330. Latch unit 333 The first latch 324 and the second latch 326 are connected in series, and the latch unit 333 can store the data transmitted by the data bus 318. More specifically, the data may first be stored in the first latch 324 and then stored in the second latch 326.

When the power supply 302 is normally powered to the source driver 300, the data in the channel 308 is transferred to the multiplexer 312, and then transmitted to the display (not shown) via the multiplexer 312 and the output 314 to The corresponding image is displayed on the display. However, when the source driver 300 is about to be turned off, the voltage transferred to the source driver 300 begins to be insufficient. If the voltage is insufficient, the voltage drop detector 304 generates a reset signal RS to reset the controller 306.

The controller 306 generates the control signal CN according to the reset signal RS. This control signal CN is transmitted to the charge sharing switch 320 to turn on/off the charge sharing switch 320. The control signal CN can be further transmitted to the multiplexer 312, causing the input/output 多 of the multiplexer 312 to assume a high impedance state to disconnect the channel 308 from the output terminal 314. Therefore, when the power supply 302 and the source driver 300 are turned off, the unstable voltage on the output terminal 314 is not transmitted to the display, and the image displayed on the display can be prevented from generating noise.

Please refer to FIG. 4, which is a schematic diagram of a voltage drop detector according to an embodiment of the present invention. The voltage drop detector 304 includes a first voltage divider 402, a second voltage divider 404, a first comparator 406, a second comparator 408, a first inverter 410, a second inverter 412, and a third reverse. Phaser 414, fourth inverter 416, level shifter 418, fifth inverter 420, and OR gate 426. The OR gate 426 includes a reverse OR gate 422 and a sixth inverter 424 in series.

The first voltage divider 402 includes resistors R1 through R7 connected in series. The first voltage divider 402 is generated according to the first supply voltage VDDA of the power supply output. The first divided voltage VA1. The first comparator 406 compares the first divided voltage VA1 with the threshold voltage VTH and generates a first comparison signal RSA. If the first divided voltage VA1 is less than the threshold voltage VTH, the first comparison signal RSA is high, indicating that the voltage of the power supply is insufficient, that is, the power supply and the source driver are being turned off; When the voltage VA1 is greater than the threshold voltage VTH, the first comparison signal RSA is low, indicating that the power supply is normally powered to the source driver.

Similarly, the second voltage divider 404 includes resistors R11 through R16 connected in series. The second voltage divider 404 generates a second divided voltage VD1 according to the second supply voltage VDDD output from the power supply. The second comparator 408 compares the second divided voltage VD1 with the threshold voltage VTH and generates a second comparison signal RSD, and the level shifter 418 shifts the level of the second comparison signal RSD. If the second divided voltage VD1 is less than the threshold voltage VTH, the second comparison signal RSD is high, indicating that the source driver is about to be turned off. If the second divided voltage VD1 is greater than the threshold voltage VTH, the second comparison signal RSD is low, indicating that the power supply is normally powered to the source driver.

In this embodiment, the voltage value of the first supply voltage V _DDA is greater than the voltage value of the second supply voltage V _DDD , and the first comparator and the second comparator are respectively a high voltage component and a low voltage component. The setting of the first divided voltage VA1, the second divided voltage VD1, and the threshold voltage VTH can be determined by the user, wherein the threshold voltage VTH must be stable without being easily affected by the output voltage of the power supply, so that a voltage such as a trench can be used. A Band-gap Voltage Generator is used to generate the threshold voltage VTH.

The first inverter 410 and the second inverter 412 transmit the first comparison signal RSA to one of the inputs of OR gate 426. The third inverter 414, the fourth inverter 416, the level shifter 418 and the fifth inverter 420 pass the second comparison signal RSD to the other input of the OR gate 426, wherein the level shifter 418 is used to shift the second comparison signal RSD.

If the first comparison signal RSA and the second comparison signal RSD are both low, the OR gate 426 outputs a low potential signal, indicating that the power supply is normally powered to the source driver, so no reset signal is generated. Conversely, if the first comparison signal RSA and/or the second comparison signal RSD are high, or the gate 426 outputs a high potential signal indicating that the power supply is about to be turned off, a reset signal RS is generated.

According to the above embodiment, in order to improve the shutdown noise of the display, it may be determined whether the power supply and the source driver enter a shutdown state; when the power supply and the source driver enter a shutdown state, the charge on the output of the source driver is made. Redistribute and disconnect the source driver output from the channel to avoid image noise on the display.

Although the present invention has been disclosed in a preferred embodiment as described above, it is not intended to limit the invention, and any of the ordinary skill in the art to which the invention pertains may be made without departing from the spirit and scope of the invention. The scope of protection of the present invention is defined by the scope of the appended claims.

