CN214627391U - Heating control circuit and electric appliance - Google Patents
Heating control circuit and electric appliance Download PDFInfo
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- CN214627391U CN214627391U CN202120386466.5U CN202120386466U CN214627391U CN 214627391 U CN214627391 U CN 214627391U CN 202120386466 U CN202120386466 U CN 202120386466U CN 214627391 U CN214627391 U CN 214627391U
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Abstract
An embodiment of the utility model provides a heating control circuit, including temperature detection circuit and gate circuit. The temperature detection circuit is used for generating a temperature signal; the first input end of the gating circuit is used for being connected with a first direct current power supply, the second input end of the gating circuit is connected with the temperature detection circuit, the power supply output end of the gating circuit is used for being connected with the heating circuit, and the gating circuit is used for outputting a power supply signal to the heating circuit at the power supply output end when the temperature signal shows that the current temperature is lower than a preset threshold value. The heating control circuit with the circuit structure can effectively avoid the problem that the heating circuit is accidentally heated immediately after being electrified, and enhances the safety of the electric appliance. In addition, the heating control circuit is simple in structure, and the use of high-power electric devices such as relays is avoided. Therefore, the control function is satisfied, the use cost of the user is saved, and the benefit of the user is guaranteed.
Description
Technical Field
The utility model relates to a heating control field of electrical apparatus, more specifically relate to a heating control circuit and including its electrical apparatus.
Background
In the current electric appliances with heating function, the heating control function is generally realized by using devices such as silicon controlled rectifier or relay. When the electric appliance is heated, the heating control circuit part of the electric appliance is most easily out of control. Once the electric appliance is out of control, the silicon controlled rectifier and other devices are immediately conducted and heated as soon as the electric appliance is electrified. Further, problems such as damage of the electric appliance may occur, thereby causing a safety hazard to the user.
In the prior art, a triode or a darlington tube is generally arranged in front of a thyristor and used as a part of a heating control circuit for controlling the conduction of the thyristor. However, there is still a possibility in this solution that the transistor or darlington tube is broken down immediately upon power-up of the appliance. In order to solve the problems, a relay is added in part of technical schemes and is used for controlling a zero line of an alternating current power supply. In this type of scheme, only if the relay is turned on, the main circuit can be turned on, and the electric appliance can start heating.
However, the relay added in the prior art belongs to a high-power electric device, which increases the use cost of users. And as the power of the relay increases, the cost becomes higher and higher, seriously impairing the benefit of the user.
SUMMERY OF THE UTILITY MODEL
The present invention has been made in view of the above problems. According to the utility model discloses an aspect provides a heating control circuit, including temperature-detecting circuit, still include the gating circuit. The temperature detection circuit is used for generating a temperature signal; the first input end of the gating circuit is used for being connected with a first direct current power supply, the second input end of the gating circuit is connected with the temperature detection circuit, the power supply output end of the gating circuit is used for being connected with the heating circuit, and the gating circuit is used for outputting a power supply signal to the heating circuit at the power supply output end when the temperature signal shows that the current temperature is lower than a preset threshold value.
In the above technical solution, the gate circuit outputs the power signal at the power output terminal thereof under the control of the temperature signal output by the temperature detection circuit, so as to provide the power signal for the heating circuit when heating is required. The power supply signal can control the on-off of the heating circuit so as to control the heating operation of the heating circuit. The heating control circuit with the circuit structure can effectively avoid the problem that the heating circuit is accidentally heated immediately after being electrified, and enhances the safety of the electric appliance. In addition, the heating control circuit is simple in structure, and the use of high-power electric devices such as relays is avoided. Therefore, the control function is satisfied, the use cost of the user is saved, and the benefit of the user is guaranteed.
Illustratively, the gate circuit includes a main control circuit, an integrating circuit, and an output circuit connected in sequence; the main control circuit is provided with a second input end for outputting a square wave signal when the temperature signal indicates that the current temperature is lower than a preset threshold value; the integrating circuit is used for integrating the square wave signal to generate an integrated signal; the output circuit is provided with a first input end and a power output end, and is used for controlling the first input end and the power output end to be conducted based on the integral signal so as to output a power signal at the power output end.
The gating circuit with the circuit structure can output the power supply signal with less interference to the heating circuit more accurately and timely. Thereby, the accuracy of the control of the heating circuit is improved.
Illustratively, the integrating circuit and the output circuit are connected via a voltage stabilizing circuit.
The voltage stabilizing circuit is arranged to ensure that the integral signal received by the output circuit is stable. Based on the stable integrated signal, the output circuit can better control the output of the power supply signal. And further effectively avoids accidents such as subsequent circuit faults and the like caused by the interference of the integral signal or errors generated by other conditions.
Illustratively, the voltage stabilizing circuit comprises a first capacitor and a first resistor, wherein a first end of the first resistor is connected with the output end of the integrating circuit and is grounded through the first capacitor, and a second end of the first resistor is connected with the input end of the output circuit.
The values of the first capacitor and the first resistor can be adjusted according to requirements, so that the charging and discharging speed of the first capacitor can be controlled, and further the on-off speed of the output circuit can be controlled. Therefore, the scheme not only improves the control accuracy of the heating control circuit, but also improves the application range of the heating control circuit.
Illustratively, the integration circuit comprises a second resistor, a second capacitor and a first diode which are connected in sequence, wherein the anode of the first diode is connected with the second capacitor, and the cathode of the first diode is connected with the output circuit.
The integrating circuit plays a role of converting waveforms in the gating circuit and has a function of delaying the time of a subsequent circuit. The possibility that the gating circuit outputs the power signal to the heating circuit under the control of the temperature signal upon power-up is also reduced. In addition, the first diode is arranged in the integrating circuit, so that the one-way conductivity of the diode can be utilized, the current of a subsequent circuit is effectively prevented from flowing back to the integrating circuit and the main control circuit, and the power consumption is reduced.
Illustratively, the anode of the first diode is also connected to the cathode of the second diode, and the anode of the second diode is grounded.
The provision of the second diode better ensures that the square wave signal can pass through the second capacitor unimpeded.
Illustratively, the main control circuit is implemented by a chip, and the chip is further provided with a fourth input end for connecting a second direct current power supply.
The chip is used for realizing the control function of the main control circuit, so that the use of electronic components can be reduced, the circuit is simplified, the system integration level is improved, and the circuit fault probability is reduced.
Illustratively, the output circuit comprises an NPN-type switching transistor, a base of the NPN-type switching transistor is connected to the integrating circuit, a collector of the NPN-type switching transistor is provided as the first input terminal, and an emitter of the NPN-type switching transistor is provided as the power output terminal.
