High-temperature warning circuit and high-temperature warning method

Abstract

The invention provides a high-temperature warning circuit and a high-temperature warning method. The high temperature warning circuit comprises a microprocessor, a diode, a first capacitor, a switch unit, a first operational amplifier, a second operational amplifier, a first comparator, a first light emitting diode, a second light emitting diode, a thermistor, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, an eleventh resistor and a voltage adjusting unit. Wherein in the power-on state, the microprocessor realizes high-precision temperature acquisition and high-temperature warning through the technical schemes of analog-digital conversion, Gaussian weighted moving average filtering, improved moving least square fitting and the like, and when the input power supply is switched from the power-on state to the power-off state, the microprocessor is powered off and does not work. And the first capacitor is used as a temporary power supply, and high-temperature warning is completed by virtue of a hardware circuit, so that the technical scheme that the high-temperature warning task can be continuously completed within a period of time when the equipment is powered on and powered off is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of welding equipment, and in particular to a high temperature warning circuit and a high temperature warning method. Background Art

[0002] Electric soldering irons and heat guns are essential welding tools for electronic engineers. These welding tools have very high temperatures during operation, and generally do not display the current temperature or have a high temperature warning function. At present, although some products can already display the current temperature of the working part of the welding tool during operation, after a power outage, existing products cannot display the temperature or have a high temperature warning function. Since the device is shut down or the power is off, the user cannot know whether the current device temperature is too high, and the user may be burned if he touches the device.

[0003] Therefore, it is necessary to provide a technical solution that can accurately detect the temperature of the welding equipment when it is powered on, and can still provide a high temperature warning for a period of time after the welding equipment is shut down or powered off, so as to prevent users from being scalded. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a high temperature warning circuit and a high temperature warning method.

[0005] A high temperature warning circuit provided by the present invention includes: a microprocessor, a diode, a first capacitor, a switch unit, a first operational amplifier, a second operational amplifier, a first comparator, a first light emitting diode, a second light emitting diode, a thermistor, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, an eleventh resistor, and a voltage adjustment unit;

[0006] The positive power input terminal of the microprocessor is electrically connected to the anode of the diode and is used to connect the positive input power terminal, the negative power input terminal and the first end of the first capacitor are electrically connected to the ground, and the first output terminal is electrically connected to the control terminal of the switch unit and the first end of the first resistor respectively;

[0007] The cathode of the diode is electrically connected to the second end of the first capacitor, the input end of the switch unit, and the first end of the second resistor respectively;

[0008] The output end of the switch unit is electrically connected to the positive power supply electrode of the first operational amplifier, the positive power supply electrode of the first comparator, and the first end of the third resistor respectively;

[0009] The non-inverting input terminal of the first operational amplifier is electrically connected to the first terminal of the thermistor and the second terminal of the second resistor respectively, the inverting input terminal thereof is electrically connected to its output terminal and the non-inverting input terminal of the first comparator respectively, and the negative power supply terminal thereof, the negative power supply terminal of the first comparator, the second terminal of the thermistor, the second terminal of the first resistor, and the first terminal of the fourth resistor are electrically connected to the ground;

[0010] The inverting input terminal of the first comparator is electrically connected to the second end of the third resistor and the second end of the fourth resistor respectively, and the output terminal thereof is electrically connected to the anode of the first light emitting diode;

[0011] The cathode of the first light emitting diode is electrically connected to the first end of the fifth resistor;

[0012] The second end of the fifth resistor is electrically connected to the output end of the voltage adjustment unit;

[0013] The non-inverting input terminal of the second operational amplifier is electrically connected to the first terminal of the thermistor, the inverting input terminal thereof is electrically connected to the output terminal thereof and the analog input terminal of the microprocessor respectively, the positive electrode of the power supply is electrically connected to the positive electrode of the diode, and the negative electrode of the power supply and the negative electrode of the second light-emitting diode are electrically connected to the ground;

[0014] The anode of the second light emitting diode is electrically connected to the first end of the eleventh resistor;

[0015] The second end of the eleventh resistor is electrically connected to the second output end of the microprocessor.

[0016] In a possible implementation, the switch unit includes a PMOS tube and a sixth resistor;

[0017] The gate of the PMOS tube is electrically connected to the first end of the sixth resistor as the control end of the switch unit, the source thereof is electrically connected to the second end of the sixth resistor as the input end of the switch unit, and the drain thereof serves as the output end of the switch unit.

[0018] In a possible implementation, the voltage adjustment unit is used to reduce power consumption;

[0019] The voltage adjustment unit includes a second capacitor, a second comparator, a seventh resistor, an eighth resistor, a ninth resistor, and a tenth resistor;

[0020] The first end of the second capacitor is electrically connected to the inverting input end of the second comparator and the first end of the tenth resistor respectively, and the second end thereof is electrically connected to the ground;

[0021] The non-inverting input terminal of the second comparator is electrically connected to the first end of the seventh resistor, the first end of the eighth resistor, and the first end of the ninth resistor, respectively; the positive electrode of the power supply and the second end of the ninth resistor are electrically connected to the output terminal of the switch unit, respectively; the negative electrode of the power supply is electrically connected to the ground; and the output terminal is electrically connected to the second end of the fifth resistor, the second end of the eighth resistor, and the second end of the tenth resistor, respectively;

[0022] The second end of the seventh resistor is electrically connected to the ground.

