TWI587706B - Display and control method thereof - Google Patents

Description

Display and control method thereof

The invention discloses a display and a control method thereof, in particular to a display compatible with a four-wire external video source and a five-wire external video source and a control method thereof.

Currently, the display is connected to an external video source (such as a video player, a video camera, an industrial instrument, or a medical instrument). It can be connected to an external video source through a five-wire (RGBHV) connection interface and four-wire type (RGBH+V). .) Connection interface or three-wire (R.Gs.B.) connection interface connection. Please refer to Figure 1. Figure 1 is a schematic illustration of a five-wire connection interface 100 that is common in the prior art. The type of connection interface needs to match different types of signal terminals. The first picture is based on the interface of BNC (Bayonet Neill-Concelman) terminal. It is red (R) video signal connection 埠110 from left to right, green (G A video signal port 埠120, a blue video (B) signal port 埠130, a horizontal sync signal port 埠140 and a vertical sync signal port 埠150 for receiving red video signals, green video signals, blue video signals, and levels, respectively. The synchronization signal (H-sync signal) and the vertical synchronization signal (V-sync signal). The above horizontal sync signal is used to control the scan line of the display, and the vertical sync signal is used to gather the scan line to form a frame display. As can be seen from Figure 1, the five-wire connection interface on the display can only be coupled to a five-wire external video source, and the three-wire, four-wire and five-wire connection interfaces cannot be integrated. In order to enable the display to be connected to a three-wire external video source or a four-wire external video source, according to the prior art, users and manufacturers are forced to use a variety of inconvenient adapters to repeatedly disassemble when the display is connected to an external video source. , or a variety of connection interfaces are set on the display, resulting in a complex display interface, the area is difficult to reduce. This has caused inconvenience to the user and is extremely Not conducive to product specifications.

An embodiment of the present invention includes a video display interface, an internal wiring interface, a red video signal path, a green video signal path, a blue video signal path, a vertical synchronous signal path, and a horizontal synchronization signal. a path, a first resistor, a second resistor, and a first switch. The video connection interface includes a red video signal port for receiving a red video signal, a green video signal port for receiving a green video signal, and a blue video signal port for receiving a blue color. a video signal; a vertical sync signal port for receiving a vertical sync signal; and a horizontal sync signal port for receiving a horizontal sync signal and/or the vertical sync signal. The internal wiring interface includes a red video signal endpoint, a green video signal endpoint, a blue video signal endpoint, a vertical sync signal endpoint, and a horizontal sync signal endpoint. The red video signal path includes a first end coupled to the end of the red video signal, and a second end coupled to the red video signal port. The green video signal path includes a first end coupled to the green video signal end point, and a second end coupled to the green video signal port. The blue video signal path includes a first end coupled to the blue video signal end point, and a second end coupled to the blue video signal port. The vertical synchronization signal path includes a first end coupled to the vertical sync signal end point, and a second end coupled to the vertical sync signal port. The horizontal synchronization signal path includes a first end coupled to the horizontal synchronization signal end point, and a second end coupled to the horizontal synchronization signal port. The first resistor includes a first end coupled to the horizontal synchronizing signal path, and a second end coupled to a low voltage end. The second resistor includes a first end coupled to the horizontal sync signal path and a second end. The first switch includes a first end coupled to the second end of the second resistor; a second end coupled to the low voltage end; and a control end configured to control whether the first switch is Turn on. When a four-wire external video source is coupled to the video connection interface, the four-wire external video source provides the vertical synchronization signal to the horizontal synchronization signal port, and turns on the first switch to enable the first Two resistor The first switch is coupled between the low voltage terminal and the horizontal synchronization signal path to connect the first resistor and the second resistor in parallel; when a five-wire external video source is coupled to the video connection interface, The five-wire external video source provides the vertical sync signal to the vertical sync signal port and does not turn on the first switch.

