Backlight driving circuit, backlight module and liquid crystal display

Abstract

The utility model relates to the technical field of backlight driving, and discloses a backlight driving circuit, a backlight module and a liquid crystal display, the backlight driving circuit comprises a power supply input end, a boost type driving chip, a first diode, a second diode and a first resistor; the boost type driving chip comprises a power supply pin, a switch pin and a feedback pin, the power supply input end is connected with the power supply pin, the switch pin is connected with the anode of the first diode, and the cathode of the first diode is connected with the anode of the second diode; the cathode of the second diode is connected with the anode pin of the backlight source, the cathode pin of the backlight source is connected in series with the first resistor and then is grounded, the cathode pin of the backlight source is connected with the feedback pin, and the voltage required by the backlight source is smaller than that of the power input end. According to the utility model, the voltage difference of the backlight driving circuit can be simulated and amplified, so that the problem that a Boost type driving chip is difficult to drive a low-voltage backlight source can be effectively avoided.

Description

Technical Field

[0001] This utility model relates to the field of backlight driving technology, specifically to a backlight driving circuit, a backlight module, and a liquid crystal display. Background Technology

[0002] A liquid crystal display (LCD) is an electronic display device that uses the physical properties of liquid crystals to display images. It boasts advantages such as low power consumption, small size, large information capacity, and eye-friendliness, and is widely used in electronic display equipment, medical equipment, and public display equipment. LCDs do not emit light themselves and require a backlight. The backlight driver circuit converts the input power supply voltage into a voltage suitable for the backlight's operation, driving the backlight to emit light normally.

[0003] In some projects, designers may limit the selection of driver chips in the backlight driver circuit based on considerations such as the overall display architecture, power management strategy, cost, and compatibility. When the driver chip is limited to a boost converter, if the backlight is a low-voltage backlight, the characteristics of the boost converter may make it difficult to meet the driving requirements of the low-voltage backlight. A low-voltage backlight refers to a backlight that requires a voltage lower than the power supply voltage of the boost converter.

[0004] Currently, the solution to the above problem is to select a new driver chip. However, this requires re-verification, which is a complex and time-consuming process that impacts project delivery time. Utility Model Content

[0005] In view of this, the present invention provides a backlight driving circuit, a backlight module and a liquid crystal display, so as to effectively avoid the problem that Boost type driving chips are difficult to drive low voltage backlights, improve the compatibility of verified chips and reduce selection time.

[0006] In a first aspect, this utility model provides a backlight driving circuit, which includes a power input terminal, a boost converter driver chip, a first diode, a second diode, and a first resistor. The boost converter driver chip includes a power supply pin, a switch pin, and a feedback pin. The power input terminal is connected to the power supply pin, the switch pin is connected to the anode of the first diode, and the cathode of the first diode is connected to the anode of the second diode. The cathode of the second diode is connected to the positive pin of the backlight source, the negative pin of the backlight source is connected to ground in series with the first resistor, and the negative pin of the backlight source is connected to the feedback pin. The voltage required by the backlight source is less than the voltage of the power input terminal.

[0007] In this embodiment, by connecting a suitable second diode in series in the backlight driving circuit to simulate and amplify the voltage difference of the entire backlight driving circuit, the boost-type driver chip can boost the low-voltage backlight and the second diode to work, improving the compatibility of the verified chip and reducing selection time. At the same time, the backlight driving circuit can stably output the corresponding current according to the backlight requirements, ensuring the stable operation of the low-voltage backlight and making the LCD display screen uniform in brightness and flicker-free.

[0008] In one alternative implementation, a light-emitting diode is used to form the second diode.

[0009] In one alternative embodiment, the backlight driving circuit further includes a first capacitor and an inductor; one end of the first capacitor is connected to the power input terminal, and the other end of the first capacitor is grounded; one end of the inductor is connected to the power input terminal and the power pin, and the other end of the inductor is connected to the anode of the first diode and the switch pin.

[0010] In this embodiment, the inductor serves as an energy storage and filter, maintaining a stable current output, while the first capacitor filters out high and low frequency ripple in the power supply, making the input power supply more stable.

