Dry-out control circuit

Abstract

The application provides a dry burning prevention control circuit, which comprises a resistance variable module and a first current source; the first current source is connected with the resistance variable module and a controlled heat generating module; the heat generating module is used for realizing a heating function; the resistance variable module is used for detecting resistance value change of the heat generating module during heating of the heat generating module; when the resistance value of the heat generating module after heating is greater than a set threshold, dry burning prevention protection is performed; and when the resistance value of the heat generating module after heating is less than or equal to the set threshold, the heat generating module is allowed to be heated. The embodiment of the application can realize dry burning prevention control.

Description

Technical Field

[0001] This application relates to the field of electronic technology, specifically to an anti-dry-burning control circuit. Background Technology

[0002] Electronic devices rely on heating modules for heat generation, which can easily lead to dry burning of these modules. Dry burning damages the heating modules, reducing the lifespan of the electronic device and posing safety hazards to users. Therefore, how to prevent dry burning is an urgent issue that needs to be addressed. Summary of the Invention

[0003] This application provides an anti-dry-burning control circuit that can achieve anti-dry-burning control.

[0004] In a first aspect, embodiments of this application provide an anti-dry-burning control circuit, the anti-dry-burning control circuit comprising: a variable resistance module and a first current source; the first current source is connected to the variable resistance module and a controlled heating module;

[0005] The heating module is used to realize the heating function;

[0006] The variable resistance module is used to detect the change in resistance of the heating module during the heating process. When the resistance of the heating module after heating is greater than a set threshold, it performs anti-dry burning protection. When the resistance of the heating module after heating is less than or equal to the set threshold, it allows the heating module to be heated.

[0007] Secondly, embodiments of this application provide an electronic device that includes an anti-dry-burning control circuit as described in the first aspect.

[0008] Implementing the embodiments of this application has the following beneficial effects:

[0009] As can be seen, the anti-dry-burning control circuit and electronic device described in the embodiments of this application include: a variable resistance module and a first current source. The first current source is connected to the variable resistance module and the controlled heating module. The heating module performs the heating function. During the heating process of the heating module, the variable resistance module detects the change in the resistance of the heating module. When the resistance of the heating module after heating is greater than a set threshold, anti-dry-burning protection is performed. When the resistance of the heating module after heating is less than or equal to the set threshold, heating of the heating module is allowed. Thus, the variable resistance module can be used to detect the change in the resistance of the heating module to achieve anti-dry-burning protection of the heating module, which can improve user experience and safety. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of this application 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 this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a schematic diagram of the structure of an anti-dry-burning control circuit provided in an embodiment of this application;

[0012] Figure 2 This is a schematic diagram of the structure of an anti-dry-burning control circuit provided in an embodiment of this application;

[0013] Figure 3 This is a schematic diagram of another anti-dry-burning control circuit provided in an embodiment of this application;

[0014] Figure 4 This is a flowchart illustrating a control method for an anti-dry-burning control circuit provided in an embodiment of this application;

[0015] Figure 5 This is a schematic diagram of another anti-dry-burning control circuit provided in an embodiment of this application;

[0016] Figure 6 This is a flowchart illustrating another control method for an anti-dry-burning control circuit provided in an embodiment of this application;

[0017] Figure 7 This is a schematic diagram of another anti-dry-burning control circuit provided in the embodiments of this application. Detailed Implementation

[0018] To help those skilled in the art better understand the technical solutions of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the description of the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, software, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but also includes steps or units not listed, or other steps or units inherent to such processes, methods, products, or apparatus.

[0020] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0021] The embodiments of this application are described below with reference to the accompanying drawings. In the drawings, the intersection of intersecting wires is indicated by dots, and the absence of dots indicates that the wires are not connected.

[0022] To better understand the solutions of the embodiments of this application, the relevant terms and concepts that may be involved in the embodiments of this application will be introduced below.

[0023] In this embodiment, the heating module may include a heating wire, which may include a resistance wire or a heating wire. The electronic device may include a device that needs to control the heating function, and the electronic device may include a heating module and a variable resistance module. The electronic device may include at least one of the following: electric blanket, heater, electronic cigarette, rice cooker, kettle, etc., which are not limited here.

[0024] Please see Figure 1 , Figure 1 This application provides an embodiment of an anti-dry-burning control circuit, which includes: a variable resistance module and a first current source IOUT1; the first current source is connected to the variable resistance module and the controlled heating module.

