Backlight protection circuit, circuit board and electronic equipment

Abstract

The utility model relates to the technical field of circuit protection, in particular to a backlight protection circuit, a circuit board and electronic equipment. The circuit comprises a sampling module, a control module and a switch module, the control module is combined with a power supply, and when the sampling module is not conducted, a disconnection signal is output to the switch module to enable the switch module to maintain disconnection; the sampling module is switched on when the low-voltage end of the LED lamp is short-circuited, and controls the control module to output a switch-on signal to the switch module when being switched on, so that the switch module is switched on; and the switch module controls the high-voltage end of the LED lamp to be grounded when being switched on. According to the scheme, the on-off of the switch module can be controlled only by using the voltage of the low-voltage end of the LED lamp, the on-off is directly controlled only by the voltage of the low-voltage end of the LED lamp, the circuit cost and the circuit complexity can be reduced while the short-circuit protection effect is ensured, fewer materials are used, the cost advantage is obvious, and the application range is wide. And the short-circuit protection effect is ensured, and the circuit cost and the circuit complexity can be reduced at the same time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of circuit protection, in particular to a backlight protection circuit, a circuit board and an electronic device. BACKGROUND

[0002] The LED backlight power supply is a light source located behind the liquid crystal display. The light emitting effect of the backlight source will directly affect the display effect of the liquid crystal display. Although it can bring high brightness and rich color visual experience, there are obvious technical defects in the backlight short circuit protection. At present, due to the complexity and high cost of adding the backlight short circuit protection circuit, many mainstream television manufacturers choose to omit this key protection measure. This leads to the fact that once the backlight short circuit occurs, the LED lamp strip is likely to be damaged due to excessive current, which not only affects the life and performance of the television, but also may cause safety hazards. CONTENT OF THE UTILITY MODEL

[0003] The embodiment of the present application mainly solves the technical problems of complex structure and high cost of the existing backlight protection circuit.

[0004] To solve the above technical problems, one technical scheme adopted by the embodiment of the present application is to provide a backlight protection circuit, comprising: a sampling module, a control module and a switching module; the first end of the control module is used for connecting a power supply, the second end of the control module is connected with the second end of the sampling module, the first end of the sampling module is used for connecting a low voltage end of an LED lamp, the third end of the control module is connected with the control end of the switching module, the fourth end of the control module is grounded, the first end of the switching module is used for connecting a high voltage end of the LED lamp, and the second end of the switching module is grounded; the control module is used for outputting an off signal to the switching module when the sampling module is not turned on, so that the switching module is maintained off; the sampling module is used for turning on when the low voltage end of the LED lamp is short-circuited, and controlling the control module to output an on signal to the switching module when turned on, so that the switching module is turned on; and the switching module is used for controlling the high voltage end of the LED lamp to be grounded when turned on.

[0005] The scheme controls the switch module to be turned off by the control module combined with the power output off signal when the low-voltage end of the LED lamp is not short-circuited, so that the normal work of the high-voltage end of the LED lamp is not affected; and controls the switch module to be turned on by the control module combined with the sampling module output on signal when the low-voltage end of the LED lamp is short-circuited, so that the high-voltage end of the LED lamp is grounded. On this basis, when the LED lamp works normally, the voltage of the low-voltage end of the LED lamp to the ground is relatively high, at this time, the voltage difference between the high-voltage end of the LED lamp and the low-voltage end of the LED lamp is normal. When the low-voltage end of the LED lamp is short-circuited, the low-voltage end of the LED lamp is grounded, the sampling module is controlled to be turned on, and then the switch module is controlled to be turned on. After the switch module is turned on, the high-voltage end of the LED lamp is grounded, and the voltage difference between the high-voltage end of the LED lamp and the low-voltage end of the LED lamp becomes very small, so that the large current flowing through the lamp bar of the LED lamp can be prevented, and the safety of the LED lamp is ensured. Based on this, only the voltage of the low-voltage end of the LED lamp is used to control the on-off of the switch module in the scheme, not only the circuit structure is simple, but also the on-off of the switch module is directly controlled by the voltage of the low-voltage end of the LED lamp, which can reduce the cost and complexity of the circuit while ensuring the short-circuit protection effect.

