Backlight driving circuit and display device

Abstract

The invention provides a backlight driving circuit and a display device, and belongs to the technical field of virtual reality and augmented reality. The backlight driving circuit is electrically connected with 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 with the reverse current cut-off sub-circuit; the black frame insertion driving sub-circuit is configured to respond to the backlight black frame insertion signal flowing through the reverse current cut-off sub-circuit and control light emitting and extinguishing of a light emitting element in the backlight source; and the reverse current cut-off sub-circuit is configured to introduce the reverse current reversely flowing from the black insertion driving sub-circuit into the first power supply voltage end when the backlight black insertion signal is converted from the normally open mode to the black insertion mode.

Description

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, the picture display delay is a key performance parameter for measuring display products. The higher the picture display delay, the more obvious the smearing phenomenon caused by the delay. In order to obtain a lower picture display delay and solve the smearing problem caused by the response time, backlight blanking can be performed.

[0003] With the widespread application of backlight blanking technology in a large number of display products, the problems it causes have been gradually discovered. Especially in small-size, side-entry backlight products, there is a problem that the backlight blanking 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 problems of the present disclosure is a backlight driving circuit electrically connected to a backlight source; wherein, the backlight driving circuit at least includes a blanking driving sub-circuit and a reverse current cut-off sub-circuit; the blanking driving sub-circuit and the reverse current cut-off sub-circuit are electrically connected;

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

[0007] The reverse current cut-off sub-circuit is configured to introduce a reverse current flowing back from the blanking driving sub-circuit into a first power supply voltage terminal when the backlight blanking signal is switched from a normally open mode to a blanking mode.

[0008] In some embodiments, the blanking driving sub-circuit includes n switching units; n is a positive integer greater than or equal to 1; the backlight source includes multiple groups of light-emitting element groups, and each group of light-emitting element groups includes multiple light-emitting elements;

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

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

[0011] The first end of the switching unit is electrically connected to the second electrode of one of the light-emitting elements in a group of the light-emitting element groups, the second end of the switching element is electrically connected to the first power voltage terminal, and the second end of the switching element is electrically connected to the reverse current cut-off sub-circuit.

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

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

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

[0015] In some embodiments, the reverse current cut-off sub-circuit includes a first resistor and a second resistor; the resistance value of the first resistor is greater than that of the second resistor;

[0016] The first end of the first resistor is electrically connected to an external backlight blanking signal source, and the second end is electrically connected to the control poles of the transistors;

[0017] The first end of the second resistor is electrically connected to the control poles of the transistors, and the second end is electrically connected to the first power voltage terminal.

[0018] In some embodiments, the reverse current cut-off sub-circuit further includes a cut-off capacitor;

[0019] The first plate of the cut-off capacitor is electrically connected to the backlight blanking signal source, and the second plate is electrically connected to the first power 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 blanking drive 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 value of the first resistor, r represents the resistance value of the second resistor; U 开 represents the turn-on voltage of the transistor, and I 反 represents the reverse current of the blanking drive sub-circuit.

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

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

[0024] In a second aspect, embodiments of the present disclosure further provide a display device, including a backlight source, a display panel, and at least one backlight driving circuit as described in any one of the first aspect.

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

[0026] In some embodiments, the backlight control circuit includes a backlight blanking signal source; and the backlight driving circuit includes multiple ones.

[0027] Each of the reverse current cut-off sub-circuits in the multiple backlight driving circuits is electrically connected to the same backlight blanking 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 one side of the liquid crystal display panel perpendicular to the light-emitting direction.

[0030] In some embodiments, the backlight source includes N groups of light-emitting element groups, and each group of light-emitting element groups 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] Figure 1 is a partial circuit architecture diagram of a backlight control module of a related direct-lit backlight source;

[0033] Figure 2 is a partial architecture diagram of a related side-injected backlight driving circuit;

[0034] Figure 3 is an architecture diagram of an exemplary backlight driving circuit provided by embodiments of the present disclosure;

[0035] Figure 4 is a schematic diagram of a blanking driving sub-circuit provided by embodiments of the present disclosure;

[0036] Figure 5 is a specific circuit structure diagram of the blanking driving sub-circuit provided by embodiments of the present disclosure;

