CN218826157U

CN218826157U - Backlight control circuit

Info

Publication number: CN218826157U
Application number: CN202222678733.3U
Authority: CN
Inventors: 孙瑛; 潘超杰; 刘统旭; 魏从明; 王绍财; 李方健; 刘志旭; 宋治广
Original assignee: Qingdao Saiwei Electronic Information Service Co ltd
Current assignee: Qingdao Saiwei Electronic Information Service Co ltd
Priority date: 2022-10-11
Filing date: 2022-10-11
Publication date: 2023-04-07
Anticipated expiration: 2032-10-11

Abstract

The utility model discloses a control circuit is shaded is applied to and adopts Local Dimming mode to carry out the LCD screen of adjusting in a poor light, and this circuit includes: the current limiting unit is used for ensuring that the current of the external power supply does not exceed the preset highest current; the voltage conversion unit is used for converting the external power supply into a driving power supply which accords with preset voltage and supplying power to a power panel and a backlight driving chip of the liquid crystal display based on the driving power supply; the current limiting unit is connected between the external power supply and the input end of the voltage conversion unit in series, and the output end of the voltage conversion unit is connected with the power panel and the backlight driving chip respectively, so that the backlight lamp bar of the liquid crystal screen is lightened under the condition that the mainboard is not connected, and the efficiency of liquid crystal screen backlight fault maintenance is improved.

Description

Backlight control circuit

Technical Field

The application relates to the technical field of liquid crystal televisions, in particular to a backlight control circuit.

Background

The Local Dimming Local backlight dynamic regulation technology is a technology applied to backlight control of a liquid crystal television, and the working mechanism of the Local Dimming Local backlight dynamic regulation technology is to dynamically regulate the backlight brightness of a corresponding area according to the brightness degree of image content, so that a bright image is brighter and a dark image is darker, and the effects of improving dynamic contrast and reducing power consumption are achieved by combining image compensation.

In the process of maintaining the backlight fault of the liquid crystal display, sometimes the main board is not connected to forcibly lighten the backlight lamp strip so as to judge whether the backlight fault is caused by the main board. However, the Local Dimming circuit is connected with the main board through the SPI bus to realize Dimming control, and the traditional maintenance idea of forcibly lighting the backlight cannot realize forcibly lighting the backlight lamp bar, so that the maintenance efficiency needs to be improved.

Therefore, how to provide a backlight control circuit to realize that a main board is not connected to a liquid crystal screen adopting a Local Dimming mode to forcibly light a backlight lamp bar is a technical problem to be solved at present.

SUMMERY OF THE UTILITY MODEL

The utility model provides a control circuit is shaded for realize not connecting the mainboard on the LCD screen that adopts Local Dimming mode and force the lamp strip in a poor light of lighting.

The circuit is applied to a liquid crystal screen which adopts a Local Dimming mode to carry out backlight adjustment, and comprises:

the current limiting unit is used for ensuring that the current of the external power supply does not exceed the preset highest current;

the voltage conversion unit is used for converting the external power supply into a driving power supply which accords with preset voltage, and supplying power to a power panel and a backlight driving chip of the liquid crystal screen based on the driving power supply so as to light a backlight lamp bar of the liquid crystal screen under the condition that a mainboard of the liquid crystal screen is not connected;

the current limiting unit is connected between the external power supply and the input end of the voltage conversion unit in series, and the output end of the voltage conversion unit is connected with the power panel and the backlight driving chip respectively.

In some embodiments, the backlight driving chip includes a pin BL-ON/OF, a pin BL-ADJUST, a pin BL _ IPWM, and a pin LD _ VSYNC, and the power board includes a pin STANDBY, where the pin BL-ON/OF is used for performing backlight ON-off control, the pin BL-ADJUST is used for performing BL-ADJUST dimming mode control, the pin BL _ IPWM is used for performing BL _ IPWM dimming mode control, the pin LD _ VSYNC is used for performing multi-partition backlight frame synchronization signal control, and the pin STANDBY is used for performing overall ON-off control.

