TWI383358B - Circuit and method for eliminating power-off noise of tft panel - Google Patents

Description

Shutdown noise cancellation circuit of thin film transistor liquid crystal display panel and method thereof

The present invention relates to a shutdown noise cancellation circuit for a thin film transistor liquid crystal display (TFT-LCD) panel, and more particularly to a circuit for eliminating vertical shutdown noise.

In order to avoid the occurrence of afterimages when the TFT-LCD panel is turned off, it is usually used with the reset IC and the XAO function of the gate driver to store the liquid crystal capacitors by turning on all the TFTs on the panel at the moment of shutdown. The charges are neutralized with each other to perform the action of turning off the afterimage. However, the above method does not solve the problem of vertical shutdown noise.

As far as the problem of vertical shutdown noise is concerned, all voltage levels are declining at the moment of shutdown. Due to differences in system design and collocation, the discharge speed of each voltage on the system is not uniform. In terms of the source driver, although the specification requires that the shutdown sequence be analog voltage (VAA) to stop outputting earlier than the digital voltage (VDD), it is difficult to control in practical applications. When the shutdown sequence does not meet the specification, or VAA and VDD fall below the normal operating voltage, the source driver may malfunction, resulting in an abnormal output voltage. When there is a difference between each of the output channels of the source driver, the final state of each data line will be inconsistent, thus causing the vertical shutdown of color straight stripes or band mura.

An embodiment of the shutdown noise cancellation circuit of a thin film transistor liquid crystal display panel of the present invention comprises a switch detection circuit, a program control circuit and a discharge circuit. The switch detection circuit generates a control signal according to a shutdown procedure. The program control circuit is configured to suspend an electrical connection between the analog power source and the at least one source driver power supply based on the control signal. The discharge circuit electrically connects the at least one source driver power supply to a ground potential according to the control signal.

An embodiment of a shutdown noise cancellation circuit of a thin film transistor liquid crystal display panel of the present invention comprises a reset integrated circuit, a first resistor, a second switch, a first switch, a second resistor and a The third switch. The reset integrated circuit is configured to compare whether the level of the power supply voltage of the liquid crystal panel drops to a predetermined value. One end of the first resistor is electrically coupled to the input of the reset integrated circuit, and the other end is electrically coupled to the output of the reset integrated circuit. The second switch is connected to supply an analog power supply of the liquid crystal panel to a power input end of the at least one source driver. The control end of the first switch is electrically connected to the output end of the reset integrated circuit, and an input end thereof is electrically connected to the control end of the second switch. One end of the second resistor is electrically connected to the control terminal of the second switch, and the other end thereof is electrically connected to the analog power source. The control terminal of the third switch is electrically connected to the control terminal of the second switch, one input terminal is electrically connected to the power input end of the at least one source driver, and the other input terminal is electrically connected to the ground level.

An embodiment of the method for canceling noise cancellation of a thin film transistor liquid crystal display panel of the present invention comprises the steps of: generating a control signal according to a shutdown procedure of the TFT-LCD panel; and suspending supply to the source according to the control signal The power source of the driver is connected to the ground terminal of the at least one source driver, and the power input terminal of the at least one source driver is electrically connected to a ground potential via a switch according to the control signal.

1 is a first embodiment of a shutdown noise cancellation circuit of a thin film transistor liquid crystal display panel according to an embodiment of the present invention. The shutdown noise cancellation circuit 1 includes a switch detection circuit 10, a program control circuit 11, and a discharge circuit 12. The switch detection circuit 10 generates a control signal CON according to a shutdown process, wherein the shutdown process is initiated when the level of a first signal S1 drops to a predetermined value. When the shutdown program is started, the control signal CON is in a low level state. The first signal S1 is an input power source of the analog power source VAA or a reset integrated circuit, and is a shutdown signal from a timing controller or a PWM circuit. The program control circuit 11 is composed of at least one MOS transistor, an analog switch or a relay, and according to the control signal CON, suspends the electrical connection between the analog power source VAA and the at least one source driver power supply. The discharge circuit 12 is composed of a discharge resistor, a MOS transistor or a relay, and electrically connects the at least one source driver power supply to a ground potential according to the control signal CON. Another national patent application No. 95133525 of the Applicant, the inventor entitled "Planar Display and Its Timing Controller" discloses a circuit for eliminating shutdown noise, the disclosure of which is incorporated herein by reference.

2 is a shutdown noise canceling circuit of a thin film transistor liquid crystal display panel according to an embodiment of the present invention. The shutdown noise canceling circuit 2 of the second embodiment further describes the detailed circuit configuration of the power-off noise canceling circuit 1 of the first embodiment. The switch detection circuit 10 includes a first resistor R1 and a reset integrated circuit U1. One end of the first resistor R1 is electrically connected to the input end of the reset integrated circuit U1 to receive an input power S1. The first resistor The other end of R1 is electrically coupled to the output of the reset integrated circuit U1. The program control circuit 11 includes a second resistor R2, a second switch Q2, and a first switch Q1. The two ends of the second switch Q2 are electrically connected to the analog power source VAA and the at least one source driver power supply and the second resistor, respectively. The second end of R2 is electrically connected to the control end of the second switch Q2 and the analog power supply VAA, and the two end points of the first switch Q1 are respectively electrically connected to the control end of the second switch Q2 and the ground potential, and the first The control terminal of switch Q1 is used to receive control signal CON. The discharge circuit 12 includes a third switch Q3, and the two ends of the third switch Q3 are electrically connected to the ground potential and the at least one source driver power supply, respectively.

