LED lighting circuit and barcode reader

Abstract

This application relates to the field of LED technology and discloses an LED light-emitting circuit and a barcode reader. The LED light-emitting circuit includes an inductor, an LED unit composed of multiple LEDs connected in series, a first switch, a boost rectifier diode, a second switch, a transistor, a boost driver chip, a first capacitor, an overcurrent sampling resistor unit, and a voltage divider unit. One end of the inductor and the cathode of the LED unit are connected to the power supply through the first switch, and the other end is connected to the anode of the boost rectifier diode. The boost rectifier diode is connected to the anode of the LED unit through the second switch. The transistor is connected to the anode of the boost rectifier diode, the boost driver chip, and the overcurrent sampling resistor unit. The first capacitor is connected to the cathode of the boost rectifier diode, the voltage divider unit, and the overcurrent sampling resistor unit. The second end of the voltage divider unit is connected to the third pin of the boost driver chip. This application enhances the brightness of the light source.

Description

Technical Field

[0001] This application relates to the field of LED technology, specifically to an LED light-emitting circuit and a barcode reader. Background Technology

[0002] A barcode reader is an automated input device that uses photoelectric technology to convert graphic information (such as 1D or 2D barcodes) printed on the surface of an object into data that can be recognized and processed by a computer. Its working principle typically involves a built-in light source illuminating the graphic code, an optical device receiving the reflected light, and an image sensor or photoelectric conversion element converting the reflected light signal into an electrical signal. Finally, decoding software decodes the signal to extract the characters, numbers, and other information contained in the graphic code.

[0003] However, if the light intensity emitted by the built-in light source of the barcode reader is insufficient, the light signal reflected from the graphic barcode may be weakened, thus affecting the reader's recognition rate and decoding accuracy. How to enhance the light intensity emitted by the built-in light source of the barcode reader is a problem that needs to be solved. Utility Model Content

[0004] In view of the above problems, this application provides an LED light-emitting circuit and a barcode reader to solve the problem of insufficient light intensity emitted by the built-in light source of the barcode reader in the prior art.

[0005] According to one aspect of the embodiments of this application, an LED light-emitting circuit is provided, including an inductor, an LED unit composed of multiple LEDs connected in series, a first switch, a boost rectifier diode, a second switch, a transistor, a boost driver chip, a first capacitor, an overcurrent sampling resistor unit, and a voltage divider unit; one end of the inductor and the cathode of the LED unit are respectively connected to a power supply through the first switch, and the other end of the inductor is connected to the anode of the boost rectifier diode; the cathode of the boost rectifier diode is connected to the anode of the LED unit through the second switch; the collector of the transistor is connected to the boost rectifier diode... The anode of the voltage-reducing rectifier diode is connected, the base of the transistor is connected to the first pin of the boost driver chip, and the emitter of the transistor is connected to the second pin of the boost driver chip and the first terminal of the overcurrent sampling resistor unit. One end of the first capacitor is connected to the cathode of the boost rectifier diode and the first terminal of the voltage divider unit, and the other end of the first capacitor is connected to the second terminal of the overcurrent sampling resistor unit. The second terminal of the voltage divider unit is connected to the third pin of the boost driver chip. The third terminals of the overcurrent sampling resistor unit and the third terminals of the voltage divider unit are grounded.

[0006] In one alternative embodiment, the overcurrent sampling resistor unit includes a first resistor and a second resistor connected in series, wherein a first end of the first resistor is a first end of the overcurrent sampling resistor unit, a second end of the first resistor is connected to a first end of the second resistor, the second end of the first resistor is a second end of the overcurrent sampling resistor unit, and the second end of the second resistor is a third end of the overcurrent sampling resistor unit.

[0007] In one alternative embodiment, the voltage divider unit includes a third resistor and a fourth resistor connected in series, wherein the first end of the third resistor is the first end of the voltage divider unit, the second end of the third resistor is connected to the first end of the fourth resistor, the second end of the third resistor is the second end of the voltage divider unit, and the second end of the fourth resistor is the third end of the voltage divider unit.