[0006] In some embodiments, the control module comprises a reference unit and a comparison unit; a first end of the reference unit is connected to the power supply, a second end of the reference unit is connected to a first input end of the comparison unit, a third end of the reference unit is connected to a second input end of the comparison unit, and a fourth end of the reference unit is grounded; the second input end of the comparison unit is connected to a second end of the sampling module; a third output end of the comparison unit is connected to a control end of the switch module; the reference unit is configured to provide a reference voltage to the first input end of the comparison unit in combination with the power supply, and to provide a first comparison signal to the second input end of the comparison unit when the sampling module is not turned on; the sampling module is configured to be turned on when the low-voltage end of the LED lamp is short-circuited, and to pull down the first comparison signal when turned on, thereby providing a second comparison signal to the second input end of the comparison unit, wherein the first comparison signal is greater than the reference voltage, and the second comparison signal is less than the reference voltage; the comparison unit is configured to provide an off signal to the switch module when receiving the first comparison signal, so that the switch module remains off, and to provide an on signal to the switch module when receiving the second comparison signal, so that the switch module is turned on. In this scheme, the reference unit provides a reference voltage to the comparison unit in combination with the power supply, and a first comparison signal under normal working conditions, and the sampling module provides a second comparison signal when short-circuited, so that the comparison unit can output an off signal to the switch unit according to the first comparison signal, and output an on signal to the switch unit according to the second comparison signal, thereby rapidly pulling down the high-voltage end of the LED lamp when the low-voltage end of the LED lamp is short-circuited, preventing large current from damaging the LED lamp, and improving the safety of the circuit.

[0007] In some embodiments, the reference unit comprises an energy storage subunit, a voltage stabilizing subunit, a reference voltage dividing subunit, and a comparison voltage dividing subunit; a first end of the energy storage subunit is connected to the power supply, a second end of the energy storage subunit is connected to a first end of the voltage stabilizing subunit, a second end of the voltage stabilizing subunit is connected to a second end of the energy storage subunit, a third end of the voltage stabilizing subunit is connected to a first end of the reference voltage dividing subunit, a second end of the reference voltage dividing subunit is grounded, a third end of the reference voltage dividing subunit is connected to a first input end of the comparison unit, a first end of the comparison voltage dividing subunit is connected to the first end of the energy storage subunit, a second end of the comparison voltage dividing subunit is grounded, and a third end of the comparison voltage dividing subunit is connected to a second input end of the comparison unit and a second end of the sampling module. In this scheme, the energy storage subunit is configured to provide power to the circuit in combination with the power supply, the voltage stabilizing subunit is configured to provide a relatively stable reference voltage to the comparison unit in combination with the reference voltage dividing subunit, and the comparison voltage dividing subunit is configured to provide a first comparison signal under normal conditions to the comparison unit, thereby ensuring the feasibility and stability of the circuit.

[0008] In some embodiments, the energy storage subunit comprises an energy storage capacitor E1 and a capacitor C2, a first end of the energy storage capacitor E1 is connected to the power supply, a second end of the energy storage capacitor E1 is grounded, a first end of the capacitor C2 is connected to the first end of the energy storage capacitor E1, and a second end of the capacitor C2 is connected to the second end of the energy storage capacitor E1. The capacitor E1 in combination with the capacitor C2 stores the power from the power supply, and maintains the power supply of the circuit in the case of short circuit, thereby ensuring the normal operation of the circuit.

[0009] In some embodiments, the voltage stabilizing subunit comprises a resistor R2 and a voltage stabilizing tube U2, a positive electrode of the voltage stabilizing tube U2 is connected to the power supply through the resistor R2, a negative electrode of the voltage stabilizing tube U2 is grounded, and a control end of the voltage stabilizing tube U2 is connected to the first end of the reference voltage dividing subunit and the positive electrode of the voltage stabilizing tube U2. The voltage stabilizing tube U2 in combination with the resistor R2 provides a relatively stable voltage to the comparison unit as a reference voltage, so as to measure the first comparison signal and the second comparison signal, and enable the comparison unit to output different signals according to different received signals.

[0010] In some embodiments, the reference voltage dividing subunit comprises a resistor R7 and a resistor R12, a first end of the resistor R7 is connected to the third end of the voltage stabilizing subunit, a second end of the resistor R7 is connected to the first input end of the comparison unit and a first end of the resistor R12, and a second end of the resistor R12 is grounded. The resistor R7 and the resistor R12 in the present scheme divide the voltage provided by the voltage stabilizing subunit, and in combination with the voltage stabilizing subunit, provide a relatively stable reference voltage to the comparison unit, and the circuit structure is simple.

