LED brightness adjusting device for industrial endoscope

Abstract

The utility model discloses an LED brightness adjusting device for an industrial endoscope, and relates to the technical field of circuit devices for operating LEDs. The circuit comprises a low-dropout linear stabilized power supply, a control unit and a light-emitting diode driving unit, a power output port of the low-dropout linear stabilized power supply is electrically connected with a power input port of the control unit, and an output end of the control unit is electrically connected with a control end of the light-emitting diode driving unit. A switch output port of the light-emitting diode driving unit is a port used for being electrically connected with a positive electrode of a light-emitting diode, and a feedback voltage input port of the light-emitting diode driving unit is a port used for being electrically connected with a negative electrode of the light-emitting diode; the output end of the control unit outputs the pulse signal PWM to control the magnitude of the output current of the light emitting diode driving unit, so that the brightness of the light emitting diode is adjusted, and the current is not turned on or off due to the adjustment of the magnitude of the current, so that flicker interference does not exist when an image is displayed.

Description

Technical Field

[0001] The utility model relates to the technical field of circuit devices for operating LEDs, in particular to an LED brightness adjustment device for an industrial endoscope. Background Art

[0002] The visual module of the industrial endoscope is inserted into the equipment for inspection and flaw detection. Usually, there is no lighting inside the equipment, and the visual module is in a dark environment. It must have its own LED as a lighting source. The LED brightness is generally controlled by PWM technology. PWM dimming is to change the ratio of the LED on and off time within a certain period of time to change the total lighting time of the LED, thereby adjusting the LED brightness.

[0003] At present, the PWM control dimming of the vision module has a defect: when shooting video, due to the opening and closing of the LED, the exposure time of the video image and the fill light cannot be synchronized, so flicker interference will appear on the image. The formation of this technical problem is detailed as follows.

[0004] Industrial endoscopes are generally used in closed or semi-closed environments. Image sensors need moderate lighting conditions to clearly and accurately capture surface defects of objects. Exposure is the process of the camera sensor collecting images. Fill light is to achieve the illumination conditions required for clear imaging during the camera exposure process. It is a lighting method that uses circuits to control LED light emission. Endoscopes need to compensate for different light intensities in different lighting environments to prevent the image from being too dark or overexposed. Therefore, controlling the LED illumination can achieve this function. The LED illumination is controlled by its current, so it is necessary to control the LED current on and off or the size through a circuit to ultimately achieve adjustable illumination. Generally, PWM technology is used to directly control the current on and off of LED current. The principle is roughly stroboscopic fill light, which will result in inconsistent exposure timing with the image sensor, causing flickering interference in the image and affecting detection judgment. Utility Model Content

[0005] The utility model provides an LED brightness adjustment device for an industrial endoscope, which solves the technical problem of flicker interference when displaying images.

[0006] In order to solve the above technical problems, the technical solutions adopted by the utility model are as follows:

[0007] A LED brightness adjustment device for an industrial endoscope comprises a voltage-stabilized power supply, a control unit and a light-emitting diode drive unit, wherein the voltage-stabilized power supply is a low-voltage difference linear voltage-stabilized power supply, a power input port IN of the low-voltage difference linear voltage-stabilized power supply is a port for electrically connecting to a power supply VCC, a power output port OUT of the low-voltage difference linear voltage-stabilized power supply is electrically connected to the power input port of the control unit, a power input port VIN of the light-emitting diode drive unit is a port for electrically connecting to the power supply VCC, an output terminal LED_PWM of the control unit is electrically connected to a control terminal of the light-emitting diode drive unit, a switch output port SW of the light-emitting diode drive unit is a port for electrically connecting to a positive electrode of a light-emitting diode, and a feedback voltage input port FB of the light-emitting diode drive unit is a port for electrically connecting to a negative electrode of the light-emitting diode.

[0008] A further technical solution is that the low voltage difference linear voltage regulator power supply includes a low voltage difference linear voltage regulator chip U1 and first to third capacitors C1~C3, the power input port IN of the low voltage difference linear voltage regulator chip U1 is the power input port of the control unit, the power output port OUT of the low voltage difference linear voltage regulator chip U1 is the power output port OUT of the low voltage difference linear voltage regulator power supply, the ground port GND of the low voltage difference linear voltage regulator chip U1 is grounded, the first capacitor C1 is connected between the power input port IN and the ground port GND of the low voltage difference linear voltage regulator chip U1, the second capacitor C2 is connected between the power output port OUT and the ground port GND of the low voltage difference linear voltage regulator chip U1, and the second capacitor C2 is connected in parallel with the third capacitor C3.