In some embodiments, the output terminal OF the voltage transformation unit is connected to the pin BL-ON/OF, the pin BL-ADJUST, the pin LD _ VSYNC, and the pin STANDBY when the dimming mode is BL-ADJUST, and the output terminal OF the voltage transformation unit is connected to the pin BL-ON/OF, the pin BL _ IPWM, the pin LD _ VSYNC, and the pin STANDBY when the dimming mode is BL _ IPWM.

In some embodiments, the output terminal OF the voltage conversion unit is connected to the pin BL-ON/OF, the pin LD _ VSYNC, and the pin STANDBY, respectively, when the dimming mode is SPI bus dimming.

In some embodiments, the current limiting unit is a resistor.

In some embodiments, the external power supply is a 5-12V DC power supply, and the resistor has a specification of 10-22 Ω/2W.

In some embodiments, the preset voltage is 3.3V.

In some embodiments, the voltage conversion unit is a LV1117-3.3V voltage converter.

In some embodiments, the backlight driving chip is of type IW7027.

In some embodiments, the model of the CPU on the motherboard is MSD6a838.

By applying the technical scheme, in the liquid crystal screen which adopts a Local Dimming mode to carry out backlight adjustment, the backlight control circuit comprises: the current limiting unit is used for ensuring that the current of the external power supply does not exceed the preset highest current; the voltage conversion unit is used for converting the external power supply into a driving power supply which accords with preset voltage and supplying power to a power panel and a backlight driving chip of the liquid crystal display based on the driving power supply; the current limiting unit is connected in series between the external power supply and the input end of the voltage conversion unit, and the output end of the voltage conversion unit is connected with the power panel and the backlight driving chip respectively, so that the backlight lamp bar of the liquid crystal screen is lightened under the condition that the main board is not connected, and the backlight fault maintenance efficiency of the liquid crystal screen is improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 shows a schematic structural diagram of a backlight control circuit according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a backlight control circuit according to another embodiment of the present invention;

fig. 3 is a schematic diagram illustrating a circuit principle of backlight driving by using Local Dimming in the prior art.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Fig. 3 is a schematic diagram of a circuit principle of backlight driving by a Local Dimming method in the prior art, and the control principle is as follows:

the liquid crystal screen can be arranged ON a television or a display, when the television or the display is started, a 220V alternating current power supply is input, firstly, a standby power supply is started, about 12V voltage is output at the moment, 5Vstb is output to a CPU50 ON a mainboard through a fully integrated high-frequency synchronous rectification buck switch converter of an MP1658 built-in power MOSFET, the CPU50 sends an ON/OFF starting signal to a power circuit according to the setting condition of the whole machine, the starting signal is fed back to a PFC + LLC circuit control chip 70 through a feedback loop, the PFC + LLC circuit control chip 70 starts a PFC circuit to enable the rectified voltage to be raised to about 390V, and 12V, 18V and 42V are converted and output through a transformer through an LLC circuit; when the CPU50 sends out the backlight switch control Signal (SW), the BOST boost circuit control chip 80 is activated, and the 42V voltage is boosted to 54V.

If the backlight driving chip 40 adopts a 16-path Local Dimming scheme, after SW is changed to a high level, a 12V voltage provides VCC to the backlight driving chip 40, the backlight driving chip 40 starts to work, the CPU50 controls a register of the backlight driving chip 40 through an SPI bus and provides an LD _ VSYNC signal to light the backlight, the backlight driving chip 40 outputs a signal to control 8 switching MOSFETs at the negative end of the backlight light bar 60 to turn on or off the switching MOSFETs, and the FB1 pin controls the BOST boost circuit control chip 80 to supply the backlight light bar 60 with a supply voltage meeting the requirements. After the backlight is lightened, the CPU50 updates the brightness data of each backlight partition in real time through the SPI according to the picture brightness, and the backlight driving chip 40 changes the current of each partition LED in the backlight lamp bar 60 in real time, so that the Local Dimming function is realized.

