On-off signal acquisition circuit of temperature controller with parallel electric auxiliary heating resistor

Abstract

The invention discloses an on-off signal acquisition circuit of a temperature controller with parallel electric auxiliary heating resistors, and belongs to the technical field of frequency conversion control. Comprising a variable-frequency controller and a temperature controller with a parallel electric auxiliary heating resistor, a phase line L of a single-phase alternating-current power supply is connected with one end of the temperature controller with the parallel electric auxiliary heating resistor and a phase line input end LI of the variable-frequency controller, and the other end of the temperature controller with the parallel electric auxiliary heating resistor is connected with a temperature controller input end T of the variable-frequency controller. A capacitor C is connected between a temperature controller input end T and a null line input end NI of the variable frequency controller, one end of an optocoupler PC input side in the variable frequency controller is connected with the temperature controller input end T of the variable frequency controller, the other end of the optocoupler PC input side is connected with one end of a diode D, the other end of the diode D is connected with one end of a current limiting resistor R, and the other end of the current limiting resistor R is connected with the other end of a resistor R. And the other end of the current-limiting resistor R is connected with the phase line input end LI of the variable frequency controller. The temperature controller has the advantages that a fixed-frequency refrigerating system of a refrigerating appliance adopting the temperature controller can be possibly upgraded and transformed into a variable-frequency refrigerating system.

Description

Technical Field

[0001] The present invention belongs to the field of variable frequency control technology, and specifically relates to an on-off signal acquisition circuit for a thermostat with a parallel electric auxiliary heating resistor. The circuit is mainly used for refrigeration appliances using such a thermostat and a variable frequency controller to control the operation of the compressor according to the on-off signal. Background Art

[0002] Traditional household refrigerators, commercial freezers and other refrigeration appliances, when powered by a single-phase AC power supply, are mostly controlled by a thermostat to control a refrigeration compressor driven by a single-phase induction AC motor. The basic principle is as follows: Figure 1 shown. Figure 1 In the example, a single-phase AC power source 10 supplies power to a single-phase induction motor 60 within the refrigeration compressor through a thermostat 50, driving the motor. The thermostat 50 primarily comprises a temperature control switch K. When the temperature at the thermostat 50 location is higher than a set temperature, the switch K turns on, completing the circuit and energizing the single-phase induction motor 60 that drives the refrigeration compressor. Conversely, when the temperature falls below the set temperature, the switch K turns off, depriving the motor 60 of power and causing it to cease operation.

[0003] With the development of technology, the application of variable frequency compressors is becoming more and more extensive. Variable frequency technology has brought huge performance improvements to refrigeration appliances. Manufacturers urgently need to transform and upgrade existing fixed-frequency refrigeration systems to variable frequency refrigeration systems at the lowest cost, and bring the technological dividends brought by variable frequency technology to consumers.

[0004] The most commonly used frequency conversion transformation method is to make minimal design changes to the existing fixed-frequency refrigeration system and replace the fixed-frequency refrigeration compressor with a variable-frequency compressor controlled by a variable-frequency control system; at the same time, directly use the thermostat of the existing fixed-frequency refrigeration system to allow the variable-frequency controller to obtain its on-off signal to control the operation and stop of the variable-frequency compressor; when the thermostat is on, the compressor is controlled to run, and when the thermostat is off, the compressor is controlled to stop running. In order to better reflect the superiority of the variable-frequency compressor, the variable-frequency controller is generally maintained in the power-on state, so that the on-off time of each thermostat can be recorded, and based on this, the speed of the variable-frequency compressor during each operation can be optimized. Figure 2As shown, a single-phase AC power source 10 is connected to the power input of the variable frequency controller 30 to supply power to the variable frequency controller 30. The phase line L of the single-phase AC power source 10 is connected to the temperature control switch K in the thermostat 50, and then to the thermostat input T of the variable frequency controller 30. The thermostat input T passes through the input side of the optocoupler PC, a diode D and a current-limiting resistor R, and is connected to the neutral line input terminal NI at the power input of the variable frequency controller 30. When the thermostat 50 is on, a unidirectional pulsating current will flow through the input side of the optocoupler PC on the variable frequency controller 30. Conversely, when the thermostat 50 is off, no current will flow through the input side of the optocoupler PC. As a result, the on / off signal of the thermostat 50 can be detected at the output side of the optocoupler PC. This signal is connected to the main control circuit 31 of the variable frequency controller 30 and is used to optimize the operation of the compressor motor 40.