[0025] The heating module is used to realize the heating function;

[0026] The variable resistance module is used to detect the change in resistance of the heating module during the heating process. When the resistance of the heating module after heating is greater than a set threshold, it performs anti-dry burning protection. When the resistance of the heating module after heating is less than or equal to the set threshold, it allows the heating module to be heated.

[0027] The threshold can be set in advance or by system default.

[0028] For further details, please refer to Figure 2 , Figure 2This application provides an anti-dry-burning control circuit. The heating module includes a first MOSFET, a heating wire RL, and a power supply BAT. The anti-dry-burning control circuit includes a variable resistance module and a first current source IOUT1. The first current source IOUT1 is connected to the variable resistance module, one end of the heating wire RL, and the source of the first MOSFET Q1. The other end of the heating wire is grounded. The drain of the first MOSFET Q1 is connected to the power supply BAT.

[0029] The heating wire is used to achieve the heating function;

[0030] The variable resistance module is used to detect the resistance change of the heating wire during the heating process, obtain the amount of resistance change, perform anti-dry burning protection when the amount of resistance change is greater than a set threshold, and allow heating of the heating wire when the amount of resistance change is less than the set threshold.

[0031] The threshold can be set in advance or by system default.

[0032] Among them, the first MOSFET Q1 can also be called the output power MOSFET.

[0033] As can be seen, in the anti-dry-burning control circuit described in this application embodiment, the heating wire performs the heating function, and the variable resistance module detects the change in the resistance of the heating wire during the heating process. When the resistance of the heated wire after heating is greater than a set threshold, anti-dry-burning protection is performed, and when the resistance of the heated wire after heating is less than or equal to the set threshold, heating of the heating wire is allowed. Thus, the variable resistance module can be used to detect the change in the resistance of the heating wire to achieve anti-dry-burning protection, which can improve user experience and safety.

[0034] Please see Figure 3 , Figure 3 This application provides an embodiment of an anti-dry-burning control circuit, which includes: a first current source IOUT1, a second current source IOUT2, a first MOSFET Q1, a comparator CMP, and a heating wire RL. The positive input terminal (+) of the comparator CMP is connected to the first current source IOUT1, the source of the first MOSFET Q1, and the heating wire RL. The negative input terminal (-) of the comparator CMP is connected to the second current source IOUT2 ​​through a single-pole double-throw switch.

[0035] The second current source is grounded through a resistor;

[0036] The drain of the first MOSFET Q1 is connected to the power supply BAT.

[0037] In a specific implementation, the second current source is grounded through one or more resistors. For example, the second current source is grounded through one resistor, or for another example, the second current source is grounded through two resistors.

[0038] In this embodiment, a feasible anti-dry-burning circuit can be formed by using one comparator, one MOSFET, two current sources, and one or two resistors. Compared with other solutions that require an MCU and a precise current meter, the cost is greatly reduced.

[0039] Optionally, the first current source is used to lock the resistance value of the heating module by adjusting the current magnitude of the first current source before heating the heating module;

[0040] The variable resistance module is used to achieve electrical balance by making the input data of the positive input terminal and the negative input terminal of the comparator equal through a first switch on / off method; and to change the voltage value of the negative input terminal of the comparator through a second switch on / off method, thereby turning off the first current source, turning on the first MOS transistor to heat the heating wire, and detecting whether the voltage value of the heating wire is greater than the voltage value of the negative input terminal of the comparator. If so, it is confirmed that there is a dry burning phenomenon and performs anti-dry burning protection.

[0041] The first switch switching method and the second switch switching method are different switch switching methods.

[0042] Optionally, when the negative input terminal (-) of the comparator CMP is connected to the second current source IOUT2 ​​through the single-pole double-throw switch, the second current source IOUT2 ​​is connected in series with the second resistor R2 and the first resistor R1, and the first resistor R1 is also grounded;

[0043] The stationary terminal of the single-pole double-throw switch is connected to the comparator CMP, and the first switching terminal T1 and the second switching terminal T2 of the single-pole double-throw switch are respectively connected to the two ends of the second resistor R2.

