Backlight driving circuit and liquid crystal display device

Abstract

The utility model relates to a backlight driving circuit and a liquid crystal display device, and relates to the technical field of display, the backlight driving circuit comprises a backlight driving chip, a backlight lamp set and a shunt circuit located between the backlight driving chip and the backlight lamp set, and the shunt circuit is used for receiving a control signal and shunting current input into the backlight lamp set according to the control signal. Therefore, the current input to the positive end of the backlight lamp group can be partially drained, and the input current of the backlight lamp group is reduced, so that the backlight display brightness is reduced, and the display uniformity of the same liquid crystal display device under low brightness is improved.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of display, in particular to a backlight driving circuit and a liquid crystal display device. BACKGROUND

[0002] The backlight driving circuit of the liquid crystal display device includes two kinds: the first kind is multi-channel backlight driving, which adopts current source type circuit, each channel can be controlled individually, has high precision and good consistency between devices, and there is no inconsistency in brightness; the second kind is single-channel backlight driving, which generally adopts resistance feedback type, all channels are connected together and return to the backlight driving chip; due to the use of resistance feedback type circuit, there is a difference in the consistency of brightness of the liquid crystal display device at low brightness, which leads to inconsistent display effect of different device individuals at low brightness in the same type of liquid crystal display device. This brightness inconsistency problem is mainly caused by the performance limitation of the driving chip itself. At low brightness, the driving current is small and the control precision is difficult to guarantee, so it is difficult to realize uniform backlight brightness between different device individuals.

[0003] In addition, some chips cannot accept low duty ratio PWM (Pulse-Width Modulation) signals and guarantee stable output.

[0004] Therefore, how to improve the backlight brightness deviation of different liquid crystal display devices at low brightness in the same type of liquid crystal display device has become a technical problem to be solved by those skilled in the art. CONTENT OF THE INVENTION

[0005] In order to solve the above technical problems, the present disclosure provides a backlight driving circuit and a liquid crystal display device for improving the backlight brightness deviation of different liquid crystal display devices at low brightness in the same type of liquid crystal display device.

[0006] In a first aspect, the present disclosure provides a backlight driving circuit, comprising: a backlight driving chip and a backlight lamp group; the backlight driving chip comprises a commutation end and a feedback end, the backlight lamp group comprises a positive end and a negative end, the commutation end of the backlight driving chip is electrically connected with the positive end of the backlight lamp group, and the feedback end of the backlight driving chip is electrically connected with the negative end of the backlight lamp group.

[0007] The backlight driving circuit further comprises a shunt circuit, which is used for receiving a control signal and performing shunt processing on the current input to the backlight lamp group according to the control signal.

[0008] Optionally, the shunt circuit comprises a first end, a second end and a third end, the first end of the shunt circuit is configured to receive the control signal, the second end of the shunt circuit is electrically connected with the positive end of the backlight lamp set and the commutation end of the backlight driving chip, and the third end of the shunt circuit is electrically connected with the negative end of the backlight lamp set and the feedback end of the backlight driving chip.

[0009] Optionally, the shunt circuit comprises a switching element, a control electrode of the switching element is electrically connected with the control signal, a first electrode of the switching element is electrically connected with the positive end of the backlight lamp set and the commutation end of the backlight driving chip, and a second electrode of the switching element is electrically connected with the negative end of the backlight lamp set and the feedback end of the backlight driving chip.

[0010] Optionally, the switching element comprises a triode or a field effect transistor.

[0011] Optionally, the shunt circuit comprises a first resistor, one end of the first resistor is electrically connected with the second electrode of the switching element, and the other end of the first resistor is electrically connected with the negative end of the backlight lamp set and the feedback end of the backlight driving chip.

[0012] Optionally, the shunt circuit comprises a filter circuit, a first end of the filter circuit is configured to receive the control signal, and a second end of the filter circuit is electrically connected with the control electrode of the switching element.

[0013] Optionally, the filter circuit comprises a first capacitor and a second resistor, one end of the second resistor is configured to receive the control signal, the other end of the second resistor is electrically connected with the control electrode of the switching element and the first capacitor, and the other end of the first capacitor is grounded.

[0014] Optionally, the backlight driving chip is a single-channel backlight driving chip.

[0015] Optionally, the control signal comprises a PWM dimming signal.

[0016] In a second aspect, based on the same inventive concept, the present disclosure further provides a liquid crystal display device comprising the backlight driving circuit according to the first aspect.