According to the scheme, the output circuit has the function of enabling the first direct current power supply to output the power supply signal through the power supply output end under the control of the integral signal. In this scheme, the above process can be implemented with one switching circuit. Compared with a common mechanical switch, the electronic switch formed by the NPN type switching triode has the advantages of small volume, no mechanical contact, high switching speed, convenience for electric signal control and the like. Therefore, the heating control circuit is high in control accuracy and small in size.
Illustratively, the heating control circuit further comprises a zero-crossing detection circuit, the zero-crossing detection circuit is used for connecting the alternating current power supply and detecting the zero-crossing point of the alternating current output by the alternating current power supply to generate a zero-crossing signal; and the gating circuit is used for outputting a power supply signal to the heating circuit at the output end of the power supply when the temperature signal indicates that the current temperature is lower than the preset threshold value and the zero-crossing signal indicates that the alternating current is at a zero-crossing point.
The conduction time of the heating circuit is set at the lowest point of the voltage of the alternating current power supply, namely the zero crossing point of the alternating current power supply, so that the interference can be reduced to the greatest extent. The zero-crossing detection circuit is arranged in the heating control circuit, so that the real zero-crossing point can be captured to the maximum extent. Thereby, system interference is desirably reduced.
Illustratively, the zero-crossing detection circuit includes a charging circuit and a discharging circuit; the discharge circuit includes: the PNP type switch triode, the third electric capacity, the third diode, the third resistance, fourth resistance and opto-coupler element, charging circuit's first end and second end are connected respectively to the first end and the second end of third resistance, the first end of third resistance is connected through the third diode to the projecting pole of PNP type switch triode, the first end of third resistance is connected to the base of PNP type switch triode, the first end of PNP type switch triode's collecting electrode is through fourth resistance connection opto-coupler element, the projecting pole of PNP type switch triode is connected to the first end of third electric capacity, the second end of third electric capacity and opto-coupler element's second end all are connected to the second end of third resistance.
The zero-crossing detection circuit reasonably utilizes the discharge characteristic of the RC circuit, so that the voltage on the third capacitor is maintained at relatively stable voltage, the reduction of the conduction voltage of the optical coupling element caused by the over-fast discharge of the third capacitor is avoided, and the delay is generated on the rising edge. Therefore, the accuracy of the zero-crossing detection result is ensured, and the system interference is reduced.
Illustratively, the charging circuit includes: a fourth diode and a fifth resistor; the cathode of the fourth diode is connected with the input zero line of the alternating current power supply, and the anode of the fourth diode is connected with the second end of the third resistor; the first end of the fifth resistor is connected with an input live wire of the alternating current power supply, and the second end of the fifth resistor is connected with the first end of the third resistor.
The fourth diode can utilize its one-way conductivity to realize the function of cutting off more ideally, and the fifth resistance can realize more reasonable partial pressure effect, further guarantees zero cross detection's accuracy, and then guarantees that system's interference is less.
Illustratively, the third end of the optical coupling element is connected with the third input end of the gating circuit and is used for being connected with a third direct current power supply through a sixth resistor, the fourth end of the optical coupling element is grounded, and the third end of the optical coupling element and the fourth end of the optical coupling element are further connected through a fourth capacitor.
It is understood that when the sixth resistor and the fourth capacitor have the above connection relationship, they form an RC low-pass filter circuit. The RC low-pass filter circuit has the function of preventing signals with the signal frequency higher than the cut-off frequency from passing through and allowing signals with the signal frequency lower than the cut-off frequency to pass through. The cutoff frequency sixth resistor is related to the value of the fourth capacitor. Different cut-off frequencies can be obtained by changing the values of the sixth resistor and the fourth capacitor. Therefore, the interference in the signal can be effectively removed, and the error of the output zero-crossing signal is reduced.
Illustratively, the temperature detection circuit is a thermocouple detection circuit, the thermocouple detection circuit includes an operational amplifier, a non-inverting input circuit, an inverting input circuit, and an operational amplifier output circuit, which are respectively connected to a non-inverting input terminal, an inverting input terminal, and an output terminal of the operational amplifier, wherein the non-inverting input circuit includes a thermocouple, and the inverting input terminal and the output terminal of the operational amplifier are connected via an eleventh resistor.
In this embodiment, a thermocouple is used as a means for temperature detection. The thermocouple has the advantages of high measurement accuracy, wide range, long service life and the like. The temperature detection circuit with the circuit structure can output the amplified temperature signal, so that the gating circuit can control the heating operation of the heating circuit based on the temperature signal. In addition, the virtual ground exists in the inverse proportion operation circuit, so that the stability of the temperature detection circuit during working is ensured, and the heating control circuit is further ensured to heat when heating is really needed.
Illustratively, the positive pole of the thermocouple is connected with the non-inverting input end through a seventh resistor, the negative pole of the thermocouple is connected with the central point of a first resistor voltage divider, the first end of the first resistor voltage divider is used for connecting a fourth direct-current power supply, and the second end of the first resistor voltage divider is grounded; the inverting input circuit comprises an eighth resistor, the first end of the eighth resistor is connected with the inverting input end, and the second end of the eighth resistor is connected with the central point of the second resistor divider; the first end of the second resistor voltage divider is used for being connected with a fifth direct-current power supply through a ninth resistor, and the second end of the second resistor voltage divider is grounded; a fifth diode connected in parallel with the second resistor divider is also connected between the first terminal and the second terminal of the second resistor divider.
In the above-described aspect, the temperature detection circuit uses fewer components and has a relatively simple circuit configuration. The seventh resistor can be used for impedance matching, so that all signals can be transmitted to the non-inverting input end of the operational amplifier, and almost no signals are reflected back to the thermocouple and/or the first resistor divider, so that the energy efficiency can be improved. The influence of temperature drift generated in the process of detecting the temperature by the thermocouple can be eliminated only by arranging the fifth diode in the inverting input circuit. Therefore, the temperature detection circuit comprising the simple components can detect the heating temperature, output relatively accurate temperature signals and further accurately control the heating operation of the heating circuit through the gating circuit.
Illustratively, the operational amplifier output circuit comprises a tenth resistor and a fifth capacitor, wherein a first end of the tenth resistor is connected with the output end of the operational amplifier, and a second end of the tenth resistor is connected with the second input end of the gating circuit and is grounded through the fifth capacitor.