[0005] The refrigeration system controlled by the thermostat described above works well in most cases. However, in some low temperature scenarios, some types of thermostats may fail to connect the contacts. The reason is that at these low temperatures, the deformation of the temperature control deformable material in the thermostat cannot reach the level required to connect the contacts. In this case, a thermostat 20 with a parallel electric auxiliary heating resistor is required, such as Figure 3 As shown, this type of thermostat 20 with a parallel electric auxiliary heating resistor has an electric auxiliary heating resistor Rh connected between the contacts of its temperature control switch K, where it is connected in parallel with the temperature control switch K. When the temperature of the thermostat 20 with the parallel electric auxiliary heating resistor is higher than the set temperature, the temperature control switch K is closed, and the electric auxiliary heating resistor Rh is short-circuited and has no effect. When the temperature of the thermostat 20 with the parallel electric auxiliary heating resistor is lower than the set temperature, the temperature control switch K is open. At this time, the electric auxiliary heating resistor Rh is connected in series in the circuit, generating heat through a weak current, while ensuring that the load compressor does not enter the operating state and preventing the temperature of the thermostat 20 with the parallel electric auxiliary heating resistor from being too low to affect normal operation. This function is implemented in the "A Thermostat" described in Chinese Utility Model Patent Authorization Publication No. CN2310334Y and the "Switch Assembly for a Fixed Temperature Reset Thermostat" disclosed in Chinese Utility Model Patent Authorization Publication No. CN205015763U.

[0006] Such a thermostat with a parallel electric auxiliary heating resistor solves the problem that the thermostat cannot work properly at low temperatures. However, this technology also brings difficulties to the upgrade of fixed frequency refrigeration system to variable frequency refrigeration system. Figure 4The figure shows a frequency conversion modification method for a refrigeration system with a thermostat without an electric auxiliary heating resistor. When the temperature of the thermostat 20 with a parallel electric auxiliary heating resistor reaches the set temperature and its temperature control switch K is disconnected, the electric auxiliary heating resistor Rh replaces the temperature control switch K and is connected to the circuit. As a result, the circuit where the thermostat 20 with the parallel electric auxiliary heating resistor is located is not completely disconnected.

[0007] For a rated power supply voltage of 220-240V, the current-limiting resistor R on the variable frequency controller is typically around 100-150kΩ to ensure a suitable operating current at the optocoupler PC input side. The resistance of the auxiliary heating resistor Rh is typically around 50kΩ to achieve a heating power of 0.5-1W at the rated voltage (these are typical values; specific values may vary depending on the system). Thus, when the thermostat's temperature control switch is in the on and off states, the thermostat circuit resistance is 100-150kΩ and 150-200kΩ, respectively. The difference in circuit resistance between these two states is small, resulting in only a small change in the current at the optocoupler PC input side of the circuit. This change is sometimes less than the change caused by power supply voltage fluctuations, insufficient to discern the optocoupler PC's conduction status (e.g., the difference between conduction and non-conduction), making it unsuitable for upgrading fixed-frequency cooling systems to variable-frequency cooling systems.

[0008] When the rated voltage of the power supply is 100~115V, the resistance values of the current limiting resistor R and the electric auxiliary heating resistor Rh will be adjusted with the rated voltage, but the resistance ratio between them is basically the same, because their values are determined according to the appropriate operating current and operating power obtained under the rated voltage and normal voltage fluctuation range, so the same problem also exists.