[0044] Optionally, before the heating wire RL starts heating, the resistance value of the heating wire RL is locked by adjusting the current of the first current source IOUT1, specifically:

[0045] The first current source IOUT1 first outputs the maximum current. The negative input terminal (-) of the comparator CMP is connected to the second resistor R2 and the first resistor R1 through the first switching terminal T1 of the single-pole double-throw switch. If the output of the comparator CMP is 0, protection is performed and no output is output.

[0046] In practice, when the heating wire is heated to an abnormally high temperature, the characteristic that the resistance of the heating wire changes with temperature can be used to judge the temperature change by the change in resistance, thereby determining whether the heating wire is dry-burning.

[0047] In practical applications, before heating begins, that is, before the output power MOSFET turns on, the resistance of the heating wire RL can be locked by adjusting the current of IOUT1: IOUT1 first outputs the maximum current, at which point the "-" input of the comparator is connected to T1. If the comparator output is 0, that is:

[0048] VRL1 <VTH1

[0049] This indicates that the resistance of the RL heating wire is less than the set minimum resistance, and the system enters protection mode and stops outputting.

[0050] Optionally, if the output of the comparator CMP is 1, the output current source of the first current source IOUT1 is gradually reduced until the output of the comparator CMP changes from 1 to 0; the heating wire RL is turned on to heat, and heating is stopped every first preset time interval; the second current source IOUT2 ​​and the second resistor R2 are connected through the second switching terminal T2 of the single-pole double-throw switch.

[0051] The first preset time interval can be set in advance or be the system default.

[0052] In the specific implementation, if the comparator output is 1, the output current source IOUT1 is gradually reduced until the comparator output changes from 1 to 0. Then, heating is turned on, and heating is stopped every time interval t. Then, the current source value recorded above is turned on. At this time, the "-" input terminal of the comparator is connected to T2, and the output of the comparator is observed. If the output of the comparator CMP changes from 0 to 1, that is:

[0053] VTH2 <VRL2

[0054] Where VTH2 = (1 + n) * VTH1, we can deduce that RL2 > (1 + n) * RL1. This means that if the resistance change of RL exceeds n%, the dry-burn protection will be activated. The resistance range of the heating wire can be set by the resistance values ​​of R1 and R2. R2 / R1 = n, where n is the maximum range that the heating wire can change. n can be preset or set by the system default.

[0055] In this embodiment, a feasible anti-dry-burning circuit is formed by using one comparator, one MOSFET, two current sources, and two resistors. Compared with other solutions that require an MCU and a precise current meter, the cost is greatly reduced.

[0056] For example, Figure 4As shown, in practical applications, the IOUT1 current source turns on to output 150 mA. The comparator is connected to T1. The comparator checks: Is VTH1 < VRL1? If not, the resistance of the heating wire is too small, the output is turned off, and protection is entered. If so, the current of the IOUT1 current source is decreased by step = 1 mA. Then, the comparator checks again: Is VTH1 < VRL1? If so, continue to execute the step of the comparator: Is VTH1 < VRL1? If not, lock the output current value of the IOUT1 current source as IOUT1_T0, turn on the output power MOS Q1, and start heating the heating wire. The comparator is connected to T2. Every time interval t, the output is turned off, and the output current value of the IOUT1 current source recorded above, i.e., IOUT1_T0, is turned on. The comparator checks: Is VTH2 < VRL2? If so, it is determined as dry burning, the output is turned off, and protection is entered. If not, execute the step of turning on the output and starting to heat the heating wire. The comparator is connected to T2.

[0057] Optionally, as Figure 5 shown, when the negative input terminal (-) of the comparator CMP is connected to the second current source IOUT2, the negative input terminal (-) of the comparator CMP is connected to the source of the second MOS transistor Q2. The drain of the second MOS transistor Q2 is connected to the second current source IOU2. The gate of the second MOS transistor Q2 is connected to one end of the first capacitor C1 and, through the first switch SW1, to the output terminal of the comparator CMP; the other end of the first capacitor C1 is grounded;

[0058] The negative input terminal (-) of the comparator CMP is also grounded successively through the third resistor R3 and the fourth resistor R4; one end of the second switch SW2 is grounded and the other end is connected to the third resistor R3 and the fourth resistor R4.

[0059] In specific implementation, the second current source may include a voltage-controlled current source.