[0009] A further technical solution is that the control unit includes a microprocessor U2, a first resistor R1, a second resistor R2, eighth to tenth capacitors C8~C10, a first button S1 and a second button S2, the power input port VDD and the power input port VDDA of the microprocessor U2 are both power input ports of the control unit, the output terminal LED_PWM of the microprocessor U2 is the output terminal LED_PWM of the control unit, the ground terminal VSS and the BOOT0 terminal of the microprocessor U2 are both grounded, the first input terminal of the microprocessor U2 is grounded via the first resistor R1 and the first button S1 in sequence, the first input terminal is grounded via the eighth capacitor C8, the second input terminal of the microprocessor U2 is grounded via the second resistor R2 and the second button S2 in sequence, the second input terminal is grounded via the ninth capacitor C9, and the reset terminal nRST of the microprocessor U2 is grounded via the tenth capacitor C10.

[0010] A further technical solution is that the first button S1 and the second button S2 are both light-touch buttons.

[0011] A further technical solution is that the light-emitting diode driving unit includes a light-emitting diode driving chip U3, a third resistor R3, a fourth resistor R4, fourth to seventh capacitors C4 to C7 and an inductor L1, a power input port VIN of the light-emitting diode driving chip U3 is a power input port VIN of the light-emitting diode driving unit, the power input port VIN is grounded via a sixth capacitor C6, the power input port VIN is grounded via a seventh capacitor C7, a pulse signal input port DIM of the light-emitting diode driving chip U3 is a control end of the light-emitting diode driving unit, the pulse signal input port DIM is electrically connected to the output end LED_PWM of the control unit via the third resistor R3, and the light-emitting diode The switch output port SW of the tube driving chip U3 is the switch output port SW of the light emitting diode driving unit, and the switch output port SW is a port for electrically connecting to the positive electrode of the light emitting diode through the inductor L1. The feedback voltage input port FB of the light emitting diode driving chip U3 is the feedback voltage input port FB of the light emitting diode driving unit, and the feedback voltage input port FB is grounded through the fourth resistor R4. The feedback voltage input port FB is a port for electrically connecting to the negative electrode of the light emitting diode. The fourth capacitor C4 is connected between the bootstrap capacitor port BOOT of the light emitting diode driving chip U3 and the switch output port SW, and the junction of the inductor L1 and the light emitting diode is grounded through the fifth capacitor C5.

[0012] A further technical solution is that it also includes a power supply VCC and a light-emitting diode, the power input port IN of the low-voltage difference linear voltage-regulated power supply is electrically connected to the power supply VCC, the power input port VIN of the light-emitting diode driving unit is electrically connected to the power supply VCC, the switch output port SW of the light-emitting diode driving unit is electrically connected to the positive electrode of the light-emitting diode, and the feedback voltage input port FB of the light-emitting diode driving unit is electrically connected to the negative electrode of the light-emitting diode.

[0013] The beneficial effects of adopting the above technical solution are:

[0014] An LED brightness adjustment device for an industrial endoscope includes a voltage-stabilized power supply, a control unit, and a light-emitting diode drive unit. The voltage-stabilized power supply is a low-voltage difference linear voltage-stabilized power supply. The power input port IN of the low-voltage difference linear voltage-stabilized power supply is a port for electrically connecting to a power supply VCC. The power output port OUT of the low-voltage difference linear voltage-stabilized power supply is electrically connected to the power input port of the control unit. The power input port VIN of the light-emitting diode drive unit is a port for electrically connecting to the power supply VCC. The output end LED_PWM of the control unit is electrically connected to the control end of the light-emitting diode drive unit. The switch output port SW of the light-emitting diode drive unit is a port for electrically connecting to the positive electrode of the light-emitting diode. The feedback voltage input port FB of the light-emitting diode drive unit is a port for electrically connecting to the negative electrode of the light-emitting diode. The output end LED_PWM of the control unit outputs a pulse signal PWM to control the magnitude of the output current of the light-emitting diode drive unit, thereby realizing the light-emitting diode brightness adjustment. Since the magnitude of the current is adjusted instead of turning the current on or off, there is no flicker interference when displaying an image.