[0009] In view of the above-mentioned prior art, the applicant has made a useful design, and the technical solution to be introduced below is produced in this context. Summary of the Invention

[0010] The object of the present invention is to provide an on / off signal acquisition circuit for a thermostat with a parallel electric auxiliary heating resistor, so as to make it possible to upgrade a fixed-frequency refrigeration system to a variable-frequency refrigeration system using a refrigeration appliance using such a thermostat.

[0011] The objectives of the present invention are achieved by providing an on / off signal acquisition circuit for a temperature controller with a parallel electric auxiliary heating resistor, comprising a frequency conversion controller and the temperature controller with the parallel electric auxiliary heating resistor. The frequency conversion controller comprises an optocoupler PC, a diode D, a current-limiting resistor R, and a main control circuit. A phase line L of a single-phase AC power supply is connected to one end of the temperature controller with the parallel electric auxiliary heating resistor and a phase line input terminal LI of the frequency conversion controller, respectively. The other end of the temperature controller with the parallel electric auxiliary heating resistor is connected to a temperature controller input terminal T of the frequency conversion controller. A neutral line N of the single-phase AC power supply is connected to a neutral line input terminal NI of the frequency conversion controller. A capacitor C is connected between the temperature controller input terminal T and the neutral line input terminal NI of the frequency conversion controller. One end of the input side of the optocoupler PC in the frequency conversion controller is connected to the temperature controller input terminal T of the frequency conversion controller. The other end of the input side of the optocoupler PC is connected to one end of the diode D. The other end of the diode D is connected to one end of the current-limiting resistor R. The other end of the current-limiting resistor R is connected to the phase line input terminal LI of the frequency conversion controller.

[0012] In a specific embodiment of the present invention, a frequency converter and a temperature controller with a parallel electric auxiliary heating resistor are provided. The frequency converter includes an optocoupler PC, a diode D, a current-limiting resistor R, and a main control circuit. The phase line L of a single-phase AC power supply is respectively connected to one end of the temperature controller with the parallel electric auxiliary heating resistor and the phase line input terminal LI of the frequency converter. The other end of the temperature controller with the parallel electric auxiliary heating resistor is connected to the temperature controller input terminal T of the frequency converter. The neutral line N of the single-phase AC power supply is connected to the neutral line input terminal NI of the frequency converter. The frequency converter is characterized in that a capacitor C is connected between the temperature controller input terminal T and the neutral line input terminal NI. One end of the optocoupler PC input side of the frequency converter is connected to one end of the diode D and the temperature controller input terminal T. The other end of the optocoupler PC input side is connected to the other end of the diode D and one end of the current-limiting resistor R. The other end of the current-limiting resistor R is connected to the phase line input terminal LI of the frequency converter.

[0013] In another specific embodiment of the present invention, the forward signal input terminal of the optocoupler PC in the frequency conversion controller is connected to the temperature controller input terminal T of the frequency conversion controller, the reverse signal input terminal of the optocoupler PC is connected to the anode of the diode D, the cathode of the diode D is connected to one end of the current limiting resistor R, and the other end of the current limiting resistor R is connected to the phase line input terminal LI of the frequency conversion controller.

[0014] In another specific embodiment of the present invention, the reverse signal input terminal of the optocoupler PC in the frequency conversion controller is connected to the temperature controller input terminal T of the frequency conversion controller, the forward signal input terminal of the optocoupler PC is connected to the cathode of the diode D, the anode of the diode D is connected to one end of the current limiting resistor R, and the other end of the current limiting resistor R is connected to the phase line input terminal LI of the frequency conversion controller.

[0015] In another specific embodiment of the present invention, the forward signal input terminal of the optocoupler PC in the frequency conversion controller is connected to the cathode of the diode D and the temperature controller input terminal T, the reverse signal input terminal of the optocoupler PC is connected to the anode of the diode D and one end of the current limiting resistor R, and the other end of the current limiting resistor R is connected to the phase line input terminal LI of the frequency conversion controller.