[0060] Further, optionally, before the heating wire RL starts to heat, the first current source IOUT1 outputs a fixed current;

[0061] The first switch SW1 and the second switch SW2 are closed. The output of the comparator CMP is connected to the gate of the second MOS transistor IOUT2 to form negative feedback. When the comparator CMP outputs high, the first capacitor C1 starts to be charged, and the voltage of the first capacitor C1 increases;

[0062] When the comparator CMP outputs low, the voltage of the first capacitor C1 decreases, the current of the second current source decreases, and after a period of feedback adjustment, the voltage of the first capacitor C1 stabilizes at a specified value.

[0063] In a specific implementation, when the temperature of the heating wire is heated to an abnormally high temperature, the characteristic that the resistance of the heating wire changes with temperature can be used to judge the temperature change by the change in resistance, thereby determining whether the heating wire is dry-burning. Before heating, IOUT1 can be turned on (IOUT1 does not require precise current, approximately 100mA is sufficient) to output a fixed current. At this time, VRL = IOUT1 * RL. Then, SW1 and SW2 can be closed first, and the output of comparator CMP can be connected to the gate of Q2 (Q2 is a voltage-controlled current source, which can control the output current IOUT2 ​​= K * VC1 through the voltage of VC1), forming negative feedback: C1 is initially 0, IOUT2 ​​= 0, VTH = IOUT2 ​​* R3 = 0, VRL > VTH, CMP outputs a high level, and starts charging capacitor C1, increasing the voltage of VC1; when VTH = IOUT2 ​​* R3 = K * VC1 * R3 > VRL = IOUT1 * RL, CMP outputs a low level, the voltage of VC1 decreases, and the current of IOUT2 ​​decreases; finally, after a period of feedback adjustment, the voltage of VC1 will stabilize at: VTH = IOUT2 ​​* R3 = K * VC1 * R3 = VRL = IOUT1 * RL.

[0064] Furthermore, optionally, after the voltage of the first capacitor stabilizes, the first switch and the second switch are disconnected, and the comparator outputs 0.

[0065] Optionally, the first current source IOUT1 is turned off, and the first MOS transistor Q1 is turned on to heat the heating wire RL;

[0066] Heating is stopped every second preset time interval, and the first current source IOUT1 is turned on again. The resistance of the heating wire RL increases. If the resistance increases to a preset value, the output of the comparator CMP changes from 0 to 1 to perform anti-dry burning protection and stop heating the heating wire RL.

[0067] The preset resistance value can be set in advance or set by the system default.

[0068] In the specific implementation, after the VC1 voltage stabilizes, SW1 and SW2 are disconnected, and CMP becomes a comparator. Since the VC1 voltage will remain essentially constant (VC1's leakage current is very small), IOUT2 ​​= K * VC1 remains unchanged, VTH = IOUT2 ​​* (R3 + R4) = K * VC1 * (R3 + R4) > IOUT1 * RL = K * VC1 * R3, and CMP outputs 0; then IOUT1 is turned off, the output power MOSFET is turned on, and the heating wire RL is heated every... When T is turned on, heating stops and IOUT1 is turned back on, causing the resistance of RL to increase. RL, then VRL = IOUT1*(RL+ RL), if the increase in resistance value is too large, resulting in VRL = IOUT1 * (RL + RL) > VTH = IOUT2 * (R3 + R4) = K * VC1 * (R3 + R4), then the CMP output will change from 0 to 1. When seeing the CMP change from 0 to 1, it is considered that the change in the resistance value of RL is too large, the temperature of the heating wire rises too high, and there is a dry burning situation. It is necessary to enter the dry-burning protection, stop heating and give a prompt, so as to improve the user experience.

[0069] In the embodiment of the present application, the circuit currently detects the change in the resistance value of RL by adjusting the size of R4 of RL.

[0070] In the embodiment of the present application, Figure 5 the described dry-burning prevention control circuit adopts 1 operational amplifier (switching between negative feedback and comparator), 2 current sources that do not need to be very accurate, and 2 resistors. By adding a negative feedback circuit to automatically adjust the output size of the current source, a feasible dry-burning prevention circuit is formed, which greatly reduces the cost compared with other solutions that require an MCU and a precise ammeter.

