LED short circuit protection circuit
The LED short-circuit protection circuit, built using discrete components, detects the LED short-circuit state and shuts off the power supply, solving the problems of high cost of shunt resistors and power transistor switching stress, and achieving efficient and reliable LED short-circuit protection.
Patent Information
- Application Number
- CN202423154055.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-19
- Publication Date
- 2025-11-25
- Estimated Expiration
- 2034-12-19
AI Technical Summary
In existing LED short-circuit protection circuits, shunt resistors are expensive and reduce product efficiency, and power transistors are susceptible to the stress of drive signal switching, resulting in a shortened lifespan.
An LED short-circuit protection circuit built with discrete components detects the instantaneous state of an LED short circuit and triggers the power supply to shut off, avoiding the use of shunt resistors. The short-circuit detection circuit controls the on and off of the power supply switch.
It reduces costs, decreases heat generation, improves product efficiency, protects power transistors from switching stress damage, and ensures circuit reliability.
Smart Images
Figure CN223600068U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to circuit design technical field, especially relates to a LED short circuit protection circuit. BACKGROUND
[0002] LED has small volume, high brightness, long life and other advantages, is widely used in the field of automobile and industrial market, along with the technical development of LED, the short circuit protection of LED power loop is more and more important.The LED short circuit protection on the market mainly is the detection LED power loop shunt resistance on the current off LED's drive signal, and shunt resistance cost is high and can reduce product efficiency, in addition, only off LED's drive signal, will lead to the power tube in the dimming loop will be affected by switching stress, reduce the life of power tube.
[0003] Therefore, it is necessary to provide a new technical scheme to solve the above problems. UTILITY MODEL CONTENTS
[0004] One of the purposes of the utility model is to provide a kind of LED short circuit protection circuit, it is built by discrete device, by detecting LED short circuit instantaneous state, will trigger LED short circuit protection, to shut off the power supply of LED.This not only saves the cost of shunt resistance, reduces heat and improves the efficiency of product, and power tube will not be damaged by the switching stress caused by the continuous switching of drive circuit.
[0005] According to an aspect of the utility model, the utility model provides a kind of LED short circuit protection circuit, it includes LED lamp string, power tube Q1, power supply switch Q4 and short circuit detection circuit, the first connecting end of power supply switch Q4 is connected with power supply Vbat, and its second connecting end is connected with the input end of LED lamp string;The first connecting end of power tube Q1 is connected with the output end of the LED lamp string, and its second connecting end is grounded, and its control end receives PWM drive signal, and the PWM drive signal is used to drive the power tube Q1 periodic conduction and shut off;The short circuit detection circuit includes power supply end A, detection end B and output end C, the power supply end A is connected with power supply Vbat, the detection end B is connected with the output end of the LED lamp string, the output end C is connected with the control end of power supply switch Q4, the short circuit detection circuit is by detecting whether the output end of the LED lamp string is low level, generates corresponding control signal, and the control signal is output by the output end C, to control the conduction or shut off of power supply switch Q4.
[0006] Further, when the output end of the LED lamp string is detected as low level, the output end C of the short circuit detection circuit outputs the first logic level of the control signal to control the power supply switch Q4 to be turned on; when the output end of the LED lamp string is not detected as low level, the output end C of the short circuit detection circuit outputs the second logic level of the control signal to control the power supply switch Q4 to be turned off.
[0007] Further, the short circuit detection circuit comprises a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a switching device Q2 and a switching device Q3, one end of the resistor R3 is connected with the power supply end A, and the other end thereof is connected with the detection end B; one end of the resistor R4 is connected with the detection end B, and the other end thereof is grounded; the first connection end of the switching device Q3 is connected with the power supply end A through the resistor R6, the second connection end thereof is grounded, and the control end thereof is connected with the detection end B through the resistor R9; the first connection end of the switching device Q2 is connected with the output end C through the resistor R7, the second connection end thereof is grounded, and the control end thereof is connected with the first connection end of the switching device Q3; one end of the resistor R5 is connected with the control end of the switching device Q2, and the other end thereof is grounded; one end of the resistor R8 is connected with the power supply end A, and the other end thereof is connected with the output end C.