[0011] In some embodiments, the comparison voltage dividing subunit comprises a resistor R6 and a resistor R13, a first end of the resistor R6 is connected to the first end of the energy storage subunit, a second end of the resistor R6 is connected to the second input end of the comparison unit and a first end of the resistor R13, and a second end of the resistor R13 is grounded. The resistor R6 and the resistor R13 in the present scheme divide the voltage of the power supply, and provide a relatively stable first comparison signal to the comparison unit, wherein the voltage value of the first comparison signal can be adjusted by changing the resistance relationship between the resistor R6 and the resistor R13, so as to set the first comparison signal suitable for specific conditions, thereby facilitating the adaptation to different use environments.

[0012] In some embodiments, the comparison unit comprises a comparator U1A, a resistor R8, a resistor R9 and a diode D2, the first input end of the comparator U1A is connected to the second end of the reference unit, the second input end of the comparator U1A is connected to the second end of the sampling module and the third end of the reference unit, the output end of the comparator U1A is connected to the control end of the switch module through the resistor R8, and the output end of the comparator U1A is also connected to the cathode of the diode D2, and the anode of the diode D2 is also connected to the control end of the switch module through the resistor R9. The scheme takes the comparator as the main device of the comparison unit, and when the LED lamp appears a short circuit condition, the switch module can be rapidly controlled to be turned on according to the received second comparison signal, the high-voltage end of the LED lamp is grounded, and short circuit protection is realized.

[0013] In some embodiments, the sampling module comprises a diode D3 and a resistor R1, the cathode of the diode D3 is connected to the low-voltage end of the LED lamp, and the anode of the diode D3 is connected to the second input end of the comparison unit through the resistor R1. The scheme realizes the output of the second comparison signal in the short circuit condition by using the one-way current limiting effect of the diode. In the normal working condition, the voltage of the low-voltage end of the LED lamp is relatively high with respect to the ground, the sampling module is not turned on under the limitation of the diode, and therefore the output of the first comparison signal to the second input end of the comparison unit is not affected. When the short circuit condition occurs, the low-voltage end of the LED lamp is grounded, the diode is turned on, the first comparison signal is pulled down, the second comparison signal with a lower voltage value is transmitted to the second input end of the comparison unit, the high-voltage end of the LED lamp is grounded, short circuit protection is realized, the response speed is fast, the circuit structure is simple, and the cost is relatively low.

[0014] In some embodiments, the switch module comprises a switch tube Q1, the first end of the switch tube Q1 is connected to the high-voltage end of the LED lamp, the second end of the switch tube Q1 is grounded, and the control end of the switch tube Q1 is connected to the third output end of the comparison unit. The scheme takes the switch tube as a switching device, and when the short circuit condition occurs, the switch tube is turned on according to the received on signal, the high-voltage end of the LED lamp is controlled to be grounded, short circuit protection is realized, the voltage difference between the high-voltage end and the low-voltage end of the LED lamp is prevented from being too large to cause damage to the LED lamp due to large current, and the reliability of the circuit is improved.

[0015] To solve the above technical problems, another technical scheme adopted by the embodiments of the present application is to provide a circuit board comprising the backlight protection circuit.

[0016] To solve the above technical problems, still another technical scheme adopted by the embodiments of the present application is to provide an electronic device comprising the backlight protection circuit.

[0017] Different from the related art, the embodiment of the application provides a backlight protection circuit, a circuit board and an electronic device. The circuit comprises a sampling module, a control module and a switching module. The control module is used for combining a power supply and outputting an off signal to the switching module when the sampling module is not turned on, so that the switching module is maintained off. The sampling module is used for being turned on when a low-voltage end of an LED lamp is short-circuited, and outputting an on signal to the switching module to turn on the switching module when the sampling module is turned on. The switching module is used for connecting a high-voltage end of the LED lamp to ground when the switching module is turned on. The circuit combines the power supply through the control module, and outputs the off signal to the switching module when the low-voltage end of the LED lamp is not short-circuited, so that the switching module is off, and the normal work of the high-voltage end of the LED lamp is not affected. The sampling module is turned on when the low-voltage end of the LED lamp is short-circuited, and the control module is controlled to output the on signal to the switching module through the sampling module, so that the switching module is turned on, the high-voltage end of the LED lamp is connected to ground, short-circuit protection is realized, and a large current is prevented from flowing through a lamp strip of the LED lamp, thereby ensuring the safety of the LED lamp. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a structural block diagram schematic view of a backlight protection circuit provided by the embodiment of the application;

