PWM (Pulse Width Modulation) adaptive control type heating circuit, device and method based on differential guidance

Abstract

The invention discloses a PWM adaptive control type heating circuit, device and method based on differential guidance, and relates to the technical field of heating devices. The heating circuit comprises a differential bridge, a Darlington tube switch, a voltage follower circuit, an instrument amplifier, a differential circuit and a comparison output circuit. According to the invention, the method is different from the conventional method for detecting the temperature value of the heating sheet by using an upper computer or a temperature sensor so as to carry out feedback control; the control of the heating rate and the constant temperature keeping is realized by simply setting the resistance value and limiting the target temperature value and adjusting the duty ratio of the PWM through the circuit so as to further adjust the turn-on time of the power supply, and the long-standing technical contradiction among rapid heating, high-precision constant temperature and ultra-low power consumption self-sustaining is innovatively and skillfully solved.

Description

Technical Field

[0001] This invention relates to the field of heating device technology, and more specifically, to: 1. a heating circuit based on differential guidance PWM adaptive control; 2. a heating device based on differential guidance PWM adaptive control; 3. a heating method based on differential guidance PWM adaptive control. Background Technology

[0002] Heating elements play an important role in daily life and scientific research. For example, the core component of everyday heating appliances such as hair dryers, clothes dryers, heaters, and electric heating pads is the heating element. Common types include silicone heating elements, polyimide heating elements, mica heating elements, PET heating elements, and ceramic heating elements.

[0003] Currently, most heating devices based on heating elements focus on structural improvements of the heating device itself, but lack research on heating drive circuits. These circuits mostly rely on digital processing units and cannot achieve truly low static power consumption. Although a few use pure analog schemes, they mainly use comparators or operational amplifiers to build simple switching controllers or linear controllers. The control strategies are singular, lacking adaptive capabilities, and cannot automatically adjust the control strength according to the error magnitude. They also have poor anti-interference capabilities and are easily affected by power fluctuations.

[0004] Furthermore, current requirements for heating devices include "rapid start-up," "high-precision temperature control," and "low self-sustaining power consumption"—that is, providing maximum power under large temperature differences, fine-tuning to achieve precise temperature control when approaching the target temperature, and maintaining low static power consumption during energy self-sustaining. Traditional high-precision control requires high-frequency sampling and adjustment, often employing multiple sensors, complex feedback circuits or external controllers, and complex control algorithms. This results in a large number of components, complex wiring, and a significant increase in overall cost, making it difficult to achieve miniaturization, integration, and industrial applicability of the overall structure. Moreover, the resulting circuit power consumption reduces system energy efficiency, violating the basic requirement of self-sustaining operation.

[0005] Therefore, a key challenge is how to simplify the circuit, use general-purpose components, and optimize the circuit structure to reduce manufacturing costs while ensuring that the requirements of "fast start-up", "high-precision constant temperature" and "low self-sustaining power consumption" are met. Summary of the Invention

[0006] Therefore, it is necessary to provide a heating circuit and device based on differential guidance PWM adaptive control to address the issue of how to simplify the circuit, use general-purpose components, and optimize the circuit structure to reduce manufacturing costs while ensuring "fast start-up", "high-precision constant temperature" and "low self-sustaining power consumption".

[0007] This invention is achieved using the following technical solution: In a first aspect, the present invention provides a PWM adaptive control heating circuit based on differential guidance for temperature control of a heating element R2 whose resistance is positively correlated with temperature.

[0008] The differential-guided PWM adaptive control heating circuit includes: a differential bridge, a control switch, and a PWM drive circuit.

[0009] The differential bridge includes: fixed resistors R3~R4 and a variable resistor R1. R1 is used to form the first circuit in series with R2, and is adjusted according to the target temperature T of R2. set Adjust its resistance value to T set / M; R3 and R4 are connected in series to form the second path; the first path and the second path are connected in parallel. The resistance ratio of R3 to R4 is 1:M; M>0; the bridge balance point provided by the differential bridge corresponds to the resistance ratio of R1 to R2 being 1:M.

