LED light mixing circuit

Abstract

An LED light mixing circuit comprises three power supply input ends, a diagnosis end, three LED lamp bead driving circuits and a diagnosis circuit. Each path of LED lamp bead driving circuit comprises an LED lamp bead and a triode constant current circuit, and a first input end and a second input end of the triode constant current circuit are respectively connected with an anode and a cathode of the LED lamp bead; the three power supply input ends are respectively connected with the common connection points of the anodes of the three paths of LED lamp beads and the first input end of the triode constant current circuit; the diagnosis circuit comprises a resistor R5, a resistor R11, a resistor R17 and a resistor R19; the first ends of the resistors R5, R11 and R17 are respectively connected with the common connection point of the cathodes of the three paths of LED lamp beads and the second input end of the triode constant current circuit, the first end of the resistor R19 is respectively connected with the second ends of the resistors R5, R11 and R17, and the second end of the resistor R19 is grounded. According to the utility model, diagnosis of open circuit and short circuit of one path of LED lamp bead of the LED light mixing circuit can be realized under the condition that one path of diagnosis line is used.

Description

Technical Field

[0001] The utility model relates to a control circuit of an LED lamp and a fault diagnosis method thereof. Background Art

[0002] At present, for the vehicle ambient light control circuit without MCU chip, the front end only provides three power lines, one diagnostic line and LIN communication line. To realize the functions of driving RGB lamp beads to emit light and diagnosing open circuit and short circuit faults, the above hardware environment must be met, which puts higher requirements on circuit design. Summary of the invention

[0003] The technical problem to be solved by the utility model is to provide an LED mixing circuit. By adopting the LED mixing circuit, the open circuit fault and short circuit fault of any LED lamp bead in the LED mixing circuit can be diagnosed by using one diagnostic line, and the circuit structure is simple.

[0004] Another technical problem to be solved by the utility model is to provide an LED light mixing circuit with an overvoltage protection function.

[0005] An LED light mixing circuit of an embodiment of the utility model comprises three power input terminals, a diagnostic terminal, three-way LED lamp bead driving circuit and a diagnostic circuit; each LED lamp bead driving circuit comprises an LED lamp bead and a triode constant current circuit, and the LED lamp bead is grounded via the triode constant current circuit; the first input terminal and the second input terminal of the triode constant current circuit of each LED lamp bead driving circuit are respectively connected to the anode and the cathode of the LED lamp bead of the LED lamp bead driving circuit; the three power input terminals are respectively connected to the common connection point of the anode of the LED lamp bead of the three-way LED lamp bead driving circuit and the first input terminal of the triode constant current circuit; the diagnostic circuit comprises a resistor R5, a resistor R11, a resistor R17 and a resistor R19; the resistor R The first end of resistor R5 is connected to the common point of the cathode of the LED lamp bead of the first LED lamp bead driving circuit and the second input end of the triode constant current circuit, the first end of resistor R11 is connected to the common point of the cathode of the LED lamp bead of the second LED lamp bead driving circuit and the second input end of the triode constant current circuit, the first end of resistor R17 is connected to the common point of the cathode of the LED lamp bead of the third LED lamp bead driving circuit and the second input end of the triode constant current circuit; the first end of resistor R19 is respectively connected to the second end of resistor R5, the second end of resistor R11 and the second end of resistor R17, and the second end of resistor R19 is grounded; the diagnostic end is connected to the common point of resistor R5, resistor R11, resistor R17 and resistor R19.

[0006] In the above-mentioned LED mixing circuit, the transistor constant current circuit includes a first NPN transistor, a second NPN transistor, a first resistor and a second resistor; the first end of the first resistor constitutes a first input end of the transistor constant current circuit, the second end of the first resistor is respectively connected to the collector of the first NPN transistor and the base of the second NPN transistor, and the emitter of the first NPN transistor is grounded; the collector of the second NPN transistor constitutes a second input end of the transistor constant current circuit, the emitter of the second NPN transistor is respectively connected to the base of the first NPN transistor and the first end of the second resistor, and the second end of the second resistor is grounded.

