Double-loop negative feedback regulation circuit

Abstract

The invention discloses a double-loop negative feedback regulation circuit, which realizes accurate and real-time closed-loop regulation of the brightness of a light-emitting element by constructing a double-loop negative feedback architecture in which a first operational amplifier circuit, a second operational amplifier circuit, a sampling circuit and a photosensitive circuit work cooperatively. The problems that the brightness of a traditional driving circuit is easily interfered and the adjustment precision is insufficient are solved, and the brightness of a light-emitting element is ensured to stably meet the use requirement.

Description

Technical Field

[0001] This invention belongs to the field of LED technology and relates to a dual-loop negative feedback regulation circuit. Background Technology

[0002] In existing technologies, the driving control circuits for light-emitting elements such as LEDs generally adopt a single constant current source driving scheme. The core design idea is to stabilize the operating current flowing through the light-emitting element through a constant current source circuit to control its illumination. However, such traditional driving circuits can only control the "on / off" state of the light-emitting element or simply stabilize the operating current; they cannot sense the actual brightness of the light-emitting element in real time, nor can they perform precise closed-loop adjustment according to brightness requirements. Specifically, because the brightness of the light-emitting element is affected by factors such as power supply voltage fluctuations, element aging, and ambient temperature changes, even if the current remains stable, its actual brightness may deviate. Traditional constant current source driving circuits lack a real-time brightness detection and feedback adjustment mechanism, resulting in the brightness of the light-emitting element failing to accurately match actual usage requirements. This problem has become a key bottleneck restricting the application of LEDs and other light-emitting elements in high-precision dimming scenarios. Summary of the Invention

[0003] The present invention provides a dual-loop negative feedback adjustment circuit. By constructing a dual-loop negative feedback architecture in which a first operational amplifier circuit, a second operational amplifier circuit, a sampling circuit and a photosensitive circuit work together, the brightness of the light-emitting element is accurately and in real time closed-loop adjusted. This overcomes the problems of brightness being easily interfered with and insufficient adjustment accuracy in traditional driving circuits, and ensures that the brightness of the light-emitting element is stable and meets the usage requirements.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A dual-loop negative feedback regulation circuit includes a power supply and a light-emitting element, and also includes a first operational amplifier circuit, a second operational amplifier circuit, a sampling circuit and a photosensitive circuit. One end of the light-emitting element is connected to the power supply, and the other end of the light-emitting element is connected to the output terminal of the first operational amplifier circuit and the input terminal of the photosensitive circuit, respectively. The photosensitive circuit is located on one side of the light-emitting element. The input terminal of the sampling circuit is connected to the control terminal of the first operational amplifier circuit, and the output terminal of the sampling circuit is connected to the input terminal of the first operational amplifier circuit. The output terminal of the photosensitive circuit is connected to the input terminal of the second operational amplifier circuit, and the output terminal of the second operational amplifier circuit is connected to the input terminal of the first operational amplifier circuit.

[0005] Furthermore, the first operational amplifier circuit includes a first operational amplifier and a first switching transistor; The inverting input terminal of the first operational amplifier is connected to the output terminal of the sampling circuit and the output terminal of the second operational amplifier circuit; The output terminal of the first operational amplifier is connected to the base of the first switching transistor, the collector of the first switching transistor is connected to the light-emitting element, and the emitter of the first switching transistor is connected to the input terminal of the sampling circuit. The non-inverting input of the first operational amplifier is used to receive a reference potential signal.

[0006] Furthermore, it also includes a potentiometer for providing a reference potential signal; One end of the potentiometer is connected to the power supply, the other end of the potentiometer is connected to the ground terminal, and the sliding terminal of the potentiometer is connected to the non-inverting input terminal of the first operational amplifier.

[0007] Furthermore, the first operational amplifier circuit also includes a first resistor; One end of the first resistor is connected to the output terminal of the first operational amplifier, and the other end of the first resistor is connected to the base of the first switching transistor.

[0008] Furthermore, the second operational amplifier circuit includes a second operational amplifier; The non-inverting input of the second operational amplifier is connected to the output of the photosensitive circuit; The output terminal of the second operational amplifier is connected to the inverting input terminal of the first operational amplifier.

[0009] Furthermore, the second operational amplifier circuit also includes a second resistor and a third resistor; One end of the second resistor is connected to the inverting input terminal of the second operational amplifier, and the other end of the second resistor is connected to the output terminal of the second operational amplifier; One end of the third resistor is connected to the inverting input of the second operational amplifier, and the other end of the third resistor is connected to the ground terminal.

[0010] Furthermore, the second operational amplifier circuit also includes a fourth resistor; One end of the fourth resistor is connected to the output terminal of the second operational amplifier, and the other end of the fourth resistor is connected to the inverting input terminal of the first operational amplifier.

[0011] Furthermore, the sampling circuit includes a sixth resistor and a seventh resistor; One end of the sixth resistor is connected to the emitter of the first switching transistor, and the other end of the sixth resistor is connected to the ground terminal; One end of the seventh resistor is connected to the emitter of the first switching transistor, and the other end of the seventh resistor is connected to the inverting input of the first operational amplifier.

[0012] Furthermore, the photosensitive circuit includes a photodiode; The positive terminal of the photodiode is connected to the non-inverting input terminal of the second operational amplifier, and the negative terminal of the photodiode is connected to the output terminal of the first operational amplifier.

[0013] Furthermore, the photosensitive circuit also includes a fifth resistor; One end of the fifth resistor is connected to the positive terminal of the photodiode, and the other end of the fifth resistor is connected to the ground terminal.

[0014] The beneficial effects of this invention are as follows: This application breaks through the limitation of traditional single constant current source drive circuits, which can only stabilize current and cannot sense actual changes in brightness. It constructs two negative feedback loops—one for current and one for brightness—through a sampling circuit and a photosensitive circuit, respectively. Both feedback signals ultimately converge at the first operational amplifier circuit, forming a collaborative adjustment mechanism. The photosensitive circuit is specifically located on the side of the light-emitting element, enabling it to directly and accurately capture the actual brightness of the element, avoiding interference from ambient light and other noise. It converts the physical brightness signal into an electrical signal and transmits it to the second operational amplifier circuit for processing. Simultaneously, the sampling circuit collects the operating current of the first operational amplifier circuit and forms a current feedback signal, providing a basic current reference for brightness adjustment. The synergistic effect of these two signals allows the first operational amplifier circuit to stabilize the operating current of the light-emitting element through the current feedback signal, laying the foundation for brightness adjustment. It also allows it to correct brightness deviations caused by factors such as power supply voltage fluctuations, element aging, and ambient temperature changes in real time through the brightness feedback signal. This achieves dual control of current stability and brightness calibration, completely solving the core problem in traditional circuits where the current is stable but the brightness may still deviate from the required level, significantly improving the accuracy of brightness adjustment for the light-emitting element.