[0037] Figure 6a is a specific architecture diagram of an exemplary backlight driving circuit provided by embodiments of the present disclosure;

[0038] Figure 6bSchematic diagram of an exemplary reverse current equivalent circuit provided by an embodiment of the present disclosure;

[0039] Figure 7a Specific architecture diagram of an exemplary backlight driving circuit provided by an embodiment of the present disclosure;

[0040] Figure 7b Schematic diagram of an exemplary reverse current equivalent circuit provided by an embodiment of the present disclosure;

[0041] Figure 8a Circuit diagram of an ideal cut-off capacitor;

[0042] Figure 8b Circuit diagram of an actual cut-off capacitor;

[0043] Figure 9 Schematic diagram of a display device provided by an embodiment of the present disclosure;

[0044] Figure 10 Schematic diagram of a backlight driving circuit driving a backlight source provided by an embodiment of the present disclosure. Detailed implementation manners

[0045] To make the objectives, 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 with reference to the accompanying drawings in the embodiments of the present disclosure. Apparently, the described embodiments are only some of the embodiments of the present disclosure, rather than all the embodiments. Usually, the components of the embodiments of the present disclosure described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present disclosure provided in the accompanying drawings is not intended to limit the scope of the present disclosure to be protected, but merely represents the selected embodiments of the present disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of the present disclosure without creative efforts shall fall within the scope of protection of the present disclosure.

[0046] Unless otherwise defined, the technical terms or scientific terms used in this disclosure shall have the ordinary meanings understood by those of ordinary skill in the art to which this disclosure pertains. The terms "first", "second" and similar words used in this disclosure do not denote any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "a", "an" or "the" do not denote a quantity limitation, but mean that there is at least one. Words such as "comprising" or "including" mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. Words such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right", etc. are only used to indicate relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0047] As used in this disclosure, "a plurality or several" means two or more. "And / or" describes the relationship between related objects and indicates that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " generally indicates that the related objects before and after are in an "or" relationship.

[0048] In the related art, as Figure 1 shown, it is a partial circuit architecture diagram of the backlight control module of a related direct-lit backlight. The light-emitting elements of the direct-lit backlight are more than those of the edge-lit backlight. On the premise that the backlight brightness remains unchanged, the direct-lit backlight requires less drive current than the edge-lit backlight. In addition, the direct-lit backlight control circuit has more backlight dimming signal sources, and a backlight dimming signal source is set in each LED zone. Therefore, for direct-lit backlight products, it is not easy to cause the problem of burning out the backlight dimming signal.

[0049] It should be noted that on the premise that the backlight brightness is the same, the greater the drive current required by the backlight, the fewer the number of backlight dimming signal sources, and the easier it is to cause the problem of burning out the backlight dimming signal.

[0050] In the related art, as Figure 2 shown, it is a partial architecture diagram of a related edge-lit backlight driving circuit. The backlight driving circuit 01 receives the backlight dimming signal PWM from the backlight dimming signal source, thereby controlling the lighting and extinguishing of the light-emitting elements in the backlight. Among them, the backlight driving circuit 01 includes two working modes, one is a normally open mode for controlling the light-emitting elements to be always on, and the other is a dimming mode for performing backlight dimming.

[0051] Exemplarily, as Figure 2As shown, the backlight driving circuit 01 quickly switches from the normally-on mode to the blanking mode. At this time, the backlight blanking signal PWM suddenly changes from a continuous first level (for example, high level) to a second level (for example, low level), which causes the parasitic capacitance between the second pole and the control pole of the transistor MOS in the backlight driving circuit 01 to instantaneously discharge and flow reversely into the backlight blanking signal PWM (that is, the backlight blanking signal source). In small-size, side-entry backlight products, a relatively high driving current is required for the backlight source. Therefore, the reverse current flowing back due to the instantaneous discharge of the parasitic capacitance is relatively large, directly causing the backlight blanking signal PWM to burn out.

