LED constant-voltage power supply and dimming short-circuit protection circuit thereof

Abstract

The utility model discloses an LED constant voltage power supply and a dimming short circuit protection circuit thereof. The dimming short-circuit protection circuit comprises the voltage detection circuit and the current detection circuit, the voltage detection circuit can accurately and effectively carry out short-circuit detection and trigger protection when the dimming PWM duty ratio is small, and the current detection circuit can accurately and effectively carry out short-circuit detection and trigger protection when the dimming PWM duty ratio is large. Short-circuit detection and protection triggering are carried out in a voltage detection and current detection complementary mode, a dimming MOS tube can be triggered, protected and turned off as long as any one of the current detection circuit and the voltage detection circuit generates a low-level short-circuit signal, the technical effect of protecting the safety of a power supply and a load is achieved, 0-100% dimming or 0-100% dimming and color modulation can be achieved, and the dimming effect is good. The problem that an existing dimming short-circuit protection circuit cannot be suitable for a 0-100% PWM comprehensive dimming or dimming and color modulation LED constant-voltage power supply is solved.

Description

TECHNICAL FIELD

[0001] The utility model relates to lighting equipment technical field especially relates to a LED constant voltage power supply and its light modulation short circuit protection circuit. BACKGROUND

[0002] As Figure 1 , Figure 2 As shown in the existing output constant voltage type light modulation / light modulation color modulation power, generally sets up voltage detection circuit in power output end, judges whether load end is short-circuited through detecting power output end voltage, when load end is short-circuited, V- voltage rises, Vb voltage rises, triode Q2 conduction triggers protection circuit to shut off NMOS pipe Q1 and carries out short-circuit protection. This light modulation short circuit protection circuit that triggers protection through voltage detection, when light modulation PWM duty ratio is small (less than 80%), protection is timely accurate and effective, and when light modulation PWM duty ratio is big (greater than or equal to 80%), since NMOS pipe Q1 is in saturation conduction, short-circuit time will lower Vo, causes Vb to reach the threshold of triode Q2 conduction, cannot trigger protection circuit, cannot achieve short-circuit protection.

[0003] Summarized above, the existing light modulation short circuit protection circuit that triggers protection through voltage detection, cannot carry out effective short-circuit protection when light modulation PWM duty ratio is big, thereby cannot be applicable to 0-100% PWM overall light modulation or light modulation color modulation LED constant voltage power. SUMMARY

[0004] The utility model wants to solve the technical problem to provide a kind of LED constant voltage power supply and its light modulation short circuit protection circuit, to solve the problem that the existing light modulation short circuit protection circuit cannot be applicable to 0-100% PWM overall light modulation or light modulation color modulation LED constant voltage power.

[0005] To solve the above technical problem, the utility model adopts the technical scheme as follows:

[0006] The first aspect of this utility model provides a dimming short-circuit protection circuit applied to an LED constant voltage power supply. The output port of the LED constant voltage power supply is grounded through a dimming MOSFET and a current-limiting resistor connected in series. The dimming short-circuit protection circuit includes: a voltage detection circuit connected to the output port of the LED constant voltage power supply, used to detect the voltage at the output port of the LED constant voltage power supply and output a shutdown control signal when the voltage at the output port of the LED constant voltage power supply reaches a preset voltage value; a current detection circuit connected to the output port of the LED constant voltage power supply, used to detect the current at the output port of the LED constant voltage power supply and output a shutdown control signal when the current at the output port of the LED constant voltage power supply reaches a preset current value; and a PWM dimming driver, whose input terminals are respectively connected to the main controller of the LED constant voltage power supply, the output terminal of the voltage detection circuit, and the output terminal of the current detection circuit. The output terminal of the PWM dimming driver is connected to the control terminal of the dimming MOSFET, used to control the dimming MOSFET to turn off when receiving the shutdown control signal output by the voltage detection circuit or the current detection circuit.

[0007] Preferably, the main controller of the LED constant voltage power supply is connected to the output terminal of the voltage detection circuit and the output terminal of the current detection circuit respectively. When the main controller receives the shutdown control signal output by the voltage detection circuit or the current detection circuit, it outputs a control signal to shut down the output of the PWM dimming drive.