[0015] Furthermore, each circuit module forms a complete closed loop through explicit electrical connections. The signal transmission path is direct and without redundancy. When a slight deviation occurs in the brightness of the light-emitting element, the photosensitive circuit and sampling circuit can quickly capture the signal change. After processing by the second operational amplifier circuit, the signal is promptly fed back to the first operational amplifier circuit. The first operational amplifier circuit can quickly adjust the output signal to ensure the real-time performance of brightness adjustment and avoid the accumulation of deviations. At the same time, the entire circuit achieves its core functions through a reasonable combination of conventional electronic components, without complex customized parts. Its compact structure and clear connection logic reduce the difficulty of circuit implementation and manufacturing costs, and facilitate subsequent installation, debugging, and maintenance. It possesses strong practicality and broad application value. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the framework structure of the present invention.

[0017] Figure 2 This is a schematic diagram of the circuit structure of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. It should be understood that this application is not limited to the exemplary embodiments disclosed herein. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0019] In the description of this invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., 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 this invention and simplifying the description, and do not 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 this invention.

[0020] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0021] In the embodiments of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., 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. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] This invention provides an appendix Figures 1-2 In this embodiment of the invention, a dual-loop negative feedback regulation circuit includes a power supply and a light-emitting element D1, and also includes a first operational amplifier circuit, a second operational amplifier circuit, a sampling circuit and a photosensitive circuit. One end of the light-emitting element D1 is connected to the power supply, and the other end of the light-emitting element D1 is connected to the output terminal of the first operational amplifier circuit and the input terminal of the photosensitive circuit, respectively. The photosensitive circuit is located on one side of the light-emitting element D1. The input terminal of the sampling circuit is connected to the control terminal of the first operational amplifier circuit, and the output terminal of the sampling circuit is connected to the input terminal of the first operational amplifier circuit. The output terminal of the photosensitive circuit is connected to the input terminal of the second operational amplifier circuit, and the output terminal of the second operational amplifier circuit is connected to the input terminal of the first operational amplifier circuit.

[0023] The dual-loop negative feedback regulation circuit of this embodiment includes a power supply, a light-emitting element D1, a first operational amplifier circuit, a second operational amplifier circuit, a sampling circuit, and a photosensitive circuit. Each component is an independent functional circuit / component. The power supply is a DC power supply used to provide operating power to the entire dual-loop negative feedback regulation circuit and the light-emitting element D1. The light-emitting element D1 is an electro-optical conversion element, preferably an LED light-emitting diode, which can convert the electrical energy provided by the power supply into light energy. The first operational amplifier circuit is the main control module of the entire regulation circuit, used to output drive signals to control the working state of the light-emitting element D1 and receive feedback signals to complete the regulation action. The second operational amplifier circuit is a brightness feedback signal processing module, used to receive the detection signal from the photosensitive circuit and transmit it to the first operational amplifier circuit. The sampling circuit is a current detection feedback module, used to collect the operating current of the first operational amplifier circuit and form a current feedback signal. The photosensitive circuit is a brightness detection feedback module, used to detect the actual luminous brightness of the light-emitting element D1 and form a brightness feedback signal.

[0024] In this embodiment, one end of the light-emitting element D1 is electrically connected to the positive terminal of the power supply, and the other end of the light-emitting element D1 is electrically connected to both the output terminal of the first operational amplifier circuit and the input terminal of the photosensitive circuit. The on / off state of the light-emitting element D1 and the magnitude of its operating current are controlled by the drive signal output by the first operational amplifier circuit. The photosensitive circuit is fixedly disposed on one side of the light-emitting element D1, and the detection terminal of the photosensitive circuit faces the light-emitting surface of the light-emitting element D1, ensuring accurate detection of the actual luminous brightness of the light-emitting element D1 and avoiding interference from ambient light and other stray light.

[0025] The input terminal of the sampling circuit is electrically connected to the control terminal of the first operational amplifier circuit. The detection terminal of the sampling circuit can collect the current signal of the control terminal of the first operational amplifier circuit in real time. The output terminal of the sampling circuit is electrically connected to the input terminal of the first operational amplifier circuit. After the sampling circuit converts the collected current signal into an electrical feedback signal, it transmits it to the input terminal of the first operational amplifier circuit through its output terminal, forming a first negative feedback adjustment loop (current negative feedback loop). The first operational amplifier circuit can adjust the drive signal parameters of its output terminal according to the current feedback signal.

[0026] The output terminal of the photosensitive circuit is electrically connected to the input terminal of the second operational amplifier circuit. After the photosensitive circuit converts the detected brightness signal of the light-emitting element D1 into an electrical detection signal, it transmits it to the input terminal of the second operational amplifier circuit through its output terminal. The second operational amplifier circuit processes the electrical detection signal and then transmits it to the input terminal of the first operational amplifier circuit through its output terminal. Thus, the photosensitive circuit, the second operational amplifier circuit, and the first operational amplifier circuit form a second negative feedback adjustment loop (brightness negative feedback loop).

[0027] In this embodiment, the input terminal of the first operational amplifier circuit is a dual signal receiving terminal, which can simultaneously receive the current feedback signal transmitted by the sampling circuit and the brightness feedback signal transmitted by the second operational amplifier circuit. The first operational amplifier circuit dynamically adjusts the driving signal at the output terminal according to the deviation between the two feedback signals and its own preset driving parameters, thereby changing the operating current of the light-emitting element D1 and realizing precise and real-time adjustment of the brightness of the light-emitting element D1.

[0028] The dual-loop negative feedback adjustment circuit in this embodiment operates as follows: After the power supply is turned on, it powers the entire circuit and the light-emitting element D1. The first operational amplifier circuit outputs an initial drive signal to the light-emitting element D1, and the light-emitting element D1 emits light of corresponding brightness according to the initial drive signal. At the same time, the sampling circuit collects the current signal at the control terminal of the first operational amplifier circuit in real time, converts it into a current feedback signal, and transmits it to the input terminal of the first operational amplifier circuit to form current negative feedback. The photosensitive circuit detects the actual light emission brightness of the light-emitting element D1 in real time, converts it into an electrical detection signal, and transmits it to the second operational amplifier circuit. After processing by the second operational amplifier circuit, it forms a brightness feedback signal, which is transmitted to the input terminal of the first operational amplifier circuit to form brightness negative feedback. The first operational amplifier circuit compares the collected current feedback signal and brightness feedback signal with its own preset parameters. If there is a deviation between the actual current / brightness and the preset value, the first operational amplifier circuit will dynamically adjust the drive signal parameters at the output terminal to change the operating current of the light-emitting element D1 until the actual brightness of the light-emitting element D1 is consistent with the preset brightness. The above process continues to achieve closed-loop precise adjustment of the brightness of the light-emitting element D1.

[0029] The first operational amplifier circuit includes a first operational amplifier U1 and a first switching transistor Q1; The inverting input terminal of the first operational amplifier U1 is connected to the output terminal of the sampling circuit and the output terminal of the second operational amplifier circuit; The output terminal of the first operational amplifier U1 is connected to the base of the first switching transistor Q1, the collector of the first switching transistor Q1 is connected to the light-emitting element D1, and the emitter of the first switching transistor Q1 is connected to the input terminal of the sampling circuit. The non-inverting input of the first operational amplifier U1 is used to receive the reference potential signal.