[0052] At the same time, in the blanking mode, as the high and low levels of the backlight blanking signal PWM continuously change, there is also a risk of insufficient charging of the parasitic capacitance of the transistor MOS. This is mainly because when the backlight blanking signal PWM is at the low level (the second level), the parasitic capacitance between the second pole and the control pole of the transistor MOS is in the charging state (Vds = V OUT ). When the backlight blanking signal PWM instantaneously rises to the high level (the first level), it will destroy the charge state of the parasitic capacitance, cause the parasitic capacitance to discharge, hinder the rise of the backlight blanking signal PWM, thereby prolonging the turn-on time of the transistor MOS in the backlight driving circuit 01, reducing the actual light-emitting time of the light-emitting elements in the backlight source, and ultimately resulting in insufficient brightness of the backlight source.

[0053] In view of this, the embodiments of the present disclosure provide a backlight driving circuit, which essentially eliminates one or more of the problems caused by the limitations and defects of the related art. Specifically, in the embodiments of the present disclosure, by adding a reverse current cut-off sub-circuit, when the backlight blanking signal switches from the normally-on mode to the blanking mode, the reverse current cut-off sub-circuit introduces the reverse current flowing reversely from the blanking driving sub-circuit into the first power supply voltage terminal, thereby avoiding the situation where the parasitic capacitance of the transistor instantaneously discharges and flows back to the backlight blanking signal source and burning out the backlight blanking signal.

[0054] The structure of the backlight driving circuit provided by the embodiments of the present disclosure will be described in detail below.

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

[0056] As Figure 3 shown, the backlight driving circuit 1 at least includes a blanking driving sub-circuit 11 and a reverse current cut-off sub-circuit 12; among them, the blanking driving sub-circuit 11 and the reverse current cut-off 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 cut - off 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, in response to the backlight black insertion signal PWM, controls 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 driving circuit 1 includes two operating modes. One is the normally - on mode for controlling the light - emitting elements to be always on, and the other is the black insertion mode for performing backlight black insertion. In the normally - on mode, the level of the backlight black insertion signal PWM is a constant first level; in the normally - on mode, the black insertion driving sub - circuit 11 controls the lighting of the light - emitting elements in the backlight source in response to the backlight black insertion signal PWM at the first level and remains in the lighting state continuously. 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 driving sub - circuit 11 controls the lighting of the light - emitting elements in the backlight source in response to the backlight black insertion signal PWM at the first level; and controls the turning - off of the light - emitting elements in the backlight source in response to the backlight black insertion signal PWM at the second level.

[0061] Among them, the first level and the second level are determined according to the actual characteristics of the transistors 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, in the black insertion mode of the backlight driving circuit 1, the duty cycle of the backlight black insertion signal PWM is 100%; in the black insertion mode of the backlight driving circuit 1, the duty cycle of the backlight black insertion signal PWM is 10%.

[0063] The reverse - current cut - off sub - circuit 12 is configured to introduce the reverse current flowing back from the black insertion driving sub - circuit 11 into the first power - supply voltage terminal GND' when the backlight black insertion signal PWM is switched from the normally - on mode to the black insertion mode.

[0064] Exemplarily, as Figure 3 shown, the first power - supply voltage terminal GND' is the internal ground terminal of the backlight driving circuit 1 and has no external pin. In addition, the backlight driving circuit 1 further includes an external ground terminal GND, specifically the ground pin on the backlight driving chip, and the current returns to the ground through the external ground terminal GND to protect the backlight driving chip.

[0065] AsFigure 3 As shown, the first terminal (i.e., the PWM terminal) of the reverse current cut-off sub-circuit 12 is electrically connected to a backlight insertion black signal source (not shown in the figure), the second terminal is electrically connected to the insertion black driving sub-circuit 11, and the third terminal is electrically connected to the first power voltage terminal GND'.

[0066] As Figure 3 shown, when the backlight driving circuit 1 quickly switches from the normally open mode to the insertion black mode, at this time, the backlight insertion black signal PWM suddenly changes from a continuous first level (for example, high level) to a second level (for example, low level), thereby causing the parasitic capacitance between the second pole and the control pole of the transistor in the insertion black driving sub-circuit 11 to instantaneously discharge to generate a reverse current, and the reverse current flows back into the reverse current cut-off sub-circuit 12. At this time, the reverse current cut-off sub-circuit 12 introduces the incoming reverse current, thereby avoiding burning out the backlight insertion black signal PWM provided by the backlight insertion black signal source. At the same time, in the insertion black mode, when the backlight insertion black signal PWM instantaneously rises to a high level, it will destroy the charge state of the parasitic capacitance, resulting in the discharge of the parasitic capacitance. At this time, the reverse current cut-off sub-circuit 12 introduces the current of the parasitic capacitance discharge into the first power voltage terminal GND', thereby avoiding the obstruction of the parasitic capacitance discharge to the backlight insertion black signal PWM, enabling the light-emitting elements in the backlight source to emit light stably, and eliminating the phenomenon of insufficient brightness.