[0008] In one alternative approach, the boost driver chip determines the current flowing through the inductor by the voltage acquired by the second pin. If the current is greater than or equal to a current threshold, the boost driver chip controls the transistor to switch from the on state to the off state.

[0009] In one alternative approach, the boost driver chip controls the operating state of the transistor based on the voltage acquired by the third pin. If the voltage acquired by the third pin is greater than or equal to a voltage threshold, the boost driver chip controls the transistor to switch from the on state to the off state.

[0010] In an alternative embodiment, the circuit further includes a second capacitor, with one end of the second capacitor connected to the power supply pin of the boost driver chip and the other end of the second capacitor grounded.

[0011] In an alternative embodiment, the circuit further includes a third capacitor, the two ends of which are connected to the anode and cathode of the LED unit, respectively.

[0012] According to another aspect of the embodiments of this application, a barcode reader is provided, the barcode reader including a microcontroller unit and an LED light-emitting circuit as described above, the microcontroller unit being connected to the first switch and the second switch respectively.

[0013] In one alternative approach, when the barcode reader is in operation, the microcontroller controls the first switch to close and controls the second switch to open; in response to the barcode reader receiving a trigger signal, the microcontroller controls the first switch to open and controls the second switch to close.

[0014] In one alternative approach, when the barcode reader is in a non-operating state, the microcontroller controls both the first switch and the second switch to be turned off.

[0015] In the LED light-emitting circuit provided in this application embodiment, in the first stage: when the first switch is closed, the second switch is open, and the transistor is turned on, the inductor receives the voltage provided by the power supply, and the boost driver chip determines the current flowing through the inductor based on the voltage acquired by the second pin, and controls the operation of the transistor according to the current. In the second stage following the first stage: when the first switch is closed and the second switch is open, the first capacitor simultaneously receives the voltages provided by the power supply and the inductor, and the boost driver chip controls the operation of the transistor according to the voltage acquired by the third pin. In the third stage following the second stage: when the first switch is open and the second switch is closed, the first capacitor provides voltage to the LED unit to make the LED unit emit light.

[0016] In this embodiment, due to the inclusion of an inductor, a first switch, a boost rectifier diode, a second switch, a transistor, a boost driver chip, and a first capacitor, the LED light-emitting circuit can store energy by receiving voltage from the power supply VCC in the first stage; in the second stage, the first capacitor can simultaneously receive voltage from both the power supply and the inductor to store energy, achieving an effect where the voltage of the first capacitor is greater than the power supply voltage; and in the third stage, the first capacitor provides a larger voltage to the LED unit to drive all LEDs to emit light, thereby enhancing the brightness of the light source.

[0017] Furthermore, in this embodiment, by setting an overcurrent sampling resistor unit, the boost driver chip can control the state of the transistor in a timely manner based on the sampled current, thereby avoiding damage to the inductor and transistor due to excessive current flowing through them. By setting a voltage divider unit, the boost driver chip can control the state of the transistor in a timely manner based on the sampled voltage of the first capacitor without damaging it, preventing the power supply and inductor from continuing to provide voltage to the first capacitor when its energy storage reaches saturation, thus avoiding energy waste.

[0018] The above description is merely an overview of the technical solutions of the embodiments of this application. In order to better understand the technical means of the embodiments of this application and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of this application more obvious and understandable, specific implementation methods of this application are described below. Attached Figure Description

[0019] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0020] Figure 1A schematic diagram of an LED light-emitting circuit provided in an embodiment of this application is shown;

[0021] Figure 2 A schematic diagram of a barcode reader provided in an embodiment of this application is shown. Detailed Implementation

[0022] Exemplary embodiments of the present application will now be described in more detail with reference to the accompanying drawings. Although exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application may be implemented in various forms and should not be limited to the embodiments set forth herein.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0024] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0025] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0026] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, representing any combination of the listed objects. For example, "A and / or B" can represent three possibilities: A exists, A and B exist simultaneously, or B exists. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0027] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0028] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0029] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0030] Light-emitting diodes (LEDs) have become one of the most commonly used light sources in modern barcode readers due to their low power consumption, long lifespan, fast response speed, and stable light emission. Since the more LEDs there are, the stronger the emitted light, increasing the number of LEDs in a barcode reader can effectively improve the brightness of the light source, thereby improving the barcode reading effect.

