Backlight dimming circuit, backlight system, and electronic device

Abstract

Provided in the present invention are a backlight dimming circuit, a system, and an electronic device. In the circuit, backlight is provided for a screen by means of an LED light string; a grayscale level of the LED light string is controlled by means of a local dimming module; the magnitude of a peak output current flowing through the LED light string is adjusted by means of a current peak adjustment module; a drain electrode of a first MOS transistor in a feedback module is coupled to a second end of the LED light string, and a source electrode of the first MOS transistor is grounded by means of the local dimming module or the current peak adjustment module; and a first input end of an operational amplifier is coupled to a first end of the current peak adjustment module or a first end of the local dimming module, a second input end of the operational amplifier is coupled to the first end of the local dimming module or the first end of the current peak adjustment module, and an output end of the operational amplifier is coupled to a gate electrode of the first MOS transistor, so as to control voltages at the first input end and second input end of the operational amplifier to be equal. Therefore, without influencing a local dimming signal, the display brightness of a backlight system in a black frame insertion mode is improved by means of adjusting the magnitude of a peak output current flowing through the LED light string.

Description

Backlight dimming circuit, backlight system and electronic equipment Technical Field

[0001] The present invention relates to the field of display technology, and in particular to a backlight dimming circuit, a backlight system and an electronic device. Background Art

[0002] With the advancement of display technology, mini-backlights are increasingly being used in LCD systems. Every time an LCD (Liquid Crystal Display) refreshes an image, the liquid crystal molecules undergo a flip. If the backlight system and the LCD panel don't work well together, the displayed image can exhibit artifacts like ghosting, smearing, and blur. To address this issue, black frame insertion (BFI), a motion blur processing technique, is increasingly being used in display systems.

[0003] In actual applications, after the display system's backlight controller receives the VSync signal (vertical synchronization signal), it sends the dimming data to each driver chip in the backlight system. The driver chip outputs current based on the dimming data to drive the MiniLED lamp beads. Please refer to Figure 1. In black frame insertion (BFI) mode, the driver chip outputs an intermittent PWM current waveform. During black frame insertion, the driver chip outputs a current of 0. When the backlight is illuminated, the driver chip outputs the corresponding current value according to the global or local dimming data. Since the flip time of each row of liquid crystal from top to bottom in the display is different, the starting time of black frame insertion must also be different for each row.

[0004] However, since the black frame insertion time is long in a data frame period and the backlight effective output current time is short, the total brightness of the backlight system will be significantly reduced in the black frame insertion mode, thereby reducing the brightness of the display screen.

[0005] Therefore, how to improve the display brightness of the backlight system in the black frame insertion mode without affecting the local dimming signal has become a technical problem that urgently needs to be solved in the industry.

[0006] Summary of the Invention

[0007] The present invention provides a backlight dimming circuit, a backlight system and an electronic device to solve the technical problem of how to improve the display brightness of the backlight system in the black frame insertion mode without affecting the local dimming signal.

[0008] According to a first aspect of the present invention, a backlight dimming circuit is provided for adjusting the peak output current flowing through an LED light string in a black frame insertion mode, comprising: a local dimming module, a current peak adjustment module, and a feedback module; wherein:

[0009] The LED light string includes N LED lights connected in series, a first end of which is coupled to a first voltage source, and the LED light string is used to provide backlight for the screen, wherein N is an integer greater than or equal to 1;

[0010] The local dimming module includes a total of M local dimming units, which are used to receive a local dimming signal and control i local dimming units in parallel according to the local dimming signal to control the grayscale level of the LED light string, wherein the local dimming signal includes dimming data information; wherein M and i are both integers, and 1≤M, 0≤i≤M;

[0011] The current peak adjustment module is configured to receive a current peak adjustment signal and a backlight mode signal, and adjust the peak output current flowing through the LED light string according to the current peak adjustment signal and the backlight mode signal, wherein the current adjustment signal includes current adjustment coefficient information, and the backlight mode signal includes backlight mode information;

[0012] The feedback module includes a first MOS transistor and an operational amplifier, and is used to control the voltage of the first end of the local dimming module to be equal to the voltage of the first end of the current peak regulation module, wherein:

[0013] The drain of the first MOS transistor is coupled to the second end of the LED light string, and the source thereof is grounded through the local dimming module or the current peak regulation module;

[0014] The first input terminal of the operational amplifier is coupled to the first terminal of the current peak regulation module or the first terminal of the local dimming module, the second input terminal thereof is coupled to the first terminal of the local dimming module or the first terminal of the current peak regulation module, and the output terminal thereof is coupled to the gate of the first MOS tube.

