Backlight driving short-circuit protection circuit
By adding diodes D58 and D59 to the LED backlight driver circuit to form a discharge circuit, and using optocoupler control to turn off the power output of PWM chip U7, the problem of current overload when the LED is short-circuited to ground is solved, protecting the light strip from damage and improving the stability of the equipment and the user experience.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-07
- Publication Date
- 2026-03-27
AI Technical Summary
Existing step-down LED backlight circuits lack effective short-circuit protection mechanisms when LEDs experience short circuits to ground, leading to a sharp increase in current, damaging the LED strips and affecting the normal operation of the equipment.
A short-circuit protection circuit for backlight drive was designed. By adding a diode D58 to the negative input port of the light bar and connecting it to the optocoupler control terminal, and adding a diode D59 to ground at the optocoupler control terminal, a discharge circuit is formed. The optocoupler controls the PWM chip U7 to shut down the power output, thereby achieving short-circuit protection.
It effectively prevents light strips from being damaged by short circuits, ensures normal equipment operation, reduces maintenance costs, and enhances product competitiveness.
Smart Images
Figure CN224052837U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to drive circuit technical field, concretely relates to a backlight drive short circuit protection circuit. BACKGROUND
[0002] In various display devices and lighting applications requiring LED backlight, the buck type LED backlight circuit becomes a commonly used circuit form to realize stable and suitable backlight effect due to its advantages of high efficiency and energy saving. This circuit generally adopts the design of series inductance and MOS tube for buck processing of LED, so that the LED light bar can operate under the voltage condition meeting its normal working requirements.
[0003] However, the current buck type LED backlight circuit has safety hazards and stability short boards that cannot be ignored. Once the LED appears an abnormal condition of short circuit to ground, there is no effective short circuit protection mechanism in the entire circuit. At this time, the current in the LED light bar will increase sharply without restraint. Due to the lack of corresponding means to limit the current, once the light bar current rapidly rises to its limit value, the light bar will be damaged due to overheating.
[0004] The damage of the light bar not only causes the backlight function of the related device to be abnormal, affects the use experience, but also increases the maintenance cost, which has a negative impact on the competitiveness of the product in the market. Although the industry has paid attention to the stability and reliability of the LED backlight circuit and has taken improvement measures such as optimizing the circuit layout and selecting high-quality components, but for the key problem of LED short circuit to ground, a feasible solution has not been proposed. UTILITY MODEL CONTENTS
[0005] The utility model aims at the above-mentioned insufficient in prior art, provides a backlight drive short circuit protection circuit.
[0006] The utility model discloses a backlight drive short circuit protection circuit, including power supply circuit and drive circuit, the power supply circuit includes flyback drive module, power output module and voltage feedback module, the drive circuit includes light bar positive input and light bar negative input, the power output module is used to give light bar positive input and light bar negative input power supply;
[0007] The voltage feedback module includes an optocoupler, the optocoupler includes an optocoupler control end and an optocoupler switch end, the optocoupler switch end is connected with the flyback drive module, and the positive pole of the optocoupler control end is connected with the power output module.
[0008] The backlight drive short-circuit protection circuit also includes diodes D59 and D58 and resistor R678; the negative terminal of the optocoupler control terminal is connected to the negative terminal of diode D59; the positive terminal of diode D59 is grounded; the negative terminal of the optocoupler control terminal is connected to the positive terminal of diode D58 through resistor R678; the negative terminal of diode D58 is connected to the negative input port of the light strip.
[0009] The present invention is further configured such that the power supply circuit includes a rectifier and filter input module and a transformer T1; the input terminal of the rectifier and filter input module is connected to the mains power; the output terminal of the rectifier and filter input module is connected to the primary side of the transformer T1; the flyback drive module includes a PWM chip U7 and a MOSFET Q17; the gate of the MOSFET Q17 is connected to the output terminal of the PWM chip U7; the source of the MOSFET Q17 is grounded; the drain of the MOSFET Q17 is connected to the primary side of the transformer T1; one end of the optocoupler switch is grounded; the other end of the optocoupler switch is connected to the PWM chip U7.
[0010] The present invention is further configured such that the power output module includes a first rectifier and filter output module and a second rectifier and filter output module; the input terminal of the first rectifier and filter output module is connected to one end of the secondary side of transformer T1; the input terminal of the second rectifier and filter output module is connected to the middle part of the secondary side of transformer T1; the other end of the secondary side of transformer T1 is grounded; the output terminal of the first rectifier and filter output module is provided with a first power output port; the output terminal of the second rectifier and filter output module is provided with a second power output port.