[0067] Exemplarily, as Figure 3 shown, the backlight driving circuit 1 further includes a voltage stabilizing sub-circuit 13 and a voltage output sub-circuit 14. The voltage stabilizing sub-circuit 13 is electrically connected to the external input voltage terminal VIN through the pin Vin. The voltage stabilizing sub-circuit 13 is, for example, a low-dropout linear regulator, which is configured to ensure the stability of the output voltage of the backlight driving circuit 1 and avoid the problem of drastic changes in the output voltage when the load is overloaded or short-circuited. The voltage output sub-circuit 14 is electrically connected to the voltage stabilizing sub-circuit 13 and is configured to output the power supply voltage Vout for driving the light-emitting elements.

[0068] In some embodiments, Figure 4 is a schematic diagram of the insertion black driving sub-circuit provided by the embodiment of the present disclosure. As Figure 4 shown, the insertion black driving sub-circuit 11 includes n switch units 111. Wherein, n is a positive integer greater than or equal to 1; the backlight source 2 (not shown in the figure, specifically, reference can be made to the following Figure 9 or Figure 10 shown) includes multiple groups of light-emitting element groups 21 (not shown in the figure, specifically, reference can be made to the following Figure 9 or Figure 10 shown), each group of light-emitting element groups 21 includes multiple light-emitting elements, such as light-emitting diodes (LEDs); one switch unit 111 is electrically connected to one group of light-emitting element groups, and different switch units 111 are electrically connected to different groups of light-emitting element groups 21.

[0069] Here, the first ends CN_1 to CN_n of each switching unit 111 independently control the light-emitting elements LED in a group of light-emitting element groups 21 to emit light. Compared with a single switching unit 111 controlling all the light-emitting elements to emit light, multiple switching units 111 jointly controlling the light-emitting elements LED to emit light can reduce the driving current for driving all the light-emitting elements LED to emit light.

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

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

[0072] In some embodiments, Figure 5 This is the specific circuit structure diagram of the black insertion driving sub-circuit provided by the embodiments of the present disclosure. As Figure 5 shown, the switching unit 111 includes a transistor MOS and a load resistor R 负 ; the first pole s of the transistor MOS is electrically connected to the first end of the load resistor R 负 The second pole d is electrically connected to the second electrode of one light-emitting element LED in a group of light-emitting element groups 21 (not shown in the figure, specifically, reference may be made to the following Figure 9 or Figure 10 shown), the control pole g is electrically connected to the reverse current cut-off sub-circuit 12; the second end of the load resistor R 负 is electrically connected to the first power supply voltage terminal GND’.

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

[0074] In the following embodiments, a field-effect transistor is taken as an example of an N-type transistor MOS for description. At this time, the first level is a high level and the second level is a low level.

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

[0076] In some embodiments, Figure 6a is a specific architecture diagram of an exemplary backlight driving circuit provided by the embodiments of the present disclosure. As Figure 6a shown, the reverse current cut-off sub-circuit 12 includes a first resistor R and a second resistor r; the resistance value of the first resistor R is greater than the resistance value of the second resistor r; the first end of the first resistor R is electrically connected to an external backlight insertion black signal source 3 (not shown in the figure, and specific reference can be made to the following Figure 9 or Figure 10 shown), the second end is electrically connected to the control poles of each transistor MOS; the first end of the second resistor r is electrically connected to the control poles of each transistor MOS, and the second end is electrically connected to the first power voltage terminal GND'.

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

[0078] Figure 6b is a schematic diagram of an exemplary reverse current equivalent circuit provided by the embodiments of the present disclosure. AsFigure 6b As shown, when the reverse current I 反 flows back, the first resistor R and the second resistor r can play a role in shunting, thereby weakening the reverse current I with a larger current value 反 , and introducing the vast majority of the reverse current I 反 into the first power supply voltage terminal GND', thus avoiding burning out the backlight insertion black signal PWM provided by the backlight insertion black signal source 3.