[0015] Optionally, the current peak regulating module includes a total of J current peak regulating units;

[0016] The current peak regulation module is further configured to: control k current peak regulation units in parallel according to the current peak regulation signal to adjust the magnitude of the peak output current flowing through the LED light string, where J and k are both integers, and 1≤J, 0≤k≤J.

[0017] Optionally, the current peak regulating unit includes a first resistor and a first switch;

[0018] A first end of each first resistor is coupled to the source of the first MOS transistor, and a second end of each first resistor is grounded through a corresponding first switch.

[0019] Optionally, the local dimming module is further configured to: output a first signal to the first input terminal of the operational amplifier according to the local dimming signal, wherein the first signal is used to represent the grayscale level of the LED light string.

[0020] Optionally, the current peak regulating unit includes a second MOS tube;

[0021] The drain of each second MOS tube is coupled to the source of the first MOS tube, and the source of each second MOS tube is grounded.

[0022] Optionally, k current peak regulating units are controlled to be connected in parallel according to the current peak regulating signal, specifically:

[0023] The gates of k second MOS tubes are controlled to be connected in sequence according to the adjustment signal.

[0024] Optionally, a third MOS tube is also included;

[0025] The drain of the third MOS transistor is coupled to the first end of the local dimming module, the source thereof is grounded, and the gate thereof is respectively coupled to the gate of the first second MOS transistor and the drain of the third MOS transistor; the second end of the local dimming module is coupled to a second voltage source.

[0026] Optionally, the local dimming unit includes a fifth MOS tube;

[0027] The drain of each fifth MOS transistor is coupled to the source of the first MOS transistor, and the source of each fifth MOS transistor is grounded.

[0028] Optionally, i local dimming units are controlled to be connected in parallel according to the local dimming signal, specifically:

[0029] The gates of i fifth MOS transistors are controlled to be connected in sequence according to the local dimming signal.

[0030] Optionally, a fourth MOS tube is further included; the current peak adjustment unit includes a current source unit and a second switch;

[0031] The first end of each current source unit is coupled to the third voltage source, and the second end of each current source unit is coupled to the first input end of the operational amplifier and the drain of the fourth MOS transistor respectively through the corresponding second switch;

[0032] The source of the fourth MOS transistor is grounded, and the gate thereof is respectively coupled to the gate of the i-th fifth MOS transistor and the drain of the fourth MOS transistor.

[0033] Optionally, the current peak regulation module includes a multiplexer and a voltage regulation unit;

[0034] The input end of the voltage regulating unit receives the current peak regulating signal, and outputs a second reference voltage according to the current peak regulating signal;

[0035] The first terminal of the multiplexer receives a first reference voltage, the second terminal receives a second reference voltage, the output terminal of the multiplexer is coupled to the first input terminal of the operational amplifier, and the control terminal of the multiplexer receives the backlight mode signal; wherein the voltage value of the second reference voltage is greater than the voltage value of the first reference voltage, wherein:

[0036] The multiplexer is configured to:

[0037] If the backlight mode information indicates a normal operating mode, controlling the output terminal to output a first reference voltage;

[0038] If the backlight mode information indicates a black frame insertion mode, the output terminal is controlled to output a second reference voltage.

[0039] The local dimming unit includes a second resistor and a third switch;

[0040] The first end of each second resistor is coupled to the source of the first MOS transistor, and the second end of each second resistor is grounded through the corresponding third switch.

[0041] Optionally, an isolation MOS tube is also included;

[0042] The first end of the isolation MOS transistor is coupled to the second end of the LED light string, the second end thereof is coupled to the drain of the first MOS transistor, and the control end thereof receives a high-voltage isolation transistor enable control signal.

[0043] According to a second aspect of the present invention, a backlight system is provided, comprising the LED light string and the backlight dimming circuit provided in any one of the first aspects of the present invention.

[0044] According to a third aspect of the present invention, an electronic device is provided, comprising the backlight dimming circuit provided by any one of the first aspects of the present invention.

