Backlight driving circuit and display device

Abstract

The present disclosure relates to the technical fields of virtual reality and augmented reality, and provides a backlight driving circuit and a display device. In the present disclosure, the backlight driving circuit is electrically connected to a backlight source; the backlight driving circuit at least comprises a black frame insertion driving sub-circuit and a reverse current cut-off sub-circuit; the black frame insertion driving sub-circuit is electrically connected to the reverse current cut-off sub-circuit; the black frame insertion driving sub-circuit is configured to control, in response to a backlight black frame insertion signal flowing through the reverse current cut-off sub-circuit, on and off of light-emitting elements in the backlight source; and the reverse current cut-off sub-circuit is configured to guide to a first power supply voltage end the reverse current reversely flowing into from the black frame insertion driving sub-circuit when the backlight black frame insertion signal is converted into a black frame insertion mode from a normally open mode.

Description

Backlight driving circuit and display device Technical Field

[0001] The present disclosure belongs to the technical field of virtual reality and augmented reality, and particularly relates to a backlight driving circuit and a display device. Background Art

[0002] In display products, screen latency is a key performance parameter. The higher the screen latency, the more noticeable the resulting ghosting. To achieve lower screen latency and address the ghosting issue caused by response time, backlight blackout can be used.

[0003] With the widespread application of backlight black insertion technology in a large number of display products, the problems it causes have gradually been discovered, especially in small-sized, edge-type backlight products, where the backlight black insertion signal is easily burned out. Summary of the Invention

[0004] The present disclosure aims to solve at least one of the technical problems existing in the prior art and provides a backlight driving circuit and a display device.

[0005] In a first aspect, the technical solution adopted to solve the technical problem of the present disclosure is a backlight driving circuit electrically connected to a backlight source; wherein the backlight driving circuit includes at least a black insertion driving subcircuit and a reverse current blocking subcircuit; the black insertion driving subcircuit and the reverse current blocking subcircuit are electrically connected;

[0006] The black insertion driving sub-circuit is configured to control the lighting and extinguishing of the light-emitting element in the backlight source in response to the backlight black insertion signal flowing through the reverse current cut-off sub-circuit;

[0007] The reverse current cutoff sub-circuit is configured to introduce the reverse current flowing in reverse from the black insertion driving sub-circuit into the first power supply voltage terminal when the backlight black insertion signal is switched from the normally-on mode to the black insertion mode.

[0008] In some embodiments, the black insertion driving subcircuit includes n switch units; n is a positive integer greater than or equal to 1; the backlight source includes multiple groups of light-emitting element groups, each of which includes multiple light-emitting elements;

[0009] One switch unit is electrically connected to one group of light emitting element groups, and different switch units are electrically connected to different groups of light emitting element groups.

[0010] In some embodiments, the plurality of light-emitting elements in each of the light-emitting element groups are connected in series;

[0011] The first end of the switch unit is electrically connected to the second electrode of one of the light-emitting elements in the light-emitting element group, the second end of the switch element is electrically connected to the first power supply voltage end, and the second end of the switch element is electrically connected to the reverse current cutoff sub-circuit.

[0012] In some embodiments, the switch unit includes a transistor and a load resistor;

[0013] The first electrode of the transistor is electrically connected to the first end of the load resistor, the second electrode is electrically connected to the second electrode of one of the light-emitting elements in the group of light-emitting elements, and the control electrode is electrically connected to the reverse current blocking sub-circuit;

[0014] The second end of the load resistor is electrically connected to the first power supply voltage end.

[0015] In some embodiments, the reverse current blocking subcircuit includes a first resistor and a second resistor; the resistance of the first resistor is greater than the resistance of the second resistor;

[0016] A first end of the first resistor is electrically connected to an external backlight black insertion signal source, and a second end thereof is electrically connected to the control electrodes of the transistors;

[0017] A first end of the second resistor is electrically connected to the control electrode of each of the transistors, and a second end thereof is electrically connected to the first power supply voltage end.

[0018] In some embodiments, the reverse current cutoff subcircuit further includes a cutoff capacitor;

[0019] The first plate of the cut-off capacitor is electrically connected to the backlight black insertion signal source, and the second plate is electrically connected to the first power supply voltage terminal.

[0020] In some embodiments, the relationship between the resistance value of the first resistor, the resistance value of the second resistor, the reverse current of the black insertion driving sub-circuit, and the turn-on voltage of the transistor satisfies the following formula:

[0021] U 开 =2R×r×I 反 / (R+r), where R represents the resistance of the first resistor and r represents the resistance of the second resistor; U 开 represents the turn-on voltage of the transistor, I 反 Represents the reverse current of the black insertion driving sub-circuit.

[0022] In some embodiments, the relationship between the minimum capacitance of the cut-off capacitor and the resistance of the first resistor satisfies the following formula:

[0023] C=t / R, where C represents the minimum capacitance of the cut-off capacitor, t represents unit time, and R represents the resistance of the first resistor.

[0024] In a second aspect, an embodiment of the present disclosure further provides a display device comprising a backlight source, a display panel, and at least one backlight driving circuit as described in any one of the first aspects.