[0008] Preferably, the voltage detection circuit includes resistor R1, resistor R2, capacitor C1, transistor Q2, and a step-down unit. The input terminal of the step-down unit is connected to the output port of the LED constant voltage power supply. The output terminal of the step-down unit is grounded after passing through resistors R1 and R2 connected in series. Capacitor C1 is connected in parallel with resistor R2. The junction between resistors R1 and R2 is connected to the base of transistor Q2. The emitter of transistor Q2 is grounded. The collector of transistor Q2 is connected to the input terminal of the PWM dimming driver and the input terminal of the main controller, respectively.

[0009] Preferably, the step-down unit includes a diode D1, a Zener diode ZD1, and a Zener diode ZD2. The anode of diode D1 is connected to the output port of the LED constant voltage power supply, the cathode of diode D1 is connected to the negative terminal of Zener diode ZD1, the positive terminal of Zener diode ZD1 is connected to the negative terminal of Zener diode ZD2, and the positive terminal of Zener diode ZD2 is connected to resistor R1.

[0010] Preferably, a diode D3 is connected between the collector of the transistor Q2 and the input terminal of the main controller. The anode of the diode D3 is connected to the input terminal of the main controller, and the cathode of the diode D3 is connected to the collector of the transistor Q2.

[0011] Preferably, the current detection circuit includes a comparator U1 and a resistor R3. The positive input terminal of the comparator U1 is connected to a reference voltage source, and the negative input terminal of the comparator U1 is connected to the junction between the dimming MOS transistor and the current limiting resistor through the resistor R3. The output terminal of the comparator U1 is connected to the input terminal of the PWM dimming drive and the input terminal of the main controller, respectively.

[0012] The second aspect of this utility model provides a dimming short-circuit protection circuit applied to an LED constant voltage power supply. The LED constant voltage power supply includes several output ports, each output port being connected to one end of a current-limiting resistor via a dimming MOSFET, the other end of which is grounded. The dimming short-circuit protection circuit includes: a voltage detection circuit, connected to each output port of the LED constant voltage power supply, for detecting the voltage at each output port and outputting a shutdown control signal when the voltage at any output port reaches a preset voltage; and a current detection circuit, connected to the LED constant voltage power supply... Each output port of the power supply is used to detect the total current at each output port of the LED constant voltage power supply and output a shutdown control signal when the total current at each output port of the LED constant voltage power supply reaches a preset current value; the PWM dimming driver has its input terminal connected to the main controller of the LED constant voltage power supply, the output terminal of the voltage detection circuit, and the output terminal of the current detection circuit, respectively. The output terminal of the PWM dimming driver is connected to the control terminal of the dimming MOS transistor of each output, and is used to control the dimming MOS transistor of each output to turn off when the shutdown control signal output by the voltage detection circuit or the current detection circuit is received.

[0013] Preferably, the main controller of the LED constant voltage power supply is connected to the output terminal of the voltage detection circuit and the output terminal of the current detection circuit respectively. When the main controller receives the shutdown control signal output by the voltage detection circuit or the current detection circuit, it outputs a control signal to shut down the output of the PWM dimming drive.

[0014] Preferably, the voltage detection circuit includes resistors R1 and R2, capacitor C1, transistor Q2, and a step-down unit. The input terminal of the step-down unit is connected to each output port of the LED constant voltage power supply. The output terminal of the step-down unit is grounded after passing through resistors R1 and R2 in series. Capacitor C1 is connected in parallel with resistor R2. The junction between resistors R1 and R2 is connected to the base of transistor Q2. The emitter of transistor Q2 is grounded. The collector of transistor Q2 is connected to the input terminal of the PWM dimming driver and the input terminal of the main controller, respectively. The step-down unit includes several diodes, Zener diodes ZD1 and ZD2. The anode of each diode is connected to one output port of the LED constant voltage power supply. The cathode of each diode is connected to the negative terminal of Zener diode ZD1. The positive terminal of Zener diode ZD1 is connected to the negative terminal of Zener diode ZD2. The positive terminal of Zener diode ZD2 is connected to resistor R1.