[0019] Figure 2 is a structural block diagram schematic view of a unit in the backlight protection circuit provided by the embodiment of the application;

[0020] Figure 3 is a circuit structure schematic view of a backlight protection circuit provided by the embodiment of the application. DETAILED DESCRIPTION

[0021] In order to facilitate understanding of the application, the application will be described in more detail below in combination with the drawings and specific embodiments. It should be noted that when one element is described as being "connected" to another element, it can be directly connected to the other element or one or more intermediate elements can be present therebetween. In addition, the terms "first", "second", etc. are only for the purpose of description and cannot be understood as indicating or implying relative importance.

[0022] Unless otherwise defined, all technical and scientific terms used in the specification are the same as those commonly understood by those skilled in the art to which the application belongs. The terms used in the specification of the application are only for the purpose of describing the specific embodiments and are not used to limit the application. The term "and / or" used in the specification includes any and all combinations of one or more related listed items.

[0023] In the safety performance of the LED backlight power supply, the short circuit protection design is an important way to ensure the safety and display effect of the LED lamp. The main purpose is to prevent the large current damage of the LED lamp caused by the short circuit of the LED lamp. The short circuit protection is usually triggered when the short circuit of the LED lamp occurs, to prevent the LED lamp from being burned out. In the related technology, the short circuit protection design scheme for the backlight interface is usually complex, and more materials are needed, and the total cost is high.

[0024] To solve the above problems, the backlight protection circuit is provided. The sampling module is arranged at the low-voltage end of the LED lamp, and the control module is combined with the power supply. When the short circuit does not occur, the disconnection signal is provided to the switch module to control the normal work of the high-voltage end of the LED lamp. When the short circuit occurs, the conduction signal is provided to the switch module to control the high-voltage end of the LED lamp to be grounded. In this way, the high-voltage end of the LED lamp is pulled down in time when the short circuit occurs, the effect of large current damage of the LED lamp is avoided, the short circuit protection of the LED lamp is realized, and the safety of the circuit is ensured.

[0025] Based on the technical concept of the above-mentioned embodiment of the present application, the present embodiment is further described.

[0026] The embodiment of the present application provides a backlight protection circuit, as shown in Figure 1 The circuit includes a control module 11, a sampling module 12 and a switch module 13.

[0027] The two ends of the switch module 13 are connected between the power supply 30 and the backlight interface 20, and the on-off of the switch module 13 directly controls the on-off between the power supply 30 and the backlight interface. The first end of the control module 11 is connected to the power supply 30, the second end of the control module 11 is connected to the second end of the sampling module 12, the third end of the control module 11 is connected to the control end of the switch module 13, and the fourth end of the control module 11 is grounded, which is represented by GND in the figure. The first end of the sampling module 12 is connected to the low-voltage end of the LED lamp 10, which is represented by LED- in the figure. The first end of the switch module 13 is connected to the high-voltage end of the LED lamp 10, which is represented by LED+ in the figure, and the second end of the switch module 13 is grounded, that is, GND in the figure.

[0028] In the circuit, when the low-voltage end LED- of the LED lamp 10 is not short-circuited, the LED lamp works normally, the voltage of the low-voltage end LED- of the LED lamp 10 is relatively high, at this time, the sampling module 12 is not turned on, the control module 11 outputs a disconnection signal to the switch module 13 in combination with the power supply 30, so that the switch module 13 is disconnected, and the normal work of the high-voltage end LED+ of the LED lamp 10 is not affected. When the low-voltage end of the LED lamp 10 is short-circuited, the voltage of the low-voltage end LED- of the LED lamp 10 is pulled down to approximately GND, the control sampling module 12 is turned on, the sampling module 12 controls the control module 11 to output a conduction signal to the switch module 13, so that the switch module 13 is turned on, the high-voltage end LED+ of the LED lamp 10 is grounded, and the voltage difference between the high-voltage end of the LED lamp and the low-voltage end of the LED lamp becomes very small, so that the large current flowing through the lamp strip of the LED lamp is prevented, and the safety of the LED lamp is ensured. In the scheme, only the voltage of the low-voltage end of the LED lamp is used to control the on-off of the switch module, not only the circuit structure is simple, but also the on-off is directly controlled by the voltage of the low-voltage end of the LED lamp, the short-circuit protection effect is ensured, and the cost and complexity of the circuit are reduced.