[0017] Compared with the prior art, the technical scheme provided by the embodiments of the present disclosure has the following advantages:

[0018] The backlight driving circuit provided by the present disclosure has a simple circuit structure and low cost. By partially shunting the current input to the positive end of the backlight lamp set, precise control of the backlight display effect can be achieved, which is conducive to reducing the objective condition limitation of insufficient duty cycle of the backlight driving chip itself and improving the display uniformity of the same liquid crystal display device under low brightness. BRIEF DESCRIPTION OF DRAWINGS

[0019] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate embodiments consistent with the present disclosure and serve to explain the principles of the present disclosure together with the specification.

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the accompanying drawings required to be used in the embodiments or prior art description will be briefly introduced. Obviously, those skilled in the art can obtain other drawings according to these drawings without any creative effort.

[0021] Figure 1 The connection schematic diagram of the backlight driving circuit in the prior art is shown.

[0022] Figure 2 The connection schematic diagram of the backlight driving circuit provided by the embodiments of the present disclosure is shown.

[0023] Figure 3 The amplification schematic diagram of the shunt circuit is shown. Figure 2

[0024] Figure 4 The schematic diagram of the liquid crystal display device provided by the embodiments of the present disclosure is shown. DETAILED DESCRIPTION

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the accompanying drawings required to be used in the embodiments or prior art description will be briefly introduced. Obviously, those skilled in the art can obtain other drawings according to these drawings without any creative effort.

[0026] In the following description, many specific details are set forth in order to fully understand the present disclosure, but the present disclosure can also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some of the embodiments of the present disclosure, not all the embodiments.

[0027] Figure 1 The connection schematic diagram of the backlight driving circuit in the prior art is shown. Please refer to Figure 1 The backlight driving circuit 100' includes a backlight driving chip 10', the VIN' port of the backlight driving chip is connected to a power supply 11', the SW' port of the backlight driving chip is connected to the positive end of a backlight lamp set 20', the negative end of the backlight lamp set 20' is connected to the FB' port of the backlight driving chip, the CTRL' port of the backlight driving chip is connected to a chip or circuit for controlling dimming, and the GND' port of the backlight driving chip is grounded.

[0028] ​Taking the AW9967DNR type chip as an example, the AW9967DNR type single-channel backlight driving chip can accept the PWM dimming with the minimum duty cycle of 0.3%. When the backlight driving chip 10' is at the minimum duty cycle of 0.3%, the voltage of the FB' port is 600 μV, which is very small. Due to the process deviation, the voltage value of the FB' port is normally distributed, most of which is concentrated around 600 μV, but part of the FB' port voltage distribution of the backlight driving chip 10' is slightly far away. When the backlight lamp set 20' displays at high brightness, the influence of the deviation voltage value on the brightness is very small, but when the backlight lamp set 20' displays at low brightness, the influence of the deviation voltage value on the brightness is large, and the display uniformity of the display module corresponding to the same type of backlight driving chip 10' under low brightness condition is not uniform.

[0029] Based on the above problems, Figure 2 Fig. 1 shows a backlight driving circuit connection diagram provided by an embodiment of the present disclosure, Figure 3 Fig. 2 shows a backlight driving circuit connection diagram provided by an embodiment of the present disclosure, Figure 2 Fig. 3 shows an amplification diagram of a shunt circuit, please refer to Figure 2 and Figure 3 In an optional embodiment provided by the present disclosure, the backlight driving circuit 100 includes a backlight driving chip 10 and a backlight lamp set 20. The backlight driving chip 10 includes a commutation end SW and a feedback end FB, and the backlight lamp set 20 includes a positive end and a negative end. The commutation end SW of the backlight driving chip 10 is electrically connected with the positive end of the backlight lamp set 20, and the feedback end FB of the backlight driving chip 10 is electrically connected with the negative end of the backlight lamp set 20. The backlight lamp set 20 includes a plurality of LED lamps connected in series, and the positive end of the backlight lamp set 20 refers to the current input end of the LED lamp.

[0030] The backlight driving circuit 100 further includes a shunt circuit 30, which is used to receive a control signal and perform shunt processing on the current input to the backlight lamp set 20 according to the control signal. Optionally, the shunt circuit 30 includes a first end 311, a second end 312 and a third end 313. The first end 311 of the shunt circuit 30 is used to receive the control signal. The second end 312 of the shunt circuit 30 is electrically connected with the positive end of the backlight lamp set 20 and the commutation end SW of the backlight driving chip 10. The third end 313 of the shunt circuit 30 is electrically connected with the negative end of the backlight lamp set 20 and the feedback end FB of the backlight driving chip 10. Optionally, the control signal includes a PWM dimming signal.