[0045] The backlight dimming circuit, backlight system, and electronic device provided by the present invention provide backlight for the screen through an LED light string, a local dimming module controls the grayscale level of the LED light string, a current peak regulation module adjusts the magnitude of the peak output current flowing through the LED light string, and a feedback module controls the voltage of the first end of the local dimming module to be equal to the voltage of the first end of the current peak regulation module, wherein: the drain of the first MOS transistor is coupled to the second end of the LED light string, and the source thereof is grounded through the local dimming module or the current peak regulation module; the first input end of the operational amplifier is coupled to the first end of the current peak regulation module or the first end of the local dimming module, the second input end thereof is coupled to the first end of the local dimming module or the first end of the current peak regulation module, and the output end thereof is coupled to the gate of the first MOS transistor. Thus, by adjusting the magnitude of the peak output current flowing through the LED light string without affecting the local dimming signal, the display brightness of the backlight system in the black frame insertion mode is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0047] FIG1 is a schematic diagram of a backlight dimming circuit structure according to an embodiment of the present invention;

[0048] FIG2 is a schematic diagram of the backlight dimming circuit structure according to the first embodiment of the present invention;

[0049] 3 is a schematic diagram of the backlight dimming circuit structure in a second embodiment of the present invention;

[0050] FIG4 is a schematic diagram of a backlight dimming circuit structure in a third embodiment of the present invention;

[0051] 5 is a schematic diagram of the backlight dimming circuit structure in a fourth embodiment of the present invention;

[0052] FIG. 6 is a schematic diagram of a backlight dimming circuit structure in a fifth embodiment of the present invention.

[0053] FIG7 is a waveform diagram of a backlight dimming circuit in the prior art in a working state;

[0054] FIG8 is a waveform diagram of the backlight dimming circuit in FIG1 in a working state;

[0055] Description of reference numerals:

[0056] 10-LED light string;

[0057] 20- local dimming module;

[0058] 30-current peak regulation module;

[0059] 40-Feedback module;

[0060] M1-first MOS tube;

[0061] M2-second MOS tube;

[0062] M3-third MOS tube;

[0063] M4-fourth MOS tube;

[0064] M5-fifth MOS tube;

[0065] 101- Operational Amplifier;

[0066] Vdcdc-first voltage source;

[0067] VCC1-second voltage source;

[0068] VCC2-third voltage source;

[0069] R1-first resistor;

[0070] R2-second resistor;

[0071] SW1-first switch;

[0072] SW2-second switch;

[0073] SW3-third switch;

[0074] 301-Multiplexer;

[0075] 302-voltage regulation unit;

[0076] Vref1-first reference voltage;

[0077] Vref2-second reference voltage;

[0078] HV-isolation MOS tube. DETAILED DESCRIPTION

[0079] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0080] The terms "first," "second," "third," "fourth," and the like (if any) in the description and claims of the present invention and in the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. In addition, the terms "including" and "having," as well as any variations thereof, are intended to cover non-exclusive inclusions, e.g., a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to these processes, methods, products, or apparatus.

[0081] The technical solution of the present invention is described in detail below with reference to specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0082] In view of the technical problem that it is difficult to improve the display brightness of the backlight system in the black frame insertion mode without affecting the local dimming signal in the prior art, the present invention provides a backlight dimming circuit, a backlight system and an electronic device. The circuit provides backlight for the screen through an LED light string, a local dimming module controls the grayscale level of the LED light string, a current peak regulation module adjusts the magnitude of the peak output current flowing through the LED light string, and a feedback module controls the voltage of the first end of the local dimming module to be equal to the voltage of the first end of the current peak regulation module, wherein: the drain of the first MOS tube is coupled to the second end of the LED light string, and the source thereof is grounded through the local dimming module or the current peak regulation module; the first input end of the operational amplifier is coupled to the first end of the current peak regulation module or the first end of the local dimming module, the second input end thereof is coupled to the first end of the local dimming module or the first end of the current peak regulation module, and the output end thereof is coupled to the gate of the first MOS tube. Therefore, by adjusting the magnitude of the peak output current flowing through the LED light string without affecting the local dimming signal, the display brightness of the backlight system in the black frame insertion mode is improved.

[0083] 1 , an embodiment of the present invention provides a backlight dimming circuit for adjusting the peak output current flowing through an LED light string 10 in a black frame insertion mode, comprising: a local dimming module 20 , a current peak adjustment module 30 , and a feedback module 40 ; wherein:

[0084] The LED light string 10 includes N LED lights connected in series, a first end of which is coupled to a first voltage source Vdcdc, and the LED light string 10 is used to provide backlight for a screen, where N is an integer greater than or equal to 1;

[0085] The local dimming module 20 includes a total of M local dimming units, which are used to receive a local dimming signal and control i local dimming units in parallel according to the local dimming signal to control the grayscale level of the LED light string 10, wherein the local dimming signal includes dimming data information; wherein M and i are both integers, and 1≤M, 0≤i≤M;