[0023] In a possible implementation, the thermistor is a platinum resistor.

[0024] In a possible implementation manner, the first capacitor is a farad supercapacitor.

[0025] The circuit can operate in a "power-on state" and a "power-off short-time state".

[0026] When in the "power-on state", the present invention provides a high temperature warning method, which is applied to the high temperature warning circuit as described above. The working steps are as follows:

[0027] (1) controlling the first output terminal of the microprocessor to output a high level so that the switch unit enters a cut-off state;

[0028] (2) reading the pin voltage of the analog input terminal of the microprocessor in real time;

[0029] (3) calculating the real-time detection temperature of the thermistor according to the pin voltage;

[0030] (4) matching the real-time detected temperature with a preset temperature threshold to obtain a temperature matching result;

[0031] (5) controlling the output level of the second output terminal according to the temperature matching result, thereby controlling the on and off of the second light emitting diode.

[0032] In a possible implementation, calculating the real-time detected temperature of the thermistor according to the pin voltage includes the following specific steps:

[0033] S1. Performing Gaussian weighted moving average filtering on the collected pin voltage of the analog input terminal to obtain a filtered voltage;

[0034] S2. Calculating the measured resistance value of the thermistor according to the filtered voltage;

[0035] S3. Fitting the measured resistance value by a resistance fitting equation to obtain a fitting resistance value;

[0036] S4. Calculate the real-time detected temperature of the thermistor according to the fitted resistance value.

[0037] In a possible implementation, performing Gaussian weighted moving average filtering on the pin voltage to obtain a filtered voltage includes the following specific steps:

[0038] $1. Move all elements in the array with the number of elements being 2n+1 forward by one unit;

[0039] $2. Add the most recently measured pin voltage to the end of the array;

[0040] $3. Calculate the weighted value of each element in the array;

[0041] $4. Normalize the weighted value to obtain a normalized weight;

[0042] $5. Obtain the filtered voltage after filtering according to the weight calculation;

[0043] Wherein, n is an integer greater than 0.

[0044] In a possible implementation, the resistance fitting equation is obtained by the following specific steps:

[0045] ① Divide the resistance value corresponding to the measured temperature range into m-1 equal parts to obtain m endpoint values;

[0046] ② Arrange the m endpoint values ​​from small to large to form the first vector Y:

[0047] Y={y1,y2,…,y m},y i is the resistance value corresponding to the ith endpoint value among the m endpoint values;

[0048] ③ replacing the thermistor in the high temperature warning circuit with resistors having the resistance values ​​corresponding to the elements Y in the first vector in sequence, and measuring m measured resistance values ​​according to the method for obtaining the measured resistance values;

[0049] The m measured resistance values ​​are combined into a second vector X in the order of the first vector Y:

[0050] X={x1,x2,…,x m}, x i is the i-th measured resistance value among the m measured resistance values;

[0051] ④ Perform improved moving least squares fitting on the first vector Y and the second vector X to obtain the resistance fitting equation:

[0052] Vector X is the independent variable, vector Y is the dependent variable, a1(x), a2(x), a3(x), a4(x) are the fitting coefficient functions, and the one-dimensional cubic basis function p is selected. T =(1,x,x 2, x 3 ),but:

[0053] Y=a1(x)X 3 +a2(x)X 2 +a3(x)X+a4(x);

[0054] Define a(x) = [a1(x)a2(x)a3(x)a4(x)], then:

[0055] a(x)=A -1 (x)·B(x)·u;

[0056] in:

[0057] A(x)=P T W(x)P,B(x)=P T W(x),

[0058]

[0059] Among them, m is an integer greater than 3, i = 1, 2, …, m, w is the weight coefficient, W(x) is the weight coefficient matrix, A(x), B(x), are intermediate variables, and u = Y.

[0060] When in the "short-time power-off state", the circuit works as follows:

[0061] When the input power source switches from a power-on state to a power-off state, the microprocessor and the second operational amplifier do not work, and the switch unit controls the terminal voltage to be lower than the input terminal voltage under the voltage-dividing action of the first resistor and the sixth resistor, and controls the conduction between the input terminal and the output terminal. Since the voltage across the first capacitor cannot change suddenly, the first capacitor supplies power to the circuit at this time.

[0062] When the voltage adjustment unit is working, the voltage at the output end of the voltage adjustment unit switches repeatedly between high and low levels.

[0063] When the temperature is higher than the specified threshold, the first comparator outputs a high level, and the first light-emitting diode flashes to provide a high temperature warning. When the temperature is not higher than the specified threshold, the first comparator outputs a low level, and the first light-emitting diode will not light up.

