Short-circuit detection circuit applied to an LED backlight panel

Abstract

The present invention discloses a short - circuit detection circuit applied to an LED backlight panel. The short - circuit detection circuit includes a short - circuit detection unit, an on - chip driving MOS transistor, an operational amplifier, a DAC current module, and a voltage switching unit. A G port and an S port are also provided in the short - circuit detection circuit. The DAC current module generates a first working current and a second working current of the LED string. The voltage switching unit is connected to a first voltage and a second voltage. The voltage switching unit switches to a first voltage input state when the DAC current module outputs the first working current. The voltage switching unit switches to a second voltage input state when the DAC current module outputs the second working current. The first working current is greater than the second working current, and the short - circuit detection unit performs short - circuit detection on the LED string only when the DAC current module outputs the second working current.

Description

Technical Field

[0001] The present invention relates to the technical field of LED driving, and particularly to a short - circuit detection circuit applied to an LED backlight panel. Background Art

[0002] Liquid crystal displays (LCDs) are the most widely used type of display application in modern display panels. The liquid crystal material used in LCD panels itself cannot emit light and requires a backlight source to provide display light. LED backlight panels have advantages such as energy conservation, environmental protection, and high performance, and are widely used in LCD display panels. The performance and reliability of the LED backlight panel driving circuit are crucial for LCD display panels. When an LED lamp short - circuits, the driving control chip of the LED backlight panel needs to detect it in a timely manner and perform corresponding fault operation processing. In the existing LED backlight panels, for the short - circuit detection of an LED lamp string, the chip needs to detect the cathode voltage of the lowest - end LED lamp bead, which increases the number of chip ports and thus the chip cost.

[0003] From Figure 1a and Figure 1b the short - circuit detection circuit of the LED backlight panel in the prior art shown, the short - circuit detection chip in the prior art needs to connect to the LED lamp string through three pins to complete the short - circuit detection of the LED lamp string. Among them, the D pin is used to connect to the low - potential end of the LED lamp string, that is, to connect to the cathode of the lowest - end LED lamp bead. The G pin is used to connect to the gate of the external driving transistor of the LED lamp string at the low - potential end, and the S pin is used to connect to the source of the external driving transistor of the LED lamp string at the low - potential end. When an LED lamp bead short - circuits, the voltage of the D port (the cathode of the lowest - end LED lamp) will increase. There is a detection circuit for the voltage of the D port inside the short - circuit detection chip. By detecting the voltage of the D port, the chip can achieve the short - circuit detection of the LED lamp. However, the above - mentioned short - circuit detection method will cause the overall power consumption of the short - circuit detection circuit to increase while the D port voltage increases. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to solve the problem of increased power consumption of the detection circuit during short - circuit detection of the LED backlight panel, achieve the purpose of reducing the power consumption of the short - circuit detection chip, and at the same time reduce the number of pins of the short - circuit detection circuit chip to reduce the chip manufacturing cost.

[0005] To solve the above - mentioned technical problem, the present invention provides a short - circuit detection circuit for an LED backlight panel. The short - circuit detection circuit includes a short - circuit detection unit, an internal - chip driving MOS transistor, an operational amplifier, a DAC current module, and a voltage switching unit;

[0006] The short - circuit detection circuit is also provided with a G port and an S port. The G port is connected to the gate of an external - chip driving MOS transistor at the low - potential end of the LED string in the LED backlight panel, and the S port is connected to the source of the external - chip driving MOS transistor;

[0007] The short - circuit detection unit is connected to the S port and is used to detect the voltage value at the S port;

[0008] The drain of the internal - chip driving MOS transistor is connected to the S port, the source of the internal - chip driving MOS transistor is connected to the DAC current module, and the DAC current module is connected to the ground. At the same time, the DAC current module generates a first operating current and a second operating current for the LED string;

[0009] The non - inverting input terminal of the operational amplifier is connected to a reference voltage, and the inverting input terminal of the operational amplifier is connected to the source of the internal - chip driving MOS transistor;