[0011] In one optional embodiment, the backlight driving circuit further includes a second capacitor and a third capacitor, and the boost type driving chip further includes a compensation pin and a ground pin; one end of the second capacitor is connected to the cathode of the first diode and the anode of the second diode, and the other end of the second capacitor is grounded; one end of the third capacitor is connected to the compensation pin, and the other end of the third capacitor is grounded, and the ground pin is grounded.

[0012] In this embodiment, the second capacitor reduces the voltage fluctuations of the first diode's output, making the output DC voltage smoother and more stable. The third capacitor connected to the compensation pin provides frequency compensation for the feedback control loop in the boost converter chip, improving circuit stability and dynamic response performance, and preventing instability such as oscillations.

[0013] In one alternative implementation, the boost driver chip further includes a control signal input pin, which is connected to the control signal output terminal of the microcontroller.

[0014] In one alternative implementation, the voltage at the power input terminal is 3.3V or 5V.

[0015] Secondly, the present invention provides a backlight module, which includes a backlight source and a backlight driving circuit according to the first aspect or any corresponding embodiment.

[0016] In one alternative implementation, the backlight includes four parallel light-emitting groups, each light-emitting group including at least one light-emitting unit.

[0017] In one alternative implementation, the light-emitting unit is a cold cathode fluorescent lamp or a light-emitting diode.

[0018] Thirdly, the present invention provides a liquid crystal display, including a backlight module and a liquid crystal display screen according to the second aspect or any corresponding embodiment described above, wherein the backlight module is located below the liquid crystal display screen. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the specific embodiments or related technologies of this utility model, the drawings used in the description of the specific embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of a backlight driving circuit according to an embodiment of the present utility model;

[0021] Figure 2 This is a schematic diagram of another backlight driving circuit according to an embodiment of the present utility model;

[0022] Figure 3 This is a schematic diagram of another backlight driving circuit according to an embodiment of the present utility model;

[0023] Figure 4 This is a schematic diagram of the connection of the light-emitting group in a backlight according to an embodiment of the present utility model;

[0024] Figure 5 This is an equivalent circuit diagram of the light-emitting group in a backlight according to an embodiment of the present utility model. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the protection scope of this utility model.

[0026] The backlight driving circuit provided by this utility model can be applied to the LCD field, and the driving chip is a Boost type driving chip, and the backlight is a low voltage backlight.

[0027] Specifically, a backlight provides the light source behind the LCD, as the LCD itself does not emit light and requires a backlight to illuminate the liquid crystal layer to display images. A Boost converter chip is a switching power supply chip primarily used to boost the input voltage to a higher output voltage to meet load demands. The operation of a Boost converter chip is based on the energy storage characteristics of an inductor and the on / off control of a switching transistor. Through periodic switching actions, electrical energy is stored in the inductor and then released at appropriate times, thereby achieving a voltage boost.

[0028] The backlight driving circuit provided by this utility model can simulate and amplify the voltage difference of the backlight driving circuit by connecting a diode in series between the Boost type driving chip and the backlight source. This can effectively avoid the problem that the Boost type driving chip is difficult to drive the low-voltage backlight source, and thus avoid re-verification of the chip.

[0029] The backlight driving circuit provided by this utility model will be described in detail below with reference to the accompanying drawings.

[0030] like Figure 1 As shown, the backlight driving circuit includes a power input terminal VCC, a boost type driver chip 110, a first diode D1, a second diode D2, and a first resistor R1.

[0031] The boost driver chip 110 includes a power supply pin VIN ( Figure 1 The first pin of the chip), the switch pin SW ( Figure 1 The third pin of the chip) and the feedback pin FB ( Figure 1 The sixth pin of the chip is connected to the power input pin VCC and the power supply pin VIN. The switch pin SW is connected to the anode of the first diode D1, and the cathode of the first diode D1 is connected to the anode of the second diode D2. The cathode of the second diode D2 is connected to the positive terminal LED+ of the backlight, and the negative terminal LED- of the backlight is connected to ground in series with the first resistor R1. The negative terminal LED- of the backlight is also connected to the feedback pin FB. In this embodiment, the voltage required by the backlight is less than the voltage of the power input pin VCC, that is, the backlight is a low-voltage backlight.

[0032] Specifically, the power supply pin VIN is connected to the power input terminal VCC to provide the DC voltage required for the operation of the boost driver chip 110 and related circuits, ensuring that the boost driver chip 110 can operate normally. For example, the voltage of the power input terminal VCC can be 3.3V or 5V, etc.