[0029] It can be understood that the power supply 30 in the scheme refers to a circuit structure for supporting power supply for the backlight interface. For example, the power supply 30 can be a power supply device for power supply only, or can be a pin or interface capable of power supply in a certain circuit or mainboard.

[0030] Please refer to Figure 2 The backlight protection circuit provided in the application includes a control module 11.

[0031] The first end of the reference unit 111 is connected to the power supply 30, the second end of the reference unit 111 is connected to the first input end of the comparison unit, the third end of the reference unit 111 is connected to the second input end of the comparison unit, and the fourth end of the reference unit 111 is grounded. The second input end of the comparison unit 112 is also connected to the second end of the sampling module 12, and the third output end of the comparison unit 112 is connected to the control end of the switch module 13. At the same time, the power supply 30 also supplies power to the comparison unit 112.

[0032] In the circuit, when the sampling module 12 is not turned on, the reference unit 111 provides a reference voltage to the first input end of the comparison unit 112 in combination with the power supply 30, and provides a first comparison signal to the second input end of the comparison unit 112, so that the comparison unit 112 outputs an off signal to the switching module 13. When the low-voltage end of the LED lamp is short-circuited, the sampling module 12 is turned on, the first comparison signal is pulled down, and the second comparison signal is provided to the second input end of the comparison unit 112. Wherein, the first comparison signal is greater than the reference voltage, and the second comparison signal is less than the reference voltage. Thus, the switching unit is realized to quickly pull down the high-voltage end of the LED lamp when the low-voltage end of the LED lamp is short-circuited, to prevent large current from causing damage to the LED lamp, and to improve the safety of the circuit.

[0033] Please combine Figure 3 In some embodiments, the above-mentioned reference unit 111 includes an energy storage subunit, a voltage stabilizing subunit, a reference voltage dividing subunit, and a comparison voltage dividing subunit. Specifically, the energy storage subunit includes an energy storage capacitor E1 and a capacitor C2, both ends of the energy storage capacitor E1 are connected to the power supply VCC and the ground GND respectively, and the capacitor C2 is connected in parallel to the energy storage capacitor E1. The energy storage capacitor E1 and the capacitor C2 can store the amount of electricity from the power supply VCC, maintain the power supply of the circuit when a short circuit occurs, and provide a guarantee for the normal operation of the circuit. The voltage stabilizing subunit includes a resistor R2 and a voltage stabilizing tube U2, the positive electrode of the voltage stabilizing tube U2 is connected to the power supply VCC through the resistor R2, the negative electrode of the voltage stabilizing tube U2 is grounded GND, and the control end of the voltage stabilizing tube U2 is connected to the positive electrode of the voltage stabilizing tube U2. The voltage stabilizing tube U2 and the resistor R2 in combination with the energy storage capacitor E1 and the capacitor C2 can provide a relatively stable voltage to the reference voltage dividing subunit, and then in combination with the reference voltage dividing subunit provide a relatively stable reference voltage to the comparison unit. The reference voltage dividing subunit includes a resistor R7 and a resistor R12, both ends of the resistor R7 are connected to the control end of the voltage stabilizing tube U2 and the first input end of the comparison unit respectively, and both ends of the resistor R12 are connected to the first input end of the comparison unit and the ground GND respectively. Through the voltage dividing effect of the resistor R7 and the resistor R12 in combination with the voltage of the control end of the voltage stabilizing tube U2, a relatively stable reference voltage is provided to the comparison unit. The comparison voltage dividing subunit includes a resistor R6 and a resistor R13, both ends of the resistor R6 are connected to the power supply VCC and the second input end of the comparison unit respectively, and both ends of the resistor R13 are connected to the second input end of the comparison unit and the ground GND respectively. Through the voltage dividing of the resistor R6 and the resistor R13 on the power supply voltage, a relatively stable first comparison signal is provided to the comparison unit when the sampling module is not turned on.