[0010] The voltage switching unit is simultaneously connected to the G port, the output terminal of the operational amplifier, and the gate of the internal - chip driving MOS transistor; the voltage switching unit is connected to a first voltage and a second voltage;

[0011] When the DAC current module outputs the first operating current, the voltage switching unit switches to the first - voltage input state; when the DAC current module outputs the second operating current, the voltage switching unit switches to the second - voltage input state; when the voltage switching unit is in the first - voltage input state, the gate of the internal - chip driving MOS transistor is controlled by the first voltage to make the internal - chip driving MOS transistor in the conducting state, and when the voltage switching unit is in the second - voltage input state, the gate of the external - chip driving MOS transistor is controlled by the second voltage to make the external - chip driving MOS transistor in the conducting state;

[0012] The first operating current is greater than the second operating current, and the short - circuit detection unit only performs short - circuit detection on the LED string when the DAC current module outputs the second operating current.

[0013] In one embodiment, when the DAC current module outputs the first operating current, the output terminal of the operational amplifier is controlled to be connected to the G port and thus connected to the gate of the external - chip driving MOS transistor.

[0014] In one embodiment, when the DAC current module outputs the second operating current, the output terminal of the operational amplifier 3 is controlled to be connected to the gate of the internal - chip driving MOS transistor.

[0015] In one embodiment, the DAC current module is controlled by a PWM signal to switch between an on state and an off state. During each period when the DAC current module is in the on state, the DAC current module provides a first operating current or a second operating current, and the average current value provided by the DAC current module is consistent with the preset average operating current value of the LED backlight panel for the LEDs.

[0016] In one embodiment, both the on-chip driving MOS transistor 2 and the off-chip driving MOS transistor 200 are NMOS transistors.

[0017] Another aspect of the present invention also lies in providing a short-circuit detection circuit for an LED backlight panel. The short-circuit detection circuit includes a short-circuit detection unit, an on-chip driving MOS transistor, a first operational amplifier, a second operational amplifier, a voltage switching unit, and a DAC current module;

[0018] The short-circuit detection circuit is provided with a G port and an S port. The G port is connected to the gate of the off-chip driving MOS transistor at the low-potential end of the LED string in the LED backlight panel, and the S port is connected to the source of the off-chip driving MOS transistor;

[0019] The short-circuit detection unit is connected to the S port and is used to detect the voltage value at the S port;

[0020] The drain of the on-chip driving MOS transistor is connected to the S port, the source of the on-chip driving MOS transistor is connected to the DAC current module, the DAC current module 6 is connected to the ground, and at the same time, the DAC current module generates a first operating current and a second operating current for the LED string;

[0021] The non-inverting input terminal of the first operational amplifier is connected to a first reference voltage, and the inverting input terminal of the first operational amplifier is connected to the source of the on-chip driving MOS transistor; the output terminal of the first operational amplifier is connected to the gate of the on-chip driving MOS transistor;

[0022] The non-inverting input terminal of the second operational amplifier is connected to a second reference voltage, the inverting input terminal of the second operational amplifier is connected to the S port, and the output terminal of the second operational amplifier is connected to the voltage switching unit;

[0023] The voltage switching unit is connected to a control voltage; the voltage switching unit switches to the input state of the second operational amplifier when the DAC current module outputs the first operating current; the voltage switching unit switches to the control voltage input state when the DAC current module outputs the second operating current; when the voltage switching unit is in the input state of the second operational amplifier, the output terminal of the second operational amplifier is connected to the G port; when the voltage switching unit is in the control voltage input state, the control voltage is input to the G port;

[0024] The first operating current is greater than the second operating current, and the short - circuit detection unit performs short - circuit detection on the LED string only when the DAC current module outputs the second operating current.

[0025] In one embodiment, the DAC current module is controlled by a PWM signal to switch between an on state and an off state. During each cycle when the DAC current module is in the on state, the DAC current module provides the first operating current or the second operating current, and the average current value provided by the DAC current module is consistent with the preset LED average operating current value of the LED backlight panel.