[0033] The switching pin SW controls the switching transistor's on / off state via a pulse signal output from the internal circuitry of the boost driver chip 110, ensuring the output voltage is higher than the power input voltage VCC. The feedback pin FB detects the output current and feeds the detected signal back to the control circuitry within the boost driver chip 110. The control circuitry compares the feedback signal with an internally set reference value and adjusts the output accordingly to maintain a stable output current.

[0034] The first diode D1 serves as a rectifier in the backlight driving circuit, maintaining a stable output voltage. For example, the first diode D1 can be a Schottky diode, a special PN junction diode formed by combining metal and N-type semiconductor materials. The first resistor R1 is used for current sampling, feeding the sampled signal back to the feedback pin FB so that the boost driver chip 110 can adjust the output based on the feedback signal to stabilize the output current.

[0035] In this embodiment, the designer selects the second diode D2 based on the voltage required by the backlight and the voltage of the power input terminal VCC. For example, the diode with a voltage greater than a first voltage is determined as the second diode D2. The first voltage can be the difference between the voltage of the power input terminal VCC and the voltage required by the backlight.

[0036] In one example, the voltage at the power input terminal VCC can be 3.3V. If the voltage required for the backlight is 2.7V, then a diode with a voltage of 0.8V can be selected as the second diode D2.

[0037] By selecting a voltage that is greater than the voltage required by the backlight and the voltage of the second diode D2, the boost driver chip 110 can amplify the voltage, thus effectively avoiding the problem that the boost driver chip cannot drive the low-voltage backlight.

[0038] Specifically, the power input terminal VCC is connected to the boost driver chip 110. The internal switching transistor of the boost driver chip 110 will turn on and off at a certain frequency, converting the input DC voltage into a high-frequency pulse voltage and boosting the input voltage to a suitable value to meet the operating voltage requirements of the backlight and the second diode D2. Moreover, in order to ensure that the light-emitting unit in the backlight can emit light stably, the boost driver chip 110 monitors the magnitude of the output current in real time through the feedback pin FB and the first resistor R1, and feeds the information back to the boost driver chip 110. The boost driver chip 110 adjusts the duty cycle of the switching transistor according to the feedback signal, thereby achieving precise control of the output current and keeping the current through the light-emitting unit constant.

[0039] In this embodiment, by connecting a suitable second diode D2 in series in the backlight driving circuit to simulate and amplify the voltage difference of the entire backlight driving circuit, the boost-type driver chip 110 can boost drive the low-voltage backlight and the second diode D2 to work, improving the compatibility of the verified chip and reducing selection time. At the same time, the backlight driving circuit can stably output the corresponding current according to the backlight requirements, ensuring the stable operation of the low-voltage backlight and making the LCD display screen uniform in brightness and flicker-free.

[0040] In some embodiments, the second diode D2 can be formed by a light-emitting diode (LED).

[0041] Specifically, a light-emitting diode (LED) is a semiconductor device that can convert electrical energy into visible light. When current passes through the diode, electrons and holes recombine, releasing energy and emitting it in the form of photons, thus producing light.

[0042] In this embodiment, the light-emitting diode is used as the second diode D2. The second diode D2 can not only bear part of the output voltage of the boost driver chip 110, but also serve as an indicator light to indicate whether the backlight driving circuit is working properly.

[0043] For example, such as Figure 2 As shown, the backlight driving circuit also includes a first capacitor C1 and an inductor L1.

[0044] One end of the first capacitor C1 is connected to the power input terminal VCC, and the other end of the first capacitor C1 is grounded. One end of the inductor L1 is connected to the power input terminal VCC and the power pin VIN, and the other end of the inductor L1 is connected to the anode of the first diode D1 and the switch pin SW.

[0045] Specifically, in the backlight driving circuit, inductor L1 serves as both an energy storage and filter. When the switching transistor is on, the inductor stores energy; when the switching transistor is off, the inductor releases energy to maintain a stable current output. The first capacitor C1 can have a capacitance of 22μF and is used for power supply filtering, removing high and low frequency ripples in the power supply to make the input power supply more stable.