[0034] As Figure 3As shown in the figure, in some embodiments, the comparison unit comprises a comparator U1A, a resistor R8, a resistor R9 and a diode D2, the first input end U1A_3 of the comparator U1A is connected between the resistor R7 and the resistor R13, the second input end U1A_2 of the comparator U1A is connected between the resistor R6 and the resistor R12, the second input end U1A_2 of the comparator U1A is also connected to the second end of the sampling module, the third output end U1A_1 of the comparator U1A is connected to the control end of the switch module through the resistor R8; the cathode of the diode D2 is connected to the third output end U1A_1 of the comparator U1A, and the anode of the diode D2 is also connected to the control end of the switch module through the resistor R9. The scheme takes the comparator as the main device of the comparison unit, when the LED lamp does not appear the short circuit condition, according to the received first comparison signal and the reference signal, a low-level off signal is output to the switch module, so that the switch module is turned off, which does not affect the normal work of the LED lamp; when the low-voltage end LED- of the LED lamp appears the short circuit condition, according to the received second comparison signal and the reference signal, a high-level on signal is quickly output to the switch module, the switch module is controlled to be turned on, the high-voltage end LED+ of the LED lamp is grounded, the short circuit protection is realized, the damage of large current to the LED lamp is prevented, and the safety of the circuit is improved.

[0035] As shown in the figure, Figure 3 As shown in the figure, in some embodiments, the sampling module comprises a diode D3 and a resistor R1, the cathode of the diode D3 is connected to the low-voltage end LED- of the LED lamp, and the anode of the diode D3 is connected to the second input end U1A_2 of the comparator U1A through the resistor R1. The scheme realizes the output of the second comparison signal under the short circuit condition by using the one-way current limiting effect of the diode, when the LED lamp works normally, the voltage of the low-voltage end LED- of the LED lamp is relatively high with respect to the ground GND, under the limitation of the diode D3, the sampling module is not turned on, so the first comparison signal will not be output to the second input end U1A_2 of the comparator U1A. When the short circuit condition occurs, the low-voltage end LED- of the LED lamp is grounded, so that the diode D3 is turned on, and then the first comparison signal is pulled down, so that the second comparison signal with a lower voltage value is transmitted to the second input end U1A_2 of the comparator U1A, to control the switch module to be turned on, so that the high-voltage end LED+ of the LED lamp is grounded, the short circuit protection is realized, the response speed is fast, the circuit structure is simple, and the cost is relatively low.

[0036] As shown in the figure, Figure 3As shown, in some embodiments, the switch module includes a switch tube Q1, a first end of the switch tube Q1 is connected to the high voltage end LED+ of the LED lamp, a second end of the switch tube Q1 is grounded GND, a control end of the switch tube Q1 is connected to the third output end U1A_1 of the comparator U1A through the resistor R8, and the control end of the switch tube Q1 is also connected to the third output end U1A_1 of the comparator U1A through the resistor R9 and the diode D2. The scheme takes the switch tube Q1 as a switching device, when a short circuit occurs at the low voltage end LED- of the LED lamp, a conduction signal is received to quickly turn on, the high voltage end LED+ of the LED lamp is grounded, short circuit protection is realized, the voltage difference between the high voltage end and the low voltage end of the LED lamp is prevented from being too large to cause damage to the LED lamp by large current, and the reliability of the circuit is improved.

[0037] Specifically, when the LED lamp is normally working, the power supply VCC charges the energy storage capacitor E1 and supplies power to the comparator U1A, at this time, the voltage of the low voltage end LED- of the LED lamp is relatively high with respect to GND, at least higher than the voltage at the position between the resistor R6 and the resistor R13, the low voltage end LED- of the LED lamp and the second input end U1A_2 of the comparator U1A are not conducted due to the existence of the diode D3, the zener U2 in combination with the resistor R6 and the resistor R13 provides a first comparison signal to the second input end U1A_2 of the comparator U1A, the first comparison signal is greater than the reference voltage, the third output end U1A_1 of the comparator U1A outputs a low level as a disconnection signal to control the switch tube Q1 to maintain a disconnected state through the resistor R8, without affecting the normal work of the LED lamp.