[0011] The present invention is further configured such that an RCD absorption module is provided between the rectifier filter input module and the primary side of the transformer T1.
[0012] The present invention is further configured such that the driving circuit includes a backlight driving module and a step-down freewheeling module; the output terminal of the backlight driving module is connected to the step-down freewheeling module; the input terminal of the backlight driving module is connected to the second power output port; the input terminal of the step-down freewheeling module is connected to the first power output port; and the positive input port and negative input port of the light strip are respectively connected to the output terminal of the step-down freewheeling module.
[0013] The present invention is further configured such that the backlight driving module includes a PWM chip U14 and a MOSFET Q18; the second power output port is connected to the PWM chip U14; the output terminal of the PWM chip U14 is connected to the gate of the MOSFET Q18; the source of the MOSFET Q18 is grounded through a resistor R189; and the drain of the MOSFET Q18 is connected to a buck freewheeling module.
[0014] The utility model further sets up, voltage feedback module includes resistance R320, resistance R220, resistance R205, electric capacity C190 and resistance R202, second power output mouth is connected with resistance R320 one end and resistance R220 one end respectively, resistance R320 other end is connected with resistance R205 one end, resistance R205 other end is connected with diode D59 negative pole, resistance R320 other end is connected with the positive pole of photocoupler control end, the negative pole of photocoupler control end is connected with diode D59 negative pole, electric capacity C190 is located between resistance R220 other end and resistance R205 other end, resistance R220 other end is grounded through resistance R202.
[0015] The utility model further sets up, voltage feedback module still includes stabilivolt Q16, stabilivolt Q16 input end is connected with the negative pole of photocoupler control end, stabilivolt Q16 ground terminal is grounded, stabilivolt Q16 output end is connected with resistance R220 other end.
[0016] The utility model discloses the beneficial effects: the utility model discloses a diode D58 is connected to the photocoupler control end by increasing in the light bar negative input port, and a diode D59 is added to the ground in the photocoupler control end, can very good realization short circuit protection function, thereby realizes the protection light bar function. BRIEF DESCRIPTION OF DRAWINGS
[0017] The utility model is further explained with the drawings, but the embodiment in the drawing does not constitute any limit to the utility model, and other drawings can be obtained according to the following drawings without the premise of creative labor for ordinary skilled person in the art.
[0018] Fig. 1 It is the circuit principle drawing of the utility model power supply circuit;
[0019] Fig. 2 It is the circuit principle drawing of the utility model drive circuit;
[0020] Wherein: 11, flyback drive module;12, power output module;13, voltage feedback module;14, rectification filter input module;15, RCD absorption module;21, light bar positive input port;22, light bar negative input port;31, photocoupler control end;32, photocoupler switch end;41, first power output port;42, second power output port;61, backlight drive module;62, step-down freewheeling module. DETAILED DESCRIPTION
[0021] The utility model is further described in connection with the following embodiments.
[0022] By Figs. 1-2It can be known that the backlight drive short circuit protection circuit described in the embodiment comprises a power supply circuit and a drive circuit; the power supply circuit comprises a flyback drive module 11, a power supply output module 12 and a voltage feedback module 13; the drive circuit comprises a lamp bar positive input port 21 and a lamp bar negative input port 22; the power supply output module 12 is used for supplying power to the lamp bar positive input port 21 and the lamp bar negative input port 22; the voltage feedback module 13 comprises an optical coupler; the optical coupler comprises an optical coupler control end 31 and an optical coupler switch end 32; the optical coupler switch end 32 is connected with the flyback drive module 11; the positive pole of the optical coupler control end 31 is connected with the power supply output module 12; the backlight drive short circuit protection circuit further comprises a diode D59, a diode D58 and a resistor R678; the negative pole of the optical coupler control end 31 is connected with the negative pole of the diode D59; the positive pole of the diode D59 is grounded; the negative pole of the optical coupler control end 31 is connected with the positive pole of the diode D58 through the resistor R678; the negative pole of the diode D58 is connected with the lamp bar negative input port 22.