[0015] The third aspect of this utility model provides an LED constant voltage power supply, which includes the dimming short-circuit protection circuit described above.

[0016] The aforementioned LED constant voltage power supply and its dimming short-circuit protection circuit include a voltage detection circuit and a current detection circuit. Short-circuit detection and protection are triggered through a complementary approach of voltage and current detection. If either the current detection circuit or the voltage detection circuit generates a low-level short-circuit signal, it can trigger the protection to shut down the dimming MOSFET, achieving the technical effect of protecting the power supply and load safety. It can realize 0-100% dimming or 0-100% dimming and color adjustment, solving the problem that existing dimming short-circuit protection circuits cannot be applied to LED constant voltage power supplies with 0-100% PWM full dimming or dimming and color adjustment. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the circuit structure of an LED constant voltage power supply that uses voltage detection for short-circuit protection in the prior art.

[0018] Figure 2 for Figure 1 The circuit diagram of the voltage detection circuit in the image;

[0019] Figure 3 This is a schematic diagram of the circuit structure of an LED constant voltage power supply in one embodiment of the present invention.

[0020] Figure 4 for Figure 3 The circuit diagrams of the current detection circuit and voltage detection circuit in the image;

[0021] Figure 5 This is a schematic diagram of the circuit structure of the LED constant voltage power supply in another embodiment of the present invention;

[0022] Figure 6 for Figure 5 The circuit diagrams for the current detection circuit and voltage detection circuit are shown. Detailed Implementation

[0023] To enable those skilled in the art to more clearly understand the purpose, technical solution and advantages of this utility model, the present utility model will be further described below in conjunction with the accompanying drawings and embodiments.

[0024] This utility model discloses an LED constant voltage power supply and its dimming short-circuit protection circuit. The dimming short-circuit protection circuit can protect the LED constant voltage power supply from short circuit when it is dimmed from 0-100% or dimmed and color-adjusted from 0-100%, so as to ensure that the power supply equipment is not damaged. It solves the problem that the existing dimming short-circuit protection circuit cannot be applied to LED constant voltage power supplies with full dimming or dimming and color-adjustment of 0-100% PWM.

[0025] like Figure 3 As shown, in one embodiment of this utility model, the LED constant voltage power supply includes an AC / DC converter, a constant voltage driver, a main controller, a PWM dimming driver, a dimming MOSFET, and a current-limiting resistor. The AC / DC converter converts AC mains power to DC power. The constant voltage driver outputs a constant voltage under the control of the main controller. Its output port, connected to the negative terminal of the load, is connected to the negative terminal of the constant voltage driver's output (the negative terminal of the constant voltage driver's output is grounded) via a dimming MOSFET and a current-limiting resistor connected in series. The main controller controls the PWM dimming driver to output PWM signals with different duty cycles. Under the control of the main controller, the PWM dimming driver outputs PWM signals with corresponding duty cycles to control the on / off state of the dimming MOSFET, thereby achieving dimming functionality. In this embodiment, the MCU is the main controller of the LED constant voltage power supply. The PWM dimming driver includes a driver IC that can output PWM signals with corresponding duty cycles under the control of the MCU. The NMOS transistor Q1 is a dimming MOSFET.

[0026] The LED constant voltage power supply also includes a dimming short-circuit protection circuit, which comprises a voltage detection circuit, a current detection circuit, and a PWM dimming driver. The voltage detection circuit is connected to the output port of the LED constant voltage power supply and detects the voltage at the output port, outputting a shutdown control signal when the voltage reaches a preset value. The current detection circuit is also connected to the output port and detects the current at the output port, outputting a shutdown control signal when the current reaches a preset value. The input terminal of the PWM dimming driver is connected to the output terminals of both the voltage and current detection circuits, and the output terminal is connected to the control terminal of the dimming MOSFET. Upon receiving the shutdown control signal from either the voltage or current detection circuit, the driver controls the dimming MOSFET to turn off, thus achieving short-circuit protection.

[0027] The main controller of the LED constant voltage power supply is also connected to the output terminal of the voltage detection circuit and the output terminal of the current detection circuit. When the main controller receives the shutdown control signal output by the voltage detection circuit or the current detection circuit, it outputs a control signal to shut down the output of the PWM dimming drive.