[0038] When the low voltage end LED- of the LED lamp is short-circuited, the voltage of the low voltage end LED- of the LED lamp is pulled down to GND, which is lower than the voltage at the position between the resistor R6 and the resistor R13, the diode D3 is conducted, the voltage at the position between the resistor R6 and the resistor R13 is pulled down, that is, a second comparison signal with a voltage value lower than the reference voltage is provided to the second input end U1A_2 of the comparator U1A, the third output end U1A_1 of the comparator U1A outputs a high level as a conduction signal to control the switch tube Q1 to be turned on through the resistor R8, the high voltage end LED+ of the LED lamp is grounded, so that the voltage of the high voltage end LED+ of the LED lamp is also pulled down to GND, avoiding the voltage difference between the high voltage end and the low voltage end of the LED lamp being too large to cause damage to the LED lamp by large current, and improving the reliability of the circuit.

[0039] The scheme controls the module to combine the power supply, when the low-voltage end of the LED lamp is not short-circuited, outputs a disconnecting signal to the switch module, so that the switch module is disconnected, and the normal work of the high-voltage end of the LED lamp is not affected; and the sampling module is set to be turned on when the low-voltage end of the LED lamp is short-circuited, the control module outputs a conducting signal to the switch module through the sampling module, so that the switch module is turned on, and the high-voltage end of the LED lamp is grounded, the short-circuit protection is realized, and the large current flowing through the light bar of the LED lamp is prevented, and the safety of the LED lamp is ensured. The scheme only uses the voltage of the low-voltage end of the LED lamp to control the on-off of the switch module, and the on-off is directly controlled by the voltage of the low-voltage end of the LED lamp, so that the short-circuit protection effect is ensured, and the cost and complexity of the circuit are reduced, only common devices such as capacitors, resistors, transistors and comparators are needed to build, the materials used are less, and the cost advantage is obvious, the short-circuit protection effect is ensured, and the cost and complexity of the circuit are reduced.

[0040] The circuit board provided by the embodiment of the present application is provided with the backlight protection circuit described above, wherein the circuit board can be an integral board or a plurality of boards spliced together. The circuit board has the corresponding functions and beneficial effects of the backlight protection circuit described above. The technical details not described in detail in the circuit board embodiment can be referred to the backlight protection circuit provided by the embodiment of the present application.

[0041] The electronic device provided by the embodiment of the present application comprises the backlight protection circuit described above, for example, the electronic device can be a liquid crystal display with an LED backlight power supply. The electronic device has the corresponding functions and beneficial effects of the backlight protection circuit described above. The technical details not described in detail in the electronic device embodiment can be referred to the backlight protection circuit provided by the embodiment of the present application.

[0042] It should be noted that the specification and drawings of the present application provide the preferred embodiments of the present application, but the present application can be implemented in many different forms, and is not limited to the embodiments described in the specification. These embodiments are not additional limitations on the content of the present application, and the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive. Furthermore, the above technical features continue to be combined with each other, forming various embodiments not listed above, which are considered to be within the scope of the present application. Furthermore, for those skilled in the art, the above description can be improved or changed, and all these improvements and changes shall fall within the scope of the claims of the present application.

Claims

1. A backlight protection circuit, characterized by, The backlight protection circuit comprises a sampling module, a control module and a switch module; The first end of the control module is connected with a power supply, the second end of the control module is connected with the second end of the sampling module, the first end of the sampling module is connected with a low-voltage end of an LED lamp, the third end of the control module is connected with a control end of the switch module, the fourth end of the control module is grounded, the first end of the switch module is connected with a high-voltage end of the LED lamp, and the second end of the switch module is grounded. The control module is used to output an off signal to the switch module when the sampling module is not turned on, so that the switch module is maintained off. The sampling module is used to be turned on when the low-voltage end of the LED lamp is short-circuited, and control the control module to output an on signal to the switch module when turned on, so that the switch module is turned on. The switch module is used to control the high-voltage end of the LED lamp to be grounded when turned on.

2. The backlight protection circuit of claim 1, wherein, The control module comprises a reference unit and a comparison unit. The first end of the reference unit is connected with the power supply, the second end of the reference unit is connected with the first input end of the comparison unit, the third end of the reference unit is connected with the second input end of the comparison unit, the fourth end of the reference unit is grounded, the second input end of the comparison unit is connected with the second end of the sampling module, and the third output end of the comparison unit is connected with the control end of the switch module. The reference unit is used to provide a reference voltage to the first input end of the comparison unit in combination with the power supply, and provide a first comparison signal to the second input end of the comparison unit when the sampling module is not turned on. The sampling module is used to be turned on when the low-voltage end of the LED lamp is short-circuited, and pull down the first comparison signal to provide a second comparison signal to the second input end of the comparison unit when turned on, wherein the first comparison signal is greater than the reference voltage, and the second comparison signal is less than the reference voltage. The comparison unit is used to provide an off signal to the switch module when receiving the first comparison signal, so that the switch module is maintained off, and provide an on signal to the switch module when receiving the second comparison signal, so that the switch module is turned on.