[0010] The control switch is used to: connect the differential bridge to power supply VCC2, and according to the PWM signal V PWM Control whether the differential bridge is connected to VCC2.

[0011] The PWM drive circuit operates under the power supply VCC1 and includes: a voltage follower circuit, an instrumentation amplifier, a differential circuit, and a comparator output circuit.

[0012] The voltage follower circuit includes voltage followers U1 and U2. U1 is used to output the voltage V1 between R1 and R2; U2 is used to output the voltage V2 between R3 and R4.

[0013] The instrumentation amplifier is used to: provide an adjustable differential gain and differentially amplify V1 and V2 to obtain the amplified signal V. big .

[0014] The differential circuit is used to: separate the sawtooth wave signal ST from V big Perform differential processing to obtain the differential output V st .

[0015] The comparator output circuit is used to: convert V st Compare with zero potential to obtain V PWM .

[0016] This implementation of a differential-guided PWM adaptive control heating circuit is based on the method or process of an embodiment of this disclosure.

[0017] Secondly, the present invention discloses a PWM adaptive control heating device based on differential guidance, which includes: heating element R2, power supply VCC1~VCC2, and heating control module.

[0018] The heating control module adopts the layout of the differential-guided PWM adaptive control heating circuit disclosed in the first aspect and is connected to R2, VCC1, and VCC2.

[0019] The implementation of this differential-guided PWM adaptive control heating device is based on the method or process of an embodiment of this disclosure.

[0020] Thirdly, the present invention discloses a PWM adaptive control heating method based on differential guidance, which is applied to the PWM adaptive control heating circuit based on differential guidance disclosed in the first aspect, or to the PWM adaptive control heating device based on differential guidance disclosed in the second aspect.

[0021] Differential-guided PWM adaptive control heating methods include: According to T set Adjust the resistance of R1 to T. set / M.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention provides a PWM adaptive control heating circuit based on differential guidance. Unlike existing systems that use a host computer or temperature sensor to detect the temperature value of the heating element for feedback control, this invention uses a pure analog hardware circuit. It achieves control over the heating rate and constant temperature by simply setting the resistance value and limiting the target temperature value, and by adjusting the duty cycle of the PWM through the circuit itself to adjust the power supply on-time. This innovatively and ingeniously solves the long-standing technical contradiction between rapid heating, high-precision constant temperature, and ultra-low power consumption.

[0023] 2. This invention can provide millisecond-level fast dynamic response and high-precision steady-state control. By utilizing the instantaneous response characteristics of pure analog hardware circuits to signal changes, it eliminates the inherent sampling and control delays of digital systems and achieves millisecond-level fast temperature tracking. At the same time, this invention can provide extremely high gain suppression and fine stepless power fine-tuning near the target temperature point, achieving temperature stability with a precision of ±1℃ or even higher, without continuous oscillation.

[0024] 3. This invention facilitates integrated design and can achieve satisfactory constant temperature heating effect with a simple structure and low manufacturing cost, making it particularly suitable for applications with strict space and cost constraints. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a structural diagram of the PWM adaptive control heating device based on differential guidance provided in Embodiment 1 of the present invention; Figure 2 This is a structural diagram of a PWM adaptive control heating circuit based on differential guidance provided in Embodiment 1 of the present invention; Figure 3 The ST waveform diagram provided in Embodiment 1 of the present invention; Figure 4 V provided in Embodiment 1 of the present invention st Waveform diagram; Figure 5 This is a structural diagram of the experimental apparatus provided in Embodiment 2 of the present invention; Figure 6 Experimental results provided for Embodiment 2 of the present invention Figure 1 ; Figure 7 Experimental results provided for Embodiment 2 of the present invention Figure 2 ; Figure 8 Experimental results provided for Embodiment 2 of the present invention Figure 3 ; Figure 9 Experimental results provided for Embodiment 2 of the present invention Figure 4 ; Figure 10 Experimental results provided for Embodiment 2 of the present invention Figure 5 . Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] It should be noted that when a component is said to be "installed on" another component, it can be directly on the other component or it may be in a component that is centered on it. When a component is said to be "set on" another component, it can be directly set on the other component or it may also be in a component that is centered on it. When a component is said to be "fixed to" another component, it can be directly fixed to the other component or it may also be in a component that is centered on it.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0030] First of all, it should be noted that the present invention is designed for heating control of heating elements—suppressing overshoot during the heating process of heating elements to the target temperature.