[0025] In some embodiments, the display device further includes a backlight control circuit configured to provide the backlight black insertion signal to the reverse current cutoff sub-circuit.

[0026] In some embodiments, the backlight control circuit includes a backlight black insertion signal source; the backlight driving circuit includes multiple;

[0027] Each of the reverse current cutoff sub-circuits in the plurality of backlight driving circuits is electrically connected to the same backlight black insertion signal source.

[0028] In some embodiments, the display panel is a liquid crystal display panel.

[0029] In some embodiments, the backlight source is located on a side of the liquid crystal display panel that is perpendicular to the light emitting direction.

[0030] In some embodiments, the backlight source includes N groups of light-emitting element groups, each of which includes M light-emitting elements; wherein the value range of N is between 1 and 4, and the value range of M is between 1 and 4.

[0031] In some embodiments, the display device is a virtual reality device or an augmented reality device. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG1 is a partial circuit structure diagram of a backlight control module of a related direct-lit backlight source;

[0033] FIG2 is a partial structural diagram of a related edge-type backlight driving circuit;

[0034] FIG3 is a structural diagram of an exemplary backlight driving circuit provided in an embodiment of the present disclosure;

[0035] FIG4 is a schematic diagram of a black insertion driving sub-circuit provided in an embodiment of the present disclosure;

[0036] FIG5 is a specific circuit structure diagram of a black insertion driving sub-circuit provided in an embodiment of the present disclosure;

[0037] FIG6 a is a specific structural diagram of an exemplary backlight driving circuit provided by an embodiment of the present disclosure;

[0038] FIG6 b is a schematic diagram of an exemplary reverse current equivalent circuit provided by an embodiment of the present disclosure;

[0039] FIG7 a is a specific structural diagram of an exemplary backlight driving circuit provided by an embodiment of the present disclosure;

[0040] FIG7 b is a schematic diagram of an exemplary reverse current equivalent circuit provided by an embodiment of the present disclosure;

[0041] FIG8 a is a circuit diagram of an ideal cut-off capacitor;

[0042] FIG8 b is a circuit diagram of an actual cut-off capacitor;

[0043] FIG9 is a schematic diagram of a display device provided by an embodiment of the present disclosure;

[0044] FIG10 is a schematic diagram of a backlight driving circuit driving a backlight source according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. The components of the embodiments of the present disclosure generally described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present disclosure provided in the drawings is not intended to limit the scope of the disclosure for which protection is sought, but merely represents selected embodiments of the present disclosure. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present disclosure.

[0046] Unless otherwise defined, the technical or scientific terms used in this disclosure should have the usual meanings understood by people with ordinary skills in the field to which this disclosure belongs. The words "first", "second" and similar words used in this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one", "an" or "the" do not indicate a quantity limitation, but rather indicate the existence of at least one. Words such as "include" or "comprise" mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0047] In this disclosure, "multiple or several" refers to two or more. "And / or" describes the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, or B exists alone. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0048] In the related art, as shown in Figure 1, it is a partial circuit architecture diagram of the backlight control module of the related direct-type backlight source. The direct-type backlight source has more light-emitting elements than the edge-type backlight source. Under the premise that the backlight brightness remains unchanged, the direct-type backlight source requires less driving current than the edge-type backlight source. In addition, the backlight control circuit of the direct-type backlight source has more backlight black insertion signal sources, and a backlight black insertion signal source is set in each LED partition. Therefore, for direct-type backlight products, it is not easy to cause the backlight black insertion signal to burn out.

[0049] It should be noted that, under the premise of consistent backlight brightness, the greater the driving current required by the backlight source and the fewer the number of backlight black insertion signal sources, the more likely it is to cause the backlight black insertion signal burnout problem.

[0050] In the related art, as shown in Figure 2, which is a partial architecture diagram of a related edge-lit backlight driver circuit, backlight driver circuit 01 receives a backlight black insertion signal PWM from a backlight black insertion signal source to control the lighting and extinguishing of the light-emitting elements in the backlight source. Backlight driver circuit 01 has two operating modes: a normally-on mode in which the light-emitting elements are constantly on, and a black insertion mode in which backlight black insertion is performed.

[0051] For example, as shown in Figure 2, when the backlight driver circuit 01 rapidly switches from normally-on mode to black insertion mode, the backlight black insertion signal PWM suddenly changes from a continuous first level (e.g., a high level) to a second level (e.g., a low level). This causes the parasitic capacitance between the second electrode and the control electrode of the MOS transistor in the backlight driver circuit 01 to instantly discharge and flow back into the backlight black insertion signal PWM (i.e., the backlight black insertion signal source). Small-sized, edge-lit backlight products require a high drive current for the backlight source, so the reverse current caused by the instantaneous discharge of the parasitic capacitance is large, directly causing the backlight black insertion signal PWM to burn out.