[0079] Exemplarily, the relationship between the resistance value of the first resistor R, the resistance value of the second resistor r, the reverse current of the insertion black driving sub-circuit 11, and the turn-on voltage of the transistor MOS satisfies the following formula (1):

[0080] U 开 = R × r × I 反 / (R + r) ……………………… formula (1)

[0081] Wherein, U 开 represents the turn-on voltage of the transistor MOS; R represents the resistance value of the first resistor; r represents the resistance value of the second resistor; I 反 represents the reverse current of the insertion black driving sub-circuit 11.

[0082] When I 反 and U 开 are fixed in value, set the resistance value of the first resistor R and the resistance value of the second resistor R.

[0083] Exemplarily, set the resistance value of the first resistor R to be between 50 Ω and 70 Ω; set the resistance value of the second resistor r to be less than 10 Ω.

[0084] It should be noted that the smaller the resistance value of the second resistor r, the more the reverse current I 反 introduced into the first power supply voltage terminal GND' and the more fully the reverse current I is released. However, if the resistance value of the second resistor r is 0, that is, the second end of the first resistor R is directly connected to the first power supply voltage terminal GND', then the voltage at the control pole of the transistor MOS will be 0, thus affecting the on / off of the transistor MOS. Therefore, in this embodiment, the resistance value of the second resistor r is as small as possible but not 0 under the condition of satisfying the above formula (1).

[0085] It should be noted that the reverse current cut-off sub-circuit 12 in the above embodiment includes the first resistor R and the second resistor r, and through the first resistor R and the second resistor r, the vast majority of the reverse current I 反 can be introduced into the first power supply voltage terminal GND'. However, there will still be a part of the reverse current I 反 flowing back to the backlight insertion black signal source. Although this part of the reverse current I 反It will not burn out the backlight insertion black signal PWM, but it will also affect the transmission quality of the backlight insertion black signal PWM. Based on this, another backlight driving circuit 1 is further provided in the embodiments of the present disclosure. Refer to Figure 7a as shown.

[0086] In some embodiments, Figure 7a is a specific architecture diagram of an exemplary backlight driving circuit provided by the embodiments of the present disclosure. As Figure 7a shown, the reverse current cut-off sub-circuit 12 further includes a cut-off capacitor C; the first plate of the cut-off capacitor C is electrically connected to the backlight insertion black signal source 3 (not shown in the figure, and specifically can refer to the following Figure 9 or Figure 10 shown), and the second plate is electrically connected to the first power supply voltage terminal GND'.

[0087] Among them, the resistance value of the first resistor R is set based on the premise of not affecting the turn-on voltage of the backlight insertion black signal PWM on the transistor MOS and based on the reverse current of the insertion black driving sub-circuit 11. The resistance value of the second resistor r is much smaller than the resistance value of the first resistor R. The capacitance value of the cut-off capacitor C is set based on the actual circuit requirements and based on the reverse current I 反 to be absorbed.

[0088] Exemplarily, according to the actual circuit requirements, in order to allow the cut-off capacitor C to filter out the reverse current I 反 within time t, the minimum value C 最小值 of the cut-off capacitor C C = I C × t / U C , where I C represents the current of the cut-off capacitor C, and U C represents the voltage of the cut-off capacitor C; specifically, I 反 = r × I C / (R + r), U 反 = R × I

[0089] Figure 7b is a schematic diagram of an exemplary reverse current equivalent circuit provided by the embodiments of the present disclosure. As Figure 7b shown, when the reverse current I flows back, the first resistor R and the second resistor r can play a role in shunting, thereby weakening the reverse current I 反 with a relatively large current value, and introducing the vast majority of the reverse current I 反 into the first power supply voltage terminal GND', thereby avoiding burning out the backlight insertion black signal PWM provided by the backlight insertion black signal source. At the same time, another small part of the reverse current I 反 is absorbed by the cut-off capacitor C, thereby ensuring the stability of the backlight insertion black signal PWM.

