TWI474302B - A display circuit - Google Patents

Description

Display circuit

The present invention relates to a display circuit, and more particularly to a display circuit for suppressing reflected waves.

Current display interfaces use, for example, a multi-drop topology interface that has the characteristics of an input signal and multiple output signals. The display interface has a plurality of driving ICs, and each driving IC is electrically connected to the output signal, and in the case of low resolution and slow output signal, the interface has no problem in use. However, with the increasing resolution of today's displays and the faster transfer speeds, the architecture of the multi-tap display interface described above will encounter some limitations.

Please refer to FIG. 1A, which is a schematic diagram of the connection between the Timing Controller (Tcon) and the source drivers 1, 2 and 3 of the conventional display circuit 1. The display driver circuit is generally composed of a timing controller, a source driver, and a gate driver (Gate Driver). Tcon is mainly used for analog display display control, and provides timing control signals for the gate driver, source driver and VCOM polarity control on the LCD screen of the display, thereby realizing display control of analog RGB signals. For liquid crystal displays, due to the relatively complex design of TCON, Therefore, in the case of poor design, the problem of electromagnetic interference (EMI) is likely to occur.

Please refer to the first B diagram and the first C diagram together, which is a circuit diagram of the conventional display circuit 1 and an eye diagram of the output signal. The display circuit 1 includes a timing controller and a source driver 13. The timing controller includes a current source 11 and a transmission line 12. The current source 11 is used to generate a plurality of incident wave signals. The transmission line 12 is electrically connected to the current source 11 and receives a plurality of incident wave signals. The source driver 13 is electrically connected to the transmission line 12, and receives a plurality of incident wave signals, and generates a plurality of reflected wave signals according to the plurality of incident wave signals.

As described above, the conventional display circuit 1 is that when the impedance of the transmission line 12 and the source driver 13 does not match, electromagnetic waves cause multiple reflections in the transmission line 12. In other words, the reflected wave signal will overlap the incident wave signal, causing an overshoot 14 or undershoot 15 as indicated by the dashed line in Figure C, thereby distorting the input signal.

In view of this, how to provide a display circuit with simple design and low cost has become an urgent problem to be solved in the industry.

In view of the above, the embodiment of the present invention provides a display circuit for overcoming the problem of overshoot and undershoot of the output signal, so that the waveform of the output signal can be more accurately matched with the input signal to avoid distortion of the output signal.

The invention provides a display circuit comprising a timing controller and a source driver. The timing controller includes a current source, a first transmission line, at least one series resistor, and a second transmission line. The current source is used to generate a plurality of incident wave signals. The first transmission line is electrically connected to the current source and receives a plurality of incident wave signals. At least one series resistor is electrically connected to the first transmission line, and is disposed at a position close to the current source, and receives a plurality of incident wave signals. The second transmission line is electrically connected to the series resistor and receives a plurality of incident wave signals. The source driver includes a load circuit electrically connected to the second transmission line, and receives a plurality of incident wave signals, and generates a plurality of reflected wave signals to the at least one series resistor according to the plurality of incident wave signals.

According to the above description, the display circuit of the present invention can transmit the incident wave signal from the current source to the source of the series resistor disposed closest to the current source by adding at least one series resistor to the position close to the current source. After the driver, the energy of the reflected wave is consumed by the action of the series resistor, and the damping of the reflected wave is suppressed, thereby overcoming the problem of overshoot and undershoot of the output signal, so that the waveform of the output signal can be more accurately input with the signal. Matching to avoid distortion of the output signal, and to achieve low cost and simple design.

11‧‧‧current source

12‧‧‧ transmission line

13‧‧‧Source Driver

14, 24‧‧ ‧ overshoot

15, 25‧‧‧ Undershoot

1, 2‧‧‧ display circuit

22‧‧‧First transmission line

23‧‧‧Second transmission line

Req‧‧‧ series resistor

The first A diagram is a schematic diagram of the connection between the timing controller and the source driver of the conventional display circuit; the first B diagram is a circuit diagram of the conventional display circuit; the first C diagram is the eye diagram of the output signal of the conventional display circuit ; 2A is a schematic diagram of the connection between the timing controller and the source driver of the display circuit of the present invention; the second B is a circuit diagram of the display circuit of the present invention; and the third to third C diagrams are the measurement of the present invention. The eye diagram of the source driver output signal of the display circuit having series resistance; and the fourth diagram is the source driver output signal eye diagram amplification waveform of the display circuit for measuring the presence or absence of series resistance.

Please refer to FIG. 2A and FIG. 2B together, which are schematic diagrams and circuit diagrams of the timing controller and the source driver of the display circuit 2 of the present invention. As described in the prior art, the display circuit 2 of the present invention overcomes the problem of electromagnetic interference by adding at least one series resistance Req between the Tcon and the source driver 1, that is, at least one series resistance Req is disposed near the current source 11. After the incident wave signal generated by the current source 11 is transmitted to the source driver 1, the generated reflected wave signal can be suppressed via at least one series resistance Req.