[0086] The current peak adjustment module 30 is configured to receive a current peak adjustment signal and a backlight mode signal, and adjust the peak output current flowing through the LED light string 10 according to the current peak adjustment signal and the backlight mode signal, wherein the current adjustment signal includes current adjustment coefficient information, and the backlight mode signal includes backlight mode information;

[0087] The feedback module 40 includes a first MOS transistor M1 and an operational amplifier 101, and is used to control the voltages of the first terminal of the local dimming module 20 and the first terminal of the current peak regulation module 30 to be equal, wherein:

[0088] The drain of the first MOS transistor M1 is coupled to the second end of the LED light string 10 , and the source thereof is grounded through the local dimming module 20 or the current peak regulation module 30 ;

[0089] The first input terminal of the operational amplifier 101 is coupled to the first terminal of the current peak regulation module 30 or the first terminal of the local dimming module 20, the second input terminal thereof is coupled to the first terminal of the local dimming module 20 or the first terminal of the current peak regulation module 30, and the output terminal thereof is coupled to the gate of the first MOS transistor M1.

[0090] The voltage at the first terminal of the local dimming module 20 and the first terminal of the current peak regulation module 30 are controlled to be equal by utilizing the virtual short characteristics of the non-inverting input and the inverting input of the operational amplifier 101. This allows for more convenient control of the current flowing through the LED light string 10. In one example, the first input of the operational amplifier 101 is the non-inverting input, and the second input is the inverting input.

[0091] In the example shown in FIG1 , the first MOS transistor M1 is an NMOS transistor. Of course, the present invention is not limited thereto, and an IGBT transistor or the like may also be used.

[0092] Regarding the current adjustment coefficient information, it should be understood that, in actual use, the current adjustment coefficient information can be defined according to the parameters of each screen, and the present invention is not limited to this.

[0093] The specific structures of the current peak regulating module 30 and the local dimming module 20 are now described. It should be understood that the present invention is not limited to the specific combination of circuits. The circuits in the local dimming module 20 in each embodiment can be replaced with each other, and the circuits in the current peak regulating module 30 can also be replaced with each other.

[0094] In one embodiment, the current peak regulating module 30 includes a total of J current peak regulating units;

[0095] The current peak regulation module 30 is further configured to: control k current peak regulation units in parallel according to the current peak regulation signal to adjust the peak output current flowing through the LED light string 10, where J and k are both integers, and 1≤J, 0≤k≤J.

[0096] On this basis, in a specific implementation, please refer to FIG2 , the current peak adjustment unit includes a first resistor R1 and a first switch SW1 ;

[0097] A first end of each first resistor R1 is coupled to the source of the first MOS transistor M1 , and a second end of each first resistor R1 is grounded through a corresponding first switch SW1 .

[0098] Of course, the present invention is not limited to a specific connection form. In another specific embodiment, the first end of each first switch SW1 is coupled to the source of the first MOS transistor M1, and the second end of each first switch SW1 is grounded through the corresponding first resistor R1.

[0099] The current peak regulation module 30 is further configured to control the closing of k first switches SW1 according to the current peak regulation signal, so as to control the magnitude of the peak output current flowing through the LED light string 10 .

[0100] In this case, the local dimming module 20 is further configured to output a first signal to the first input terminal of the operational amplifier 101 according to the local dimming signal, wherein the first signal is used to represent the grayscale level of the LED light string 10 .

[0101] In some examples, the local dimming unit is a resistor, and the local dimming module 20 controls i local dimming units to be connected in series according to the local dimming signal, or controls resistors of different resistance values ​​to be coupled to the first input terminal of the operational amplifier 101 to control the grayscale level of the LED light string.

[0102] In this embodiment, the first signal can be understood as a voltage value, which is used to represent the grayscale level of the LED light string 10. Since the voltage of the first terminal of the local dimming module 20 is equal to the voltage of the first terminal of the current peak regulation module 30, in this case:

[0103] If the number of the first resistors R1 connected in parallel in the current peak regulating module 30 remains unchanged, the current flowing through the LED light string 10 will change with the corresponding grayscale level;

[0104] If the voltage value corresponding to the first signal remains unchanged, the current flowing through the LED light string 10 will change according to the number of first resistors R1 connected in parallel in the current peak regulation module 30 .

[0105] In another specific embodiment, referring to FIG3 , the local dimming unit can be a current source (the local dimming module 20 can control the number of current sources connected in parallel). On this basis, the current output by the local dimming module 20 can be used to control the current flowing through the LED light string 10 .

