Electric heating temperature control system and method

Abstract

The present invention discloses an electric heating temperature control system and method, belonging to the field of electric heating control. The electric heating temperature control system includes a heating device having an electric heating element, a heating subsystem, a temperature detection module, and a processing module. The heating subsystem is configured to form a heating circuit with the electric heating element. The temperature detection module is configured to convert the temperature of the electric heating element into a thermoelectric signal. The processing module is configured to control the on / off state of the heating subsystem and to perform PID control of the temperature of the electric heating element based on the thermoelectric signal. The present invention implements overtemperature protection for the electric heating element.

Description

Technical Field

[0001] The present invention relates to the field of electric heating control, and in particular to an electric heating temperature control system and method. Background Art

[0002] When powered, electric heating elements generate heat, which is then transferred to a load to heat the medium. Heating devices based on electric heating elements are widely used, such as heating rods and heating blankets.

[0003] In existing heating rods and heating blankets, the heating element is often directly connected to the heating power supply. When the power supply is turned on, the heating element heats up. When the power supply is turned off, no current flows through the element, and heating stops. This continuous heating element presents a risk of overheating. A circuit fault can also cause the element to continue heating, and overheating can easily lead to safety accidents. Therefore, a safer and more reliable electric heating temperature control system is necessary. Summary of the Invention

[0004] The purpose of this application is to provide an electric heating temperature control system and method, which improves the reliability of the system by reducing the risk of overheating of electric heating elements.

[0005] To achieve the above objectives, the present invention provides the following technical solutions.

[0006] An electric heating temperature control system includes a heating device having an electric heating element, a heating power supply, a heating subsystem, a temperature detection module, and a processing module;

[0007] The heating subsystem is used to form a heating circuit with the electric heating element and the heating power supply;

[0008] The temperature detection module is used to convert the temperature of the electric heating element into a thermoelectric signal;

[0009] The processing module is used to input the first signal and the second signal into the heating subsystem to control the on and off of the heating circuit, and is also used to perform PID control on the temperature of the electric heating element according to the thermoelectric signal. In the PID control, the thermoelectric signal is used as feedback to adjust the first signal and / or the second signal.

[0010] Optionally, the heating subsystem includes a heating power supply, an input power control module and a program heating control module;

[0011] The input power control module is used to control the connection and disconnection between the positive electrode of the heating power supply and the electric heating element according to the first signal transmitted by the processing module;

[0012] The program heating control module is used to control the connection and disconnection between the negative electrode of the heating power supply and the electric heating element according to the second signal transmitted by the processing module;

[0013] The second signal is a pulse signal, and the heating subsystem further includes a program heating control protection module, which is used to disconnect the heating circuit when a fault occurs in the second signal.

[0014] Optionally, the input power control module includes:

[0015] a first MOS transistor, wherein the source electrode of the first MOS transistor is connected to the positive electrode of the heating power supply, and the drain electrode of the first MOS transistor is connected to the electric heating element;

[0016] A first photoelectric coupler, used to control the first MOS tube to be turned on and off;

[0017] The first transistor is configured to drive the first photocoupler to be turned on and off according to the first signal.

[0018] Optionally, the program heating control module includes:

[0019] a second MOS transistor, wherein the source of the second MOS transistor is connected to the negative electrode of the heating power supply, and the drain of the second MOS transistor is connected to the electric heating element;

[0020] A second photocoupler, used to control the on and off of the second MOS tube;

[0021] The second transistor is used to drive the second photocoupler to be turned on and off according to the second signal.

[0022] Optionally, the program heating control protection module includes an input side protection unit, and the input side protection unit is used to disconnect the path between the input power control module and the electric heating element when the second signal changes from a pulse signal to a low level signal;

[0023] The program heating control protection module also includes an output side protection unit, which is used to control the program heating control module to disconnect the path between the negative pole of the heating power supply and the electric heating element when the second signal changes from a pulse signal to a normally high level signal or a normally low level signal.

[0024] Optionally, the input side protection unit includes:

[0025] a third MOS transistor, wherein the source of the third MOS transistor is connected to the drain of the first MOS transistor;

[0026] A third triode, used to drive the third MOS tube;

[0027] a first charge-discharge unit, configured to charge when a high level is input to the program heating control module, and discharge the base of the third transistor when a low level is input to the program heating control module;

[0028] During one cycle of the second signal, the charge amount of the input side protection unit in the high level stage is able to maintain the positive electrode of the input power control module and the electric heating element in the low level stage in a conductive state;

[0029] Optionally, the output side protection unit includes:

[0030] a second charge and discharge unit connected to the emitter of the second photoelectric coupler; when the program heating control module inputs a high level, the second charge and discharge unit charges slowly, and when the program heating control module inputs a low level, the second charge and discharge unit discharges quickly;

[0031] A first voltage comparator includes a first channel, an inverting input of the first channel is connected to the second charge and discharge unit, and a non-inverting input of the first channel is a first fixed voltage, wherein when the second control signal is a pulse signal, the first fixed voltage is greater than the voltage of the second charge and discharge unit, and after the second signal becomes high for a period of time, the first fixed voltage is less than the voltage of the second charge and discharge unit; the first voltage comparator also includes a second channel, an inverting input of the second channel is connected to the output of the temperature detection protection module, a non-inverting input of the second channel is connected to the second fixed voltage, and the second channel and the first channel use wired-AND logic;

[0032] a fourth triode, wherein: a base of the fourth triode is connected to the output of the first channel, an emitter is connected to the gate of the second MOS transistor, and a collector is grounded; wherein, when the first fixed voltage is less than the voltage of the second charge and discharge unit, the emitter and collector of the fourth triode are turned on, and the second MOS transistor is turned off.

[0033] Optionally, the temperature detection module includes:

[0034] a thermistor, mounted on the electric heating element;

[0035] The operational amplifier unit is used to form a constant current source monitoring circuit with the thermistor and amplify the voltage at the current output end of the thermistor to form the thermoelectric signal.

[0036] Optionally, the processing module includes:

[0037] a first control unit, configured to output a first signal;

[0038] a second control unit, configured to output a second signal;

[0039] The PID control unit is electrically connected to the temperature detection module, the first control unit and the second control unit respectively; when the electric heating element reaches the target temperature, the PID control unit performs PID control on the heating circuit according to the thermoelectric signal.

[0040] An electric heating temperature control method is implemented using the electric heating temperature control system as described in any one of the above items, and the control method comprises the following steps:

[0041] S10, controlling the operation of the heating circuit;

[0042] S20, determining whether the temperature of the electric heating element reaches the target temperature, if so, executing step S30, otherwise returning to step S10;

[0043] S30, performing PID control on the temperature of the electric heating element, and executing step S40 when a stop instruction is detected;

[0044] S40: Control the heating circuit to be disconnected.

[0045] Optionally, step S10 specifically includes the following steps:

[0046] The processing module is controlled to output a high-level first signal to the input power control module of the heating subsystem, and to input a pulse waveform second signal to the program heating control module of the heating subsystem, so that the positive and negative poles of the heating element and the heating power supply of the heating subsystem are turned on.