[0031] As mentioned in the background section, heating elements (including silicone heating elements, polyimide heating elements, mica heating elements, PET heating elements, ceramic heating elements, etc.) have similar resistance-temperature characteristics: resistance is positively correlated with temperature, meaning resistance increases with increasing temperature. This is because their internal heating elements follow the common physical law of a "positive temperature coefficient of resistance": increased temperature leads to increased lattice thermal vibration, thereby enhancing the scattering of free electrons, macroscopically manifested as increased resistance. This characteristic provides a natural negative feedback mechanism, preventing unlimited power, helping to avoid extreme overheating due to dry burning, improving safety to a certain extent, and ultimately stabilizing the heating element at an equilibrium temperature—when the heating rate is equal to the heat dissipation rate, the surface of the heating element will be in a dynamic equilibrium state.

[0032] Unlike existing heating controls that require temperature sensors (such as PT100 or thermocouples) to measure the temperature of the heating element, along with a suitable MCU controller and PID control programs to modulate the PWM, this invention breaks the traditional paradigm that "complex control must rely on digital processors." It innovatively designs a pure analog hardware circuit that controls the heating rate and maintains a constant temperature by simply setting the resistance value and limiting the target temperature value, and by adjusting the PWM duty cycle and power supply on-time through the circuit itself.

[0033] Example 1 See Figure 1 The invention demonstrates a PWM adaptive control heating device based on differential guidance provided in Embodiment 1 of the present invention, which includes: a heating element R2, power supplies VCC1~VCC2, and a heating control module.

[0034] It should be noted that R2 meets the characteristics mentioned above—its resistance is positively correlated with temperature. A ceramic heating element is recommended for R2.

[0035] VCC1 serves as the power supply for heating R2 and can be of various specifications such as 5V, 9V, 12V, 18V, and 24V. However, considering the modular power supply design, 5V is recommended. VCC2 serves as the power supply for the heating control module and is generally set to 15V.

[0036] The heating control module, the core design of this invention, employs a circuit layout based on differential guidance and PWM adaptive control for the heating circuit, used to control the temperature of R2. The heating control module can be fabricated on a PCB board using existing common processing techniques, resulting in high integration and low manufacturing cost.

[0037] See Figure 2 This diagram illustrates the structure of a PWM adaptive control heating circuit based on differential guidance. As described above, this heating circuit is used for temperature control of R2.

[0038] The heating circuit can be divided into the following functional areas: differential bridge, control switch, voltage follower circuit, instrumentation amplifier, differential circuit, and comparison output circuit.

[0039] The voltage follower circuit, instrumentation amplifier, differential circuit, and comparator output circuit all operate under the power supply VCC1, so these parts can be combined into a PWM drive circuit.

[0040] The following is an explanation of each part: ① A differential bridge can be designed to include: fixed resistors R3~R4 and variable resistor R1.

[0041] R1 is used for: connecting in series with R2 to form the first path; connecting R3 and R4 in series to form the second path; connecting the first path and the second path in parallel.

[0042] like Figure 2 As shown, the first end of R1 is connected to the first end of R3 and connected to VCC2 via a control switch; the second end of R1 is connected to the first end of R2; the second end of R2 is grounded to GND; the second end of R3 is connected to the first end of R4, and the second end of R4 is grounded to GND. However, in actual use, the second end of R1 is connected to the first end of R2, and the second end of R2 is grounded to GND.

[0043] The resistance ratio of R3 to R4 is 1:M; M > 0. Theoretically, the larger the value of M, the better. Since R3 to R4 are fixed resistors, once the resistance values ​​of R3 and R4 are fixed, the value of M will also be fixed. In this embodiment 1, M = 10.