[0106] In one embodiment, the current peak regulating unit includes a second MOS transistor M2;

[0107] The drain of each second MOS transistor M2 is coupled to the source of the first MOS transistor M1 , and the source of each second MOS transistor M2 is grounded.

[0108] In this case, the above-mentioned control of k current peak regulating units in parallel according to the current peak regulating signal is specifically as follows:

[0109] The gates of the k second MOS transistors M2 are controlled to be connected in sequence according to the adjustment signal.

[0110] The k parallel-connected second MOS transistors M2 can be regarded as a single MOS transistor, and the width-to-length ratio of the single MOS transistor is equivalent to k times the width-to-length ratio of the second MOS transistor M2. To utilize this characteristic, in one embodiment, the backlight dimming circuit further includes a third MOS transistor M3;

[0111] The drain of the third MOS transistor M3 is coupled to the first end of the local dimming module 20 , the source thereof is grounded, and the gate thereof is coupled to the gate of the first second MOS transistor M2 and the drain of the third MOS transistor M3 .

[0112] Of course, the present invention does not limit the specific parallel connection mode of the second MOS transistor M2. In other embodiments, the current peak regulation module may also be:

[0113] The drain of each second MOS transistor M2 is coupled to the source of the first MOS transistor M1 through a switch, the gates of each second MOS transistor M2 are connected, and the source of each second MOS transistor M2 is grounded.

[0114] In other implementations, the current peak regulation module may also be:

[0115] The drain of each second MOS transistor M2 is coupled to the source of the first MOS transistor M1 , the gate of each second MOS transistor M2 is connected, and the source of each second MOS transistor M2 is grounded through a switch.

[0116] In this case, the above-mentioned control of k current peak regulating units in parallel according to the current peak regulating signal may be specifically as follows:

[0117] The drains or sources of the k second MOS transistors M2 are controlled to be connected in sequence according to the adjustment signal.

[0118] 3 , the second terminal of the local dimming module 20 is coupled to a second voltage source VCC1 . In an actual circuit, the voltage provided by the second voltage source VCC1 is generally lower than the voltage provided by the first voltage source Vdcdc.

[0119] In this embodiment, the third MOS transistor M3 and the current peak regulation module 30 form a current mirror. In this case:

[0120] If the number of the second MOS transistors M2 connected in parallel in the current peak regulation module 30 remains unchanged, the current flowing through the LED light string 10 will change its grayscale level correspondingly with the current output by the local dimming module 20;

[0121] If the current value output by the local dimming module 20 remains unchanged, the current flowing through the LED light string 10 will vary according to the number of second MOS transistors M2 connected in parallel in the current peak regulation module 30 .

[0122] In another specific embodiment, referring to FIG4 , the local dimming unit includes a fifth MOS transistor M5 ;

[0123] The drain of each fifth MOS transistor M5 is coupled to the source of the first MOS transistor M1 , and the source of each fifth MOS transistor M5 is grounded.

[0124] In this case, i local dimming units are controlled to be connected in parallel according to the local dimming signal, specifically:

[0125] The gates of i fifth MOS transistors M5 are controlled to be connected in sequence according to the local dimming signal.

[0126] Similarly, the characteristic that the width-to-length ratio of a single MOS transistor formed by i fifth MOS transistors M5 is equal to i times the width-to-length ratio of the fifth MOS transistor M5 can be utilized. In one embodiment, the backlight dimming circuit further includes a fourth MOS transistor M4; the current peak adjustment unit includes a current source unit and a second switch SW2;

[0127] The first end of each current source unit is coupled to the third voltage source VCC2, and the second end of each current source unit is coupled to the first input end of the operational amplifier 101 and the drain of the fourth MOS transistor M4 through the corresponding second switch SW2;

[0128] The source of the fourth MOS transistor M4 is grounded, and the gate thereof is coupled to the gate of the i-th fifth MOS transistor M5 and the drain of the fourth MOS transistor M4 .

[0129] In an actual circuit, the voltage value provided by the third voltage source VCC2 is usually smaller than the voltage value provided by the first voltage source Vdcdc.

[0130] The current peak regulation module 30 is further configured to control the closing of k second switches SW2 according to the current peak regulation signal, so as to control the magnitude of the peak output current flowing through the LED light string 10 .