[0071] For example, as Figure 6 shown, in practical applications, IOUT1 outputs a fixed current. Close SW1 and SW2 to form negative feedback to adjust the output current of IOUT2. Disconnect the first switch SW1, the second switch SW2, turn on the first MOS transistor Q1 to heat the heating wire. Every t time, turn off the first MOS transistor Q1, turn on the second current source IOUT2, and the comparator: whether VTH < VRL. If so, it is judged as dry burning and protection is carried out. If not, execute the steps of disconnecting the first switch SW1, the second switch SW2, turning on the first MOS transistor Q1, and heating the heating wire.

[0072] Optionally, as Figure 7 shown, when connecting the second current source IOUT2 to the negative input terminal (-) of the comparator CMP, the negative input terminal (-) of the comparator CMP is connected to the source electrode of the second MOS transistor Q2, the drain electrode of the second MOS transistor Q2 is connected to the second current source IOUT2, and the gate electrode of the second MOS transistor Q2 is connected to one end of the first capacitor C1 and through the first switch SW1 to the output terminal of the comparator CMP; the other end of the first capacitor C1 is grounded;

[0073] The negative input terminal (-) of the comparator CMP is grounded through the fifth resistor R5;

[0074] The negative input terminal (-) of the comparator CMP is also connected to a third current source via a third switch SW3. I.

[0075] In this embodiment of the application, it is equivalent to... Figure 5 Based on this, change R4 to another path. The current source of I. By adjusting I will adjust Changes in RL detection values.

[0076] In the specific implementation, Figure 5 The proposed solution controls the VTH voltage through the second switch SW2: Before heating, the second switch SW2 is closed, VTH = IOUT2 ​​* R1; after the VCl voltage rises and balances through negative feedback, the first switch SW1 and the second switch SW2 are then opened, thereby changing the VTH voltage: VTH =IOUT2*(R1+R2)=IOUT2*R1+IOUT2*R2; and Figure 7 The proposed solution is to replace it by adjusting and increasing ΔI. Figure 5 In the design, the second resistor R2 is used as follows: Before heating, the second switch SW2 is opened, and VTH = IOUT2 ​​* R1; after the voltage VC1 rises and balances through negative feedback, the first switch SW1 is opened and the second switch SW2 is closed, adding a current to the first resistor R1. I, thus changing the VTH voltage: VTH =IOUT2*R1+△I*R1. As can be seen, Figure 7 The scheme in I*R1 is equivalent to Figure 5 The purpose of IOUT2*R2 in the middle scheme is to increase VTH. The voltage is used to set the resistance value of RL to increase after heating, triggering the judgment of the resistance change when dry burning.

[0077] The anti-dry-burning control circuit described in this application embodiment has the following advantages:

[0078] 1. Figure 5 , Figure 7 The proposed solution does not require an MCU, ADC, or DAC; it is implemented using purely analog circuitry, significantly reducing costs. Figure 2 The proposed solution requires adjusting the current value of IOUT1, which necessitates digital circuitry to record the IOUT1_T0 value before heating and a DAC to adjust the output current value of IOUT1.

[0079] 2. No precise current source is required. The currents of IOUT1 and IOUT2 ​​do not need calibration, and the resistance values ​​of R3, R4, R5, and RL are irrelevant. The negative feedback circuit will automatically adjust the IOUT2 ​​current to match the deviation of IOUT1 and the deviation of the initial RL resistance. Specifically, R4 and... I decide The dry-burning judgment threshold of RL;

[0080] 3. It can automatically match different RL resistors, improving the compatibility of heating wires with different resistance values.

[0081] The anti-dry-burning control circuit described in the embodiments of this application can be composed of one comparator, one MOSFET, two current sources, and one or two resistors to form a feasible anti-dry-burning circuit, which greatly reduces costs compared to other solutions that require MCU and precise current meter.

[0082] In this embodiment of the application, an electronic device may also be provided, which includes the above-mentioned anti-dry-burning control circuit, and anti-dry-burning control is achieved through the anti-dry-burning control circuit.

[0083] The above are the implementation methods of the embodiments of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the embodiments of this application, and these improvements and modifications are also considered to be within the protection scope of this application.