[0030] The dual-loop negative feedback regulation circuit of this embodiment includes a power supply, a light-emitting element D1, a first operational amplifier circuit, a second operational amplifier circuit, a sampling circuit, and a photosensitive circuit. The first operational amplifier circuit includes a first operational amplifier U1 and a first switching transistor Q1. The first operational amplifier U1 is a linear integrated operational amplifier adapted for real-time comparison, adjustment, and output of analog electrical signals. The first switching transistor Q1 can be an NPN transistor with three electrodes: a base, a collector, and an emitter. The base is the controlled terminal, and the conduction degree between the collector and the emitter can be adjusted by receiving electrical signals, thereby controlling the magnitude of the loop current. The two together constitute the core control structure of the first operational amplifier circuit.

[0031] In this embodiment, the inverting input terminal of the first operational amplifier U1 is a dual-signal input terminal, electrically connected to both the output terminal of the sampling circuit and the output terminal of the second operational amplifier circuit. It can simultaneously receive the current feedback signal transmitted by the sampling circuit and the brightness feedback signal transmitted by the second operational amplifier circuit. This inverting input terminal is the core signal comparison terminal of the first operational amplifier U1, where all feedback signals converge for adjustment calculations. The output terminal of the first operational amplifier U1 is electrically connected to the base of the first switching transistor Q1. The voltage regulation signal output by the first operational amplifier U1 directly acts on the base of the first switching transistor Q1, and the voltage signal received at the base... The amplitude determines the conduction level of the first switch Q1; the collector of the first switch Q1 is electrically connected to the light-emitting element D1, providing a transmission path for the operating current of the light-emitting element D1; the emitter of the first switch Q1 is electrically connected to the input terminal of the sampling circuit, and the sampling circuit can accurately acquire the actual current signal flowing through the first switch Q1 through this connection terminal; the non-inverting input terminal of the first operational amplifier U1 is a reference signal receiving terminal, used to receive an externally input reference potential signal, which is a DC voltage signal, and its amplitude provides a reference for the brightness adjustment of the light-emitting element D1, determining the target brightness value of the light-emitting element D1.

[0032] In this embodiment, the operation of the first operational amplifier circuit is as follows: the first operational amplifier U1 uses the reference potential signal received at the non-inverting input terminal as the brightness adjustment reference, performs real-time difference comparison calculation between the current feedback signal and the brightness feedback signal synchronously received at the inverting input terminal and the reference signal, and outputs the corresponding voltage regulation signal to the base of the first switching transistor Q1 according to the calculation result; when the amplitude of the feedback signal is lower than the amplitude of the reference potential signal, the first operational amplifier U1 increases the voltage signal at the output terminal, which increases the base current of the first switching transistor Q1, reduces the conduction internal resistance between the collector and emitter, and allows the light to flow through the light-emitting element. As the operating current of D1 increases, the brightness of the light-emitting element D1 increases. When the amplitude of the feedback signal is higher than the amplitude of the reference potential signal, the first operational amplifier U1 reduces the voltage signal at its output terminal, causing the base current of the first switching transistor Q1 to decrease, the on-resistance between the collector and emitter to increase, the operating current flowing through the light-emitting element D1 to decrease, and the brightness of the light-emitting element D1 to decrease. When the amplitude of the feedback signal is the same as the amplitude of the reference potential signal, the first operational amplifier U1 keeps the output voltage signal unchanged, the conduction degree of the first switching transistor Q1 is stable, the operating current of the light-emitting element D1 is constant, and the brightness is maintained at the target value.

[0033] In this embodiment, the input terminal of the sampling circuit is connected to the emitter of the first switching transistor Q1, which can directly collect the conduction current between the collector and emitter of the first switching transistor Q1. This current is in the same loop as the operating current flowing through the light-emitting element D1, ensuring the authenticity and accuracy of the current feedback signal. The output terminal of the second operational amplifier circuit is directly connected to the inverting input terminal of the first operational amplifier U1, so that the brightness feedback signal does not need to go through other intermediate components and directly participates in the signal comparison calculation of the first operational amplifier U1, ensuring the real-time performance of brightness adjustment.

[0034] It also includes a potentiometer R0 for providing a reference potential signal; One end of the potentiometer R0 is connected to the power supply, the other end of the potentiometer R0 is connected to the ground terminal, and the sliding terminal of the potentiometer R0 is connected to the non-inverting input terminal of the first operational amplifier U1.

[0035] The dual-loop negative feedback adjustment circuit of this embodiment includes a power supply, a light-emitting element D1, a first operational amplifier circuit, a second operational amplifier circuit, a sampling circuit, and a photosensitive circuit. The first operational amplifier circuit includes a first operational amplifier U1 and a first switching transistor Q1, and also includes a potentiometer R0 for providing a reference potential signal. The potentiometer R0 is a linear DC voltage divider potentiometer R0, which is suitable for the DC power supply environment of this circuit. It has two fixed terminals and one adjustable sliding terminal. By adjusting the position of the sliding terminal, the resistance value between the two fixed terminals and the sliding terminal can be changed, thereby realizing precise voltage division of DC voltage and providing an adjustable DC reference potential signal for the first operational amplifier U1. This reference potential signal serves as the reference value for adjusting the brightness of the light-emitting element D1 and directly determines the target brightness of the light-emitting element D1.

[0036] In this embodiment, one fixed terminal of the potentiometer R0 is electrically connected to the positive terminal of the power supply to obtain the DC operating voltage of the power supply; the other fixed terminal of the potentiometer R0 is electrically connected to the ground terminal to form a complete voltage divider circuit; the sliding terminal of the potentiometer R0 is directly electrically connected to the non-inverting input terminal of the first operational amplifier U1, so that the DC voltage signal obtained after voltage division by the potentiometer R0 is directly transmitted to the non-inverting input terminal of the first operational amplifier U1 as a reference potential signal, and this connection has no intermediate relay components, avoiding attenuation or interference of the reference potential signal during transmission and ensuring the accuracy of the signal.

[0037] In this embodiment, potentiometer R0 is used to divide and output an adjustable reference potential signal. Potentiometer R0 is connected to the positive terminal of the power supply and the ground terminal respectively through two fixed terminals, forming a DC voltage divider circuit. Its sliding end can slide linearly along the resistive body. When the sliding end moves towards the fixed terminal of the positive terminal of the power supply, the resistance between the sliding end and the ground terminal increases, and the resistance between the sliding end and the positive terminal of the power supply decreases. The DC voltage value output by the sliding end increases, and the amplitude of the reference potential signal transmitted to the non-inverting input terminal of the first operational amplifier U1 increases accordingly. When the sliding end moves towards the fixed terminal of the ground terminal, the resistance between the sliding end and the ground terminal decreases, and the resistance between the sliding end and the positive terminal of the power supply increases. The DC voltage value output by the sliding end decreases, and the amplitude of the reference potential signal transmitted to the non-inverting input terminal of the first operational amplifier U1 decreases accordingly. By manually adjusting the mechanical position of the sliding end, the amplitude of the reference potential signal can be continuously adjusted steplessly within the power supply voltage range, thereby realizing the manual setting of the target brightness of the light-emitting element D1.