[0026] In one embodiment, both the on - chip driving MOS transistor 2 and the off - chip driving MOS transistor 200 are NMOS transistors.

[0027] Compared with the prior art, one or more embodiments of the present invention may have the following advantages:

[0028] In the present invention, by using the DAC current module to generate a small current, the short - circuit detection of the LED string is only performed in the small operating current state, thereby effectively reducing the power consumption generated by the short - circuit detection chip itself during short - circuit detection.

[0029] Other features and advantages of the present invention will be described in the following specification, and, in part, will be obvious from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be realized and obtained by the structures specifically pointed out in the specification, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention. In the drawings:

[0031] Figures 1a to 1b is a schematic diagram of a short - circuit detection circuit for an LED string in the prior art;

[0032] Figure 2 is a schematic diagram of the structure of a short - circuit detection circuit for an LED backlight panel according to the first embodiment of the present invention;

[0033] Figure 3 is a timing diagram of the electrical level of the short - circuit detection circuit for an LED backlight panel according to the first embodiment of the present invention;

[0034] Figure 4 is a schematic diagram of the structure of a short - circuit detection circuit for an LED backlight panel according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0036] Before proceeding with the following detailed description, it may be advantageous to set forth definitions of certain words and phrases used throughout this invention. The terms "coupled", "connected" and their derivatives refer to any direct or indirect communication or connection between two or more elements, whether or not those elements are in physical contact with each other. The terms "transmit", "receive" and "communicate" and their derivatives cover both direct and indirect communication. The terms "comprise" and "include" and their derivatives mean including but not limited to. The term "or" is inclusive, meaning and / or. The phrase "associated with" and its derivatives mean including, included within, interconnected, containing, contained within, connected or connected to, coupled or coupled to, communicating with, cooperating with, interlacing, juxtaposed, adjacent, bound or bound to, having, having an attribute, having a relationship or having a relationship with, etc. The term "controller" refers to any device, system or part thereof that controls at least one operation. Such a controller can be implemented in hardware, or in a combination of hardware and software and / or firmware. The functions associated with any particular controller can be centralized or distributed, whether local or remote. The phrase "at least one", when used in conjunction with a list of items, means that different combinations of one or more of the listed items can be used, and it may only be necessary to have one item in the list. For example, "at least one of A, B, C" includes any one of the following combinations: A, B, C, A and B, A and C, B and C, A and B and C.

[0037] In the present invention, the description of the first end and the second end of a resistor, capacitor or inductor is only for distinguishing the two connection ends of the device, so as to facilitate the description of the connection relationship between the device and other devices, and it does not specifically specify a certain end of the resistor, capacitor or inductor in actual situations. Those skilled in the art should be aware that in actual circuit construction, any end of the resistor, capacitor or inductor in the actual device can be defined as the first end, and at the same time when the first end is defined, the other end of the device is automatically defined as the second end.

[0038] Definitions of other specific words and phrases provided throughout this invention. Those of ordinary skill in the art should understand that in many cases, if not most cases, such definitions apply to the prior and future use of the words and phrases so defined.

[0039] In the present invention, the application combinations of modules and the hierarchical division of sub-modules are only for illustration, and within the scope not departing from this disclosure, the application combinations of modules and the hierarchical division of sub-modules can have different forms.

[0040] Example 1

[0041] As Figure 2 shown, the short - circuit detection circuit 100 for an LED backlight panel in this embodiment includes a short - circuit detection unit 1, an on - chip driving MOS transistor 2, an operational amplifier 3, a DAC current module 4, and a voltage switching unit 5.

[0042] A G port and an S port are provided in the short - circuit detection circuit. The G port is connected to the gate of the off - chip driving MOS transistor 200 at the low - potential end of the LED string 300 in the LED backlight panel, and the S port is connected to the source of the off - chip driving MOS transistor 200.

[0043] The short - circuit detection unit 1 is connected to the S port and is used to detect the voltage value at the S port.

[0044] The drain of the on - chip driving MOS transistor 2 is connected to the S port, the source of the on - chip driving MOS transistor 2 is connected to the DAC current module 4, and the DAC current module 4 is connected to the ground.