[0047] Optionally, the following steps are further included between step S10 and step S20:

[0048] S11. Determine whether the temperature is abnormal. If so, execute step S40; otherwise, execute step S20.

[0049] Optionally, the following steps are further included before step S10:

[0050] S071, control processing module operation;

[0051] S081, the processing module starts the temperature detection module and determines whether the temperature of the electric heating element is abnormal. If so, execute step S40; otherwise, execute step S091;

[0052] S091. Determine whether there is a heating instruction. If so, execute step S10; otherwise, return to step S081.

[0053] An electric heating temperature control method is implemented using the electric heating temperature control system as described in any one of the above items, and the control method comprises the following steps:

[0054] a. Obtaining the current temperature and target temperature of the electric heating element, and calculating the time T required for the electric heating element to reach the target temperature from the current temperature;

[0055] b. controlling the operation of the heating circuit and recording the operation time t of the heating circuit;

[0056] c. When t ≥ T, execute step d, otherwise return to step b;

[0057] d. Determine whether the temperature of the electric heating element reaches the target temperature. If so, execute step e; otherwise, return to step b;

[0058] e. Determine whether the temperature of the electric heating element exceeds a first target temperature threshold; if so, proceed to step g; otherwise, proceed to step f;

[0059] f. Performing PID control on the temperature of the electric heating element, and executing step g when a stop instruction is detected;

[0060] g. Control the heating circuit to disconnect.

[0061] Compared with the prior art, the present invention has the following advantages:

[0062] In this electric heating temperature control system, a heating subsystem is provided between the electric heating element and the heating power supply. The heating subsystem is controlled by the first and second signals output by the processing module, thereby improving system reliability. In the electric heating temperature control method, a thermoelectric signal is obtained by the temperature detection module, and the temperature of the electric heating element is determined based on the thermoelectric signal. When the electric heating element reaches the target temperature, the processing module controls the electric heating element to perform PID control, thereby achieving a constant temperature and preventing overheating of the electric heating element. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The technical features and advantages of the present invention will be more fully understood by referring to the following detailed description in conjunction with the accompanying drawings.

[0064] Figure 1 A circuit diagram of the input power control module of the present invention;

[0065] Figure 2 This is a circuit diagram of the program heating control module of the present invention;

[0066] Figure 3 This is a circuit diagram of the input side protection unit and the program heating control module of the present invention;

[0067] Figure 4 This is a circuit diagram of the program heating control protection module and the program heating control module of the present invention;

[0068] Figure 5The circuit diagram of the temperature detection module of the present invention is shown in FIG. 1 , wherein the thermistor adopts a positive temperature coefficient;

[0069] Figure 6 The circuit diagram of the temperature detection module of the present invention, wherein the thermistor adopts a negative temperature coefficient;

[0070] Figure 7 This is a circuit diagram of the temperature detection protection module of the present invention, wherein the thermistor adopts a positive temperature coefficient;

[0071] Figure 8 This is a circuit diagram of the temperature detection protection module of the present invention, in which the thermistor adopts a negative temperature coefficient. DETAILED DESCRIPTION

[0072] Unless otherwise defined, technical or scientific terms used in this specification and claims shall have the ordinary meanings understood by persons of ordinary skill in the art to which this invention belongs. In the drawings, some locations in the circuits are identified by combinations of letters. For ease of description, the following description combines these symbols.

[0073] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified with "first," "second," etc., may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0074] An electric heating temperature control system includes a heating device having an electric heating element, a heating power supply, a heating subsystem, and a processing module. The processing module is used to control the heating subsystem and the electric heating element to form a heating loop.

[0075] The heating device can be a heating rod, carpet, or other device requiring electrical heating. The heating element can be a resistance wire or other type. The heating device can be equipped with a load, and the heating element is used to directly or indirectly heat the load. For example, a ceramic heating rod consists of a ceramic body, a heating element, and a load. The heating element and the load are separately mounted on the ceramic body. The heating element transfers heat energy directly to the ceramic body, and then further to the load. The load can be a metal block or supported by ceramic material.

[0076] The processing module is used to implement the control functions of the electric heating temperature control system and may include one or more chips capable of running programs, such as a CPU, MCU, DSP, SOC, or single-chip microcomputer. The processing module includes a first control unit and a second control unit. The first control unit and the second control unit can be implemented using two separate chips or can be arranged in a single chip. One pin of the first control unit is used to output a first signal, and one pin of the second control unit is used to output a second signal. The first signal and the second signal serve as two input signals for the heating circuit. Only when the first signal and the second signal both meet the conditions can the heating circuit be turned on and the electric heating element be heated. Otherwise, the heating circuit is disconnected and the electric heating element is not heated. When an abnormality occurs in the electric heating temperature control system, the processing module adjusts one or both of the first signal and the second signal to disconnect the heating circuit, thereby ensuring the safety of the electric heating element and, accordingly, the safety of the heating device.

[0077] The heating subsystem includes an input power control module and a program heating control module; the input power control module is used to control the on and off between the positive pole of the heating power supply and the electric heating element according to the first signal emitted by the processing module; the program heating control module is used to control the on and off between the negative pole of the heating power supply and the electric heating element according to the second signal emitted by the processing module.

[0078] The input power control module has its own power supply to ensure normal operation. Combined with a microcontroller program, the module can be used to control the power supply to the heating element. When the heating element needs to be heated, the input power control module must be turned on. When the heating element does not need to be heated, the input power control module is turned off, achieving on-demand control of the heating element's power input.

[0079] The input power control module is configured to connect the electric heating element and the positive electrode of the heating power supply when the first signal is at a high level, and disconnect the electric heating element and the positive electrode of the heating power supply when the first signal is at a low level.

[0080] refer to Figure 1Understand. The input power control module includes a first MOS tube Q4, a first photocoupler U3 and a first transistor Q7. When the first signal is at a high level, the first transistor Q7 drives the first photocoupler U3 to turn on, and further drives the first MOS tube Q4 to turn on. When the first signal is at a low level, the first transistor Q7, the first photocoupler U3 and the first MOS tube Q4 are cut off. The source of the first MOS tube Q4 is connected to the positive pole of the heating power supply, and the drain is connected to the electric heating element; when the source and drain of the first MOS tube Q4 are turned on, the positive pole of the heating power supply and the electric heating element can be connected, otherwise, the positive pole of the heating power supply and the electric heating element are in a disconnected state, and the heating circuit cannot be turned on. The first photocoupler U3 is used to control the conduction and cutoff of the first MOS tube Q4; the first transistor Q7 is used to drive the first photocoupler U3 to turn on and off according to the first signal.

