Constant power control circuit of probiotic incubator

Abstract

The invention discloses a constant power control circuit of a probiotic incubator, which belongs to the technical field of control circuits, and is characterized in that a power supply is sequentially connected in series with a heating resistor, a switching tube and a sampling resistor to form a heating loop; the heating resistor is connected with the switching tube through the first divider resistor and the second divider resistor in sequence; the normal-phase input end and the inverted-phase input end of the operational amplifier are connected in parallel to the two ends of the sampling resistor, and the output end of the operational amplifier is connected with the current input end of the MCU; the voltage input end of the MCU is connected between the first divider resistor and the second divider resistor; the output end of the MCU is connected with the switching tube; and when the MCU receives the current signal and the voltage signal, a PWM control signal is fed back through the output end of the MCU so as to adjust the duty ratio of the switching tube. By adjusting the duty ratio of the switching tube in real time, power supply voltage fluctuation and drifting of the heating resistor can be effectively coped with.

Description

Technical Field

[0001] This invention belongs to the field of control circuit technology, specifically relating to a constant power control circuit for a probiotic culture device. Background Technology

[0002] A probiotic culture device is used to control and maintain the growth conditions of probiotics, providing suitable temperature, humidity, pH, and gas environment to promote optimal probiotic cultivation. It typically includes temperature and humidity control functions to maintain the stability of the culture environment and promote the growth and reproduction of probiotics. A constant power control circuit is used to maintain a constant power output in the device, commonly found in probiotic culture devices. This ensures the stability of the power output during long-term operation, preventing overload or power fluctuations from affecting the cultivation effect. Its principle involves real-time monitoring of current and voltage and adjusting the power output in the circuit to ensure the device operates at a specific power level.

[0003] The power control circuit of a probiotic culture device is crucial. It not only ensures long-term stable operation of the equipment, preventing damage or disruption of the culture environment caused by voltage or current fluctuations, but also improves energy efficiency, extends equipment lifespan, and guarantees optimal probiotic culture results. A constant power control circuit helps maintain stable environmental parameters such as temperature and humidity, ensuring probiotics grow under optimal conditions, thus improving production efficiency and product quality.

[0004] Existing power control circuits cannot respond quickly to load changes, which can easily lead to power fluctuations and unstable equipment operation. Furthermore, probiotic culturers need to operate for extended periods, and current control circuits often ignore the resistance drift caused by heat accumulation in the load resistor, further resulting in insufficient power control accuracy. Summary of the Invention

[0005] The purpose of this invention is to provide a constant power control circuit for a probiotic culture device, which can solve the technical problem that existing power control circuits cannot respond quickly when the load changes, are prone to power fluctuations, and cause unstable operation of the device. Furthermore, probiotic culture devices need to work for a long time, and current control circuits usually ignore the resistance drift of the load resistance due to heat accumulation, which further leads to insufficient control accuracy of the working power.

[0006] To solve the above-mentioned technical problems, the present invention provides a constant power control circuit for a probiotic culture device.

[0007] First aspect This invention provides a constant power control circuit for a probiotic culture device, comprising: a power supply, a heating resistor, a switching transistor, a sampling resistor, an operational amplifier, a first voltage divider resistor, a second voltage divider resistor, and a microcontroller unit; The power supply is connected in series with the heating resistor, the switching transistor, and the sampling resistor to form a heating circuit. The heating resistor is connected to the switching transistor in sequence through a first voltage divider resistor and a second voltage divider resistor; The non-inverting and inverting inputs of the op-amp are connected in parallel across the sampling resistor. The output of the op-amp is connected to the current input of the MCU. The voltage input of the MCU is connected between the first and second voltage divider resistors. The output of the MCU is connected to the switching transistor. The current input of the MCU is used to receive the current signal, and the voltage input of the MCU is used to receive the voltage signal. When the MCU receives current and voltage signals, it feeds back PWM control signals through the MCU output terminal to adjust the duty cycle of the switching transistor.

[0008] Optionally, the positive terminal of the power supply is connected to the heating resistor, and the negative terminal of the power supply is connected to the sampling resistor.