[0131] In this embodiment, the fourth MOS transistor M4 and the local dimming module 20 form a current mirror. In this case:

[0132] If the current value output by the current peak regulating module 30 to the fourth MOS transistor M4 remains unchanged, the current flowing through the LED light string 10 will change with the number of the fifth MOS transistors M5 connected in parallel, wherein the number of the fifth MOS transistors M5 connected in parallel corresponds to different grayscale levels;

[0133] If the number of the fifth MOS transistors M5 connected in parallel in the local dimming module 20 remains unchanged, the current flowing through the LED light string 10 will change according to the magnitude of the current output by the current peak regulation module 30 to the fourth MOS transistor M4.

[0134] In other embodiments, please refer to FIG5 , the current peak regulation module 30 includes a multiplexer 301 and a voltage regulation unit 302 ;

[0135] The input terminal of the voltage regulating unit 302 receives the current peak regulating signal, and outputs a second reference voltage Vref2 according to the current peak regulating signal;

[0136] The first terminal of the multiplexer 301 receives the first reference voltage Vref1, the second terminal receives the second reference voltage Vref2, the output terminal of the multiplexer 301 is coupled to the first input terminal of the operational amplifier 101, and the control terminal of the multiplexer 301 receives the backlight mode signal; wherein the voltage value of the second reference voltage Vref2 is greater than the voltage value of the first reference voltage Vref1, wherein:

[0137] The multiplexer 301 is configured as follows:

[0138] If the backlight mode information indicates a normal operating mode, controlling the output terminal to output a first reference voltage Vref1;

[0139] If the backlight mode information indicates a black frame insertion mode, the output terminal is controlled to output a second reference voltage Vref2 .

[0140] In one example, the voltage value of the second reference voltage Vref2 is L times the voltage value of the first reference voltage Vref1, where L is the current adjustment coefficient. In some examples, the current adjustment coefficient can also be set according to the grayscale level of the LED light string 10, which is not limited by the present invention.

[0141] In this case, the voltage at the first end of the local dimming module 20 is the first reference voltage Vref1 or the second reference voltage Vref2. In this case, in one embodiment, referring to FIG. 5 , the local dimming unit includes a second resistor R2 and a third switch SW3 ;

[0142] A first end of each second resistor R2 is coupled to the source of the first MOS transistor M1 , and a second end of each second resistor R2 is grounded via a corresponding third switch SW3 .

[0143] In this embodiment, if the voltage value output by the current peak regulation module 30 remains unchanged, the current flowing through the LED light string 10 will change with the number of second resistors R2 connected in parallel, wherein the number of second resistors R2 connected in parallel corresponds to different grayscale levels;

[0144] If the number of the second resistors R2 connected in parallel in the local dimming module 20 remains unchanged, the current flowing through the LED light string 10 will change according to the voltage value output by the current peak regulation module 30 .

[0145] In summary, the current flowing through the LED light string 10 can be controlled by the local dimming module 20 and / or the current peak adjustment module 30. In the circuit design, the characteristics of the internal circuit of the local dimming module 20 are utilized to improve the display brightness of the backlight system in the black frame insertion mode by adjusting the peak output current flowing through the LED light string 10 without affecting the local dimming signal (which can also be understood as not affecting the working state of the local dimming module 20).

[0146] Generally, the voltage value of the voltage source connected in series to the LED light string 10 is relatively high (ie, the LED light string 10 is powered by a high voltage). In the above embodiment, the first MOS transistor M1 is used as a high-voltage transistor.

[0147] In other embodiments, the first MOS transistor M1 may also be used as a low-voltage transistor, and the feedback module 40 , the local dimming module 20 , and the current peak regulation module 30 are powered by a low voltage. In this case, high and low voltage isolation of the circuit is also required.

[0148] In one embodiment, referring to FIG6 , the backlight dimming circuit further includes an isolation MOS transistor HV;

[0149] The first end of the isolation MOS transistor HV is coupled to the second end of the LED light string 10 , the second end thereof is coupled to the drain of the first MOS transistor M1 , and the control end thereof receives a high-voltage isolation transistor enable control signal.

[0150] To achieve the black frame insertion mode, the current flowing through the LED light string 10 is controlled to be zero for a set time. In one example, the first MOS transistor M1 can be controlled to be disconnected. In another example, the isolation MOS transistor HV can also be controlled to be disconnected.

[0151] It should be understood that the present invention does not limit the specific method of controlling the current flowing through the LED light string 10 to be 0 within a set time, and those skilled in the art can set a suitable circuit as needed.