[0028] like Figure 4 As shown, the voltage detection circuit includes resistor R1, resistor R2, capacitor C1, transistor Q2, and a step-down unit. The input terminal of the step-down unit is connected to the output port V- of the LED constant voltage power supply. The output terminal of the step-down unit is grounded through resistors R1 and R2 connected in series. Capacitor C1 is connected in parallel with resistor R2. The junction between resistors R1 and R2 is connected to the base of transistor Q2. The emitter of transistor Q2 is grounded. The collector of transistor Q2 is connected to the input terminal of the PWM dimming driver (the enable terminal EN of the driver IC) and the input terminal of the main controller (the detection pin ER of the MCU).

[0029] The step-down unit includes diode D1, Zener diode ZD1, and Zener diode ZD2. The anode of diode D1 is connected to the output port V- of the LED constant voltage power supply, the cathode of diode D1 is connected to the negative terminal of Zener diode ZD1, the anode of Zener diode ZD1 is connected to the negative terminal of Zener diode ZD2, and the anode of Zener diode ZD2 is connected to resistor R1. A diode D3 is connected between the collector of transistor Q2 and the input terminal of the main controller. The anode of diode D3 is connected to the input terminal of the main controller, and the cathode of diode D3 is connected to the collector of transistor Q2. In other embodiments, the specific circuit structure of the step-down unit can be adjusted according to actual conditions, such as adding or removing a Zener diode.

[0030] The current detection circuit includes a comparator U1 and a resistor R3. The positive input terminal of the comparator U1 is connected to a reference voltage source, and the negative input terminal of the comparator U1 is connected to the junction between the dimming MOS transistor and the current limiting resistor through the resistor R3. The output terminal of the comparator U1 is connected to the input terminal of the PWM dimming driver and the input terminal of the main controller, respectively.

[0031] In this embodiment, the dimming short-circuit protection circuit uses a combination of current detection circuit and voltage detection circuit to perform short-circuit detection, thereby achieving the short-circuit protection function. The specific working principle is as follows:

[0032] (1) In the current detection circuit:

[0033] Comparator U1 forms a voltage comparator. Its positive input is connected to an external reference voltage source, which sets the reference voltage Vref. The negative input voltage Vad is connected to ground via resistor R3 and a current-limiting resistor RS. Vad is the voltage value converted from the current Io through the current-limiting resistor RS (Vad = Io * RS). The larger the current Io, the larger Vad. During normal operation, when Vref is greater than Vad, the output voltage Vs1 (Vs1 is approximately equal to VCC) of comparator U1 remains high. The Vs voltage is clamped by diode D3, also resulting in a high level. PNP transistor Q2 is cut off, and Vs and Vs1 are both high. The MCU does not detect a low-level short-circuit signal in Vs, and the enable pin EN of the driver IC is high. Both the MCU and the driver IC output PWM normally, and the load operates normally. When a short circuit occurs, the output current Io increases instantaneously, Vad increases until Vad is greater than Vref, the output voltage Vs1 of comparator U1 flips and outputs a low level, Vs1 pulls Vs low through D3; the MCU detects the low-level short-circuit signal of Vs, the enable terminal EN of the driver IC is low, the MCU and the driver IC simultaneously turn off the output PWM, and the current load stops working.

[0034] (2) In the voltage detection circuit:

[0035] Since V- = (V+) - Vled and Vb = {(V-) - (Vf + Vz1 + Vz2)} * R2 / (R1 + R2), V+ is stepped down by the load LED, diode D1, Zener diode ZD1, and Zener diode ZD2, and then divided by resistors R1 and R2 to obtain Vb, which drives NPN transistor Q2 to conduct, generating a low-level short-circuit signal for the MCU and driver IC. During normal operation, Vb < 0.7V, transistor Q2 is cut off, Vs and Vs1 are high, the MCU does not detect the low-level short-circuit signal of Vs, the enable pin EN of the driver IC is high, and both the MCU and driver IC output PWM normally, and the load operates normally. At the moment of short circuit, (V-) = (V+), Vb rises rapidly, and Vb charges capacitor C1. When Vb > 0.7V, NPN transistor Q2 turns on, pulling Vs1 and Vs low. The MCU detects the low-level short circuit signal of Vs, and the enable pin EN of the driver IC goes low. The MCU and the driver IC simultaneously turn off the output PWM, and the current load stops working.