[0009] Optionally, the switching transistor is specifically an N-channel switching transistor, with the drain of the N-channel switching transistor connected to the heating resistor, the source of the N-channel switching transistor connected to the sampling resistor, and the gate of the N-channel switching transistor connected to the MCU output terminal.

[0010] Optionally, it may also include: a gate resistor; The gate resistor is connected in series between the gate of the N-channel switch and the output terminal of the MCU; the heating resistor is connected to the gate of the N-channel switch in sequence through the first voltage divider resistor, the second voltage divider resistor and the gate resistor.

[0011] Optionally, it also includes: a gain resistor and a feedback resistor; One end of the gain resistor is connected between the switching transistor and the sampling resistor, and the other end of the gain resistor is connected to the inverting input of the operational amplifier. The two ends of the feedback resistor are connected to the inverting input terminal and the output terminal of the op-amp, respectively.

[0012] Alternatively, the operational amplifier may specifically be an OPA335.

[0013] Alternatively, the MCU may be specifically an STM32G431 microcontroller.

[0014] Optionally, the negative power supply, sampling resistor, non-inverting input terminal, and MCU are all grounded.

[0015] Optionally, the calculation process of the PWM control signal specifically includes: Obtain the target power of the probiotic culture device; Calculate the equivalent resistance and actual power of the heating resistor based on the voltage and current signals. The equivalent resistance and actual power are superimposed on the target power as compensation signals to calculate the PWM control signal.

[0016] Optionally, the calculation formula for the PWM control signal is as follows: ; ; ; ; PID ; ; in, express k The PWM control signal at any time is k Duty cycle at any time Represents the amplitude limiting function. Indicates the target power. express k Equivalent resistance at any time express k Equivalent resistance at any time express k Voltage across the heating resistor at time -1 and These represent the first voltage divider resistor and the second voltage divider resistor, respectively. and They represent k Time and k The current flowing through the heating resistor is obtained by inverse operation of the current signal at time -1. denoted by k, the power error at time k is represented by PID, which stands for PID controller.

[0017] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following: In this embodiment of the invention, an intelligent feedback adjustment mechanism effectively solves the problems caused by power supply voltage fluctuations and load resistance drift due to temperature changes. The circuit uses a microcontroller unit to collect current and voltage signals in real time, monitoring changes in the power supply and load status. The microcontroller unit adjusts the duty cycle of the switching transistor based on these signals, thereby precisely controlling the heating power and ensuring that the heating power on the load remains constant. This circuit utilizes sampling resistors and voltage divider resistors to monitor voltage and current, amplifies and processes the signals through an operational amplifier, and then controls the switching transistor through PWM regulation to dynamically respond to load changes and avoid power fluctuations. Even in environments with significant power supply or load variations, the system can still maintain stable heating power, avoiding resistance drift caused by temperature changes, thus providing a continuous and stable thermal environment to ensure the normal growth of probiotics. This improves the stability and reliability of the system, effectively preventing performance fluctuations caused by changes in the external environment during long-term operation. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the constant power control circuit of a probiotic culture device provided in an embodiment of the present invention; Figure 2 This is another schematic diagram of the constant power control circuit of a probiotic culture device provided in an embodiment of the present invention.

[0019] Attached image description: R HEATER Load resistance; R v1 First voltage divider resistor; R v2 1. Second voltage divider resistor; U1; Operational amplifier; R SENSE Sampling resistor; Q1; Switching transistor; Ground; GND.

[0020] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0022] The constant power control circuit of the probiotic culturer provided in the embodiments of the present invention will be described in detail below with reference to the accompanying drawings, through specific embodiments and application scenarios.

[0023] Example 1 Reference Figure 1 The diagram shows a schematic of the constant power control circuit of a probiotic culture device provided in an embodiment of the present invention.

[0024] Reference Figure 2 The diagram shows another structural schematic of a constant power control circuit for a probiotic culture device provided in an embodiment of the present invention.