[0046] Furthermore, such as Figure 3 As shown, the backlight driving circuit also includes a second capacitor C2 and a third capacitor C3, and the boost type driver chip 110 also includes a compensation pin COMP. Figure 3 The 5th pin of the chip) and the ground pin GND ( Figure 3 (The 4th pin of the chip).

[0047] In this configuration, one end of the second capacitor C2 is connected to the cathode of the first diode D1 and the anode of the second diode D2, while the other end of the second capacitor C2 is grounded. One end of the third capacitor C3 is connected to the compensation pin COMP, while the other end of the third capacitor C3 is grounded, and the grounding pin GND is grounded.

[0048] Specifically, the second capacitor C2 has a capacitance of 0.047μF, which stores charge when the voltage output of the first diode D1 increases and releases charge when the voltage decreases, thereby reducing the voltage fluctuation of the first diode D1 and making the output DC voltage smoother and more stable. The compensation pin COMP is connected to a third capacitor C3, which is used to perform frequency compensation on the feedback control loop in the boost driver chip 110, improving the circuit's stability and dynamic response performance, and preventing instability phenomena such as oscillations.

[0049] For example, such as Figure 3 As shown, the boost driver chip 110 also includes a control signal input pin CTRL ( Figure 3 The second pin of the chip (CTRL) is connected to the control signal output of the microcontroller. For example, the control signal can be a pulse-width modulation (PWM) signal.

[0050] Specifically, the boost converter driver chip 110 can receive PWM signals from the microcontroller and then flexibly adjust the brightness of the backlight based on the PWM signals. The PWM signal is periodic, and by adjusting the proportion of the high-level time of the signal within one cycle (i.e., the duty cycle), the average current flowing through the backlight can be controlled. The larger the duty cycle, the longer the backlight is powered on per unit time, the larger the average current, and the higher the brightness; conversely, the lower the brightness.

[0051] This utility model also provides a backlight module, which includes a backlight source and a backlight driving circuit provided in any of the above embodiments.

[0052] For example, such as Figure 4 As shown, the backlight may include four parallel light-emitting groups, each of which includes at least one light-emitting unit. Figure 4 In the diagram, A(+) represents the positive pin LED+ of the backlight. Figure 4 In the diagram, K1(-) to K4(-) represent the negative pins of the backlight. Figure 4 Taking each light-emitting group as an example, which includes one light-emitting unit, but not limited to this. Here, Q1 represents the light-emitting unit of the first light-emitting group, Q2 represents the light-emitting unit of the second light-emitting group, Q3 represents the light-emitting unit of the third light-emitting group, and Q4 represents the light-emitting unit of the fourth light-emitting group.

[0053] In this embodiment, after connecting the second diode D2 in series between the Boost type driver chip and the backlight, the equivalent circuit diagram of the backlight can be as follows: Figure 5 As shown, the original four-lamp parallel backlight can be equivalent to an eight-lamp backlight with four two-lamp series connections.

[0054] Alternatively, the light-emitting unit can be a cold cathode fluorescent lamp (CCFL) or a light-emitting diode (LED).

[0055] Specifically, CCFL (CCFL) is a gas discharge light-emitting diode (PDD) lamp. High voltage is applied across the lamp tube to ionize the gas inside, forming plasma that excites phosphors to emit light. LED (LED) is a semiconductor light-emitting diode. When a forward voltage is applied to an LED, electrons and holes recombine at the PN junction, releasing excess energy as light. CCFLs offer higher brightness and uniformity, while LEDs boast advantages such as low power consumption, long lifespan, fast response time, and wide color gamut.

[0056] In some implementations, the backlight also includes a light guide plate, a reflective sheet, a diffuser sheet, and a prism sheet. The light guide plate converts point or line light sources into surface light sources, allowing light to be evenly distributed across the entire back of the LCD screen. The reflective sheet, located at the bottom of the light guide plate, reflects light leaking from the bottom back into the light guide plate, reducing light loss and improving light utilization, thereby enhancing backlight brightness. The diffuser sheet, placed above the light guide plate, scatters light in different directions, further homogenizing the light and reducing brightness unevenness caused by uneven light output from the light guide plate or differences in the light source itself, resulting in more consistent brightness across the entire LCD screen and improved display performance. The prism sheet refracts and converges light, focusing it in a direction perpendicular to the LCD screen, reducing horizontal scattering, thereby increasing the front brightness of the screen and enhancing display contrast and viewing angle.