And a tenth resistor and a fifth capacitor in the operational amplifier output circuit form an RC low-pass filter circuit. The RC low-pass filter circuit has the function of preventing signals with the signal frequency higher than the cut-off frequency from passing through and allowing signals with the signal frequency lower than the cut-off frequency to pass through. In this circuit, the cutoff frequency is related to the values of the tenth resistor and the fifth capacitor. Different cut-off frequencies can be obtained by varying the values of the tenth resistor and the fifth capacitor. Therefore, the interference in the signals can be effectively removed, more accurate temperature signals can be obtained, and further more accurate power signals with more accurate control effect can be obtained.
Illustratively, a sixth capacitor is connected between the non-inverting input terminal and the inverting input terminal.
The sixth capacitor is arranged between the non-inverting input end and the inverting input end and is used for filtering other signal interference except interference ripples in the direct current power supply.
Illustratively, the power input first end of the operational amplifier is grounded, and the power input second end of the operational amplifier is used for connecting the sixth direct current power supply and is also grounded via the seventh capacitor.
Therefore, the seventh capacitor can effectively filter the interference ripple, so that the temperature signal output by the operational amplifier through the operational amplifier output circuit is more accurate, and the error is smaller.
According to another aspect of the present invention, there is provided an electrical appliance, comprising the heating control circuit and the heating circuit connected to the heating control circuit.
The electric appliance provided with the heating control circuit can effectively avoid the situations that the electric appliance is heated immediately after being electrified, and the like, thereby ensuring the use safety of the electric appliance and ensuring the personal safety of users. In addition, no high-power electric device such as a relay is arranged in the heating control circuit of the electric appliance, so that the use cost of a user is reduced.
Illustratively, the appliance is a steam oven. The heating control circuit can normally measure the temperature of the steam oven in work, and then normally controls the heating of the steam oven. Therefore, the heating control requirement of the steaming oven is met.
The above description is only an overview of the technical solutions of the present invention, and in order to make the technical means of the present invention more clearly understood, the present invention may be implemented according to the content of the description, and in order to make the above and other objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the present invention is given.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail embodiments of the present invention with reference to the attached drawings. The accompanying drawings are included to provide a further understanding of the embodiments of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the invention and not to limit the invention. In the drawings, like reference numbers generally represent like parts or steps.
Fig. 1 shows a schematic block diagram of a heating control circuit according to an exemplary embodiment of the present invention;
fig. 2 shows a schematic block diagram of a heating control circuit according to another exemplary embodiment of the present invention;
fig. 3 shows a schematic diagram of a gating circuit in a heating control circuit according to an exemplary embodiment of the present invention;
fig. 4 shows a schematic diagram of a zero crossing detection circuit in a heating control circuit according to an exemplary embodiment of the present invention;
fig. 5 shows a schematic diagram of a temperature detection circuit in a heating control circuit according to an exemplary embodiment of the present invention.
Wherein the figures include the following reference numerals:
100. a heating control circuit; 110. a temperature detection circuit; 111. an operational amplifier; 112. an inverting input circuit; 113. a positive phase input circuit; 114. an operational amplifier output circuit; 1121. a second resistive divider; 1131. a first resistive divider; 120. a gating circuit; 121. a master control circuit; 122. an integrating circuit; 123. an output circuit; 124. a voltage stabilizing circuit; 130. a heating circuit; 140. a zero-crossing detection circuit; 141. a charging circuit; 142. a discharge circuit.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, exemplary embodiments according to the present invention will be described in detail below with reference to the accompanying drawings. It is to be understood that the described embodiments are merely exemplary of the present invention and are not intended to limit the invention to the particular embodiments described herein. Based on the embodiments of the present invention described in the present application, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present invention.
According to the utility model discloses an aspect provides a heating control circuit. Fig. 1 shows a schematic block diagram of a heating control circuit 100 according to an exemplary embodiment of the present invention. As shown in fig. 1, the heating control circuit 100 is used to connect the heating circuit 130 to control the heating operation of the heating circuit 130 by outputting a power signal to the heating circuit 130. Heating circuit 130 may include a heating plate or the like for heating. In the present application, no limitation is made to the specific circuit structure of the heating circuit 130, and any circuit that can realize the heating function is within the protection scope of the present application.
The heating control circuit 100 includes not only the temperature detection circuit 110 but also the gate circuit 120. The temperature detection circuit 110 is used to generate a temperature signal. A first input of the gating circuit 120 is for connection to a first dc power supply. A second input terminal of the gating circuit 120 is connected to the temperature detection circuit 110. The power output terminal of the gating circuit 120 is connected to the heating circuit 130 to provide a control power to the heating circuit 130 when heating is required according to the temperature signal input by the temperature detection circuit 110. Specifically, the gating circuit 120 is configured to output a power signal to the heating circuit 130 at the power output when the temperature signal indicates that the current temperature is below the preset threshold.
As shown in fig. 1, a first input terminal of the gating circuit 120 is connected to a first dc power supply. Illustratively, the first dc power supply may be a 12V dc power supply, for example. A second input of the gating circuit 120 is connected to the temperature detection circuit 110 to receive the temperature signal. After power-on, the temperature detection circuit 110 starts to operate, and is used for detecting the temperature of the preset point and generating a corresponding temperature signal. The temperature signal includes current temperature information of a preset point. When heating is required, i.e. the temperature signal received by the gating circuit 120 indicates that the current temperature is lower than the preset threshold, the gating circuit 120 outputs a power signal to the heating circuit 130 at its power output terminal. When heating is not required, the gate circuit 120 no longer outputs the power signal to the heating circuit 130. It will be appreciated that the aforementioned predetermined threshold may be any reasonable value, such as 100 degrees celsius, 85 degrees celsius, or the like. With the power supply signal providing power, the heating circuit 130 may perform a heating operation. When the temperature signal indicates that the current temperature is equal to or higher than the preset threshold, the gating circuit 120 will no longer output the power signal to the heating circuit 130. The heating circuit 130 no longer has a power signal input and thus stops heating.
In the above technical solution, the gating circuit 120 outputs the power signal at the power output terminal thereof under the control of the temperature signal output by the temperature detection circuit 110, so as to provide the power signal for the heating circuit 130 when heating is required. The power signal can control the on/off of the heating circuit 130, thereby controlling the heating operation of the heating circuit 130. The heating control circuit 100 with the circuit structure can effectively avoid the problems of accidental heating immediately after the electric appliance is electrified, and the like, and enhances the safety of the electric appliance. In addition, the heating control circuit 100 has a simple structure, and avoids the use of high-power electric devices such as relays. Therefore, the control function is satisfied, the use cost of the user is saved, and the benefit of the user is guaranteed.