[0064] The technical solution provided by the present invention has at least the following beneficial effects:

[0065] When the input power is switched from a power-on state to a power-off state, the microprocessor and the second operational amplifier do not work, and the system is in an ultra-low power consumption state. The first capacitor is used as a temporary power source to discharge energy to the outside, and no power supply equipment such as batteries is required. The switch unit controls its conduction under the voltage division effect of the first resistor and the sixth resistor, and can continue to provide a high temperature warning when the device is powered off for a long period of time, effectively preventing users from being scalded after the device is powered off, thereby improving the safety of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 A schematic diagram of a high temperature warning circuit provided by an embodiment of the present invention;

[0067] Figure 2 A working principle diagram of a high temperature warning circuit in a power-on state provided by an embodiment of the present invention;

[0068] Figure 3 A working principle diagram of a high temperature warning circuit in a short-time power-off state provided by an embodiment of the present invention;

[0069] Figure 4 A power-on state workflow diagram provided for an embodiment of the present invention;

[0070] Figure 5 An effect diagram of filtering by using the Gaussian weighted moving average filter provided in an embodiment of the present invention;

[0071] In the accompanying drawings, 10 is a switch unit; 20 is a voltage adjustment unit. DETAILED DESCRIPTION

[0072] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The embodiments are only used to explain the present invention and do not limit the protection scope of the present invention.

[0073] Please refer to Figures 1 to 5 A high temperature warning circuit provided by the present invention includes: a microprocessor MCU, a diode D1, a first capacitor C1, a switch unit 10, a first operational amplifier AP1, a second operational amplifier AP2, a first comparator U1, a first light emitting diode LED1, a second light emitting diode LED2, a thermistor RT1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, an eleventh resistor R11, and a voltage adjustment unit 20;

[0074] The positive power input terminal V+ of the microprocessor MCU is electrically connected to the positive electrode of the diode D1 and is used to connect the positive power input terminal VDD, the negative power input terminal V- and the first end of the first capacitor C1 are electrically connected to the ground, and the first output terminal P0.0 is electrically connected to the control terminal of the switch unit 10 and the first end of the first resistor R1 respectively;

[0075] The cathode of the diode D1 is electrically connected to the second end of the first capacitor C1, the input end of the switch unit 10, and the first end of the second resistor R2 respectively;

[0076] The output end of the switch unit 10 is electrically connected to the positive power supply electrode of the first operational amplifier AP1, the positive power supply electrode of the first comparator U1, and the first end of the third resistor R3 respectively;

[0077] The non-inverting input terminal of the first operational amplifier AP1 is electrically connected to the first terminal of the thermistor RT1 and the second terminal of the second resistor R2, respectively; the inverting input terminal thereof is electrically connected to its output terminal and the non-inverting input terminal of the first comparator U1, respectively; the negative power supply terminal thereof, the negative power supply terminal of the first comparator U1, the second terminal of the thermistor RT1, the second terminal of the first resistor R1, and the first terminal of the fourth resistor R4 are electrically connected to ground;

[0078] The inverting input terminal of the first comparator U1 is electrically connected to the second end of the third resistor R3 and the second end of the fourth resistor R4 respectively, and the output terminal thereof is electrically connected to the positive electrode of the first light emitting diode LED1;

[0079] The cathode of the first light emitting diode LED1 is electrically connected to the first end of the fifth resistor R5;

[0080] The second end of the fifth resistor R5 and the output end of the voltage adjustment unit 20 are electrically connected;

[0081] The non-inverting input terminal of the second operational amplifier AP2 is electrically connected to the first terminal of the thermistor RT1, the inverting input terminal thereof is electrically connected to the output terminal thereof and the analog input terminal P1.0 of the microprocessor MCU, the positive electrode of the power supply is electrically connected to the positive electrode of the diode D1, and the negative electrode of the power supply and the negative electrode of the second light emitting diode LED2 are electrically connected to the ground;

[0082] The anode of the second light emitting diode LED2 is electrically connected to the first end of the eleventh resistor R11;

[0083] The second end of the eleventh resistor R11 is electrically connected to the second output end of the microprocessor MCU.

[0084] In a possible implementation, the switch unit 10 includes a PMOS tube Q1 and a sixth resistor R6;

[0085] The gate of the PMOS tube Q1 is electrically connected to the first end of the sixth resistor R6 as the control end of the switch unit 10, the source thereof is electrically connected to the second end of the sixth resistor R6 as the input end of the switch unit 10, and the drain thereof is the output end of the switch unit 10.