[0008] Further, when the output end of the LED lamp string is detected as low level, the switching device Q3 is turned off, and the switching device Q2 is turned on, so that the output end C of the short circuit detection circuit outputs the first logic level of the control signal to control the power supply switch Q4 to be turned on; when the output end of the LED lamp string is not detected as low level, the switching device Q3 is turned on, and the switching device Q2 is turned off, so that the output end C of the short circuit detection circuit outputs the second logic level of the control signal to control the power supply switch Q4 to be turned off.
[0009] Further, the power tube Q1 is an NMOS tube, the first connection end, the second connection end and the control end of the power tube Q1 are the drain, the source and the gate of the NMOS tube respectively; the switching device Q2 is an NPN type triode, the first connection end, the second connection end and the control end of the switching device Q2 are the collector, the emitter and the base of the NPN type triode respectively; the switching device Q3 is an NPN type triode, the first connection end, the second connection end and the control end of the switching device Q3 are the collector, the emitter and the base of the NPN type triode respectively; the power supply switch Q4 is a PMOS tube, the first connection end, the second connection end and the control end of the power supply switch Q4 are the source, the drain and the gate of the PMOS tube respectively.
[0010] Further, the resistance values of the resistors R3 and R4 are selected to satisfy: when the output end of the LED lamp string is not detected as low, the voltage value of the voltage division on the resistor R4 is greater than the turn-on voltage threshold of the switch device Q3, so that the switch device Q3 is in the turn-on state; the resistance values of the resistors R5 and R6 are selected to satisfy: when the switch device Q3 is off, the voltage value of the voltage division on the resistor R5 is greater than the turn-on voltage threshold of the switch device Q2, so that the switch device Q2 is in the turn-on state; the resistance values of the resistors R7 and R8 are selected to satisfy: when the switch device Q2 is on and the switch device Q3 is off, the voltage value of the voltage division on the resistor R8 is greater than the turn-on voltage threshold of the power supply switch Q4, so that the power supply switch Q4 is in the turn-on state.
[0011] Further, the LED short-circuit protection circuit further comprises resistors R1 and R2, one end of the resistor R1 is connected with the PWM driving signal, and the other end thereof is connected with the control end of the power tube Q1; one end of the resistor R2 is connected with the control end of the power tube Q1, and the other end thereof is grounded.
[0012] Further, the resistance values of the resistors R1 and R2 are selected to satisfy: when the PWM driving signal is high, the voltage value of the voltage division on the resistor R2 is greater than the turn-on voltage threshold of the power tube Q1, so that the power tube Q1 is in the turn-on state.
[0013] Compared with the prior art, the utility model discloses discrete device builds, and through detecting LED short-circuit instantaneous state, will trigger LED short-circuit protection, thereby shutting off the power supply of LED. In this way, not only the cost of shunt resistance is saved, the heat is reduced and the efficiency of product is improved, and the power tube will not be damaged by the switching stress of the driving circuit. BRIEF DESCRIPTION OF DRAWINGS
[0014] In order to more clearly illustrate the technical scheme of the embodiments of the utility model, the drawings needed to be used in the embodiment description will be briefly introduced, and obviously, the drawings in the following description are only some embodiments of the utility model, and for those skilled in the art, other drawings can also be obtained according to these drawings without paying the creative labor. Among them:
[0015] Figure 1 It is the circuit schematic diagram of the LED short-circuit protection circuit in an embodiment of the utility model. DETAILED DESCRIPTION
[0016] In order to make the above-mentioned purpose, features and advantages of the utility model more apparent and easy to understand, the utility model will be further explained in detail in combination with the drawings and specific embodiments.
