Optical power automatic control circuit of light emitting diode and electronic equipment

Abstract

The utility model relates to the technical field of photoelectric sensors, and discloses an optical power automatic control circuit of a light emitting diode, which comprises an operational amplifier, a load, a first resistor and a current regulating tube. When the light receiving diode senses the current emitted by the light emitting diode, the current is converted into load voltage through the load and input to the inverted input end of the operational amplifier, the operational amplifier outputs a corresponding control signal to the current adjusting tube according to the difference value between the load voltage and the reference voltage, and when the temperature changes, the load voltage changes correspondingly, and the current is adjusted. Therefore, according to the corresponding change of the load voltage and the reference voltage, the current emitted by the light emitting diode is adjusted through the difference value until the difference value is 0, and the optical power of the light emitting diode is the preset optical power, so that the optical power of the light emitting diode is constant when the temperature is changed, and the light emitting efficiency is improved. Therefore, the optical power of the light emitting diode can be automatically adjusted when the temperature changes, and it is ensured that the optical power is always kept at the preset optical power level.

Description

Technical Field

[0001] This utility model relates to the field of optical power control technology for photoelectric sensors, and in particular to an automatic optical power control circuit and electronic device for a light-emitting diode. Background Technology

[0002] In laser ranging products, the main controller typically controls the laser emitter to emit sinusoidally tuned light (i.e., the intensity of the light is sinusoidal) and illuminate the object being measured. The light is reflected by the object and received by the SIPM (silicon photon multiplier tube), which outputs an analog waveform. The main controller calculates the phase shift between the emitted and received sinusoidal waves to indirectly calculate the distance to the object.

[0003] However, the aforementioned laser ranging products require constant power drive when emitting laser light, and the optical power output by the light emitting tube will vary significantly with temperature changes. For example... Figure 1 As shown, taking a certain domestic laser emitting tube as an example, the power curve in the emitting tube's technical specifications shows that when the driving current of the emitting tube is equal to 24mA, there is 2mW of optical power output at 25 degrees Celsius. If the temperature rises to 30℃, 24mA will not reach the threshold current of the emitting tube, which is insufficient to drive the emitting tube to emit light or even damage the emitting tube, so that the normal ranging function cannot be completed.

[0004] Currently, relatively complex circuits and software are generally used to regulate the current of the photoemitting diode. This circuit typically first samples the analog voltage of the photoreceiving diode, then converts it into a digital signal via an ADC (analog-to-digital converter), and finally sends the digital signal to a DSP (DSP processor). The DSP processor analyzes whether the current value is increasing or decreasing, calculates and outputs a corresponding digital drive current signal, which is then converted back into an analog signal via a DAC (digital-to-analog converter) to regulate the current of the photoemitting diode. However, this circuit requires many modules, has complex software design, and high overall logic design requirements, resulting in a high cost. Utility Model Content

[0005] In view of the shortcomings of the prior art, the purpose of this utility model is to provide an automatic control circuit and electronic equipment for the optical power of a light-emitting diode, so as to solve the problem that temperature changes affect the output power of the emitting diode in the prior art.

[0006] To solve the above technical problems, the present invention adopts the following technical solution:

[0007] An automatic control circuit for the optical power of a light-emitting diode, the control circuit comprising an operational amplifier, a load, a first resistor, and a current regulating transistor;

[0008] The cathode of the photoreceiving diode and the anode of the photoemitting diode are connected to a power supply. The load is connected between the anode of the photoreceiving diode and ground. The non-inverting input of the operational amplifier is connected to a reference voltage. The inverting input of the operational amplifier is connected to the non-ground terminal of the load and is also connected to the output of the operational amplifier through a first resistor. The output of the operational amplifier is also connected to the control terminal of the current regulating transistor. The output of the current regulating transistor is connected to the cathode of the photoemitting diode.

[0009] The automatic optical power control circuit further includes a second resistor and a third resistor. The second resistor is connected in series between the non-inverting input of the operational amplifier and the reference voltage, and the third resistor is connected in series between the inverting input of the operational amplifier and the non-ground terminal of the load.

[0010] In the automatic optical power control circuit, the resistance values ​​of the second resistor and the third resistor are equal.

[0011] The automatic optical power control circuit also includes a fourth resistor, which is connected in series between the output terminal of the operational amplifier and the control terminal of the current regulating transistor.

[0012] In the aforementioned automatic optical power control circuit, the current regulating transistor is an NPN transistor. The base of the NPN transistor is the control terminal of the current regulating transistor and is connected to the output terminal of the operational amplifier. Its collector is the output terminal of the current regulating transistor and is connected to the cathode of the photoemitting diode. Its emitter is grounded.