[0152] In order to better reflect the working effect of the present invention, the working effect of the backlight dimming circuit of the present invention is now described with reference to the waveform diagrams shown in FIG7 and FIG8 :

[0153] Among them, the waveform diagram shown in FIG7 is a current waveform diagram of the backlight dimming circuit of the prior art flowing through the LED light string 10 (taking three strings of LED light strings 10 as an example) in the normal working mode and the black frame insertion mode; the waveform diagram shown in FIG8 is a current waveform diagram of the backlight dimming circuit shown in FIG1 flowing through the LED light string 10 in the normal working mode and the black frame insertion mode, which are described in detail as follows:

[0154] ROW_1, you can understand the current signal flowing through the first LED string 10;

[0155] ROW_2, can understand the current signal flowing through the second LED string 10;

[0156] ROW_3, you can understand the current signal flowing through the third LED string 10;

[0157] DIMMING_DATA, which can be understood as the local dimming signal;

[0158] Vsync can be understood as vertical synchronization signal;

[0159] Among them, in the display screen, the flipping time of each row of liquid crystal from top to bottom is different, so the starting time of inserting the black frame of each string of lights must also be different.

[0160] Referring to Figure 7 , although the prior art also implements how, starting from receiving a vertical synchronization signal, the LED light string 10 corresponding to each row of liquid crystals receives current (i.e., lights up at different times) based on the different flip times of each row of liquid crystals, thereby allowing the backlight circuit to match the liquid crystal flipping, thereby avoiding image blur caused by liquid crystal flipping and improving the display quality, in black frame insertion mode, however, the black frame insertion time in a data frame is longer, which results in a shorter lighting time for the LED light string 10. The current value received by the LED light string 10 is the same as the current value received in normal operating mode. Therefore, in black frame insertion mode, the brightness of the display will be significantly reduced.

[0161] 8 , the circuit provided by the present invention can control the current value received by the LED light string 10 in the black frame insertion mode according to a preset current adjustment coefficient, thereby ensuring that the brightness of the display image does not decrease in the black frame insertion mode.

[0162] In addition, an embodiment of the present invention further provides a backlight system, including the LED light string and the above-mentioned backlight dimming circuit.

[0163] In addition, an embodiment of the present invention further provides an electronic device including the above-mentioned backlight dimming circuit. As an example, the device can be applied to a display screen, and of course can also be applied to other devices requiring backlight dimming.

[0164] In summary, in an embodiment of the present invention, an LED light string is used to provide backlight for the screen, a local dimming module controls the grayscale level of the LED light string, a current peak regulation module adjusts the magnitude of the peak output current flowing through the LED light string, and a feedback module controls the voltage of the first end of the local dimming module to be equal to the voltage of the first end of the current peak regulation module, wherein: the drain of the first MOS tube is coupled to the second end of the LED light string, and its source is grounded through the local dimming module or the current peak regulation module; the first input end of the operational amplifier is coupled to the first end of the current peak regulation module or the first end of the local dimming module, the second input end of the operational amplifier is coupled to the first end of the local dimming module or the first end of the current peak regulation module, and the output end of the operational amplifier is coupled to the gate of the first MOS tube. Thus, by adjusting the magnitude of the peak output current flowing through the LED light string without affecting the local dimming signal, the display brightness of the backlight system in the black frame insertion mode is improved.

[0165] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A backlight dimming circuit for adjusting the peak output current flowing through an LED light string in a black frame insertion mode, characterized in that: include: Local dimming module, current peak regulation module and feedback module; wherein: The LED light string comprises N LED lights connected in series, a first end of which is coupled to a first voltage source, and the LED light string is used to provide backlight for the screen, wherein N is an integer greater than or equal to 1; The local dimming module includes a total of M local dimming units, which are used to receive a local dimming signal and control i local dimming units to be connected in parallel according to the local dimming signal to control the grayscale level of the LED light string, wherein the local dimming signal includes dimming data information; wherein M and i are both integers, and 1≤M, 0≤i≤M; The current peak adjustment module is used to receive a current peak adjustment signal and a backlight mode signal, and adjust the peak output current flowing through the LED light string according to the current peak adjustment signal and the backlight mode signal, wherein the current adjustment signal includes current adjustment coefficient information, and the backlight mode signal includes backlight mode information; The feedback module includes a first MOS tube and an operational amplifier, and is used to control the voltage of the first end of the local dimming module to be equal to the voltage of the first end of the current peak adjustment module, wherein: The drain of the first MOS tube is coupled to the second end of the LED light string, and the source thereof is grounded through the local dimming module or the current peak adjustment module; The first input terminal of the operational amplifier is coupled to the first terminal of the current peak regulation module or the first terminal of the local dimming module, the second input terminal thereof is coupled to the first terminal of the local dimming module or the first terminal of the current peak regulation module, and the output terminal thereof is coupled to the gate of the first MOS tube.