[0007] In the above-mentioned LED mixing light circuit, each LED lamp bead driving circuit includes an overvoltage protection circuit, and the overvoltage protection circuit includes an overvoltage conduction branch, a current limiting resistor and a switch tube; the first end of the overvoltage conduction branch is respectively connected to the power input end of the LED lamp bead driving circuit, the anode of the LED lamp bead, the first end of the first resistor and the first end of the current limiting resistor, the second end of the overvoltage conduction branch is grounded, and the output end of the overvoltage conduction branch is connected to the controlled end of the switch tube; the first conduction end of the switch tube is respectively connected to the second end of the current limiting resistor, the first resistor The second end of the switch tube, the collector of the first NPN transistor and the base of the second NPN transistor are connected, and the second conduction end of the switch tube is grounded; the overvoltage conduction branch is used to disconnect from the ground when the input voltage of the power input end does not reach the preset protection voltage threshold so that the switch tube is turned off, and is connected to the ground when the input voltage of the power input end reaches or exceeds the preset protection voltage threshold, divides the input voltage, and outputs it to the switch tube to turn on the switch tube, and controls the first NPN transistor and the second NPN transistor to be disconnected when the switch tube is turned on.

[0008] The utility model has at least the following advantages:

[0009] 1. The LED mixing circuit of the embodiment of the utility model utilizes the principle of power superposition, and can diagnose the open circuit fault and short circuit fault of any LED lamp bead in the LED mixing circuit according to the change of a voltage signal, and the circuit structure is simple;

[0010] 2. The LED mixing circuit of the embodiment of the utility model is provided with an overvoltage protection circuit, which can control the transistor constant current circuit to stop working when the voltage at the power input terminal reaches or exceeds the preset protection voltage threshold, thereby achieving the purpose of overvoltage protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 The circuit schematic diagram of the LED light mixing circuit according to an embodiment of the utility model is shown. DETAILED DESCRIPTION

[0012] The utility model is described in detail below with reference to the accompanying drawings and specific embodiments.

[0013] Figure 1 FIG. 1 shows a circuit schematic diagram of an LED light mixing circuit according to an embodiment of the present invention. Figure 1 According to an embodiment of the utility model, an LED light mixing circuit includes three power input terminals PWM_RED, PWM_GREEN, and PWM_BLUE, a diagnosis terminal ADC, a three-way LED lamp bead driving circuit 1 and a diagnosis circuit 2.

[0014] Each LED lamp bead driving circuit 1 includes an LED lamp bead 11 and a triode constant current circuit 12, and the LED lamp bead 11 is grounded through the triode constant current circuit 12. The first input terminal and the second input terminal of the triode constant current circuit of each LED lamp bead driving circuit 1 are respectively connected to the anode and cathode of the LED lamp bead 11 of the LED lamp bead driving circuit; the three power input terminals PWM_RED, PWM_GREEN, and PWM_BLUE are respectively connected to the common connection point of the anode of the LED lamp bead 11 of the three LED lamp bead driving circuits and the first input terminal of the triode constant current circuit 12.

[0015] Furthermore, each LED lamp bead driving circuit includes an anti-reverse element 13 and a filter capacitor 14. The anti-reverse element 13 is connected in series between the power input terminal and the anode of the LED lamp bead 11. One end of the filter capacitor 14 is connected to the anode of the LED lamp bead 11, and the other end of the filter capacitor 14 is grounded. In this embodiment, the anti-reverse element 13 is a diode. In other embodiments, the anti-reverse element 13 can also be a MOS tube or other device.

[0016] In this embodiment, the LED mixing circuit is an RGB three-primary color mixing circuit, and the LED lamp beads 11 of the three-way LED lamp bead driving circuit respectively connected to the three power input terminals PWM_RED, PWM_GREEN, and PWM_BLUE are red LED lamp beads, green LED lamp beads, and blue LED lamp beads.

[0017] In a specific application, the red LED lamp beads, green LED lamp beads and blue LED lamp beads are lamp beads of vehicle atmosphere lights, and the three power input terminals PWM_RED, PWM_GREEN, and PWM_BLUE are used to receive PWM control signals sent by the domain controller.

[0018] The diagnostic circuit 2 includes a resistor R5, a resistor R11, a resistor R17 and a resistor R19; the first end of the resistor R5 is connected to the common point of the cathode of the LED lamp bead of the first LED lamp bead driving circuit and the second input end of the triode constant current circuit, the first end of the resistor R11 is connected to the common point of the cathode of the LED lamp bead of the second LED lamp bead driving circuit and the second input end of the triode constant current circuit, the first end of the resistor R17 is connected to the common point of the cathode of the LED lamp bead of the third LED lamp bead driving circuit and the second input end of the triode constant current circuit; the first end of the resistor R19 is respectively connected to the second end of the resistor R5, the second end of the resistor R11 and the second end of the resistor R17, and the second end of the resistor R19 is grounded. Preferably, the resistance values ​​of the resistors R5, R11 and R17 are the same.