Another embodiment of the present invention discloses a control method for a display, wherein the display includes a video connection interface, an internal wiring interface, a horizontal synchronization signal path, a first resistor, a second resistor, and a first switch; The horizontal synchronization signal connection is coupled to the horizontal synchronization signal end of the internal wiring interface through the horizontal synchronization signal path, and the first resistance is coupled to the horizontal synchronization signal path and a low voltage end. The second resistor is coupled between the horizontal synchronization signal path and the first end of the first switch, and the second end of the first switch is coupled to the low voltage end. The method includes Controlling a control terminal of the first switch when the four-wire external video source is coupled to the video connection interface, and the four-wire external video source provides a vertical synchronization signal to the horizontal synchronization signal port The first switch is turned on, and the second resistor is coupled to the low voltage terminal and the horizontal synchronization signal path through the first switch, so that the first resistor is connected in parallel with the second resistor

Another embodiment of the present invention discloses a control method for a display, wherein the display includes a video connection interface, an internal wiring interface, a horizontal synchronization signal path, a first resistor, a second resistor, and a first switch; The horizontal synchronization signal connection is coupled to the horizontal synchronization signal end of the internal wiring interface through the horizontal synchronization signal path, and the first resistance is coupled to the horizontal synchronization signal path and a low voltage end. The second resistor is coupled between the horizontal synchronization signal path and the first end of the first switch, and the second end of the first switch is coupled to the low voltage end. The method includes When the five-wire external video source is coupled to the video connection interface, and the five-wire external video source provides a vertical synchronization signal to one of the video connection interfaces, the first switch is controlled. A control terminal makes the first switch non-conductive.

By using the display and the control method thereof disclosed in the embodiments of the present invention, the video connection interface can be compatible with the three-wire external video source, the four-wire external video source and the five-wire external video source without impedance incompatibility. Happening.

100‧‧‧5-wire connection interface

110, 2101, 3101‧‧‧ Red Video Signal Connection埠

120, 2102, 3102‧‧‧ Green Video Signal Connection埠

130, 2103, 3103‧‧‧Blue video signal connection埠

150, 2104, 2104‧‧‧ vertical sync signal connection埠

140, 2105, 3105‧‧‧ horizontal sync signal connection埠

220, 320‧‧‧Internal wiring interface

200, 300‧‧‧ display

210, 310‧‧‧ video connection interface

2201, 3201‧‧‧ Red Video Signal Endpoints

2202, 3202‧‧ Green Video Signal Endpoints

2203, 3203‧‧‧Blue Video Signal Endpoints

2204, 3204‧‧‧ Vertical sync signal endpoints

2205, 3205‧‧‧ horizontal sync signal endpoint

281, 381‧‧‧ Red video signal path

282, 382‧‧‧ Green video signal path

283, 383‧‧‧Blue video signal path

284, 384‧‧‧ vertical sync signal path

285, 385‧‧‧ horizontal sync signal path

291, 391‧‧‧ first resistance

292, 392‧‧‧ second resistor

270, 370‧‧‧ first switch

330‧‧‧Vertical Synchronous Signal Detection Module

351‧‧‧ diode

341‧‧‧ Capacitance

371‧‧‧Second switch

393‧‧‧ Third resistor

400‧‧‧ method

401 to 403‧‧ steps

Figure 1 is a schematic illustration of a five-wire connection interface in the prior art.

Figure 2 is a schematic illustration of a display of an embodiment of the invention.

Figure 3 is a schematic illustration of a display of another embodiment of the present invention.

Fig. 4 is a flow chart showing a display control method of an embodiment of the present invention.

Please refer to Figure 2. FIG. 2 is a schematic diagram of a display 200 disclosed in an embodiment of the present invention. As shown in FIG. 2, the display 200 includes a video connection interface 210, an internal wiring interface 220, a red video signal path 281, a green video signal path 282, a blue video signal path 283, a vertical synchronization signal path 284, and a horizontal synchronization signal path 285. A resistor 291, a second resistor 292 and a first switch 270. The video connection interface 210 includes a red video signal port 2101 for receiving a red video signal, a green video signal port 2102 for receiving a green video signal, and a blue video signal port 2103 for receiving a blue video signal. The synchronous signal port 104 2104 is configured to receive the vertical sync signal; and the horizontal sync signal port 埠 2105 is configured to receive the horizontal sync signal and/or the vertical sync signal. The internal wiring interface 220 includes a red video signal endpoint 2201, a green video signal endpoint 2202, a blue video signal endpoint 2203, a vertical sync signal endpoint 2204, and a horizontal sync signal endpoint 2205.