Fig. 2 shows a schematic block diagram of a heating control circuit 100 according to another exemplary embodiment of the present invention. As shown in fig. 2, the heating control circuit 100 further includes a zero-crossing detection circuit 140. The zero-crossing detection circuit 140 is used for connecting an ac power supply and detecting a zero-crossing point of an ac power output by the ac power supply to generate a zero-crossing signal. It is understood that the ac power source connected to the zero-crossing detection circuit 140 may be an external power source for supplying power to the appliance, i.e., an external power grid. A third input of the gating circuit 120 is connected to a zero crossing detection circuit 140. The gating circuit 120 is configured to output a power signal to the heating circuit 130 at a power output terminal thereof when the temperature signal output by the temperature detection circuit 110 indicates that the current temperature is lower than the preset threshold value and the zero-crossing signal output by the zero-crossing detection circuit 140 indicates that the alternating current is at the zero-crossing point. By setting the conduction time of the heating circuit 130 at the lowest point of the voltage of the ac power source, i.e., the zero-crossing point of the ac power, the interference can be minimized. The zero-crossing detection circuit 140 is provided in the heating control circuit 100 to capture the true zero-crossing point to the maximum extent. Thereby, system interference is desirably reduced.
Fig. 3 shows a schematic diagram of the gating circuit 120 in the heating control circuit 100 according to an exemplary embodiment of the present invention. As shown in fig. 3, the gate circuit 120 includes a main control circuit 121, an integration circuit 122, and an output circuit 123, which are connected in sequence. The main control circuit 121 is provided with the aforementioned second input terminal and third input terminal, and is configured to output a square wave signal when the temperature signal indicates that the current temperature is lower than the preset threshold value and the zero-crossing signal indicates that the alternating current is at a zero-crossing point. The integrating circuit 122 is used for integrating the square wave signal to generate an integrated signal. The output circuit 123 is provided with a first input terminal and a power output terminal, and is configured to control the first input terminal and the power output terminal to be turned on based on the integral signal, so as to output a power signal at the power output terminal.
As shown in fig. 3, the temperature detection circuit 110 and the zero-crossing detection circuit 140 are respectively connected to the second input terminal and the third input terminal of the main control circuit 121 to input the temperature signal and the zero-crossing signal to the main control circuit 121. Illustratively, the master control circuit 121 may be implemented by a logic circuit built up by electronic elements such as a comparator, a nand gate, and the like. The main control circuit 121 may perform analog-to-digital conversion on the temperature signal, and convert the temperature signal into a current temperature value. When the current temperature value is lower than the preset threshold value and the zero-crossing signal indicates that the alternating current is at the zero-crossing point, the output end of the main control circuit 121 may output a square wave signal to the integrating circuit 122. The square wave signal may be an electrical signal having a voltage of 5 volts and a frequency of 1000 hertz, for example. It will be appreciated that the parameters of the square wave signal may be specifically set as desired. The integration circuit 122 is used for integrating the square wave signal, and may convert the square wave signal into, for example, a sawtooth wave signal or a triangular wave signal as an integration signal. The voltage values of the integrated signals are all non-negative numbers. The integrating circuit has the functions of reducing the variable quantity, highlighting the invariant quantity and the like. Under the control of the integrated signal, the first input terminal and the power output terminal of the output circuit 123 may be turned on, and the power signal is output at the power output terminal. The power signal may be a dc signal output by the first dc power supply. As described above, after the main control circuit 121 receives the temperature signal and converts the temperature signal into the current temperature value, if the current temperature value is equal to or higher than the preset threshold, the square wave signal is not output to the integrating circuit 122. The power supply output of the output circuit 123 therefore no longer outputs the power supply signal. Therefore, the main control circuit 121 is controlled by the zero crossing signal and the temperature signal to output the square wave signal.
It is to be understood that the third input terminal for connecting the zero-crossing detection circuit 140 is provided on the main control circuit 121 shown in fig. 3, but it is not necessary. When the zero-cross detection circuit 140 is not provided in the heating control circuit 100, the main control circuit 121 may be provided with only the second input terminal, and is not provided with the third input terminal. In this case, the main control circuit 121 outputs a square wave signal as long as the temperature signal output by the temperature detection circuit 110 indicates that the current temperature is lower than the preset threshold.
The gate circuit 120 having the above circuit configuration can output the power supply signal with less disturbance to the heating circuit 130 more accurately and more appropriately. Thereby, the accuracy of the control of the heating circuit 130 is improved.
Although it is explained above that the master control circuit 121 is implemented as a logic circuit, it is understood that the master control circuit 121 may alternatively be implemented as a chip. The chip is also provided with a fourth input end for connecting a second direct current power supply. The second direct current power supply is used for supplying power to the chip. The second dc power source may be, for example, a 5 volt dc power supply. The operation principle of the main control circuit 121 has been described in detail in the foregoing embodiments, and is not described herein for brevity.
The control function of the main control circuit 121 is realized by using a chip, so that the use of electronic components can be reduced, the circuit is simplified, the system integration level is improved, and the circuit fault probability is reduced.
As shown in fig. 3, the integrating circuit 122 includes a second resistor R2, a second capacitor C2, and a first diode D1, which are connected in series. The anode of the first diode D1 is connected to the second capacitor C2, and the cathode of the first diode D1 is connected to the output circuit 123. The integrator circuit 122 receives the square wave signal, and starts to charge the second capacitor C2. The capacitor has the characteristics of alternating current passing and direct current blocking. Specifically, as time passes, the charging voltage gradually increases, and the charging current gradually decreases. When the second capacitor C2 is fully charged, the voltage across it reaches a maximum value, but the charging current is substantially zero. For direct current, the second capacitor C2 may then be equivalent to an open circuit. After that, the second capacitor C2 starts to discharge. In other words, integrating circuit 122, in addition to functioning to transform waveforms in gating circuit 120, also functions to delay the time for subsequent circuits. This reduces the likelihood that, upon power-up, gating circuit 120 will output a power signal to heating circuit 130 under the control of the zero-crossing signal and the temperature signal. In addition, the first diode D1 arranged in the integration circuit 122 can effectively prevent the current of the subsequent circuit from flowing back to the integration circuit 122 and the main control circuit 121 by utilizing the one-way conductivity of the diode, thereby reducing the power consumption.