[0045] The non - inverting input terminal of the operational amplifier 3 is connected to the reference voltage Vref, and the inverting input terminal of the operational amplifier 3 is connected to the source of the on - chip driving MOS transistor 2.

[0046] The voltage switching unit 5 is simultaneously connected to the G port, the output terminal of the operational amplifier 3, and the gate of the on - chip driving MOS transistor 2. At the same time, the voltage switching unit 5 is connected to a first voltage and a second voltage.

[0047] The voltage switching unit 5 can switch between a first - voltage input state and a second - voltage input state according to the magnitude of the LED string working current value of the LED string 300.

[0048] When the LED string working current value is a large current (first working current), the voltage switching unit 5 connects the first voltage to the gate of the on - chip driving MOS transistor 2 and controls the on - chip driving MOS transistor 2 to be in the conducting state. At the same time, the output terminal of the operational amplifier 3 is controlled to be connected to the G port and thus connected to the gate of the off - chip driving MOS transistor 200. At this time, the on - chip driving MOS transistor 2 operates in the linear region and can be approximately regarded as a resistor with a low resistance value, so as to ensure that the voltage at the S port is in a low state, thereby enabling the short - circuit detection chip to operate in a low - power state.

[0049] When the working current value of the LED string is a small current (the second working current), the voltage switching unit 5 connects the second voltage to the G port and thus connects to the gate of the external driving MOS transistor 200 of the chip. Under the action of the second voltage, the external driving MOS transistor 200 of the chip is in a conducting state. At the same time, the output end of the operational amplifier 3 is controlled to connect to the gate of the internal driving MOS transistor 2 of the chip. The short-circuit detection chip performs short-circuit detection in this small-current state. In this case, once a LED bead in the LED string 300 is short-circuited, the voltage value at the S port will increase, which is thus detected by the short-circuit detection unit 1 to achieve short-circuit detection of the LED string 300. Since the working current value of the LED string at this time is small, even if the voltage value at the S port is on the high side, the overall power consumption value of the short-circuit detection chip can be controlled.

[0050] In this embodiment, the function of the DAC current module 4 is to adjust the working current value of the LED string. As Figure 3 shown, the DAC current module 4 is used to adjust the working current of the LED string to change between a large current value and a small current value. By changing the COED value input to the DAC current module 4, the corresponding current value can be obtained. In the present invention, the DAC current module 4 can also be used to adjust the brightness of the LED string.

[0051] In this embodiment, the basis for setting the large current (the first working current) and the small current (the second working current) of the working current value of the LED string is the average working current value of the LED string, and the average working current value of the LED string is preset by the LED backlight panel. Therefore, the first working current and the second working current of the present invention are selected and matched according to the LED backlight panel matched by the short-circuit detection chip of the present invention. When detecting a short circuit of the LED, the voltage at the S port will be relatively high. Therefore, try to reduce the working current value of the LED string during this time period to ensure that the product of the current and the voltage is not too large, and ensure that the system does not trigger overheat protection due to too high power of the chip or safety problems caused by high power, and finally meet that the average value of the large current and the small current of the working current of the LED string is equal to the LED current set by the system.

[0052] In this embodiment, as Figure 3 shown, under the requirement of the average working current value of the LED string, as long as the magnitudes of the first working current value and the second working current value generated by controlling the DAC current module 4 are controlled, and at the same time, the DAC current module 4 is turned on or off by the PWM control signal, the average working current value of the LED string can reach the requirement of the LED backlight panel, and the power consumption of the short-circuit detection chip itself can be reduced as much as possible.

[0053] In this embodiment, the first voltage is set to satisfy the gate turn-on voltage of the driving MOS transistor 2 inside the chip, and the second voltage is set to at least satisfy the gate turn-on voltage of the driving MOS transistor 200 outside the chip. At the same time, the second voltage should be high enough so that the S port can detect the requirement of the short-circuit voltage design value.