[0015] Please refer to the detailed description of the specific implementation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the circuit schematic diagram of the low voltage difference linear voltage regulated power supply of the utility model;

[0017] Figure 2 It is a circuit schematic diagram of the control unit in the utility model;

[0018] Figure 3 It is a circuit schematic diagram of the light emitting diode driving unit in the utility model;

[0019] Figure 4 It is a current curve diagram of a pulse signal with a duty cycle of 50% in the prior art solution;

[0020] Figure 5 It is a current curve diagram of a pulse signal with a duty cycle of 75% in the prior art solution;

[0021] Figure 6 It is a current curve diagram of a pulse signal with a duty cycle of 50% in the utility model;

[0022] Figure 7 It is a current curve diagram of a pulse signal with a duty cycle of 75% in the utility model. DETAILED DESCRIPTION

[0023] The purpose of this application is to provide an LED brightness adjustment device for an industrial endoscope, which adjusts the LED brightness by controlling the current flowing through the LED, thereby solving the technical problem of LED flicker interference when the visual module shoots video.

[0024] In order to solve the technical problem of flickering display images, the present application selects a circuit to achieve deep analog dimming by changing the internal reference voltage in proportion to the duty cycle of the PWM signal input in the range of 1% to 100%. This method is used to adjust the brightness without generating flicker interference.

[0025] The improved fill light control circuit uses PWM technology to convert analog DC levels to control the LED current. In this way, the fill light intensity changes continuously during the exposure process, so the image sensor will not produce flicker interference.

[0026] In order to achieve the above objectives, this application adopts the following technical solutions.

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0028] In the following description, many specific details are set forth to facilitate a full understanding of the present application, but the present application may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0029] like Figure 1 to Figure 3 As shown, the utility model discloses an LED brightness adjustment device for an industrial endoscope, including a low-voltage difference linear voltage-regulated power supply, a control unit and a light-emitting diode driving unit, wherein a power input port IN of the low-voltage difference linear voltage-regulated power supply is used to be electrically connected to a power supply VCC, a power output port OUT of the low-voltage difference linear voltage-regulated power supply is electrically connected to a power input port of the control unit, and a power input port VIN of the light-emitting diode driving unit is used to be electrically connected to the power supply VCC.

[0030] The output terminal LED_PWM of the control unit is electrically connected to the control terminal of the light-emitting diode driving unit, the switch output port SW of the light-emitting diode driving unit is used to be electrically connected to the positive electrode of the light-emitting diode LED1, and the feedback voltage input port FB of the light-emitting diode driving unit is used to be electrically connected to the negative electrode of the light-emitting diode LED1, so as to adjust the output current of the light-emitting diode driving unit.

[0031] like Figure 1As shown, the low voltage difference linear voltage regulator power supply includes a low voltage difference linear voltage regulator chip U1 and first to third capacitors C1~C3. The first pin of the low voltage difference linear voltage regulator chip U1, namely the ground port GND, is grounded. The second pin of the low voltage difference linear voltage regulator chip U1, namely the power input port IN, is used to be electrically connected to the power supply VCC. The third pin of the low voltage difference linear voltage regulator chip U1, namely the power output port OUT, is used to output the regulated power supply VDD. The first capacitor C1 is connected between the power input port IN and the ground port GND of the low voltage difference linear voltage regulator chip U1. The second capacitor C2 is connected between the power output port OUT and the ground port GND of the low voltage difference linear voltage regulator chip U1. The second capacitor C2 is connected between the power output port OUT and the ground port GND of the low voltage difference linear voltage regulator chip U1. The second capacitor C2 is connected in parallel with the third capacitor C3. The positive electrodes of the second capacitor C2 and the third capacitor C3 are connected to the power output port OUT of the low voltage difference linear voltage regulator chip U1.