[0031] Specifically, the backlight driving circuit 100 includes a backlight driving chip 10, a shunt circuit 30, and a backlight lamp set 20. The backlight driving chip 10 includes a power supply end VIN, a commutation end SW, a control end CTRL, a feedback end FB, and a ground end GND. The power supply end VIN is used to connect an external power supply 11 to provide a working voltage for the backlight driving chip 10. The control end CTRL is externally connected to a pulse width modulation signal generator and a CABC (Content Adaptive Brightness Control), which is used to realize fine adjustment of the brightness of the backlight lamp set 20 to improve the display effect.

[0032] The commutation end SW of the backlight driving chip 10 is connected to the backlight lamp set 20. In an optional embodiment provided in the present disclosure, the commutation end SW provides stable voltage and current for the backlight lamp set 20 through continuous charging and discharging actions. The commutation end SW is also connected to the shunt circuit 30. Since the minimum duty cycle that can be accepted by the backlight driving chip 10 is not low enough, the current output to the backlight lamp set 20 cannot be low enough, and thus the minimum screen brightness of the liquid crystal display device cannot meet the customer's requirements. By connecting the second end 312 of the shunt circuit 30 to the commutation end SW of the backlight driving chip 10 and the positive end of the backlight lamp set 20, the brightness of the backlight lamp set 20 can be reduced through the shunt effect of the shunt circuit 30, and precise control of the brightness can be realized.

[0033] The feedback end FB of the backlight driving chip 10 is electrically connected to the negative end of the backlight lamp set 20, and is used to receive a feedback voltage. According to the feedback voltage signal, the output is adjusted to enable the backlight lamp set 20 to obtain stable and accurate voltage supply. The feedback end FB is also connected to the third end 313 of the shunt circuit 30, and is used to divert part of the current in the shunt circuit 30 to the feedback end FB to reduce the input current of the positive end of the backlight lamp set 20 to reduce the brightness of the backlight display.

[0034] The ground end GND is used to ensure the stability of the circuit and prevent damage to the circuit caused by static electricity.

[0035] In this way, in the single-channel backlight driving circuit 100, by providing the backlight driving circuit 100 with the shunt circuit 30, the shunt circuit 30 can divert part of the current input to the positive end of the backlight lamp set 20 to the feedback end FB of the backlight driving chip 10 to reduce the input current of the positive end of the backlight lamp set 20, thereby reducing the objective condition limitation that the minimum screen brightness cannot meet the customer's requirements due to the insufficient low duty cycle of the backlight driving chip 10 itself, and improving the display uniformity of the same liquid crystal display device under low brightness.

[0036] In an alternative embodiment provided in the present disclosure, the shunt circuit 30 comprises a switching element 31, a control electrode of the switching element 31 is configured to receive a control signal, and the control signal comprises a PWM dimming signal. A first electrode C of the switching element 31 is electrically connected to a positive terminal of the backlight lamp set 20 and a commutation terminal SW of the backlight driving chip 10, and a second electrode E of the switching element 31 is electrically connected to a negative terminal of the backlight lamp set 20 and a feedback terminal FB of the backlight driving chip 10.

[0037] Specifically, the backlight driving circuit 100 comprises a shunt circuit 30, a first terminal 311 of the shunt circuit 30 is configured to receive a PWM dimming signal, a second terminal 312 of the shunt circuit 30 is electrically connected to a positive terminal of the backlight lamp set 20 and a commutation terminal SW of the backlight driving chip 10, and a third terminal 313 of the shunt circuit 30 is electrically connected to a negative terminal of the backlight lamp set 20 and a feedback terminal FB of the backlight driving chip 10. The shunt circuit 30 comprises a switching element 31, the switching element 31 comprises a control electrode B, a first electrode C and a second electrode E, the control electrode B of the switching element 31 is configured to receive the PWM dimming signal, the PWM dimming signal is configured to control the switching element 31 to work in an amplification region, the first electrode C of the switching element 31 is electrically connected to the commutation terminal SW of the backlight driving chip 10 and the positive terminal of the backlight lamp set 20, and the second electrode E of the switching element 31 is electrically connected to the feedback terminal FB of the backlight driving chip 10 and the negative terminal of the backlight lamp set 20. When the switching element 31 works in the amplification region, a shunt branch (a branch formed by the electrical connection between the second terminal 312 and the third terminal 313 when the switching element 31 works in the amplification region) can be provided for the input current of the backlight lamp set 20; in this way, by connecting the switching element 31 with the backlight driving chip 10 and the backlight lamp set 20, when the switching element 31 works in the amplification region, the current between the first electrode C and the second electrode E of the switching element 31 can pass through, and part of the input current of the backlight lamp set 20 can be shunted, so as to reduce the input current of the backlight lamp set 20 and thus reduce the display brightness.