[0038] In this embodiment, the reference potential signal output by potentiometer R0 provides a stable brightness adjustment reference for the first operational amplifier U1. This voltage divider signal supply method has the characteristics of strong anti-interference and high stability. The voltage divider circuit of potentiometer R0 is independent of the current negative feedback loop and the brightness negative feedback loop of the circuit. Its output reference potential signal will not be affected by the fluctuation of the feedback signal in the circuit, ensuring that the first operational amplifier U1 always has a fixed and accurate reference signal for comparison with the feedback signal. At the same time, the selection of potentiometer R0 is compatible with the DC voltage specification of the power supply, ensuring that the amplitude of its output reference potential signal is within the normal operating voltage range of the first operational amplifier U1, avoiding abnormal operation of the first operational amplifier U1 due to the signal amplitude exceeding the threshold.

[0039] In this embodiment, after the reference potential signal is directly input to the non-inverting input terminal of the first operational amplifier U1 through the potentiometer R0, the first operational amplifier U1 uses the reference potential signal as the brightness adjustment reference, performs real-time difference comparison calculation with the current feedback signal and brightness feedback signal received at the inverting input terminal, and adjusts the voltage signal output to the base of the first switching transistor Q1 according to the calculation result, so as to realize the adjustment action of the brightness of the light-emitting element D1 approaching the target brightness corresponding to the reference potential signal.

[0040] The first operational amplifier circuit also includes a first resistor R1; One end of the first resistor R1 is connected to the output terminal of the first operational amplifier U1, and the other end of the first resistor R1 is connected to the base of the first switching transistor Q1.

[0041] The dual-loop negative feedback regulation circuit of this embodiment includes a power supply, a light-emitting element D1, a first operational amplifier circuit, a second operational amplifier circuit, a sampling circuit, and a photosensitive circuit. The first operational amplifier circuit includes a first operational amplifier U1 and a first switching transistor Q1, and also includes a first resistor R1. The first resistor R1 can be a metal film fixed resistor adapted to DC low-voltage circuits. This resistor has the characteristics of high resistance accuracy, small temperature drift, and stable overcurrent capability. Its resistance value is precisely selected according to the DC operating voltage of the power supply and the maximum allowable base current of the first switching transistor Q1. It is a passive current limiting protection component, which does not require an additional power supply. It achieves current limiting only through series connection. Its core function is to protect the first switching transistor Q1 and the first operational amplifier U1 and prevent the components from burning out due to base overcurrent.

[0042] One end of the first resistor R1 is directly electrically connected to the output terminal of the first operational amplifier U1, and the other end is directly electrically connected to the base of the first switching transistor Q1. The first resistor R1 is connected in series in the electrical signal transmission circuit between the output terminal of the first operational amplifier U1 and the base of the first switching transistor Q1. It is the only series component in this transmission circuit, without any intermediate relay parts, which ensures the directness and effectiveness of the current limiting protection function, while avoiding additional attenuation or interference of the electrical signal during transmission.

[0043] In this embodiment, the first operational amplifier U1 outputs a corresponding voltage regulation signal based on the reference potential signal at the non-inverting input terminal and the feedback signal at the inverting input terminal. This signal must first flow through the first series resistor R1 during its transmission to the base of the first switching transistor Q1. According to Ohm's law, the first series resistor R1 will impose a fixed limit on the current in the circuit, strictly controlling the current flowing into the base of the first switching transistor Q1 within its rated operating current range. Even if there are abnormal situations such as slight fluctuations in the power supply voltage or a sudden surge in the output signal of the first operational amplifier U1, the first resistor R1 can still achieve voltage division and current limiting through its own resistance value, avoiding excessive current flowing into the base of the first switching transistor Q1 and causing electrode breakdown and component burnout.

[0044] While achieving current limiting protection, the resistance value of the first resistor R1 is precisely selected and designed, and its own voltage drop during operation is negligible. After the voltage regulation signal output by the first operational amplifier U1 is transmitted through the first resistor R1, the amplitude and trend do not change significantly, and it can still accurately control the current of the base of the first switching transistor Q1, thereby achieving precise control of the conduction degree between the collector and emitter of the first switching transistor Q1.

[0045] In this embodiment, the addition of the first resistor R1 can also improve the working stability and service life of the circuit: at the moment of power-on startup of the circuit, the power supply will generate a momentary current surge. The first resistor R1 can effectively buffer this surge and prevent the momentary large current from flowing directly into the base of the first switching transistor Q1. At the same time, the small temperature drift characteristic of the metal film resistor ensures that its resistance remains stable within the temperature range of the circuit operation, and the current limiting protection effect will not weaken with temperature changes, so that the working state of the first operational amplifier circuit always remains stable.

[0046] The second operational amplifier circuit includes a second operational amplifier U2; The non-inverting input of the second operational amplifier U2 is connected to the output of the photosensitive circuit; The output terminal of the second operational amplifier U2 is connected to the inverting input terminal of the first operational amplifier U1.

[0047] The dual-loop negative feedback adjustment circuit of this embodiment includes a power supply, a light-emitting element D1, a first operational amplifier circuit, a second operational amplifier circuit, a sampling circuit, and a photosensitive circuit. The first operational amplifier circuit includes a first operational amplifier U1 and a first switching transistor Q1, and the second operational amplifier circuit includes a second operational amplifier U2. The second operational amplifier U2 is a high-input-impedance linear integrated operational amplifier, adapted to the reception and processing of the weak analog electrical signal output by the photosensitive circuit in this circuit. It has three core signal terminals: a non-inverting input terminal, an inverting input terminal, and an output terminal, without any additional redundant functional terminals. Its core function is to receive the brightness detection electrical signal transmitted by the photosensitive circuit, linearly amplify the signal, and accurately transmit it to the inverting input terminal of the first operational amplifier U1, ensuring that the brightness feedback signal can effectively participate in the adjustment operation of the first operational amplifier circuit. Moreover, the operational amplifier is a DC low-voltage adapted type, with its operating voltage provided by the power supply, matching the power supply environment of the entire circuit.

[0048] The non-inverting input of the second operational amplifier U2 is directly electrically connected to the output of the photosensitive circuit without any intermediate relay components or transmission parts. This ensures that the brightness detection signal output by the photosensitive circuit can be transmitted to the second operational amplifier U2 without attenuation or interference. Furthermore, the high input impedance of the non-inverting input effectively avoids the second operational amplifier U2 from causing a load on the signal of the photosensitive circuit, thus ensuring the authenticity of the brightness detection signal. The output terminal of the second operational amplifier U2 is directly electrically connected to the inverting input terminal of the first operational amplifier U1. The brightness feedback electrical signal processed by the second operational amplifier U2 can be directly transmitted to the signal comparison core terminal of the first operational amplifier U1, where it merges with the current feedback signal transmitted by the sampling circuit and participates in the difference comparison calculation of the first operational amplifier U1 to ensure the real-time performance of brightness feedback adjustment.

[0049] In this embodiment, the photosensitive circuit detects the actual luminous brightness of the light-emitting element D1 in real time and converts the physical brightness signal into a corresponding weak analog electrical signal, which is then transmitted to the non-inverting input of the second operational amplifier U2 through its output terminal. Based on its own linear amplification characteristics, the second operational amplifier U2 linearly amplifies the input weak brightness detection signal proportionally, increasing the signal amplitude to a range that the first operational amplifier U1 can accurately identify and process. During the amplification process, the signal trend remains consistent with the original brightness detection signal, without signal distortion, phase shift, or other problems. The amplified brightness feedback electrical signal is directly transmitted to the inverting input of the first operational amplifier U1 through the output terminal of the second operational amplifier U2, serving as the core signal of the brightness negative feedback loop. Together with the current feedback signal, it serves as the actual value reference signal of the first operational amplifier U1.

