Dimmable LED drive short circuit self-locking protection circuit of small black box

Abstract

The utility model relates to a light -modulating LED drive short circuit self -locking protection circuit of small black box, include: Mosfet drive circuit is used in chopping control drive power tube Mosfet, LED lamp string, anode connects to power supply power end, cathode connects to power tube Mosfet, LED lamp string is used for emitting light, power tube Mosfet respectively with Mosfet drive circuit, LED lamp string and current detection circuit electricity is connected, power tube Mosfe is used for adjusting the luminance of LED lamp string. Adopt above -mentioned technical scheme, the utility model discloses through Mosfet drive circuit can chopping control drive power Mosfet, LED's anode connects to power supply power end, cathode connects to power Mosfet, like this when through PWM control Mosfet, can adjust the luminance of LED, and current detection circuit is the current value of detection flowing through LED, and short circuit protection self -locking circuit when the loop of LED appears short circuit condition will be triggered, and short circuit protection self -locking circuit will close Mosfet's drive circuit, and will lock the short circuit protection state.

Description

Technical Field

[0001] This utility model relates to the field of LED driver technology, specifically to a dimming LED driver short-circuit self-locking protection circuit for a small black box. Background Technology

[0002] LEDs have advantages such as small size, high brightness, and long lifespan, and are widely used in the automotive and industrial markets. With the development of LED technology, LED driving and protection circuits are becoming increasingly important.

[0003] However, there are two main types of LED driver dimming short-circuit protection circuits on the market: one type uses integrated chip detection for protection, which is expensive and there are not many manufacturers to choose from; the other type relies on the LED power supply to detect short circuits for protection, which will cause the system to power off and restart. Utility Model Content

[0004] The purpose of this utility model is to overcome the defects of the prior art by providing a short-circuit self-locking protection circuit for the dimming LED driver of the small black box, thus solving the problem of short-circuit self-locking protection circuit for the dimming LED driver of the small black box.

[0005] The technical solution of this utility model is: a dimming LED driver short-circuit self-locking protection circuit for a small black box, including: a MOSFET driver circuit for chopper control of driving the power transistor MOSFET. The LED light string has its positive terminal connected to the power supply terminal and its negative terminal connected to the power transistor MOSFET. The LED light string is used to emit light. The power transistor MOSFET is electrically connected to the MOSFET driving circuit, the LED string, and the current detection circuit, respectively. The power transistor MOSFET is used to adjust the brightness of the LED string. The current detection circuit is electrically connected to the power transistor MOSFET and the short-circuit protection self-locking circuit, respectively. The current detection circuit is used to detect the current value flowing through the LED string. The short-circuit protection self-locking circuit is electrically connected to the MOSFET driving circuit, the power transistor MOSFET, and the current detection circuit. The short-circuit protection self-locking circuit is triggered when a short circuit occurs in the circuit of the LED string. The short-circuit protection self-locking circuit will shut down the MOSFET driving circuit and lock the short-circuit protection state.

[0006] In a further embodiment of this invention, the MOSFET driving circuit includes: resistors R1, R2, R3, R4, and R5; transistors Q1 and Q2; wherein the PWM driver is connected to the base of transistor Q1 via one end of resistor R1; one end of resistor R2 is connected to one end of resistor R1 and the PWM driver; the other end of resistor R2 is pulled down to GND; the collector of transistor Q1 is connected to the base of transistor Q2 and one end of resistor R3; VCC is connected to the other end of resistor R3 and to the emitter of transistor Q2; the emitter of transistor Q1 is connected to GND; and the collector of transistor Q2 is connected to resistor R4.

[0007] In a further improvement of this invention, the transistor Q1 is an NPN transistor.

[0008] In a further improvement of this invention, the transistor Q2 is a PNP transistor.

[0009] In a further improvement of this invention, the power transistor MOSFET is an N-type transistor Q3.

[0010] In a further embodiment of this invention, the MOSFET driving circuit further includes a transistor Q4, wherein one end of the resistor R5 is connected to the base of the transistor Q4, and the other end of the resistor R4 is connected to the emitter of the transistor Q4 and the gate of the transistor Q3.

[0011] In a further improvement of this invention, the transistor Q4 is a PNP transistor.