2. The backlight dimming circuit according to claim 1, characterized in that: The current peak value regulating module includes a total of J current peak value regulating units; The current peak regulation module is also configured to: control k current peak regulation units in parallel according to the current peak regulation signal to adjust the peak output current flowing through the LED light string, where J and k are both integers, and 1≤J, 0≤k≤J.

3. The backlight dimming circuit according to claim 2, characterized in that: The current peak value adjustment unit includes a first resistor and a first switch; The first end of each first resistor is coupled to the source of the first MOS tube. The second ends of the switches are grounded through the corresponding first switches.

4. The backlight dimming circuit according to claim 3, characterized in that: The local dimming module is further configured to: output a first signal to a first input terminal of the operational amplifier according to the local dimming signal, wherein the first signal is used to represent a grayscale level of the LED light string.

5. The backlight dimming circuit according to claim 2, characterized in that: The current peak regulating unit includes a second MOS tube; The drain of each second MOS tube is coupled to the source of the first MOS tube, and the source of each second MOS tube is grounded.

6. The backlight dimming circuit according to claim 5, characterized in that: According to the current peak value adjustment signal, k current peak value adjustment units are controlled to be connected in parallel, specifically: The gates of k second MOS tubes are controlled to be connected in sequence according to the adjustment signal.

7. The backlight dimming circuit according to claim 6, characterized in that: Also includes a third MOS tube; The drain of the third MOS tube is coupled to the first end of the local dimming module, the source thereof is grounded, and the gate thereof is respectively coupled to the gate of the first second MOS tube and the drain of the third MOS tube; The second end of the local dimming module is coupled to a second voltage source.

8. The backlight dimming circuit according to claim 2, characterized in that: The local dimming unit includes a fifth MOS tube; The drain of each fifth MOS tube is coupled to the source of the first MOS tube, and the source of each fifth MOS tube is grounded.

9. The backlight dimming circuit according to claim 8, characterized in that: According to the local dimming signal, i local dimming units are controlled to be connected in parallel, specifically: The gates of i fifth MOS tubes are controlled to be connected in sequence according to the local dimming signal.

10. The backlight dimming circuit according to claim 9, characterized in that: It also includes a fourth MOS tube; the current peak adjustment unit includes a current source unit and a second switch; The first end of each current source unit is coupled to the third voltage source, and the second end of each current source unit is respectively coupled to the first input end of the operational amplifier and the drain of the fourth MOS tube through the corresponding second switch; The source of the fourth MOS tube is grounded, and the gate thereof is respectively coupled to the gate of the i-th fifth MOS tube and the drain of the fourth MOS tube.

11. The backlight dimming circuit according to claim 1, characterized in that: The current peak regulation module includes a multiplexer and a voltage regulation unit; The input end of the voltage regulating unit receives the current peak regulating signal, and outputs a second reference voltage according to the current peak regulating signal; The first end of the multiplexer receives the first reference voltage, the second end receives the second reference voltage, the output end is coupled to the first input end of the operational amplifier, and the control end receives the backlight mode signal; wherein the voltage value of the second reference voltage is greater than the voltage value of the first reference voltage, wherein: The multiplexer is configured as: If the backlight mode information indicates a normal working mode, controlling the output terminal to output a first reference voltage; If the backlight mode information indicates a black frame insertion mode, the output terminal is controlled to output a second reference voltage.

12. The backlight dimming circuit according to claim 11, characterized in that: The local dimming unit includes a second resistor and a third switch; The first end of each second resistor is coupled to the source of the first MOS tube, and the second end of each second resistor is grounded through the corresponding third switch.

13. The backlight dimming circuit according to any one of claims 1 to 12, characterized in that: It also includes isolated MOS tubes; The first end of the isolation MOS tube is coupled to the second end of the LED light string, the second end of the isolation MOS tube is coupled to the drain of the first MOS tube, and the control end of the isolation MOS tube receives a high-voltage isolation tube enable control signal.

14. A backlight system, characterized in that: It comprises the LED light string and the backlight dimming circuit as described in any one of claims 1-13.

15. An electronic device, characterized in that: Comprising the backlight dimming circuit as described in any one of claims 1-13.

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