Illustratively, the anode of the first diode D1 is also connected to the cathode of the second diode D2, and the anode of the second diode D2 is grounded. A second diode D2 may be used to discharge the second capacitor C2. After the second capacitor C2 is charged, pin 1 is positive and pin 2 is negative. At the time of the low level of the square wave signal, the pin 1 of the second capacitor C2 is discharged through the second resistor R2, the main control circuit 121 and the second diode D2. It will be appreciated that only a zero charge capacitance can pass an ac signal. It is therefore desirable to ensure that at the high time of the square wave signal, there is a low level on the second capacitor C2. Thus, the provision of the second diode D2 better ensures that the square wave signal can pass through the second capacitor C2 unimpeded.
Illustratively, the output circuit 123 includes an NPN-type switching transistor. The base of the NPN switching transistor is connected to the integrating circuit 122. The collector of the NPN switching transistor is provided as a first input terminal for connection to a 12V first dc power supply, as shown in fig. 3. And an emitter of the NPN type switching triode is arranged as a power supply output end. Generally, the conduction and the cut-off of the triode can be controlled by controlling the base voltage of the triode. In this scheme, the integration circuit 122 outputs an integration signal to the base of the NPN type switching transistor, the voltage of which is non-negative as described above. Therefore, the NPN-type switching transistor can be turned on under the control of the integration signal. After the transistor is turned on, the emitter of the NPN-type switching transistor serves as a power output terminal of the output circuit 123 to output a power signal.
As can be seen from the above solution, the output circuit 123 is used to enable the first dc power supply to output the power signal through the power output terminal under the control of the aforementioned integration signal. In this scheme, the above process can be implemented with one switching circuit. Compared with a common mechanical switch, the electronic switch formed by the NPN type switching triode has the advantages of small volume, no mechanical contact, high switching speed, convenience for electric signal control and the like. Therefore, the heating control circuit 100 has strong control accuracy and small volume.
Illustratively, the integrating circuit 122 and the output circuit 123 are connected via a stabilizing circuit 124.
The voltage stabilizing circuit 124 is configured to ensure that the integrated signal received by the output circuit 123 is stable. Based on the stabilized integrated signal, the output circuit 123 can better control the output of the power supply signal. And further effectively avoids accidents such as subsequent circuit faults and the like caused by the interference of the integral signal or errors generated by other conditions.
As shown in FIG. 3, the stabilizing circuit 124 includes a first capacitor C1 and a first resistor R1. The first capacitor C1 is used for voltage stabilizing filtering. A first terminal of the first resistor R1 is connected to the output terminal of the integrating circuit 122 and to ground via a first capacitor C1. A second terminal of the first resistor R1 is connected to an input terminal of the output circuit 123. The first resistor R1 is a base current limiting resistor of the NPN-type switching transistor in the output circuit 123, and also determines the discharging speed of the first capacitor C1. It is understood that the product RC of the resistance value of the resistor and the capacitance value of the capacitor is taken as a time constant. The charging and discharging speeds of the capacitor are related to this constant. Generally, R1 is equal to or more than (3 to 5 times) T11/2, wherein T1The period of the square wave signal.
The values of R1 and C1 can be adjusted according to the requirement, so that not only the charging and discharging speed of the first capacitor C1 can be controlled, but also the on/off speed of the output circuit (NPN type switching transistor) can be controlled. Therefore, the scheme not only improves the control accuracy of the heating control circuit 100, but also improves the application range of the heating control circuit 100.
Fig. 4 shows a schematic diagram of a zero crossing detection circuit 140 in the heating control circuit 100 according to an exemplary embodiment of the present invention. As shown in fig. 4, the zero-cross detection circuit 140 includes a charging circuit 141 and a discharging circuit 142. The discharge circuit 142 includes: the PNP type switching triode Q2, a third capacitor C3, a third diode D3, a third resistor R3, a fourth resistor R4 and an optical coupling element U1. The first terminal and the second terminal of the third resistor R3 are connected to the first terminal and the second terminal of the charging circuit 141, respectively. An emitter of the PNP switching transistor Q2 is connected to a first terminal of a third resistor R3 through a third diode D3. The base of the PNP switching transistor Q2 is connected to the first terminal of the third resistor R3. The collector of the PNP switching transistor Q2 is connected to the first end of the optocoupler U1 via a fourth resistor R4. A first terminal of the third capacitor C3 is connected to an emitter of a PNP switching transistor Q2. A second terminal of the third capacitor C3 and a second terminal of the optocoupler U1 are both connected to a second terminal of the third resistor R3.
The charging circuit 141 includes: a fourth diode D4 and a fifth resistor R5. The cathode of the fourth diode D4 is connected to the input neutral line of the ac power supply. An anode of the fourth diode D4 is connected to the second terminal of the third resistor R3. A first end of the fifth resistor R5 is connected to the input hot wire of the ac power source. The second end of the fifth resistor R5 is connected to the first end of the third resistor R3.
Illustratively, the ac power source may be a power source having an effective voltage of 220 volts, a frequency of 50 hertz, and an initial phase angle of 0 degrees. It is understood that the charging circuit 141 and the discharging circuit 142 are relative to the third capacitor C3 in the zero-crossing detection circuit 140. The third resistor R3 forms one branch of the discharge circuit 142, and the other components in the discharge circuit 142 form the other branch. The two branches are connected in parallel across the charging circuit 141.
Alternatively, the resistances of the fifth resistor R5 and the third resistor R3 are reasonably set, so that the fifth resistor R5 can be more ideally divided into voltage by the third resistor R3. Illustratively, the resistance of the fifth resistor R5 is set to 60 kilo-ohms and the resistance of the third resistor R3 is set to 4.7 kilo-ohms. When the alternating current of the alternating current power supply is in the positive direction and the third capacitor C3 is in a charging state, the voltage V at the two ends of the third capacitor C3C3＝VR3-VD3ON. Wherein, VR3Represents the voltage, V, across the third resistor R3D3ONIndicating the voltage across the third diode D3 when in the on state. Thus, in the above example, V is charged by the charging circuit 112 after the third capacitor C3 is charged for a whileR3And VC3Is a difference of VD3ONAnd is approximately 0.7 volts. In the charging process, for the PNP switching transistor Q2, the voltage of the collector is always lower than that of the base, and the PNP switching transistor Q2 is in an off state, so that the triggering event of the optocoupler element U1 is not caused.
Illustratively, in the discharge circuit 142, by properly setting the electrical parameters of the various elements therein, the discharge period of the third capacitor C3 can be made much longer than T of the period of the ac power source2/2, wherein T2The period of the ac power source. For the aforementioned 50 hz ac power source, the cycle time is 20 ms. Specifically, in the discharge circuit 142, based on the discharge characteristic of the RC circuit, the discharge constant of the RC circuit is made larger than T by using the third resistor R3 and the fourth resistor R42/2. After the voltage of the ac power supply drops to zero, the voltage across the third capacitor C3 remains relatively stable. V is caused by the clamping action of PN junction of PNP type switching diodeR3And VC3The difference in (c) stabilized at about 0.7 volts.