[0050] In this embodiment, the second operational amplifier U2, as the only core component of the second op-amp circuit, is the key to realizing weak signal amplification and accurate transmission in the brightness negative feedback loop. Its high input impedance design effectively solves the problems of weak and easily interfered output signals of the photosensitive circuit and easy overload, ensuring the originality of the brightness detection signal. The linear amplification characteristic ensures that the processed brightness feedback signal can truly reflect the actual brightness state of the light-emitting element D1, allowing the first operational amplifier U1 to accurately adjust the control signal of the first switching transistor Q1 according to the deviation between the signal and the reference potential signal, thereby realizing the negative feedback regulation of the brightness of the light-emitting element D1.

[0051] Meanwhile, the working state of the second operational amplifier U2 is synchronized with the working rhythm of the entire dual-loop negative feedback adjustment circuit. When the brightness of the light-emitting element D1 changes, the output signal of the photosensitive circuit changes accordingly. The second operational amplifier U2 will receive and amplify the changed signal in real time, and quickly transmit the changed brightness feedback signal to the first operational amplifier U1 to ensure the response speed of the brightness negative feedback adjustment, so that the brightness of the light-emitting element D1 can quickly return to the target value.

[0052] The second operational amplifier circuit also includes a second resistor R2 and a third resistor R3; One end of the second resistor R2 is connected to the inverting input terminal of the second operational amplifier U2, and the other end of the second resistor R2 is connected to the output terminal of the second operational amplifier U2; One end of the third resistor R3 is connected to the inverting input terminal of the second operational amplifier U2, and the other end of the third resistor R3 is connected to the ground terminal.

[0053] In this embodiment, the dual-loop negative feedback adjustment circuit includes a power supply, a light-emitting element D1, a first operational amplifier circuit, a second operational amplifier circuit, a sampling circuit, and a photosensitive circuit. The first operational amplifier circuit includes a first operational amplifier U1 and a first switching transistor Q1. The second operational amplifier circuit includes a second operational amplifier U2, and also includes a second resistor R2 and a third resistor R3. The second resistor R2 and the third resistor R3 are both metal film fixed resistors adapted for DC low-voltage circuits, which have the characteristics of high resistance accuracy, small temperature drift, and strong anti-interference. The resistance values ​​of the two are precisely designed according to the required amplification factor of the brightness detection signal. They are both passive components and do not require additional power supply. Through a specific connection with the second operational amplifier U2, they form a feedback bias network with in-phase proportional amplification. The core function is to jointly determine the fixed amplification factor of the second operational amplifier U2, and at the same time provide a stable DC bias potential for the inverting input terminal of the second operational amplifier U2, ensuring that it always works in the linear amplification region.

[0054] One end of the second resistor R2 is directly electrically connected to the inverting input terminal of the second operational amplifier U2, and the other end is directly electrically connected to the output terminal of the second operational amplifier U2. The second resistor R2 is a feedback resistor connected between the inverting input terminal and the output terminal of the second operational amplifier U2, without any intermediate relay components or transmission parts, ensuring the directness and effectiveness of the feedback signal transmission. One end of the third resistor R3 is directly electrically connected to the inverting input terminal of the second operational amplifier U2, and the other end is directly electrically connected to the ground terminal. The third resistor R3 is the ground bias resistor of the inverting input terminal of the second operational amplifier U2, and together with the second resistor R2, it forms a complete feedback bias circuit. This connection has no additional relay components, ensuring the stability of the potential of the inverting input terminal.

[0055] In this embodiment, the main functions of the second resistor R2 and the third resistor R3 are to determine the fixed amplification factor and provide DC bias. Together with the second operational amplifier U2, they form a classic non-inverting proportional amplifier circuit, and the amplification factor is a fixed value. The voltage amplification factor of the second operational amplifier U2 is uniquely determined by the resistance ratio of the second resistor R2 and the third resistor R3. This amplification factor is independent of the input signal of the photosensitive circuit, achieving precise proportional amplification of the brightness detection signal. This avoids distortion of the brightness feedback signal due to fluctuations in the amplification factor, ensuring that the amplified signal accurately reflects the actual brightness change of the light-emitting element D1. This is the fixed amplification factor. Furthermore, providing DC bias involves the third resistor R3 grounding a stable DC reference potential to the inverting input of the second operational amplifier U2. This keeps the potential at the inverting input dynamically balanced with the potential at the non-inverting input, ensuring that the second operational amplifier U2 always operates in the linear amplification region and avoiding signal clipping and distortion caused by the op-amp entering the saturation region. Even further, it suppresses self-oscillation. The second resistor R2 forms a negative feedback loop, effectively suppressing the self-oscillation generated by the second operational amplifier U2 during operation, improving the circuit's stability, and preventing noise and interference in the brightness feedback signal caused by oscillation.

[0056] In this embodiment, the photosensitive circuit detects the actual luminous brightness of the light-emitting element D1 in real time, converts the physical brightness signal into a weak analog electrical signal, and transmits it to the non-inverting input of the second operational amplifier U2. Under the action of the feedback bias network formed by the second resistor R2 and the third resistor R3, the second operational amplifier U2 linearly amplifies the weak brightness detection signal at the non-inverting input with a fixed amplification factor. During the amplification process, the trend of the signal is kept consistent with the original signal, without phase shift, amplitude distortion, or other problems. The precisely amplified brightness feedback electrical signal is transmitted to the inverting input of the first operational amplifier U1 through the output of the second operational amplifier U2, where it merges with the current feedback signal of the sampling circuit and participates in the difference comparison calculation of the first operational amplifier U1.

[0057] In this embodiment, the resistance values ​​of the second resistor R2 and the third resistor R3 are precisely matched to ensure that the amplification factor is adapted to the signal requirements of this circuit. This amplifies the weak signal from the photosensitive circuit to a range that the first operational amplifier U1 can accurately identify and process. Furthermore, the amplified signal amplitude is stable. Even if there are small voltage fluctuations in the power supply or changes in the ambient temperature, the resistance ratio between the two remains unchanged due to the small temperature drift characteristic of the metal film resistor. Consequently, the amplification factor of the second operational amplifier U2 will not change significantly, ensuring the accuracy and stability of the brightness feedback signal.

[0058] The second operational amplifier circuit also includes a fourth resistor R4; One end of the fourth resistor R4 is connected to the output terminal of the second operational amplifier U2, and the other end of the fourth resistor R4 is connected to the inverting input terminal of the first operational amplifier U1.

[0059] In this embodiment, the fourth resistor R4 can be a metal film fixed resistor adapted to DC low-voltage circuits, which has the characteristics of high resistance accuracy, small temperature drift, and stable overcurrent capability. Its resistance value is precisely selected according to the maximum output current of the second operational amplifier U2 and the maximum allowable input current of the inverting input terminal of the first operational amplifier U1. It is a passive current limiting and isolation component, which does not require an additional power supply. It achieves current limiting and signal isolation only through series connection. Its core function is to protect the inverting input terminal of the first operational amplifier U1 and prevent the first operational amplifier U1 from being damaged due to excessive output current of the second operational amplifier U2. At the same time, it isolates the signal interference between the two operational amplifiers and ensures the independence of the feedback signal.