[0019] The diagnostic terminal ADC is connected to the common point of the resistor R5, the resistor R11, the resistor R17 and the resistor R19. The output signal of the diagnostic terminal ADC is collected by the controller, and the controller determines whether the LED mixing circuit fails.

[0020] The structure and principle of the three-way LED lamp bead driving circuit 1 are the same. For the sake of simplicity, the following only takes the first way LED lamp bead driving circuit with red LED lamp beads as an example to illustrate the structure and working principle of the LED lamp bead driving circuit.

[0021] The transistor constant current circuit 12 includes a first NPN transistor Q1, a second NPN transistor Q2, a first resistor R1, and a second resistor R2. The first end of the first resistor R1 constitutes a first input end of the transistor constant current circuit, the second end of the first resistor R1 is respectively connected to the collector of the first NPN transistor Q1 and the base of the second NPN transistor Q2, and the emitter of the first NPN transistor Q1 is grounded. The collector of the second NPN transistor Q2 constitutes a second input end of the transistor constant current circuit, the emitter of the second NPN transistor Q2 is respectively connected to the base of the first NPN transistor Q1 and the first end of the second resistor R2, and the second end of the second resistor R2 is grounded.

[0022] Furthermore, the LED lamp bead driving circuit includes an overvoltage protection circuit 15, and the overvoltage protection circuit 15 includes an overvoltage conduction branch, a current limiting resistor R4 and a switch tube Q3.

[0023] The first end of the overvoltage conduction branch is respectively connected to the power input end of the LED lamp bead driving circuit, the anode of the LED lamp bead 11, the first end of the first resistor R1 and the first end of the current limiting resistor R4, the second end of the overvoltage conduction branch is grounded, and the output end of the overvoltage conduction branch is connected to the controlled end of the switch tube Q3. In this embodiment, the overvoltage conduction branch includes a first voltage-dividing resistor R3, a second voltage-dividing resistor R6 and a voltage-stabilizing diode D2. The first end of the first voltage-dividing resistor R3 constitutes the first end of the overvoltage conduction branch, the second end of the first voltage-dividing resistor R3 is connected to the cathode of the voltage-stabilizing diode D2, the anode of the voltage-stabilizing diode D2 is connected to the first end of the second voltage-dividing resistor R6, the second end of the second voltage-dividing resistor R6 constitutes the second end of the overvoltage conduction branch, and the common connection point of the anode of the voltage-stabilizing diode and the first end of the second voltage-dividing resistor constitutes the output end of the overvoltage conduction branch.

[0024] The first conduction end of the switch tube Q3 is respectively connected to the second end of the current limiting resistor R4, the second end of the first resistor R1, the collector of the first NPN transistor Q1 and the base of the second NPN transistor Q2, and the second conduction end of the switch tube Q3 is grounded. The switch tube Q3 is composed of a third NPN transistor, and the base, collector and emitter of the third NPN transistor Q3 respectively constitute the controlled end, the first conduction end and the second conduction end of the switch tube Q3.

[0025] The overvoltage conduction branch is used to disconnect from the ground when the input voltage at the power input end does not reach the preset protection voltage threshold so that the switch tube Q3 is turned off. When the input voltage at the power input end reaches or exceeds the preset protection voltage threshold, it is connected to the ground, the input voltage is divided, and output to the switch tube Q3 to turn on the switch tube Q3. When the switch tube Q3 is turned on, it controls the first NPN transistor Q1 and the second NPN transistor Q2 to be disconnected.

[0026] For the second LED lamp bead driving circuit provided with the green LED lamp bead GREEN, the transistor constant current circuit 12 includes a first NPN transistor Q4, a second NPN transistor Q5, a first resistor R7 and a second resistor R8. The overvoltage protection circuit 15 includes an overvoltage conduction branch, a current limiting resistor R10 and a switch tube Q6. The overvoltage conduction branch includes a first voltage dividing resistor R9, a second voltage dividing resistor R12 and a voltage stabilizing diode D4.

[0027] For the third LED lamp bead driving circuit provided with a blue LED lamp bead BLUE, the transistor constant current circuit 12 includes a first NPN transistor Q7, a second NPN transistor Q8, a first resistor R13 and a second resistor R14. The overvoltage protection circuit 15 includes an overvoltage conduction branch, a current limiting resistor R16 and a switch tube Q9. The overvoltage conduction branch includes a first voltage dividing resistor R15, a second voltage dividing resistor R18 and a voltage stabilizing diode D6.