[0025] The present invention provides a constant power control circuit for a probiotic culture device, comprising: a power supply, a heating resistor, a switching transistor, a sampling resistor, an operational amplifier, a first voltage divider resistor, a second voltage divider resistor, and a microcontroller unit.

[0026] The power supply is connected in series with the heating resistor, the switching transistor, and the sampling resistor to form a heating circuit.

[0027] The heating resistor is connected to the switching transistor in sequence through the first voltage divider resistor and the second voltage divider resistor.

[0028] The non-inverting and inverting inputs of the operational amplifier are connected in parallel across the sampling resistor. The output of the operational amplifier is connected to the current input of the MCU. The voltage input of the MCU is connected between the first and second voltage divider resistors. The output of the MCU is connected to the switching transistor. The MCU current input receives the current signal, and the MCU voltage input receives the voltage signal.

[0029] When the MCU receives current and voltage signals, it feeds back PWM control signals through the MCU output terminal to adjust the duty cycle of the switching transistor.

[0030] Specifically, in this constant power control circuit, the power supply provides the necessary electrical energy to support the operation of the entire system. The heating resistor is the load element in the circuit; it converts electrical energy into heat energy to provide the necessary temperature environment for the probiotics. The switching transistor, controlled by the microcontroller unit, regulates the current flow to control the heating degree of the heating resistor. The sampling resistor monitors the current magnitude, and the operational amplifier processes the current signal to ensure stable signal transmission to the microcontroller unit. The first and second voltage divider resistors work together to provide a voltage signal to the microcontroller unit through voltage division. The microcontroller unit analyzes the current and voltage signals to calculate the required PWM control signal to adjust the duty cycle of the switching transistor, thereby regulating the heating power.

[0031] This circuit uses an intelligent feedback mechanism to adjust the duty cycle of the switching transistor in real time, effectively addressing power supply voltage fluctuations and heating resistor drift. When the power supply voltage or heating resistor fluctuates due to temperature changes, the microcontroller dynamically adjusts the duty cycle of the switching transistor based on sampled current and voltage information, thereby locking in a constant power to the heating resistor. This feedback adjustment mechanism ensures that the entire system maintains stable heating power, avoiding the impact of power fluctuations on the probiotic culture environment. Because it can compensate for changes caused by voltage variations and load drift, the circuit exhibits strong stability and reliability, continuously providing constant operating power during long-term operation.

[0032] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following: In this embodiment of the invention, the circuit acquires current and voltage signals in real time through a microcontroller unit to monitor changes in the power supply and load status. The microcontroller unit adjusts the duty cycle of the switching transistor based on these signals, thereby precisely controlling the heating power and ensuring that the heating power on the load remains constant. This circuit utilizes sampling resistors and voltage divider resistors to monitor voltage and current, amplifies and processes the signals through an operational amplifier, and then controls the switching transistor via PWM regulation to dynamically respond to load changes and avoid power fluctuations. Even in environments with significant power supply or load variations, the system can still maintain stable heating power, avoiding resistance drift caused by temperature changes, thus providing a continuous and stable thermal environment to ensure the normal growth of probiotics. This improves the stability and reliability of the system, effectively preventing performance fluctuations caused by changes in the external environment during long-term operation.

[0033] In one possible implementation, the positive terminal of the power supply is connected to the heating resistor, and the negative terminal of the power supply is connected to the sampling resistor.

[0034] Understandably, the positive terminal of the power supply directly provides current to the heating resistor, ensuring that the heating resistor can convert electrical energy into heat energy, thereby generating the required temperature. The negative terminal of the power supply is connected to a sampling resistor, which is used to monitor the current magnitude in the circuit, helping the system acquire current signals in real time. The current signal acquired through the sampling resistor is fed back to the microcontroller unit, which adjusts the switching transistors in the circuit based on these signals to maintain a constant power output from the heating resistor.

[0035] In one possible implementation, the switching transistor is specifically an N-channel switching transistor, with its drain connected to a heating resistor, its source connected to a sampling resistor, and its gate connected to the MCU output.