[0060] One end of the fourth resistor R4 is directly electrically connected to the output terminal of the second operational amplifier U2, and the other end is directly electrically connected to the inverting input terminal of the first operational amplifier U1. The fourth resistor R4 is connected in series in the brightness feedback signal transmission loop between the output terminal of the second operational amplifier U2 and the inverting input terminal of the first operational amplifier U1. It is the only series component in this transmission loop, without any intermediate relay components or transmission parts, which ensures the directness and effectiveness of current limiting protection and signal isolation, while avoiding additional attenuation or distortion of the brightness feedback signal during transmission.

[0061] In this embodiment, the fourth resistor R4 is mainly used for current limiting protection and signal isolation. The second operational amplifier U2 linearly amplifies the brightness detection signal output from the photosensitive circuit and outputs a corresponding brightness feedback signal. This signal must flow through the series-connected fourth resistor R4 before being transmitted to the inverting input of the first operational amplifier U1. According to Ohm's law, the fourth resistor R4 provides a fixed limit on the current in the circuit, strictly controlling the current flowing into the inverting input of the first operational amplifier U1 within its rated allowable input current range. Even if there is a sudden surge in the output signal of the second operational amplifier U2 or fluctuations in the power supply voltage, this resistor will provide protection. In case of abnormal situations, the fourth resistor R4 can also achieve voltage division and current limiting through its own resistance value, preventing excessive current from flowing into the inverting input of the first operational amplifier U1 and causing internal circuit breakdown and component burnout. Furthermore, the inverting input of the first operational amplifier U1 simultaneously receives the current feedback signal transmitted by the sampling circuit and the brightness feedback signal transmitted by the second operational amplifier circuit. The fourth resistor R4 forms isolation between the transmission loops of the two feedback signals through series connection, avoiding mutual load or interference between the brightness feedback signal and the current feedback signal, ensuring that the amplitude and trend of the two feedback signals can accurately reflect the corresponding detection parameters (brightness / current), allowing the first operational amplifier U1 to perform difference comparison calculation based on two independent and accurate feedback signals, improving the accuracy of brightness adjustment. Based on the above embodiment, the low temperature drift characteristic of the fourth resistor R4 ensures that its resistance value remains stable within the temperature range of the circuit operation, and the current limiting and isolation effects will not weaken with temperature changes, ensuring that the transmission of the brightness feedback signal remains stable, further improving the working stability of the entire dual-loop negative feedback adjustment circuit.

[0062] In this embodiment, the photosensitive circuit detects the actual luminous brightness of the light-emitting element D1 in real time, converts the physical brightness signal into a weak analog electrical signal, and transmits it to the non-inverting input of the second operational amplifier U2. The second operational amplifier U2 linearly amplifies the weak signal and outputs the corresponding brightness feedback electrical signal. This brightness feedback electrical signal flows through the fourth resistor R4 in series, and after current limiting and isolation processing, it is accurately transmitted to the inverting input of the first operational amplifier U1. It merges with the current feedback signal transmitted by the sampling circuit and together serves as the actual value reference signal of the first operational amplifier U1, participating in the difference comparison calculation.

[0063] In this embodiment, the resistance value of the fourth resistor R4 is precisely selected and designed, and its voltage drop during operation is negligible. After the brightness feedback signal output by the second operational amplifier U2 is transmitted through the fourth resistor R4, the amplitude and trend do not change significantly. This does not affect the first operational amplifier U1's recognition and processing of the signal, and can also achieve effective current limiting and isolation, perfectly balancing signal transmission quality and component protection.

[0064] The sampling circuit includes a sixth resistor R6 and a seventh resistor R7; One end of the sixth resistor R6 is connected to the emitter of the first switch Q1, and the other end of the sixth resistor R6 is connected to the ground terminal; One end of the seventh resistor R7 is connected to the emitter of the first switching transistor Q1, and the other end of the seventh resistor R7 is connected to the inverting input of the first operational amplifier U1.

[0065] In this embodiment, the sampling circuit includes a sixth resistor R6 and a seventh resistor R7. Both the sixth resistor R6 and the seventh resistor R7 can be selected as metal film fixed resistors adapted to DC low-voltage circuits, which have the characteristics of high resistance accuracy, small temperature drift, and strong anti-interference. The resistance values ​​of the two are precisely selected according to the DC operating voltage of the power supply, the rated operating current of the first switching transistor Q1, and the signal recognition range of the first operational amplifier U1. They are both passive components and do not require additional power supply. Their core function is to cooperate in realizing the complete current detection function of "current acquisition-voltage conversion-feedback transmission". The resistance value design ensures that the amplitude of the converted voltage signal is within the linear processing range of the first operational amplifier U1, avoiding signal saturation or distortion.

[0066] Furthermore, one end of the sixth resistor R6 is directly electrically connected to the emitter of the first switching transistor Q1, and the other end is directly electrically connected to the ground terminal. The sixth resistor R6 is the grounding resistor of the current loop of the sampling circuit, without any intermediate relay components or transmission parts, ensuring the integrity and stability of the current acquisition loop. One end of the seventh resistor R7 is directly electrically connected to the emitter of the first switching transistor Q1, and the other end is directly electrically connected to the inverting input terminal of the first operational amplifier U1. The seventh resistor R7 is the current-to-voltage conversion and feedback transmission resistor, also without intermediate relay components, ensuring that the converted voltage feedback signal can be transmitted to the first operational amplifier U1 without attenuation or interference.

[0067] In this embodiment, the sampling circuit is mainly used for accurate current acquisition, linear conversion of voltage, and stable feedback transmission. The collector of the first switching transistor Q1 is connected to the light-emitting element D1, and its emitter is connected to the sampling circuit. The conduction current flowing through the collector-emitter junction of the first switching transistor Q1 is in the same loop as the operating current flowing through the light-emitting element D1 (ignoring line losses). Therefore, by acquiring the current at the emitter of the first switching transistor Q1, the actual operating current of the light-emitting element D1 can be indirectly obtained. The sixth resistor R6 forms a complete current loop through grounding, allowing the current at the emitter of the first switching transistor Q1 to flow through the sixth resistor R6 and be led to the ground terminal, providing a basis for current acquisition. Furthermore, the seventh resistor R7 is connected in parallel with the sixth resistor R6 to the first switching transistor Q1. Between the emitter of the first switching transistor Q1 and the ground terminal / first operational amplifier U1, according to Ohm's law, the current flowing through the emitter of the first switching transistor Q1 will be simultaneously shunt to the sixth resistor R6 and the seventh resistor R7. The current flowing through the seventh resistor R7 will form a voltage signal proportional to the current amplitude (voltage = current × resistance) across its terminals, thus linearly converting the "current signal" into a "voltage signal" that the first operational amplifier U1 can recognize and process. Furthermore, the seventh resistor R7 transmits the converted voltage signal to the inverting input terminal of the first operational amplifier U1 through a direct electrical connection. This voltage signal is the core feedback signal of the current negative feedback loop, which, together with the brightness feedback signal transmitted by the second operational amplifier circuit, participates in the difference comparison calculation of the first operational amplifier U1.