[0012] In a further embodiment of this invention, the short-circuit protection self-locking circuit includes: resistors R6, R7, R8, R9, R10, and R11; diode D1; capacitor C1; transistors Q5, Q6, and Q7. One end of resistor R10 is connected to resistor R11, and the other end of resistor R10 is connected to one end of capacitor C1 and the positive terminal of diode D1. The other end of capacitor C1 is connected to GND. The negative terminal of diode D1 is connected to one end of resistor R9 and the base of transistor Q7. The other end of resistor R9 is connected to the collector of transistor Q6 and one end of resistor R6. The other end of resistor R6 is connected to the base of transistor Q5. The emitter of transistor Q5 is connected to GND. The collector of transistor Q5 is connected to the base of transistor Q1. The emitter of transistor Q6 is connected to VCC and one end of resistor R7. The other end of resistor R7 is connected to the base of transistor Q6 and one end of resistor R8. The other end of resistor R8 is connected to the collector of transistor Q7. The emitter of transistor Q7 is connected to GND.

[0013] In a further embodiment of this invention, the transistor Q6 is a PNP transistor.

[0014] In a further embodiment of this invention, transistor Q5 is an NPN transistor, and transistor Q7 is an NPN transistor.

[0015] The beneficial effects of this utility model are as follows: The MOSFET driving circuit can chop and control the driving power MOSFET. The positive terminal of the LED is connected to the power supply terminal, and the negative terminal is connected to the power MOSFET. In this way, when the MOSFET is controlled by PWM, the brightness of the LED can be adjusted. The current detection circuit detects the current value flowing through the LED. The short circuit protection self-locking circuit is triggered when a short circuit occurs in the LED circuit. The short circuit protection self-locking circuit will shut down the MOSFET driving circuit and lock the short circuit protection state. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a specific embodiment of the present utility model; Figure 2 This is a detailed structural diagram of a specific embodiment of the present utility model.

[0017] In the diagram: 1. MOSFET driver circuit; 2. LED string; 3. Power transistor MOSFET; 4. Current detection circuit; 5. Short circuit protection self-locking circuit. Detailed Implementation

[0018] The technical solutions in this embodiment will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0019] It should be noted that all directional indicators (such as up, down, forward, backward, etc.) in the description of this utility model are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0020] Furthermore, in this utility model, the use of terms such as "first," "second," etc., is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. In the description of this utility model, "a number" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0021] Furthermore, the technical solutions of the various embodiments of this utility model can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0022] like Figure 1-2 As shown, the dimming LED driver short-circuit self-locking protection circuit of the small black box mainly consists of a MOSFET driver circuit 1, an LED string 2, a power MOSFET 3, a current detection circuit 4, and a short-circuit protection self-locking circuit 5. In this embodiment, the small black box adopts a black shell and integrates a control module and a power module, including the dimming LED driver short-circuit self-locking protection circuit. The size of the power control small black box is usually within the range of (length ≤ 400mm, width ≤ 300mm, height ≤ 60mm), which is a compact design. The specific external dimensions of this application are 364mm (length) x 271.5mm (width) x 50mm (height). Within this range and compared with similar power control small black boxes, it has a higher space utilization rate and is more compact.

[0023] MOSFET driver circuit 1 is used for chopping control and driving the power transistor MOSFET. LED string 2, whose positive terminal is connected to the power supply terminal and whose negative terminal is connected to the power transistor MOSFET, is used to emit light; The power transistor MOSFET 3 is electrically connected to the MOSFET driving circuit, the LED string, and the current detection circuit, respectively, and is used to adjust the brightness of the LED string. The current detection circuit 4 is electrically connected to the power transistor MOSFET and the short-circuit protection self-locking circuit, respectively, and is used to detect the current value flowing through the LED string. The short-circuit protection self-locking circuit 5 is electrically connected to the MOSFET driver circuit, the power transistor MOSFET, and the current detection circuit, respectively. Its function is to be triggered when a short circuit occurs in the circuit of the LED string, thereby shutting down the MOSFET driver circuit and locking the short-circuit protection state.

