CN217955418U

CN217955418U - Backlight driving circuit, liquid crystal display module and liquid crystal display equipment

Info

Publication number: CN217955418U
Application number: CN202220434109.6U
Authority: CN
Inventors: 王灵松
Original assignee: Guangzhou Shiyuan Electronics Thecnology Co Ltd; Guangzhou Shikun Electronic Technology Co Ltd
Current assignee: Guangzhou Shiyuan Electronics Thecnology Co Ltd; Guangzhou Shikun Electronic Technology Co Ltd
Priority date: 2022-03-01
Filing date: 2022-03-01
Publication date: 2022-12-02
Anticipated expiration: 2032-03-01

Abstract

The embodiment of the utility model discloses a backlight driving circuit, a liquid crystal display module and liquid crystal display equipment, wherein the backlight driving circuit comprises a second diode, a third diode, a switching sub-circuit, a detection control sub-circuit and a Boost sub-circuit, and the Boost sub-circuit comprises an input capacitor; a first end of the switching sub-circuit is connected to a first power supply, a second end of the switching sub-circuit is connected with an anode of a second diode, and a cathode of the second diode is connected to a power supply input end of the Boost sub-circuit; the power supply end of the detection control sub-circuit is connected to a first power supply, the detection end of the detection control sub-circuit is used for detecting the voltage of an input capacitor of the Boost sub-circuit, and the control end of the detection control sub-circuit is connected with the controlled end of the switching sub-circuit and used for controlling the conduction state of the switching sub-circuit according to the detection result of the detection end; the anode of the third diode is connected to the first power supply, and the cathode of the third diode is connected with the power supply output end of the Boost sub-circuit. The scheme reduces the overall implementation cost of overcurrent protection.

Description

Backlight driving circuit, liquid crystal display module and liquid crystal display equipment

Technical Field

The embodiment of the utility model provides a relate to liquid crystal technology field, especially relate to drive circuit, liquid crystal display module assembly and liquid crystal display equipment in a poor light.

Background

With the continuous development of semiconductor technology and network technology, liquid crystal display products are widely used. For liquid crystal display products, the entire display function needs to be realized through a matched circuit. Taking a liquid crystal television as an example, as shown in fig. 2, a schematic diagram of a circuit composition inside the liquid crystal television is shown, because the division of the electronic industry is more subdivided, a circuit board inside the liquid crystal television may be from different developers, a PFC (Power Factor Correction) circuit + DC/DC (such as 12V and 22V output) Power circuit comes from a manufacturer a, a CPU (central processing unit) motherboard of the liquid crystal television comes from a manufacturer B, a local dimming control board (which may be a Boost backlight drive board) comes from a manufacturer C, and the like, where the above circuit boards are all standard products of various manufacturers, and a plurality of circuit boards with different functions are collocated to form a control circuit of the television.

In the simplified configuration shown in fig. 2, the TV CPU board normally outputs two signals, PS _ ON and BL _ ON, for controlling the power board to output stable constant voltages (for example, 12V and 22V constant voltages in the above figure), the PS _ ON signal is 380Vdc voltage for turning ON the PFC circuit (high level turn ON) so that the PFC works to output stable, and the two independent DC/DC module converters at the back end convert the 380Vdc voltage into 12V and 22V DC output voltages. The 22Vdc output is controlled by a BL _ ON control signal (normally BL _ ON high-level turn-ON DC/DC module output 22V) from a TV CPU main board, the 12Vdc output is not controlled by any signal and does not need PFC turn-ON, the 12V voltage can be normally output as long as the AC input is in a rated range, and the 22Vdc voltage is used as the input voltage of a regional dimming control board (also can be a backlight driving board).

The main circuit topology of the local dimming control board (which can also be a backlight driving board) is a Boost circuit (namely, the 22Vdc voltage is boosted to a higher output voltage VLED), and the voltage which is enough to drive the LED lamp bar/lamp panel is achieved to light the backlight of the television, so that the picture on the liquid crystal screen is developed; the main structure of the Boost voltage-boosting circuit is shown in fig. 3. Generally, a PFC circuit +2 relatively independent DC/DC modules form a power panel product, and due to the standardized requirements of the circuit product (i.e., one power panel is power-down compatible), the over-current protection (OCP) of the power panel is set to be relatively large; when the Boost circuit is matched as a backlight driving board of a main circuit, if a MOS transistor Q1 of the Boost circuit is short-circuited or an output electrolytic capacitor C2 is short-circuited due to a device life, a quality problem, a severe use environment, an external foreign object, or the like, since an OCP protection point of the DC/DC circuit is high and the DC/DC circuit is repeatedly restarted (since an input voltage 380V of the DC/DC circuit is still stable, a BL _ ON control signal of a TV CPU board exists, the DC/DC circuit is usually continuously maintained or repeatedly restarted), high-temperature smoke of an inductor L1 may be caused, even a fire is caused, and personal safety of a consumer is threatened.