[0016] In another specific embodiment of the present invention, the reverse signal input terminal of the optocoupler PC in the frequency conversion controller is connected to the anode of the diode D and the temperature controller input terminal T, the forward signal input terminal of the optocoupler PC is connected to the cathode of the diode D and one end of the current limiting resistor R, and the other end of the current limiting resistor R is connected to the phase line input terminal LI of the frequency conversion controller.

[0017] Due to the adoption of the above-mentioned structure, the present invention has the beneficial effect of being able to solve the problem of obtaining the on / off signal of a thermostat with a parallel electric auxiliary thermal resistor. In the prior art, for a thermostat without a parallel electric auxiliary thermal resistor, the thermostat is connected in series to the input side of an optocoupler. When the thermostat is turned on and off, the optocoupler is turned on and off, respectively, and then the on / off signal of the thermostat is obtained at the output side of the optocoupler after optical isolation. However, for a thermostat with a parallel electric auxiliary thermal resistor, since the parallel electric auxiliary thermal resistor is significantly smaller than the current limiting resistor of the thermostat circuit, when the temperature control switch in the thermostat is turned on and off, the parallel electric auxiliary thermal resistor actually exhibits two states, namely, ineffective and effective, respectively. This only brings about a small change in the total resistance of the thermostat circuit and does not produce a sufficiently large difference in the current on the input side of the optocoupler for actually obtaining the on / off signal of the thermostat. Therefore, it can be seen that the prior art cannot effectively identify the on / off state of the temperature control switch in the thermostat. Compared with the above-mentioned existing technologies, in the present invention, when the temperature control switch in the thermostat is turned on and off, the optocoupler input side that actually obtains the thermostat on-off signal shows two states: no current and current. This can reliably identify the on-off state of the thermostat and realize the variable frequency transformation of the refrigeration system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the electrical schematic diagram of a constant-frequency compressor refrigeration system controlled by a thermostat; Figure 2 This is the electrical schematic diagram for the frequency conversion transformation of the refrigeration system controlled by the thermostat; Figure 3 The electrical schematic diagram of a fixed-frequency compressor refrigeration system controlled by a thermostat with a parallel electric auxiliary heating resistor; Figure 4 An electrical schematic diagram of a refrigeration system controlled by a thermostat with a parallel electric auxiliary heating resistor; Figure 5 This is an electrical schematic diagram of an embodiment of the present invention; Figure 6 is an electrical schematic diagram of another embodiment of the present invention; Figure 7 This is an electrical schematic diagram of another embodiment of the present invention; Figure 8 This is an electrical schematic diagram of yet another embodiment of the present invention.

[0019] In the figure: 10. Single-phase AC power supply; 20. Thermostat with parallel electric auxiliary heating resistor; 30. Frequency converter; 31. Main control circuit; 40. Compressor motor; 50. Thermostat; 60. Single-phase induction motor. DETAILED DESCRIPTION

[0020] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the description of the embodiments does not limit the technical solutions. Any changes in form rather than substance based on the concept of the present invention should be considered as the scope of protection of the present invention.

[0021] In the following description, all concepts related to directionality (or orientation) such as up, down, left, right, front and back are with respect to the position state of the figure being described. The purpose is to facilitate public understanding, and therefore it cannot be understood as a special limitation on the technical solution provided by the present invention. Example 1