[0068] The sixth resistor R6 is mainly used to build a stable current acquisition circuit. By grounding, it provides a discharge path for the current of the emitter of the first switching transistor Q1, avoiding the current from being floating and thus unable to be acquired. At the same time, its fixed resistance value can limit the maximum amplitude of the circuit current, preventing damage to the sampling circuit or the first switching transistor Q1 due to overcurrent. The seventh resistor R7 is mainly used to achieve accurate signal conversion and feedback. Its resistance accuracy directly determines the accuracy of current-to-voltage conversion. Its small temperature drift ensures that the conversion coefficient remains stable when the ambient temperature changes, so that the feedback voltage signal can truly reflect the actual operating current change of the light-emitting element D1.

[0069] In this embodiment, the non-inverting input of the first operational amplifier U1 receives a reference potential signal, and the inverting input receives a voltage feedback signal transmitted by the seventh resistor R7. The first operational amplifier U1 compares the two signals in real time. When the amplitude of the voltage feedback signal is lower than the amplitude of the reference potential signal (corresponding to a smaller current and lower brightness in the light-emitting element D1), the first operational amplifier U1 increases the output voltage signal, thereby increasing the base current of the first switching transistor Q1 and deepening its conduction, thus increasing the current flowing through the light-emitting element D1. When the amplitude of the voltage feedback signal is higher than the amplitude of the reference potential signal (corresponding to a larger current and higher brightness in the light-emitting element D1), the first operational amplifier U1 decreases the output voltage signal, thereby weakening the conduction of the first switching transistor Q1 and decreasing the current flowing through the light-emitting element D1. When the amplitudes of the two signals are the same, the first operational amplifier U1 maintains a stable output, achieving closed-loop stable current control.

[0070] The photosensitive circuit includes a photodiode D2; The positive terminal of the photodiode D2 is connected to the non-inverting input terminal of the second operational amplifier U2, and the negative terminal of the photodiode D2 is connected to the output terminal of the first operational amplifier U1.

[0071] In this embodiment, the photosensitive circuit includes a photodiode D2. The photodiode D2 can be an N-type silicon-based photodiode D2, which is suitable for the DC low-voltage power supply environment of this circuit. It has the characteristics of fast response speed, high linearity of photo-to-electric conversion, and small dark current. Its core function is to convert the physical brightness signal of the light-emitting element D1 into a weak electrical signal. It only has photoelectric detection function in the reverse bias state. Its selection needs to match the emission wavelength of the light-emitting element D1 (such as visible light LEDs are adapted to visible light band photodiodes D2) to ensure detection sensitivity.

[0072] The positive terminal of the photodiode D2 is directly electrically connected to the non-inverting input of the second operational amplifier U2, without any intermediate relay components or transmission parts. This ensures that the weak electrical signal after photo-to-electric conversion can be transmitted to the second operational amplifier U2 without attenuation or interference. Furthermore, the high input impedance of the non-inverting input of the second operational amplifier U2 will not affect the signal of the photodiode D2, ensuring signal authenticity. The negative terminal of the photodiode D2 is also directly electrically connected to the output of the first operational amplifier U1, again without any intermediate relay components. This connection method provides a reverse bias electric field for the photodiode D2, which is crucial for its photoelectric detection function.

[0073] In this embodiment, the output terminal of the first operational amplifier U1 is the high-potential terminal (output driving voltage signal) in the circuit, and the non-inverting input terminal of the second operational amplifier U2 is indirectly grounded through subsequent circuits (becoming a low-potential terminal). The photodiode D2 is connected with its negative terminal at a high potential and its positive terminal at a low potential, so that its internal PN junction forms a stable reverse bias electric field, which meets the working conditions for photoelectric detection (it can only conduct electricity when forward biased, and has no photoelectric detection function). The photodiode D2 is fixed on one side of the light-emitting element D1, with the detection terminal facing the light-emitting surface of the light-emitting element D1, to capture the actual light emission brightness of the light-emitting element D1 in real time. When light shines on the PN junction of the photodiode D2, it will excite the generation of a photoelectric sensor. Photogenerated electron-hole pairs, under the influence of a reverse bias electric field, cause these charge carriers to move directionally, forming a weak photocurrent proportional to the brightness (the higher the brightness, the larger the photocurrent; the lower the brightness, the smaller the photocurrent), achieving a linear conversion from "brightness physical signal to electrical signal". The photocurrent flows into the negative terminal of the photodiode D2 and out the positive terminal, passing through the non-inverting input terminal of the second operational amplifier U2. Due to the high input impedance of the second operational amplifier U2, this current will form a weak voltage signal at its input terminal (proportional to the amplitude of the photocurrent). This voltage signal is the original detection signal of the brightness negative feedback loop, providing the basis for the subsequent signal amplification of the second operational amplifier U2.

[0074] In this embodiment, the negative terminal of photodiode D2 is directly connected to the output terminal of the first operational amplifier U1, making its detection circuit linked with the driving circuit of the light-emitting element D1. Only when the first operational amplifier U1 outputs a driving signal and the light-emitting element D1 emits light will photodiode D2 be reverse-biased and generate photocurrent. If only ambient light is present (no driving signal), photodiode D2 has no reverse bias electric field and generates almost no photocurrent, effectively filtering out ambient light interference and ensuring that the detected light-emitting element D1's actual operating brightness is the actual brightness. The positive terminal of photodiode D2 is directly connected to the non-inverting input terminal of the second operational amplifier U2. The photocurrent does not need to pass through other intermediate components and directly enters the signal input terminal of the second operational amplifier U2, avoiding signal attenuation or noise interference during transmission and ensuring the purity of the original detection signal. The stability of the reverse bias electric field ensures a good linear relationship between the photocurrent generated by photodiode D2 and the brightness of the light-emitting element D1. The converted electrical signal accurately reflects brightness changes, providing precise raw data for subsequent amplification and feedback adjustment.

[0075] Furthermore, after the photodiode D2 converts the brightness of the light-emitting element D1 into a weak voltage signal, it transmits it to the non-inverting input of the second operational amplifier U2. The second operational amplifier U2 linearly amplifies the weak signal and outputs the corresponding brightness feedback electrical signal, which is then transmitted to the inverting input of the first operational amplifier U1. The first operational amplifier U1 performs a difference comparison operation on the brightness feedback signal, the reference potential signal at the non-inverting input, and the current feedback signal from the sampling circuit, and dynamically adjusts the voltage signal output to the base of the first switching transistor Q1, thereby changing the operating current of the light-emitting element D1 and achieving closed-loop precise adjustment of the brightness.

[0076] The photosensitive circuit also includes a fifth resistor R5; One end of the fifth resistor R5 is connected to the positive terminal of the photodiode D2, and the other end of the fifth resistor R5 is connected to the ground terminal.