[0036] It should be noted that, based on the characteristic that an N-channel MOSFET conducts when its gate voltage is higher than the source threshold, the MCU adjusts the gate voltage via a PWM signal to control the MOSFET's on / off state—forming a heating circuit when on and interrupting current when off. By changing the PWM duty cycle (on-time ratio), the average current and power of the heating circuit can be adjusted, thereby offsetting the effects of power supply voltage fluctuations or heating resistor drift and achieving constant power control. This connection method satisfies the current path requirements of the heating circuit and utilizes the advantages of N-channel MOSFET voltage drive and fast switching speed, adapting to the real-time requirements of constant power regulation.

[0037] In one possible implementation, a gate resistor is also included.

[0038] The gate resistor is connected in series between the gate of the N-channel switch and the output terminal of the MCU. The heating resistor is connected to the gate of the N-channel switch in sequence through the first voltage divider resistor, the second voltage divider resistor, and the gate resistor.

[0039] It should be noted that the gate resistor is connected in series between the MCU output and the gate of the N-channel MOSFET. Its function is to limit the gate charging and discharging current (because there is input capacitance between the gate and source of the N-channel MOSFET, a large instantaneous current will be generated when the PWM signal switches), preventing damage to the MCU output pin or the MOSFET gate. At the same time, it can buffer the edges of the PWM signal, reduce voltage spikes generated by parasitic inductance (such as wiring inductance) during switching, avoid gate overvoltage breakdown, and improve circuit stability.

[0040] The design, where the heating resistor is connected to the gate sequentially via a first voltage divider resistor, a second voltage divider resistor, and a gate resistor, transmits the voltage signal from the heating resistor (after being stepped down by the voltage divider resistors) to the gate circuit. This assists the MCU in combining the PWM control signal with the real-time voltage state of the heating resistor, enabling more precise adjustment of the gate voltage. This ensures that the duty cycle of the switching transistor matches the constant power control requirements (e.g., when voltage fluctuates, the gate drive is corrected through the voltage divider signal to maintain stable heating power). This design achieves both MOSFET drive protection and, in conjunction with the voltage divider resistors, enhances the accuracy of constant power control.

[0041] In one possible implementation, it also includes a gain resistor and a feedback resistor.

[0042] One end of the gain resistor is connected between the switching transistor and the sampling resistor, and the other end of the gain resistor is connected to the inverting input of the op-amp.

[0043] The two ends of the feedback resistor are connected to the inverting input terminal and the output terminal of the op-amp, respectively.

[0044] It should be noted that the gain resistor and feedback resistor work together to configure the operational amplifier as a proportional amplifier, amplifying the small voltage signal across the sampling resistor (because the sampling resistor has a small resistance, the voltage generated when current flows is weak), improving the sensitivity of current detection, and enabling the MCU to more accurately obtain real-time current information of the heating circuit. Simultaneously, the feedback resistor forms a negative feedback loop, stabilizing the operational amplifier's amplification factor and preventing temperature changes or power supply fluctuations from affecting detection accuracy, thus ensuring the accuracy of constant power control. This solves the problem of weak voltage signal due to the small resistance of the sampling resistor, making it easier for the MCU's ADC (analog-to-digital converter) to recognize the signal through amplification, while the negative feedback ensures the stability of the amplification factor, providing a reliable current signal basis for subsequent power calculation and duty cycle adjustment.

[0045] In one possible implementation, the operational amplifier is specifically an OPA335.

[0046] Among them, the OPA335 is a high-precision operational amplifier. Its low offset voltage, low temperature drift and high common-mode rejection ratio can accurately amplify the small current signal across the sampling resistor and maintain detection stability when the temperature changes or power supply fluctuates. It provides a reliable current detection basis for constant power control and ensures the temperature stability of the probiotic culture environment.

[0047] In one possible implementation, the MCU is specifically an STM32G431 microcontroller.

[0048] The STM32G431 microcontroller features a high-precision ADC module and PWM output, enabling real-time and accurate acquisition of current and voltage signals and rapid adjustment of the MOSFET duty cycle to ensure stable heating power. Its powerful computing capabilities support complex control algorithms (such as PID regulation), while its rich interface resources facilitate system expansion and parameter monitoring, providing a reliable hardware foundation for constant temperature control.