[0054] In this embodiment, the reference voltage Vref usually adopts a relatively small voltage value, such as 200 mv, so that in the high-current operating state, the source voltage of the driving MOS transistor 2 inside the chip is relatively low, and thus the voltage of the S port is also pulled down, making the power consumption of the short-circuit detection chip itself in a relatively low state.

[0055] In this embodiment, both the driving MOS transistor 2 inside the chip and the driving MOS transistor 200 outside the chip are NMOS transistors.

[0056] In this embodiment, the small-current period and the large-current period generated by the DAC current module can be adjusted according to requirements. For example, one small-current period is inserted in 64 DAC turn-on periods, and the rest are large-current periods. Or, one small-current period is inserted in 128 DAC turn-on periods, and the rest are large-current periods.

[0057] Or, one small-current period is inserted in 128 DAC turn-on periods, and the rest are large-current periods.

[0058] In this embodiment, the turn-on period and turn-off period of the DAC can be controlled by a PWM control signal or can also be controlled by the internal clock signal of the chip. At the same time, the chip can be set to determine that after several large-current periods (such as the above-mentioned 63 periods or 127 periods) by counting the periods, a small-current period is applied in the next current period, and short-circuit detection is started during this small-current period.

[0059] Example 2

[0060] As Figure 3 shown, the short-circuit detection circuit 100 for the LED backlight panel in this embodiment includes a short-circuit detection unit 1, a driving MOS transistor 2 inside the chip, a first operational amplifier 3, a second operational amplifier 4, a voltage switching unit 5, and a DAC current module 6.

[0061] A G port and an S port are provided in the short-circuit detection circuit. The G port is connected to the gate of the driving MOS transistor 200 at the low-potential end of the LED string 300 in the LED backlight panel, and the S port is connected to the source of the driving MOS transistor 200 outside the chip.

[0062] The short-circuit detection unit 1 is connected to the S port and is used to detect the voltage value at the S port.

[0063] The drain of the driving MOS transistor 2 inside the chip is connected to the S port, the source of the driving MOS transistor 2 inside the chip is connected to the DAC current module 6, and the DAC current module 6 is grounded.

[0064] The non-inverting input terminal of the first operational amplifier 3 is connected to the first reference voltage Vref1, and the inverting input terminal of the first operational amplifier 3 is connected to the source of the driving MOS transistor 2 inside the chip. The output terminal of the first operational amplifier 3 is connected to the gate of the driving MOS transistor 2 inside the chip.

[0065] The non-inverting input terminal of the second operational amplifier 4 is connected to the second reference voltage Vref2, the inverting input terminal of the second operational amplifier 4 is connected to the S port, and the output terminal of the second operational amplifier 4 is connected to the voltage switching unit 5.

[0066] The voltage switching unit 5 can switch between the control voltage input state and the second operational amplifier input state according to the magnitude of the LED string working current value of the LED string 300.

[0067] When the LED string working current value is a large current (the first working current), the voltage switching unit 5 switches to the second operational amplifier input state. At this time, the output terminal of the second operational amplifier 4 is connected to the G port, that is, the output terminal of the second operational amplifier 4 is connected to the gate of the external driving MOS transistor 200 of the chip. At this time, the source voltage of the external driving MOS transistor 200 of the chip is clamped to the second reference voltage Vref2. When the second reference voltage Vref2 is set to a small voltage value, the short-circuit detection chip can be controlled to work in a low-power state.

[0068] When the LED string working current value is a small current (the second working current), the voltage switching unit 5 switches to the control voltage input state. At this time, the control voltage is connected to the G port, that is, the control voltage is connected to the gate of the external driving MOS transistor 200 of the chip, so as to control the external driving MOS transistor 200 of the chip to be in a conducting state. In this state, when there is a short circuit of an LED bead in the LED string 300, the voltage value of the S port will increase, which is thus detected by the short-circuit detection unit 1 to achieve the short-circuit detection of the LED string 300.