[0077] In this embodiment, the photosensitive circuit includes a photodiode D2 and a fifth resistor R5. The fifth resistor R5 can be a metal film fixed resistor adapted to DC low-voltage circuits, which has the characteristics of high resistance accuracy, small temperature drift, and strong anti-interference. Its resistance value is precisely selected according to the rated operating current of the photodiode D2 and the input impedance of the second operational amplifier U2. It is a passive component and does not require an additional power supply. Its core function is to stabilize the weak electrical signal output by the photodiode D2, limit the loop current, provide a stable potential reference, and avoid signal noise or overcurrent damage to the components.

[0078] One end of the fifth resistor R5 is directly electrically connected to the positive terminal of the photodiode D2. This connection point is also directly connected to the non-inverting input terminal of the second operational amplifier U2. There are no intermediate relay components or transmission parts, which ensures the directness of signal transmission and avoids signal attenuation. The other end of the fifth resistor R5 is directly electrically connected to the ground terminal, forming a complete signal stabilization and current discharge circuit. There are no additional relay components, which ensures the stability of the potential reference.

[0079] In this embodiment, the photocurrent generated by photodiode D2 under reverse bias is extremely weak and easily affected by circuit noise and environmental electromagnetic interference. The fifth resistor R5 forms a stable potential reference point through grounding, which can effectively filter high-frequency noise and interference signals in the signal, making the electrical signal output by photodiode D2 purer and smoother, avoiding noise causing the second operational amplifier U2 to amplify incorrectly or distort the signal, and ensuring the accuracy of brightness detection. The fifth resistor R5 is connected in series between the positive terminal of photodiode D2 and the ground terminal. According to Ohm's law, it can limit the maximum current flowing through photodiode D2 (including instantaneous forward current, dark current, etc.), avoiding the influence of power supply. Abnormal conditions such as source voltage fluctuations and transient electromagnetic shocks can cause excessive current to flow through the photodiode D2, resulting in PN junction breakdown or performance degradation, thus extending the component's lifespan. The fifth resistor R5 provides a fixed low potential reference (close to 0V) to the positive terminal of the photodiode D2 through grounding, forming a stable reverse bias electric field with the negative terminal of the photodiode D2 (connected to the high potential of the output terminal of the first operational amplifier U1). The strength of this electric field is not affected by signal fluctuations in other parts of the circuit, ensuring that the photo-to-electric conversion of the photodiode D2 always maintains a good linear relationship, making the correspondence between the photogenerated current and the brightness of the light-emitting element D1 more accurate, and improving the precision of feedback regulation.

[0080] Specifically, photodiode D2 is fixed on one side of light-emitting element D1. Under the action of a reverse bias electric field, it detects the actual brightness of light-emitting element D1 in real time and converts the physical brightness signal into a weak photocurrent. This photocurrent flows in from the negative terminal of photodiode D2 and out from the positive terminal. When it flows through the connection point of the fifth resistor R5 and the non-inverting input terminal of the second operational amplifier U2, the fifth resistor R5 stabilizes the potential at this point by grounding, filters noise and limits the current amplitude, so that the converted weak voltage signal remains stable. The stabilized voltage signal is directly transmitted to the non-inverting input terminal of the second operational amplifier U2. After being linearly amplified by the second operational amplifier U2, it is transmitted as a brightness feedback signal to the inverting input terminal of the first operational amplifier U1. Together with the current feedback signal of the sampling circuit, it participates in the difference comparison calculation to realize the closed-loop precise adjustment of the brightness of light-emitting element D1.

[0081] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0082] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A dual-loop negative feedback regulation circuit, comprising a power supply and a light-emitting element, characterized in that, It also includes a first operational amplifier circuit, a second operational amplifier circuit, a sampling circuit, and a photosensitive circuit; One end of the light-emitting element is connected to the power supply, and the other end of the light-emitting element is connected to the output terminal of the first operational amplifier circuit and the input terminal of the photosensitive circuit, respectively. The photosensitive circuit is located on one side of the light-emitting element. The input terminal of the sampling circuit is connected to the control terminal of the first operational amplifier circuit, and the output terminal of the sampling circuit is connected to the input terminal of the first operational amplifier circuit. The output terminal of the photosensitive circuit is connected to the input terminal of the second operational amplifier circuit, and the output terminal of the second operational amplifier circuit is connected to the input terminal of the first operational amplifier circuit.

2. The dual-loop negative feedback regulation circuit according to claim 1, characterized in that, The first operational amplifier circuit includes a first operational amplifier and a first switching transistor; The inverting input terminal of the first operational amplifier is connected to the output terminal of the sampling circuit and the output terminal of the second operational amplifier circuit; The output terminal of the first operational amplifier is connected to the base of the first switching transistor, the collector of the first switching transistor is connected to the light-emitting element, and the emitter of the first switching transistor is connected to the input terminal of the sampling circuit. The non-inverting input of the first operational amplifier is used to receive a reference potential signal.

3. The dual-loop negative feedback regulation circuit according to claim 2, characterized in that, It also includes a potentiometer for providing a reference potential signal; One end of the potentiometer is connected to the power supply, the other end of the potentiometer is connected to the ground terminal, and the sliding terminal of the potentiometer is connected to the non-inverting input terminal of the first operational amplifier.

4. The dual-loop negative feedback regulation circuit according to claim 2, characterized in that, The first operational amplifier circuit also includes a first resistor; One end of the first resistor is connected to the output terminal of the first operational amplifier, and the other end of the first resistor is connected to the base of the first switching transistor.

5. The dual-loop negative feedback regulation circuit according to claim 2, characterized in that, The second operational amplifier circuit includes a second operational amplifier; The non-inverting input of the second operational amplifier is connected to the output of the photosensitive circuit; The output terminal of the second operational amplifier is connected to the inverting input terminal of the first operational amplifier.

6. The dual-loop negative feedback regulation circuit according to claim 5, characterized in that, The second operational amplifier circuit also includes a second resistor and a third resistor; One end of the second resistor is connected to the inverting input terminal of the second operational amplifier, and the other end of the second resistor is connected to the output terminal of the second operational amplifier; One end of the third resistor is connected to the inverting input of the second operational amplifier, and the other end of the third resistor is connected to the ground terminal.

7. The dual-loop negative feedback regulation circuit according to claim 5, characterized in that, The second operational amplifier circuit also includes a fourth resistor; One end of the fourth resistor is connected to the output terminal of the second operational amplifier, and the other end of the fourth resistor is connected to the inverting input terminal of the first operational amplifier.

8. The dual-loop negative feedback regulation circuit according to claim 2, characterized in that, The sampling circuit includes a sixth resistor and a seventh resistor; One end of the sixth resistor is connected to the emitter of the first switching transistor, and the other end of the sixth resistor is connected to the ground terminal; One end of the seventh resistor is connected to the emitter of the first switching transistor, and the other end of the seventh resistor is connected to the inverting input of the first operational amplifier.

9. A dual-loop negative feedback regulation circuit according to claim 5, characterized in that, The photosensitive circuit includes a photodiode; The positive terminal of the photodiode is connected to the non-inverting input terminal of the second operational amplifier, and the negative terminal of the photodiode is connected to the output terminal of the first operational amplifier.

10. A dual-loop negative feedback regulation circuit according to claim 9, characterized in that, The photosensitive circuit also includes a fifth resistor; One end of the fifth resistor is connected to the positive terminal of the photodiode, and the other end of the fifth resistor is connected to the ground terminal.

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