[0081] The first MOS transistor Q4 is a P-channel enhancement type transistor. When the first MOS transistor Q4 is on, its drain voltage VDD (hereinafter referred to as "power supply VDD") is equal to its source voltage, that is, the voltage of power supply VDD is equal to the voltage of the heating power supply. The gate of the first MOS transistor Q4 is connected to the supply voltage via resistor R11. When the first photocoupler U3 is off, the gate of the first MOS transistor Q4 is at a high level, and the source and drain of the first MOS transistor Q4 are not conducting, and no current flows through the positive electrode of the heating power supply and the electric heating element. In the first photocoupler U3, the emitter is grounded, and the collector is connected to the gate of the first MOS transistor Q4. When the first photocoupler U3 is on, its emitter and collector are connected, causing the gate of the first MOS transistor Q4 to be at a low level, thereby conducting the source and drain of the first MOS transistor Q4. In the absence of other obstacles, current can flow through the positive electrode of the heating power supply and the electric heating element. The first transistor Q7 is an NPN transistor. The emitter of the first transistor Q7 is grounded and connected to the base of the first transistor Q7 via resistor R10. The base of the first transistor Q7 is connected to the processing module via resistor R22, that is, the CTRL signal originates from the control pin of the processing module. The collector of the first transistor Q7 is connected to a voltage 3V3 via a first photocoupler U3 and a resistor R33 (a current-limiting resistor at the front end of the photocoupler). When the collector and emitter of the first transistor Q7 are turned on, the first photocoupler U3 is turned on. When the collector and emitter of the first transistor Q7 are turned off, the first photocoupler U3 is in the off state.

[0082] As can be seen from the above, the CTRL signal can be controlled to be high or low through the processing module. When the CTRL signal is high, the base and emitter voltage Vbe of the first transistor Q7 is greater than 0.7V (the turn-on voltage of the first transistor Q7) through the voltage division of the resistors R22 and R10, and the collector and emitter Vce of the first transistor Q7 are turned on. The voltage 3V3, the resistor R33, and the first transistor Q7 form a current path, so that the rear end collector end of the first photocoupler U3 is turned on, the gate of the first MOS transistor Q4 is at a low voltage, the source and drain of the first MOS transistor Q4 are turned on, and the power supply VDD voltage is approximately equal to the voltage VCC of the heating power supply. On the contrary, when the CTRL signal is at a low level, the base and emitter voltages Vbe of the first transistor Q7 are approximately 0, the collector and emitter Vce of the first transistor Q7 are cut off, the voltage 3V3, the resistor R33, and the first transistor Q7 cannot form a current path, the first photocoupler U3 is cut off, the first MOS transistor Q4 is cut off, and the power supply VDD voltage is approximately 0.

[0083] refer to Figure 2 The program heating control module includes a second MOS transistor Q1, a second photocoupler U2, and a second transistor Q6. The source of the second MOS transistor Q1 is connected to the negative terminal of the heating power supply, and the drain is connected to the heating element. The second photocoupler U2 is used to control the conduction and cutoff of the second MOS transistor Q1. The second transistor Q6 is used to drive the second photocoupler U2 to conduct and cut off according to the second signal.

[0084] The second MOS transistor Q1 is an N-channel enhancement type transistor. Its gate is grounded via resistor R8, ensuring that the gate of the second MOS transistor Q1 is at a low level when the second photocoupler U2 is turned off. A resistor R25 is provided between the gate of the second MOS transistor Q1 and the emitter of the second photocoupler U2. Resistor R8 acts as a pull-down resistor between the gate of the second MOS transistor Q1 and resistor R25. A pull-down resistor R1 is also provided between the emitter of the second photocoupler U2 and resistor R25. In the second photocoupler U2, the collector is connected to the supply voltage via resistor R21, and the emitter is connected to the gate of the second MOS transistor Q1. The second transistor Q6 is an NPN transistor. Its base is connected to the second control unit of the processing module via resistor R20, meaning that the HEAT signal originates from the processing module. The collector is connected to the supply voltage via the second photocoupler U2 and resistor R28. The emitter is grounded and connected to the base of the second transistor Q6 via resistor R30.

[0085] When HEAT is at a high level, the collector and emitter of the second transistor Q6 are conductive, forming a current path through resistors R20, R30, the second transistor Q6, resistor R28, and the front end of the second photocoupler U2. The collector and emitter of the second photocoupler U2 are also conductive. Resistors R21 and R1 divide the supply voltage VCC at the collector of the second photocoupler U2. The voltage Vheato at the emitter of the second photocoupler U2 is less than the supply voltage connected to the collector of the second photocoupler U2 and greater than 0. This voltage Vheato is defined as the first voltage. Conversely, when HEAT is at a low level, as in the pulse waveform, the collector and emitter of the second transistor Q6 are cut off. Resistors R20, R30, the second transistor Q6, resistor R28, and the front end of the second photocoupler U2 cannot form a current path. The collector and emitter of the second photocoupler U2 are cut off, and the voltage Vheato at the emitter of the second photocoupler U2 is approximately 0V due to the pull-down effect of resistor R1. The resistor R25 and the resistor R8 further divide the voltage Vheato to control the on and off of the MOS transistor Q1 , that is, when Vheato is approximately a first voltage, the second MOS transistor Q1 is turned on, and when Vheato is approximately 0V, the second MOS transistor Q1 is turned off.

[0086] The electric heating element of a small ceramic heating rod can be equivalent to a resistor with a rated resistance of 12Ω. Its working condition is that it can generate heat when the rated voltage is applied to both ends. Figure 2 In the figure, resistor R9 represents the heating element.

[0087] In one embodiment, the drain of the first MOS transistor Q4 in the input power control module is directly connected to the electric heating element, and the drain of the second MOS transistor Q1 in the program heating control module is directly connected to the electric heating element. When the first signal and the second signal are both high, the power supply VDD, the electric heating element, the second MOS transistor Q1, and the GNDP connected to the second MOS transistor Q1 form a heating circuit through which current flows. When the first signal and / or the second signal are low, the heating circuit is disconnected and no current flows.

[0088] In some other embodiments, the second signal uses a pulse signal instead of a high-level signal and a low-level signal, and the input power control module is not directly connected to the electric heating element. These embodiments are described in detail below.

[0089] The heating subsystem also includes a programmable heating control and protection module, which disconnects the heating circuit if a second signal fails. A second signal failure, such as a pulse signal changing to a permanently high or low level, indicates a second signal failure. If the second signal fails, the heating element may continue heating, potentially causing overheating or other risks. The programmable heating control and protection module protects the electric heating temperature control system, enhancing system safety.

[0090] The program heating control protection module includes an input side protection unit, which is used to disconnect the path between the input power control module and the electric heating element when a second signal fails. Specifically, the input of the input side protection unit is connected to the program heating control module, which is used to disconnect the path between the input power control module and the electric heating element after the second signal changes from a pulse signal to a low level signal.

[0091] When the program heating control module inputs a high level, the input side protection unit is charged and controls the input power control module and the electric heating element to be turned on; when the program heating control module inputs a low level, the input side protection unit discharges until the input power control module and the electric heating element are disconnected, thereby automatically disconnecting the heating circuit after the second signal changes from a pulse signal to a low level signal; within one cycle of the second signal, the charging amount of the input side protection unit in the high level stage can maintain the input power control module and the electric heating element in the on state in the low level stage, thereby ensuring that when the second signal is a normal pulse signal, continuous heating can be achieved between the input power control module and the electric heating element.