[0044] The resistance value of R1 is adjustable—it is used to determine the target temperature T of R2. set Adjust its resistance value to T set The resistance of R1 is 1:M, while the resistance of R2 is positively correlated with temperature. Therefore, if the resistance of R1 is fixed, the resistance ratio of R1 to R2 is negatively correlated with temperature. Thus, the bridge balance point provided by the differential bridge corresponds to a resistance ratio of 1:M for R1 to R2.

[0045] ② The control switch is used to connect the differential bridge to VCC2 and, based on the PWM signal V... PWM Control whether the differential bridge is connected to VCC2.

[0046] The recommended control switch is a Darlington transistor switch based on a transistor design, which utilizes V... PWM By controlling the conduction time of the transistor per unit time, the duration of VCC2 being connected by the differential bridge per unit time is controlled.

[0047] In this embodiment 1, the control switch uses NPN transistors Q1~Q2.

[0048] like Figure 2 As shown, the positive terminals of Q1 and Q2 are connected to VCC2; the base of Q1 serves as the control terminal of the control switch, and its negative terminal is connected to the base of Q2; the negative terminal of Q2 is connected to the first terminal of R1.

[0049] Therefore, when the control terminal of the control switch is at a high level, the control switch is turned on, and the differential bridge is connected to VCC2; when the control terminal of the control switch is at a low level, the control switch is turned off, and the differential bridge is disconnected from VCC2.

[0050] Of course, the control switch can be designed with other switches, but it should meet the control logic requirements mentioned above.

[0051] When the differential bridge is connected to VCC2, the first and second loads have the same voltage, and a voltage V1 is generated between R1 and R2, and a voltage V2 is generated between R3 and R4.

[0052] ③ The voltage follower circuit includes: voltage follower U1~U2.

[0053] Voltage followers do not provide attenuation or amplification—they only provide buffering. Therefore, U1 is used to output the voltage V1 between R1 and R2; U2 is used to output the voltage V2 between R3 and R4. like Figure 2As shown, the positive input terminal of U1 is connected to the second terminal of R1, the output terminal is connected to the negative input terminal and used to output V1, and both the positive and negative power supply terminals are connected to VCC1. The positive input terminal of U2 is connected to the second terminal of R3, the output terminal is connected to the negative input terminal and used to output V2, and both the positive and negative power supply terminals are connected to VCC1.

[0054] ④ The instrumentation amplifier is used to: provide an adjustable differential gain, and differentially amplify V1 and V2 to obtain the amplified signal V. big .

[0055] like Figure 2 As shown, the instrumentation amplifier can be designed to include: operational amplifiers U3~U5, fixed resistors R7~R12, and variable resistor R5.

[0056] The positive input terminal of U3 is connected to the output terminal of U1, the negative input terminal is connected to the first terminal of R5 and the first terminal of R8, the output terminal is connected to the second terminal of R8 and the first terminal of R9, and both the positive and negative power supply terminals are connected to VCC1. The positive input terminal of U4 is connected to the output terminal of U2, the negative input terminal is connected to the second terminal of R5 and the first terminal of R7, the output terminal is connected to the second terminal of R7 and the first terminal of R10, and both the positive and negative power supply terminals are connected to VCC1. The positive input terminal of U5 is connected to the second terminal of R9 and the first terminal of R11, the negative input terminal is connected to the second terminal of R10 and the first terminal of R12, and the output terminal is connected to the second terminal of R12 and used to output V. big Both the positive and negative power supply terminals are connected to VCC1; the second terminal of R11 is grounded to GND.

[0057] It should be noted that R5 is used to adjust the differential amplification factor, thereby changing the time ΔT2 from the first time the bridge reaches its equilibrium point to the constant temperature. The resistance of R5 is positively correlated with the differential amplification factor and negatively correlated with ΔT2.

[0058] In other words, the smaller the value of R5, the shorter the oscillation process from the bridge equilibrium point to the isothermal point. Generally, R5 is preset according to the actual situation. In this embodiment 1, R5 is 10Ω, and the differential amplification factor is 200 times.

[0059] ⑤ The differential circuit is used to: separate the sawtooth wave signal ST from V big Perform differential processing to obtain the differential output V st .

[0060] like Figure 2 As shown, the differential circuit can be designed to include: a sawtooth wave generator XFG, a differential amplifier U6, and fixed resistors R13~R15.