[0028] The following takes the first LED lamp bead driving circuit with red LED lamp beads as an example to illustrate the fault diagnosis principle of the LED mixing circuit with overvoltage protection.

[0029] The PWM input signal supplies power to the subsequent stage through the anti-reverse diode D1. When the power supply voltage is greater than the preset protection voltage threshold (the protection voltage threshold, i.e., the overvoltage value, can be set by selecting the parameters of the voltage-stabilizing diode D2, the first voltage-dividing resistor R3, and the second voltage-dividing resistor R6), current will flow through the base of the third NPN transistor Q3. At this time, the third NPN transistor Q3 is turned on, and the collector voltage of the third NPN transistor Q3 will be pulled down, thereby causing the emitter voltage of the first NPN transistor Q1 to be pulled down, and the first NPN transistor Q1 and the second NPN transistor Q2 are both disconnected, and the transistor constant current circuit 12 cannot work normally.

[0030] The current flowing through the red LED lamp bead RED is mainly determined by the Vbe conduction voltage drop of the first NPN transistor Q1 and the resistance value of the second resistor R2, that is, the current flowing through the red LED lamp bead 11 is approximately Vbe / R2; the transistor constant current circuit requires the emitter voltage of the first NPN transistor Q1 to be high in order to play a constant current role. After the overvoltage protection, the emitter voltage of the first NPN transistor Q1 is pulled down and cannot work.

[0031] The cathode of the red LED bead RED is connected to resistor R5, the cathode of the green LED bead GREEN is connected to resistor R11, and the cathode of the blue LED bead BLUE is connected to resistor R17. After these three resistors are connected in parallel, they are divided by resistor R19, and the voltage division point is sent to the ADC port of the controller as an analog signal to determine open or short circuit.

[0032] When working normally, the three resistors can be regarded as three power supplies, the cathode voltage of the red LED bead RED is used as the voltage source u1, the cathode voltage of the green LED bead GREEN is used as the voltage source u2, and the cathode voltage of the blue LED bead BLUE is used as the voltage source u3; the resistance values ​​of resistors R5, R11, R17 and R19 are r5, r11, r17 and r19 respectively, and the output voltage Vadc of the diagnostic end ADC can be obtained by the power supply superposition principle:

[0033] Normal operation:

[0034]

[0035] Take the short circuit of the red LED lamp bead RED as an example:

[0036] When the red LED lamp bead RED is short-circuited, the size of u1 changes compared to when the LED lamp bead is normal, and the difference is the voltage drop of an LED lamp bead. The change in Vadc voltage can be calculated by the above formula.

[0037] When the red LED lamp bead RED is open, it is equivalent to having only two voltage sources. At this time, Vadc is:

[0038]

[0039] It can be seen from the above formula that the voltage of Vadc will change significantly when the LED is in normal operation and when it is open or short-circuited. In this way, the controller connected to the diagnostic end ADC can easily implement the open-short circuit diagnosis function according to the voltage of Vadc.

[0040] The following describes a method for fault diagnosis using an LED light mixing circuit according to an embodiment of the present invention, comprising the following steps:

[0041] Calibration operation: When the LED mixing circuit is in a normal state (i.e., no fault), the controller collects an output voltage from the diagnostic terminal of the LED mixing circuit as the calibration voltage V 标 , and record the ambient temperature T during collection 标定 , as the calibration temperature of the controller;

[0042] Fault diagnosis: The controller collects the output voltage Vadc of the diagnostic terminal ADC of the LED mixing circuit in real time. If Vadc is greater than k1*(Temp-T 标定 )+V 标 +ΔV1, it is judged that there is a short circuit fault in one LED lamp bead in the LED mixing circuit; if Vadc is less than k21*(Temp-T 标定 )+V 标 -ΔV21, k22*(Temp-T 标定 )+V 标 -ΔV22, k23*(Temp-T 标定 )+V 标 -ΔV23, it is determined that there is an open circuit fault in one LED lamp bead in the LED mixing circuit.