[0092] refer to Figure 3 Understand. The input side protection unit includes a third MOS tube Q3, a third transistor Q5 and a first charge and discharge unit. One of the source and drain of the third MOS tube Q3 is connected to the input power control module, and the other is connected to the electric heating element, so that the on and off between the input power control module and the electric heating element is controlled by the state of the third MOS tube Q3; the third transistor Q5 is used to drive the third MOS tube Q3; the first charge and discharge unit is used to charge when the program heating control module inputs a high level, and to discharge the base of the third transistor Q5 when the program heating control module inputs a low level; the frequency of the pulse signal and the discharge constant of the first charge and discharge unit are set to achieve the function of maintaining the input power control module and the electric heating element in the on state in the low level stage within one cycle of the second signal.

[0093] The third MOS transistor Q3 is a P-channel enhancement type transistor. The gate of the third MOS transistor Q3 is connected to the collector of the third triode Q5 via a resistor R27, and is connected to the power supply VDD via a resistor R5 (resistance value 10 kΩ). The resistor R5 is connected in parallel with a capacitor C4. The source of the third triode Q5 is connected to the power supply VDD, and the drain of the third MOS transistor Q3 is connected to the electric heating element. Only when the source and drain of the third MOS transistor Q3 are conductive can the positive electrode of the heating power supply be connected to the electric heating element. When the source and drain of the third MOS transistor Q3 are blocked, even if the first MOS transistor Q4 is conductive, the circuit between the heating power supply and the electric heating element cannot pass.

[0094] The third transistor Q5 is of NPN type, the emitter of the third transistor Q5 is grounded, and the base of the third transistor Q5 is connected to the first charge and discharge circuit through a resistor R19 (2K4Ω); the first charge and discharge unit includes a first capacitor C11 and a first charge and discharge resistor R6, the first capacitor C11 is selected to be 2.2μF, and the first charge and discharge resistor R6 is selected to be 10KΩ, achieving the effect of fast charging and slow discharging; the first charge and discharge unit is connected to the program heating control module through a first diode D3, the first charge and discharge unit is connected to the cathode of the first diode D3, and the anode of the first diode D3 is connected to the emitter of the second photocoupler U2.

[0095] When HEAT is a pulse voltage waveform of a set frequency, when the pulse is high, the current passes through the first diode D3, quickly charging the first charge and discharge resistor R6 and the first capacitor C11, and the voltage across the first capacitor C11 increases. When the pulse is low, the first diode D3 is cut off, and the first capacitor C11 is slowly discharged through the first charge and discharge resistor R6, thereby reducing the voltage. The pulse frequency only needs to ensure that the voltage of the first capacitor C11 is not lower than the voltage of the base and emitter Vbe of the third transistor Q5. From the perspective of reliability, the voltage across the first capacitor C11 can be designed to be not lower than 2Vbe, so that the power supply VDD of the electric heating element can be normally turned on during the pulse voltage waveform.

[0096] When HEAT fails and remains at a low level, the voltage Vheato is approximately 0V, that is, Vheato is at a low level. At this time, the first diode D3 is turned off, and the voltage across the first capacitor C11 is discharged through the first charge-discharge resistor R6. When the voltage of the first charge-discharge resistor R6 is lower than the base-emitter voltage Vbe of the third transistor Q5, the third transistor Q5 is turned off, and the gate of the third MOS transistor Q3 is at a high level under the action of the pull-up resistor R5. At this time, the third MOS transistor Q3 is turned off, the power supply VDD cannot be normally output to the resistor R9, the electric heating element cannot be heated, and the circuit is safe.

[0097] When HEAT fails and remains at a high level, the voltage Vheato at the emitter of the second photocoupler U2 is approximately the first voltage, i.e., the voltage Vheato is high. At this time, the voltage passes through the first diode D3 to charge the RC circuit (i.e., the first charge and discharge unit) consisting of the first charge and discharge resistor R6 and the first capacitor C11. When the voltage of the first charge and discharge resistor R6 exceeds the base-emitter voltage Vbe of the third transistor Q5, the third transistor Q5 is turned on, and the gate of the third MOS transistor Q3 is at a low level. At this time, the third MOS transistor Q3 is turned on, and the power supply VDD can be normally output to the resistor R9. At this time, whether the electric heating element is working or not depends on the conduction state of the second MOS transistor Q1.

[0098] The program heating control protection module also includes an output side protection unit, which is arranged on the program heating control module. The output side protection unit is used to control the program heating control module to disconnect the path between the negative pole of the heating power supply and the electric heating element when the second signal changes from a pulse signal to a high level signal.

[0099] When the program heating control module inputs a high level, the output side protection unit charges slowly. When the program heating control module inputs a low level, the output side protection unit discharges quickly. Within one cycle of the second signal, the discharge amount of the output side protection unit in the low level stage is not less than its charging amount in the high level stage.

[0100] refer to Figure 4 The output-side protection unit includes a fourth transistor Q2, a first voltage comparator U1, and a second charge-discharge unit. The fourth transistor Q2 is used to control the conduction and cutoff of the second MOS transistor Q1. When the fourth transistor Q2 is on, the second MOS transistor Q1 is cut off. The first voltage comparator U1 includes a first channel, which is used to drive the fourth transistor Q2. The second charge-discharge unit is used to drive and control the output of the first voltage comparator U1. When the program heating control module input is high, the second charge-discharge unit charges slowly. When the program heating control module input is low, the second charge-discharge unit discharges quickly. After the second control signal changes from a pulse signal to a high-level signal for a period of time, the voltage of the second charge-discharge unit reverses the output of the first voltage comparator U1, further driving the second MOS transistor Q1 to cut off through the fourth transistor Q2.

[0101] The second charge and discharge unit is a two-stage RC charging. Specifically, the resistor R24 ​​is connected to HEATO, the resistor R24 ​​and the resistor R2 are connected in series, and a second capacitor C3 and a third capacitor C10 are arranged between the two. The rear end of the resistor R2 is provided with a fourth capacitor C2. The resistor R24 ​​is also connected in parallel with a second diode D2 and a first charge and discharge resistor R17. A second charge and discharge resistor (that is, the above-mentioned pull-down resistor R1) is provided between the second photocoupler U2 and the second MOS tube Q1. When the program heating control module inputs a low level, the second charge and discharge unit is quickly discharged through the second diode D2, the first charge and discharge resistor R17 and the second charge and discharge resistor in sequence.

[0102] The inverting input of the first channel is connected to the second charge and discharge unit, that is, connected to the resistor R2. The non-inverting input of the first channel is a first fixed voltage. The resistors R4 and R3 divide the voltage of a power supply. The first fixed voltage is set by using the resistance relationship between the resistors R4 and R3. When the second control signal is a pulse signal, the first fixed voltage is greater than the voltage of the second charge and discharge unit. After the second signal becomes a high level for a period of time, the first fixed voltage is less than the voltage of the second charge and discharge unit.