[0052] At the same time, in the black insertion mode, as the backlight black insertion signal PWM changes between high and low levels, there is also a risk of insufficient charging of the parasitic capacitance of the transistor MOS. This is mainly because when the backlight black insertion signal PWM is at a low level (second level), the parasitic capacitance between the second electrode and the control electrode of the transistor MOS is in a charged state (Vds = V OUT), when the backlight black insertion signal PWM is instantaneously boosted to a high level (first level), the charge state of the parasitic capacitor will be destroyed, causing the parasitic capacitor to discharge, hindering the rise of the backlight black insertion signal PWM, thereby extending the turn-on time of the transistor MOS in the backlight driving circuit 01, reducing the actual light-emitting time of the light-emitting element in the backlight source, and ultimately resulting in insufficient brightness of the backlight source.

[0053] In view of this, embodiments of the present disclosure provide a backlight driver circuit that substantially eliminates one or more of the problems caused by the limitations and defects of related technologies. Specifically, embodiments of the present disclosure incorporate a reverse current blocking subcircuit. When the backlight black insertion signal switches from a normally-on mode to a black insertion mode, the reverse current blocking subcircuit directs the reverse current flowing from the black insertion driver subcircuit to the first power supply voltage terminal. This prevents the parasitic capacitance of the transistor from instantaneously discharging back into the backlight black insertion signal source, potentially damaging the backlight black insertion signal.

[0054] The structure of the backlight driving circuit provided by the embodiment of the present disclosure is described in detail below.

[0055] Figure 3 is an architectural diagram of an exemplary backlight driving circuit provided in an embodiment of the present disclosure. As shown in Figure 3, the backlight driving circuit 1 can be understood as a backlight control chip, which is electrically connected to the backlight source (not shown in the figure) during actual application and is configured to control the lighting and extinguishing of the light-emitting elements in the backlight source.

[0056] As shown in FIG3 , the backlight driving circuit 1 at least includes a black insertion driving sub-circuit 11 and a reverse current blocking sub-circuit 12 ; wherein the black insertion driving sub-circuit 11 and the reverse current blocking sub-circuit 12 are electrically connected.

[0057] The black insertion driving sub-circuit 11 is configured to control the lighting and extinguishing of the light-emitting elements in the backlight source in response to the backlight black insertion signal PWM flowing through the reverse current cutoff sub-circuit 12 .

[0058] Here, the black insertion driving sub-circuit 11 is electrically connected to the light-emitting elements in the backlight source. The black insertion driving sub-circuit 11 receives the backlight black insertion signal PWM from the reverse current cut-off sub-circuit 12 and responds to the backlight black insertion signal PWM to control the lighting and extinguishing of the light-emitting elements in the backlight source.

[0059] Exemplarily, the backlight black insertion signal PWM is a pulse width modulation (PWM) signal.

[0060] Exemplarily, the backlight driver circuit 1 includes two operating modes: a normally-on mode in which the light-emitting elements are constantly on, and a black-insertion mode in which backlight black insertion is performed. In the normally-on mode, the backlight black insertion signal PWM has a constant first level. In the normally-on mode, the black-insertion driver subcircuit 11 controls the light-emitting elements in the backlight source to illuminate continuously in response to the first-level backlight black insertion signal PWM. In the black-insertion mode, the backlight black insertion signal PWM is a PWM signal with a preset duty cycle. In the black-insertion mode, the black-insertion driver subcircuit 11 controls the light-emitting elements in the backlight source to illuminate in response to the first-level backlight black insertion signal PWM, and controls the light-emitting elements in the backlight source to turn off in response to the second-level backlight black insertion signal PWM.

[0061] The first level and the second level are determined according to actual characteristics of the transistor in the backlight driving circuit 1. When the transistor is an N-type transistor, the first level is a high level and the second level is a low level.

[0062] Exemplarily, when the backlight driving circuit 1 is in the black insertion mode, the duty cycle of the backlight black insertion signal PWM is 100%; when the backlight driving circuit 1 is in the black insertion mode, the duty cycle of the backlight black insertion signal PWM is 10%.

[0063] The reverse current cutoff sub-circuit 12 is configured to direct the reverse current flowing from the black insertion driving sub-circuit 11 into the first power supply voltage terminal GND′ when the backlight black insertion signal PWM switches from the normally-on mode to the black insertion mode.

[0064] For example, as shown in FIG3 , the first power supply voltage terminal GND′ is a ground terminal within the backlight driver circuit 1 and has no external pin. Furthermore, the backlight driver circuit 1 also includes an external ground terminal GND, specifically a ground pin on the backlight driver chip. Current returns to the ground through the external ground terminal GND to protect the backlight driver chip.

[0065] As shown in FIG3 , the first terminal (ie, PWM terminal) of the reverse current cutoff subcircuit 12 is electrically connected to the backlight black insertion signal source (not shown), the second terminal is electrically connected to the black insertion driving subcircuit 11 , and the third terminal is electrically connected to the first power supply voltage terminal GND′.

