LED backlight driving circuit and pre-charging circuit thereof

Abstract

The invention discloses an LED backlight driving chip. An LED backlight driving circuit comprises an LED pin, a high-voltage MOS switch tube M1, a low-voltage driving current MOS switch tube M2, an operational amplifier, a driving resistor and a pre-charging module. The pre-charging module comprises a pre-charging MOS switch tube M3, a pre-charging power supply and a pre-charging control unit. According to the LED backlight driver, the body diode characteristic of the high-voltage MOS tube is utilized, and the control MOS tube in the pre-charging circuit is set as a low-voltage device, so that the layout area of a semiconductor integrated circuit is reduced. And the pre-charging efficiency is improved by utilizing the quick response characteristic of the low-voltage MOS device.

Description

Technical Field

[0001] The present invention relates to the technical field of LED backlight, and in particular to an LED backlight driving circuit and a pre-charging circuit thereof. Background Art

[0002] Liquid crystal display (LCD) is the largest screen display application in modern display panels. The liquid crystal material used in LCD panels cannot emit light by itself and needs to be provided by a backlight source. LED backlight sources have the advantages of energy saving, environmental protection, and high performance and are widely used in LCD display panels. The performance of LED backlight driver chips is crucial to LCD display panels.

[0003] like Figure 1-2 The schematic diagram of the LED backlight driving circuit and pre-charging circuit structure in the prior art is shown in FIG. The conventional matrix scanning LED backlight driving circuit structure is as follows Figure 1 , the current source at the low potential end will be continuously reused by the switch HS_SW at the high potential end. When the cathode voltage of the LED string is relatively low and the control end PWM of the high-voltage MOS switch M1 is 0 at the same time, once the high-end switch HS_SW is switched, the corresponding LED string will be connected to the parasitic capacitor C p It flashes under the action of, and the LED cathode needs to be pre-charged during the dead time of the switch.

[0004] The pre-charging circuit in the prior art is as follows Figure 2 When PWM = 0, the high-voltage MOS switch M1 is turned off, the pre-charge MOS switch tube M3 is turned on, and the driving voltage provided by the pre-charge power supply will pass through the pre-charge MOS switch tube M3 to the parasitic capacitance C of the LED pin. p Charging to ensure that when PWM=0, the LED pin voltage is maintained at the voltage required by the system. Since the LED pin needs to withstand high voltage (for example, the cathode voltage of the LED light string reaches 40V when it is forward-conducting), M3 also needs a high-voltage switch tube. In order to ensure that the LED port can be quickly charged, the on-resistance of the pre-charge MOS switch tube M3 needs to be relatively small, and the driving ability of the pre-charge control unit needs to be relatively strong to ensure that the LED port voltage can be quickly charged. According to the above performance requirements for the pre-charge circuit, the prior art requires a relatively large chip area and power consumption to realize the pre-charge circuit. In the design of integrated circuits, the use of large-area semiconductor layout and high-voltage devices means a significant increase in the manufacturing cost of the chip.

[0005] It can be seen that the prior art requires an LED backlight driving circuit and a pre-charging circuit with lower chip manufacturing cost. Summary of the invention

[0006] The present invention provides an LED backlight driving circuit, which utilizes the body diode characteristics of a high-voltage MOS tube to set the control MOS tube in the pre-charging circuit as a low-voltage device, thereby reducing the layout area of ​​the semiconductor integrated circuit. The fast response characteristics of the low-voltage MOS device are utilized to improve the efficiency of pre-charging.