[0043] Wherein, Temp is the temperature detected in real time; k1 is the slope of the output voltage value of the diagnostic terminal when one of the LED lamp beads in the LED mixing circuit is short-circuited, which is pre-stored by the controller, and ΔV1 is the theoretical output voltage V of the diagnostic terminal when one of the LED lamp beads is short-circuited. 短 With the calibration voltage V 标 The difference between the two is the theoretical diagnostic terminal output voltage V when one of the LED lamp beads is short-circuited. 短 It refers to the theoretical value of the output voltage Vadc of the diagnostic terminal ADC when one of the LED lamp beads in the LED mixing circuit is short-circuited. V 短 The calculation formula is as follows:

[0044]

[0045] Wherein, u1, u2 and u3 are the cathode voltages of the LED lamp beads in the three-way LED lamp bead driving circuit respectively; r5, r11, r17 and r19 are the resistance values ​​of resistors R5, R11, R17 and R19 respectively.

[0046] In this embodiment, k1 is obtained by querying the technical manual. One of the above-mentioned LED lamp beads can be pre-designated as any one of the three LED lamp beads. In other embodiments, k1 is obtained by a short-circuit calibration step, which includes artificially short-circuiting one of the LED lamp beads (for example, connecting a wire in parallel between the anode and cathode of the LED lamp bead), collecting the output voltage of the diagnostic terminal at multiple different temperatures, and performing linear fitting on the multiple temperatures and the collected multiple output voltages to obtain k1.

[0047] k21 is the slope of the output voltage value of the diagnostic terminal when the first LED lamp bead of the LED mixing circuit is open-circuited, which is pre-stored by the controller, and ΔV21 is the calibration voltage V 标 The theoretical diagnostic terminal output voltage V when the first LED lamp bead is open 开1 k22 is the slope of the output voltage value of the diagnostic terminal when the second LED lamp bead of the LED mixing circuit is open-circuited, which is pre-stored by the controller, and ΔV22 is the calibration voltage V 标 The theoretical diagnostic terminal output voltage V when the second LED lamp bead is open 开2 k23 is the slope of the output voltage value of the diagnostic terminal when the third LED lamp bead of the LED mixing circuit is open-circuited, which is pre-stored by the controller, and ΔV22 is the calibration voltage V 标 The theoretical diagnostic terminal output voltage V when the third LED lamp bead is open 开3 The theoretical diagnostic terminal output voltage V when the nth (n=1, 2 or 3) LED lamp bead is open circuit 开n It refers to the theoretical value of the output voltage Vadc of the diagnostic terminal ADC when the nth LED lamp bead of the LED mixing circuit is open circuit. ΔV2n is equal to V 标 With V 开n The difference, V 开1 、V 开2 and V 开3 The calculation formulas are as follows:

[0048]

[0049]

[0050]

[0051] In this embodiment, k21, k22 and k23 are obtained by consulting the technical manual. In other implementations, k2n (n=1, 2 and 3) is obtained by an open circuit calibration step, which includes artificially opening the LED lamp beads of the n-th LED lamp bead driving circuit (which can be achieved by removing the LED lamp beads), collecting the output voltage of the diagnosis terminal at multiple different temperatures, and performing linear fitting on the multiple temperatures and the collected multiple output voltages to obtain k2n.

[0052] T 标定 Both Temp and Temp are obtained by collecting the temperature detection value of the temperature sensor by the controller. In some specific implementations, the controller adopts MCU.

[0053] In actual applications, each product performs the aforementioned calibration steps before leaving the factory, and performs the aforementioned fault diagnosis steps during the actual working process after leaving the factory.

[0054] The above-mentioned diagnostic method corrects and performs temperature compensation processing on the theoretical value of the diagnostic terminal output voltage when the LED lamp bead short circuit fault and open circuit fault occur in the LED mixing circuit, thereby improving the accuracy and reliability of the diagnostic result.

[0055] The embodiment of the utility model is suitable for application in an atmosphere lamp system without MCU control. It not only solves the problem that only one diagnostic signal needs to report an open-short circuit fault, but also solves the problem that the LED lamp bead current exceeds the rated value when high voltage occurs by means of the overvoltage protection function of the overvoltage protection circuit.

[0056] The above description is a further explanation of the utility model in combination with the specific implementation methods and the accompanying drawings. However, the utility model can obviously be implemented in a variety of other methods different from the description, and those skilled in the art can generalize and deduce according to actual usage without violating the content of the utility model. Therefore, the content of the above specific embodiments should not limit the protection scope determined by the utility model.