[0090] Exemplarily, the relationship between the resistance value of the first resistor R, the resistance value of the second resistor r, and the reverse current I of the black insertion driving sub-circuit 11 反 and the turn-on voltage of the transistor MOS satisfies the following formula two:

[0091] U 开 = U C + U R = 2R × r × I 反 / (R + r) …………… formula two

[0092] Wherein, U 开 represents the turn-on voltage of the transistor MOS; 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 value of the first resistor; r represents the resistance value of the second resistor; I 反 represents the reverse current of the black insertion driving sub-circuit 11.

[0093] When I 反 and U 开 = take fixed values, set the resistance values of the first resistor R and the second resistor R.

[0094] Meanwhile, the existence of the first resistor R can also reduce the damped oscillation generated by the parasitic inductance ESL and parasitic resistance ESR of the cut-off capacitor C, and further ensure the stability of the backlight black insertion signal PWM.

[0095] It should be noted that the oscillation principle of the cut-off capacitor C is as follows: Figure 8a is the circuit diagram of an ideal cut-off capacitor, Figure 8b is the circuit diagram of an actual cut-off capacitor. As shown in Figure 8a and Figure 8b shown, due to actual process limitations, the cut-off capacitor C cannot reach the ideal state during production, and there will be parasitic inductance ESL and parasitic resistance ESR. The series connection of the parasitic inductance ESL and the cut-off capacitor C will cause energy exchange, and then generate damped oscillation, affecting the backlight black insertion signal PWM. Generally, the main way to reduce damped oscillation is to increase the damping resistance (the damping resistance is the total resistance in series with the cut-off capacitor C. For a circuit with only the cut-off capacitor C, the damping resistance is the parasitic resistance ESR).

[0096] For this embodiment, the first resistor R and the parasitic resistance ESR are equivalent to being in series. Therefore, the existence of the first resistor R is equivalent to increasing the damping resistance, thereby avoiding the generation of spike noise on the waveform of the backlight black insertion signal PWM due to damped oscillation and affecting the stability of the backlight black insertion signal PWM.

[0097] It should be noted that if the first resistor R and the second resistor r are not set, and only the cut-off capacitor C is relied on to absorb the reverse current I of the insertion black driving sub-circuit 11 反 , then a relatively large capacitance value needs to be set for the cut-off capacitor C to play a role. However, if the capacitance value of the cut-off capacitor C is too large, the resonance frequency will be reduced, resulting in the operating frequency of the backlight being higher than the resonance frequency ( , where ω0 represents the resonance frequency, C represents the capacitance value of the cut-off capacitor C, and ESL represents the parasitic inductance), thus showing an inductive characteristic, making the cut-off capacitor C unable to pass the AC signal and reducing the filtering effect. Therefore, the capacitance value of the cut-off capacitor C in the present disclosure cannot be too large.

[0098] In some embodiments, the relationship between the minimum capacitance value of the cut-off capacitor C and the resistance value of the first resistor R satisfies the following formula three:

[0099] C = t / R……………………………Formula Three

[0100] Where C represents the minimum capacitance value of the cut-off capacitor, t represents the unit time, and R is 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.

[0101] In addition, the embodiments of the present disclosure also provide a display device. Figure 9 As shown in the schematic diagram of the display device provided by the embodiments of the present disclosure, Figure 9 the display device includes a backlight source 2, a display panel (not shown in the figure), and a backlight driving circuit 1. Among them, the backlight driving circuit 1 can be considered as the backlight driving circuit 1 in the above various embodiments and their combinations.

[0102] In some embodiments, the display panel of the present disclosure is a liquid crystal display panel.

[0103] In some embodiments, the backlight source 2 of the present disclosure is a side-entry backlight source. Specifically, the backlight source 2 is located on one side of the liquid crystal display panel perpendicular to the light-emitting direction.

[0104] In some embodiments, as Figure 9 shown, the display device further includes a backlight control circuit 20, configured to provide a backlight insertion black signal PWM to the reverse current cut-off sub-circuit 12.

[0105] Exemplarily, the backlight control circuit 20 is, for example, a backlight chip (Integrated Circuit, IC) or a microcontroller unit (MCU). The backlight blanking signal source 3 (i.e., the backlight blanking 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 cut-off capacitor C) in the reverse current cut-off sub-circuit 12, and is used to provide the backlight blanking signal PWM to the reverse current cut-off sub-circuit 12.