[0017] As used herein, an "embodiment" or "embodiments" means an implementation or implementations, and can include a specific feature, structure, or characteristic in and of itself - and / or it can implement or represent a specific feature, structure, or characteristic that can be combined or implemented in combination with other features, structures, or characteristics. As such, the terminology "in one embodiment" or "in an embodiment" utilized throughout this document refers to an embodiment which can comprise, by itself or in combination with other features, structures, or characteristics, the particular feature, structure, or characteristic being described. However, the describing used throughout this document is not necessarily describing only that one particular feature, structure, or characteristic - and alternative features, structures, or characteristics can be used as and when appropriate. The terminology throughout this document is to be interpreted in the broadest reasonable manner, and it is intended that the embodiments can absorb and shed features, structures, or characteristics when or as appropriate. As used herein, coupling, connected, connecting, and so on are to be construed broadly to include direct and indirect coupling, connection, and so on.
[0018] In the description of the present application, it needs to be understood that the terms "upper", "lower", "front", "back", "front", "back", "left", "right", "vertical", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.
[0019] Please refer to Figure 1 The LED short circuit protection circuit shown in the figure is a circuit schematic diagram of the LED short circuit protection circuit in an embodiment of the present application. Figure 1 The LED short circuit protection circuit shown in the figure includes LED lamp string LED1, power tube (Metal Oxide Semiconductor Field Effect Transistor, Mosfet) Q1, power supply switch Q4 and short circuit detection circuit 110.
[0020] The first connection end of the power supply switch Q4 is connected with the power supply Vbat, and the second connection end is connected with the input end (or positive electrode) of the LED lamp string LED1; the first connection end of the power tube Q1 is connected with the output end (or negative electrode) of the LED lamp string LED1, and the second connection end is grounded, and the control end receives the PWM (Pulse Width Modulation) drive signal, which is used to drive the power tube Q1 to be periodically turned on and turned off; the short circuit detection circuit 110 includes the power supply end A, the detection end B and the output end C, the power supply end A is connected with the power supply Vbat, the detection end B is connected with the output end of the LED lamp string LED1, and the output end C is connected with the control end of the power supply switch Q4; the short circuit detection circuit 110 detects whether the output end of the LED lamp string LED1 is low, and generates a corresponding control signal, which is output through the output end C to control the power supply switch Q4 to be turned on or turned off.
[0021] When a low level is detected at the output terminal of LED1, the output terminal C of the short-circuit detection circuit 110 outputs the first logic level of the control signal to control the power supply switch Q4 to turn on, thereby enabling the power supply Vbat to supply power to LED1. When a low level is not detected at the output terminal of LED1, the output terminal C of the short-circuit detection circuit 110 outputs the second logic level of the control signal to control the power supply switch Q4 to turn off, thereby turning off the power supply Vbat to LED1.
[0022] The short-circuit detection circuit 110 includes resistors R3, R4, R5, R6, R7, R8, and R9, as well as switching devices Q2 and Q3. One end of resistor R3 is connected to power supply terminal A, and the other end is connected to detection terminal B. One end of resistor R4 is connected to detection terminal B, and the other end is grounded. The first connection terminal of switching device Q3 is connected to power supply terminal A via resistor R6, and its second connection terminal is grounded. Its control terminal is connected to detection terminal B via resistor R9. The first connection terminal of switching device Q2 is connected to output terminal C via resistor R7, and its second connection terminal is grounded. Its control terminal is connected to the first connection terminal of switching device Q3. One end of resistor R5 is connected to the control terminal of switching device Q2, and the other end is grounded. One end of resistor R8 is connected to power supply terminal A, and the other end is connected to output terminal C.
[0023] When a low level is detected at the output terminal of LED1, switch Q3 is turned off and switch Q2 is turned on, thereby causing the output terminal C of short-circuit detection circuit 110 to output a low level (which can be called the first logic level of the control signal) to control the power supply switch Q4 to turn on; when a low level is not detected at the output terminal of LED1, switch Q3 is turned on and switch Q2 is turned off, thereby causing the output terminal C of short-circuit detection circuit 110 to output a high level (which can be called the second logic level of the control signal) to control the power supply switch Q4 to turn off.
[0024] exist Figure 1 In the specific embodiment shown, power transistor Q1 is an NMOS transistor, and its first connection terminal, second connection terminal, and control terminal are the drain, source, and gate of the NMOS transistor, respectively; switching device Q2 is an NPN transistor, and its first connection terminal, second connection terminal, and control terminal are the collector, emitter, and base of the NPN transistor, respectively; switching device Q3 is an NPN transistor, and its first connection terminal, second connection terminal, and control terminal are the collector, emitter, and base of the NPN transistor, respectively; power supply switch Q4 is a PMOS transistor, and its first connection terminal, second connection terminal, and control terminal are the source, drain, and gate of the PMOS transistor, respectively.