[0103] In the fourth transistor Q2, the base is connected to the output of the first channel, the emitter is connected to the gate of the second MOS transistor Q1 on one hand, and is connected to the base via the resistor R7 on the other hand, and the collector is grounded. When the first fixed voltage is lower than the voltage of the second charge and discharge unit, the emitter and collector of the fourth transistor Q2 are turned on, and the second MOS is turned off.

[0104] When HEAT is a pulse voltage waveform of a set frequency, when the pulse is at a high level, the voltage across the fourth capacitor C2 increases through the slow charging voltage of the resistor R24, the resistor R2, the second capacitor C3, and the third capacitor C10. When the pulse is at a low level, the voltage across the fourth capacitor C2 is quickly discharged through the second diode D2, the resistor R17, and the resistor R1, and the voltage decreases. The frequency of the pulse voltage is designed to be greater than the RC charge and discharge constant of the resistor R24, the resistor R2, the second capacitor C3, the third capacitor C10, and the fourth capacitor C2. Therefore, when the pulse is at a high level, the voltage across the fourth capacitor C2 is designed to be lower than the first fixed voltage of the positive input terminal of the first voltage comparator U1. The output of the first voltage comparator U1 is at a high level. At this time, the conduction state of the second MOS tube Q1 depends on the high level state of the HEAT pulse waveform, and the electric heating element is heated synchronously when the HEAT pulse is at a high level.

[0105] When HEAT is always high, Vheato is approximately a first voltage. That is, when Vheato is high, the voltage flows through a relatively large resistor R24 ​​(using 750 kΩ) to a current loop formed by the second capacitor C3, the third capacitor C10, the resistor R2, and the fourth capacitor C2, slowly charging the second capacitor C3, the third capacitor C10, and the fourth capacitor C2. The charging time depends on the RC coefficient of the resistor R24, the resistor R2, the second capacitor C3, the third capacitor C10, and the fourth capacitor C2. The voltage across the fourth capacitor C2 slowly rises. In the first channel of the first voltage comparator U1, the positive input terminal divides VCC through the resistors R4 and R3. When the voltage across C2 rises above a first fixed voltage, the output of the first voltage comparator U1 is low, the fourth transistor Q2 is turned on, and the second MOS transistor Q1 is turned off due to the low gate voltage. The electric heating element R9 cannot form a current loop with the second MOS transistor Q1 and the third MOS transistor Q3, i.e., the electric heating element cannot heat.

[0106] When HEAT is always at a low level, Vheato is approximately 0V, the output of the first voltage comparator U1 is at a high level, the fourth transistor Q2 is turned off, and the second MOS transistor Q1 is turned off due to the low level caused by the pull-down resistor R8 at the gate. The electric heating element R9 and the second MOS transistor Q1 and the third MOS transistor Q3 cannot form a current loop, that is, the electric heating element cannot heat.

[0107] By heating the electric heating element through the above content, HEAT must be a pulse voltage waveform with a set frequency, and the electric heating element can be heated. This can effectively avoid the control program failure, which causes the HEAT signal to be abnormally high and cause the overtemperature risk to protect the circuit system.

[0108] The electric heating temperature control system also includes a temperature detection module and a temperature detection protection module. The temperature detection module is used to detect the temperature of the electric heating element. The temperature detection protection module is used to control the electric heating element to have no current passing through it when the temperature of the electric heating element exceeds the target temperature.

[0109] refer to Figure 5 The temperature detection module includes a thermistor and an operational amplifier unit U5. The thermistor is installed on the electric heating element. Figure 5 Resistor R12 is used to represent this. Specifically, the thermistor can be mounted on the heating element, or it can be embedded or plugged into the load. A sealed cavity can also be set around the heating element, with the thermistor built into the sealed cavity. When the thermistor is indirectly connected to the heating element, there may be a slight deviation in the thermistor's detection results, which can be compensated by an algorithm. The resistance of the thermistor changes with the temperature of the heating element. The relationship between the thermistor resistance and temperature is set before leaving the factory, and the data is pre-stored in the processing module. The operational amplifier unit U5 is used to form a constant current source monitoring circuit with the thermistor and amplify the voltage at the thermistor's current output terminal to form a thermoelectric signal output. The operational amplifier unit U5 includes an upper channel and a lower channel. The upper channel, the lower channel, and the thermistor form a constant current source monitoring circuit. The lower channel is used to amplify the output of the upper channel and output a thermoelectric signal. The processing module is connected to the output of the lower channel and is used to convert the electrothermal signal into a temperature value.

[0110] The current of the thermistor is constant. When the temperature changes, the voltage at its current output terminal changes, and the voltage input to the temperature detection protection module changes. When the thermistor has a positive temperature coefficient, such as the platinum thermal resistor PT1000A, the voltage at the current output terminal of the thermistor gradually decreases as the temperature rises. When the thermistor has a negative temperature coefficient, such as the MT52A102F3950F00030, the voltage at the current output terminal of the thermistor gradually increases as the temperature rises.

[0111] In the upper channel: the non-inverting input is connected to the first supply voltage 2VREF, where 2VREF is a standard voltage of 2V and the accuracy of the first supply voltage is relatively high; the inverting input is connected to the second supply voltage 3VREF through the first resistor R32, where 3VREF is a standard voltage of 3V and the accuracy of the second supply voltage is relatively high; the output is connected to the inverting input through the thermistor, and the thermistor is connected in series with the first resistor. The first supply voltage is less than the second supply voltage, and the difference between the two is the voltage of the first resistor R32. The current of the thermistor can be calculated according to Ohm's law. When the resistance of the thermistor changes with temperature, the voltage of its current input terminal TEMP+ remains constant, and the voltage of the current output terminal TEMP- changes.

[0112] A first filter capacitor C6 is provided at the first supply voltage connection, and a second filter capacitor C7 is provided at the second supply voltage connection to improve stability. A capacitor C5 is provided at the positive electrode of the operational amplifier unit U5. In one embodiment, the capacitor C5, the first filter capacitor C6, and the second filter capacitor C7 are all ripple capacitors. Figure 5 As shown, the temperature detection module also includes a capacitor C13 as a tuning capacitor for the feedback circuit. Capacitor C13 is a bypass capacitor for thermistor R12. In addition, the first resistor R32 has a precision of 0.01Ω to improve the accuracy of the current output terminal TEMP- and the thermoelectric signal.

[0113] The output of the upper channel is first connected to the positive input of the lower channel and then to the thermistor; the inverting input of the lower channel is grounded through a third resistor R31 and is also connected to the output of the lower channel through a fourth resistor R34. The amplification factor is set by setting the resistance values ​​of the third resistor R31 and the fourth resistor R34. The thermoelectric signal formed after amplification is the voltage of the HTADC; a capacitor C12 can also be connected in parallel with the fourth resistor R34.