[0086] In a possible implementation, the voltage adjustment unit 20 is used to reduce power consumption;

[0087] The voltage adjustment unit 20 includes a second capacitor C2, a second comparator U2, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, and a tenth resistor R10;

[0088] The first end of the second capacitor C2 is electrically connected to the inverting input end of the second comparator U2 and the first end of the tenth resistor R10, respectively, and the second end thereof is electrically connected to the ground;

[0089] The non-inverting input terminal of the second comparator U2 is electrically connected to the first end of the seventh resistor R7, the first end of the eighth resistor R8, and the first end of the ninth resistor R9, respectively; the positive electrode of the power supply and the second end of the ninth resistor R9 are electrically connected to the output end of the switch unit 10, respectively; the negative electrode of the power supply is electrically connected to the ground; and the output end is electrically connected to the second end of the fifth resistor R5, the second end of the eighth resistor R8, and the second end of the tenth resistor R10, respectively;

[0090] A second end of the seventh resistor R7 is electrically connected to the ground.

[0091] In a possible implementation, the thermistor RT1 is a platinum resistor.

[0092] In a possible implementation, the first capacitor C1 is a farad supercapacitor.

[0093] In this embodiment, the microprocessor MCU is a conventional processing chip, which can be a general single-chip microcomputer, such as a single-chip microcomputer of the STC series. The diode D1 is a conventional Schottky diode. The first capacitor C1 is a Farad supercapacitor, which is used to store energy and provide energy for external discharge. The second capacitor C2 is a conventional capacitor. The switch unit 10 is of conventional design and can be implemented based on a triode or a MOS tube. The first operational amplifier AP1 and the second operational amplifier AP2 are conventional operational amplifiers. The first comparator U1 and the second comparator U2 are conventional comparators. The first light-emitting diode LED1 and the second light-emitting diode LED2 are conventional light-emitting diodes. The thermistor RT1 is a conventional model and a platinum resistor can be used. The second resistor R2, the third resistor R3, and the fourth resistor R4 are high-precision resistors. The first resistor R1, the fifth resistor R5, the sixth resistor R6, the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, the tenth resistor R10, and the eleventh resistor R11 are all conventional resistors.

[0094] In a specific implementation, the positive electrode VDD of the input power supply is introduced by the power supply terminal P1, and the supply voltage is 5V. The microprocessor MCU adopts a single chip microcomputer of model STC8H64U. The diode D1 can adopt a Schottky diode of model IN5822. The first capacitor C1 is 5.5F, and the second capacitor C2 is 10uF. The first operational amplifier AP1 and the second operational amplifier AP2 adopt a model GS8331. The first comparator U1 and the second comparator U2 adopt a model LM311. The second resistor R2 and the third resistor R3 can both adopt a high-precision resistor of 2KΩ, and the fourth resistor R4 can adopt a high-precision resistor of 1.15KΩ. The first resistor R1 can be a 10KΩ resistor, the fifth resistor R5 can be a 1KΩ resistor, the sixth resistor R6 can be a 2KΩ resistor, the seventh resistor R7 can be a 20KΩ resistor, the eighth resistor R8 can be a 20KΩ resistor, the ninth resistor R9 can be a 20KΩ resistor, the tenth resistor R10 can be a 100KΩ resistor, and the eleventh resistor R11 can be a 1KΩ resistor. When the thermistor RT1 is a platinum resistor, the model can be PT1000, which is used to detect the current temperature of the equipment (such as: electric soldering iron, hot air gun and other welding equipment).

[0095] In this embodiment, the circuit can operate in a "power-on state" and a "power-off short-time state".

[0096] When in the "power-on state", the present invention provides a high temperature warning method, which is applied to the high temperature warning circuit as described above. The working steps are as follows:

[0097] In a specific implementation, after the device is powered on, the microprocessor MCU sets its first output terminal P0.0 to a high level, and the gate of the PMOS tube Q1 is turned off under the action of the high level, such as Figure 1 The output voltage VS of the drain of the PMOS tube Q1 is 0. The first operational amplifier AP1, the first comparator U1, and the voltage adjustment unit 20 are all in the power-off state, and the first light-emitting diode LED1 is always in the off state. Figure 2 shown.

[0098] In the high temperature warning workflow of the "power-on state", the microprocessor MCU uses its own ADC function to regularly read the pin voltage Vadc of the analog input terminal P1.0, and specifically calculates the real-time detection temperature corresponding to the thermistor RT1, that is, the device temperature t. When the device temperature t is lower than the specified threshold, the microprocessor MCU sets the output level of its second output terminal P0.1 to a low level, and the second light-emitting diode LED2 goes out; when the device temperature t exceeds the specified threshold, the microprocessor MCU sets the output level of its second output terminal P0.1 to a high level or to a high or low level that flips at a time, so that the second light-emitting diode LED2 is always on or flashing, thereby realizing the function of high temperature warning.

[0099] The present invention also provides a high temperature warning method, which is applied to the high temperature warning circuit as described above, and comprises the following specific steps:

[0100] S1: When the positive electrode of the input power supply VDD is powered on and enters the power-on state, the first output terminal P0.0 of the microprocessor MCU is controlled to output a high level so that the switch unit 10 enters the cut-off state;

[0101] S2: Read the pin voltage Vadc of the analog input terminal P1.0 of the microprocessor MCU in real time;

[0102] S3: Calculating the real-time detected temperature of the thermistor RT1 according to the pin voltage Vadc;

[0103] S4: Matching the real-time detected temperature with a preset temperature threshold to obtain a temperature matching result;

[0104] S5: controlling the output level of the second output terminal P0.1 according to the temperature matching result, so as to control the on and off of the second light emitting diode LED2.