In the prior art, a temperature detection circuit is usually added in a TV CPU mainboard or an overcurrent protection point of DC/DC is reduced to realize short circuit safety protection of the liquid crystal display device, but the former needs to increase the area of a circuit and the mainboard, and the latter needs to provide various circuit board products according to the product needs, so that the technical problem of overhigh integral realization cost exists in the actual production process.

SUMMERY OF THE UTILITY MODEL

The utility model provides a drive circuit, liquid crystal display module and liquid crystal display equipment are shaded to the whole too high technical problem of cost of realization to overcurrent protection in solving current liquid crystal product.

In a first aspect, an embodiment of the present invention provides a backlight driving circuit, including a second diode, a third diode, a switching sub-circuit, a detection control sub-circuit and a Boost sub-circuit, where the Boost sub-circuit includes an input capacitor;

a first end of the switching sub-circuit is connected to a first power supply, a second end of the switching sub-circuit is connected with an anode of the second diode, and a cathode of the second diode is connected to a power supply input end of the Boost sub-circuit;

the power supply end of the detection control sub-circuit is connected to a first power supply, the detection end of the detection control sub-circuit is used for detecting the voltage of the input capacitor of the Boost sub-circuit, and the control end of the detection control sub-circuit is connected with the controlled end of the switching sub-circuit and is used for controlling the conduction state of the switching sub-circuit according to the detection result of the detection end;

and the anode of the third diode is connected to a first power supply, and the cathode of the third diode is connected with the power output end of the Boost sub-circuit.

In a second aspect, an embodiment of the present invention provides a liquid crystal display module, which includes the first aspect of the backlight driving circuit.

In a third aspect, an embodiment of the present invention provides a liquid crystal display device, including the liquid crystal display module set described in the second aspect.

The backlight driving circuit, the liquid crystal display module and the liquid crystal display device comprise a second diode, a third diode, a switching sub-circuit, a detection control sub-circuit and a Boost sub-circuit, wherein the Boost sub-circuit comprises an input capacitor; a first end of the switching sub-circuit is connected to a first power supply, a second end of the switching sub-circuit is connected with an anode of the second diode, and a cathode of the second diode is connected to a power supply input end of the Boost sub-circuit; the power supply end of the detection control sub-circuit is connected to a first power supply, the detection end of the detection control sub-circuit is used for detecting the voltage of the input capacitor of the Boost sub-circuit, and the control end of the detection control sub-circuit is connected with the controlled end of the switching sub-circuit and is used for controlling the conduction state of the switching sub-circuit according to the detection result of the detection end; and the anode of the third diode is connected to a first power supply, and the cathode of the third diode is connected with the power output end of the Boost sub-circuit. The voltage of the input capacitor is detected, and the switch conduction state of the switching sub-circuit is controlled, so that the circuit is protected by a two-stage protection ring based on the second diode and the third diode, the protection of various standard products is realized through a low-cost circuit, and the overall realization cost of overcurrent protection is reduced.

Drawings

Fig. 1 is a schematic circuit diagram of a backlight driving circuit according to an embodiment of the present invention;

FIG. 2 is a schematic diagram showing the circuit configuration inside the liquid crystal television;

FIG. 3 is a circuit schematic of a prior art Boost voltage circuit;

fig. 4 is a schematic circuit diagram of a backlight driving circuit according to an embodiment of the present invention;

fig. 5 is a schematic circuit diagram of another backlight driving circuit according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are for purposes of illustration and are not to be construed as limitations of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

It should be noted that, for the sake of brevity, this description does not exhaust all alternative embodiments, and it should be understood by those skilled in the art after reading this description that any combination of features may constitute an alternative embodiment as long as the features are not mutually inconsistent.

The following examples are described in detail.