At the zero-crossing moment of the alternating-current power supply, when the voltage of the collector of the PNP type switching diode is 0.7V higher than the voltage of the base of the PNP type switching diode, the PNP type switching diode is effectively conducted, the optical coupling element U1 is triggered, and zero-crossing detection is achieved.
The zero-crossing detection circuit 140 utilizes the discharge characteristic of the RC circuit more reasonably, so that the voltage across the third capacitor C3 is maintained at a relatively stable voltage, and the condition that the conducting voltage of the optocoupler element U1 is reduced and the rising edge generates delay due to the too fast discharge of the third capacitor C3 is avoided. Therefore, the accuracy of the zero-crossing detection result is ensured. In addition, the fourth diode D4 can more ideally utilize its one-way conductivity to realize the function of cutting off, and the fifth resistor R5 can realize more reasonable voltage division, further guarantee the accuracy of zero crossing detection. Thereby, system interference is reduced.
As shown in fig. 4, the third terminal of the optical coupler U1 is connected to the third input terminal of the gate circuit 120 and to the third dc power source via the sixth resistor R6. The fourth end of the optical coupling element U1 is grounded. The third terminal of the optical coupler element U1 and the fourth terminal of the optical coupler element U1 are also connected via a fourth capacitor C4.
It can be understood that when the sixth resistor R6 and the fourth capacitor C4 have a connection relationship as shown in fig. 4, they form an RC low pass filter circuit. The RC low-pass filter circuit has the function of preventing signals with the signal frequency higher than the cut-off frequency from passing through and allowing signals with the signal frequency lower than the cut-off frequency to pass through. The cut-off frequency is related to the values of R6 and C4. Different cut-off frequencies can be obtained by varying the values of R6 and C4. Therefore, the interference in the signal can be effectively removed, and the error of the output zero-crossing signal is reduced.
Fig. 5 shows a schematic diagram of the temperature detection circuit 110 in the heating control circuit 100 according to an exemplary embodiment of the present invention. As shown in fig. 5, the temperature detection circuit 110 is a thermocouple detection circuit. The thermocouple detection circuit includes an operational amplifier 111, a non-inverting input circuit 113, an inverting input circuit 112, and an operational amplifier output circuit 114 that are connected to a non-inverting input terminal, an inverting input terminal, and an output terminal of the operational amplifier 111, respectively. Wherein the non-inverting input circuit 113 includes a thermocouple. The inverting input terminal and the output terminal of the operational amplifier 111 are connected via an eleventh resistor R11.
According to the temperature measurement principle of the thermocouple, generally, the potential difference between the hot end and the cold end of the thermocouple is increased or reduced in a certain proportion at different temperatures. The change in potential difference of the thermocouple is extremely small, typically in the order of millivolts. Therefore, to output a usable temperature signal to the gate circuit 120, the potential difference may be amplified through the operational amplifier 111. In this embodiment, the connection between the inverting input terminal and the output terminal of the operational amplifier 111 via the eleventh resistor R11 also means that the temperature detecting circuit 110 is an inverting proportional operational circuit.
In this embodiment, a thermocouple is used as a means for temperature detection. The thermocouple has the advantages of high measurement accuracy, wide range, long service life and the like. The temperature detection circuit 110 having the above-described circuit configuration may output an amplified temperature signal, so that the gate circuit 120 controls the heating operation of the heating circuit 130 based on the temperature signal. In addition, a virtual ground exists in the inverse proportion operation circuit, so that the stability of the temperature detection circuit 110 during operation is ensured, and the heating circuit is controlled to heat when heating is really needed.
As shown in fig. 5, the positive electrode of the thermocouple is connected to the non-inverting input terminal via a seventh resistor R7. The cathode of the thermocouple is connected to the center point of the first resistor divider 1131. The first terminal of the first resistor divider 1131 is used to connect to a fourth dc power source. The second terminal of the first resistor divider 1131 is connected to ground. The inverting input circuit 112 includes an eighth resistor R8. A first terminal of the eighth resistor R8 is connected to the inverting input terminal. A second terminal of the eighth resistor R8 is connected to a center point of the second resistor divider 1121. A first terminal of the second resistor divider 1121 is used for connecting to a fifth dc power source via a ninth resistor R9. A second terminal of the second resistive divider 1121 is connected to ground. A fifth diode D5 is connected between the first terminal and the second terminal of the second resistive divider 1121 in parallel with the second resistive divider 1121.
It can be understood that the hot end of the thermocouple, i.e. the temperature measuring end, can be set at a preset point to be measured. The cold end of the thermocouple is typically disposed on a printed circuit board. In general, as the heating circuit 130 heats or changes the environment, not only the temperature of the hot end of the thermocouple increases rapidly, but also the temperature of the cold end of the thermocouple increases, which eventually causes the potential difference of the thermocouple to drift. The temperature drift can be suppressed using the above-described circuit. The input voltage V of the non-inverting input terminal of the operational amplifier 111 can be calculated according to the connection mode of the circuit3. Examples of the inventionThe fourth dc power source may be, for example, a dc power source having a voltage of 5 volts. V3＝VThermocouple+5V × R13/(R12+ R13), wherein V isThermocouple＝VHot end-VCold end. Illustratively, a type K thermocouple is used as an example, and the cold end of the thermocouple is set in an environment of 0 degrees celsius, and the hot end of the thermocouple is used for contacting a measured object. If the object to be measured is boiled water, the temperature is 100 ℃. A potential difference of 4.096 millivolts is created between the hot and cold sides. According to the K-type thermocouple graduation table, the temperature difference at the moment can be correspondingly obtained by looking up a table and is 100 ℃. However, in practical use, the cold end of the thermocouple is in a changing environment, and the temperature of the cold end is difficult to be kept constant at 0 ℃. The cold side was placed in a 30 c environment and the hot side was also placed in boiling water, showing that the potential difference between the hot and cold sides was 2.893 mv. And checking a K-type thermocouple graduation table to obtain that the temperature difference is 71 ℃ and 29 ℃ different from the actual 100 ℃. Therefore, the cold side needs to compensate for this 29 degree Celsius temperature difference, i.e., 1.203 millivolts. As can be seen from the actual measurement data, the potential difference V of the thermocouple increases with the rise of the ambient temperatureThermocoupleAs compared to 0 degrees celsius. For example, V measured at an ambient temperature of T50 degrees celsiusThermocoupleIs a VTInevitably has VTLess than 4.095 millivolts, the difference is 4.095-VT. The output voltage V of the output terminal of the operational amplifier 111 can be calculated according to the circuit structure1＝(V3-V2) R11/R8. As described above, V3Decrease (4.095-V)T) Millivolts, therefore, correspondingly, V2Should also be reduced (4.095-V)T) Millivolts.