[0032] like Figure 2 As shown, the control unit includes a microprocessor U2, a first resistor R1, a second resistor R2, eighth to tenth capacitors C8-C10, a first button S1 and a second button S2. The 9th and 24th pins of the microprocessor U2, namely the power input port VDD, and the 48th pin, namely the power input port VDDA, are electrically connected to the power output port OUT of the low voltage difference linear voltage regulator chip U1. The 23rd and 47th pins of the microprocessor U2, namely the ground terminal VSS, and the 44th pin BOOT0 are all grounded. The first input terminal of the microprocessor U2, namely the data port PA8, is grounded via the first resistor R1 and the first button S1 in sequence. The second input terminal of the microprocessor U2, namely the data port PB15, is grounded via the second resistor R2 and the second button S2 in sequence. The first input terminal is grounded via the eighth capacitor C8, and the second input terminal is grounded via the ninth capacitor C9. The 7th pin of the microprocessor U2, namely the reset terminal nRST, is grounded via the tenth capacitor C10. The 19th pin PB1 of the microprocessor U2 is the output terminal LED_PWM. The first button S1 and the second button S2 are both touch buttons.

[0033] like Figure 3As shown, the light emitting diode driving unit includes a light emitting diode driving chip U3, a third resistor R3, a fourth resistor R4, fourth to seventh capacitors C4-C7 and an inductor L1, the 4th pin of the light emitting diode driving chip U3, namely the power input port VIN, is used to be electrically connected to the power supply VCC, the 3rd pin of the light emitting diode driving chip U3 is grounded, the 2nd pin of the light emitting diode driving chip U3, namely the pulse signal input port DIM, is electrically connected to the output end LED_PWM of the control unit via the third resistor R3, the 5th pin of the light emitting diode driving chip U3, namely the switch output port SW, is used to be electrically connected to the positive electrode of the light emitting diode LED1 via the inductor L1, the 1st pin of the light emitting diode driving chip U3, namely the feedback voltage input port FB, is grounded via the fourth resistor R4, and the light emitting diode driving unit is connected to the positive electrode of the light emitting diode LED1 via the inductor L1. The feedback voltage input port FB of the light emitting diode driver chip U3 is used to be electrically connected to the negative electrode of the light emitting diode LED1. The fourth capacitor C4 is connected between the 6th pin of the light emitting diode driver chip U3, i.e., the bootstrap capacitor port BOOT, and the 5th pin, i.e., the switch output port SW. The junction of the inductor L1 and the light emitting diode LED1 is grounded via the fifth capacitor C5. The power input port VIN of the light emitting diode driver chip U3 is grounded via the sixth capacitor C6. The power input port VIN of the light emitting diode driver chip U3 is grounded via the seventh capacitor C7. The sixth capacitor C6 and the seventh capacitor C7 are connected in parallel. The positive electrodes of the sixth capacitor C6 and the seventh capacitor C7 are connected to the power input port VIN of the light emitting diode driver chip U3. The negative electrodes of the sixth capacitor C6 and the seventh capacitor C7 are grounded.

[0034] The model of the low voltage difference linear voltage regulator chip U1 is HT7533-2, the model of the microprocessor U2 is MM32F0131, and the model of the light emitting diode driver chip U3 is TPS92200D2.

[0035] The resistance value of the first resistor R1 is 1KΩ, the resistance value of the second resistor R2 is 1KΩ, the resistance value of the third resistor R3 is 100Ω, and the resistance value of the fourth resistor R4 is 1.5Ω.

[0036] The capacitance of the first capacitor C1 is 10uF, the capacitance of the second capacitor C2 is 100uF, the capacitance of the third capacitor C3 is 0.1uF, the capacitance of the fourth capacitor C4 is 0.1uF, the capacitance of the fifth capacitor C5 is 10uF, the capacitance of the sixth capacitor C6 is 0.1uF, the capacitance of the seventh capacitor C7 is 10uF, the capacitance of the eighth capacitor C8 is 0.1uF, the capacitance of the ninth capacitor C9 is 0.1uF, and the capacitance of the tenth capacitor C10 is 0.1uF.

[0037] Among them, the low voltage difference linear voltage regulator chip U1, the microprocessor U2 and the light emitting diode driver chip U3 themselves and the corresponding connection technology are existing technologies and will not be described in detail here.