[0024] The power MOSFET is driven by a MOSFET driver circuit using chopper control. The positive terminal of the LED string is connected to the power supply terminal, and the negative terminal is connected to the power MOSFET. Thus, the brightness of the LEDs can be adjusted by controlling the MOSFET through PWM. The current detection circuit is used to detect the current value flowing through the LED. When a short circuit occurs in the LED circuit, the short circuit protection self-locking circuit will be triggered. This circuit will shut down the MOSFET driver circuit and lock the short circuit protection state.

[0025] This application aims to build a hardware short-circuit protection circuit using discrete components. Its advantages are low cost and simple circuit structure. The circuit has a short-circuit protection self-locking function and can directly determine whether the failure is caused by short-circuit protection based on the product's phenomena.

[0026] This circuit provides short-circuit protection for LED dimming circuits through a simple external hardware structure and can lock the short-circuit state, thereby ensuring that the product will not be damaged by repeated short-circuit impacts.

[0027] In this embodiment, as Figure 2 As shown, the MOSFET driver circuit includes: resistors R1, R2, R3, R4, and R5; transistors Q1 and Q2. The PWM driver is connected to the base of transistor Q1 via one end of resistor R1. One end of resistor R2 is connected to one end of resistor R1 and the PWM driver; the other end of resistor R2 is pulled down to GND. The collector of transistor Q1 is connected to the base of transistor Q2 and one end of resistor R3. VCC is connected to the other end of resistor R3 and to the emitter of transistor Q2. The emitter of transistor Q1 is connected to GND, and the collector of transistor Q2 is connected to resistor R4.

[0028] like Figure 2 As shown, transistor Q1 is an NPN transistor, transistor Q2 is a PNP transistor, and the power transistor MOSFET is an N-type transistor Q3.

[0029] In this embodiment, as Figure 2As shown, it also includes a transistor Q4, which is a PNP transistor. One end of resistor R5 is connected to the base of transistor Q4, and the other end of resistor R4 is connected to the emitter of transistor Q4 and the gate of transistor Q3.

[0030] The PWM drive is a high and low level square wave waveform. R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, and R11 are resistors. Q1, Q5, and Q7 are NPN transistors. Q2, Q4, and Q6 are PNP transistors. Q3 is an N-type MOSFET. LED1 is an LED string. C1 is a capacitor. D1 is a diode. VCC is the power supply voltage for the driver circuit, Vbat is the LED dimming power supply, the PWM driver is connected to the base of Q1 through one end of R1, one end of R2 is connected to one end of R1 and the PWM driver, and the other end is pulled down to GND. The pull-down of R2 to ground is for the reliable turn-off of transistor Q1. The collector of Q1 is connected to the base of Q2 and one end of R3, and VCC is connected to the other end of R3 to the emitter of Q2. The emitter of Q1 is connected to GND, the collector of Q2 is connected to one end of R4 and R5 and the base of Q4, and the other end of R4 is connected to the emitter of Q4 and the gate of Q3. R1, R2, R3, R4, R5, Q1, Q2, Q4 and VCC constitute the MOSFET driver circuit.

[0031] The positive terminal of LED1 is connected to Vbat, and the negative terminal is connected to the drain of Q3. The source of Q3 is connected to one end of R11, and the other end of R11 is connected to GND. LED1, Q3, and R11 form the main circuit of the dimming LED. Under normal conditions, this circuit completes the dimming function of the LED.

[0032] In this embodiment, as Figure 2 As shown, the short-circuit protection self-locking circuit includes: resistors R6, R7, R8, R9, R10, and R11, diode D1, capacitor C1, transistors Q5, Q6, and Q7, where transistor Q6 is a PNP transistor, transistor Q5 is an NPN transistor, and transistor Q7 is an NPN transistor.

[0033] One end of resistor R10 is connected to resistor R11. The other end of resistor R10 is connected to one end of capacitor C1 and the positive terminal of diode D1. The other end of capacitor C1 is connected to GND. The negative terminal of diode D1 is connected to one end of resistor R9 and the base of transistor Q7. The other end of resistor R9 is connected to the collector of transistor Q6 and one end of resistor R6. The other end of resistor R6 is connected to the base of transistor Q5. The emitter of transistor Q5 is connected to GND. The collector of transistor Q5 is connected to the base of transistor Q1. The emitter of transistor Q6 is connected to VCC and one end of resistor R7. The other end of resistor R7 is connected to the base of transistor Q6 and one end of resistor R8. The other end of resistor R8 is connected to the collector of transistor Q7. The emitter of transistor Q7 is connected to GND.