[0023] Specifically, the backlight drive short circuit protection circuit described in the embodiment, when in use, respectively connects the positive and negative poles of the lamp bar with the lamp bar positive input port 21 and the lamp bar negative input port 22; when normally working, the lamp bar negative input port 22 is high level, so that the diode D58 is reverse cut-off, the optical coupler control end 31 normally realizes feedback, and the circuit normally works; when the lamp bar negative input port 22 appears short circuit abnormality, the level of the lamp bar negative input port 22 is 0V, the diode D58 is forward conducting, the negative pole of the optical coupler control end 31 is clamped below 0.7V, so that the optical coupler switch end 32 is saturated conduction, the 2 pin level of the PWM chip U7 is pulled low, the 6 pin drive output of the PWM chip U7 is closed, so that the output of the first power supply output port 41 is closed, and the current through the lamp bar is 0V after the output of the first power supply output port 41 is closed, so as to achieve the protection of the lamp bar from being damaged; in addition, by setting the diode D59, a discharge loop can be provided when the lamp bar negative input port 22 appears short circuit abnormality.
[0024] The backlight drive short circuit protection circuit described in the embodiment, the power supply circuit further comprises a rectifier filter input module 14 and a transformer T1; the input end of the rectifier filter input module 14 is connected with the mains; the output end of the rectifier filter input module 14 is connected with the primary side of the transformer T1; the flyback drive module 11 comprises a PWM chip U7 and a MOS tube Q17; the gate of the MOS tube Q17 is connected with the output end of the PWM chip U7; the source of the MOS tube Q17 is grounded; the drain of the MOS tube Q17 is connected with the primary side of the transformer T1; one end of the optical coupler switch end 32 is grounded; the other end of the optical coupler switch end 32 is connected with the PWM chip U7.
[0025] Specifically, through the above setting, the PWM chip U7 outputs a PWM signal to the MOS tube Q17, controls the on-off of the MOS tube Q17, and thus controls the primary side voltage of the transformer T1, so as to output a voltage at the secondary side of the transformer T1.
[0026] The backlight driving short circuit protection circuit provided by the embodiment comprises a power supply output module 12, a rectifier filter input module 14, a transformer T1, a first power supply output port 41, and a second power supply output port 42.
[0027] Specifically, through the above setting, the first power supply output port 41 can output 120V voltage to supply power to the input end of the step-down freewheeling module 62, and the second power supply output port 42 can output 12V to supply power to the PWM chip U14.
[0028] The backlight driving short circuit protection circuit provided by the embodiment comprises a power supply output module 12, a rectifier filter input module 14, a transformer T1, a first power supply output port 41, and a second power supply output port 42.
[0029] The backlight driving short circuit protection circuit provided by the embodiment comprises a power supply output module 12, a rectifier filter input module 14, a transformer T1, a first power supply output port 41, and a second power supply output port 42.
[0030] The backlight driving short circuit protection circuit provided by the embodiment comprises a power supply output module 12, a rectifier filter input module 14, a transformer T1, a first power supply output port 41, and a second power supply output port 42.
[0031] Specifically, the embodiment sets the backlight driving module 61, the PWM chip U14 outputs the PWM signal to the MOS tube Q18, the output frequency of the step-down freewheeling module 62 is controlled by controlling the on-off of the MOS tube Q18, so as to change the brightness of the light bar.
[0032] The voltage feedback module 13 comprises the resistor R320, the resistor R220, the resistor R205, the capacitor C190 and the resistor R202; one end of the resistor R320 and one end of the resistor R220 are connected to the second power output port 42; the other end of the resistor R320 is connected to one end of the resistor R205; the other end of the resistor R205 is connected to the negative electrode of the diode D59; the other end of the resistor R320 is connected to the positive electrode of the optocoupler control end 31; the negative electrode of the optocoupler control end 31 is connected to the negative electrode of the diode D59; the capacitor C190 is arranged between the other end of the resistor R220 and the other end of the resistor R205; the other end of the resistor R220 is grounded through the resistor R202.
[0033] The negative electrode of the optocoupler control end 31 is connected to the port A1, and the negative electrode of the diode D59 is connected to the port A2, so that the negative electrode of the optocoupler control end 31 and the negative electrode of the diode D59 are communicated through the connection of the port A1 and the port A2.
[0034] The voltage feedback module 13 further comprises the voltage stabilizing tube Q16; the input end of the voltage stabilizing tube Q16 is connected to the negative electrode of the optocoupler control end 31; the grounding end of the voltage stabilizing tube Q16 is grounded; and the output end of the voltage stabilizing tube Q16 is connected to the other end of the resistor R220. The above arrangement can enhance the stability of the whole circuit.
[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.