The embodiment of the application provides a backlight control circuit, is applied to the LCD screen that adopts Local Dimming mode to carry out backlight adjustment, as shown in FIG. 1, the circuit includes:

the current limiting unit 10 is used for enabling the current of an external power supply not to exceed a preset highest current;

the voltage conversion unit 20 is used for converting an external power supply into a driving power supply meeting a preset voltage, and supplying power to the power panel 30 and the backlight driving chip 40 of the liquid crystal screen based on the driving power supply so as to light a backlight light bar of the liquid crystal screen without connecting a mainboard of the liquid crystal screen;

the current limiting unit 10 is connected in series between the external power supply and the input terminal of the voltage transforming unit 20, and the output terminal of the voltage transforming unit 20 is connected to the power supply board 30 and the backlight driving chip 40, respectively.

In this embodiment, since the backlight control circuit in this application is used to maintain the backlight fault of the liquid crystal display, the SPI bus between the CPU50 and the backlight driver chip 40 on the motherboard and the motherboard power supply plug wire need to be unplugged in advance to realize that the motherboard is not connected. When backlight fault maintenance is carried out, an external power supply is connected to the power panel 30 and the backlight driving chip 40 of the liquid crystal screen through the current limiting unit 10 and the voltage conversion unit 20, and a driving power supply which meets preset voltage is provided for the power panel 30 and the backlight driving chip 40, so that the backlight lamp bar is forcibly lightened without connecting a mainboard.

In order to ensure the reliability OF the backlight driving chip 40 and the power board 30, in some embodiments OF the present application, the backlight driving chip 40 includes a pin BL-ON/OF, a pin BL-ADJUST, a pin BL _ IPWM, and a pin LD _ VSYNC, and the power board 30 includes a pin STANDBY, where the pin BL-ON/OF is used for performing backlight ON-off control, the pin BL-ADJUST is used for performing BL-ADJUST dimming mode control, the pin BL _ IPWM is used for performing BL _ IPWM dimming mode control, the pin LD _ VSYNC is used for performing multi-partition backlight frame synchronization signal control, and the pin STANDBY is used for performing overall machine ON-off control.

In this embodiment, when the lcd panel normally works, the control signals OF the pin BL-ON/OF, the pin BL-ADJUST, the pin BL _ IPWM, the pin LD _ VSYNC, and the pin STANDBY are all from the CPU50.

In order to ensure the reliability of the backlight driving chip 40, in some embodiments of the present application, the backlight driving chip 40 further includes:

a pin LD _ CS, a chip selection signal and a slave equipment enabling signal are controlled by the master equipment;

pin LD _ SDI, master device data input, slave device data output;

pin LD _ SDO, master device data output, slave device data input;

pin LD _ SCLK, a clock signal, generated by the master device;

pin Error, error status output pin, when the circuit works abnormally, output low level to be sent to CPU50.

For reliable backlight control, in some embodiments OF the present application, as shown in fig. 2, the output end OF the voltage conversion unit 20 is connected to the pin BL-ON/OF, the pin BL-ADJUST, the pin LD _ VSYNC, and the pin STANDBY respectively when the dimming mode is BL-ADJUST, and the output end OF the voltage conversion unit 20 is connected to the pin BL-ON/OF, the pin BL _ IPWM, the pin LD _ VSYNC, and the pin STANDBY respectively when the dimming mode is BL _ IPWM.

For reliable backlight control, in some embodiments OF the present application, the output terminal OF the voltage conversion unit 20 is connected to the pin BL-ON/OF, the pin LD _ VSYNC, and the pin STANDBY respectively when the dimming mode is SPI bus dimming.