[0038] Instructions for use:

[0039] The LED brightness adjustment device of the present application is connected to the light-emitting diode LED1 on the industrial endoscope and the power supply, specifically including: electrically connecting the second pin of the low voltage difference linear voltage regulator chip U1, that is, the power input port IN, to the power supply VCC, electrically connecting the fourth pin of the light-emitting diode driver chip U3, that is, the power input port VIN, to the power supply VCC, electrically connecting the fifth pin of the light-emitting diode driver chip U3, that is, the switch output port SW, to the positive electrode of the light-emitting diode LED1 via the inductor L1, and electrically connecting the feedback voltage input port FB of the light-emitting diode driver chip U3 to the negative electrode of the light-emitting diode LED1.

[0040] By lightly touching the first button S1 and the second button S2, the duty cycle of the PWM pulse can be set and adjusted and the microprocessor U2 can be informed. The microprocessor U2 controls the light-emitting diode driver chip U3, thereby adjusting the output current of the light-emitting diode driver chip U3, and then changing the brightness of the light-emitting diode LED1.

[0041] The relationship between LED brightness and current is that the greater the current, the higher the brightness.

[0042] The output terminal LED_PWM of the microprocessor U2 of the present application outputs a pulse signal PWM. The pulse signal input port DIM of the light-emitting diode driver chip U3 proportionally adjusts the internal reference voltage Vref of the light-emitting diode driver chip U3 within a period according to the high and low levels of the received pulse signal PWM. At the same time, the current on the light-emitting diode LED1 generates a voltage Vfb on the sampling resistor, i.e., the fourth resistor R4. The internal comparator of the light-emitting diode driver chip U3 compares the size of Vfb and Vref received by the FB port. When Vfb is greater than Vref, the light-emitting diode driver chip U3 controls the internal circuit to reduce the current flowing through LED1 until Vfb is equal to Vref. Otherwise, the internal circuit is controlled to increase the current flowing through LED1 until Vfb is equal to Vref. LED brightness adjustment is achieved by regulating current in this way.

[0043] The beneficial technical effects of the present application are as follows: the device has a wide range of power input, and adjusts the output current of the light-emitting diode driver chip U3 by changing the duty cycle of the pulse signal PWM. The current output dynamic range is 0 amperes to 1.5 amperes, which is suitable for adjusting the brightness of LEDs of various powers, fully meeting the lighting needs of the visual module, while avoiding flicker interference on the video.

[0044] The technical effects of this application and the prior art are described by comparing them as follows:

[0045] The existing technical solution uses PWM signal to control the on-off of the forward working current, not the current size.

[0046] For example: the current of the LED is 5mA~60mA, and dimming provides a 60mA current to the LED.

[0047] like Figure 4 The figure shows the current curve of the pulse signal with a duty cycle of 50% in the prior art solution. In a 10ms period, when the PWM duty cycle is 50%, a current of 60mA flows through the LED within 5ms, and a current of 0mA flows through the LED within another 5ms.

[0048] like Figure 5 As shown, it is a current curve diagram of a pulse signal with a duty cycle of 75% in the prior art solution. If the PWM duty cycle is 75%, a current of 60mA flows through the LED within 7.5ms, and a current of 0mA flows within another 2.5ms.

[0049] like Figure 6 The current curve of the pulse signal with a duty cycle of 50% in this application is shown in FIG. 1. When the PWM dimming PWM duty cycle of this application is 50%, the current output by the LED driver chip U3 always flows in one cycle, and the effective current flowing in one cycle is 60mA*50%=30mA.

[0050] like Figure 7 The current curve of the pulse signal with a duty cycle of 75% in this application is shown. When the PWM dimming PWM duty cycle of this application is 75%, the current output by the LED driver chip U3 has current flowing through it in one cycle, and the effective current flowing through it in one cycle is 60mA*75%=45mA.