The red video signal port 2101 is coupled to the red video signal end point 2201 through the red video signal path 281; the green video signal port 2102 is transmitted through the green video signal path 282. The blue video signal port 2102 is coupled to the blue video signal end point 2203 through the blue video signal path 283; the vertical sync signal port 2104 is coupled to the vertical sync signal path 284 via the vertical sync signal path 284. The vertical sync signal endpoint 2204; and the horizontal sync signal port 2105 are coupled to the horizontal sync signal endpoint 2205 via the horizontal sync signal path 285. In addition, the horizontal sync signal path 285 is coupled to the low voltage terminal, such as the ground terminal, through the first resistor 291. As shown in FIG. 2, the horizontal sync signal path 285 is coupled to the first switch 270 through a second resistor 292 to a low voltage terminal (eg, a ground terminal). The value of the first resistor 291 is much larger than the second resistor 292. For example, the first resistor 291 can be, for example, a resistance of 2.2 kΩ, and the second resistor 292 can be, for example, a resistor of 77 Ω.

According to the standard specification, when the three-wire connection interface receives the signal from the three-wire external video source, the synchronous signal and the green signal integration (SOG) technology are used, so the vertical synchronization signal and the horizontal synchronization signal are both green video signals. The connection 埠 2102 receives, regardless of the impedance value of the vertical sync signal connection and the horizontal sync signal connection 埠 coupled to the ground. When the five-wire interface receives a signal from a five-wire external video source, the horizontal sync signal endpoint is coupled to an impedance of approximately 2.2 kΩ to ground. When the four-wire connection interface receives the signal from the four-wire external video source, the vertical sync signal and the horizontal sync signal are received by the same end point (for example, a horizontal sync signal end point), and the end point needs to be coupled to the The 75Ω to ground impedance is used as a partial voltage.

According to the embodiment of the present invention shown in FIG. 2, when a four-wire external video source (for example, a high-end medical device) is coupled to the video connection interface 210, the four-wire external video source synchronizes the vertical synchronization signal with the horizontal synchronization signal. The first switch 270 is turned on, and the second resistor 292 is coupled to the low voltage end (for example, the ground end) and the horizontal synchronization signal through the first switch 270 according to the embodiment of the present invention. Between the paths 285, the first resistor 291 and the second resistor 292 are connected in parallel. If the first resistor 291 and the second resistor 292 are respectively impedances of 2.2 kΩ and 77 Ω, the impedance values after parallel connection are calculated as: (2.2kΩ×77Ω)/(2.2kΩ+77Ω)=74.396Ω≒75Ω............(a)

It can be seen from the formula (a) that when the four-wire external video source is connected to the video connection interface 210 of FIG. 2, the horizontal synchronization signal path 285 and the low voltage terminal (such as the ground end) connected to the horizontal synchronization signal port 2105 are connected. The impedance value between the first resistor 291 and the second resistor 292 is about 75 Ω, which can meet the standard specifications and enable the video connection interface 210 to receive the signal normally.

When a five-wire external video source (for example, a video player) is coupled to the video connection interface 210, the five-wire external video source provides a vertical synchronization signal and a horizontal synchronization signal to a vertical synchronization signal connection 埠 2104 and a horizontal synchronization signal connection.埠 2105, at this time, according to the embodiment of the present invention, the first switch 270 is not turned on, so the impedance value between the horizontal sync signal path 285 connected to the horizontal sync signal port 2105 and the low voltage end (eg, the ground end) is equal to The value of a resistor 291, that is, 2.2 kΩ, conforms to the standard specifications and allows the video connection interface 210 to receive signals normally.

Therefore, the display 200 disclosed in the embodiment of the present invention in FIG. 2 can be compatible with the three-wire, four-wire, and five-wire external video sources only by the same video connection interface 210, without the need for a five-wire external video source. A separate adapter or multiple sets of different video connection interfaces are used with the four-wire five-wire external video source. The above control whether the first switch 270 is turned on can control the voltage level of the control end of the first switch 270 by a graphical user interface (GUI), a toggle switch, an integrated circuit, a detection circuit, or a single-pole switch to control Whether the first switch 270 is turned on.

Please refer to Figure 3. FIG. 3 is a schematic diagram of a display 300 according to another embodiment of the present invention.