Fig. 1 is a schematic circuit diagram of a backlight driving circuit, as shown in the figure, including a second diode D2, a third diode D3, a switching sub-circuit, a detection control sub-circuit and a Boost sub-circuit, where the Boost sub-circuit includes an input capacitor C1;

the first end of the switching sub-circuit is connected to a first power supply, the second end of the switching sub-circuit is connected with the anode of a second diode D2, and the cathode of the second diode D2 is connected to the power supply input end of the Boost sub-circuit;

the power supply end of the detection control sub-circuit is connected to a first power supply, the detection end of the detection control sub-circuit is used for detecting the voltage of an input capacitor C1 of the Boost sub-circuit, and the control end of the detection control sub-circuit is connected with the controlled end of the switching sub-circuit and is used for controlling the conduction state of the switching sub-circuit according to the detection result of the detection end;

the anode of the third diode D3 is connected to the first power supply, and the cathode of the third diode D3 is connected with the power output end of the Boost sub-circuit.

In the scheme, a circuit structure of a backlight driving circuit is shown in fig. 1, a 12V first power supply supplies power to a detection control sub-circuit, the detection control sub-circuit continuously detects the voltage of an input capacitor C1, for example, 22V input is performed when the backlight driving circuit normally works in fig. 1, when the voltage of the input capacitor C1 is detected to be less than 15V, a controlled end of a switching sub-circuit is disconnected based ON the detected voltage, and the situation that when different TV CPU mainboards and power boards are matched, after a BL _ ON signal is given out, 22V stable output is not established or not output is not output, and a Boost sub-circuit starts to work (at the moment, the voltage ON the C1 capacitor is 12V), the Boost sub-circuit triggers over-current lock protection or the Boost sub-circuit is overloaded instantly, so that the TV CPU mainboard is powered off due to 12V power failure and can not start normally; therefore, when the stable output of 22V is detected, the detection & control unit controls the switch to be closed, the loop where the D2 diode is located forms a closed loop, and the D2 diode is reversely biased to be cut off. At this time, since 12V < 22V < VLED, the second diode D2 and the third diode D3 are reversely turned off, and 12V, 22V, and VLED do not affect each other.

Based ON the implementation in fig. 1, for the output end of the backlight driving-end circuit, if the output electrolytic capacitor C2 is short-circuited, which is equivalent to VLED ≈ 0V, VLED < 12V < 22V, the third diode D3 is forward biased to be turned ON, and the first diode D1 and the second diode D2 in the Boost sub-circuit are reverse biased to be turned off, so that the 12V power supply voltage is pulled down to the low level ≈ 0V through D3, and since the 12V power supply of the power supply board is cut off, the power supply of the TV CPU motherboard causes the TV CPU motherboard to enter the default standby state (the backlight is not turned ON in the standby state, PS _ ON, and BL _ ON are both low levels), therefore, 380Vdc outputted by the PFC, BL _ ON for controlling the 22V voltage of the DC/DC output does not exist, no 22Vdc output exists, the inductor L1 and the first diode D1 do not have continuous large current to pass through, there is no high temperature and fire hazard, and a primary protection ring is formed to realize short-circuit protection when equivalent.

Based on the implementation in fig. 1, when a short circuit of a drain D and a source S occurs in a MOS transistor Q1 in the Boost sub-circuit, it is equivalent to that the Boost sub-circuit fails and cannot Boost, and at this time, an inductor L1 (in a direct current state) is equivalent to a wire with an impedance, when a DC/DC voltage enters a hiccup restart period, a 22V output is pulled down to a low level, at this time, a second diode D2 is forward biased to conduct, and similarly, a 12V voltage is also pulled down to a low level so that a power supply failure of a TV CPU motherboard causes the TV CPU motherboard to enter a default standby state, and particularly, a detection control sub-circuit has a delay circuit to prevent the switching switch from being turned off in advance before the 12V voltage is pulled down to the low level by the 22V voltage failure after a short circuit fault, and a protection ring fails. Meanwhile, after the primary protection ring is in open circuit failure and the output electrolytic capacitor C2 is in short circuit failure, 12V can be pulled down through the second diode D2, the inductor L1 and the first diode D1 to enable the television to enter a standby state, continuous large current does not pass through the inductor L1, high temperature and fire danger do not exist, and accordingly the primary protection ring is formed to achieve short circuit protection.

The Boost sub-circuit in fig. 1 includes an input capacitor C1, an output electrolytic capacitor C2, a Boost inductor L1, a diode D1 (freewheeling diode), a MOS transistor Q1 (for switching), a resistor R1 (for driving current limiting), a resistor R2 (for discharging a gate and a source of the MOS transistor Q1), a resistor R3 (for detecting current of the Boost), and a control circuit of the Boost (including a control chip, a chip pin peripheral circuit, and the like), which are the key devices included in the Boost sub-circuit, are the technologies commonly used in the field, specifically, the peripheral circuit of the control chip, and are not specifically shown in fig. 1. FIG. 1 shows a 22V boost output 35V/1A power LED backlight driving circuit.