[0105] In a possible implementation, in step S3, calculating the real-time detected temperature of the thermistor RT1 according to the pin voltage Vadc includes the following specific steps:

[0106] S31: performing Gaussian weighted moving average filtering on the pin voltage Vadc collected from the analog input terminal P1.0 to obtain a filtered voltage;

[0107] S32: Calculating the measured resistance value of the thermistor RT1 according to the filtered voltage;

[0108] S33: fitting the measured resistance value through a resistance fitting equation to obtain a fitting resistance value;

[0109] S34: Calculate the real-time detected temperature of the thermistor RT1 according to the fitted resistance value.

[0110] In this embodiment, the read pin voltage Vadc is subjected to Gaussian weighted moving average filtering to obtain a filtered voltage value Vt, i.e., a filtered voltage. The effect of Gaussian weighted moving average filtering is as follows: Figure 5 , Gaussian weighted moving average filtering can effectively remove white noise, retain the main characteristics of the signal, and improve the accuracy of temperature measurement. The measured resistance value RT of the platinum resistor is calculated by the filtered voltage value Vt:

[0111]

[0112] Wherein, R2 represents the resistance value of the second resistor R2, and VCC represents the power supply voltage of the power supply node VCC.

[0113] Substitute the calculated measured resistance value RT of the platinum resistor into the resistance fitting equation to obtain the resistance value of the fitted platinum resistor, i.e. the fitting resistance value Rt:

[0114] Rt=a1(x)*RT 3 +a2(x)*RT 2 +a3(x)*RT 1 +a4(x)

[0115] Among them, a1(x), a2(x), a3(x), and a4(x) are constants obtained by resistance fitting.

[0116] By fitting the resistance value Rt, the current temperature t of the device, i.e. the real-time detection temperature, can be calculated. The calculation formula is as follows:

[0117] Rt=1000(1+At+Bt 2 )

[0118] Among them, A and B are graduation constants, A = 0.0038623139728, B = -0.00000065314932626.

[0119] In a possible implementation, in step S31, Gaussian weighted moving average filtering is performed on the pin voltage Vadc to obtain a filtered voltage, including the following specific steps:

[0120] S311: Move all elements in the array with the number of elements being 2n+1 forward by one unit;

[0121] S312: Add the pin voltage Vadc measured most recently to the end of the array;

[0122] S313: Calculate the weighted value of each element in the array;

[0123] S314: normalizing the weighted value to obtain a normalized weight;

[0124] S315: Obtaining a filtered voltage according to the weight calculation;

[0125] Wherein, n is an integer greater than 0.

[0126] In this embodiment, when used for the first time, an array with 2n+1 elements is created, where n is an integer greater than 0, and the initial value of all elements is 0. D[i] represents the value of the element corresponding to the subscript i in the array, i=0, 1, ..., 2n.

[0127] Each time the analog input port voltage is collected, all elements in the array are moved forward by one unit, that is:

[0128] D[i-1]=D[i], i=1,2,...,2n.

[0129] Add the most recently measured pin voltage Vadc to the end of the array, that is:

[0130] D[2n]=Vadc.

[0131] Calculate the weighted value G(i) of each data:

[0132]

[0133] Wherein, i=1,2,…,2n, and σ represents the standard deviation set by the system.

[0134] Normalize and obtain the normalized weight ω(i):

[0135]

[0136] Among them, i=1,2,…,2n.

[0137] The filtered result F is:

[0138] F = ω(i)D(i).

[0139] In a possible implementation, in step S33, the resistance fitting equation is obtained by the following specific steps:

[0140] S331: Divide the resistance value corresponding to the measurement range into m-1 equal parts to obtain m endpoint values;

[0141] S332: Arrange the m endpoint values ​​from small to large to form a first vector Y:

[0142] Y={y1,y2,…,y m},y i is the resistance value corresponding to the ith endpoint value among the m endpoint values;

[0143] S333: replacing the thermistor RT1 in the high temperature warning circuit with resistors having resistance values ​​corresponding to the elements in the first vector Y in sequence, and measuring m measured resistance values ​​according to the method for obtaining the measured resistance value;

[0144] S334: Combining the m measured resistance values ​​into a second vector X according to the order of the first vector Y:

[0145] X={x1,x2,…,x m}, x i is the i-th measured resistance value among the m measured resistance values;

[0146] S335: Fitting the first vector Y and the second vector X using the improved moving least squares method to obtain a resistance fitting equation:

[0147] Y=a1(x)X 3 +a2(x)X 2 +a3(x)X+a4(x);

[0148] Define a(x) = [a1(x)a2(x)a3(x)a4(x)], then:

[0149] a(x)=A -1 (x)·B(x)·u;

[0150] in:

[0151] A(x)=P T W(x)P,B(x)=P T W(x),

[0152]

[0153] Among them, m is an integer greater than 3, i = 1, 2, …, m, w is the weight coefficient, W(x) is the weight coefficient matrix, A(x), B(x), are intermediate variables, and u = Y.