[0066] As shown in Figure 3, when the backlight driver circuit 1 rapidly switches from the normally-on mode to the black insertion mode, the backlight black insertion signal PWM suddenly changes from a continuous first level (e.g., a high level) to a second level (e.g., a low level), causing the parasitic capacitance between the second electrode and the control electrode of the transistor in the black insertion driver sub-circuit 11 to discharge instantaneously, generating a reverse current that flows in the reverse direction into the reverse current blocking sub-circuit 12. At this point, the reverse current blocking sub-circuit 12 directs the incoming reverse current, thereby preventing the backlight black insertion signal PWM provided by the backlight black insertion signal source from being burned. Furthermore, in the black insertion mode, when the backlight black insertion signal PWM is instantaneously boosted to a high level, the charge state of the parasitic capacitance is destroyed, causing the parasitic capacitance to discharge. At this point, the reverse current blocking sub-circuit 12 directs the discharged current from the parasitic capacitance into the first power supply voltage terminal GND', thereby preventing the parasitic capacitance discharge from obstructing the backlight black insertion signal PWM. This ensures stable light emission from the light-emitting elements in the backlight source, eliminating the phenomenon of insufficient brightness.

[0067] For example, as shown in FIG3 , the backlight driving circuit 1 further includes a voltage stabilizing subcircuit 13 and a voltage output subcircuit 14. The voltage stabilizing subcircuit 13 is connected to the external input voltage terminal V via the pin Vin. IN The voltage stabilization subcircuit 13 is, for example, a low-dropout linear regulator, configured to ensure a stable output voltage from the backlight driver circuit 1 and prevent drastic changes in the output voltage when the load is overloaded or short-circuited. The voltage output subcircuit 14 is electrically connected to the voltage stabilization subcircuit 13 and configured to output a power supply voltage Vout for driving the light-emitting elements.

[0068] In some embodiments, FIG4 is a schematic diagram of a black insertion drive subcircuit provided in an embodiment of the present disclosure. As shown in FIG4 , the black insertion drive subcircuit 11 includes n switch units 111 , where n is a positive integer greater than or equal to 1; the backlight source 2 (not shown in the figure, but see FIG9 or FIG10 below for details) includes multiple groups of light-emitting element groups 21 (not shown in the figure, but see FIG9 or FIG10 below for details), each light-emitting element group 21 includes multiple light-emitting elements, such as light-emitting diodes (LEDs); one switch unit 111 electrically connects one group of light-emitting element groups, and different switch units 111 electrically connect different groups of light-emitting element groups 21.

[0069] Here, the first end CN_1~CN_n of each switch unit 111 independently controls the light-emitting elements LED in a group of light-emitting elements group 21. Compared with one switch unit 111 controlling all light-emitting elements to emit light, multiple switch units 111 jointly control the light-emitting elements LED to emit light, which can reduce the driving current for driving the entire light-emitting elements LED to emit light.

[0070] In some embodiments, as shown in Figure 9 or Figure 10 below, multiple light-emitting elements LED in each light-emitting element group 21 are connected in series; the first end CN_1~CN_4 of the switch unit 111 is electrically connected to the second electrode of a light-emitting element LED in a group of light-emitting element groups, the second end of the switch unit 111 is electrically connected to the first power supply voltage end GND', and the third end 1111 of the switch unit 111 is electrically connected to the reverse current cutoff sub-circuit 12.

[0071] Exemplarily, the second electrode of the light emitting element LED may be a cathode of the light emitting element LED, and the first power supply voltage terminal GND′ may be a ground terminal.

[0072] In some embodiments, FIG5 is a specific circuit structure diagram of the black insertion drive sub-circuit provided in an embodiment of the present disclosure. As shown in FIG5 , the switch unit 111 includes a transistor MOS and a load resistor R 负 The first electrode s of the transistor MOS is electrically connected to the load resistor R 负 The first end of the second electrode d is electrically connected to the second electrode of a light-emitting element LED in a group of light-emitting elements 21 (not shown in the figure, please refer to Figure 9 or Figure 10 below for details), and the control electrode g is electrically connected to the reverse current cutoff sub-circuit 12; the load resistor R 负 The second end is electrically connected to the first power supply voltage end GND'.

[0073] It should be noted that the transistor MOS used in the embodiment of the present disclosure can be a thin film transistor MOS or a field effect transistor or other devices with the same characteristics. Since the source and drain of the transistor MOS used are symmetrical, there is no difference between its source and drain. In the embodiment of the present disclosure and the subsequent description, in order to distinguish the source and drain of the transistor MOS, one of the poles is called the first pole, the other pole is called the second pole, and the gate is called the control pole. In addition, according to the characteristics of the transistor MOS, the transistor MOS can be divided into N-type and P-type. When a P-type transistor MOS is used, the first pole is the source of the P-type transistor MOS, and the second pole is the drain of the P-type transistor MOS. When a low-level signal is input to the control pole, the source and drain are turned on; when an N-type transistor MOS is used, the first pole is the source of the N-type transistor MOS, and the second pole is the drain of the N-type transistor MOS. When a high-level signal is input to the control pole, the source and drain are turned on.

[0074] In the following embodiments, the field effect transistor is an N-type MOS transistor. In this case, the first level is a high level and the second level is a low level.