[0036] The dimming short-circuit protection circuit in this embodiment includes a voltage detection circuit and a current detection circuit. The voltage detection circuit can accurately and effectively detect short circuits and trigger protection when the dimming PWM duty cycle is small (less than 80%). The current detection circuit can accurately and effectively detect short circuits and trigger protection when the dimming PWM duty cycle is large (greater than or equal to 80%). Short circuit detection and protection are triggered by the complementary approach of voltage and current detection. As long as either the current detection circuit or the voltage detection circuit generates a low-level short-circuit signal, it can trigger the protection to shut down the dimming MOSFET, achieving the technical effect of protecting the power supply and load safety. It can realize 0-100% dimming or 0-100% dimming and color adjustment, solving the problem that existing dimming short-circuit protection circuits cannot be applied to LED constant voltage power supplies with full dimming or dimming and color adjustment of 0-100% PWM.

[0037] like Figure 5 , Figure 6As shown, in another embodiment of this utility model, the LED constant voltage power supply includes an AC / DC converter, a constant voltage driver, a main controller, a PWM dimming driver, several dimming MOSFETs, and a current-limiting resistor. The AC / DC converter is used to convert AC mains power into DC power. The constant voltage driver is used to output a constant voltage under the control of the main controller. The LED constant voltage power supply includes several output ports. Each output port is connected to one end of the current-limiting resistor through a dimming MOSFET. The other end of the current-limiting resistor is connected to the negative terminal of the output of the constant voltage driver (the negative terminal of the output of the constant voltage driver is grounded). The main controller controls the PWM dimming driver to output several PWM signals, correspondingly controlling the conduction and cutoff of the dimming MOSFET of each output, thereby realizing multi-channel dimming function. In this embodiment, the MCU is the main controller of the LED constant voltage power supply. The PWM dimming driver includes a driver IC, which can output several PWM signals under the control of the MCU. V-, V1-, ..., Vn- are several output ports of the LED constant voltage power supply. NMOS transistors Q1, Q1-1, ..., Q1-n are several dimming MOS transistors corresponding to V-, V1-, ..., Vn-.

[0038] The dimming short-circuit protection circuit of the LED constant voltage power supply in this embodiment includes a voltage detection circuit, a current detection circuit, and a PWM dimming driver. The voltage detection circuit is connected to each output port of the LED constant voltage power supply to detect the voltage at each output port and outputs a shutdown control signal when the voltage at any output port reaches a preset voltage. The current detection circuit is connected to each output port of the LED constant voltage power supply to detect the total current at each output port and outputs a shutdown control signal when the total current at each output port reaches a preset current value. The input terminal of the PWM dimming driver is connected to the output terminals of the voltage detection circuit and the current detection circuit, respectively. The output terminal of the PWM dimming driver is connected to the control terminal of each output dimming MOS transistor, respectively, to control each output dimming MOS transistor to turn off when the shutdown control signal output by the voltage detection circuit or the current detection circuit is received.

[0039] The main controller of the LED constant voltage power supply is connected to the output terminal of the voltage detection circuit and the output terminal of the current detection circuit respectively. When the main controller receives the shutdown control signal output by the voltage detection circuit or the current detection circuit, it outputs a control signal to shut down the output of the PWM dimming drive.

[0040] The voltage detection circuit includes resistors R1 and R2, capacitor C1, transistor Q2, and a step-down unit. The input of the step-down unit is connected to each output port of the LED constant voltage power supply. The output of the step-down unit is grounded through resistors R1 and R2 connected in series. Capacitor C1 is connected in parallel with resistor R2. The junction between resistors R1 and R2 is connected to the base of transistor Q2. The emitter of transistor Q2 is grounded. The collector of transistor Q2 is connected to the input of the PWM dimming driver (enable terminal of the driver IC) and the input of the main controller (detection pin ER of the MCU).