[0106] In some embodiments, the backlight control circuit 20 includes one backlight blanking signal source 3; the backlight driving circuit 1 includes multiple ones; each reverse current cut-off sub-circuit 12 in the multiple backlight driving circuits 1 is electrically connected to the same backlight blanking signal source 3, which is beneficial to realizing a small-sized display device.

[0107] The display device is a virtual reality (VR) device or an augmented reality (AR) device. Different from large-sized liquid crystal displays (LCDs), for large-sized LCD products, there can be multiple backlight blanking signal sources 3. Due to the limitation of the number of pins of the backlight chip IC in VR / AR products, the number of pins is limited because of the screen size.

[0108] It should be noted that, as Figure 1 shown in the direct-lit backlight product, compared with the side-lit backlight, there are more light-emitting elements, and the driving current required for the backlight is greater; at the same time, the number of backlight blanking signal sources is larger. Exemplarily, as Figure 1 shown, for the direct-lit backlight, the total number of light-emitting elements is 2304, which is divided into 72 groups of light-emitting element groups. Each group of light-emitting element groups is electrically connected to a switching circuit 011, and each switching circuit 011 is electrically connected to 8 backlight blanking signal sources. Each group of light-emitting element groups includes 32 light-emitting elements LED, and the 32 light-emitting elements LED are divided into eight groups, and 4 light-emitting elements LED in each group are connected in series. In the blanking mode, a single CH terminal can be controlled by 8 backlight blanking signal sources. In order to achieve the same backlight brightness as the side-lit backlight product, the required driving current is smaller. At the same time, the direct-lit backlight product is provided with 72×8 = 576 backlight blanking signal sources (that is, one backlight blanking signal source is set in each LED partition (4 series-connected light-emitting elements), a total of 2304 / 4 = 576 partitions). Therefore, compared with the side-lit backlight product, the direct-lit backlight product is not prone to the problem of burning out of the backlight blanking signal PWM.

[0109] In some embodiments, the backlight 2 includes N groups of light-emitting element groups 21, and each group of light-emitting element groups 21 includes M light-emitting elements LED; wherein, the value range of N is between 1 and 4, and the value range of M is between 1 and 4. Optionally, M = 4.

[0110] Exemplarily, Figure 10 is a schematic diagram of the backlight driving circuit provided by the embodiments of the present disclosure driving the backlight. As Figure 10 shown, for the side-entry backlight, the total number of light-emitting elements LED is 12, which are divided into 4 groups of light-emitting element groups 21, and each group of light-emitting element groups 21 includes 3 light-emitting elements LED connected in series. In order to achieve the same backlight brightness as the direct-lit backlight product, a relatively large driving current is required. At the same time, limited by the size limitation of the small-size display device and the small number of interfaces of the backlight control chip, the number of backlight black insertion signal sources 3 is small, and usually only one backlight black insertion signal source 3 is provided (not shown in the figure). At this time, the reverse current flowing back into the backlight black insertion signal source 3 is the sum of the backflows of each group of light-emitting element groups 21. Without setting the reverse current cut-off sub-circuit 12, the sum of the backflows of each group of light-emitting element groups 21 directly flows into the backlight black insertion signal source 3, which is likely to cause the burnout of the backlight black insertion signal PWM.

[0111] As Figure 10 shown, a reverse current cut-off sub-circuit 12 is provided between the backlight black insertion signal source 3 and the black insertion driving sub-circuit 11. When the backlight driving circuit 1 quickly switches from the normally open mode to the black insertion mode, the reverse current flowing back from the black insertion driving sub-circuit 11 is introduced into the first power supply voltage terminal GND' through the reverse current cut-off sub-circuit 12, thereby avoiding the situation that the parasitic capacitance of the transistor MOS discharges instantaneously and flows back to the backlight black insertion signal source 3, burning out the backlight black insertion signal PWM. In the black insertion mode, the reverse current cut-off sub-circuit 12 introduces the current discharged by the parasitic capacitance into the first power supply voltage terminal GND', thereby avoiding the obstruction of the backlight black insertion signal PWM caused by the discharge of the parasitic capacitance, enabling the light-emitting elements LED in the backlight 2 to emit light stably, and eliminating the phenomenon of insufficient brightness.