The video connection interface 300, the internal wiring interface 320, the red video signal path 381, the green video signal path 382, the blue video signal path 383, and the vertical synchronization signal path 384, The horizontal synchronization signal path 385, the first resistor 391, the second resistor 392, the first switch 370, the red video signal port 1013101, the green video signal port 埠3102, the blue video signal port 埠3103, and the vertical sync signal port 埠3104, The horizontal synchronization signal connection 埠3105, the red video signal end point 3201, the green video signal end point 3202, the blue video signal end point 3203, the vertical synchronization signal end point 3204 and the horizontal synchronization signal end point 3205 are set in the same manner as the circuit connection. It is shown in the embodiment of Fig. 2, and therefore will not be described again.

The embodiment shown in FIG. 3 further includes a vertical sync signal detecting module 330, which includes a capacitor 341, a diode 351, a third resistor 393 and a second switch 371. The anode of the diode 351 is coupled to the vertical synchronization signal path 384, the cathode is coupled to the first end of the capacitor 341 and the control end of the second switch 371; the second end of the capacitor 341 is coupled to the low voltage terminal ( For example, the first end of the third resistor 393 is coupled to the high voltage end (eg, the power supply end), and the second end is coupled to the first end of the second switch 371 and the control end of the first switch 370; The second end of the switch 371 is coupled to the low voltage terminal. The principle of the vertical sync signal detecting module 330 for detecting the vertical sync signal is: (1) if a vertical sync signal is input to the vertical sync signal port 埠 3104, the anode and the cathode of the diode 351 have a cross. Pressing, the diode 351 is turned on, and the capacitor 341 is charged. When the capacitor 341 is charged to the first terminal, the voltage level is sufficiently high, so that the voltage level of the control terminal of the second switch 371 is also high enough to be turned on. The second switch 371, the control terminal of the first switch 370 is connected to the low voltage terminal through the second switch 371, so that the first switch 370 is not turned on, and the first resistor 391 connected to the horizontal synchronization signal path 385 is therefore not connected. The second resistor 392 is connected in parallel; (2) if there is no vertical sync signal input vertical sync signal connection 埠 3104, the anode and cathode of the diode 351 do not have a voltage across the cathode, so that the diode 351 is not turned on, and the capacitor 341 cannot During charging, the voltage level of the first end of the capacitor 341 cannot be raised, so that the voltage level of the control terminal of the second switch 371 cannot be raised, so that the second switch 371 is not turned on, and the control terminal of the first switch 370 is Through the third resistor 393 Connected to the high voltage terminal, a control terminal of the first switch 370 so as to have views of a high voltage after dividing, and thus the first switch 370 is turned on, a second lead 392 through a first resistor The switch 370 is coupled between the horizontal sync signal path 385 and a low voltage terminal, and the first resistor 391 and the second resistor 392 connected to the horizontal sync signal path 385 are connected in parallel.

In the above case (1), since the vertical sync signal is input to the vertical sync signal port 埠 3104, the vertical sync signal detecting module 330 can determine that the corresponding external video source belongs to a five-wire (RGBHV) external video source, wherein the vertical sync The signal is input separately from the horizontal sync signal. In the above case (2), since the vertical sync signal is input to the horizontal sync signal port 1053105 instead of the vertical sync signal port 埠3104, the vertical sync signal detecting module 330 can determine that the corresponding external video source belongs to the four-wire type (RGB). H+V.) An external video source in which the vertical sync signal and the horizontal sync signal are input with the same signal.

Please refer to Figure 2 and Figure 3, refer to Figure 4. Figure 4 is a flow diagram of a display control method 400 in accordance with an embodiment of the present invention. The steps are as follows: Step 401: When the external video source is coupled to the video connection interface, is the vertical synchronization signal input to the horizontal synchronization signal connection for receiving the horizontal synchronization signal? If yes, proceed to step 402; if no, proceed to step 403; step 402: determine that the four-wire external video source turns on the first switch coupled between the second resistor and the low voltage terminal to connect the second resistor Between the horizontal sync signal path and the low voltage terminal, and in parallel with the first resistor connected between the horizontal sync signal path and the low voltage terminal.

Step 403: determining that the five-wire external video source does not conduct the first switch coupled between the second resistor and the low voltage terminal, so that the second resistor cannot be connected between the horizontal synchronization signal path and the low voltage terminal. Therefore, the first resistor connected between the horizontal sync signal path and the low voltage terminal is not connected in parallel.