[0114] The temperature detection module is further described using thermistors with positive and negative temperature coefficients as examples:

[0115] When the thermistor has a positive temperature coefficient, the thermistor R12 is a PT1000A metal platinum resistor. Its resistance increases with the increase of the sensed temperature. It can be installed on the electric heating element or the load connected to the electric heating element to monitor the temperature of the electric heating element or load in real time. A constant current source monitoring circuit is designed using the operational amplifier unit U5. The positive input terminal of the upper channel is 2VREF (i.e., 2V), and the negative input terminal VTEMP+ is connected to 3VREF (i.e., 3V) through the resistor R32, and forms a feedback circuit with the output of the lower channel. The voltage difference across the resistor R32 is 3VREF-2VREF, i.e., 3V-2V=1V. The resistor R32 is 1KΩ, and the current flowing through the resistor R32 is 1V / 1K=1mA. This 1mA current flows through thermistor R12. At 0°C, the rated resistance of thermistor R12 is 1kΩ. Ohm's law dictates that the voltage difference across R12 is 1mA * 1kΩ = 1V. This means the voltage difference between VTEMP+ and VTEMP- is 1V, so VTEMP- is 1V. VTEMP- passes through the feedback circuit in the lower channel of operational amplifier unit U5. The HTADC voltage, VHTADC, is calculated as ((R31 + R34) / R31) * VTEMP- = 1V * 2 = 2V. VHTADC is connected to the ADC pin of the processing module. The control program reads this voltage and converts it into a temperature value. For example, 2V is equivalent to 0°C. When the temperature of the heating element or load rises, the resistance of thermistor R12 increases, and the voltage drop across it increases. Since the VTEMP+ voltage remains constant at 2VREF, the VTEMP- voltage decreases, synchronizing with the VHTADC voltage. After this conversion, the program detects the temperature increase.

[0116] When the thermistor has a negative temperature coefficient, for ease of description, we introduce Figure 6 , Figure 6 and Figure 5 The difference is that Figure 6 Resistor R50 is used to represent the thermistor. R50 is an MT52A102F3950F00030 negative temperature coefficient thermistor. Its resistance decreases as the sensed temperature increases. It can be installed on a heating element or its connected load to monitor the temperature in real time. A constant current source monitoring circuit is designed using operational amplifier unit U5. Figure 6In the figure, the positive input of the upper channel of the op amp is 2VREF (i.e. 2V), and the negative input VTEMP+ is connected to 3VREF (i.e. 3V) through resistor R32, and forms a feedback circuit with the op amp output (i.e. the output of the lower channel). The voltage difference across resistor R32 is 3VREF-2VREF, i.e. 3V-2V=1V, and the current flowing through resistor R32 is 1V / 1K=1mA. This 1mA current flows through resistor R50. When the resistor R50 is at 0℃, the rated resistance value is 1KΩ. Ohm's law shows that the voltage difference across R50 is 1mA*1KΩ=1V, i.e. the voltage difference between VTEMP+ and VTEMP- is 1V, so the voltage of VTEMP- is 1V. VTEMP- is connected to the resistor R50 through Figure 6 In the feedback circuit of the lower channel of operational amplifier unit U5, VHTADC = ((R31 + R34) / R31) * VTEMP- = 1V * 2 = 2V. VHTADC is connected to the ADC pin of the processing module. The control program can read this voltage and convert it into a temperature value. For example, 2V is equivalent to 0°C. When the temperature of the heating element or load rises, the resistance of resistor R50 decreases, and the voltage drop across it decreases. Since the VTEMP+ voltage remains the same as 2VREF, the VTEMP- voltage increases, which in turn increases the VHTADC voltage. After the conversion, the program detects the temperature increase.

[0117] refer to Figure 4 and Figure 6 、 Figure 7 The input of the temperature detection protection module is connected to the current output terminal TEMP- of the thermistor. The temperature detection protection module controls the state of the second MOS transistor Q1 based on the input voltage. When the temperature of the heating element exceeds a preset temperature (equivalent to the target temperature described below), the temperature detection protection module controls the second MOS transistor Q1 to be turned off.

[0118] The temperature detection protection module controls the state of the second MOS tube Q1 by controlling the output of the protection module through the control program heating. Figure 4 As shown, the first voltage comparator U1 also includes a second channel, the inverting input of the second channel is connected to the output of the temperature detection protection module, and the non-inverting input of the second channel is connected to the second fixed voltage. The second channel and the first channel use wired-AND logic. When the heating element is not overheated, the inverting input of the second channel is less than the second fixed voltage. When the heating element is overheated, the inverting input of the second channel is greater than the second fixed voltage.

[0119] The temperature detection and protection module includes a second voltage comparator U6, a fifth triode Q8, and a third opto-coupler U4. The two inputs of the second voltage comparator U6 are respectively connected to the current output terminal TEMP- of the thermistor and a third fixed voltage. The third fixed voltage is set according to the resistance value and temperature relationship of the thermistor and corresponds to the target temperature. The fifth triode Q8 is driven by the second voltage comparator U6. The third opto-coupler U4 is driven by the fifth triode Q8. One of the collector and emitter of the third opto-coupler U4 is connected to a supply voltage, and the other is connected to the inverting input HT_PT_O of the lower channel in the program heating control and protection module. When the heating element is not overheated, the fifth triode Q8 and the third opto-coupler U4 are cut off. When the heating element is overheated, the fifth triode Q8 and the third opto-coupler U4 are turned on, and the program heating control module is controlled to disconnect the heating element and the negative pole of the heating power supply.

[0120] When the thermistor uses a positive temperature coefficient and a negative temperature coefficient, the temperature detection and protection module will be different. The following will be described in combination with Figure 7 、 Figure 8 respectively.

[0121] As Figure 7 shown, the temperature coefficient of the thermistor uses a positive temperature coefficient. The inverting input of the second voltage comparator U6 is connected to the current output terminal of the thermistor, and the non-inverting input of the second voltage comparator U6 is connected to the third fixed voltage. Figure 7 In U6 is the chip of the second voltage comparator U6. When the non-inverting input terminal is greater than the inverting input terminal, the OUT of the second voltage comparator U6 outputs a high level. Through the voltage division of resistors R23 and R15, the fifth triode Q8 is turned on, and the third opto-coupler U4 is turned on. The voltage of VHT_PT_O is approximately equal to VCC (VCC here is the supply voltage connected to the collector of the third opto-coupler U4). On the contrary, when the non-inverting input terminal is less than the inverting input terminal, the OUT of the second voltage comparator U6 outputs a low level, the fifth triode Q8 is cut off, and the third opto-coupler U4 is cut off. The voltage of VHT_PT_O is approximately 0V under the pull-down effect of the resistor R16. The non-inverting input terminal of the second voltage comparator U6 is a fixed voltage VOP, which is 3V3 divided by resistors R13 and R35, approximately 1.5V. The capacitor C8 is a filter capacitor. The voltage of the inverting input terminal of the second voltage comparator U6 is filtered by resistors R26 and capacitor C14 and connected to VTEMP-, which is a high-impedance input, and the voltage value is the same as VTEMP-. Thus, when VTEMP- < VOP, VTH_PT_O is a high level approximately equal to VCC. When VTEMP- > VOP, VTH_PT_O is a low level approximately equal to 0V. Combined with Figure 4In the lower channel of the first voltage comparator U1 is a comparison circuit (since the outputs of the two channels of the first voltage comparator U1 are connected in wire-AND, the working process of the control circuit at the output end of the first voltage comparator U1 is the same as that of the pulse output protection in the "Programmed Heating Control and Protection Module of the Heating Rod"). When the resistor R12 detects a relatively high temperature, that is, when VTEMP- < VOP, VHT_PT_O is at a high level of about VCC, the fourth triode Q2 conducts, the gate of the second MOS transistor Q1 is at a low level and turns off, and the heating element cannot heat normally; when R12 detects a relatively low temperature, that is, when VTEMP- > VOP, VHT_PT_O is at a low level of about 0V, the fourth triode Q2 turns off, and the second MOS transistor Q1 is normally turned on and off under pulse control, and the heating rod heats normally.