[0112] Exemplarily, the backlight driving circuit 1 includes two working modes, one is the normally open mode for controlling the light-emitting element LED to be always on, and the other is the black insertion mode for performing backlight black insertion.

[0113] In the normally open mode, the level of the backlight black insertion signal PWM is a constant first level (for example, a high level); the control poles of the transistors MOS in each switching unit 111 are turned on in response to the backlight black insertion signal PWM of the first level. At this time, the driving current starts to flow through the light-emitting element LED and the switching unit 111 from the second power supply voltage terminal V OUT and finally flows into the first power supply voltage terminal GND', and the light-emitting element LED emits light.

[0114] In the black insertion mode, the control electrodes of the MOS transistors in each switching unit 111 are turned on in response to the backlight black insertion signal PWM at the first level. At this time, the drive current starts to flow through the light-emitting element LED and the switching unit 111 from the second power supply voltage terminal V OUT and finally flows into the first power supply voltage terminal GND’, and the light-emitting element LED emits light. Also, the control electrodes of the MOS transistors in each switching unit 111 are turned off in response to the backlight black insertion signal PWM at the second level. At this time, the drive current cannot pass through the switching unit 111, and the light-emitting element LED is turned off.

[0115] Exemplarily, the display device can 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, a vehicle-mounted device, etc.

[0116] The above is the entire description of the display device. Other essential components of the display device should be understood by those of ordinary skill in the art and will not be elaborated here, nor should it be regarded as a limitation to the present disclosure.

[0117] It can be understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principles of the present disclosure. However, the present disclosure is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present disclosure, and these modifications and improvements are also regarded as the protection scope 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 includes a black insertion driving sub-circuit and a reverse current cut-off sub-circuit; the black insertion driving sub-circuit and the reverse current cut-off sub-circuit are electrically connected; The black insertion driving sub-circuit is configured to control the lighting and extinguishing of the light-emitting elements in the backlight source in response to a backlight black insertion signal flowing through the reverse current cut-off sub-circuit; The reverse current cut-off sub-circuit is configured to introduce a reverse current flowing back from the black insertion driving sub-circuit into the first power voltage terminal when the backlight black insertion signal is switched from the normally open mode to the black insertion mode.

2. The backlight driving circuit according to claim 1, wherein, The black insertion driving sub-circuit 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, and each group of light-emitting element groups includes multiple 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, The multiple light-emitting elements in each group of the light-emitting element groups 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 one group of the light-emitting element groups, the second end of the switch element is electrically connected to the first power voltage terminal, and the second end of the switch element is electrically connected to the reverse current cut-off sub-circuit.

4. The backlight driving circuit according to claim 3, wherein, The switch unit includes a transistor and a load resistor; The first pole of the transistor is electrically connected to the first end of the load resistor, the second pole is electrically connected to the second electrode of one of the light-emitting elements in one group of the light-emitting element groups, and the control pole is electrically connected to the reverse current cut-off sub-circuit; The second end of the load resistor is electrically connected to the first power voltage terminal.

5. The backlight driving circuit according to claim 4, wherein, The reverse current cut-off sub-circuit includes a first resistor and a second resistor; the resistance value of the first resistor is greater than that 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 poles of the transistors; The first end of the second resistor is electrically connected to the control poles of the transistors, and the second end is electrically connected to the first power voltage terminal.

6. The backlight driving circuit according to claim 5, wherein, The reverse current cut-off sub-circuit further includes a cut-off 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 voltage terminal.

7. The backlight driving circuit according to claim 6, wherein, The relationship among 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: U 开 = 2R × r × I 反 / (R + r), where R represents the resistance value of the first resistor, 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 drive 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, where C represents the minimum capacitance value of the cut-off capacitor, t represents the unit time, and R is the resistance value of the first resistor.

9. A display device, which includes 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 cut-off 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 multiple ones; Each of the reverse current cut-off sub-circuits in the multiple 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 perpendicular to the light-emitting direction.

14. The display device according to claim 13, wherein, The backlight includes N groups of light-emitting element groups, and each group of light-emitting element groups 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.

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