Illustratively, the reduction in V may be achieved using a characteristic of diode temperature and tube voltage drop2This is the purpose. Thus, the fifth diode D5 is provided in the inverting input circuit 112. Specifically, the diode's tube drop varies with temperature by-2 millivolts per degree celsius, i.e., the tube drop decreases by 2 millivolts per 1 degree celsius increase in temperature. The tube drop decreases by 100 mv from 0 c up to 50 c. In this scheme, V3Only decrease (4.095-V)T) Millivolts, so the tube voltage drop of the fifth diode D5 is reduced by 100/(4.095-V)T) Doubling the weight. Meanwhile, the fifth diode D5 is connected in parallel with the second resistor divider 1121, i.e., the sum of the voltages of R14 and R15 is equal to the tube voltage drop V of the fifth diode D5on. Thus, the input voltage V of the inverting input terminal of the operational amplifier 111 can be calculated2＝VonR15/(R14+ R15). That is, the value of the resistance in the second resistive divider 1121 should satisfy: R15/(R14+ R15) is 100/(4.095-V)T). The main functions of the operational amplifier 111 are to amplify the differential mode, reject the common mode, and also have the characteristics of virtual short and virtual break. From this characteristic, the output voltage V of the output terminal of the operational amplifier 111 can be calculated1。V1＝(V3-V2) R11/R8. It will be appreciated that adjusting the resistance values of R11 and R8 adjusts the amplification of operational amplifier 111 such that V1Varying between 0-5 volts. Finally, the temperature signal is outputted to the main control circuit 121 via the operational amplifier output circuit 114.
In the above-described embodiment, the temperature detection circuit 110 uses fewer components and has a relatively simple circuit configuration. The seventh resistor R7 is configured to perform impedance matching so that all signals can be transmitted to the non-inverting input of the operational amplifier 111, and almost no signals are reflected back to the thermocouple and/or the first resistor divider 1131, thereby improving energy efficiency. The influence of temperature drift generated in the process of detecting the temperature by the thermocouple can be eliminated only by arranging the fifth diode D5 in the inverting input circuit. Therefore, the temperature detection circuit 110 including such simple components can detect the heating temperature and output a relatively accurate temperature signal, and the gate circuit 120 can precisely control the heating operation of the heating circuit 130.
Illustratively, the op-amp output circuit 114 includes a tenth resistor R10 and a fifth capacitor C5. A first terminal of the tenth resistor R10 is connected to the output terminal of the operational amplifier 111. A second terminal of the tenth resistor R10 is connected to the second input terminal of the gating circuit 120 and to ground via a fifth capacitor C5.
Similar to the zero-crossing detection circuit, the tenth resistor R10 and the fifth capacitor C5 in the operational amplifier output circuit 114 also form an RC low-pass filter circuit. As described above, the RC low-pass filter circuit functions to block signals having a signal frequency higher than the cutoff frequency from passing and to allow signals having a signal frequency lower than the cutoff frequency to pass. In this circuit, the cut-off frequency is related to the values of R10 and C5. Different cut-off frequencies can be obtained by varying the values of R10 and C5. Therefore, the interference in the signals can be effectively removed, more accurate temperature signals can be obtained, and further more accurate power signals with more accurate control effect can be obtained.
Illustratively, the power input first terminal of the operational amplifier 111 is connected to ground. The second terminal of the power supply input of the operational amplifier 111 is used for connecting the sixth direct current power supply and is also connected to the ground via the seventh capacitor C7.
It will be appreciated that all dc power supplies mentioned above except the first dc power supply may be implemented using the same power supply. The drawings are distinguished so as to be more clearly apparent. Low voltage power supplies often have interference ripple. Typically the voltage magnitude of the ripple is between tens of millivolts and tens of millivolts. According to the above scheme, the potential difference of the thermocouple is also in the millivolt level.
Therefore, the seventh capacitor C7 is provided to effectively filter the interference ripple, so that the temperature signal output by the operational amplifier 111 via the operational amplifier output circuit 114 is more accurate and has less error.
Illustratively, a sixth capacitor C6 is connected between the non-inverting input terminal and the inverting input terminal. As described above, the inverting input circuit 112 and the non-inverting input circuit 113 are both connected to a dc power supply. However, the non-inverting input and the inverting input of the operational amplifier may simultaneously receive the interference ripple in the dc power supply. The interference ripple is not amplified according to the characteristic that the operational amplifier 111 can suppress the common mode signal. That is, the operational amplifier 111 amplifies only the desired signal, i.e., the potential difference of the thermocouple. The sixth capacitor C6 is provided between the non-inverting input terminal and the inverting input terminal to filter out signal interference other than interference ripple in the dc power supply.
According to an aspect of the present invention, an electrical appliance is provided. The appliance includes a heating control circuit 100 as described above and a heating circuit 130 connected to the heating control circuit 100. Illustratively, the appliance may be a steamer. When the user uses the electric appliance, the heating control circuit 100 can be used to control the heating condition of the heating circuit 130. The control process of the heating control circuit 100 is as described above and will not be described herein.
The electric appliance provided with the heating control circuit 100 can effectively avoid the situations that the electric appliance is heated immediately after being electrified, and the like, thereby ensuring the use safety of the electric appliance and ensuring the personal safety of users. In addition, the heating control circuit 100 of the electric appliance is not provided with a high-power electric device such as a relay, so that the use cost of a user is reduced.
Illustratively, the chassis of the appliance is made of black crystal. Although the normal heating temperature of the black crystal furnace is as high as 600-700 ℃, the heating control circuit 100 can normally measure the temperature and further normally control the heating. Therefore, the heating control requirement of the electric appliance is met.
For purposes of description, the term "connected" may be used herein to describe one or more elements or features shown in a figure in relation to other elements or features. It should be understood that "connected" may include directly connected or indirectly connected via other elements or features, all of which are intended to be encompassed herein.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, elements, components, and/or combinations thereof, unless the context clearly indicates otherwise.
It should be noted that the terms "first," "second," and the like in the description and claims of this application and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are capable of operation in sequences other than those illustrated or described herein.