[0122] As Figure 8 shown, the temperature coefficient of the thermistor is a negative temperature coefficient. The non-inverting input of the second voltage comparator U6 is connected to the current output terminal of the thermistor, and the inverting input of the second voltage comparator U6 is connected to the third fixed voltage. Figure 8 In it, U6 is the chip of the second voltage comparator U6. When the non-inverting input terminal is greater than the inverting input terminal, the OUT of the second voltage comparator U6 outputs a high level. Through the voltage division of the resistor R23 and the resistor R15, the fifth triode Q8 conducts, and the fourth opto-coupler conducts, and the voltage of VHT_PT_O is approximately equal to VCC; conversely, when the non-inverting input terminal is less than the inverting input terminal, the OUT of the second voltage comparator U6 outputs a low level, the fifth triode Q8 turns off, and the fourth opto-coupler turns off, and the voltage of VHT_PT_O is approximately 0V under the pull-down action of the resistor R16. The inverting input terminal of the second voltage comparator U6 is the fixed voltage VOP, which is 3V3 divided by the resistors R13 and R35, approximately 1.5V. The capacitor C8 is a filter capacitor. The voltage at the non-inverting input terminal of the second voltage comparator U6 is filtered by the resistor R26 and the capacitor C14 and connected to VTEMP-, which is a high-impedance input, and the voltage value is the same as VTEMP-. Thus, when TEMP- > VOP, VTH_PT_O is at a high level of approximately VCC, and when TEMP- < VOP, VTH_PT_O is at a low level of approximately 0V. Combining Figure 4 In the lower channel of the first voltage comparator U1 in it is a comparison circuit. When the thermistor R50 detects a relatively low temperature, that is, when TEMP- < VOP, VHT_PT_O is at a low level of about 0V, the fourth triode Q2 turns off, and the second MOS transistor Q1 is normally turned on and off under pulse control, and the heating element heats normally; when the thermistor R50 detects a relatively high temperature, that is, when VTEMP- > VOP, VHT_PT_O is at a high level of about 3.3V, the fourth triode Q2 conducts, the gate of the second MOS transistor Q1 is at a low level and turns off, and the heating element cannot heat normally.

[0123] From the above description, it can be seen that the electric heating temperature control system uses circuits to provide multiple protections for the electric heating elements. The processing module also includes a PID unit, which performs PID control on the electric heating temperature control system according to the thermoelectric signal. The PID control unit of the processing module is electrically connected to the temperature detection module, the first control unit and the second control unit respectively; when the electric heating element reaches the target temperature, the PID control unit performs PID control on the heating circuit according to the thermoelectric signal. For detailed information on PID control, please refer to the subsequent description, which is further described below from the perspective of PID control.

[0124] In the electric heating temperature control system, the processing module controls the heating subsystem to heat the electric heating element to meet the temperature requirements of the heating device. The temperature of the electric heating element is converted into a thermoelectric signal through the temperature detection module, and then the processing module analyzes the electric heating signal to obtain the temperature value of the electric heating element. When the electric heating element reaches the target temperature, the processing module performs PID control on the electric heating element to achieve constant temperature control of the electric heating element and prevent the electric heating element from overheating.

[0125] An electric heating temperature control method is implemented using the above-mentioned electric heating temperature control system (an embodiment in which the second signal is a pulse waveform), and the control method includes the following steps:

[0126] S071. Control the processing module to run.

[0127] S081, the processing module starts the temperature detection module and determines whether the temperature of the electric heating element is abnormal according to the thermoelectric signal. If so, execute step S40, otherwise execute step S091.

[0128] S091, the processing module determines whether there is a heating instruction, if so, executes step S10, otherwise returns to step S081; wherein, the heating instruction is input by the operator, for example, the operator presses a heating button on the host computer of the electric heating temperature control system.

[0129] S10. The processing module controls the operation of the heating circuit: the control processing module outputs a high-level first signal to the input power control module of the heating subsystem, and inputs a pulse waveform second signal to the program heating control module of the heating subsystem, so that the positive and negative poles of the heating element and the heating power supply of the heating subsystem are turned on.

[0130] S11. The processing module determines whether the temperature is abnormal. If so, step S40 is executed, otherwise step S20 is executed. Among them, detecting that the thermistor is broken and detecting that the electric heating element has been heated to the target temperature or even exceeds the target temperature are both abnormal temperature situations.

[0131] S20, the processing module determines whether the temperature of the electric heating element reaches the target temperature. If so, execute step S30, otherwise return to step S10; wherein, the target temperature can be a fixed value pre-written into the processing module, or can be input into the system by the operator.

[0132] S30, PID performs PID control on the temperature of the electric heating element, and executes step S40 when a stop instruction is detected; wherein the stop instruction is an instruction input by the operator.

[0133] S40, controlling the heating circuit to be disconnected. This step can be achieved by turning off the power of the processing module, or by controlling the first signal and the second signal by the processing module.

[0134] An electric heating temperature control method is implemented using the above-mentioned electric heating temperature control system (an embodiment in which the second signal is a pulse waveform), and the control method includes the following steps:

[0135] a. Start the processing module, which obtains the current temperature and target temperature of the electric heating element and calculates the time T required for the electric heating element to reach the target temperature from the current temperature. The current temperature can be obtained by starting the detection module, and the target temperature can be data pre-written into the processing module or data entered by the operator read by the processing module.

[0136] b. The processing module controls the operation of the heating circuit and records the operation time t of the heating circuit;

[0137] c. When the processing module determines that t≥T, execute step d; otherwise, return to step b;

[0138] d. The processing module determines whether the temperature of the electric heating element reaches the target temperature. If so, execute step e; otherwise, return to step b;

[0139] e. The processing module determines whether the temperature of the electric heating element exceeds a first target temperature threshold. If so, step g is executed; otherwise, step f is executed. The first threshold may be 5° C.;

[0140] f. Perform PID control on the temperature of the electric heating element, and execute step g when a stop command is detected; in PID control, the thermoelectric signal is used as feedback (the thermoelectric signal reflects the actual temperature of the electric heating element, and using the thermoelectric signal as feedback is equivalent to using the actual temperature of the electric heating element as feedback), and the PID control unit adjusts the duty cycle of the second signal according to the feedback of the thermoelectric signal to achieve this.