[0154] The high temperature warning circuit and high temperature warning method proposed in the present invention adopt Gaussian weighted moving average filtering, improved moving least squares fitting and other technical solutions when the device is powered on to obtain the temperature, which can improve the accuracy of temperature measurement.

[0155] When in the "short-time power-off state", the circuit works as follows:

[0156] When the input power source is switched from the power-on state to the power-off state, the microprocessor MCU and the second operational amplifier AP2 do not work, the switch unit 10 is turned on, and the working circuit part is as follows: Figure 3 shown.

[0157] When the temperature of thermistor RT1 is higher than the specified threshold, the first comparator U1 outputs a high level, that is, U1(c)=VS, and the state of the first light-emitting diode LED1 also changes with the voltage change of node Y, and the first light-emitting diode LED1 flashes, thereby realizing the function of high temperature warning by flashing the first light-emitting diode LED1. When the resistance value of thermistor RT1 is less than or equal to the specified value, the first comparator U1 outputs a low voltage, that is, U1(c)=0. At this time, no matter whether the voltage at node Y is low or high, the first light-emitting diode LED1 is cut off, and the first light-emitting diode LED1 is in an off state, and will not trigger a high temperature warning. The specific analysis is as follows:

[0158] φ1. In the short-time power-off state, when the temperature of thermistor RT1 is higher than the specified threshold, the first comparator U1 outputs voltage U1(c)=VS. When the temperature of thermistor RT1 is not higher than the specified threshold, the first comparator U1 outputs voltage U1(c)=0. The specific analysis is as follows:

[0159] After the device is powered off, since the voltage across the first capacitor C1 cannot change suddenly, the input voltage of the switch unit 10, i.e., the power supply voltage of the power supply node VCC (the power supply voltage of the power supply node VCC can be directly represented by VCC), will slowly decrease. Due to the voltage division effect of the first resistor R1 and the sixth resistor R6, the voltage at the input end of the switch unit is higher than the voltage of its control section, and the switch unit 10 is turned on, VS = VCC. The resistance value of the thermistor RT1 is represented by RT, the resistance value of the second resistor R2 is represented by R2, and the resistance value of the third resistor R3 is represented by R3.

[0160] The voltage U1(+) at the non-inverting input terminal of the first comparator U1 is:

[0161] U1(+)=VCC*RT / (RT+R2)

[0162] The voltage U1(-) at the inverting input terminal of the first comparator U1 is:

[0163] U1(-)=VS*R4 / (R4+R3)

[0164] When the resistance value of thermistor RT1 is higher than the specified value, that is, the temperature is higher than the specified threshold,

[0165] U1(+)>U1(-)

[0166] At this time, the voltage at the non-inverting input terminal of the first comparator U1 is higher than the voltage at the inverting input terminal, and the output voltage of the first comparator U1 is U1 (c)=VS.

[0167] When the resistance value of thermistor RT1 is less than or equal to the specified value, that is, the temperature is less than or equal to the specified threshold, then

[0168] U1(+) <U1(-)

[0169] At this time, the voltage at the non-inverting input terminal of the first comparator U1 is lower than the voltage at the inverting input terminal, and the output voltage U1 (c) of the first comparator U1 is equal to 0.

[0170] φ2. During a period of power failure, the voltage regulation unit works, and the level of the output node Y of the voltage regulation unit switches automatically between high and low levels. The specific working process is analyzed as follows:

[0171] Ⅰ. In the initial state of power-off of the device, the voltage across the second capacitor C2 is zero, that is, the voltage at the inverting input terminal of the second comparator U2 is 0, and the non-inverting input terminal of the second comparator U2 is connected to the node where VS is located through the ninth resistor R9. The voltage at the non-inverting input terminal of the second comparator U2 is greater than 0, and the output terminal voltage of the second comparator U2 is a high level. At this time: the output voltage of the second comparator U2 U2 (c) = VS. The non-inverting input voltage U2 (+H) of the second comparator U2 is obtained as follows:

[0172]

[0173] At this time, the output terminal of the second comparator U2 is at a high level to charge the second capacitor C2, that is, U2(c)=VS, and the voltage across the second capacitor C2 gradually increases.

[0174] Ⅱ. When the voltage across the second capacitor C2 is higher than U2(+H), that is, the inverting input voltage of the second comparator U2 is higher than the non-inverting input voltage of the second comparator U2, the output voltage of the second comparator U2 is low level. At this time, the output voltage U2(c) of the second comparator U2 = 0. The non-inverting input voltage U2(+L) of the second comparator U2 is obtained as:

[0175]

[0176] At this time, the output of the second comparator U2 is at a low level, ie, U2(c)=0, the second capacitor C2 will be discharged through the tenth resistor R10, and the voltage across the second capacitor C2 will gradually decrease.