The reset integrated circuit U1 and the second resistor R2 of the second embodiment belong to the switch detection circuit, and the first switch Q1, the second switch Q2, the first resistor R1 belong to the power supply sequence control circuit, and the third switch Q3 It belongs to the shutdown fast discharge circuit.

A third embodiment of the method for canceling the noise cancellation of the thin film transistor liquid crystal display (TFT-LCD) panel of the present invention is based on a shutdown procedure of the TFT-LCD panel to generate a control signal. The shutdown procedure is initiated when the level of a first signal S1 drops to a predetermined value. The first signal S1 is a shutdown signal from a timing controller or a PWM circuit of the liquid crystal panel, which is used as an input power source for the analog power supply VAA or a reset integrated circuit. Then, the power input terminal of the at least one source driver is connected to the analog power source VAA according to the control signal CON, and the power input terminal of the at least one source driver is electrically connected to a ground potential according to the control signal CON.

In the third embodiment, when the power is turned on, after the digital power supply VDD is first established, the integrated circuit is reset to pull the output control signal to the high level. At this time, the first switch Q1 and the second switch Q2 are enabled, the third switch Q3 is turned off, and the analog power supply VAA is established, thereby complying with the power-on sequence of the source driver. When the power is turned off, if the digital power supply VDD falls below the detection potential of the reset integrated circuit, resetting the integrated circuit at this time will pull the output control signal CON to the low level. At this time, the first switch Q1 and the second switch Q2 are turned off, the third switch Q3 is enabled, and the analog power supply VAA is quickly discharged to the grounding level through the third switch Q3 in an instant, thereby complying with the shutdown of the source driver. order.

When the sequence of the switch is completely in accordance with the requirements of the specification, and the analog power supply VAA discharges very fast (less than a few milliseconds), even if each output channel of the source driver is slightly different in the process of shutting down the voltage, Since the source driver VAA has been quickly discharged to the grounding level through the third switch Q3, each output channel is fixed to the grounding level, so the picture will be nearly uniform and there will be no shutdown noise.

The technical and technical features of the present invention have been disclosed as above, and those skilled in the art can still make various substitutions and modifications without departing from the spirit and scope of the invention. Therefore, the scope of the present invention should be construed as being limited by the scope of the appended claims

1. . . Shutdown noise cancellation circuit

10. . . Switching machine detection circuit

11. . . Program control circuit

12. . . Discharge circuit

2. . . Shutdown noise cancellation circuit

VAA. . . Analog power supply

CON. . . Control signal

Q1. . . First switch

Q2. . . Second switch

Q3. . . Third switch

1 is a first embodiment of a shutdown noise canceling circuit of a thin film transistor liquid crystal display panel of the present invention; and FIG. 2 is a second embodiment of a shutdown noise canceling circuit of the thin film transistor liquid crystal display panel of the present invention.

1. . . Shutdown noise cancellation circuit

10. . . Switching machine detection circuit

11. . . Program control circuit

12. . . Discharge circuit

CON. . . Control signal

VAA. . . Analog power supply

R1, R2. . . resistance

Q1. . . First switch

Q2. . . Second switch

Q3. . . Third switch

Claims (4)

A shutdown noise cancellation circuit for a thin film transistor liquid crystal display (TFT-LCD) panel, comprising: a switch detection circuit for generating a control signal according to a shutdown process; a program control circuit according to the control signal Suspening the electrical connection between the analog power source of the source driver and the power input end of the at least one source driver; and a discharge circuit electrically connecting the power input end of the at least one source driver to a ground potential according to the control signal; The program control circuit is composed of at least one MOS transistor, an analog switch or a relay; wherein the discharge circuit is a first switch, and the two ends of the first switch are electrically connected to the ground potential and the at least one source respectively Pole driver power supply. The shutdown noise cancellation circuit of claim 1, wherein the shutdown procedure is initiated when the level of the power supply voltage of the liquid crystal panel drops to a predetermined value. The shutdown noise cancellation circuit of claim 1, wherein the control signal is in a low level state when the shutdown program is started. A shutdown noise cancellation circuit for a thin film transistor liquid crystal display (TFT-LCD) panel, comprising: a reset integrated circuit for comparing whether a level of a power supply voltage of the liquid crystal panel drops to a predetermined value; a first resistor One end of which is electrically connected to the input of the reset integrated circuit The other end is electrically connected to the output end of the reset integrated circuit; a second switch is connected to supply the analog power supply of the liquid crystal panel to the power input end of the at least one source driver; a first switch The control terminal is electrically connected to the output end of the reset integrated circuit, and an input end thereof is electrically connected to the control end of the second switch; a second resistor, one end of which is electrically connected to the control end of the second switch The other end is electrically connected to the analog power source; and a third switch has a control end electrically connected to the control end of the second switch, and an input end electrically connected to the power input end of the at least one source driver, Its other input is electrically connected to the ground level.