[0007] Based on the above technical purpose, the present invention provides an LED backlight driving circuit, which includes: an LED pin, a high-voltage MOS switch tube M1, a low-voltage drive current MOS switch tube M2, an operational amplifier, a driving resistor and a pre-charging module; the pre-charging module includes a pre-charging MOS switch tube M3, a pre-charging power supply and a pre-charging control unit;

[0008] The LED pin is used to connect the cathode of the LED light string, the drain of the high-voltage MOS switch tube M1 is connected to the LED pin, and the gate of the high-voltage MOS switch tube M1 is controlled by a PWM signal; the source of the high-voltage MOS switch tube M1 is connected to the drain of the low-voltage drive current MOS switch tube M2;

[0009] The gate of the low-voltage drive current MOS switch tube M2 is connected to the output end of the operational amplifier, and the non-inverting input end of the operational amplifier inputs an external reference voltage V ref The source of the low voltage driving current MOS switch tube M2 is connected to one end of the driving resistor, and the other end of the driving resistor is grounded. The inverting input end of the operational amplifier is connected to the source of the low voltage driving current MOS switch tube M2;

[0010] The source of the pre-charging MOS switch tube M3 is connected to the source of the high-voltage MOS switch tube M1 , the drain of the pre-charging MOS switch tube M3 is connected to the pre-charging power supply, and the gate of the pre-charging MOS switch tube M3 is connected to the pre-charging control unit.

[0011] In one embodiment, the high-voltage MOS switch tube M1 and the low-voltage drive current MOS switch tube M2 are NMOS switch tubes.

[0012] In one embodiment, the pre-charging MOS switch tube M3 is an NMOS switch tube.

[0013] In one embodiment, when the PWM signal controlling the gate of the high-voltage MOS switch tube M1 is at a low level, the pre-charging control unit controls the pre-charging MOS switch tube M3 to be turned on, and the pre-charging power supply at the drain end of the pre-charging MOS switch tube M3 applies a voltage to the source of the high-voltage MOS switch tube M1.

[0014] In one embodiment, the parasitic capacitance C on the LED pinp The charging speed is controlled by the voltage provided by the pre-charging power supply.

[0015] The present invention also provides another LED backlight driving circuit, the LED backlight driving circuit comprises: an LED pin, a high-voltage MOS switch tube M1, a low-voltage drive current MOS switch tube M2, an operational amplifier, a driving resistor and a pre-charging module; the pre-charging module comprises a pre-charging MOS switch tube M3, a pre-charging power supply and a pre-charging control unit;

[0016] The LED pin is used to connect the cathode of the LED light string, the drain of the high-voltage MOS switch tube M1 is connected to the LED pin, and the gate of the high-voltage MOS switch tube M1 is controlled by a PWM signal; the source of the high-voltage MOS switch tube M1 is connected to the drain of the low-voltage drive current MOS switch tube M2;

[0017] The gate of the low-voltage drive current MOS switch tube M2 is connected to the output end of the operational amplifier, and the non-inverting input end of the operational amplifier inputs an external reference voltage V ref The source of the low-voltage drive current MOS switch tube M2 is connected to one end of the drive resistor, and the other end of the drive resistor is connected to an external drive power supply. The inverting input end of the operational amplifier is connected to the source of the low-voltage drive current MOS switch tube M2;

[0018] The source of the pre-charging MOS switch tube M3 is connected to the source of the high-voltage MOS switch tube M1 , the drain of the pre-charging MOS switch tube M3 is connected to the pre-charging power supply, and the gate of the pre-charging MOS switch tube M3 is connected to the pre-charging control unit.

[0019] In one embodiment, the high-voltage MOS switch tube M1 and the low-voltage drive current MOS switch tube M2 are PMOS switch tubes.

[0020] In one embodiment, the pre-charging MOS switch tube M3 is a PMOS switch tube.

[0021] In one embodiment, when the PWM signal controlling the gate of the high-voltage MOS switch tube M1 is at a low level, the pre-charging control unit controls the pre-charging MOS switch tube M3 to be turned on, and the pre-charging power supply at the drain end of the pre-charging MOS switch tube M3 applies a voltage to the source of the high-voltage MOS switch tube M1.