100‧‧‧Source Driver

108‧‧‧ channel

112‧‧‧Multiplexer

114‧‧‧output

118‧‧‧ data bus

122‧‧‧Shift register

124‧‧‧First latch

126‧‧‧Second lock

128‧‧‧ position shifter

130‧‧‧Digital/Analog Converter

133‧‧‧Lock unit

200‧‧‧Source Driver

202‧‧‧Power supply

204‧‧‧Fall drop detector

312‧‧‧Multiplexer

314‧‧‧ Output

318‧‧‧ data bus

320‧‧‧Charge sharing switch

322‧‧‧Shift register

324‧‧‧First latch

326‧‧‧Second lock

328‧‧‧ position shifter

330‧‧‧Digital/Analog Converter

333‧‧‧Lock unit

402‧‧‧First voltage divider

404‧‧‧Second voltage divider

406‧‧‧First comparator

408‧‧‧Second comparator

206‧‧‧ Controller

208‧‧‧ channel

212‧‧‧Multiplexer

214‧‧‧ Output

220‧‧‧Charge sharing switch

222‧‧‧voltage switch

224‧‧‧ Grounding terminal

300‧‧‧Source Driver

302‧‧‧Power supply

304‧‧‧pressure drop detector

306‧‧‧ Controller

308‧‧‧ channel

410‧‧‧First Inverter

412‧‧‧Second inverter

414‧‧‧ third inverter

416‧‧‧fourth inverter

418‧‧‧ position shifter

420‧‧‧ fifth inverter

422‧‧‧Anti-gate

424‧‧‧ sixth inverter

426‧‧‧ or gate

The above and other objects, features, advantages and embodiments of the present invention will become more apparent and understood. Figure 1 is a schematic diagram showing a conventional source driver.

2A is a schematic view showing a source driver according to an embodiment of the present invention.

2B is a schematic diagram of a source driver according to another embodiment of the present invention.

2C is a schematic view showing a source driver according to still another embodiment of the present invention.

FIG. 3 is a schematic view showing a source driver according to still another embodiment of the present invention.

4 is a schematic view of a voltage drop detector according to an embodiment of the present invention.

200‧‧‧Source Driver

202‧‧‧Power supply

204‧‧‧Fall drop detector

206‧‧‧ Controller

208‧‧‧ channel

212‧‧‧Multiplexer

214‧‧‧ Output

220‧‧‧Charge sharing switch

RS‧‧‧Reset signal

CN‧‧‧Control signal

Claims (13)

A source driver is powered by a power supply, the source driver includes: at least two channels; at least two outputs; at least one multiplexer electrically connected to the channels and the outputs to control the channels a connection with the output terminals; at least one charge sharing switch electrically connected to the output terminals; and a voltage drop detector for detecting whether the first supply voltage is insufficient by the power supply output If not, the charge sharing switch is turned on, and the multiplexer disconnects the channels from the output terminals, and the voltage drop detector can detect one of the outputs output by the power supply. a second supply voltage to determine a state of the source driver, wherein a voltage value of the first supply voltage is greater than a voltage value of the second supply voltage. The source driver of claim 1, further comprising a voltage switch, wherein the voltage drop detector detects that the first supply voltage is insufficient, and electrically connects a fixed voltage terminal to the outputs. One of the ends. The source driver of claim 1, wherein the voltage drop detector comprises: a first voltage divider, generating a first divided voltage according to the first supply voltage; and a first comparison Comparing the first divided voltage with a threshold voltage, To determine the state of the source driver. The source driver of claim 3, wherein the voltage drop detector further comprises: a second voltage divider, generating a second voltage divider according to the second supply voltage output by the power supply a second comparator that compares the second divided voltage with the threshold voltage to determine the state of the source driver; and an OR gate having two inputs electrically coupled to the first comparator and the first The output of the two comparators outputs a reset signal. The source driver of claim 4, wherein the voltage drop detector further comprises a quasi-shifter electrically connected to the second comparator and the sluice. The source driver of claim 4, wherein the first voltage divider and the second voltage divider respectively comprise a plurality of series resistors. The source driver of claim 4, further comprising a controller, controlling the charge sharing switch and the multiplexer according to the reset signal, thereby disconnecting the channels from the outputs . A method for suppressing noise includes: determining whether a power supply enters a closed state, wherein comparing a threshold voltage to a first supply voltage of one of the power supplies is first Dividing a voltage, when the first divided voltage is less than the threshold voltage, indicating that the power supply enters a closed state; determining whether a second supply voltage supplied by the power supply is insufficient, thereby determining whether the power supply enters a closed state, wherein a voltage value of the second supply voltage is less than a voltage value of the first supply voltage; and when the power supply enters a shutdown state, causing a plurality of output terminals of one of the source drivers to be powered by the power supply The charge on the redistribution. The method for suppressing noise according to claim 8 further includes disconnecting the output terminals of the source driver from the plurality of channels when the power supply enters a closed state. The method for suppressing noise according to claim 8, wherein when the power supply enters a closed state, at least one charge sharing switch is turned on, and the output ends are electrically connected to a fixed voltage terminal. The charge on the outputs is redistributed through the charge sharing switch. The noise suppression method of claim 10, wherein the fixed voltage terminal receives a ground voltage. The noise suppression method of claim 8, wherein the fixed voltage terminal receives a common voltage. The method for suppressing noise according to claim 8, wherein the threshold voltage is compared with a second corresponding to the second supply voltage. The divided voltage, when the second divided voltage is less than the threshold voltage, represents that the power supply enters a closed state.