[0022] See also Figure 5The present invention relates to a circuit for acquiring on / off signals for a thermostat with a parallel electric auxiliary heating resistor. This circuit can reliably acquire the on / off signals of a thermostat with a parallel electric auxiliary heating resistor, enabling frequency conversion upgrades of refrigeration systems. The circuit comprises a frequency conversion controller 30 and a thermostat 20 with a parallel electric auxiliary heating resistor. The frequency conversion controller 30 comprises an optocoupler PC, a diode D, a current-limiting resistor R, and a main control circuit 31. The optocoupler PC comprises a light-emitting diode (LED) as the light-emitting element and a phototransistor as the light-receiving element. The thermostat 20 comprises a temperature control switch K and an electric auxiliary heating resistor Rh connected in parallel. The phase line L and neutral line N of a single-phase AC power source 10 are connected to the phase line input terminal LI and the neutral line input terminal NI of the frequency conversion controller 30, respectively, providing single-phase AC power to the frequency conversion controller 30. The output of the variable frequency controller 30 is connected to the compressor motor 40. The compressor motor 40 can be any asynchronous or synchronous motor that the variable frequency controller can drive, most commonly a permanent magnet synchronous motor (PMSM) or a brushless DC motor (BLDC). The phase line L of the single-phase AC power source 10 is also connected to one end of a thermostat 20 with a parallel electric auxiliary heating resistor. The other end of the thermostat 20 with a parallel electric auxiliary heating resistor is connected to the thermostat input T of the variable frequency controller 30. A capacitor C is connected between the thermostat input T and the neutral input N1 of the variable frequency controller 30. One end of the optocoupler PC input side of the variable frequency controller 30 is connected to the thermostat input T of the variable frequency controller 30. The other end of the optocoupler PC input side is connected to one end of a diode D. The other end of the diode D is connected to one end of a current-limiting resistor R. The other end of the current-limiting resistor R is connected to the phase line input L1 of the variable frequency controller 30. In this embodiment, the temperature controller input terminal T is connected to the forward signal input terminal of the optocoupler PC in the frequency conversion controller 30, and the reverse signal input terminal of the optocoupler PC is connected to the positive electrode of the diode D. That is, the light-emitting diode on the input side of the optocoupler PC and the diode D have the same polarity direction in the series circuit, and the negative electrode of the diode D is connected to one end of the current-limiting resistor R.

[0023] When the temperature of the thermostat 20 with a parallel electric auxiliary heating resistor is higher than the set temperature, the internal temperature control switch K is turned on, and the thermostat input terminal T and the phase line input terminal of the frequency conversion controller 30 are effectively short-circuited. As a result, the two ends of the series circuit formed by the input side of the optocoupler PC, the diode D, and the current-limiting resistor R are effectively connected to the phase line L of the single-phase AC power supply 10 due to the closure and conduction of the temperature control switch K. Since there is no voltage difference between the two ends of this series circuit, no current flows in the circuit. At the same time, the two ends of the capacitor C are effectively connected to the phase line L and the neutral line N of the single-phase AC power supply 10. Considering that the capacitance of the capacitor C is generally no more than 0.5uF, only a small amount of reactive power will be generated, which will basically not affect the actual power consumption of the system efficiency. When the temperature of the thermostat 20 with a parallel electric auxiliary heating resistor falls below the set temperature, its internal temperature control switch K is disconnected. The characteristics of the thermostat 20 with a parallel electric auxiliary heating resistor in the circuit are equivalent to those of an electric auxiliary heating resistor Rh. At this point, the circuit in which the thermostat 20 with a parallel electric auxiliary heating resistor resides is equivalent to being connected in parallel with a series circuit consisting of the input side of an optocoupler PC, a diode D, and a current-limiting resistor R. This circuit, connected in series via a capacitor C, is ultimately connected to the phase line L and neutral line N of a single-phase AC power source 10. By selecting an appropriate resistance value for the current-limiting resistor R and an appropriate capacitance value for the capacitor C, an appropriate conduction current can flow through the input side of the optocoupler PC. Thus, when the thermostat 20 with a parallel electric auxiliary heating resistor is turned on and off, the input side of the optocoupler PC presents two states: no current flowing through it and a conduction current flowing through it, respectively. The output side of the optocoupler PC can reliably obtain an isolated thermostat on / off signal, thus achieving the purpose of the invention. Example 2

[0024] In the present invention, one end of the optocoupler PC input side in the variable frequency controller 30 can also be connected to one end of the diode D and the temperature controller input terminal T, the other end of the optocoupler PC input side is connected to the other end of the diode D and one end of the current limiting resistor R, and the other end of the current limiting resistor R is connected to the phase line input terminal LI of the variable frequency controller 30.