[0031] However, since the power supply voltage used to drive the LEDs in a barcode reader is typically low, increasing the number of LEDs may exceed the power supply's driving capacity, resulting in insufficient voltage to drive all LEDs to emit light normally, thus affecting the overall brightness of the light source. Therefore, how to drive multiple LEDs to emit light normally after increasing the number of LEDs is a problem that needs to be solved.

[0032] To enhance the brightness of the light source in a barcode reader, this application proposes an LED light-emitting circuit, including an inductor, multiple LEDs connected in series, and a first capacitor. First, the inductor is powered by the reader's internal power supply, allowing it to store energy. Then, the inductor is controlled to release energy and generate an induced voltage. This voltage, superimposed with the power supply voltage, charges the first capacitor, giving it a voltage higher than the input power supply voltage. Finally, the first capacitor provides a driving voltage higher than the power supply voltage to the multiple LEDs, ensuring all LEDs emit light normally, thereby effectively improving the light source brightness. The LED light-emitting circuit provided in this application will be described in detail below with reference to the accompanying drawings.

[0033] Figure 1 A schematic diagram of an LED light-emitting circuit provided in an embodiment of this application is shown. For example... Figure 1 As shown, the LED light-emitting circuit includes an inductor L1, an LED unit consisting of five LEDs connected in series, a first switch SW1, a boost rectifier diode D1, a second switch SW2, a transistor Q1, a boost driver chip U1, a first capacitor C1, an overcurrent sampling resistor unit consisting of a first resistor R1 and a second resistor R2, and a voltage divider unit consisting of a third resistor R3 and a fourth resistor R4. It is worth noting that... Figure 1 This paper only uses an LED unit containing five LEDs as an example. This application does not limit the number of LEDs included in the LED unit. The number of LEDs in the LED unit can be set as needed and is not limited here.

[0034] Figure 1 In this circuit, one end of inductor L1 and the cathode of the LED unit are connected to the power supply VCC via the first switch SW1, and the other end of inductor L1 is connected to the anode of boost rectifier diode D1. The cathode of boost rectifier diode D1 is connected to the anode of the LED unit via the second switch SW2. Transistor Q1 is an NPN transistor. The collector of transistor Q1 is connected to the anode of boost rectifier diode D1, the base of transistor Q1 is connected to the first pin (DRIVE pin) of boost driver chip U1, and the emitter of transistor Q1 is connected to the second pin (SENSE pin) of boost driver chip U1 and the first end of the first resistor R1. One end of the first capacitor C1 is connected to the cathode of boost rectifier diode D1 and the first end of the third resistor R3, and the other end of the first capacitor C1 is connected to the second end of the first resistor R1. The second end of the first resistor R1 is connected to the first end of the second resistor R2, the second end of the third resistor R3 is connected to the first end of the fourth resistor R4, and the second ends of the second resistor R2 and the fourth resistor R4 are both grounded.

[0035] In the first stage: when the first switch SW1 is closed, the second switch SW2 is open, and the transistor Q1 is turned on, the inductor L1 receives the voltage provided by the power supply VCC to store energy in the inductor L1. However, since the maximum current that the inductor L1 can withstand is limited, in order to avoid damage to the inductor L1 due to excessive current flowing through it, the boost driver chip U1 in this application determines the current flowing through the inductor L1 by acquiring the voltage through the SENSE pin (i.e., pin 5). When the current flowing through the inductor L1 is greater than or equal to the current threshold, the boost driver chip U1 controls the transistor Q1 to switch from the on state to the off state to stop storing energy in the inductor L1, thereby preventing damage to the inductor L1 and the transistor Q1 due to excessive current. In this application, after the boost driver chip U1 acquires the voltage through the SENSE pin, it can determine the current flowing through the first resistor R1 based on the resistance values ​​of the first resistor R1 and the second resistor R2. Since the current flowing through the first resistor R1 is the same as the current flowing through the inductor L1, the current flowing through the inductor L1 is also determined. In this application, the current threshold can be set as needed, for example, it can be set to the maximum current value that the inductor L1 can withstand. The resistance values ​​of the first resistor R1 and the second resistor R2 can be determined as needed and are not limited here. It is worth noting that this application does not improve the boost driver chip U1; the boost driver chip U1 can utilize existing chips.