In contrast, as shown in a loop 1 in fig. 3, when an output electrolytic capacitor C2 in a backlight driving circuit of the prior art is short-circuited due to a fault, 22V forms a loop through an inductor L1 (an inductor winding has impedance and can be equivalently used as a resistor under a direct current condition), a first diode D1, and a second capacitor C2 to GND which are short-circuited, because a DC/DC overcurrent protection point in a power board outputting 22V is high, a continuous large current flows through the loop 1 (or a large current repeatedly intermittently impacted flows through the loop — the DC/DC overcurrent protection is triggered to be repeatedly restarted), meanwhile, a 22V voltage is reduced due to an increased 22V voltage amplitude of a DC/DC load, and is even quickly restarted after being turned off, and the inductor L1 and the first diode D1 cause a high temperature and even fire due to loss.

As shown in a loop 2 in fig. 3, when a circuit fault in a backlight driving circuit of the prior art causes a short circuit between a D pole and an S pole of Q1, 22V returns to GND through an inductor L1, the short-circuited Q1, and a current detection resistor (usually having a very small resistance value and can be regarded as a short-circuit wire approximately) of a Boost circuit to form a loop, which is basically consistent with an analysis principle when an output electrolytic capacitor C2 is short-circuited, and may cause a high temperature of the inductor L1 and even fire.

The comparison can find that the scheme can realize comprehensive protection on the output electrolytic capacitor C2 and the MSO pipe Q1 and effectively reduce the realization cost of the whole product.

In a specific implementation, as shown in fig. 4, the detection control sub-circuit includes a fourth diode D4, a protection diode ZD1, a sixth resistor R6, and a fifth capacitor C5;

the anode of the fourth diode D4 is connected to the anode of the input capacitor C1, the cathode of the fourth diode D4 is connected to the cathode of the protection diode ZD1, the anode of the protection diode ZD1 is connected to the first end of the sixth resistor R6, the first end of the fifth capacitor C5, and the controlled end of the switching sub-circuit, and the second end of the sixth resistor R6 and the second end of the fifth capacitor C5 are both grounded.

Taking the implementation of the switching sub-circuit in fig. 4 as an example, the fourth diode D4 is used as a bias diode, and forms a delay circuit with the fifth capacitor C5 and the sixth resistor R6, where the fifth capacitor C5 is used for filtering, and the sixth resistor is used for voltage division and discharge. When the voltage on the input capacitor C1 is less than 22V (i.e., the DC/DC of the power panel is not output yet), the breakdown conduction voltage of the protection diode ZD1 is not reached, the loop of the fourth diode D4, the protection diode ZD1, and the sixth resistor R6 is not conducted, and the divided voltage on the sixth resistor R6 is not enough to drive the N-type MOS transistor Q2 to be conducted. When the voltage of the input capacitor C1 is greater than 16V, a loop of the fourth capacitor D4, the protection diode ZD1, and the sixth resistor R6 is turned on, a voltage starts to exist on the sixth resistor R6, the capacitor voltage gradually rises along with the first capacitor C1, and when the voltage of the sixth resistor R6 is greater than the turn-on voltage of the N-type MOS transistor Q2 (for example, greater than 3V), the N-type MOS transistor Q2 is turned on, and the P-type MOS transistor Q3 is controlled to be turned on. Namely, a node at which the anode of the protection diode ZD1, the first end of the sixth resistor R6, and the first end of the fifth capacitor C5 are connected serves as a control end of the detection control sub-circuit.

When the MOS transistor Q1 or the output electrolytic capacitor C2 is short-circuited, the voltage on the input capacitor C1 is instantly pulled down, and if the fourth diode D4 and the fifth capacitor C5 are not added (the fifth capacitor C5 usually has larger capacity), the voltage of the G pole of the N-type MOS transistor Q2 is also instantly pulled down synchronously, so that the P-type MOS transistor Q3 is disconnected, and the diode protection ring is open-circuited, so that the protection effect cannot be realized; therefore, the fourth diode D4 is added for biasing, when the input C1 is powered down, the fourth diode D4 is reversely biased to be non-conductive, and the voltage on the fifth capacitor C5 cannot be rapidly discharged (the capacity of the fifth capacitor C5 is large, so that the continuous conduction of the N-type MOS transistor Q2 and the P-type MOS transistor Q3 can be maintained within a period of time), so as to prevent the switching sub-circuit from being turned off in advance before the 12V is pulled down to the low level by the 22V power down after the short-circuit fault occurs, and the protection ring fails.