[0049] In one possible implementation, the negative power supply, the sampling resistor, the non-inverting input, and the MCU are all grounded.

[0050] Understandably, the negative power supply, sampling resistor, operational amplifier non-inverting input, and MCU are connected to a common ground to form a unified reference potential. This ensures that the current detection signal and voltage divider signal are referenced to the same ground potential, avoiding measurement errors caused by inconsistent reference points. It also simplifies the circuit layout and improves anti-interference capabilities.

[0051] In one possible implementation, the calculation process of the PWM control signal specifically includes: Obtain the target power of the probiotic culture device.

[0052] Calculate the equivalent resistance and actual power of the heating resistor based on the voltage and current signals.

[0053] The equivalent resistance and actual power are superimposed on the target power as compensation signals to calculate the PWM control signal.

[0054] Specifically, this control process employs a closed-loop regulation strategy. First, a target power is set as a reference value. Then, by real-time monitoring of the voltage and current signals of the heating resistor, its equivalent impedance and instantaneous power are dynamically calculated, and these two parameters are introduced into the control system as feedback quantities. By compensating for impedance changes and power deviations to the target value, an optimized PWM duty cycle signal is generated, thereby achieving precise control of the switching transistor. This compensation mechanism effectively counteracts the effects of power supply fluctuations and resistor temperature drift, ensuring that the heating power remains strictly stable at the set value.

[0055] In one possible implementation, the formula for calculating the PWM control signal is as follows: ; ; ; ; PID ; ; in, express k The PWM control signal at any time is k Duty cycle at any time Represents the amplitude limiting function. Indicates the target power. express k Equivalent resistance at any time express k Voltage across the heating resistor at time -1 and These represent the first voltage divider resistor and the second voltage divider resistor, respectively. and They represent k Time and k The current flowing through the heating resistor is obtained by inverse operation of the current signal at time -1. denoted by k, the power error at time k is represented by PID, which stands for PID controller.

[0056] The current flowing through the heating resistor, obtained through inverse operation of the current signal, refers to the real-time loop current value calculated using Ohm's law by combining the voltage signal across the sampling resistor (amplified by an operational amplifier and input to the MCU) with the known resistance value of the sampling resistor. Since this current is the same as the current in the heating resistor (equal currents in a series loop), it accurately reflects the operating state of the heating resistor. The control algorithm achieves dynamic compensation through PID regulation: first, it detects the real-time voltage of the heating resistor based on a voltage divider resistor network, and calculates the equivalent resistance and actual power based on the sampled current. Then, it inputs the power error into the PID controller to generate a compensation value, and finally calculates the optimal duty cycle based on the target power and equivalent resistance. This design automatically adapts to power supply voltage fluctuations and resistor temperature drift, locking the target power by adjusting the PWM duty cycle in real time to ensure heating stability. Its core lies in using iterative estimation of the equivalent resistance and PID compensation to form a closed-loop control with anti-interference capabilities.

[0057] In practical applications, each component of this constant power control circuit can be adaptively adjusted according to the target power. A voltage divider resistor network is used to monitor the voltage across the heating resistor in real time. Simultaneously, a high-precision operational amplifier amplifies the current signal from the sampled resistor. The MCU integrates these two feedback signals to calculate the actual power and compares it with the target value. A PID algorithm dynamically adjusts the PWM duty cycle to control the MOSFET's on / off state, thus forming a closed-loop system of detection-calculation-adjustment. This circuit ensures comprehensive parameter acquisition through dual voltage and current detection, enhances micro-signal processing capabilities with a high-precision operational amplifier, and achieves rapid dynamic compensation with PID control, enabling the system to automatically offset the effects of power fluctuations and resistor temperature drift. Its unique linkage design between the voltage divider resistor and the gate resistor protects the switching transistor and enhances control accuracy, while the common ground connection eliminates errors caused by reference potential differences. Through intelligent real-time adjustment, the entire system maintains constant heating power even under complex operating conditions, providing a highly stable thermal environment for probiotic cultivation and significantly improving the equipment's reliability and environmental adaptability. This control strategy, integrating precise detection, rapid response, and intelligent compensation, gives the circuit outstanding advantages in anti-interference, control accuracy, and long-term stability.