[0038] It should be noted that, please refer to Figure 3 , the switching element 31 is taken as an example of an NPN type triode, and the working of the switching element 31 in the amplification region means that if the voltage of the base electrode (i.e. the control electrode B in the triode) is higher than the voltage of the emitter electrode (i.e. the second electrode E in the triode), and the voltage difference is greater than the conduction voltage of the PN junction, the emission junction of the triode is forward biased, and the collector junction is reverse biased, i.e. the collector electrode (i.e. the first electrode C in the triode) is reverse biased. Figure 3 Figure 3 Figure 3 ​​When the base voltage is higher than the collector voltage, the base current controls the collector current, and the transistor has current amplification. An important parameter of the transistor is the current amplification factor β. When a small current is applied to the base of the transistor, a current β times the injection current is obtained at the collector, i.e. the collector current. The collector current changes with the base current, and a small change in the base current can cause a large change in the collector current, which is the amplification of the transistor. In simple terms, the transistor in the amplification state can control a large change in the collector current with a small change in the base current, realizing current amplification.

[0039] In the embodiment, when the switch element 31 is in the amplification state, the base of the transistor receives the control signal, and a small change in the control signal current controls a large change in the collector current, Figure 3 For example, only the collector of the switch element 31 is electrically connected to the commutation end SW of the backlight driving chip 10 and the positive end of the backlight lamp set 20, and a large change in the collector current causes an increase in the current flowing from the collector (first pole C) to the emitter (second pole E), which can shunt part of the current input to the backlight lamp set 20 and reduce the display brightness.

[0040] Specifically, please refer to Figure 3 In an optional embodiment provided by the present disclosure, the switch element 31 can be a transistor, and an N-type transistor is taken as an example for illustration. The transistor includes a base, an emitter and a collector. The base of the transistor is used to receive a PWM dimming signal, and is used to control the transistor to work in an amplification region. The collector of the transistor is electrically connected to the commutation end SW of the backlight driving chip 10 and the positive end of the backlight lamp set 20. The emitter of the transistor is electrically connected to the feedback end FB of the backlight driving chip 10 and the negative end of the backlight lamp set 20. In another optional embodiment provided by the present disclosure, the switch element 31 can be a field effect transistor. The field effect transistor includes a gate, a source and a drain. The gate of the field effect transistor is used to receive a PWM dimming signal, and is used to control the field effect transistor to work in an amplification region. The source of the field effect transistor is electrically connected to the commutation end SW of the backlight driving chip 10 and the positive end of the backlight lamp set 20. The drain of the field effect transistor is electrically connected to the feedback end FB of the backlight driving chip 10 and the negative end of the backlight lamp set 20.

[0041] It should be noted that the transistor can be N-type or P-type, and the present disclosure does not specifically limit the type of the transistor. The field effect transistor can be N-type or P-type, and the present disclosure does not specifically limit the type of the field effect transistor. When the types of the transistor or the field effect transistor are different, the connection of the switch element 31 in the shunt circuit 30 can be adaptively adjusted.

[0042] Please combine Figure 2 andFigure 3 In an optional embodiment provided by the present disclosure, the shunt circuit 30 comprises a first resistor 33, one end of the first resistor 33 is electrically connected to the second pole E of the switching element 31, and the other end is electrically connected to the negative end of the backlight lamp set 20 and the feedback end FB of the backlight driving chip 10.

[0043] Specifically, the first resistor 33 is connected in series with the switching element 31, the first resistor 33 is located between the second pole E of the switching element 31 and the feedback end FB of the backlight driving chip 10, and the first resistor 33 is also electrically connected to the negative end of the backlight lamp set 20, that is, the first resistor 33 is used for voltage division to reduce the current in the shunt circuit 30, and the resistance value of the first resistor 33 can be set according to actual needs.

[0044] In an optional embodiment provided by the present disclosure, the shunt circuit 30 comprises a filter circuit 32, a first end of the filter circuit 32 is used for receiving a control signal, and the control signal comprises a PWM dimming signal, and a second end of the filter circuit 32 is electrically connected to the control pole of the switching element 31.

[0045] Specifically, the backlight driving circuit 100 comprises the shunt circuit 30, the shunt circuit 30 comprises the filter circuit 32, the filter circuit 32 is located between the PWM dimming signal and the switching element 31, and the filter circuit 32 can convert the PWM dimming signal into a relatively gentle direct-current voltage signal for controlling the switching element 31 to work in an amplification zone.