[0075] Exemplarily, the control electrode of the transistor MOS responds to the backlight black insertion signal PWM flowing through the reverse current cutoff sub-circuit 12, and is turned on when the level of the backlight black insertion signal PWM is a first level, and controls the light-emitting elements in a group of light-emitting element groups electrically connected to it to emit light; and is turned off when the level of the backlight black insertion signal PWM is a second level, and controls the light-emitting elements in the group of light-emitting element groups electrically connected to it to extinguish, thereby realizing backlight black insertion.

[0076] In some embodiments, Figure 6a is a specific architecture diagram of an exemplary backlight driving circuit provided by an embodiment of the present disclosure. As shown in Figure 6a, the reverse current cutoff sub-circuit 12 includes a first resistor R and a second resistor r; the resistance of the first resistor R is greater than the resistance of the second resistor r; the first end of the first resistor R is electrically connected to the external backlight black insertion signal source 3 (not shown in the figure, please refer to Figure 9 or Figure 10 below for details), and the second end is electrically connected to the control electrode of each transistor MOS; the first end of the second resistor r is electrically connected to the control electrode of each transistor MOS, and the second end is electrically connected to the first power supply voltage terminal GND'.

[0077] The resistance of the first resistor R is set based on the reverse current of the black insertion drive sub-circuit 11 and the premise of not affecting the turn-on voltage of the backlight black insertion signal PWM on the transistor MOS. The resistance of the second resistor r is much smaller than that of the first resistor R.

[0078] FIG6b is a schematic diagram of an exemplary reverse current equivalent circuit provided by an embodiment of the present disclosure. As shown in FIG6b , when the reverse current I 反 During backflow, the first resistor R and the second resistor r can play a shunt role, thereby reducing the reverse current I with a larger current value. 反 and transfers most of the reverse current I 反 The first power supply voltage terminal GND′ is introduced to avoid burning the backlight black insertion signal PWM provided by the backlight black insertion signal source 3 .

[0079] Exemplarily, the relationship between the resistance of the first resistor R, the resistance of the second resistor r, the reverse current of the black insertion driving sub-circuit 11 and the turn-on voltage of the transistor MOS satisfies the following formula 1: 开 =R×r×I 反 / (R+r)............................Formula 1

[0080] Among them, U 开 represents the turn-on voltage of the MOS transistor; R represents the resistance of the first resistor; r represents the resistance of the second resistor; I 反 represents the reverse current of the black insertion driving sub-circuit 11.

[0081] When I 反 and U开 =When the value is fixed, the resistance value of the first resistor R and the resistance value of the second resistor R are set.

[0082] Exemplarily, the resistance value of the first resistor R is set between 50Ω and 70Ω; and the resistance value of the second resistor r is set below 10Ω.

[0083] It should be noted that the smaller the resistance of the second resistor r is, the greater the reverse current I 反 The greater the amount of reverse current I introduced into the first power supply voltage terminal GND', the more fully the reverse current I is released. However, if the resistance of the second resistor r is zero, that is, the second end of the first resistor R is directly connected to the first power supply voltage terminal GND', the voltage at the control electrode of the transistor MOS will be zero, thereby affecting the on and off of the transistor MOS. Therefore, in this embodiment, the resistance of the second resistor r is as small as possible while satisfying the above formula 1, but not zero.

[0084] It should be noted that the reverse current blocking sub-circuit 12 in the above embodiment includes a first resistor R and a second resistor r, and the first resistor R and the second resistor r can block most of the reverse current I 反 The first power supply voltage terminal GND' is introduced. However, there will still be some reverse current I 反 Backflow to the backlight black signal source, although this part of the reverse current I 反 The backlight black insertion signal PWM will not be burned, but the transmission quality of the backlight black insertion signal PWM will be affected. Based on this, the embodiment of the present disclosure also provides another backlight driving circuit 1, as shown in FIG7a.

[0085] In some embodiments, Figure 7a is a specific architecture diagram of an exemplary backlight driving circuit provided in an embodiment of the present disclosure. As shown in Figure 7a, the reverse current cutoff sub-circuit 12 also includes a cutoff capacitor C; the first plate of the cutoff capacitor C is electrically connected to the backlight black insertion signal source 3 (not shown in the figure, please refer to Figure 9 or Figure 10 below for details), and the second plate is electrically connected to the first power supply voltage terminal GND'.

[0086] The resistance of the first resistor R is set based on the premise that it does not affect the turn-on voltage of the backlight black insertion signal PWM on the transistor MOS and is based on the reverse current of the black insertion drive sub-circuit 11. The resistance of the second resistor r is much smaller than the resistance of the first resistor R. The capacitance of the cut-off capacitor C is based on the actual circuit requirements and the reverse current I to be absorbed. 反 to set it up.

[0087] For example, according to the actual circuit requirements, in order to allow the cut-off capacitor C to reduce the reverse current I 反 Filter out, the minimum value of the cut-off capacitor C 最小值 =I C×t / U C , where I C Represents the current of the cut-off capacitor C, U C Represents the voltage of the cut-off capacitor C; specifically, I C =r×I 反 / (R+r),U C =R×I 反 ×r / (R+r).