In this embodiment, if the dimming mode is SPI bus dimming, the output terminal of the voltage conversion unit 20 is not connected to the pin BL-ADJUST or the pin BL _ IPWM.

In order to ensure the reliability of the circuit, in some embodiments of the present application, the current limiting unit is a resistor.

Those skilled in the art can use other types of current limiting elements according to actual needs, which does not affect the scope of protection of the present application.

In order to ensure the reliability of the circuit, in some embodiments of the present application, the external power supply is a 5-12V dc power supply, and the specification of the resistor is 10-22 Ω/2W.

In order to ensure the reliability of the circuit, in some embodiments of the present application, the predetermined voltage is 3.3V.

In order to ensure the reliability of the circuit, in some embodiments of the present application, the voltage conversion unit is an LV1117-3.3V voltage converter.

Those skilled in the art can use other types of voltage converting elements according to actual needs, which does not affect the scope of the present application.

In order to ensure the reliability of the circuit, in some embodiments of the present application, the model of the backlight driving chip is IW7027.

Those skilled in the art can use other types of backlight driving chips according to actual needs, which does not affect the scope of the present application.

In order to ensure the reliability of the circuit, in some embodiments of the present application, the model of the CPU on the motherboard is MSD6a838.

Those skilled in the art can use other types of CPUs according to actual needs, which does not affect the scope of the present application.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature, and in the description of the invention, "plurality" means two or more unless explicitly specifically defined otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "enter", "connect", and the like are to be construed broadly, e.g., as a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood according to specific situations by those of ordinary skill in the art.

In the description of the present specification, reference to the description of "one embodiment," "some embodiments," "an example," "a specific example," or "some examples" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although embodiments of the present invention have been shown and described, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that changes, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art without departing from the principles and spirit of the present invention.

Claims

1. The utility model provides a control circuit is shaded, is applied to and adopts LocalDimming mode to carry out the LCD screen that adjusts in a poor light, its characterized in that, the circuit includes:

the current limiting unit is connected in series between the external power supply and the input end of the voltage conversion unit, and the output end of the voltage conversion unit is respectively connected with the power panel and the backlight driving chip.

2. The circuit OF claim 1, wherein the backlight driver chip comprises a pin BL-ON/OF, a pin BL-ADJUST, a pin BL _ IPWM, and a pin LD _ VSYNC, and the power board comprises a pin STANDBY, wherein the pin BL-ON/OF is used for performing backlight ON-off control, the pin BL-ADJUST is used for performing BL-ADJUST dimming mode control, the pin BL _ IPWM is used for performing BL _ IPWM dimming mode control, the pin LD _ VSYNC is used for performing multi-partition backlight frame synchronization signal control, and the pin STANDBY is used for performing overall ON-off control.

3. The circuit as claimed in claim 2, wherein the output terminal OF the voltage transforming unit is connected to the pins BL-ON/OF, BL-ADJUST, LD _ VSYNC, and STANDBY, respectively, when the dimming mode is BL-ADJUST, and the output terminal OF the voltage transforming unit is connected to the pins BL-ON/OF, BL _ IPWM, LD _ VSYNC, and STANDBY, respectively, when the dimming mode is BL _ IPWM.

4. The circuit OF claim 2, wherein the output OF the voltage conversion unit is connected to pin BL-ON/OF, pin LD _ VSYNC, and pin STANDBY, respectively, when the dimming mode is SPI bus dimming.

5. The circuit of claim 1, wherein the current limiting unit is a resistor.

6. The circuit of claim 5, wherein the external power supply is a 5-12V DC power supply, and the resistor has a specification of 10-22 Ω/2W.

7. The circuit of claim 1, wherein the predetermined voltage is 3.3V.

8. The circuit of claim 7, wherein the voltage conversion unit is a LV1117-3.3V voltage converter.

9. The circuit of claim 1, wherein the backlight driver chip is model IW7027.

10. The circuit of claim 1, wherein the CPU on the motherboard is model number MSD6a838.