[0069] In this embodiment, it is the same as the previous embodiment 1. The DAC current module 4 is used to adjust the working current of the LED string to change between a large current value and a small current value. By changing the COED value input to the DAC current module 4, the corresponding current value can be obtained. In the present invention, the DAC current module 4 can also be used to adjust the brightness of the LED string. And it is also controlled to perform short-circuit detection only during the small current time period.

[0070] In the small current state, although the voltage value at the S port is relatively high, the power consumption of the short-circuit detection chip itself can still be controlled due to the small current value, and there will be no overheating caused by excessive power consumption.

[0071] In this embodiment, the small current period and the large current period generated by the DAC current module can be adjusted according to requirements. For example, one small current period is inserted into 64 DAC enable cycles, and the rest are large current periods. Or, one small current period is inserted into 128 DAC enable cycles, and the rest are large current periods.

[0072] Or, one small current period is inserted into 128 DAC enable cycles, and the rest are large current periods.

[0073] In this embodiment, the DAC enable period and the disable period can be controlled by a PWM control signal or by using the internal clock signal of the chip. At the same time, the chip can be internally set to determine, by counting the periods, that after a certain number of large current periods (such as the above-mentioned 63 periods or 127 periods), a small current period is applied in the next current period, and short-circuit detection is started within this small current period.

[0074] Example 3

[0075] Based on the circuit structure of the above-mentioned Embodiment 1 or 2, in this embodiment, the DAC current module 4 no longer outputs the two current values of large current and small current, but only outputs the average current value for the operation of the LED string.

[0076] In this embodiment, the DAC enable period and the disable period are still generated by a PWM signal or the internal clock signal of the chip. When the DAC is in the enable period, the DAC current module 4 outputs the average current value for the operation of the LED string.

[0077] At the same time, the chip can be internally set to determine, by counting the periods, that short-circuit detection is applied in the next DAC enable period after a certain number of DAC enable periods.

[0078] In this embodiment, similarly, for example, one short-circuit detection period is inserted into 64 DAC enable cycles, and the rest are normal operation cycles; or, one short-circuit detection period is inserted into 128 DAC enable cycles, and the rest are normal operation cycles. As long as the detection time is very short and the interval time is long, it can also ensure relatively low power consumption and no problem of chip overheating.

[0079] Thus, in this embodiment, the circuit state in the short-circuit detection period is the same as the circuit state in the small current state of Embodiment 1 or 2, and the circuit state in the non-short-circuit detection period is the same as the circuit state in the large current state of Embodiment 1 or 2.

[0080] As described above, it is only a specific implementation case of the present invention, and the protection scope of the present invention is not limited thereto. Any person skilled in the art who makes modifications or replacements to the present invention within the technical specifications described in the present invention shall fall within the protection scope of the present invention.

Claims

1. A short - circuit detection circuit applied to an LED backlight panel, characterized in that, The short - circuit detection circuit includes a short - circuit detection unit, an on - chip driving MOS transistor, an operational amplifier, a DAC current module, and a voltage switching unit; The short - circuit detection circuit is further provided with a G port and an S port. The G port is connected to the gate of the off - chip driving MOS transistor at the low - potential end of the LED string in the LED backlight panel, and the S port is connected to the source of the off - chip driving MOS transistor; The short - circuit detection unit is connected to the S port and is used to detect the voltage value at the S port; The drain of the on - chip driving MOS transistor is connected to the S port, the source of the on - chip driving MOS transistor is connected to the DAC current module, the DAC current module is connected to the ground, and at the same time, the DAC current module generates the first working current and the second working current of the LED string; The non - inverting input terminal of the operational amplifier is connected to the reference voltage, and the inverting input terminal of the operational amplifier is connected to the source of the on - chip driving MOS transistor; The voltage switching unit is simultaneously connected to the G port, the output terminal of the operational amplifier, and the gate of the on - chip driving MOS transistor; the voltage switching unit is connected to a first voltage and a second voltage; When the DAC current module outputs the first working current, the voltage switching unit switches to the first - voltage input state; when the DAC current module outputs the second working current, the voltage switching unit switches to the second - voltage input state; When the voltage switching unit is in the first - voltage input state, the gate of the on - chip driving MOS transistor is controlled by the first voltage to make the on - chip driving MOS transistor in the conducting state. When the voltage switching unit is in the second - voltage input state, the gate of the off - chip driving MOS transistor is controlled by the second voltage to make the off - chip driving MOS transistor in the conducting state; The first working current is greater than the second working current, and the short - circuit detection unit performs short - circuit detection on the LED string only when the DAC current module outputs the second working current.