[0025] The resistance values of the resistors R3 and R4 are selected to satisfy: when the output end of the LED lamp string LED1 is low, the voltage value of the voltage division on the resistor R4 is greater than the conduction voltage threshold of the switching device Q3, so that the switching device Q3 is in the conduction state; the resistance values of the resistors R5 and R6 are selected to satisfy: when the switching device Q3 is off, the voltage value of the voltage division on the resistor R5 is greater than the conduction voltage threshold of the switching device Q2, so that the switching device Q2 is in the conduction state; the resistance values of the resistors R7 and R8 are selected to satisfy: when the switching device Q2 is on and the switching device Q3 is off, the voltage value of the voltage division on the resistor R8 is greater than the conduction voltage threshold of the power supply switch Q4, so that the power supply switch Q4 is in the conduction state.
[0026] Figure 1 The LED short circuit protection circuit also includes resistors R1 and R2, one end of the resistor R1 is connected with the PWM drive signal, and the other end is connected with the control end of the power tube Q1; one end of the resistor R2 is connected with the control end of the power tube Q1, and the other end is grounded. The resistance values of the resistors R1 and R2 are selected to satisfy: when the PWM drive signal is high, the voltage value of the voltage division on the resistor R2 is greater than the conduction voltage threshold of the power tube Q1, so that the power tube Q1 is in the conduction state.
[0027] The working principle of the LED short circuit protection circuit is specifically introduced as follows. Figure 1 The working principle of the LED short circuit protection circuit is specifically introduced as follows.
[0028] 1. When the system is in normal operation (or the LED lamp string LED1 does not appear short circuit), the PWM drive signal is a periodic high-low square wave signal, which can drive the power tube Q1 to be continuously turned on and turned off, so that the luminous brightness of the LED lamp string LED1 can be adjusted according to the different duty ratios of the PWM drive signal. The power supply Vbat, the power supply switch Q4, the LED lamp string LED1 and the power tube Q1 constitute a dimming loop.
[0029] 2、When the system is working normally (or the LED lamp string LED1 does not appear short circuit), when the PWM drive signal is high, the power tube Q1 is NMOS tube, so the power tube Q1 will be turned on, the drain of the power tube Q1 will be pulled to 0V (at this time, the output end of the LED lamp string LED1 is low), the base voltage of the switching device Q3 is clamped to about 0V, the switching device Q3 is NPN triode, so the switching device Q3 is in the off state (or off state), the circuit loop of the power supply Vbat, the resistor R6, the resistor R5 and the switching device Q2 meets the conduction condition of the switching device Q2 (that is, the voltage value of the voltage divider on the resistor R5 is greater than the conduction voltage threshold of the switching device Q2), so the switching device Q2 is turned on, the collector of the switching device Q2 is pulled to 0V, because the power supply switch Q4 is P type Mosfet (PMOS tube), the voltage divider circuit composed of the power supply Vbat, the resistor R8 and the resistor R7 meets the conduction condition of the power supply switch Q4 (that is, the voltage value of the voltage divider on the resistor R8 is greater than the conduction voltage threshold of the power supply switch Q4), so the power supply switch Q4 is turned on. That is, when the LED lamp string LED1 does not appear short circuit and the PWM drive signal is high, the power tube Q1 is turned on, the power supply switch Q4 is turned on, and the power supply Vbat can supply power to the LED lamp string LED1 through the power supply switch Q4, and the LED lamp string LED1 is lit.