Claims

1. A dry-burning prevention control circuit, characterized in that, The anti-dry-burning control circuit includes: a variable resistance module and a first current source; the first current source is connected to the variable resistance module and the controlled heating module; The heating module is used to realize the heating function; The variable resistance module is used to detect the change in resistance of the heating module during the heating process. When the resistance of the heating module after heating is greater than a set threshold, it performs anti-dry burning protection. When the resistance of the heating module after heating is less than or equal to the set threshold, it allows the heating module to be heated. The variable resistance module includes a comparator and a second current source; the heating module includes a first MOSFET, a heating wire, and a power supply; the variable resistance module is connected to the source of the first MOSFET and one end of the heating wire, and the other end of the heating wire is grounded. The positive input terminal of the comparator is connected to the first current source, the source of the first MOSFET, and the heating wire; the negative input terminal of the comparator is directly or indirectly connected to the second current source. The second current source is grounded through a resistor; The drain of the first MOSFET is connected to the power supply.

2. The anti-dry-burning control circuit according to claim 1, characterized in that, The first current source is used to lock the resistance value of the heating module by adjusting the current magnitude of the first current source before heating the heating module; The variable resistance module is used to achieve electrical balance by adjusting the current in a first way to make the input data of the positive input terminal and the negative input terminal of the comparator equal. And by adjusting the current in a second way, the voltage value of the negative input terminal of the comparator is changed, the first current source is turned off, the first MOS transistor is turned on to heat the heating wire, and the voltage value of the heating wire is detected to be greater than the voltage value of the negative input terminal of the comparator. If so, it is confirmed that there is a dry burning phenomenon, and dry burning protection is performed.

3. The anti-dry-burning control circuit according to claim 1 or 2, characterized in that, When the negative input terminal of the comparator is connected to the second current source through a single-pole double-throw switch, the stationary terminal of the single-pole double-throw switch is connected to the comparator, and the first switching terminal and the second switching terminal of the single-pole double-throw switch are respectively connected to the two ends of the second resistor. The first current source outputs the maximum current first. The negative input terminal of the comparator is connected to the second resistor and the first resistor through the first switching terminal of the single-pole double-throw switch. If the output of the comparator is 0, protection is performed and no output is output.

4. The anti-dry-burning control circuit according to claim 3, characterized in that, If the output of the comparator is 1, gradually reduce the output current of the first current source until the output of the comparator changes from 1 to 0; turn on the heating wire to heat, stop heating every first preset time interval, and connect the second current source and the second resistor through the second switching terminal of the single-pole double-throw switch.

5. The anti-dry-burning control circuit according to claim 1 or 2, characterized in that, When the negative input terminal of the comparator is connected to the second current source, the negative input terminal of the comparator is connected to the source of the second MOS transistor, the drain of the second MOS transistor is connected to the second current source, the gate of the second MOS transistor is connected to one end of the first capacitor and the output terminal of the comparator through the first switch; the other end of the first capacitor is grounded. The negative input terminal of the comparator is also grounded through a third resistor and a fourth resistor in sequence; one end of the second switch is grounded and the other end is connected to the third resistor and the fourth resistor.

6. The anti-dry-burning control circuit according to claim 5, characterized in that, Before the heating wire begins to heat up, the first current source outputs a fixed current; When the first switch and the second switch are closed, the output of the comparator is connected to the gate of the second MOS transistor to form negative feedback; when the comparator outputs a high level, the first capacitor begins to charge, and the voltage of the first capacitor increases.

7. The anti-dry-burning control circuit according to claim 6, characterized in that, When the comparator outputs a low level, the voltage of the first capacitor decreases, the current of the second current source decreases, and after a period of feedback adjustment, the voltage of the first capacitor stabilizes at a specified value. After the voltage of the first capacitor stabilizes, the first switch and the second switch are disconnected, and the comparator outputs 0.

8. The anti-dry-burning control circuit according to claim 6, characterized in that, Turn off the first current source, turn on the first MOS transistor, and heat the heating wire; Heating is stopped every second preset time interval, and the first current source is turned on again. The resistance of the heating wire increases. If the resistance increases to a preset value, the output of the comparator changes from 0 to 1 to perform anti-dry burning protection and stop heating the heating wire.

9. The anti-dry-burning control circuit according to claim 1 or 2, characterized in that, When the negative input terminal of the comparator is connected to the second current source, the negative input terminal of the comparator is connected to the source of the second MOS transistor, the drain of the second MOS transistor is connected to the second current source, the gate of the second MOS transistor is connected to one end of the first capacitor and the output terminal of the comparator through the first switch; the other end of the first capacitor is grounded. The negative input terminal of the comparator is grounded through a fifth resistor; The negative input terminal of the comparator is also connected to a third current source via a third switch.

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