[0177] III. When the voltage across the second capacitor C2 drops below U2(+L), that is, the inverting input voltage of the second comparator U2 is lower than the non-inverting input voltage of the second comparator U2, the output voltage of the second comparator U2 is high. At this time, the output voltage U2(c) of the second comparator U2 = VS. At this time, the non-inverting input voltage U2(+H) of the second comparator U2 is:

[0178]

[0179] At this time, the output terminal of the second comparator U2 is at a high level to charge the second capacitor C2, that is, U2(c)=VS, and the voltage across the second capacitor C2 gradually increases.

[0180] IV. Steps II and III are repeated continuously, and the output voltage of the second comparator U2 is automatically switched between high and low levels.

[0181] Therefore, during a period of power failure, the output voltage of the second comparator U2 automatically switches between high and low levels, and so on, that is, the level of the output node Y of the voltage regulating unit automatically switches between high and low levels.

[0182] In summary, when the temperature of thermistor RT1 is higher than the specified threshold, the first comparator U1 outputs a high voltage U1(c)=VS, and the state of the first light-emitting diode LED1 also changes with the voltage change of node Y, and the first light-emitting diode LED1 flashes, thereby realizing the function of high temperature warning by flashing the first light-emitting diode LED1, while reducing power consumption. When the resistance value of thermistor RT1 is less than or equal to the specified value, the first comparator U1 outputs a low voltage U1(c)=0, at this time, no matter whether the voltage at node Y is low or high, the first light-emitting diode LED1 is cut off, and the first light-emitting diode LED1 is in an off state, and will not trigger a high temperature warning.

[0183] It should be noted that if the device is powered off for a long time, there will be basically no high temperature. Therefore, using the first capacitor C1 as a temporary power source is sufficient to achieve a high temperature warning for a period of time after the power is off. The high temperature warning circuit in the present invention will remind the user if the device has an over-high temperature when the device stops running or even after a period of power outage, thereby effectively improving the safety of the welding equipment.

[0184] The above embodiments should not limit the present invention in any way, and any technical solutions obtained by equivalent replacement or equivalent conversion shall fall within the protection scope of the present invention.

Claims

1. A high temperature warning circuit, characterized in that: include: A microprocessor, a diode, a first capacitor, a switch unit, a first operational amplifier, a second operational amplifier, a first comparator, a first light emitting diode, a second light emitting diode, a thermistor, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, an eleventh resistor, and a voltage adjustment unit; The positive power input terminal of the microprocessor is electrically connected to the anode of the diode and is used to connect the positive input power terminal, the negative power input terminal and the first end of the first capacitor are electrically connected to the ground, and the first output terminal is electrically connected to the control terminal of the switch unit and the first end of the first resistor respectively; The cathode of the diode is electrically connected to the second end of the first capacitor, the input end of the switch unit, and the first end of the second resistor respectively; The output end of the switch unit is electrically connected to the positive power supply electrode of the first operational amplifier, the positive power supply electrode of the first comparator, and the first end of the third resistor respectively; The non-inverting input terminal of the first operational amplifier is electrically connected to the first terminal of the thermistor and the second terminal of the second resistor respectively, the inverting input terminal thereof is electrically connected to its output terminal and the non-inverting input terminal of the first comparator respectively, and the negative power supply terminal thereof, the negative power supply terminal of the first comparator, the second terminal of the thermistor, the second terminal of the first resistor, and the first terminal of the fourth resistor are electrically connected to the ground; The inverting input terminal of the first comparator is electrically connected to the second end of the third resistor and the second end of the fourth resistor respectively, and the output terminal thereof is electrically connected to the anode of the first light emitting diode; The cathode of the first light emitting diode is electrically connected to the first end of the fifth resistor; The second end of the fifth resistor is electrically connected to the output end of the voltage adjustment unit; The non-inverting input terminal of the second operational amplifier is electrically connected to the first terminal of the thermistor, the inverting input terminal thereof is electrically connected to the output terminal thereof and the analog input terminal of the microprocessor respectively, the positive electrode of the power supply is electrically connected to the positive electrode of the diode, and the negative electrode of the power supply and the negative electrode of the second light-emitting diode are electrically connected to the ground; The anode of the second light emitting diode is electrically connected to the first end of the eleventh resistor; The second end of the eleventh resistor is electrically connected to the second output end of the microprocessor.

2. The high temperature warning circuit according to claim 1, characterized in that: The switch unit includes a PMOS tube and a sixth resistor; The gate of the PMOS tube is electrically connected to the first end of the sixth resistor as the control end of the switch unit, the source thereof is electrically connected to the second end of the sixth resistor as the input end of the switch unit, and the drain thereof serves as the output end of the switch unit.