[0030] When the PWM drive signal is low, the power tube Q1 is in the off state, and the loop of the LED lamp string LED1 and the power tube Q1 will not affect the base level state of the switching device Q3 (or the output end of the LED lamp string LED1 is not low). At this time, the voltage divider circuit composed of the power supply Vbat, the resistor R3 and the resistor R4 meets the conduction condition of the switching device Q3 (that is, the voltage value of the voltage divider on the resistor R4 is greater than the conduction voltage threshold of the switching device Q3), so the switching device Q3 is turned on, the collector of the switching device Q3 will be pulled to 0V, the base of the switching device Q2 is connected to the collector of Q3, so the base of the switching device Q2 is also 0V, the switching device Q2 is in the off state (or off state), the voltage value of the source and gate of the power supply switch Q4 is the same, which does not meet the conduction condition of the power supply switch Q4, so the power supply switch Q4 is off. That is, when the LED lamp string LED1 does not appear short circuit and the PWM drive signal is low, the power tube Q1 is off, the power supply switch Q4 is off, the power supply Vbat cannot supply power to the LED lamp string LED1 through the power supply switch Q4, and the LED lamp string LED1 is closed (or extinguished).
[0031] 3、When the PWM drive signal is high, if the LED lamp string LED1 suddenly appears short circuit, the drain voltage of the power tube Q1 will suddenly become a high voltage value (also can be said, the output end of the LED lamp string LED1 is not low level), the base voltage of the switching device Q3 will also be lifted to this voltage value, the NPN triode Q3 will be turned on, as described in the above 2, at this time, the switching device Q2 is off, the power supply switch Q4 is off. Even if the LED lamp string LED1 is short-circuited, no current will appear in the loop of the power supply switch Q4, the LED lamp string LED1 and the power tube Q1, ensuring the reliability of the circuit and reducing the switching stress of the power tube Q1. That is to say, when the PWM drive signal is high, if the LED lamp string LED1 suddenly appears short circuit, the short circuit detection circuit 110 will control the power supply switch Q4 to be off, so that the power supply Vbat cannot supply power to the LED lamp string LED1 through the power supply switch Q4 (that is, the power supply loop of the LED is closed), ensuring that the power tube Q1 will not be damaged and reducing the switching stress of the power tube Q1.
[0032] When the PWM drive signal is low, as described in the above 2, the switching device Q3 is turned on, the switching device Q2 is off, and the power supply switch Q4 is off. Since the power supply switch Q4 is always off, the power supply Vbat cannot supply power to the LED lamp string LED1 through the power supply switch Q4, and no current flows through the power tube Q1, so the power tube Q1 will not be affected by the short circuit of the LED lamp string LED1.
[0033] In summary, the LED short circuit protection circuit provided by the present application has the following beneficial effects:
[0034] 1、The utility model discloses a discrete device is built, and the circuit is simple and reliable, and the LED short circuit protection is triggered by detecting the LED short circuit transient state, so that the power supply of the LED is turned off.
[0035] 2、The utility model discloses a short circuit protection for the LED by turning off the power supply of the LED, avoiding the risk that the power tube Q1 is damaged by the shutdown stress of the gate always having the PWM drive signal when short circuit.
[0036] 3、The utility model discloses a short circuit of the LED without detecting through the shunt resistance, reducing the cost, reducing the heat output of the shunt resistance and improving the efficiency of the product.
[0037] It should be pointed out that any modification made by the skilled in the art to the specific embodiments of the utility model does not deviate from the scope of the claims of the utility model. Correspondingly, the scope of the claims of the utility model is not limited to the foregoing specific embodiments.
Claims
1. An LED short circuit protection circuit, characterized by, It includes LED light string, power tube Q1, power supply switch Q4 and short circuit detection circuit, The first connection end of the power supply switch Q4 is connected with the power supply Vbat, and the second connection end is connected with the input end of the LED light string; The first connection end of the power tube Q1 is connected with the output end of the LED light string, the second connection end is grounded, and the control end receives the PWM driving signal, which is used to drive the power tube Q1 to be periodically turned on and turned off; The short circuit detection circuit includes power supply end A, detection end B and output end C, the power supply end A is connected with the power supply Vbat, the detection end B is connected with the output end of the LED light string, and the output end C is connected with the control end of the power supply switch Q4, the short circuit detection circuit generates corresponding control signal by detecting whether the output end of the LED light string is low, and the control signal is output through the output end C to control the power supply switch Q4 to be turned on or turned off.