[0057] Specifically, after the light-emitting unit in the backlight generates light, the light is evenly distributed behind the entire liquid crystal display through the action of optical components such as light guide plates, reflective sheets, diffuser sheets and prism sheets, providing a uniform light source for the liquid crystal layer.

[0058] This utility model also provides a liquid crystal display, which includes the backlight module and liquid crystal display screen provided above, with the backlight module located below the liquid crystal display screen.

[0059] Specifically, a liquid crystal display (LCD) is a device that uses the physical properties of liquid crystals to display images. Liquid crystals are substances between solid and liquid states, possessing unique physical properties such as optical anisotropy and dielectric anisotropy. Under the influence of an electric field, the arrangement of liquid crystal molecules changes, thereby altering their refraction and polarization properties of light. LCDs utilize this property to control the transmission or blocking of light by controlling the arrangement of liquid crystal molecules, thus enabling the display of images and text.

[0060] For example, a liquid crystal display screen may include a liquid crystal layer, a glass substrate, a polarizer, and a color filter. The liquid crystal layer, the core component of the LCD screen, is composed of liquid crystal molecules sandwiched between two glass substrates and is used to modulate light. The glass substrates provide support for the liquid crystal layer and have various electrodes and circuit patterns fabricated on their surfaces to control the state of the liquid crystal molecules. Polarizers, located on either side of the liquid crystal layer, allow only light polarized in a specific direction to pass through, working in conjunction with the liquid crystal layer to control the light and enable the user to see a clear image. The color filter decomposes white light into the three primary colors of red, green, and blue, and displays various colors by controlling the brightness combinations of these three primary colors.

[0061] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicate the orientation or positional relationship according to the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0062] In this utility model, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0063] It should be understood that the various parts of this utility model can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0064] In the description of this specification, the references to terms such as "this embodiment," "an embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0065] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this utility model, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0066] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the present invention.

Claims

1. A backlight driving circuit, characterized by comprising: The backlight driving circuit comprises a power input end, a boost driving chip, a first diode, a second diode and a first resistor. The boost driving chip comprises a power pin, a switch pin and a feedback pin, the power input end is connected with the power pin, the switch pin is connected with an anode of the first diode, and a cathode of the first diode is connected with an anode of the second diode. A cathode of the second diode is connected with a positive pin of the backlight, a negative pin of the backlight is connected with the feedback pin after being connected with the first resistor in series and then grounded, and the negative pin of the backlight is connected with the feedback pin, wherein a voltage required by the backlight is less than a voltage of the power input end.

2. The backlight driving circuit according to claim 1, wherein The second diode is constituted by a light emitting diode.

3. The backlight driving circuit according to claim 1, wherein The backlight driving circuit further comprises a first capacitor and an inductor. One end of the first capacitor is connected with the power input end, the other end of the first capacitor is grounded, one end of the inductor is connected with the power input end and the power pin, and the other end of the inductor is connected with the anode of the first diode and the switch pin.

4. The backlight driving circuit according to any one of claims 1 to 3, characterized in that, The backlight driving circuit further comprises a second capacitor and a third capacitor, and the boost driving chip further comprises a compensation pin and a ground pin. One end of the second capacitor is connected with the cathode of the first diode and the anode of the second diode, and the other end of the second capacitor is grounded. One end of the third capacitor is connected with the compensation pin, and the other end of the third capacitor is grounded, and the ground pin is grounded.

5. The backlight driving circuit according to claim 4, wherein The boost driving chip further comprises a control signal input pin, and the control signal input pin is connected with a control signal output end of a microcontroller.

6. The backlight driving circuit according to any one of claims 1 to 3, wherein The voltage of the power input end is 3.3V or 5V.

7. A backlight module, characterized in that, The backlight module comprises a backlight and the backlight driving circuit according to any one of claims 1 to 6.

8. The backlight module of claim 7, wherein, The backlight comprises four light emitting groups connected in parallel, and each light emitting group comprises at least one light emitting unit.

9. The backlight module of claim 8, wherein, The light emitting unit is a cold cathode fluorescent lamp or a light emitting diode.

10. A liquid crystal display device, characterized by comprising: The backlight module according to any one of claims 7 to 9 and a liquid crystal display screen are provided, and the backlight module is arranged below the liquid crystal display screen.

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