[0061] XFG is used to: provide ST; where the trough of ST is 0. See also Figure 3 The waveform of ST is a sawtooth wave, and it remains above the zero point. Combined with... Figure 2 The connection relationship of XFG is as follows: the positive output terminal of XFG is connected to the first terminal of R13, and the COM terminal is grounded to GND; the second terminal of R15 is grounded to GND; the second terminal of R13 and the first terminal of R15 are connected to the positive input terminal of U6.

[0062] In this Example 1, the Vpp (peak-to-peak value) of ST is 2.5V. f The frequency is 3Hz and the bias is 2.5V.

[0063] The positive input terminal of U6 is connected to XFG via parallel resistors R13 and R15. The negative input terminal is connected to the second terminal of R14 and the first terminal of R16. The output terminal is connected to the second terminal of R16 and is used to output V. st Both the positive and negative power supply terminals are connected to VCC1; the first terminal of R14 is connected to the output terminal of U5.

[0064] In other words, V st By subtracting V from ST big Produced.

[0065] ⑥ The comparator output circuit is used to: convert V st Compare with zero potential to obtain V PWM .

[0066] like Figure 2 As shown, the comparison output circuit can be designed to include: a fixed resistor R18, a comparator U7, and a fixed resistor R17.

[0067] The first terminal of R18 is connected to the output terminal of U6; The positive input terminal of U7 is connected to the second terminal of R18, the negative input terminal is grounded (GND), and the output terminal is connected to the control terminal of the control switch via R17 to output V. PWM It is then applied to the control terminal of the control switch, with both the positive and negative power supply terminals connected to VCC1.

[0068] In addition, the fixed resistors R7 to R18 in the above circuit are used for balancing the circuit, and their resistance values ​​can be determined according to the actual situation.

[0069] Therefore, connecting the heating control module based on the above circuit layout with R2, VCC1, and VCC2 forms a PWM adaptive control heating device based on differential guidance. Thus, according to T... set Adjust the resistance of R1 to T. set / M, the aforementioned heating circuit and heating device will automatically perform PWM modulation: The control switch is initially in the off state, and the instrumentation amplifier and differential circuit initially output a low level; XFG starts generating ST; U6 differentially divides ST with zero potential (i.e., the output of the differential circuit at this time), and outputs V... st Above zero potential; U7 will V st Compared to zero potential, the output V PWM The voltage level remains high, which turns on the control switch, connects VCC2 to the differential bridge for power, and R2 starts heating. The temperature of R2 is affected by the heating power and its own heat dissipation.

[0070] In this circuit, resistors R1 and R2 divide the voltage to generate V1; resistors R3 and R4 divide the voltage to generate V2; V1 and V2 are output to the differential circuit via U1 and U2 respectively; the differential circuit amplifies V1 and V2 to generate V0. big .

[0071] 1. Assuming the initial temperature of R2 is less than T set For example: When the resistance of R2 is at a lower value, the resistance ratio of R1 to R2 will be greater than 1 / M; therefore, V1 < V2, V big The voltage is negative; U6 differentially divides ST with the negative voltage and outputs V. st Still above zero potential; U7 will V st Compared to zero potential, the output V PWM The circuit remains at a high level, keeping the control switch on. R2 will heat up at high power – the amount of heat generated is much greater than the amount of heat dissipated, and the temperature of R2 will rise.

[0072] As the temperature of R2 increases, its resistance also increases, V1 increases and approaches V2, and the resistance ratio of R1 to R2 decreases and approaches 1 / M; see above, V PWM It remains at a high level, and R2 continues to heat at high power.