On the basis of the specific implementation of the detection control sub-circuit, the protection diode is a voltage stabilizing diode or a TVS diode. Corresponding to a specific hardware design, the protection diode is a 16V zener diode or a 16V TVS diode, which is suitable for the design of the power supply voltage shown in fig. 4. If the voltage stabilizing diode is adopted, the voltage stabilizing diode has a high resistance state before reverse breakdown voltage, and is in a low resistance state after the critical point is exceeded, and the voltage stabilizing diode can be used in series, so that a higher voltage stabilizing value can be obtained. If the TVS tube is adopted, the property of the transient suppression diode is utilized, so that the response time of the backlight driving circuit in the scheme is extremely fast and reaches subnanosecond level, and the TVS tube can suppress the energy once the circuit receives the instant high-energy impact.

In a specific implementation, the switching sub-circuit in the present scheme may include a fifth resistor R5, an N-type MOS transistor Q2, a P-type MOS transistor Q3, a seventh resistor R7, an eighth resistor R8, and a fourth capacitor C4;

the first end of the fifth resistor R5 is connected with the control end of the detection control sub-circuit, the second end of the fifth resistor R5 is connected with the grid electrode of the N-type MOS tube Q2, the source electrode of the N-type MOS tube Q2 is grounded, the drain electrode of the N-type MOS tube Q2 is connected with the first end of the seventh resistor R7 and the first end of the eighth resistor R8, the second end of the eighth resistor R8 is connected with the first end of the fourth capacitor C4 and the grid electrode of the P-type MOS tube Q3, the drain electrode of the P-type MOS tube Q3 is connected with the anode of the second diode D2, and the source electrode of the P-type MOS tube Q3, the second end of the fourth capacitor C4 and the second end of the seventh resistor R7 are all connected to a first power supply.

In the design shown in fig. 4, the fifth resistor R5 of the switching sub-circuit is used for limiting current, and when the voltage at the second end (i.e., the left end in fig. 4) of the fifth resistor R5 meets the GS-pole turn-on voltage of the MOS transistor, Q2 is in saturation conduction, and otherwise is turned off. The seventh resistor R7 and the eighth resistor R8 are used for voltage division, and the fourth capacitor C4 is used for filtering. For the P-type MOS transistor Q3, when the N-type MOS transistor Q2 is not turned on, since the S-pole voltage and the G-pole voltage of the P-type MOS transistor Q3 are substantially equal (the G-pole potential pull-up voltage is realized by the presence of the seventh resistor R7 and the eighth resistor R8), the turn-on condition of the P-type MOS transistor Q3 is not satisfied, and the diode protection ring is open; when the N-type MOS transistor Q2 is turned on, the voltage of the S-pole of the P-type MOS transistor Q3 is lower than the voltage of the G-pole (the G-pole potential is pulled down by the presence of the eighth resistor R8), the P-type MOS transistor Q3 is turned on in a saturated state, and the diode protection ring is connected to the Boost sub-circuit.

The design of the two-pole protection ring can avoid that when different TV CPU mainboards and power boards are matched, after a BL _ ON signal is given, stable output is not established and/or output is not output, and the Boost control circuit starts to work (at the moment, the voltage ON the input capacitor C1 is 12V), the Boost control circuit triggers overcurrent deadlock protection or the Boost control circuit instantly pumps too much load to cause 12V power failure to cause the TV CPU mainboard to enter standby state and cannot be normally started.

As another specific implementation manner, as shown in fig. 5, the switching sub-circuit may include a fifth resistor R5, an N-type MOS transistor Q2, and a relay S1;

the first end of a fifth resistor R5 is connected with the control end of the detection control sub-circuit, the second end of the fifth resistor R5 is connected with the grid electrode of an N-type MOS tube Q2, the source electrode of the N-type MOS tube Q2 is grounded, the drain electrode of the N-type MOS tube Q2 is connected with the control end of the relay, the power supply end and the static contact of the relay S1 are both connected with a first power supply, and the movable contact of the relay S1 is connected with the anode of a second diode D2.