[0034] One end of R10 is connected to R11, and the other end is connected to one end of C1 and the positive terminal of D1. The other end of C1 is connected to GND. The negative terminal of D1 is connected to one end of R9 and the base of Q7. The other end of R9 is connected to the collector of Q6 and one end of R6. The other end of R6 is connected to the base of Q5. The emitter of Q5 is connected to GND. The collector of Q5 is connected to the base of Q1. The emitter of Q6 is connected to VCC and one end of R7. The other end of R7 is connected to the base of Q6 and one end of R8. The other end of R8 is connected to the collector of Q7. The emitter of Q7 is connected to GND.

[0035] R10 and C1 form an RC filter to filter out interference signals from the current sampling resistor R11. The sampled voltage on R11, after passing through the filter, together with D1, Q7, R7, R8, R9, Q6, R6, Q5 and VCC, forms a short-circuit protection self-locking circuit. When there is a short circuit in the LED dimming circuit, this short-circuit self-locking protection function will be activated.

[0036] Circuit design principles: Normal system operation: The PWM driver outputs a PWM square wave. When the PWM level is high, NPN transistor Q1 is saturated and conducting, its collector is pulled down to 0V, and the base of PNP transistor Q2 is also 0V. Q2 meets the saturation conduction condition, and its collector voltage is basically the same as VCC. Since Q4 is a PNP transistor, its base and emitter voltages are the same, so the conduction condition for Q4 is not met, and Q4 is in the off state. Thus, VCC, through Q2 and R4, can drive Q3 to conduct. When the PWM level is low, Q1 does not meet the conduction condition and is in the off state. The emitter and base voltages of Q2 are the same, and since Q2 is a PNP transistor, it is in the off state. The base of Q4 is pulled down to GND through R5. With Q2 in the off state, Q4 will be in a saturated conduction state, which can quickly discharge the gate voltage of Q3 to 0V. Thus, the brightness of LED1 can be adjusted according to the different PWM duty cycles.

[0037] Normal operating condition of the protection circuit: During normal operation, the current flowing through the current sampling resistor R11 is very small, and the voltage drop across R11 is also relatively small, failing to reach the bias voltage required for Q5 and Q7 to conduct. Therefore, NPN transistors Q5 and Q7 are in the off state. Q6 is a PNP transistor. Because Q7 is in the off state, the base of transistor Q6 is pulled up to VCC through R7. The base voltage of Q6 is basically the same as the collector voltage of Q6, so Q6 is also in the off state. Therefore, the voltage of VCC will not affect the collector voltage of Q6, will not cause Q5 to conduct, and will not affect the drive circuit of Q3. Therefore, when the system is operating normally, the short-circuit protection self-locking circuit does not affect the normal operation of the system.

[0038] Short-circuit protection and self-locking mechanism: When LED1 is short-circuited in the drive circuit, the current flowing through R11 is very large, and the voltage drop across R11 is also very large, exceeding the forward voltage drop of D1 plus the bias voltage of NPN transistors Q5 and Q7. Thus, after Q5 and Q7 turn on, their collectors are pulled down to 0V. The conduction of Q5 can quickly turn off the base drive of Q1. Referring to the theory in point one above, Q3 will also turn off quickly. After Q7 turns on, after VCC is divided by R6 and R7, the base voltage of PNP transistor Q6 is lower than its emitter voltage, satisfying the conduction condition of PNP transistor Q6. After Q6 turns on, VCC, R9, and Q6 form a positive feedback loop, allowing Q7 to remain in the on state. Because Q6 is in the ON state, its collector voltage is close to VCC. After passing through R6 and Q5, the NPN transistor Q5 will also remain ON because the self-locking circuit formed by R7, R8, R9, Q6, and Q7 satisfies the bias conduction condition. The collector of Q5 will be pulled down to 0V, and Q1 will remain ON. This circuit forms a short-circuit protection circuit for a dimming LED driver with self-locking capability. Furthermore, due to the unidirectional biasing effect of D1, the voltage across the short-circuit self-locking circuit will not affect the voltage passing through D1, R3, and R5, ensuring the reliability of the short-circuit protection self-locking circuit.