[0058] The above are merely embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A constant power control circuit for a probiotic culture device, characterized in that, include: Power supply, heating resistor, switching transistor, sampling resistor, operational amplifier, first voltage divider resistor, second voltage divider resistor, and microcontroller unit; The power supply is connected in series with the heating resistor, the switching transistor, and the sampling resistor to form a heating circuit; The heating resistor is connected to the switching transistor in sequence through the first voltage divider resistor and the second voltage divider resistor; The non-inverting and inverting input terminals of the operational amplifier are connected in parallel across the sampling resistor. The output terminal of the operational amplifier is connected to the current input terminal of the MCU. The voltage input terminal of the MCU is connected between the first voltage divider resistor and the second voltage divider resistor. The output terminal of the MCU is connected to the switching transistor. The current input terminal of the MCU is used to receive current signals, and the voltage input terminal of the MCU is used to receive voltage signals. Upon receiving the current signal and the voltage signal, the MCU feeds back a PWM control signal through its output terminal to adjust the duty cycle of the switching transistor.

2. The constant power control circuit for the probiotic culture device according to claim 1, characterized in that, The positive terminal of the power supply is connected to the heating resistor, and the negative terminal of the power supply is connected to the sampling resistor.

3. The constant power control circuit for the probiotic culture device according to claim 1, characterized in that, The switching transistor is specifically an N-channel switching transistor. The drain of the N-channel switching transistor is connected to the heating resistor, the source of the N-channel switching transistor is connected to the sampling resistor, and the gate of the N-channel switching transistor is connected to the output terminal of the MCU.

4. The constant power control circuit for the probiotic culture device according to claim 3, characterized in that, It also includes: gate resistor; The gate resistor is connected in series between the gate of the N-channel switch and the output terminal of the MCU; the heating resistor is connected to the gate of the N-channel switch in sequence through the first voltage divider resistor, the second voltage divider resistor and the gate resistor.

5. The constant power control circuit for the probiotic culture device according to claim 1, characterized in that, Also includes: Gain resistor and feedback resistor; One end of the gain resistor is connected between the switching transistor and the sampling resistor, and the other end of the gain resistor is connected to the inverting input terminal of the operational amplifier. The two ends of the feedback resistor are respectively connected to the inverting input terminal and the output terminal of the operational amplifier.

6. The constant power control circuit for the probiotic culture device according to claim 1, characterized in that, The operational amplifier is specifically an OPA335.

7. The constant power control circuit for the probiotic culture device according to claim 1, characterized in that, The MCU is specifically an STM32G431 microcontroller.

8. The constant power control circuit for the probiotic culture device according to claim 1, characterized in that, The negative power supply, the sampling resistor, the positive input terminal, and the MCU are all grounded.

9. The constant power control circuit for the probiotic culture device according to claim 1, characterized in that, The calculation process of the PWM control signal specifically includes: Obtain the target power of the probiotic culture device; Calculate the equivalent resistance and actual power of the heating resistor based on the voltage signal and the current signal; The equivalent resistance and the actual power are superimposed on the target power as compensation signals to calculate the PWM control signal.

10. The constant power control circuit for the probiotic culture device according to claim 9, characterized in that, The specific formula for calculating the PWM control signal is as follows: ； ； ； ； PID ; ； in, express k The PWM control signal at any time is k Duty cycle at any time Represents the amplitude limiting function. Indicates the target power. express k Equivalent resistance at any moment express k Voltage across the heating resistor at time -1 and These represent the first voltage divider resistor and the second voltage divider resistor, respectively. and They represent k Time and k The current flowing through the heating resistor is obtained by inverse operation of the current signal at time -1. denoted by k, the power error at time k is represented by PID, which stands for PID controller.

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