[0013] In the aforementioned automatic optical power control circuit, the current regulating transistor is an NMOS transistor. The gate of the NMOS transistor is the control terminal of the current regulating transistor, which is connected to the output terminal of the operational amplifier. Its drain is the output terminal of the current regulating transistor, which is connected to the cathode of the photoemitting diode, and its source is grounded.

[0014] In the aforementioned automatic optical power control circuit, an inductor is connected in series between the collector of the transistor and the cathode of the photoemitting diode; or, an inductor is connected in series between the drain of the MOS transistor and the cathode of the photoemitting diode.

[0015] The automatic optical power control circuit also includes a power filtering module consisting of a fifth resistor, a first capacitor, and a second capacitor. One end of the fifth resistor is connected to the power supply, grounded through the first capacitor, and grounded through the second capacitor. The other end of the fifth resistor is connected to the cathode of the light receiving diode and the anode of the light emitting diode.

[0016] In the automatic optical power control circuit, the load is a sixth resistor, and the resistance value of the sixth resistor is equal to that of the first resistor.

[0017] This invention also provides an electronic device, including the optical power automatic control circuit described above, wherein the optical power automatic control circuit is connected to an optical emitting diode and an optical receiving diode.

[0018] Compared to existing technologies, the automatic optical power control circuit for the light-emitting diode provided by this utility model is connected between the anode of the light-receiving diode and the cathode of the light-emitting diode. The control circuit includes an operational amplifier, a load, a first resistor, and a current regulating transistor. When the light-receiving diode senses the current emitted by the light-emitting diode, it converts the current into a load voltage through the load and inputs it to the inverting input terminal of the operational amplifier. The operational amplifier outputs a corresponding control signal to the current regulating transistor based on the difference between the load voltage and the reference voltage. When the temperature changes, the load voltage changes accordingly. Therefore, the corresponding change between the load voltage and the reference voltage adjusts the current emitted by the light-emitting diode through the difference until the difference is 0, so that the optical power of the light-emitting diode is at the preset optical power. This achieves constant optical power of the light-emitting diode when the temperature changes, thus automatically adjusting the optical power of the light-emitting diode when the temperature changes, ensuring that it always remains at the preset optical power level. Attached Figure Description

[0019] Figure 1 This is a graph showing the output power of a photodiode in the prior art.

[0020] Figure 2 A circuit diagram of one embodiment of the automatic optical power control circuit for the optical emitting diode provided by this utility model.

[0021] Explanation of reference numerals in the attached figures

[0022] Photodetector diode LD, photoemitting diode PD, operational amplifier U1, load 10, first resistor R1, current regulator Q1, second resistor R2, third resistor R3, fourth resistor R4, inductor L1, fifth resistor R5, first capacitor C1, second capacitor C2, sixth resistor R6 Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0024] The automatic optical power control circuit for the optical emitting diode (PD) provided by this utility model can be used in products such as laser rangefinders, automotive collision avoidance detection, robotic vacuum cleaners, and security monitoring. Please refer to [link / reference]. Figure 2The control circuit includes an operational amplifier U1, a load 10, a first resistor R1, and a current regulating transistor Q1. The cathode of the photoreceiving diode LD and the anode of the photoemitting diode PD are connected to the power supply, and the load 10 is connected between the anode of the photoreceiving diode LD and ground.

[0025] In an optional implementation, the light emitting diode PD and the light receiving diode LD can be packaged in a single photoelectric sensor. Since the temperature characteristics of the light receiving diode LD are stable and the output current of the light receiving diode LD is proportional to the luminous intensity of the light emitting diode PD, changes in external temperature (such as ambient temperature) have little effect on the magnitude of its photoelectric conversion current.

[0026] The non-inverting input of the operational amplifier U1 is connected to the reference voltage, and the inverting input of the operational amplifier U1 is connected to the non-ground terminal of the load 10 and is also connected to the output terminal of the operational amplifier U1 through the first resistor R1. The output terminal of the operational amplifier U1 is also connected to the control terminal of the current regulating transistor Q1, and the output terminal of the current regulating transistor Q1 is connected to the cathode of the photoemitting diode PD.

[0027] In this invention, when the light-receiving diode LD senses the current emitted by the light-emitting diode PD, it converts the current into a load voltage through the load 10 and inputs it to the inverting input of the operational amplifier U1. The operational amplifier U1 outputs a corresponding control signal to the current regulating transistor Q1 based on the difference between the load voltage and the reference voltage. When the temperature changes, the load voltage changes accordingly. Therefore, the difference between the load voltage and the reference voltage adjusts the current emitted by the light-emitting diode PD until the difference is 0, so that the light power of the light-emitting diode PD is at the preset light power. This achieves constant light power of the light-emitting diode PD when the temperature changes, thus automatically adjusting the light power of the light-emitting diode PD when the temperature changes, ensuring that it always remains at the preset light power level.