[0036] In the second stage following the first stage: When the first switch SW1 is closed and the second switch SW2 is open, the first capacitor C1 simultaneously receives voltages from the power supply VCC and the inductor L1 to store energy. As mentioned earlier, since the power supply VCC and the inductor L1 simultaneously supply voltages to the first capacitor C1, the voltage stored in the first capacitor C1 is higher than the voltage of the power supply VCC. Since the capacity of the first capacitor C1 is limited, if the power supply VCC and the inductor L1 continue to supply voltages to the first capacitor C1 when its energy storage reaches saturation, energy waste may occur. Therefore, in this application, the VFB pin of the boost driver chip U1 is used to acquire the voltage of the first capacitor C1. When the voltage of the first capacitor C1 is greater than or equal to the voltage threshold, it is determined that the energy storage of the first capacitor C1 has reached saturation. Then, the boost driver chip U1 controls the transistor Q1 to switch from the on state to the off state to stop supplying voltage to the first capacitor C1. Because the voltage of the first capacitor C1 is relatively high, while the voltage that the VFB pin of the boost driver chip U1 can withstand is limited, directly sampling the voltage of the first capacitor C1 using the VFB pin of the boost driver chip U1 might result in excessive voltage, potentially damaging the boost driver chip U1. Therefore, this application designs a voltage divider unit composed of a third resistor R3 and a fourth resistor R4 to proportionally reduce the high voltage of the first capacitor C1 to within the voltage range that the VFB pin of the boost driver chip U1 can withstand (typically, the voltage that the VFB pin can withstand is less than 2V). This allows the boost driver chip U1 to determine whether the energy stored in the first capacitor C1 has reached saturation based on the voltage sampled from the VFB pin, thereby preventing damage to the boost driver chip U1. The resistance values ​​of the third resistor R3 and the fourth resistor R4 can be determined as needed and are not limited here.

[0037] In the third stage following the second stage: when the first switch SW1 is open and the second switch SW2 is closed, the first capacitor C1 provides voltage to the LED unit so that all the LEDs in the LED unit light up.

[0038] In summary, in the LED light-emitting circuit provided in this application, the first switch SW1 controls whether the entire circuit is powered on or off. When the first switch SW1 is closed, it supplies power to the boost driver chip U1 and inductor L1, and the boost driver chip U1 is powered on and begins to work. The boost driver chip U1, as the main control chip, drives transistor Q1 through the DRIVE pin. After sampling the current through the SENSE pin and detecting that the current reaches its peak value, it controls transistor Q1 to turn off. It stops boosting when the output voltage of the first capacitor C1 is greater than or equal to the voltage threshold sampled by the VFB pin. When transistor Q1 is on, the power supply VCC charges inductor L1; when transistor Q1 is off, it forces inductor L1 to discharge into the first capacitor C1, thus achieving boosting. The boost rectifier diode D1 prevents reverse output and directs the induced energy of inductor L1 into the first capacitor C1. The first capacitor C1, acting as an energy storage and filtering capacitor, has a voltage much higher than the power supply VCC voltage, thereby providing a "high instantaneous current" for LED light emission.