The value of the first resistance as mentioned in the above FIGS. 2, 3, and 4 may be, for example, 2.2 kΩ, and the value of the second resistance may be, for example, 75 Ω. By the method of the embodiment of FIG. 4, Achieve the same video interface and compatibility with four-wire external video sources and five-wire external video sources.

The invention is applicable to video connection interfaces such as D-sub, VGA connector, DB, HDB and HD which are commonly used in the industry. Take the 15-pin D-Sub 15 as an example. The first, second, third, 14 and 13 pins are red video signal port, green video signal port, blue video signal port, vertical sync signal connection.埠 and horizontal sync signal connection 埠, in the prior art, the impedance value (75 Ω) required to be coupled by the horizontal sync signal path (for receiving the horizontal sync signal and the vertical sync signal) corresponding to the four-wire external video source Different from the impedance value (2.2kΩ) required for the horizontal sync signal path corresponding to the five-wire external video source, the display user is forced to set two sets of video for the four-wire external video source and the five-wire external video source. Connect the interface, or use the adapter, a monitor can be connected to a different external video source. This not only causes inconvenience to the user, but also increases the hardware cost, which is not conducive to product specifications. By using the display and control method of the embodiment of the invention, only a single video connection interface can be compatible with the three-wire, four-wire and five-wire external video sources, and the connection interface of the display can be simplified. In addition, if the display disclosed in the embodiment of FIG. 3 is further used, the external video source is automatically determined to be a four-wire external video source or a five-wire external video source, and the internal impedance is automatically adjusted to meet the standard specifications.

In summary, the present invention is useful for enhancing the experience of users in the field and improving the hardware specifications of the products.

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

200‧‧‧ display

210‧‧‧Video Connection Interface

220‧‧‧Internal wiring interface

2201‧‧‧Red video signal endpoint

2202‧‧‧Green video signal endpoint

2203‧‧‧Blue Video Signal Endpoint

2204‧‧‧Vertical sync signal endpoint

2205‧‧‧ horizontal sync signal endpoint

281‧‧‧Red video signal path

282‧‧‧Green video signal path

283‧‧‧Blue video signal path

284‧‧‧Vertical sync signal path

285‧‧‧ horizontal sync signal path

291‧‧‧First resistance

292‧‧‧second resistance

270‧‧‧ first switch

2101‧‧‧Red video signal port埠

2102‧‧‧Green Video Signal Connection埠

2103‧‧‧Blue Video Signal Connection埠

2104‧‧‧Vertical Synchronous Signal Connection埠

2105‧‧‧Horizontal Synchronous Signal Connection埠

Claims (11)