[0022] Compared with the prior art, one or more embodiments of the present invention may have the following advantages:

[0023] The LED backlight driver of the present invention utilizes the body diode characteristics of the high-voltage MOS tube and sets the control MOS tube in the pre-charging circuit as a low-voltage device, thereby reducing the layout area of ​​the semiconductor integrated circuit. The fast response characteristics of the low-voltage MOS device are utilized to improve the efficiency of pre-charging.

[0024] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0026] Figure 1 It is a schematic diagram of the structure of a matrix LED backlight driving circuit in the prior art;

[0027] Figure 2 It is a schematic diagram of the structure of a pre-charging circuit in the prior art;

[0028] Figure 3 is a schematic structural diagram of an LED backlight driving circuit according to a first embodiment of the present invention;

[0029] Figure 4 It is a schematic diagram of the structure of the LED backlight driving circuit of the second embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings.

[0031] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part. And when the second element, component, region, layer or part is discussed, it does not indicate that the present invention necessarily has the first element, component, region, layer or part.

[0032] Spatially relative terms such as "under", "beneath", "below", "under", "above", "above", etc., may be used here for convenience of description to describe the relationship between an element or feature shown in the figure and other elements or features. It should be understood that in addition to the orientation shown in the figure, the spatial relationship terms are intended to also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is turned over, then the elements or features described as "under other elements" or "under it" or "under it" will be oriented as "on" other elements or features. Therefore, the exemplary terms "under" and "under" may include both upper and lower orientations. The device can be oriented otherwise (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0033] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present invention. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0034] Example 1

[0035] like Figure 3As shown, the LED backlight driving circuit of the present invention includes: an LED pin, a high-voltage MOS switch tube M1, a low-voltage driving current MOS switch tube M2, an operational amplifier, a driving resistor and a pre-charging module; the pre-charging module includes a pre-charging MOS switch tube M3, a pre-charging power supply and a pre-charging control unit.

[0036] Among them, the LED pin is used to connect the cathode of the LED light string, the high-voltage MOS switch tube M1 and the low-voltage drive current MOS switch tube M2 are NMOS switch tubes, the drain of the high-voltage MOS switch tube M1 is connected to the LED pin, and the gate of the high-voltage MOS switch tube M1 is controlled by a PWM signal, that is, the PWM signal controls the conduction or cutoff of the high-voltage MOS switch tube M1; the source of the high-voltage MOS switch tube M1 is connected to the drain of the low-voltage drive current MOS switch tube M2.

[0037] The gate of the low-voltage drive current MOS switch tube M2 is connected to the output end of the operational amplifier, and the non-inverting input end of the operational amplifier inputs an external reference voltage V ref The source of the low voltage driving current MOS switch tube M2 is connected to one end of the driving resistor, and the other end of the driving resistor is grounded. The inverting input end of the operational amplifier is connected to the source of the low voltage driving current MOS switch tube M2. ref The driving resistor determines the magnitude of the driving current of the LED light string.

[0038] The pre-charge MOS switch tube M3 is an NMOS switch tube, the source of the pre-charge MOS switch tube M3 is connected to the source of the high-voltage MOS switch tube M1, the drain of the pre-charge MOS switch tube M3 is connected to the pre-charge power supply, and the gate of the pre-charge MOS switch tube M3 is connected to the pre-charge control unit. In this embodiment, when the PWM signal controlling the gate of the high-voltage MOS switch tube M1 is at a low level, the pre-charge control unit controls the pre-charge MOS switch tube M3 to be turned on, and then the pre-charge power supply at the drain end of the pre-charge MOS switch tube M3 applies a voltage to the source of the high-voltage MOS switch tube M1. Since there is an equivalent body diode between the source and the drain of the high-voltage MOS switch tube M1 when the high-voltage MOS switch tube M1 is in the cut-off state, when the pre-charge power supply is provided to a certain voltage value, this can realize the source-to-drain conduction of the high-voltage MOS switch tube M1, thereby realizing the charging of the parasitic capacitance Cp on the LED pin. And the charging speed can be controlled by the voltage provided by the pre-charge power supply.