[0073] When the resistance ratio of R1 to R2 first reaches 1 / M, the circuit reaches the bridge balance point for the first time; at this time, V1=V2, which also marks the beginning of high-gain suppression and the end of continuous high-power heating, after which PWM duty cycle modulation is performed: Due to the lag in heating, R2 will not reach temperature equilibrium at the same time as the first time it reaches the bridge equilibrium point; the temperature of R2 will continue to rise, and the resistance of R2 will continue to increase, causing the resistance of R1 and R2 to be less than 1 / M. Therefore, V1 > V2, and the differential circuit will amplify the difference between V1 and V2 to generate a positive potential V. big U6 will connect ST and V big Performing a differential operation—that is, differentiating a continuously increasing positive potential wave; since ST is a sawtooth wave, see [reference needed]. Figure 4 V stThe overall waveform remains a sawtooth pattern and will gradually shift towards zero potential, eventually becoming negative; U7 will V st Compared to zero potential, the output V PWM A low level may also occur, causing the control switch to turn off and R2 to experience an interrupted power supply. It should be noted that due to V... PWM A high level still exists, and R2 is still connected to power; however, the duration of the control switch's conduction will vary with V. st The amplitude of the shift towards zero potential changes and shortens, eventually achieving a balance between heat generation and heat dissipation at a certain moment, thus achieving high gain suppression. After the temperature of R2, it enters dynamic equilibrium.

[0074] II. assuming the initial temperature of R2 is greater than T set For example: When the resistance of R2 is at a high value, the resistance ratio of R1 to R2 will be less than 1 / M; therefore, V1 > V2, and the differential circuit will amplify the difference between V1 and V2 to generate a positive potential V. big U6 will connect ST and V big Differential output V st The proportion of negative potential is large; U7 will V st Compared to zero potential, the output V PWM A high percentage of low-level signals result in a longer switch-off time, causing the heating amount of R2 to be less than the heat dissipation, and the temperature of R2 to gradually decrease. Referring to the above, the following will still be based on ST and V. big Perform differential calculations to ensure that the temperature of R2 eventually reaches dynamic equilibrium.

[0075] The underlying control mechanism of the above process is as follows: The energy conservation equation for R2 is: ; In the formula, t represents the current time; P in (.) represents the real-time heating power of R2; m represents the mass of R2; c p T represents the specific heat capacity of R2; s (.) indicates the real-time temperature of R2; T amb σ represents the ambient temperature; h represents the convective heat transfer coefficient; σ represents the radiative heat transfer coefficient; A represents the surface area of ​​R2; ε represents the emissivity of R2.

[0076] In fact, T s (t) and T set There exists a real-time temperature difference e(t), that is: e(t) = T set -T s e(t); t represents the current time, and the differential bridge converts e(t) into the real-time voltage difference e. u (t); that is, e u (t)= Uset -U s (t); U set For R2 temperature to reach T set Voltage across the terminals; U s (.) indicates the real-time voltage across R2.

[0077] Therefore, the energy conservation equation for R2 is transformed into: .

[0078] Therefore, we have: 1. When e(t) is large, the circuit provides the maximum or near-maximum power P. max At this point, most of the energy is used to raise the temperature of R2, that is... This allows for rapid heating.

[0079] In other words, R2 satisfies the following at this time: .

[0080] 2. When e(t) enters a very small interval Δe, the circuit enters PWM duty cycle modulation. At this time, P in (.) will be in V big Under precise control, the temperature of R2 is dynamically and slightly higher than the heat dissipation—a small surplus power ΔP is used to compensate for heat loss and stabilize the temperature of R2 at T. set Nearby, i.e. This is the key to achieving high-precision temperature control and low-power self-sustaining operation.

[0081] In other words, R2 satisfies the following at this time: .

[0082] 3. When e(t) is negative, the circuit will either cut off or significantly reduce P. in (.), R2 achieves cooling through heat dissipation, that is until e(t) returns to Δe.

[0083] In other words, R2 satisfies the following at this time: .

[0084] As can be seen from the above description, this embodiment 1 also discloses a PWM adaptive control heating method based on differential guidance, which is applied to the above-mentioned PWM adaptive control heating circuit based on differential guidance or the above-mentioned PWM adaptive control heating device based on differential guidance.

[0085] Specifically, the differential-guided PWM adaptive control heating method includes: According to T set Adjust the resistance of R1 to T.set / M.

[0086] It can be seen that the above heating method is extremely simple to operate and requires very little skill from the operator, making it very suitable for widespread use.