[0039] The first resistor R1 and the second resistor R2 are connected in series at the emitter of transistor Q1, forming an overcurrent sampling resistor network. When transistor Q1 is turned on, current flows through the first resistor R1 and the second resistor R2, forming a voltage drop, which is then divided and sent to the SENSE pin of the boost driver chip U1. If the current is too large, the boost driver chip U1 will control transistor Q1 to enter the cutoff state, thereby protecting inductor L1 and transistor Q1. The second switch SW2 acts as a trigger switch. When it is closed, it can directly connect the LED to the first capacitor C1, which has been charged to a high voltage, so that the LED can draw energy stored in the first capacitor C1 to emit light; when the second switch SW2 is open, the LED is turned off.

[0040] In the LED light-emitting circuit provided in this embodiment, due to the inclusion of an inductor L1, a first switch SW1, a boost rectifier diode D1, a second switch SW2, a transistor Q1, a boost driver chip U1, and a first capacitor C1, the LED light-emitting circuit can achieve the following: in the first stage, the inductor L1 can receive the voltage provided by the power supply VCC to store energy; in the second stage, the first capacitor C1 can simultaneously receive the voltages provided by the power supply VCC and the inductor L1 to store energy, achieving the effect that the voltage of the first capacitor C1 is greater than the voltage of the power supply VCC; in the third stage, the first capacitor C1 provides a larger voltage to the LED unit to drive all LEDs to emit light, thereby enhancing the brightness of the light source. Figure 1 Taking an LED unit comprising five high-brightness LEDs as an example, each LED has a forward voltage drop of approximately 2.8–3.2V, resulting in a total voltage of approximately 14–16V when connected in series. If the operating voltage is directly supplied to the LED unit using the power supply VCC, the LED unit cannot be driven to operate normally. In this application, through the aforementioned configuration, the first capacitor C1 provides a high voltage to the LED unit, enabling the LEDs to emit light normally.

[0041] Furthermore, in this embodiment, by setting an overcurrent sampling resistor unit, the boost driver chip U1 can control the state of transistor Q1 in a timely manner based on the sampled current, thereby avoiding damage to inductor L1 and transistor Q1 due to excessive current flowing through them. By setting a voltage divider unit, the boost driver chip U1 can control the state of transistor Q1 in a timely manner based on the sampled voltage of the first capacitor C1 without damaging it, thus preventing the power supply VCC and inductor L1 from continuing to supply voltage to the first capacitor C1 when the first capacitor C1 reaches saturation, thereby avoiding energy waste.

[0042] like Figure 1 As shown, the power supply VCC is also connected to the power supply pin (i.e., the VCC pin) of the boost driver chip U1 to provide operating voltage to the boost driver chip U1. Further, in this application, to ensure that the power supply VCC can stably supply power to the boost driver chip U1, the LED light-emitting circuit also includes a second capacitor C2. One end of the second capacitor C2 is connected to the VCC pin of the boost driver chip U1, and the other end of the second capacitor C2 is grounded. Through the above configuration, the second capacitor C2 acts as a filter capacitor at the power input terminal of the boost driver chip U1, smoothing the voltage provided by the power supply VCC and suppressing ripple and transient pulses, thereby ensuring that the power supply VCC can stably supply power to the boost driver chip U1.

[0043] like Figure 1 As shown in the present application, the LED light-emitting circuit further includes a third capacitor C3, wherein the two ends of the third capacitor C3 are connected in parallel across the two ends of the LED unit for filtering and bypassing, so as to ensure the stability of the current flowing through the LED during the LED flashing process.

[0044] Figure 2 A schematic diagram of a barcode reader provided in an embodiment of this application is shown. Figure 2 As shown, the barcode reader includes a microcontroller unit (MCU) and... Figure 1 The illustrated embodiment provides an LED light-emitting circuit. The MCU is connected to the first switch SW1 and the second switch SW2, respectively.

[0045] When the barcode reader is in operation, the MCU controls the first switch SW1 to close and the second switch SW2 to open, causing the LED lighting circuit to enter the first and second stages. In response to the barcode reader receiving a trigger signal, the MCU controls the first switch SW1 to open and the second switch SW2 to close, causing the LED lighting circuit to enter the third stage, and the LED illuminates. This trigger signal is the signal that triggers the barcode reader to enter the scanning state. For example, a trigger button can be set on the barcode reader; when the user needs to control the barcode reader to scan, the user presses the trigger button, and the barcode reader receives the trigger signal.