[0028] Meanwhile, this invention uses an operational amplifier U1 to monitor and adjust the difference between the load voltage 10 and the reference voltage in real time, which can achieve precise optical power control, avoid optical power fluctuations caused by environmental changes, and automate the optical power adjustment process without manual intervention, reducing operational complexity and the possibility of human error.

[0029] In the automatic optical power control circuit of this invention, a target optical power voltage value can be set first. When the light emission power of the light emitting diode PD decreases, the output current of the light receiving diode LD decreases accordingly. By increasing the driving current of the light emitting diode PD, the output optical power of the light emitting diode PD is increased until it increases to the voltage value converted by the light receiving diode LD, which is equal to the target optical power setting value. Similarly, when the optical power of the light emitting diode PD increases, the output current of the light receiving diode LD increases accordingly. At this time, the driving current of the light emitting diode PD is reduced by the automatic optical power control circuit to reduce the output optical power of the light emitting diode PD until it decreases to the voltage value converted by the light receiving diode LD, which is equal to the target optical power setting value, so that the light emission power of the light emitting diode PD is constant.

[0030] Please continue reading. Figure 2 The automatic optical power control circuit further includes a second resistor R2 and a third resistor R3. The second resistor R2 is connected in series between the non-inverting input terminal of the operational amplifier U1 and the reference voltage, and the third resistor R3 is connected in series between the inverting input terminal of the operational amplifier U1 and the non-ground terminal of the load 10.

[0031] The second resistor R2 provides a stable reference voltage to the positive input terminal IN+ of the operational amplifier U1. This reference voltage is compared with the voltage at the negative input terminal IN- of the operational amplifier U1 to determine the output of the operational amplifier U1. The second resistor R2 and the third resistor R3 are used to set the comparison voltage of the operational amplifier U1, thereby controlling the conduction state of the current regulating transistor Q1.

[0032] In this embodiment, the resistance values ​​of the second resistor R2 and the third resistor R3 are equal, such as 10KΩ, to ensure that the output voltage of the operational amplifier U1 is output according to the optical power received by the photodiode LD.

[0033] Please continue reading. Figure 2 The automatic optical power control circuit of this utility model also includes a fourth resistor R4, which is connected in series between the output terminal of the operational amplifier U1 and the control terminal of the current regulating transistor Q1. It is used to limit the current flowing into the base of the current regulating transistor Q1 and protect the current regulating transistor Q1 from damage caused by excessive current.

[0034] In one embodiment, the current regulating transistor Q1 is an NPN transistor. The base of the NPN transistor is the control terminal of the current regulating transistor Q1 and is connected to the output terminal of the operational amplifier U1. Its collector is the output terminal of the current regulating transistor Q1 and is connected to the cathode of the photoemitting diode PD, and its emitter is grounded. When the operational amplifier U1 outputs a high-level voltage, the current regulating transistor Q1 is turned on, causing the photoemitting diode PD to conduct and emit laser light. The driving current of the current regulating transistor Q1 changes with the output voltage of the operational amplifier U1, thereby controlling the output power of the photoemitting diode PD and ultimately controlling the optical power of the photoemitting diode PD.

[0035] In one specific embodiment, based on the current gain of the current regulating transistor Q1, such as 50 times, when the luminous power of the photodiode PD is 1mW, the base current Ib of the current regulating transistor Q1 is 23.1mA / 50 = 0.462mA; when the luminous power of the photodiode PD is 3mW, the base current Ib of the current regulating transistor Q1 is 25.3mA / 50 = 0.506mA; where 23.1mA and 25.3mA are the driving currents required for the luminous power of the photodiode PD at 1mW and 3mW, respectively. Simultaneously, Ib = (Vout - 0.7V) / R6, where Vout is the output of the operational amplifier U1, and 0.7V is the voltage between the base and emitter of the current regulating transistor Q1. The initial setting of the Ib current is met by setting the load R6, and the value of Ib is finely adjusted by changing Vout, thereby changing the collector current of the current regulating transistor Q1 and stabilizing the luminous power of the photodiode PD.

[0036] Please continue reading. Figure 2 In the automatic optical power control circuit of this utility model, an inductor L1 is connected in series between the collector of the transistor and the cathode of the light emitting diode PD. The inductor L1 is mainly used to store and release electrical energy, which can smooth the output current of the current regulating tube Q1, reduce voltage fluctuations, and stabilize the light emission of the light emitting diode PD.