Claims
1. A backlight driver short-circuit protection circuit, characterized in that: It includes a power supply circuit and a drive circuit; the power supply circuit includes a flyback drive module (11), a power output module (12) and a voltage feedback module (13); the drive circuit includes a positive input port (21) and a negative input port (22) for the light strip; the power output module (12) is used to supply power to the positive input port (21) and the negative input port (22) for the light strip. The voltage feedback module (13) includes an optocoupler; the optocoupler includes an optocoupler control terminal (31) and an optocoupler switch terminal (32); the optocoupler switch terminal (32) is connected to the flyback drive module (11); the positive terminal of the optocoupler control terminal (31) is connected to the power output module (12); The backlight drive short-circuit protection circuit also includes diode D59, diode D58 and resistor R678; the negative terminal of the optocoupler control terminal (31) is connected to the negative terminal of diode D59; the positive terminal of diode D59 is grounded; the negative terminal of the optocoupler control terminal (31) is connected to the positive terminal of diode D58 through resistor R678; the negative terminal of diode D58 is connected to the negative input port (22) of the light strip.
2. The backlight driver short-circuit protection circuit according to claim 1, characterized in that: The power supply circuit also includes a rectifier and filter input module (14) and a transformer T1; the input terminal of the rectifier and filter input module (14) is connected to the mains power; the output terminal of the rectifier and filter input module (14) is connected to the primary side of the transformer T1; the flyback drive module (11) includes a PWM chip U7 and a MOSFET Q17; the gate of the MOSFET Q17 is connected to the output terminal of the PWM chip U7; the source of the MOSFET Q17 is grounded; the drain of the MOSFET Q17 is connected to the primary side of the transformer T1; one end of the optocoupler switch (32) is grounded; the other end of the optocoupler switch (32) is connected to the PWM chip U7.
3. The backlight driver short-circuit protection circuit according to claim 2, characterized in that: The power output module (12) includes a first rectifier and filter output module and a second rectifier and filter output module; the input terminal of the first rectifier and filter output module is connected to one end of the secondary side of transformer T1; the input terminal of the second rectifier and filter output module is connected to the middle of the secondary side of transformer T1; the other end of the secondary side of transformer T1 is grounded; the output terminal of the first rectifier and filter output module is provided with a first power output port (41); the output terminal of the second rectifier and filter output module is provided with a second power output port (42).
4. A backlight driver short-circuit protection circuit according to claim 2, characterized in that: An RCD absorption module (15) is provided between the rectifier filter input module (14) and the primary side of the transformer T1.
5. A backlight drive short-circuit protection circuit according to claim 3, characterized in that: The driving circuit includes a backlight driving module (61) and a step-down freewheeling module (62); the output terminal of the backlight driving module (61) is connected to the step-down freewheeling module (62); the input terminal of the backlight driving module (61) is connected to the second power output port (42); the input terminal of the step-down freewheeling module (62) is connected to the first power output port (41); the positive input port (21) and the negative input port (22) of the light strip are respectively connected to the output terminal of the step-down freewheeling module (62).
6. A backlight drive short-circuit protection circuit according to claim 5, characterized in that: The backlight driving module (61) includes a PWM chip U14 and a MOS transistor Q18; the second power output port (42) is connected to the PWM chip U14; the output terminal of the PWM chip U14 is connected to the gate of the MOS transistor Q18; the source of the MOS transistor Q18 is grounded through a resistor R189; and the drain of the MOS transistor Q18 is connected to the buck freewheeling module (62).
7. A backlight drive short-circuit protection circuit according to claim 3, characterized in that: The voltage feedback module (13) includes resistors R320, R220, R205, capacitor C190, and resistor R202; the second power output port (42) is connected to one end of resistor R320 and one end of resistor R220 respectively; the other end of resistor R320 is connected to one end of resistor R205; the other end of resistor R205 is connected to the negative terminal of diode D59; the other end of resistor R320 is connected to the positive terminal of optocoupler control terminal (31); the negative terminal of optocoupler control terminal (31) is connected to the negative terminal of diode D59; capacitor C190 is located between the other end of resistor R220 and the other end of resistor R205; the other end of resistor R220 is grounded through resistor R202.
8. A backlight driving short-circuit protection circuit according to claim 7, characterized in that: The voltage feedback module (13) also includes a Zener diode Q16; the input terminal of the Zener diode Q16 is connected to the negative terminal of the optocoupler control terminal (31); the ground terminal of the Zener diode Q16 is grounded; and the output terminal of the Zener diode Q16 is connected to the other end of the resistor R220.