3. The high temperature warning circuit according to claim 1, characterized in that: The voltage adjustment unit is used to reduce power consumption, and includes a second capacitor, a second comparator, a seventh resistor, an eighth resistor, a ninth resistor, and a tenth resistor; The first end of the second capacitor is electrically connected to the inverting input end of the second comparator and the first end of the tenth resistor respectively, and the second end thereof is electrically connected to the ground; The non-inverting input terminal of the second comparator is electrically connected to the first end of the seventh resistor, the first end of the eighth resistor, and the first end of the ninth resistor, respectively; the positive electrode of the power supply and the second end of the ninth resistor are electrically connected to the output terminal of the switch unit, respectively; the negative electrode of the power supply is electrically connected to the ground; and the output terminal is electrically connected to the second end of the fifth resistor, the second end of the eighth resistor, and the second end of the tenth resistor, respectively; The second end of the seventh resistor is electrically connected to the ground.

4. The high temperature warning circuit according to claim 1, characterized in that: The thermistor is a platinum resistor.

5. The high temperature warning circuit according to claim 1, characterized in that: The first capacitor is a Farad supercapacitor.

6. The high temperature warning circuit according to claim 2, characterized in that: The high temperature warning circuit includes a "power-off short-time state". When the high temperature warning circuit is in the "power-off short-time state", the input power supply is switched from the power-on state to the power-off state, the microprocessor and the second operational amplifier do not work, and the switch unit controls the terminal voltage to be lower than the input terminal voltage under the voltage division effect of the first resistor and the sixth resistor, and controls the conduction between the input terminal and the output terminal. Since the voltage across the first capacitor cannot change suddenly, the capacitor supplies power to the circuit at this time; When the voltage adjustment unit is working, the voltage at the output end of the voltage adjustment unit switches repeatedly between high and low levels; When the temperature is higher than the specified threshold, the first comparator outputs a high level, and the first light-emitting diode flashes to provide a high temperature warning. When the temperature is not higher than the specified threshold, the first comparator outputs a low level, and the first light-emitting diode will not light up.

7. A high temperature warning method, characterized in that: Applied to the high temperature warning circuit as claimed in claim 2, the high temperature warning circuit also includes a "power-on state", when the high temperature warning circuit is in the "power-on state", the following specific steps are included: Controlling the first output terminal of the microprocessor to output a high level so that the switch unit enters a cut-off state; Reading the pin voltage of the analog input terminal of the microprocessor in real time; Calculating the real-time detected temperature of the thermistor according to the pin voltage; Matching the real-time detected temperature with a preset temperature threshold to obtain a temperature matching result; The output level of the second output terminal is controlled according to the temperature matching result, thereby controlling the on and off of the second light emitting diode.

8. The high temperature warning method according to claim 7, characterized in that: Calculating the real-time detected temperature of the thermistor according to the pin voltage includes the following specific steps: Performing Gaussian weighted moving average filtering on the collected pin voltage of the analog input terminal to obtain a filtered voltage; calculating a measured resistance value of the thermistor based on the filtered voltage; The measured resistance value is fitted by a resistance fitting equation to obtain a fitted resistance value; The real-time detected temperature of the thermistor is calculated according to the fitted resistance value.

9. The high temperature warning method according to claim 8, characterized in that: Performing Gaussian weighted moving average filtering on the pin voltage to obtain a filtered voltage includes the following specific steps: Move all elements in an array with 2n+1 elements forward by one unit; Add the most recently measured pin voltage to the end of the array; Calculate the weighted value of each element in the array; Normalizing the weighted value to obtain a normalized weight; Obtaining a filtered voltage after filtering according to the weight calculation; Wherein, n is an integer greater than 0.

10. The high temperature warning method according to claim 8, characterized in that: The resistance fitting equation is obtained by the following specific steps: Divide the resistance value corresponding to the measurement temperature range into m-1 equal parts to obtain m endpoint values; Arrange the m endpoint values ​​from small to large to form the first vector Y: Y={y1,y2,…,y m },y i is the resistance value corresponding to the ith endpoint value among the m endpoint values; replacing the thermistor in the high temperature warning circuit with resistors having resistance values ​​corresponding to the elements in the first vector Y in sequence, and measuring m measured resistance values ​​according to the method for obtaining the measured resistance value; The m measured resistance values ​​are combined into a second vector X in the order of the first vector Y: X={x1,x2,…,x m }, x i is the i-th measured resistance value among the m measured resistance values; The first vector Y and the second vector X are fitted by the improved moving least squares method to obtain the resistance fitting equation: Vector X is the independent variable, vector Y is the dependent variable, a1(x), a2(x), a3(x), a4(x) are the fitting coefficient functions, and the one-dimensional cubic basis function p is selected. T =(1,x,x 2, x 3 ),but: Y=a1(x)X 3 +a2(x)X 2 +a3(x)X+a4(x); Define a(x) = [a1(x)a2(x)a3(x)a4(x)], then: a(x)=A -1 (x)·B(x)·u; in: a(x)=P T W(x)P,B(x)=P T W(x), Among them, m is an integer greater than 3, i = 1, 2, …, m, w is the weight coefficient, W(x) is the weight coefficient matrix, A(x), B(x), are intermediate variables, and u = Y.

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