A display comprising: a video connection interface comprising: a red video signal port for receiving a red video signal; a green video signal port for receiving a green video signal; and a blue video signal port; For receiving a blue video signal; a vertical sync signal port for receiving a vertical sync signal; and a horizontal sync signal port for receiving a horizontal sync signal and/or the vertical sync signal; an internal wiring The interface includes a red video signal endpoint, a green video signal endpoint, a blue video signal endpoint, a vertical sync signal endpoint and a horizontal sync signal endpoint; and a red video signal path, including: a first The second end is coupled to the red video signal port; and the second end is coupled to the red video signal port; the green video signal path includes: a first end coupled to the green video signal end And a second end coupled to the green video signal port; a blue video signal path comprising: a first end coupled to the blue video signal The signal end point and the second end are coupled to the blue video signal port; a vertical sync signal path includes: a first end coupled to the vertical sync signal end point, and a second end The first synchronous signal path is coupled to the vertical synchronous signal port, and includes: a first end coupled to the horizontal synchronizing signal end, and a second end coupled to the horizontal synchronizing signal port; a first resistor comprising: a first end coupled to the horizontal synchronizing signal And a second end coupled to a low voltage terminal; a second resistor comprising: a first end coupled to the horizontal sync signal path; and a second end; and a first switch The first end is coupled to the second end of the second resistor; the second end is coupled to the low voltage end; and a control end is configured to control whether the first switch is turned on; When a four-wire external video source is coupled to the video connection interface, the four-wire external video source provides the vertical synchronization signal to the horizontal synchronization signal port, and the vertical synchronization is not provided according to the vertical synchronization signal connection port. The signal is electrically connected to the first switch, and the second resistor is coupled between the low voltage terminal and the horizontal synchronization signal path through the first switch, so that the first resistor is connected in parallel with the second resistor; An external video source is coupled to the video connection interface The five-wire system provides an external video source to the vertical synchronizing signal to the vertical sync signal port, the vertical synchronization signal port provided in the switch according to the first vertical synchronization signal is not turned on. The display device of claim 1, further comprising a vertical sync signal detecting module, comprising: a capacitor comprising: a first end; and a second end coupled to the low voltage end; a third resistor , comprising: a first end coupled to a high voltage end; and a second end coupled to the control end of the first switch; a diode comprising: an anode coupled to the vertical sync signal path; and a cathode coupled to the first of the capacitor And a second switch, comprising: a first end coupled to the second end of the third resistor; a second end coupled to the low voltage end; and a control end coupled to the The cathode of the diode. The display of claim 2, wherein the first switch and the second open relationship are N-type MOS transistors. The display of claim 1, wherein the resistance of the first resistor is much greater than the resistance of the second resistor. The display device of claim 1, wherein the video connection interface is a D-sub video connection interface, an HD video connection interface, a DB video connection interface, or an HDB video connection interface. A display control method, wherein the display comprises a video connection interface, an internal wiring interface, a horizontal synchronization signal path, a first resistor, a second resistor and a first switch; and one of the video connection interfaces is horizontally synchronized. The first resistor is coupled between the horizontal synchronization signal path and a low voltage terminal, and the second resistor is coupled to the horizontal synchronization signal end of the internal wiring interface. The second resistor is coupled between the horizontal synchronization signal path and a low voltage terminal. The second end of the first switch is coupled to the low voltage end, and the method includes: when a four-wire external video is coupled between the first horizontal end of the first switch and the first end of the first switch The source is coupled to the video connection interface, and the four-wire external video source is provided When a vertical sync signal is connected to the horizontal sync signal port, the vertical sync signal is not provided according to the vertical sync signal port, and the control terminal of the first switch is controlled to turn on the first switch, so that the second resistor transmits the second resistor. The first switch is coupled between the low voltage terminal and the horizontal synchronization signal path such that the first resistor is connected in parallel with the second resistor. The method of claim 6, wherein the controlling the first switch to turn the first switch on is: a graphical user interface (GUI), a toggle switch, an integrated circuit, or A single-pole switch controls the control terminal of the first switch to turn the first switch on. The method of claim 6, wherein the internal wiring interface further comprises a vertical sync signal end point coupled to a vertical sync signal port of the video connection interface via a vertical sync signal path, the display further comprising a vertical The synchronous signal detecting module is coupled to the vertical synchronous signal path and the control end of the first switch, wherein the control terminal of the first switch controls the first switch to be turned on, and the vertical synchronization signal is detected. The module controls the control end of the first switch to turn on the first switch. A display control method, wherein the display comprises a video connection interface, an internal wiring interface, a horizontal synchronization signal path, a first resistor, a second resistor and a first switch; and one of the video connection interfaces is horizontally synchronized. The first resistor is coupled between the horizontal synchronization signal path and a low voltage terminal, and the second resistor is coupled to the horizontal synchronization signal end of the internal wiring interface. The second resistor is coupled between the horizontal synchronization signal path and a low voltage terminal. The second end of the first switch is coupled to the low voltage end, and the method includes: when a five-wire external video is coupled between the horizontal signal path and the first end of the first switch The source is coupled to the video connection interface, and the five-wire external video source provides a vertical synchronization signal to one of the vertical connection signals of the video connection interface, according to the vertical The vertical synchronization signal is provided in the step signal connection port, and one of the control terminals of the first switch is controlled to make the first switch non-conductive. The method of claim 9, wherein the controlling the first switch to make the first switch non-conductive is: a graphical user interface (GUI), a toggle switch, an integrated circuit, Or a single-pole switch controlling the control end of the first switch to disable the first switch. The method of claim 9, wherein the internal wiring interface further comprises a vertical sync signal end point coupled to a vertical sync signal port of the video connection interface via a vertical sync signal path, the display further comprising a vertical The synchronous signal detecting module is coupled to the vertical synchronous signal path and the control end of the first switch, wherein the control terminal of the first switch is configured to disable the first switch, and the vertical synchronization signal is detected. The measuring module controls the control end of the first switch to make the first switch non-conductive.