Claims

1. An LED light mixing circuit, comprising three power input terminals, a diagnostic terminal, three LED lamp bead driving circuits and a diagnostic circuit; each LED lamp bead driving circuit comprises an LED lamp bead and a triode constant current circuit, and the LED lamp bead is grounded via the triode constant current circuit; characterized in that: The first input terminal and the second input terminal of the triode constant current circuit of each LED lamp bead driving circuit are respectively connected to the anode and cathode of the LED lamp bead of the LED lamp bead driving circuit; The three power input terminals are respectively connected to the common connection points of the anodes of the LED lamp beads of the three-way LED lamp bead driving circuit and the first input terminal of the triode constant current circuit; The diagnostic circuit includes a resistor R5, a resistor R11, a resistor R17 and a resistor R19; the first end of the resistor R5 is connected to the common point of the cathode of the LED lamp bead of the first LED lamp bead driving circuit and the second input end of the triode constant current circuit, the first end of the resistor R11 is connected to the common point of the cathode of the LED lamp bead of the second LED lamp bead driving circuit and the second input end of the triode constant current circuit, and the first end of the resistor R17 is connected to the common point of the cathode of the LED lamp bead of the third LED lamp bead driving circuit and the second input end of the triode constant current circuit; the first end of the resistor R19 is respectively connected to the second end of the resistor R5, the second end of the resistor R11 and the second end of the resistor R17, and the second end of the resistor R19 is grounded; The diagnosis terminal is connected to a common point of the resistor R5 , the resistor R11 , the resistor R17 , and the resistor R19 .

2. The LED mixing circuit according to claim 1, characterized in that: The transistor constant current circuit comprises a first NPN transistor, a second NPN transistor, a first resistor and a second resistor; The first end of the first resistor constitutes the first input end of the transistor constant current circuit, the second end of the first resistor is connected to the collector of the first NPN transistor and the base of the second NPN transistor respectively, and the emitter of the first NPN transistor is grounded; The collector of the second NPN transistor constitutes the second input end of the transistor constant current circuit, the emitter of the second NPN transistor is respectively connected to the base of the first NPN transistor and the first end of the second resistor, and the second end of the second resistor is grounded.

3. The LED mixing circuit according to claim 2, characterized in that: Each LED lamp bead driving circuit includes an overvoltage protection circuit, and the overvoltage protection circuit includes an overvoltage conduction branch, a current limiting resistor and a switch tube; The first end of the overvoltage conduction branch is respectively connected to the power input end of the LED lamp bead driving circuit, the anode of the LED lamp bead, the first end of the first resistor and the first end of the current limiting resistor, the second end of the overvoltage conduction branch is grounded, and the output end of the overvoltage conduction branch is connected to the controlled end of the switch tube; The first conducting end of the switch tube is respectively connected to the second end of the current limiting resistor, the second end of the first resistor, the collector of the first NPN transistor and the base of the second NPN transistor, and the second conducting end of the switch tube is grounded; The overvoltage conduction branch is used to disconnect from the ground when the input voltage at the power input end does not reach the preset protection voltage threshold so that the switch tube is turned off, and is connected to the ground when the input voltage at the power input end reaches or exceeds the preset protection voltage threshold, and the input voltage is divided and output to the switch tube to turn on the switch tube. When the switch tube is turned on, it controls the first NPN transistor and the second NPN transistor to be disconnected.

4. The LED mixing circuit according to claim 3, characterized in that: The overvoltage conduction branch includes a first voltage-dividing resistor, a second voltage-dividing resistor and a voltage-stabilizing diode; The first end of the first voltage-dividing resistor constitutes the first end of the overvoltage conduction branch, the second end of the first voltage-dividing resistor is connected to the cathode of the voltage-regulating diode, the anode of the voltage-regulating diode is connected to the first end of the second voltage-dividing resistor, and the second end of the second voltage-dividing resistor constitutes the second end of the overvoltage conduction branch.

5. The LED mixing circuit according to claim 3, characterized in that: The switch tube is composed of a third NPN transistor, and the base, collector and emitter of the third NPN transistor respectively constitute the controlled end, the first conduction end and the second conduction end of the switch tube.

6. The LED mixing circuit according to claim 1, characterized in that: Each of the LED lamp bead driving circuits includes an anti-reverse element, and the anti-reverse element is connected in series between the power input terminal and the anode of the LED lamp bead.

7. The LED mixing circuit according to claim 1, characterized in that: The LED lamp beads of the three-way LED lamp bead driving circuit are respectively red LED lamp beads, green LED lamp beads and blue LED lamp beads.

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