[0141] g. Control the heating circuit to disconnect or perform abnormal processing on the electric heating temperature control system. This step can be achieved by turning off the power supply of the processing module, or by controlling the first signal and the second signal through the processing module.

[0142] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. An electric heating temperature control system, characterized in that: It includes a heating device with an electric heating element, a heating power supply, a heating subsystem, a temperature detection module and a processing module; The heating subsystem is used to form a heating circuit with the electric heating element and the heating power supply; The heating subsystem includes an input power control module, a program heating control module and a program heating control protection module; The input power control module is used to control the connection and disconnection between the positive electrode of the heating power supply and the electric heating element according to the first signal transmitted by the processing module; The program heating control module is used to control the connection and disconnection between the negative electrode of the heating power supply and the electric heating element according to the second signal transmitted by the processing module, and the second signal is a pulse signal; The program heating control protection module includes an input side protection unit and an output side protection unit, wherein the input side protection unit is used to disconnect the path between the input power control module and the electric heating element when the second signal changes from a pulse signal to a low level signal, and the output side protection unit is used to control the program heating control module to disconnect the path between the negative electrode of the heating power supply and the electric heating element when the second signal changes from a pulse signal to a normally high level signal or a normally low level signal; The temperature detection module is used to convert the temperature of the electric heating element into a thermoelectric signal; The processing module is used to input the first signal and the second signal into the heating subsystem to control the on and off of the heating circuit, and is also used to perform PID control on the temperature of the electric heating element according to the thermoelectric signal. In the PID control, the thermoelectric signal is used as feedback to adjust the first signal and / or the second signal.

2. The electric heating temperature control system according to claim 1, characterized in that: The input power control module includes: a first MOS transistor, wherein the source electrode of the first MOS transistor is connected to the positive electrode of the heating power supply, and the drain electrode of the first MOS transistor is connected to the electric heating element; A first photoelectric coupler, used to control the first MOS tube to be turned on and off; The first transistor is configured to drive the first photocoupler to be turned on and off according to the first signal.

3. The electric heating temperature control system according to claim 2, characterized in that: The program heating control module includes: a second MOS transistor, wherein the source of the second MOS transistor is connected to the negative electrode of the heating power supply, and the drain of the second MOS transistor is connected to the electric heating element; A second photoelectric coupler, used to control the second MOS tube to be turned on and off; The second transistor is used to drive the second photocoupler to be turned on and off according to the second signal.

4. The electric heating temperature control system according to claim 3, characterized in that: The input side protection unit includes: a third MOS transistor, wherein the source of the third MOS transistor is connected to the drain of the first MOS transistor; A third triode, used to drive the third MOS tube; a first charge-discharge unit, configured to charge when a high level is input to the program heating control module, and discharge the base of the third transistor when a low level is input to the program heating control module; In one cycle of the second signal, the charging amount of the input side protection unit in the high level stage can maintain the positive electrode of the input power control module and the electric heating element in the low level stage in the conductive state.

5. The electric heating temperature control system according to claim 3, characterized in that: The output side protection unit includes: a second charge and discharge unit connected to the emitter of the second photoelectric coupler; when the program heating control module inputs a high level, the second charge and discharge unit charges slowly, and when the program heating control module inputs a low level, the second charge and discharge unit discharges quickly; A first voltage comparator includes a first channel, an inverting input of the first channel connected to the second charge-discharge unit, and a non-inverting input of the first channel being a first fixed voltage, wherein when the second control signal is a pulse signal, the first fixed voltage is greater than the voltage of the second charge-discharge unit, and after the second signal becomes high for a period of time, the first fixed voltage is less than the voltage of the second charge-discharge unit; the first voltage comparator also includes a second channel, an inverting input of the second channel connected to the output of the temperature detection protection module, a non-inverting input of the second channel connected to the second fixed voltage, and the second channel and the first channel using wired-AND logic; a fourth triode, wherein: a base of the fourth triode is connected to the output of the first channel, an emitter is connected to the gate of the second MOS transistor, and a collector is grounded; wherein, when the first fixed voltage is less than the voltage of the second charge and discharge unit, the emitter and collector of the fourth triode are turned on, and the second MOS transistor is turned off.

6. The electric heating temperature control system according to claim 1, characterized in that: The temperature detection module includes: a thermistor, mounted on the electric heating element; The operational amplifier unit is used to form a constant current source monitoring circuit with the thermistor and amplify the voltage at the current output end of the thermistor to form the thermoelectric signal.

7. The electric heating temperature control system according to any one of claims 1 to 6, characterized in that: The processing module includes: a first control unit, configured to output the first signal; a second control unit, configured to output the second signal; The PID control unit is electrically connected to the temperature detection module, the first control unit and the second control unit respectively; when the electric heating element reaches the target temperature, the PID control unit performs PID control on the heating circuit according to the thermoelectric signal.

8. An electric heating temperature control method, characterized in that: The electric heating temperature control system according to any one of claims 1 to 6 is used for implementation, and the control method comprises the following steps: S10, controlling the operation of the heating circuit; S20, determining whether the temperature of the electric heating element reaches the target temperature, if so, executing step S30, otherwise returning to step S10; S30, performing PID control on the temperature of the electric heating element, and executing step S40 when a stop instruction is detected; S40: Control the heating circuit to be disconnected.

9. The electric heating temperature control method according to claim 8, characterized in that: Step S10 specifically includes the following steps: The processing module is controlled to output a high-level first signal to the input power control module of the heating subsystem, and to input a pulse waveform second signal to the program heating control module of the heating subsystem, so that the positive and negative poles of the heating element and the heating power supply of the heating subsystem are turned on.

10. The electric heating temperature control method according to claim 9, characterized in that: The following steps are also included between step S10 and step S20: S11. Determine whether the temperature is abnormal. If so, execute step S40; otherwise, execute step S20.

11. The electric heating temperature control method according to claim 9, characterized in that: Before step S10, the following steps are also included: S071, control processing module operation; S081, the processing module starts the temperature detection module and determines whether the temperature of the electric heating element is abnormal. If so, execute step S40; otherwise, execute step S091; S091. Determine whether there is a heating instruction. If so, execute step S10; otherwise, return to step S081.

12. An electric heating temperature control method, characterized in that: The electric heating temperature control system according to any one of claims 1 to 6 is used for implementation, and the control method comprises the following steps: a. Obtaining the current temperature and target temperature of the electric heating element, and calculating the time T required for the electric heating element to reach the target temperature from the current temperature; b. controlling the operation of the heating circuit and recording the operation time t of the heating circuit; c. When t ≥ T, execute step d, otherwise return to step b; d. Determine whether the temperature of the electric heating element reaches the target temperature. If so, execute step e; otherwise, return to step b; e. Determine whether the temperature of the electric heating element exceeds a first target temperature threshold; if so, proceed to step g; otherwise, proceed to step f; f. Performing PID control on the temperature of the electric heating element, and executing step g when a stop instruction is detected; g. Control the heating circuit to disconnect.

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