[0025] See also Figure 6 The difference between this embodiment and embodiment 1 is that the forward signal input terminal of the optocoupler PC in the frequency conversion controller 30 is connected to the cathode of the diode D, the reverse signal input terminal of the optocoupler PC is connected to the anode of the diode D and one end of the current limiting resistor R, and the other end of the current limiting resistor R is connected to the phase line input terminal LI of the frequency conversion controller 30.

[0026] In this embodiment, diode D is connected in antiparallel with the LED on the PC input side of the optocoupler. This circuit connection also serves to protect the LED on the PC input side of the optocoupler. As is well known, the LED on the optocoupler input side generally has a very low reverse withstand voltage, typically 5-6V. Any interference signal on the input signal line exceeding this withstand voltage can damage the optocoupler. Therefore, connecting a high-voltage diode in series with the same polarity or connecting a diode in antiparallel can achieve effective protection. The optocoupler protection method in this embodiment differs from that in Example 1, but the operating principles remain the same. Example 3

[0027] See also Figure 7 The difference between this embodiment and embodiment 1 is that the temperature controller input terminal T of the variable frequency controller 30 is connected to the reverse signal input terminal of the optocoupler PC, the forward signal input terminal of the optocoupler PC in the variable frequency controller 30 is connected to the cathode of the diode D, the anode of the diode D is connected to one end of the current limiting resistor R, and the other end of the current limiting resistor R is connected to the phase line input terminal LI of the variable frequency controller 30.

[0028] In this embodiment, the polarity of the input-side light-emitting diode of the optocoupler PC and the diode D in the circuit are opposite to those in Example 1. Since the power supply of the circuit is an AC power supply, the result of the reverse direction of the diode D is that the actual conduction half-cycle in the circuit is replaced. The other working principles are exactly the same as those in Example 1. Example 4

[0029] See also Figure 8 The difference between this embodiment and embodiment 2 is that the reverse signal input terminal of the optocoupler PC in the frequency conversion controller 30 is connected to the anode of the diode D and the temperature controller input terminal T, the forward signal input terminal of the optocoupler PC is connected to the cathode of the diode D and one end of the current limiting resistor R, and the other end of the current limiting resistor R is connected to the phase line input terminal LI of the frequency conversion controller 30.

[0030] In this embodiment, the polarities of the input-side light-emitting diode and diode D of the optocoupler PC in the circuit are opposite to those in Example 2. As a result, the conduction half-cycle and reverse bypass half-cycle of the input side of the optocoupler PC are exactly opposite to those in Example 2. The other working principles are completely consistent with Example 2.

[0031] In the above structure, the choice of capacitor C's capacitance and current-limiting resistor R's resistance determines the feasibility of the technical solution. Therefore, capacitor C and current-limiting resistor R play a crucial role in the circuit. The parameters of these two components are primarily based on two factors: First, when the thermostat's auxiliary heating resistor is required to generate heat, its heating power should not vary significantly (e.g., no more than ±20%) due to the presence of other components in the circuit, thereby affecting its original heating function. Second, when the optocoupler input of the circuit conducts current, its conduction current should be limited to its normal conduction current range (e.g., 2-10mA) to avoid reliability issues caused by undercurrent and component damage caused by overcurrent. In practical applications, the specific selection of capacitor C and current-limiting resistor R requires calculation based on the actual specifications of the thermostat's auxiliary heating resistor and the optocoupler used.