[0041] The step-down unit includes several diodes, a Zener diode ZD1, and a Zener diode ZD2. The anode of each diode is connected to one output port of the LED constant voltage power supply, and the cathode of each diode is connected to the negative terminal of Zener diode ZD1. The anode of Zener diode ZD1 is connected to the negative terminal of Zener diode ZD2, and the anode of Zener diode ZD2 is connected to resistor R1. A diode D3 is connected between the collector of transistor Q2 and the input terminal of the main controller. The anode of diode D3 is connected to the input terminal of the main controller, and the cathode of diode D3 is connected to the collector of transistor Q2.

[0042] The current detection circuit includes a comparator U1 and a resistor R3. The positive input terminal of the comparator U1 is connected to a reference voltage source, and the negative input terminal of the comparator U1 is connected to the junction between several dimming MOS transistors and current limiting resistors through the resistor R3. The output terminal of the comparator U1 is connected to the input terminal of the PWM dimming driver and the input terminal of the main controller, respectively.

[0043] In this embodiment, the dimming short-circuit protection circuit uses a combination of current detection and voltage detection circuits to perform short-circuit detection, thereby achieving short-circuit protection. For details on its working principle, please refer to [reference needed]. Figure 3 , Figure 4 The working principle of the dimming short-circuit protection circuit in the illustrated embodiment will not be described in detail here.

[0044] The dimming short-circuit protection circuit in this embodiment includes a voltage detection circuit and a current detection circuit. The voltage detection circuit can accurately and effectively detect short circuits and trigger protection when the dimming PWM duty cycle is small (less than 80%). The current detection circuit can accurately and effectively detect short circuits and trigger protection when the dimming PWM duty cycle is large (greater than or equal to 80%). Short circuit detection and protection are triggered by the complementary use of voltage and current detection. If either the current detection circuit or the voltage detection circuit generates a low-level short-circuit signal, it can trigger the protection to shut down the dimming MOSFET, achieving the technical effect of protecting the power supply and load safety. It can realize multi-channel output 0-100% dimming or 0-100% dimming and color adjustment, solving the problem that existing dimming short-circuit protection circuits cannot be applied to LED constant voltage power supplies with 0-100% PWM full dimming or dimming and color adjustment.

[0045] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Those skilled in the art can make various equivalent changes and improvements based on the above embodiments. All equivalent changes or modifications made within the scope of the claims should fall within the protection scope of the present utility model.

Claims

1. A dimming short-circuit protection circuit, applied to an LED constant voltage power supply, wherein the output port of the LED constant voltage power supply is grounded through a dimming MOSFET and a current-limiting resistor connected in series, characterized in that... include: A voltage detection circuit is connected to the output port of the LED constant voltage power supply. It is used to detect the voltage at the output port of the LED constant voltage power supply and output a shutdown control signal when the voltage at the output port of the LED constant voltage power supply reaches the preset voltage value. The current detection circuit is connected to the output port of the LED constant voltage power supply. It is used to detect the current at the output port of the LED constant voltage power supply and output a shutdown control signal when the current at the output port of the LED constant voltage power supply reaches the preset current value. The input terminals of the PWM dimming driver are connected to the main controller of the LED constant voltage power supply, the output terminal of the voltage detection circuit, and the output terminal of the current detection circuit, respectively. The output terminal of the PWM dimming driver is connected to the control terminal of the dimming MOSFET, and is used to control the dimming MOSFET to turn off when the turn-off control signal output by the voltage detection circuit or the current detection circuit is received.

2. The dimming short-circuit protection circuit as described in claim 1, characterized in that, The main controller of the LED constant voltage power supply is connected to the output terminal of the voltage detection circuit and the output terminal of the current detection circuit respectively. When the main controller receives the shutdown control signal output by the voltage detection circuit or the current detection circuit, it outputs a control signal to shut down the output of the PWM dimming drive.