The present invention has been described in terms of the above embodiments, but it is to be understood that the above embodiments are for purposes of illustration and description only and are not intended to limit the invention to the described embodiments. Furthermore, it will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that many more modifications and variations are possible in light of the teaching of the present invention and are within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (18)
1. A heating control circuit comprises a temperature detection circuit and is characterized by also comprising a gating circuit;
the temperature detection circuit is used for generating a temperature signal;
the first input end of the gating circuit is used for being connected with a first direct current power supply, the second input end of the gating circuit is connected with the temperature detection circuit, the power output end of the gating circuit is used for being connected with the heating circuit, and the gating circuit is used for outputting a power signal to the heating circuit at the power output end when the temperature signal indicates that the current temperature is lower than a preset threshold value;
the gating circuit comprises a main control circuit, an integrating circuit and an output circuit which are connected in sequence;
the main control circuit is provided with the second input end and is used for outputting a square wave signal when the temperature signal indicates that the current temperature is lower than a preset threshold value;
the integration circuit is used for integrating the square wave signal to generate an integrated signal;
the output circuit is provided with the first input end and the power output end and is used for controlling the conduction of the first input end and the power output end based on the integral signal so as to output the power signal at the power output end.
2. The heating control circuit according to claim 1, wherein the integration circuit and the output circuit are connected via a voltage stabilizing circuit.
3. The heating control circuit of claim 2, wherein the voltage regulator circuit comprises a first capacitor and a first resistor, a first end of the first resistor is connected to the output terminal of the integrator circuit and grounded via the first capacitor, and a second end of the first resistor is connected to the input terminal of the output circuit.
4. The heating control circuit of claim 1, wherein the integration circuit comprises a second resistor, a second capacitor, and a first diode connected in series, wherein an anode of the first diode is connected to the second capacitor and a cathode of the first diode is connected to the output circuit.
5. The heating control circuit of claim 4, wherein the anode of the first diode is further connected to the cathode of a second diode, and the anode of the second diode is grounded.
6. A heating control circuit according to claim 1, wherein the master control circuit is implemented as a chip, said chip further being provided with a fourth input for connection to a second dc power supply.
7. The heating control circuit of claim 1, wherein the output circuit comprises an NPN switching transistor, a base of the NPN switching transistor is connected to the integrating circuit, a collector of the NPN switching transistor is configured as the first input terminal, and an emitter of the NPN switching transistor is configured as the power output terminal.
8. The heating control circuit according to claim 1, further comprising a zero-crossing detection circuit for connecting an ac power source and detecting a zero-crossing of the ac power output by the ac power source to generate a zero-crossing signal;
the third input end of the gating circuit is connected with the zero-crossing detection circuit, and the gating circuit is used for outputting a power supply signal to the heating circuit at the power supply output end when the temperature signal indicates that the current temperature is lower than a preset threshold value and the zero-crossing signal indicates that the alternating current is at a zero-crossing point.
9. The heating control circuit of claim 8, wherein the zero-crossing detection circuit comprises a charging circuit and a discharging circuit;
the discharge circuit includes: PNP type switch triode, third electric capacity, third diode, third resistance, fourth resistance and opto-coupler element, the first end and the second end of third resistance are connected respectively charging circuit's first end and second end, the projecting pole warp of PNP type switch triode the third diode is connected the first end of third resistance, PNP type switch triode's base is connected the first end of third resistance, PNP type switch triode's collecting electrode warp fourth ohmic connection the first end of opto-coupler element, the first end of third electric capacity is connected the projecting pole of PNP type switch triode, the second end of third electric capacity with the second end of opto-coupler element all is connected to the second end of third resistance.
10. The heating control circuit of claim 9, wherein the charging circuit comprises: a fourth diode and a fifth resistor; the cathode of the fourth diode is connected with the input zero line of the alternating current power supply, and the anode of the fourth diode is connected with the second end of the third resistor; the first end of the fifth resistor is connected with the input live wire of the alternating current power supply, and the second end of the fifth resistor is connected with the first end of the third resistor.
11. The heating control circuit of claim 9, wherein a third terminal of the optical coupler element is connected to a third input terminal of the gating circuit and is configured to be connected to a third dc power source via a sixth resistor, a fourth terminal of the optical coupler element is grounded, and the third terminal of the optical coupler element and the fourth terminal of the optical coupler element are further connected via a fourth capacitor.
12. The heating control circuit according to claim 1, wherein the temperature detection circuit is a thermocouple detection circuit, the thermocouple detection circuit includes an operational amplifier, a non-inverting input circuit, an inverting input circuit, and an operational amplifier output circuit, which are respectively connected to a non-inverting input terminal, an inverting input terminal, and an output terminal of the operational amplifier, wherein the non-inverting input circuit includes a thermocouple, and the inverting input terminal and the output terminal of the operational amplifier are connected via an eleventh resistor.
13. The heating control circuit of claim 12,
the positive electrode of the thermocouple is connected with the non-inverting input end through a seventh resistor, the negative electrode of the thermocouple is connected with the central point of a first resistor voltage divider, the first end of the first resistor voltage divider is used for being connected with a fourth direct-current power supply, and the second end of the first resistor voltage divider is grounded;
the inverting input circuit comprises an eighth resistor, wherein a first end of the eighth resistor is connected with the inverting input end, and a second end of the eighth resistor is connected to the central point of the second resistor divider; the first end of the second resistor voltage divider is used for being connected with a fifth direct current power supply through a ninth resistor, and the second end of the second resistor voltage divider is grounded; and a fifth diode connected with the second resistor divider in parallel is connected between the first end and the second end of the second resistor divider.
14. The heating control circuit of claim 12,
the operational amplifier output circuit comprises a tenth resistor and a fifth capacitor, wherein a first end of the tenth resistor is connected with the output end of the operational amplifier, and a second end of the tenth resistor is connected with the second input end of the gating circuit and is grounded through the fifth capacitor.
15. The heating control circuit according to claim 12, wherein a sixth capacitor is connected between the non-inverting input terminal and the inverting input terminal.
16. The heating control circuit of claim 12, wherein a power input first end of the operational amplifier is connected to ground, and a power input second end of the operational amplifier is used for connecting a sixth dc power supply and is also connected to ground via a seventh capacitor.
17. An electrical appliance comprising a heating control circuit according to any one of claims 1 to 16 and the heating circuit connected to the heating control circuit.
18. The appliance according to claim 17, characterized in that the appliance is a steamer.
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| CN202120386466.5U CN214627391U (en) | 2021-02-20 | 2021-02-20 | Heating control circuit and electric appliance |
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| CN202120386466.5U CN214627391U (en) | 2021-02-20 | 2021-02-20 | Heating control circuit and electric appliance |
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