Claims

1. A circuit for acquiring an on / off signal of a temperature controller with a parallel electric auxiliary heating resistor, comprising a frequency conversion controller (30) and a temperature controller (20) with a parallel electric auxiliary heating resistor, wherein the frequency conversion controller (30) has an optical coupler PC, a diode D, a current limiting resistor R and a main control circuit (31), a phase line L of a single-phase AC power supply (10) is respectively connected to one end of the temperature controller (20) with the parallel electric auxiliary heating resistor and a phase line input terminal LI of the frequency conversion controller (30), the other end of the temperature controller (20) with the parallel electric auxiliary heating resistor is connected to the temperature controller input terminal T of the frequency conversion controller (30), and a neutral line N of the single-phase AC power supply (10) is connected to the neutral line input terminal NI of the frequency conversion controller (30), characterized in that: The variable frequency controller (30) is connected to a capacitor C between the temperature controller input terminal T and the neutral line input terminal NI. One end of the optocoupler PC input side in the variable frequency controller (30) is connected to the temperature controller input terminal T of the variable frequency controller (30). The other end of the optocoupler PC input side is connected to one end of a diode D. The other end of the diode D is connected to one end of a current limiting resistor R. The other end of the current limiting resistor R is connected to the phase line input terminal LI of the variable frequency controller (30).

2. A circuit for acquiring an on / off signal of a temperature controller with a parallel electric auxiliary heating resistor, comprising a frequency conversion controller (30) and a temperature controller (20) with a parallel electric auxiliary heating resistor, wherein the frequency conversion controller (30) has an optical coupler PC, a diode D, a current limiting resistor R and a main control circuit (31), a phase line L of a single-phase AC power supply (10) is connected to one end of the temperature controller (20) with a parallel electric auxiliary heating resistor and a phase line input terminal LI of the frequency conversion controller (30), the other end of the temperature controller (20) with a parallel electric auxiliary heating resistor is connected to the temperature controller input terminal T of the frequency conversion controller (30), and a neutral line N of the single-phase AC power supply (10) is connected to the neutral line input terminal NI of the frequency conversion controller (30), characterized in that: The variable frequency controller (30) is connected to a capacitor C between the temperature controller input terminal T and the neutral line input terminal NI. One end of the optocoupler PC input side in the variable frequency controller (30) is connected to one end of the diode D and the temperature controller input terminal T. The other end of the optocoupler PC input side is connected to the other end of the diode D and one end of the current limiting resistor R. The other end of the current limiting resistor R is connected to the phase line input terminal LI of the variable frequency controller (30).

3. The on / off signal acquisition circuit of a temperature controller with a parallel electric auxiliary heating resistor according to claim 1, characterized in that: The forward signal input terminal of the optocoupler PC in the frequency conversion controller (30) is connected to the temperature controller input terminal T of the frequency conversion controller (30), the reverse signal input terminal of the optocoupler PC is connected to the positive electrode of the diode D, the negative electrode of the diode D is connected to one end of the current limiting resistor R, and the other end of the current limiting resistor R is connected to the phase line input terminal LI of the frequency conversion controller (30).

4. The on / off signal acquisition circuit of a temperature controller with a parallel electric auxiliary heating resistor according to claim 1, characterized in that: The reverse signal input terminal of the optocoupler PC in the frequency conversion controller (30) is connected to the temperature controller input terminal T of the frequency conversion controller (30), the forward signal input terminal of the optocoupler PC is connected to the cathode of the diode D, the anode of the diode D is connected to one end of the current limiting resistor R, and the other end of the current limiting resistor R is connected to the phase line input terminal LI of the frequency conversion controller (30).

5. The on / off signal acquisition circuit of a temperature controller with a parallel electric auxiliary heating resistor according to claim 2, characterized in that: The forward signal input terminal of the optocoupler PC in the frequency conversion controller (30) is connected to the cathode of the diode D and the temperature controller input terminal T, the reverse signal input terminal of the optocoupler PC is connected to the anode of the diode D and one end of the current limiting resistor R, and the other end of the current limiting resistor R is connected to the phase line input terminal LI of the frequency conversion controller (30).

6. The on / off signal acquisition circuit of a temperature controller with a parallel electric auxiliary heating resistor according to claim 2, characterized in that: The reverse signal input terminal of the optocoupler PC in the frequency conversion controller (30) is connected to the positive electrode of the diode D and the temperature controller input terminal T, the forward signal input terminal of the optocoupler PC is connected to the negative electrode of the diode D and one end of the current limiting resistor R, and the other end of the current limiting resistor R is connected to the phase line input terminal LI of the frequency conversion controller (30).

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