[0088] FIG7b is a schematic diagram of an exemplary reverse current equivalent circuit provided by an embodiment of the present disclosure. As shown in FIG7b, when the reverse current I flows back, the first resistor R and the second resistor r can play a shunt role, thereby reducing the reverse current I with a larger current value. 反 and transfers most of the reverse current I 反 The first power supply voltage terminal GND' is introduced to avoid burning the backlight black insertion signal PWM provided by the backlight black insertion signal source. At the same time, another small part of the reverse current I 反 It is absorbed by the cut-off capacitor C, thereby ensuring the PWM stability of the backlight black insertion signal.

[0089] For example, the resistance value of the first resistor R, the resistance value of the second resistor r, the reverse current I of the black insertion drive sub-circuit 11 反 The relationship between the turn-on voltage of the MOS transistor satisfies the following formula: 开 =U C +U R =2R×r×I 反 / (R+r)................Formula 2

[0090] Among them, U 开 Indicates the turn-on voltage of the MOS transistor; U C Represents the voltage of the cut-off capacitor C; U R represents the voltage of the first resistor R; R represents the resistance of the first resistor; r represents the resistance of the second resistor; I 反 represents the reverse current of the black insertion driving sub-circuit 11.

[0091] When I 反 and U 开 =When the value is fixed, the resistance value of the first resistor R and the resistance value of the second resistor R are set.

[0092] At the same time, the presence of the first resistor R can also reduce the damping oscillation generated by the parasitic inductance ESL and the parasitic resistance ESR of the cut-off capacitor C, further ensuring the stability of the backlight black insertion signal PWM.

[0093] It should be noted that the oscillation principle generated by the cut-off capacitor C is as follows: Figure 8a is the circuit diagram of an ideal cut-off capacitor, and Figure 8b is the circuit diagram of an actual cut-off capacitor. As shown in Figures 8a and 8b, due to actual process limitations, the cut-off capacitor C cannot be manufactured in an ideal state, and parasitic inductance ESL and parasitic resistance ESR will exist. The series connection of the parasitic inductance ESL and the cut-off capacitor C will cause energy exchange, which in turn will produce damped oscillations, affecting the backlight black insertion signal PWM. Generally, the main way to reduce damped oscillations is to increase the damping resistor (the damping resistor is the total resistance in series with the cut-off capacitor C. For a circuit with only the cut-off capacitor C, the damping resistor is the parasitic resistance ESR).

[0094] In this embodiment, the first resistor R and the parasitic resistor ESR are connected in series. Therefore, the existence of the first resistor R is equivalent to adding a damping resistor, thereby preventing spike noise from being generated in the waveform of the backlight black insertion signal PWM due to damped oscillation, thereby affecting the stability of the backlight black insertion signal PWM.

[0095] It should be noted that if the first resistor R and the second resistor r are not provided, only the cut-off capacitor C is provided to absorb the reverse current I of the black insertion drive sub-circuit 11. 反 , then the cut-off capacitor C needs to be set to a larger capacitance value to play a role, but if the capacitance value of the cut-off capacitor C is too large, the resonant frequency will be reduced, causing the operating frequency of the backlight to be higher than the resonant frequency ( Wherein, ω0 represents the resonant frequency, C represents the capacitance value of the cut-off capacitor C, and ESL represents the parasitic inductance), thus presenting an inductive characteristic, which makes the cut-off capacitor C unable to pass the AC signal, reducing the filtering effect. Therefore, the capacitance value of the cut-off capacitor C disclosed in the present invention cannot be too large.

[0096] In some embodiments, the relationship between the minimum capacitance of the cut-off capacitor C and the resistance of the first resistor R satisfies the following formula 3: C=t / R.....................................Formula 3

[0097] Wherein, C represents the minimum capacitance value of the cut-off capacitor, t represents unit time, and R represents the resistance value of the first resistor R. When the resistance value of the first resistor R is fixed, the minimum capacitance value of the cut-off capacitor C is set.

[0098] In addition, an embodiment of the present disclosure further provides a display device. FIG9 is a schematic diagram of the display device provided by an embodiment of the present disclosure. As shown in FIG9 , the display device includes a backlight source 2, a display panel (not shown), and a backlight driving circuit 1. The backlight driving circuit 1 can be considered as the backlight driving circuit 1 of each of the above-mentioned embodiments and their combinations.

[0099] In some embodiments, the display panel of the present disclosure is a liquid crystal display panel.

[0100] In some embodiments, the backlight source 2 of the present disclosure is an edge-type backlight source. Specifically, the backlight source 2 is located on a side of the liquid crystal display panel that is perpendicular to the light emitting direction.

[0101] In some embodiments, as shown in FIG. 9 , the display device further includes a backlight control circuit 20 configured to provide a backlight black insertion signal PWM to the reverse current cutoff sub-circuit 12 .

[0102] Exemplarily, the backlight control circuit 20 is, for example, a backlight integrated circuit (IC) or a microcontroller unit (MCU). The backlight black insertion signal source 3 (i.e., the backlight black insertion signal PWM pin) in the backlight control circuit 20 is electrically connected to the first end of the first resistor R (and the first end of the cutoff capacitor C) in the reverse current cutoff sub-circuit 12, for providing the backlight black insertion signal PWM to the reverse current cutoff sub-circuit 12.