3. The backlight protection circuit of claim 2, wherein, The reference unit comprises an energy storage subunit, a voltage stabilizing subunit, a reference voltage dividing subunit and a comparison voltage dividing subunit. The first end of the energy storage subunit is connected with the power supply, the second end of the energy storage subunit is connected with the first end of the voltage stabilizing subunit, the second end of the voltage stabilizing subunit is connected with the second end of the energy storage subunit, the third end of the voltage stabilizing subunit is connected with the first end of the reference voltage dividing subunit, the second end of the reference voltage dividing subunit is grounded, the third end of the reference voltage dividing subunit is connected with the first input end of the comparison unit, the first end of the comparison voltage dividing subunit is connected with the first end of the energy storage subunit, the second end of the comparison voltage dividing subunit is grounded, and the third end of the comparison voltage dividing subunit is connected with the second input end of the comparison unit and the second end of the sampling module.

4. The backlight protection circuit of claim 3, wherein, The energy storage subunit comprises an energy storage capacitor E1 and a capacitor C2, a first end of the energy storage capacitor E1 is connected to the power supply, a second end of the energy storage capacitor E1 is grounded, a first end of the capacitor C2 is connected to the first end of the energy storage capacitor E1, and a second end of the capacitor C2 is connected to the second end of the energy storage capacitor E1.

5. The backlight protection circuit of claim 3, wherein, The voltage stabilizing subunit comprises a resistor R2 and a voltage stabilizing tube U2, a positive electrode of the voltage stabilizing tube U2 is connected to the power supply through the resistor R2, a negative electrode of the voltage stabilizing tube U2 is grounded, and a control end of the voltage stabilizing tube U2 is connected to the first end of the reference voltage dividing subunit and the positive electrode of the voltage stabilizing tube U2.

6. The backlight protection circuit of claim 3, wherein, The reference voltage dividing subunit comprises a resistor R7 and a resistor R12, a first end of the resistor R7 is connected to the third end of the voltage stabilizing subunit, a second end of the resistor R7 is connected to the first input end of the comparison unit and a first end of the resistor R12, and a second end of the resistor R12 is grounded.

7. The backlight protection circuit of claim 3, wherein, The comparison voltage dividing subunit comprises a resistor R6 and a resistor R13, a first end of the resistor R6 is connected to the first end of the energy storage subunit, a second end of the resistor R6 is connected to the second input end of the comparison unit and a first end of the resistor R13, and a second end of the resistor R13 is grounded.

8. The backlight protection circuit of claim 2, wherein, The comparison unit comprises a comparator U1A, a resistor R8, a resistor R9 and a diode D2, a first input end of the comparator U1A is connected to the second end of the reference unit, a second input end of the comparator U1A is connected to the second end of the sampling module and the third end of the reference unit, an output end of the comparator U1A is connected to the control end of the switching module through the resistor R8, the output end of the comparator U1A is also connected to the cathode of the diode D2, and the anode of the diode D2 is also connected to the control end of the switching module through the resistor R9.

9. The backlight protection circuit of claim 2, wherein, The sampling module comprises a diode D3 and a resistor R1, a cathode of the diode D3 is connected to the low-voltage end of the LED lamp, and an anode of the diode D3 is connected to the second input end of the comparison unit through the resistor R1.

10. The backlight protection circuit of claim 2, wherein, The switching module comprises a switching tube Q1, a first end of the switching tube Q1 is connected to the high-voltage end of the LED lamp, a second end of the switching tube Q1 is grounded, and a control end of the switching tube Q1 is connected to the third output end of the comparison unit.

11. A circuit board, characterized by The backlight protection circuit comprises the backlight protection circuit according to any one of claims 1-10.

12. An electronic device, comprising: The backlight protection circuit comprises the backlight protection circuit according to any one of claims 1-10.

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