Claims

1. An LED brightness adjustment device for an industrial endoscope, comprising a voltage-stabilized power supply, a control unit and a light-emitting diode driving unit, characterized in that: The voltage-regulated power supply is a low-voltage-difference linear voltage-regulated power supply, the power input port IN of the low-voltage-difference linear voltage-regulated power supply is a port for being electrically connected to the power supply VCC, the power output port OUT of the low-voltage-difference linear voltage-regulated power supply is electrically connected to the power input port of the control unit, the power input port VIN of the light-emitting diode driving unit is a port for being electrically connected to the power supply VCC, the output terminal LED_PWM of the control unit is electrically connected to the control terminal of the light-emitting diode driving unit, the switch output port SW of the light-emitting diode driving unit is a port for being electrically connected to the positive electrode of the light-emitting diode, and the feedback voltage input port FB of the light-emitting diode driving unit is a port for being electrically connected to the negative electrode of the light-emitting diode; the control unit includes a microprocessor U2, a first resistor R1, the second resistor R2, the eighth to tenth capacitors C8~C10, the first button S1 and the second button S2, the power input port VDD and the power input port VDDA of the microprocessor U2 are both power input ports of the control unit, the output terminal LED_PWM of the microprocessor U2 is the output terminal LED_PWM of the control unit, the ground terminal VSS and the BOOT0 terminal of the microprocessor U2 are both grounded, the first input terminal of the microprocessor U2 is grounded via the first resistor R1 and the first button S1 in sequence, the first input terminal is grounded via the eighth capacitor C8, the second input terminal of the microprocessor U2 is grounded via the second resistor R2 and the second button S2 in sequence, the second input terminal is grounded via the ninth capacitor C9, and the reset terminal nRST of the microprocessor U2 is grounded via the tenth capacitor C10.

2. The LED brightness adjustment device for an industrial endoscope according to claim 1, characterized in that: The low voltage difference linear voltage regulator power supply includes a low voltage difference linear voltage regulator chip U1 and first to third capacitors C1~C3, the power input port IN of the low voltage difference linear voltage regulator chip U1 is the power input port of the control unit, the power output port OUT of the low voltage difference linear voltage regulator chip U1 is the power output port OUT of the low voltage difference linear voltage regulator power supply, the ground port GND of the low voltage difference linear voltage regulator chip U1 is grounded, the first capacitor C1 is connected between the power input port IN and the ground port GND of the low voltage difference linear voltage regulator chip U1, the second capacitor C2 is connected between the power output port OUT and the ground port GND of the low voltage difference linear voltage regulator chip U1, and the second capacitor C2 is connected in parallel with the third capacitor C3.

3. The LED brightness adjustment device for an industrial endoscope according to claim 1, characterized in that: The first button S1 and the second button S2 are both light-touch buttons.

4. The LED brightness adjustment device for an industrial endoscope according to claim 1, characterized in that: The light emitting diode driving unit comprises a light emitting diode driving chip U3, a third resistor R3, a fourth resistor R4, fourth to seventh capacitors C4-C7 and an inductor L1. The power input port VIN of the light emitting diode driving chip U3 is the power input port VIN of the light emitting diode driving unit. The power input port VIN is grounded via the sixth capacitor C6. The power input port VIN is grounded via the seventh capacitor C7. The pulse signal input port DIM of the light emitting diode driving chip U3 is the control end of the light emitting diode driving unit. The pulse signal input port DIM is electrically connected to the output end LED_PWM of the control unit via the third resistor R3. The switch output port SW of U3 is the switch output port SW of the light-emitting diode driving unit, and the switch output port SW is a port for electrically connecting to the positive electrode of the light-emitting diode via the inductor L1. The feedback voltage input port FB of the light-emitting diode driving chip U3 is the feedback voltage input port FB of the light-emitting diode driving unit, and the feedback voltage input port FB is grounded via the fourth resistor R4. The feedback voltage input port FB is a port for electrically connecting to the negative electrode of the light-emitting diode. The fourth capacitor C4 is connected between the bootstrap capacitor port BOOT of the light-emitting diode driving chip U3 and the switch output port SW, and the junction of the inductor L1 and the light-emitting diode is grounded via the fifth capacitor C5.

5. The LED brightness adjustment device for an industrial endoscope according to claim 1, characterized in that: It also includes a power supply VCC and a light-emitting diode, wherein the power input port IN of the low-voltage difference linear voltage-regulated power supply is electrically connected to the power supply VCC, the power input port VIN of the light-emitting diode driving unit is electrically connected to the power supply VCC, the switch output port SW of the light-emitting diode driving unit is electrically connected to the positive electrode of the light-emitting diode, and the feedback voltage input port FB of the light-emitting diode driving unit is electrically connected to the negative electrode of the light-emitting diode.

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