[0103] In some embodiments, the backlight control circuit 20 includes a backlight black insertion signal source 3; the backlight driving circuit 1 includes multiple; each reverse current cutoff sub-circuit 12 in the multiple backlight driving circuits 1 is electrically connected to the same backlight black insertion signal source 3, which is conducive to realizing a small-sized display device.

[0104] The display device is a virtual reality (VR) device or an augmented reality (AR) device. Unlike large-size liquid crystal displays (LCDs), which can have multiple backlight blackout signal sources 3, VR / AR products have a limited number of backlight chip IC pins due to screen size limitations.

[0105] It should be noted that the direct-lit backlight product shown in Figure 1 has more light-emitting elements than edge-lit backlights, requiring a higher drive current. Furthermore, it requires a larger number of backlight blackout signal sources. For example, as shown in Figure 1, the direct-lit backlight has 2304 light-emitting elements, divided into 72 groups. Each group is electrically connected to a switch circuit 011, and each switch circuit 011 is electrically connected to eight backlight blackout signal sources. Each group includes 32 LEDs, divided into eight groups, with four LEDs in each group connected in series. In blackout mode, a single channel (CH) can be controlled by eight backlight blackout signal sources. To achieve the same backlight brightness as edge-lit backlight products, the required drive current is lower. Furthermore, the direct-lit backlight product has 72 × 8 = 576 backlight blackout signal sources (i.e., one backlight blackout signal source is provided for each LED segment (four light-emitting elements connected in series), for a total of 2304 / 4 = 576 segments). Therefore, direct-lit backlight products are less likely to suffer from the backlight black insertion signal PWM burn-in problem than edge-lit backlight products.

[0106] In some embodiments, the backlight source 2 includes N groups of light emitting element groups 21 , each group of light emitting element groups 21 includes M light emitting elements LEDs, wherein N is in the range of 1 to 4, and M is in the range of 1 to 4. Optionally, M=4.

[0107] For example, FIG10 is a schematic diagram of a backlight driving circuit driving a backlight source provided by an embodiment of the present disclosure. As shown in FIG10 , the side-entry backlight source has a total of 12 light-emitting element LEDs, which are divided into 4 groups of light-emitting element groups 21. Each group of light-emitting element groups 21 includes 3 light-emitting element LEDs connected in series. In order to achieve the same backlight brightness as a direct-type backlight product, a larger driving current is required. At the same time, due to the size limitation of the small-sized display device and the influence of the small number of backlight control chip interfaces, the number of backlight black insertion signal sources 3 is small, and usually only one backlight black insertion signal source 3 is set (not shown in the figure). At this time, the reverse current flowing into the backlight black insertion signal source 3 is the sum of the reflux of each group of light-emitting element groups 21. In the case where the reverse current cutoff sub-circuit 12 is not set, the sum of the reflux of each group of light-emitting element groups 21 directly flows into the backlight black insertion signal source 3, which can easily cause the backlight black insertion signal PWM to burn out.

[0108] As shown in Figure 10, a reverse current blocking subcircuit 12 is provided between the backlight black insertion signal source 3 and the black insertion driver subcircuit 11. When the backlight driver circuit 1 rapidly switches from the normally-on mode to the black insertion mode, the reverse current flowing from the black insertion driver subcircuit 11 is directed to the first power supply voltage terminal GND' via the reverse current blocking subcircuit 12. This prevents the parasitic capacitance of the MOS transistor from instantly discharging back into the backlight black insertion signal source 3 and damaging the backlight black insertion signal PWM. In black insertion mode, the reverse current blocking subcircuit 12 directs the current discharged from the parasitic capacitance to the first power supply voltage terminal GND', thereby preventing the parasitic capacitance discharge from obstructing the backlight black insertion signal PWM. This ensures stable illumination of the light-emitting elements LEDs in the backlight source 2, eliminating the problem of insufficient brightness.

[0109] Exemplarily, the backlight driving circuit 1 includes two working modes, one is a normally-on mode for controlling the light-emitting element LED to be always on, and the other is a black insertion mode for performing backlight black insertion.

[0110] In the normally-on mode, the level of the backlight black insertion signal PWM is a constant first level (e.g., a high level); the control electrode of the transistor MOS in each switch unit 111 is turned on in response to the first level of the backlight black insertion signal PWM, and the driving current is then supplied from the second power supply voltage terminal V OUT The power starts to flow through the light emitting element LED and the switch unit 111 and finally flows into the first power supply voltage terminal GND′, and the light emitting element LED emits light.

[0111] In the black insertion mode, the control electrode of the transistor MOS in each switch unit 111 is turned on in response to the first level backlight black insertion signal PWM, and the driving current is supplied from the second power supply voltage terminal V OUT The current begins to flow through the light-emitting element LED and the switch unit 111, and finally flows into the first power supply voltage terminal GND', causing the light-emitting element LED to emit light. Furthermore, the control electrode of the transistor MOS in each switch unit 111 is cut off in response to the backlight black insertion signal PWM of the second level. At this time, the driving current cannot flow through the switch unit 111, and the light-emitting element LED is turned off.