[0046] Please refer to Figure 3 In an optional embodiment provided by the present disclosure, the filter circuit 32 comprises a first capacitor 35 and a second resistor 34, one end of the second resistor 34 is used for receiving a control signal, the other end is electrically connected to the control pole B of the switching element 31 and the first capacitor 35, and the other end of the first capacitor 35 is grounded.

[0047] The filter circuit 32 is used to convert the PWM dimming signal with high-frequency variation into a gentle voltage signal, and the cost is low.

[0048] In an optional embodiment provided by the present disclosure, the backlight driving chip 10 is a single-channel backlight driving chip 10.

[0049] Specifically, the backlight driving chip 10 is a single-channel backlight driving chip 10, compared with a multi-channel backlight driving chip 10, the single-channel backlight driving chip 10 has low cost, can adjust the brightness of the backlight through the PWM dimming signal, and has high-efficiency and high-precision current regulation function.

[0050] The backlight driving chip 10 generally has a voltage boosting function, the backlight lamp set 20 includes a plurality of LED lamps, the LED lamps need a higher voltage to work normally, and the power supply voltage on the circuit board is generally low, and the voltage boosting function of the backlight driving chip 10 can increase the low voltage to the required high voltage to meet the voltage requirement of the backlight lamp set 20.

[0051] Figure 4 A schematic diagram of a liquid crystal display device provided by the embodiment of the present disclosure is shown, please refer to Figure 4 In a second aspect, based on the same inventive concept, the present disclosure further provides a liquid crystal display device 200, comprising the backlight driving circuit 100 as described above.

[0052] It can be understood that the brightness of the liquid crystal display device 200 is positively correlated with the current flowing through the backlight lamp set 20. The liquid crystal display device 200 provided by the embodiment adopts the backlight driving circuit 100 provided by the above embodiment to supply power to the backlight lamp set 20, so that the maximum driving current flowing through the backlight lamp set 20 is changed, thereby realizing low-brightness display of the liquid crystal display device 200.

[0053] The liquid crystal display device 200 includes but is not limited to a computer, a notebook computer, a smart phone, a tablet computer and a portable wearable device.

[0054] In summary, the present disclosure provides a backlight driving circuit and a liquid crystal display device, which comprises a backlight driving chip, a backlight lamp set, and a shunt circuit between the backlight driving chip and the backlight lamp set. The first end of the shunt circuit is used to receive a PWM dimming signal, the second end of the shunt circuit is electrically connected with the positive end of the backlight lamp set and the commutation end of the backlight driving chip, and the third end of the shunt circuit is electrically connected with the negative end of the backlight lamp set and the feedback end of the backlight driving chip. In this way, in a single-channel backlight driving circuit, by setting the backlight driving circuit with the shunt circuit and making the switching element in the shunt circuit work in the amplification zone, part of the current input to the positive end of the backlight lamp set can be diverted to the feedback end of the backlight driving chip, the input current of the positive end of the backlight lamp set is reduced, the display uniformity of the same liquid crystal display device under low brightness is improved, and the objective condition limitation that the minimum screen brightness cannot meet the customer's requirements due to the insufficient low duty cycle of part of the backlight driving chip is reduced.

[0055] The above description is merely a specific implementation of the present disclosure, which enables those skilled in the art to understand or implement the present disclosure. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure will not be limited to these embodiments described herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A backlight driving circuit, characterized by comprising: The backlight driving circuit comprises a backlight driving chip, a backlight lamp set, a shunt circuit and a filter circuit. The shunt circuit is used for receiving a control signal and shunting the current input to the backlight lamp set according to the control signal. The shunt circuit comprises a first end, a second end and a third end.

2. The backlight drive circuit of claim 1, wherein, The shunt circuit comprises a switching element.

3. The backlight drive circuit of claim 2, wherein, The switching element comprises a triode or a field effect transistor.

4. The backlight drive circuit of claim 3, wherein, The shunt circuit comprises a first resistor.

5. The backlight drive circuit of claim 3, wherein, The filter circuit comprises a first capacitor and a second resistor.

6. The backlight drive circuit of claim 3, wherein, The control signal comprises a PWM dimming signal.

7. The backlight drive circuit of claim 6, wherein, The backlight driving circuit comprises the backlight driving circuit according to any one of claims 1-9.

8. The backlight drive circuit of claim 1, wherein, ​ 9. The backlight drive circuit of claim 1, wherein, ​ 10. A liquid crystal display device, characterized by comprising: ​

Images