[0037] In another embodiment, the current regulating transistor Q1 is an NMOS transistor. The gate of the NMOS transistor, which is the control terminal of the current regulating transistor Q1, is connected to the output terminal of the operational amplifier U1. Its drain, which is the output terminal of the current regulating transistor Q1, is connected to the cathode of the photoemitting diode PD, and its source is grounded. Since the conduction principle of an NMOS transistor is similar to that of an NPN transistor, it will not be described in detail here. Of course, in other embodiments, the current regulating transistor Q1 can also be other electronic components, such as an insulated gate bipolar transistor (IGBT).

[0038] Similarly, an inductor L1 is connected in series between the drain of the MOS transistor and the cathode of the photoemitting diode PD. Its function is the same as in the above embodiment, and will not be described again here.

[0039] In a further embodiment, the automatic optical power control circuit of this utility model further includes a power supply filtering module composed of a fifth resistor R5, a first capacitor C1, and a second capacitor C2. One end of the fifth resistor R5 is connected to the power supply, grounded through the first capacitor C1, and grounded through the second capacitor C2. The other end of the fifth resistor R5 is connected to the cathode of the photodiode LD and the anode of the photoemitting diode PD. The 3V3 power supply voltage is filtered through the fifth resistor R5, the first capacitor C1, and the second capacitor C2 to stabilize the power supply voltage of the photodiode LD and the photoemitting diode PD.

[0040] The load 10 is the sixth resistor R6, and the resistance value of the sixth resistor R6 is equal to that of the first resistor R1, which can simplify the setting of the operational amplifier U1.

[0041] To better understand this utility model, the following is combined with... Figure 2 The working principle of the automatic optical power control circuit of this utility model will be described in detail by giving specific examples:

[0042] Assuming the photodiode PD uses an LD light source of model HGLD-635TO5.6 with a wavelength of 635nm (hereinafter referred to as LD tube), and the average optical power of the human eye laser safety CLSS2 standard is less than 1mW, considering the actual application process, an optical lens will be added to focus the light. The optical power attenuation caused by the optical lens is about 50%. In this example, the optical power of the photodiode PD is calculated to be 1-3mW.

[0043] According to the datasheet for the HGLD-635TO5.6 laser diode, the operating current of the LD is 22-48mA, and the slope efficiency SE = 0.9W / A = 0.9mw / mA (calculated based on typical values).

[0044] When the optical power is 1mW, the corresponding current of the LD tube is 22mA + 1mW / 0.9mW / mA = 23.1mA;

[0045] When the optical power is 3mW, the corresponding current of the LD tube is 22mA + 3mW / 0.9mW / mA = 25.3mA;

[0046] Let the output voltage of operational amplifier U1 be Vout, the voltage at the non-inverting output terminal of operational amplifier U1 be Vx, and the voltage at the inverting input terminal of operational amplifier U1 be Vy;

[0047] Where Ib = (Vout - 0.7V) / R4, and R4 = 680 ohms.

[0048] Optical power is 1mW: Vout = 1.01V;

[0049] Optical power is 3mW: Vout = 1.04V

[0050] Based on the virtual short of operational amplifier U1:

[0051] When the optical power is 1mW, the target DAC voltage (such as the target voltage value output by the digital-to-analog converter, used to set the average optical power of the LD tube) is set to Vx = Vy = 0.655V;

[0052] When the optical power is 3mW, the target DAC voltage is set to Vx = Vy = 0.97V;

[0053] As the temperature rises, the current of the LD transistor decreases, resulting in a decrease in its optical power. Since the current of the PD transistor changes with the optical power of the LD, the current of the PD transistor also decreases, i.e., Vf decreases, and consequently Vy decreases (at this point, Vy is less than Vx). The voltage at the inverting input of operational amplifier U1 decreases, thus increasing the output voltage Vout of operational amplifier U1. Therefore, the base current IB of the current regulating transistor Q1 increases, further increasing the current of the LD transistor. When the current of the LD transistor increases to the point where Vy = Vx, equaling the target DAC voltage, reaching a new stable state, the automatic optical power control circuit ceases adjustment. It is evident that after the temperature rises, the automatic optical power control circuit, composed of only a few electronic components such as operational amplifier U1, load I0, first resistor R1, and third resistor R3, regulates the base current of the current regulating transistor Q1 to achieve power stability of the LD transistor.

[0054] This utility model also provides an electronic device, including an automatic optical power control circuit, which is connected to a light emitting diode and a light receiving diode. Since the circuit structure and operation of the automatic optical power control circuit have been described in detail above, they will not be repeated here.