[0039] Specifically, this solution features a simple and reliable circuit, a purely hardware-based design, and a short-circuit state that can be locked to ensure circuit reliability. Furthermore, it eliminates the need for software resources to handle short-circuit protection circuits, uses discrete components, requires very few materials, has low cost, occupies little PCB space, and is conducive to product integration.

Claims

1. A dimming LED driver short-circuit self-locking protection circuit for a small black box, characterized in that, include: The MOSFET driver circuit is used for chopper control to drive the power transistor MOSFET. The LED light string has its positive terminal connected to the power supply terminal and its negative terminal connected to the power transistor MOSFET. The LED light string is used to emit light. The power transistor MOSFET is electrically connected to the MOSFET driving circuit, the LED string, and the current detection circuit, respectively. The power transistor MOSFET is used to adjust the brightness of the LED string. The current detection circuit is electrically connected to the power transistor MOSFET and the short-circuit protection self-locking circuit, respectively. The current detection circuit is used to detect the current value flowing through the LED string. The short-circuit protection self-locking circuit is electrically connected to the MOSFET driving circuit, the power transistor MOSFET, and the current detection circuit. The short-circuit protection self-locking circuit is triggered when a short circuit occurs in the circuit of the LED string. The short-circuit protection self-locking circuit will shut down the MOSFET driving circuit and lock the short-circuit protection state.

2. The dimming LED driver short-circuit self-locking protection circuit according to claim 1, characterized in that, The MOSFET driving circuit includes: resistors R1, R2, R3, R4, and R5; transistors Q1 and Q2; wherein the PWM driver is connected to the base of transistor Q1 through one end of resistor R1; one end of resistor R2 is connected to one end of resistor R1 and the PWM driver; the other end of resistor R2 is pulled down to GND; the collector of transistor Q1 is connected to the base of transistor Q2 and one end of resistor R3; VCC is connected to the other end of resistor R3 to the emitter of transistor Q2; the emitter of transistor Q1 is connected to GND; and the collector of transistor Q2 is connected to resistor R4.

3. The dimming LED driver short-circuit self-locking protection circuit according to claim 2, characterized in that, The transistor Q1 is an NPN transistor.

4. The dimming LED driver short-circuit self-locking protection circuit according to claim 2, characterized in that, The transistor Q2 is a PNP transistor.

5. The dimming LED driver short-circuit self-locking protection circuit according to claim 2, characterized in that, The power transistor MOSFET is an N-type transistor Q3.

6. The dimming LED driver short-circuit self-locking protection circuit according to claim 5, characterized in that, The MOSFET driving circuit also includes a transistor Q4, wherein one end of the resistor R5 is connected to the base of the transistor Q4, and the other end of the resistor R4 is connected to the emitter of the transistor Q4 and the gate of the transistor Q3.

7. The dimming LED driver short-circuit self-locking protection circuit according to claim 6, characterized in that, The transistor Q4 is a PNP transistor.

8. The dimming LED driver short-circuit self-locking protection circuit according to claim 6, characterized in that, The short-circuit protection self-locking circuit includes: resistors R6, R7, R8, R9, R10, and R11; diode D1; capacitor C1; transistors Q5, Q6, and Q7. One end of resistor R10 is connected to resistor R11, and the other end of resistor R10 is connected to one end of capacitor C1 and the positive terminal of diode D1. The other end of capacitor C1 is connected to GND. The negative terminal of diode D1 is connected to one end of resistor R9 and the base of transistor Q7. The other end of resistor R9... The collector of transistor Q6 is connected to one end of resistor R6, the other end of resistor R6 is connected to the base of transistor Q5, the emitter of transistor Q5 is connected to GND, the collector of transistor Q5 is connected to the base of transistor Q1, the emitter of transistor Q6 is connected to VCC and one end of resistor R7, the other end of resistor R7 is connected to the base of transistor Q6 and one end of resistor R8, the other end of resistor R8 is connected to the collector of transistor Q7, and the emitter of transistor Q7 is connected to GND.

9. The dimming LED driver short-circuit self-locking protection circuit according to claim 8, characterized in that, The transistor Q6 is a PNP transistor.

10. The dimming LED driver short-circuit self-locking protection circuit according to claim 8, characterized in that, Transistor Q5 is an NPN transistor, and transistor Q7 is an NPN transistor.

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