[0087] Example 2 This embodiment 2 aims to verify the performance of the heating circuit, device, and method provided in embodiment 1, in order to demonstrate their effectiveness and superiority.

[0088] See Figure 5 In this embodiment 2, an experimental platform was constructed: 1. R2 should use MCH ceramic heating element; 2. A shell for housing R2 is manufactured using 3D printing, and heat insulation is filled between R2 and the shell to reduce heat loss; 3. Place the temperature sensor (using PT100 or thermocouple) onto the surface of R2 for temperature measurement; the temperature sensor is connected to the host computer via a temperature acquisition card to realize temperature signal acquisition and analysis; 4. Based on the heating circuit, process the PCB board to obtain a physical heating control module, and connect VCC1, VCC2, and R2 to form a heating device.

[0089] 5. The heating control module is connected to the host computer via an NI data acquisition card to acquire and analyze some key signals of the heating control module.

[0090] It should be noted that the above-mentioned experimental platform is equipped with relevant data acquisition components to verify the effect of the heating device; these data acquisition components are not needed in actual use.

[0091] Based on the above experimental platform, different T values ​​were selected. set And ensure that the initial temperature of R2 is less than T. set The heating device is controlled according to the method in Example 1. The temperature curve of R2 is shown below. Figure 6 It can be seen that the heating device will rapidly heat R2 in the initial stage, quickly reaching T. set Nearby, the temperature of R2 gradually stabilized, with temperature variations controlled within ±1℃ or even higher.

[0092] Specifically, T set Taking 40℃ as an example, the voltage change across R2 is as follows: Figure 7 As shown, V big Voltage changes as follows Figure 8 As shown, V st Voltage changes as follows Figure 9 As shown, V PWM Voltage changes as follows Figure 10 As shown, all conform to the working process description of Example 1.

[0093] The results above show that the heating circuit, device, and method provided in Example 1 achieve millisecond-level fast dynamic response and high-precision steady-state control of R2. It can provide extremely high gain suppression and fine stepless power fine-tuning near the target temperature point, achieving temperature stability of ±1℃ or even higher, without continuous oscillation.

[0094] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A PWM adaptive control heating circuit based on differential guidance, characterized in that, It is used for temperature control of heating element R2, whose resistance is positively correlated with temperature; It includes: A differential bridge includes: fixed resistors R3~R4, and a variable resistor R1; R1 is used to form the first circuit in series with R2, and is adjusted according to the target temperature T of R2. set Adjust its resistance value to T set / M; R3 and R4 are connected in series to form the second path; the first path and the second path are connected in parallel; the resistance ratio of R3 to R4 is 1:M; M>0; the bridge balance point provided by the differential bridge corresponds to: the resistance ratio of R1 to R2 is 1:M; A Darlington transistor switch is used to connect the differential bridge to the power supply VCC2 and to operate according to the PWM signal V. PWM Control whether the differential bridge is connected to VCC2; and The PWM drive circuit, which operates under the power supply VCC1, includes: A voltage follower circuit includes: voltage followers U1~U2; U1 is used to output the voltage V1 between R1 and R2; U2 is used to output the voltage V2 between R3 and R4; An instrumentation amplifier is used to provide an adjustable differential gain and differentially amplify V1 and V2 to obtain the amplified signal V. big ; A differential circuit is used to: separate the sawtooth wave signal ST from V. big Perform differential processing to obtain the differential output V st ; The comparator output circuit is used to: convert V st Compare with zero potential to obtain V PWM .

2. The PWM adaptive control heating circuit based on differential guidance according to claim 1, characterized in that, The first end of R1 is connected to the first end of R3 and connected to VCC2 through a Darlington transistor switch. The second end is used to connect to the first end of R2. The second end of R2 is used to ground GND. The second end of R3 is connected to the first end of R4, and the second end of R4 is grounded GND.

3. The PWM adaptive control heating circuit based on differential guidance according to claim 2, characterized in that, Darlington transistor switches include: NPN transistors Q1~Q2; The positive terminals of Q1 and Q2 are connected to VCC2; the base of Q1 serves as the control terminal of the Darlington transistor switch, and its negative terminal is connected to the base of Q2; the negative terminal of Q2 is connected to the first terminal of R1. When the control terminal of the Darlington transistor switch is high, the Darlington transistor switch is turned on. When the control terminal of the Darlington transistor switch is at a low level, the Darlington transistor switch is turned off.