[0039] On the other hand, since the source of the pre-charged MOS switch tube M3 in this embodiment is connected to the source of the high-voltage MOS switch tube M1, the voltage of the source of the pre-charged MOS switch tube M3 belongs to the low voltage range, so the pre-charged MOS switch tube M3 does not need to use a high-voltage device, that is, it can save a lot of chip area when designing integrated circuits. And the pre-charged MOS switch tube M3, as a low-voltage device, has a faster response speed than the high-voltage charging MOS tube in the prior art, and can meet the charging operation of the parasitic capacitor in a shorter time interval.

[0040] Example 2

[0041] like Figure 4 As shown, the LED backlight driving circuit of the present invention includes: LED pin, high-voltage MOS switch tube M1, low-voltage drive current MOS switch tube M2, operational amplifier, drive resistor and pre-charging module; the pre-charging module includes pre-charging MOS switch tube M3, pre-charging power supply and pre-charging control unit.

[0042] Among them, the LED pin is used to connect the anode of the LED light string, the high-voltage MOS switch tube M1 and the low-voltage drive current MOS switch tube M2 are PMOS switch tubes, the drain of the high-voltage MOS switch tube M1 is connected to the LED pin, and the gate of the high-voltage MOS switch tube M1 is controlled by a PWM signal, that is, the PWM signal controls the conduction or cutoff of the high-voltage MOS switch tube M1; the source of the high-voltage MOS switch tube M1 is connected to the drain of the low-voltage drive current MOS switch tube M2.

[0043] The gate of the low-voltage drive current MOS switch tube M2 is connected to the output end of the operational amplifier, and the non-inverting input end of the operational amplifier inputs an external reference voltage V ref The source of the low voltage driving current MOS switch tube M2 is connected to one end of the driving resistor, and the other end of the driving resistor is connected to an external driving power supply. The external driving power supply is a negative voltage power supply. The inverting input end of the operational amplifier is connected to the source of the low voltage driving current MOS switch tube M2. The external reference voltage V ref The driving resistor determines the magnitude of the driving current of the LED light string.

[0044] The pre-charge MOS switch tube M3 is a PMOS switch tube, the source of the pre-charge MOS switch tube M3 is connected to the source of the high-voltage MOS switch tube M1, the drain of the pre-charge MOS switch tube M3 is connected to the pre-charge power supply, and the gate of the pre-charge MOS switch tube M3 is connected to the pre-charge control unit. In this embodiment, when the PWM signal controlling the gate of the high-voltage MOS switch tube M1 is at a low level, the pre-charge control unit controls the pre-charge MOS switch tube M3 to be turned on, and then the pre-charge power supply at the drain end of the pre-charge MOS switch tube M3 applies a voltage to the source of the high-voltage MOS switch tube M1. Since there is an equivalent body diode between the source and the drain of the high-voltage MOS switch tube M1 when the high-voltage MOS switch tube M1 is in the cut-off state, when the pre-charge power supply is provided to a certain voltage value, this can realize the source-to-drain conduction of the high-voltage MOS switch tube M1, thereby realizing the charging of the parasitic capacitance Cp on the LED pin. And the charging speed can be controlled by the voltage provided by the pre-charge power supply.