[0055] In summary, this invention adjusts the current emitted by the light-emitting diode by changing the difference between the load voltage and the reference voltage as the light power received by the light-receiving diode changes with the output power of the light-emitting diode. When the difference is zero, the light power of the light-emitting diode is set to a preset level. This ensures that the light power of the light-emitting diode remains constant despite temperature changes, automatically adjusting its power to maintain a preset level and meeting the requirements of continuous and stable ITOF ranging.

[0056] Meanwhile, this invention employs an operational amplifier to monitor and adjust the difference between the load voltage and the reference voltage in real time, enabling precise optical power control and avoiding optical power fluctuations caused by environmental changes. This automates the optical power adjustment process, eliminating the need for manual intervention and reducing operational complexity and the possibility of human error. Furthermore, by monitoring changes in the current of the optical receiving diode using an operational amplifier and a few resistors, the current of the transmitting diode is automatically adjusted. Compared to existing methods that rely on DSP analysis and processing, this significantly reduces the complexity of software design.

[0057] Furthermore, the automatic optical power control circuit of this invention can adapt to different working environments and conditions, especially in situations with large temperature variations, it can still maintain the stable performance of the light emitting diode.

[0058] This invention can also improve the reliability of the entire system by real-time monitoring and adjustment of optical power, reduce equipment failures or performance degradation caused by unstable optical power, and avoid unnecessary energy waste by precisely controlling optical power, thereby achieving energy-saving effects.

[0059] It is understood that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of this utility model, and all such substitutions or changes should fall within the protection scope of the appended claims of this utility model.

Claims

1. An automatic control circuit for the optical power of a light-emitting diode, characterized in that, The control circuit includes an operational amplifier, a load, a first resistor, and a current regulating transistor; The anode of the light-emitting diode is connected to the cathode of the light-receiving diode and the power supply. The load is connected between the anode of the light-receiving diode and ground. The non-inverting input of the operational amplifier is connected to the reference voltage. The inverting input of the operational amplifier is connected to the non-ground terminal of the load and is also connected to the output of the operational amplifier through a first resistor. The output of the operational amplifier is also connected to the control terminal of the current regulating transistor. The output of the current regulating transistor is connected to the cathode of the light-emitting diode.

2. The automatic optical power control circuit according to claim 1, characterized in that, It also includes a second resistor and a third resistor, the second resistor being connected in series between the non-inverting input of the operational amplifier and the reference voltage, and the third resistor being connected in series between the inverting input of the operational amplifier and the non-ground terminal of the load.

3. The automatic optical power control circuit according to claim 2, characterized in that, The resistance values ​​of the second resistor and the third resistor are equal.

4. The automatic optical power control circuit according to claim 1, characterized in that, It also includes a fourth resistor, which is connected in series between the output of the operational amplifier and the control terminal of the current regulating transistor.

5. The automatic optical power control circuit according to claim 1, characterized in that, The current regulating transistor is an NPN transistor. The base of the NPN transistor is the control terminal of the current regulating transistor and is connected to the output terminal of the operational amplifier. Its collector is the output terminal of the current regulating transistor and is connected to the cathode of the photoemitting diode. Its emitter is grounded.

6. The automatic optical power control circuit according to claim 1, characterized in that, The current regulating transistor is an NMOS transistor. The gate of the NMOS transistor is the control terminal of the current regulating transistor and is connected to the output terminal of the operational amplifier. Its drain is the output terminal of the current regulating transistor and is connected to the cathode of the photoemitting diode. Its source is grounded.

7. The automatic optical power control circuit according to claim 5, characterized in that, An inductor is connected in series between the collector of the transistor and the cathode of the photoemitting diode.

8. The automatic optical power control circuit according to claim 6, characterized in that, An inductor is connected in series between the drain of the MOS transistor and the cathode of the photoemitting diode.

9. The automatic optical power control circuit according to claim 1, characterized in that, It also includes a power filtering module consisting of a fifth resistor, a first capacitor, and a second capacitor. One end of the fifth resistor is connected to the power supply, grounded through the first capacitor, and grounded through the second capacitor. The other end of the fifth resistor is connected to the cathode of the photoreceiving diode and the anode of the photoemitting diode.

10. The automatic optical power control circuit according to any one of claims 1-9, characterized in that, The load is a sixth resistor, and the resistance value of the sixth resistor is equal to that of the first resistor.

11. An electronic device, characterized in that, It includes the automatic optical power control circuit as described in any one of claims 1-10, wherein the automatic optical power control circuit is connected to the optical emitting diode and the optical receiving diode.

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