2. The short-circuit detection circuit according to claim 1, wherein When the DAC current module outputs the first working current, the output terminal of the operational amplifier is controlled to be connected to the G port and thus connected to the gate of the off - chip driving MOS transistor.

3. The short-circuit detection circuit according to claim 1, wherein When the DAC current module outputs the second working current, the output terminal of the operational amplifier 3 is controlled to be connected to the gate of the on - chip driving MOS transistor.

4. The short-circuit detection circuit according to claim 1, wherein The DAC current module is controlled by a PWM signal to switch between the on state and the off state. During each cycle when the DAC current module is in the on state, the DAC current module provides the first working current or the second working current, and the average current value provided by the DAC current module is consistent with the preset average working current value of the LEDs in the LED backlight panel.

5. The short - circuit detection circuit according to claim 1, characterized in that, Both the on - chip driving MOS transistor 2 and the off - chip driving MOS transistor 200 are NMOS transistors.

6. A short - circuit detection circuit for an LED backlight panel, characterized in that, The short - circuit detection circuit includes a short - circuit detection unit, an on - chip driving MOS transistor, a first operational amplifier, a second operational amplifier, a voltage switching unit, and a DAC current module; The short - circuit detection circuit is provided with a G port and an S port. The G port is connected to the gate of the external - chip driving MOS transistor at the low - potential end of the LED string in the LED backlight panel, and the S port is connected to the source of the external - chip driving MOS transistor; The short - circuit detection unit is connected to the S port and is used to detect the voltage value at the S port; The drain of the internal - chip driving MOS transistor is connected to the S port, the source of the internal - chip driving MOS transistor is connected to the DAC current module, the DAC current module is grounded, and at the same time, the DAC current module generates the first working current and the second working current of the LED string; The non - inverting input terminal of the first operational amplifier is connected to the first reference voltage, and the inverting input terminal of the first operational amplifier is connected to the source of the internal - chip driving MOS transistor; The output terminal of the first operational amplifier is connected to the gate of the internal - chip driving MOS transistor; The non - inverting input terminal of the second operational amplifier is connected to the second reference voltage, the inverting input terminal of the second operational amplifier is connected to the S port, and the output terminal of the second operational amplifier is connected to the voltage switching unit; The voltage switching unit is connected to a control voltage; the voltage switching unit switches to the input state of the second operational amplifier when the DAC current module outputs the first working current; the voltage switching unit switches to the input state of the control voltage when the DAC current module outputs the second working current; when the voltage switching unit is in the input state of the second operational amplifier, the output terminal of the second operational amplifier is connected to the G port; when the voltage switching unit is in the input state of the control voltage, the control voltage is input to the G port; The first working current is greater than the second working current, and the short - circuit detection unit only performs short - circuit detection on the LED string when the DAC current module outputs the second working current.

7. The short-circuit detection circuit according to claim 6, wherein, The DAC current module is controlled by a PWM signal to switch between the on and off states. In each cycle when the DAC current module is in the on state, the DAC current module provides the first working current or the second working current, and the average current value provided by the DAC current module is consistent with the preset average working current value of the LEDs in the LED backlight panel.

8. The short-circuit detection circuit according to claim 6, wherein, Both the internal - chip driving MOS transistor 2 and the external - chip driving MOS transistor 200 are NMOS transistors.

9. An LED backlight panel driving and controlling chip, characterized in that, The control chip includes the short - circuit detection circuit as described in any one of claims 1 - 8.

10. An LED backlight panel, characterized in that, The LED backlight panel includes the short - circuit detection circuit as described in any one of claims 1 - 8.

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