[0045] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. An LED backlight driving circuit, characterized in that: The LED backlight driving circuit includes: an LED pin, a high-voltage MOS switch tube M1, a low-voltage drive current MOS switch tube M2, an operational amplifier, a driving resistor and a pre-charging module; the pre-charging module includes a pre-charging MOS switch tube M3, a pre-charging power supply and a pre-charging control unit; The LED pin is used to connect the cathode of the LED light string, the drain of the high-voltage MOS switch tube M1 is connected to the LED pin, and the gate of the high-voltage MOS switch tube M1 is controlled by a PWM signal; the source of the high-voltage MOS switch tube M1 is connected to the drain of the low-voltage drive current MOS switch tube M2; The gate of the low-voltage drive current MOS switch tube M2 is connected to the output end of the operational amplifier, and the non-inverting input end of the operational amplifier inputs an external reference voltage V ref The source of the low voltage driving current MOS switch tube M2 is connected to one end of the driving resistor, and the other end of the driving resistor is grounded. The inverting input end of the operational amplifier is connected to the source of the low voltage driving current MOS switch tube M2; The source of the pre-charging MOS switch tube M3 is connected to the source of the high-voltage MOS switch tube M1 , the drain of the pre-charging MOS switch tube M3 is connected to the pre-charging power supply, and the gate of the pre-charging MOS switch tube M3 is connected to the pre-charging control unit.

2. The LED backlight driving circuit according to claim 1, characterized in that: The high-voltage MOS switch tube M1 and the low-voltage drive current MOS switch tube M2 are NMOS switch tubes.

3. The LED backlight driving circuit according to claim 1, characterized in that: The pre-charging MOS switch tube M3 is an NMOS switch tube.

4. The LED backlight driving circuit according to claim 1, characterized in that: When the PWM signal controlling the gate of the high-voltage MOS switch tube M1 is at a low level, the pre-charging control unit controls the pre-charging MOS switch tube M3 to be turned on, and the pre-charging power supply at the drain end of the pre-charging MOS switch tube M3 applies a voltage to the source of the high-voltage MOS switch tube M1.

5. The LED backlight driving circuit according to claim 1, characterized in that: The parasitic capacitance C on the LED pin p The charging speed is controlled by the voltage provided by the pre-charging power supply.

6. An LED backlight driving circuit, characterized in that: The LED backlight driving circuit includes: an LED pin, a high-voltage MOS switch tube M1, a low-voltage drive current MOS switch tube M2, an operational amplifier, a driving resistor and a pre-charging module; the pre-charging module includes a pre-charging MOS switch tube M3, a pre-charging power supply and a pre-charging control unit; The LED pin is used to connect the cathode of the LED light string, the drain of the high-voltage MOS switch tube M1 is connected to the LED pin, and the gate of the high-voltage MOS switch tube M1 is controlled by a PWM signal; the source of the high-voltage MOS switch tube M1 is connected to the drain of the low-voltage drive current MOS switch tube M2; The gate of the low-voltage drive current MOS switch tube M2 is connected to the output end of the operational amplifier, and the non-inverting input end of the operational amplifier inputs an external reference voltage V ref The source of the low-voltage drive current MOS switch tube M2 is connected to one end of the drive resistor, and the other end of the drive resistor is connected to an external drive power supply. The inverting input end of the operational amplifier is connected to the source of the low-voltage drive current MOS switch tube M2; The source of the pre-charging MOS switch tube M3 is connected to the source of the high-voltage MOS switch tube M1 , the drain of the pre-charging MOS switch tube M3 is connected to the pre-charging power supply, and the gate of the pre-charging MOS switch tube M3 is connected to the pre-charging control unit.

7. The LED backlight driving circuit according to claim 6, characterized in that: The high-voltage MOS switch tube M1 and the low-voltage drive current MOS switch tube M2 are PMOS switch tubes.

8. The LED backlight driving circuit according to claim 6, characterized in that: The pre-charging MOS switch tube M3 is a PMOS switch tube.

9. The LED backlight driving circuit according to claim 6, characterized in that: When the PWM signal controlling the gate of the high-voltage MOS switch tube M1 is at a low level, the pre-charging control unit controls the pre-charging MOS switch tube M3 to be turned on, and the pre-charging power supply at the drain end of the pre-charging MOS switch tube M3 applies a voltage to the source of the high-voltage MOS switch tube M1.

10. An LED backlight panel, wherein the LED backlight panel uses the LED backlight driving circuit according to any one of claims 1 to 9 to drive LED light-emitting elements to emit light.

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