In the implementation of fig. 5, compared to the implementation of fig. 4, the switching sub-circuit uses the relay S1 as a switch to achieve a switching effect, the principle is consistent with the implementation of the P-type MOS transistor described above, when the N-type MOS transistor Q2 is not turned on, the

pins

3 and 4 of the relay S1 are off, the first-stage protection ring is open, when the N-type MOS transistor Q2 is turned on, the

pins

3 and 4 of the relay S1 are closed, and the diode protection ring is open.

For the specific implementation of the second diode and the third diode, considering that a large inrush current may occur at the moment of short circuit of the output electrolytic capacitor C2, the type selection of the second diode D2 requires a diode with a large inrush current resistance, such as a GS3JB diode, and the third diode may be selected from the same type or another type of diode with a large inrush current resistance for the same reason.

On the basis of the above embodiment, the present invention further provides a liquid crystal display module including the backlight driving circuit in any of the above embodiments.

Furthermore the utility model also provides a liquid crystal display equipment, including aforementioned liquid crystal display module assembly.

It should be understood that the liquid crystal display module and the liquid crystal display device have the same beneficial effects of the backlight driving circuit.

It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element.

It should be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles applied thereto. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail with reference to the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the scope of the present invention.

Claims

1. The backlight driving circuit is characterized by comprising a second diode, a third diode, a switching sub-circuit, a detection control sub-circuit and a Boost sub-circuit, wherein the Boost sub-circuit comprises an input capacitor;

the power supply end of the detection control sub-circuit is connected to a first power supply, the detection end of the detection control sub-circuit is used for detecting the voltage of the input capacitor of the Boost sub-circuit, and the control end of the detection control sub-circuit is connected with the controlled end of the switching sub-circuit and used for controlling the conduction state of the switching sub-circuit according to the detection result of the detection end;

and the anode of the third diode is connected to a first power supply, and the cathode of the third diode is connected with the power supply output end of the Boost sub-circuit.

2. The backlight driving circuit according to claim 1, wherein the detection control sub-circuit comprises a fourth diode, a protection diode, a sixth resistor and a fifth capacitor;

the anode of the fourth diode is connected with the anode of the input capacitor, the cathode of the fourth diode is connected with the cathode of the protection diode, the anode of the protection diode is connected with the first end of the sixth resistor, the first end of the fifth capacitor and the controlled end of the switching sub-circuit, and the second end of the sixth resistor and the second end of the fifth capacitor are both grounded.

3. The backlight driving circuit of claim 2, wherein the protection diode is a zener diode or a TVS diode.

4. The backlight driving circuit according to claim 3, wherein the protection diode is a 16V voltage regulator diode or a 16V TVS diode.

5. The backlight driving circuit according to any of claims 1-4, wherein the switching sub-circuit comprises a fifth resistor, an N-type MOS transistor, a P-type MOS transistor, a seventh resistor, an eighth resistor, and a fourth capacitor;

the first end of the fifth resistor is connected with the control end of the detection control sub-circuit, the second end of the fifth resistor is connected with the grid electrode of the N-type MOS tube, the source electrode of the N-type MOS tube is grounded, the drain electrode of the N-type MOS tube is connected with the first end of the seventh resistor and the first end of the eighth resistor, the second end of the eighth resistor is connected with the first end of the fourth capacitor and the grid electrode of the P-type MOS tube, the drain electrode of the P-type MOS tube is connected with the anode of the second diode, and the source electrode of the P-type MOS tube, the second end of the fourth capacitor and the second end of the seventh resistor are all connected into the first power supply.

6. The backlight driving circuit according to any one of claims 1-4, wherein the switching sub-circuit comprises a fifth resistor, an N-type MOS transistor and a relay;

the first end of the fifth resistor is connected with the control end of the detection control sub-circuit, the second end of the fifth resistor is connected with the grid electrode of the N-type MOS tube, the source electrode of the N-type MOS tube is grounded, the drain electrode of the N-type MOS tube is connected with the control end of the relay, the power supply end and the static contact of the relay are both connected with the first power supply, and the movable contact of the relay is connected with the anode of the second diode.

7. The backlight driving circuit according to any of claims 1-4, wherein the second diode is a GS3JB diode.

8. The backlight driving circuit according to any of claims 1-4, wherein the third diode is a GS3JB diode.

9. A liquid crystal display module comprising the backlight driving circuit according to any one of claims 1 to 8.

10. A liquid crystal display device comprising the liquid crystal display module according to claim 9.