[0112] Exemplarily, the display device may be any product with a display function, such as a VR device, an AR device, a mobile phone, a tablet computer, a television, a monitor, a laptop computer, a digital photo frame, or a vehicle-mounted device.

[0113] The above is a complete description of the display device. Other essential components of the display device are well understood by those skilled in the art and will not be described in detail here, nor should they be considered as limitations of the present disclosure.

[0114] It is understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present disclosure, and the present disclosure is not limited thereto. Those skilled in the art may make various modifications and improvements without departing from the spirit and substance of the present disclosure, and such modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A backlight driving circuit, which is electrically connected to a backlight source; wherein: The backlight driving circuit at least comprises a black insertion driving subcircuit and a reverse current cutoff subcircuit; the black insertion driving subcircuit and the reverse current cutoff subcircuit are electrically connected; The black insertion driving subcircuit is configured to control the lighting and extinguishing of the light-emitting element in the backlight source in response to the backlight black insertion signal flowing through the reverse current cutoff subcircuit; The reverse current cutoff subcircuit is configured to introduce the reverse current flowing in reverse from the black insertion driving subcircuit into the first power supply voltage terminal when the backlight black insertion signal is switched from the normally-on mode to the black insertion mode.

2. The backlight driving circuit according to claim 1, wherein: The black insertion drive subcircuit includes n switch units; n is a positive integer greater than or equal to 1; the backlight source includes a plurality of light emitting element groups, each of which includes a plurality of light emitting elements; One of the switch units is electrically connected to one group of the light emitting element groups, and different switch units are electrically connected to different groups of the light emitting element groups.

3. The backlight driving circuit according to claim 2, wherein: A plurality of light emitting elements in each group of light emitting elements are connected in series; The first end of the switch unit is electrically connected to the second electrode of one of the light-emitting elements in the light-emitting element group, the second end of the switch element is electrically connected to the first power supply voltage end, and the second end of the switch element is electrically connected to the reverse current cutoff sub-circuit.

4. The backlight driving circuit according to claim 3, wherein: The switch unit includes a transistor and a load resistor; The first electrode of the transistor is electrically connected to the first end of the load resistor, the second electrode is electrically connected to the second electrode of one of the light emitting elements in the light emitting element group, and the control electrode is electrically connected to the reverse current cutoff subcircuit; The second end of the load resistor is electrically connected to the first power supply voltage end.

5. The backlight driving circuit according to claim 4, wherein: The reverse current cutoff subcircuit comprises a first resistor and a second resistor; the resistance value of the first resistor is greater than the resistance value of the second resistor; The first end of the first resistor is electrically connected to an external backlight black insertion signal source, and the second end is electrically connected to the control electrode of each of the transistors; A first end of the second resistor is electrically connected to a control electrode of each of the transistors, and a second end of the second resistor is electrically connected to the first power supply voltage end.

6. The backlight driving circuit according to claim 5, wherein: The reverse current cutoff subcircuit also includes a cutoff capacitor; The first plate of the cut-off capacitor is electrically connected to the backlight black insertion signal source, and the second plate is electrically connected to the first power supply voltage terminal.

7. The backlight driving circuit according to claim 6, wherein: The relationship between the resistance value of the first resistor, the resistance value of the second resistor, the reverse current of the black insertion driving subcircuit and the turn-on voltage of the transistor satisfies the following formula: U 开 =2R×r×I 反 / (R+r), where R represents the resistance value of the first resistor, and r represents the resistance value of the second resistor; U 开 represents the turn-on voltage of the transistor, I 反 Represents the reverse current of the black insertion driving sub-circuit.

8. The backlight driving circuit according to claim 6, wherein: The relationship between the minimum capacitance value of the cut-off capacitor and the resistance value of the first resistor satisfies the following formula: C=t / R, wherein C represents the minimum capacitance value of the cut-off capacitor, t represents unit time, and R represents the resistance value of the first resistor.

9. A display device comprising a backlight source, a display panel, and at least one backlight driving circuit according to any one of claims 1 to 8.

10. The display device according to claim 9, wherein: The display device further includes a backlight control circuit configured to provide the backlight black insertion signal to the reverse current cutoff sub-circuit.

11. The display device according to claim 10, wherein: The backlight control circuit includes a backlight black insertion signal source; the backlight driving circuit includes a plurality of; Each of the reverse current cutoff sub-circuit in the plurality of backlight driving circuits is electrically connected to the same backlight black insertion signal source.

12. The display device according to claim 9, wherein: The display panel is a liquid crystal display panel.

13. The display device according to claim 12, wherein: The backlight source is located on one side of the liquid crystal display panel that is perpendicular to the light emitting direction.

14. The display device according to claim 13, wherein: The backlight source includes N groups of light emitting element groups, each of which includes M light emitting elements; wherein the value range of N is between 1 and 4, and the value range of M is between 1 and 4.

15. The display device according to any one of claims 9 to 14, wherein: The display device is a virtual reality device or an augmented reality device.

Images