4. The PWM adaptive control heating circuit based on differential guidance according to claim 3, characterized in that, The positive input terminal of U1 is connected to the second terminal of R1, the output terminal is connected to the negative input terminal and used to output V1, and both the positive and negative power supply terminals are connected to VCC1. The positive input terminal of U2 is connected to the second terminal of R3, the output terminal is connected to the negative input terminal and used to output V2, and both the positive and negative power supply terminals are connected to VCC1.

5. The PWM adaptive control heating circuit based on differential guidance according to claim 4, characterized in that, The instrumentation amplifiers include: operational amplifiers U3~U5, fixed resistors R7~R12, and variable resistor R5; The positive input terminal of U3 is connected to the output terminal of U1, the negative input terminal is connected to the first terminal of R5 and the first terminal of R8, the output terminal is connected to the second terminal of R8 and the first terminal of R9, and both the positive and negative power supply terminals are connected to VCC1. The positive input terminal of U4 is connected to the output terminal of U2, the negative input terminal is connected to the second terminal of R5 and the first terminal of R7, and the output terminal is connected to the second terminal of R7 and the first terminal of R10. Both the positive and negative power supply terminals are connected to VCC1. R5 is used to adjust the differential amplification factor to change the time ΔT2 from the first time the bridge balance point is reached to constant temperature. The resistance value of R5 is positively correlated with the differential amplification factor and negatively correlated with ΔT2. The positive input terminal of U5 is connected to the second terminal of R9 and the first terminal of R11, the negative input terminal is connected to the second terminal of R10 and the first terminal of R12, and the output terminal is connected to the second terminal of R12 and used to output V. big Both the positive and negative power supply terminals are connected to VCC1; the second terminal of R11 is grounded to GND.

6. The PWM adaptive control heating circuit based on differential guidance according to claim 5, characterized in that, The differential circuit includes: a sawtooth wave generator XFG, a differential amplifier U6, and fixed resistors R13~R15; XFG is used to: provide ST; where the trough of ST is 0; The positive input terminal of U6 is connected to XFG via parallel resistors R13 and R15. The negative input terminal is connected to the second terminal of R14 and the first terminal of R16. The output terminal is connected to the second terminal of R16 and is used to output V. st Both the positive and negative power supply terminals are connected to VCC1; the first terminal of R14 is connected to the output terminal of U5.

7. The PWM adaptive control heating circuit based on differential guidance according to claim 6, characterized in that, The positive output terminal of XFG is connected to the first terminal of R13, and the COM terminal is grounded to GND; the second terminal of R15 is grounded to GND; the second terminal of R13 and the first terminal of R15 are connected to the positive input terminal of U6.

8. The PWM adaptive control heating circuit based on differential guidance according to claim 7, characterized in that, The comparator output circuit includes: a fixed resistor R18, a comparator U7, and a fixed resistor R17; The first terminal of R18 is connected to the output terminal of U6; The positive input terminal of U7 is connected to the second terminal of R18, the negative input terminal is grounded (GND), and the output terminal is connected to the control terminal of the Darlington transistor switch via R17 to output V. PWM It is then applied to the control terminal of the Darlington transistor switch, with both the positive and negative power supply terminals connected to VCC1.

9. A PWM adaptive control heating device based on differential guidance, characterized in that, It includes: heating element R2, power supply VCC1~VCC2, and heating control module; The heating control module adopts the layout of the differential-guided PWM adaptive control heating circuit as described in any one of claims 1-8, and is connected to R2, VCC1, and VCC2.

10. A PWM adaptive control heating method based on differential guidance, characterized in that, Its application is in the differential-guided PWM adaptive control heating circuit as described in any one of claims 1-8, or in the differential-guided PWM adaptive control heating device as described in claim 9; The differential-guided PWM adaptive control heating method includes: According to T set Adjust the resistance of R1 to T. set / M.

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