[0046] Since the power supply VCC in the barcode reader has limited capacity, in order to improve the barcode reader's operating time, in this embodiment of the application, when the barcode reader is in a non-working state, the MCU controls both the first switch SW1 and the second switch SW2 to be turned off, so that the barcode reader enters a low-power mode, thereby reducing the power consumption of the barcode reader and increasing the operating time.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. An LED light emitting circuit, characterized by, It includes an inductor, an LED unit consisting of multiple LEDs connected in series, a first switch, a boost rectifier diode, a second switch, a transistor, a boost driver chip, a first capacitor, an overcurrent sampling resistor unit, and a voltage divider unit; One end of the inductor and the cathode of the LED unit are respectively connected to the power supply through the first switch, and the other end of the inductor is connected to the anode of the boost rectifier diode. The cathode of the boost rectifier diode is connected to the anode of the LED unit via the second switch; The collector of the transistor is connected to the anode of the boost rectifier diode, the base of the transistor is connected to the first pin of the boost driver chip, and the emitter of the transistor is connected to the second pin of the boost driver chip and the first end of the overcurrent sampling resistor unit, respectively. One end of the first capacitor is connected to the cathode of the boost rectifier diode and the first end of the voltage divider unit, respectively, and the other end of the first capacitor is connected to the second end of the overcurrent sampling resistor unit; The second end of the voltage divider unit is connected to the third pin of the boost driver chip; The third terminal of the overcurrent sampling resistor unit and the third terminal of the voltage divider unit are respectively grounded.

2. The LED light emitting circuit of claim 1, wherein, The overcurrent sampling resistor unit includes a first resistor and a second resistor connected in series. The first end of the first resistor is the first end of the overcurrent sampling resistor unit, the second end of the first resistor is connected to the first end of the second resistor, the second end of the first resistor is the second end of the overcurrent sampling resistor unit, and the second end of the second resistor is the third end of the overcurrent sampling resistor unit.

3. The LED light emitting circuit of claim 1, wherein, The voltage divider unit includes a third resistor and a fourth resistor connected in series. The first end of the third resistor is the first end of the voltage divider unit, the second end of the third resistor is connected to the first end of the fourth resistor, the second end of the third resistor is the second end of the voltage divider unit, and the second end of the fourth resistor is the third end of the voltage divider unit.

4. The LED light emitting circuit of claim 1, wherein, The boost driver chip determines the current flowing through the inductor by acquiring the voltage through the second pin. If the current is greater than or equal to the current threshold, the boost driver chip controls the transistor to switch from the on state to the off state.

5. The LED light emitting circuit of claim 1, wherein, The boost driver chip controls the working state of the transistor based on the voltage collected by the third pin. If the voltage collected by the third pin is greater than or equal to the voltage threshold, the boost driver chip controls the transistor to switch from the on state to the off state.

6. The LED light emitting circuit of claim 1, wherein, The circuit also includes a second capacitor. The power supply pin of the boost driver chip is connected to the power supply. One end of the second capacitor is connected to the power supply pin of the boost driver chip, and the other end of the second capacitor is grounded.

7. The LED light emitting circuit of claim 1, wherein, The circuit also includes a third capacitor, the two ends of which are connected to the anode and cathode of the LED unit, respectively.

8. A barcode reader, characterized in that, The barcode reader includes a microcontroller unit and an LED light-emitting circuit as described in any one of claims 1-7, wherein the microcontroller unit is connected to the first switch and the second switch respectively.

9. The code reader of claim 8, wherein, When the code reader is in the working state, the micro control unit controls the first switch to be closed and the second switch to be opened; In response to the code reader receiving a trigger signal, the micro control unit controls the first switch to be opened and the second switch to be closed.

10. The code reader of claim 8, wherein, When the code reader is in the non-working state, the micro control unit controls the first switch and the second switch to be both opened.

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