2. The LED short circuit protection circuit according to claim 1, wherein When it is detected that the output end of the LED light string is low, the output end C of the short circuit detection circuit outputs the first logic level of the control signal to control the power supply switch Q4 to be turned on; When it is not detected that the output end of the LED light string is low, the output end C of the short circuit detection circuit outputs the second logic level of the control signal to control the power supply switch Q4 to be turned off.
3. The LED short circuit protection circuit according to claim 2, wherein The short circuit detection circuit includes resistance R3, resistance R4, resistance R5, resistance R6, resistance R7, resistance R8, resistance R9, switching device Q2 and switching device Q3, One end of the resistance R3 is connected with the power supply end A, and the other end is connected with the detection end B; one end of the resistance R4 is connected with the detection end B, and the other end is grounded; the first connection end of the switching device Q3 is connected with the power supply end A through the resistance R6, the second connection end is grounded, and the control end is connected with the detection end B through the resistance R9; the first connection end of the switching device Q2 is connected with the output end C through the resistance R7, the second connection end is grounded, and the control end is connected with the first connection end of the switching device Q3; one end of the resistance R5 is connected with the control end of the switching device Q2, and the other end is grounded; one end of the resistance R8 is connected with the power supply end A, and the other end is connected with the output end C.
4. The LED short circuit protection circuit according to claim 3, wherein When it is detected that the output end of the LED light string is low, the switching device Q3 is turned off, the switching device Q2 is turned on, so that the output end C of the short circuit detection circuit outputs the first logic level of the control signal to control the power supply switch Q4 to be turned on; When the output end of the LED lamp string is not detected as low, the switch device Q3 is turned on, the switch device Q2 is turned off, and thus the output end C of the short circuit detection circuit outputs a second logic level of the control signal to control the power supply switch Q4 to be turned off. 5.The LED short circuit protection circuit of claim 4, wherein the power tube Q1 is an NMOS tube, the first connection end, the second connection end and the control end of the power tube Q1 are the drain, the source and the gate of the NMOS tube respectively; the switch device Q2 is an NPN triode, the first connection end, the second connection end and the control end of the switch device Q2 are the collector, the emitter and the base of the NPN triode respectively; the switch device Q3 is an NPN triode, the first connection end, the second connection end and the control end of the switch device Q3 are the collector, the emitter and the base of the NPN triode respectively; and the power supply switch Q4 is a PMOS tube, the first connection end, the second connection end and the control end of the power supply switch Q4 are the source, the drain and the gate of the PMOS tube respectively. 6.The LED short circuit protection circuit of claim 4, wherein the resistance values of the resistors R3 and R4 are selected to satisfy: when the output end of the LED lamp string is not detected as low, the voltage value of the voltage division on the resistor R4 is greater than the turn-on voltage threshold of the switch device Q3, so that the switch device Q3 is in the turn-on state; the resistance values of the resistors R5 and R6 are selected to satisfy: when the switch device Q3 is turned off, the voltage value of the voltage division on the resistor R5 is greater than the turn-on voltage threshold of the switch device Q2, so that the switch device Q2 is in the turn-on state; and the resistance values of the resistors R7 and R8 are selected to satisfy: when the switch device Q2 is turned on and the switch device Q3 is turned off, the voltage value of the voltage division on the resistor R8 is greater than the turn-on voltage threshold of the power supply switch Q4, so that the power supply switch Q4 is in the turn-on state. The LED short circuit protection circuit further comprises resistors R1 and R2, one end of the resistor R1 is connected with the PWM driving signal, and the other end of the resistor R1 is connected with the control end of the power tube Q1; one end of the resistor R2 is connected with the control end of the power tube Q1, and the other end of the resistor R2 is grounded. 8.The LED short circuit protection circuit of claim 7, wherein the resistance values of the resistors R1 and R2 are selected to satisfy: when the PWM driving signal is high, the voltage value of the voltage division on the resistor R2 is greater than the turn-on voltage threshold of the power tube Q1, so that the power tube Q1 is in the turn-on state. 7. The LED short protection circuit according to any one of claims 1-6, wherein,