In addition, it should be noted that the number of series resistance Req between the Tcon of the present invention and the source driver 1 is two in the figure, but the number is not limited thereto, but is in Tcon and each source driver. Between 1, 2, 3, at least one series resistor Req is disposed between the source driver 1 closest to the current source 11 and the current source 11, so that the reflected wave after first being transmitted to the source driver 1 can be via the series resistor Req Suppress to reduce subsequent electromagnetic interference. In other words, the display circuit 2 of the present invention is It is required to increase the number of series resistances Req between each of the source drivers 2, 3 and the current source 11, so that the reflected wave signals can be suppressed by each of the series resistances Req added.

The display circuit 2 includes a timing controller and a source driver 13. The timing controller includes a current source 11, a first transmission line 22, at least one series resistor Req, and a second transmission line 23. The current source 11 is used to generate a plurality of incident wave signals. The first transmission line 22 is electrically connected to the current source 11 and receives a plurality of incident wave signals. At least one series resistor Req is electrically connected to the first transmission line 22, and is disposed at a position close to the current source 11, and receives a plurality of incident wave signals. The second transmission line 23 is electrically connected to the series resistance Req and receives a plurality of incident wave signals. The source driver 13 includes a load circuit electrically connected to the second transmission line 23 and receives a plurality of incident wave signals, and generates a plurality of reflected wave signals to the at least one series resistance Req according to the plurality of incident wave signals. It should be noted that a plurality of reflected wave signals are generated when the source driver 13 does not match the impedance of the first transmission line 22 or the second transmission line 23, and those skilled in the art should understand the principle. No longer.

Referring to FIG. 3A to FIG. 3C together, after adding at least one series resistance Req to the display circuit 2 of the present invention, the eye waveform of the output signal on the source driver is measured. Compared with the prior art shown in FIG. C, the display circuit 1 has no series resistance Req, and the output signal is obviously affected by the reflected wave, causing problems of overshoot 14 and undershoot 15, and in the display circuit 2 of the present invention. After increasing the series resistance Req, it can be seen from the figure that the eye height and the eye width of the eye pattern are large, and the phenomenon of overshoot 24 and undershoot 25 is obviously suppressed, that is, the quality of the digital signal conversion is better. Accordingly, the display circuit of the present invention 2 By increasing the series resistance Req, the oscillation of the reflected wave can be made small, that is, the magnitude of the reflected wave is suppressed by the series resistance Req.

The fourth figure is an eye-shaped amplification waveform for measuring the output signal on the source driver according to whether the display circuit has a series resistance Req, wherein the thick line is an output signal waveform without a series resistance Req, and the thin line is after increasing the series resistance Req Output signal waveform. It is apparent from the enlarged figure that the phenomenon of overshoot 24 and undershoot 25 is significantly suppressed after the series resistance Req is increased.

In an embodiment of the invention, the resistance of the series resistor is approximately 50 ohms. As shown in the third to third C diagrams, the series resistance Req has a resistance value of 22 ohms, 50 ohms, and 75 ohms. In addition, an embodiment of the present invention further includes a measuring circuit electrically connected between the current source 11 and the first transmission line 22 for measuring an input signal such as a square wave.

In summary, the display circuit of the present invention can transmit the incident wave signal from the current source to the source of the series resistor disposed closest to the current source by adding at least one series resistor to the position close to the current source. After the driver, the energy of the reflected wave is consumed by the action of the series resistor, and the amplitude of the reflected wave is suppressed, thereby overcoming the problem of overshoot and undershoot of the output signal, so that the waveform of the output signal can be more accurately matched with the input signal, Avoid distortion of the output signal, and achieve low cost and simple design.

The above description is only the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention; all other equivalent changes or modifications which are not departing from the spirit of the invention should be included in the following Within the scope of the patent application.

11‧‧‧current source

13‧‧‧Source Driver

2‧‧‧Display circuit

22‧‧‧First transmission line

23‧‧‧Second transmission line

Req‧‧‧ series resistor

Claims (4)

A display circuit comprising: a timing controller comprising a current source for generating a plurality of incident wave signals; a first transmission line electrically connected to the current source and receiving the plurality of incident wave signals At least one series resistor electrically connected to the first transmission line and disposed adjacent to the current source, and receiving the plurality of incident wave signals; and a second transmission line electrically connected to the series resistor and receiving The plurality of incident wave signals; and a source driver includes a load circuit electrically connected to the second transmission line, and receiving the plurality of incident wave signals, and generating a plurality of the plurality of incident wave signals according to the plurality of incident wave signals And reflecting the wave signal to the at least one series resistor, wherein the at least one series resistor suppresses the plurality of reflected wave signals. The display circuit of claim 1, wherein the series resistor has a resistance of approximately 50 ohms. The display circuit of claim 1, wherein the plurality of reflected wave signals are generated when the source driver does not match the impedance of the first transmission line or the second transmission line. The display circuit of claim 1, wherein the incident wave signal is a square wave.