3. The dimming short-circuit protection circuit as described in claim 2, characterized in that, The voltage detection circuit includes resistors R1 and R2, capacitor C1, transistor Q2, and a step-down unit. The input of the step-down unit is connected to the output port of the LED constant voltage power supply. The output of the step-down unit is grounded through resistors R1 and R2 connected in series. Capacitor C1 is connected in parallel with resistor R2. The junction between resistors R1 and R2 is connected to the base of transistor Q2. The emitter of transistor Q2 is grounded. The collector of transistor Q2 is connected to the input of the PWM dimming driver and the input of the main controller, respectively.

4. The dimming short-circuit protection circuit as described in claim 3, characterized in that, The step-down unit includes diode D1, Zener diode ZD1, and Zener diode ZD2. The anode of diode D1 is connected to the output port of the LED constant voltage power supply, the cathode of diode D1 is connected to the negative terminal of Zener diode ZD1, the positive terminal of Zener diode ZD1 is connected to the negative terminal of Zener diode ZD2, and the positive terminal of Zener diode ZD2 is connected to resistor R1.

5. The dimming short-circuit protection circuit as described in claim 3 or 4, characterized in that, A diode D3 is connected between the collector of transistor Q2 and the input terminal of the main controller. The anode of diode D3 is connected to the input terminal of the main controller, and the cathode of diode D3 is connected to the collector of transistor Q2.

6. The dimming short-circuit protection circuit as described in claim 2, characterized in that, The current detection circuit includes a comparator U1 and a resistor R3. The positive input terminal of the comparator U1 is connected to a reference voltage source, and the negative input terminal of the comparator U1 is connected to the junction between the dimming MOS transistor and the current limiting resistor through the resistor R3. The output terminal of the comparator U1 is connected to the input terminal of the PWM dimming driver and the input terminal of the main controller, respectively.

7. A dimming short-circuit protection circuit, applied to an LED constant voltage power supply, the LED constant voltage power supply including several output ports, each output port being connected to one end of a current-limiting resistor through a dimming MOSFET, the other end of the current-limiting resistor being grounded, characterized in that, include: The voltage detection circuit is connected to each output port of the LED constant voltage power supply. It is used to detect the voltage at each output port of the LED constant voltage power supply and output a shutdown control signal when the voltage at any output port of the LED constant voltage power supply reaches the preset voltage. The current detection circuit is connected to each output port of the LED constant voltage power supply. It is used to detect the total current at each output port of the LED constant voltage power supply and output a shutdown control signal when the total current at each output port of the LED constant voltage power supply reaches the preset current value. The input terminals of the PWM dimming driver are connected to the main controller of the LED constant voltage power supply, the output terminal of the voltage detection circuit, and the output terminal of the current detection circuit, respectively. The output terminal of the PWM dimming driver is connected to the control terminal of each output dimming MOS transistor, and is used to control each output dimming MOS transistor to turn off when the voltage detection circuit or the current detection circuit outputs a turn-off control signal.

8. The dimming short-circuit protection circuit as described in claim 7, characterized in that, The main controller of the LED constant voltage power supply is connected to the output terminal of the voltage detection circuit and the output terminal of the current detection circuit respectively. When the main controller receives the shutdown control signal output by the voltage detection circuit or the current detection circuit, it outputs a control signal to shut down the output of the PWM dimming drive.

9. The dimming short-circuit protection circuit as described in claim 8, characterized in that, The voltage detection circuit includes resistors R1 and R2, capacitor C1, transistor Q2, and a step-down unit. The input of the step-down unit is connected to each output port of the LED constant voltage power supply. The output of the step-down unit is grounded after passing through resistors R1 and R2 in series. Capacitor C1 is connected in parallel with resistor R2. The junction between resistors R1 and R2 is connected to the base of transistor Q2. The emitter of transistor Q2 is grounded. The collector of transistor Q2 is connected to the input of the PWM dimming driver and the input of the main controller, respectively. The step-down unit includes several diodes, Zener diodes ZD1 and ZD2. The anode of each diode is connected to one output port of the LED constant voltage power supply. The cathode of each diode is connected to the negative terminal of Zener diode ZD1. The positive terminal of Zener diode ZD1 is connected to the negative terminal of Zener diode ZD2. The positive terminal of Zener diode ZD2 is connected to resistor R1.

10. An LED constant voltage power supply, characterized in that, Includes the dimming short-circuit protection circuit as described in any one of claims 1-9.

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