Communication circuit, communication device and air conditioner

Abstract

The utility model discloses a communication circuit, a communication device and an air conditioner, the communication circuit comprises a first sending module, a second sending module, a first monostable trigger and a second monostable trigger, the first sending module is used for outputting a first communication signal output by a first controller to the second monostable trigger through a communication line, and the second sending module is used for outputting a second communication signal output by a second controller to the second monostable trigger through a communication line; the second monostable trigger is used for outputting the first communication signal to the second controller; the second sending module is used for outputting a second communication signal output by the second controller to the first monostable trigger through the communication line, and the first monostable trigger is used for outputting the second communication signal to the first controller. According to the application, the monostable trigger is arranged as a communication receiving circuit, and when the monostable trigger supplies power, the maximum communication current is in a microampere level, so that the line loss of a communication line can be reduced, the communication line with a longer distance can be adapted, and the long-distance communication requirement can be met.

Description

Technical Field

[0001] This application relates to the field of electronic technology, specifically to a communication circuit, a communication device, and an air conditioner. Background Technology

[0002] In current air conditioning systems, multi-split and unit air conditioners are increasingly widely used. With the continuous expansion of building scale and the increasing coverage of air conditioning systems, the communication distance between indoor and outdoor units is becoming a growing concern.

[0003] Traditional air conditioner communication solutions are typically designed based on limited line loss ranges, making it difficult to meet the needs of ultra-long-distance communication. When the distance between the indoor and outdoor units exceeds a certain range, the signal transmission quality deteriorates sharply, leading to communication interruptions or data transmission errors, severely affecting the normal operation and control accuracy of the air conditioning system. Utility Model Content

[0004] The communication circuit, communication device, and air conditioner provided in this application can effectively alleviate the problem that current communication circuits cannot meet the needs of long-distance communication.

[0005] This application provides a communication circuit, which includes:

[0006] The first transmitting module has an input terminal for connecting to the transmitting terminal of the first controller in the host, and an output terminal for connecting to one end of the communication line.

[0007] The second transmitting module has an input terminal for connecting to the transmitting terminal of the second controller in the slave device, and an output terminal for connecting to the other end of the communication line.

[0008] The first monostable multivibrator has its input connected to one end of the communication line and its output connected to the receiving end of the first controller.

[0009] The input of the second monostable multivibrator is connected to the other end of the communication line, and the output of the second monostable multivibrator is connected to the receiving end of the second controller.

[0010] The first transmitting module is further configured to output the first communication signal output by the first controller to the second monostable multivibrator via a communication line, and the second monostable multivibrator is configured to output the first communication signal to the second controller; the second transmitting module is further configured to output the second communication signal output by the second controller to the first monostable multivibrator via a communication line, and the first monostable multivibrator is configured to output the second communication signal to the first controller.

[0011] In some embodiments of the communication circuit, the input terminal of the first monostable multivibrator includes a first trigger terminal and a first threshold terminal; the output terminal of the second monostable multivibrator includes a second trigger terminal and a second threshold terminal.

[0012] The first transmitting module is specifically used to output a low-level signal to the second trigger terminal via a communication line based on the high-level signal output by the first controller; the first transmitting module is also used to output a high-level signal to the second threshold terminal via a communication line based on the low-level signal output by the first controller.

[0013] The second transmitting module is specifically used to output a low-level signal to the first trigger terminal via a communication line based on the high-level signal output by the second controller; the second transmitting module is also used to output a high-level signal to the first threshold terminal via a communication line based on the low-level signal output by the second controller.

[0014] In some embodiments of the communication circuit, the first transmitting module includes a first switch, a first resistor, a second resistor, and a third resistor; a first end of the first switch is connected to one end of the first resistor and one end of the second resistor, the second end of the first switch and the other end of the second resistor are both energized, the third end of the first switch is connected to one end of the communication line and one end of the third resistor, the other end of the third resistor is energized, and the other end of the first resistor is used to connect to the transmitting end of the first controller.

[0015] In some embodiments of the communication circuit, the second transmitting module includes a second switch, a fourth resistor, and a fifth resistor. The first end of the second switch is connected to one end of the fourth resistor and one end of the fifth resistor. The second end of the second switch and the other end of the fifth resistor are both grounded. The other end of the fourth resistor is used to connect to the transmitting end of the second controller. The third end of the second switch is connected to the other end of the communication line.

[0016] In some embodiments of the communication circuit, the first switching transistor and the second switching transistor both include transistors. The first terminal of the first switching transistor and the second terminal of the second switching transistor are the base of the transistors. The second terminal of the first switching transistor and the second terminal of the second switching transistor are connected to the emitters of the transistors. The third terminal of the first switching transistor and the third terminal of the second switching transistor are the collectors of the transistors.

[0017] This application embodiment also provides a communication circuit, the communication circuit including:

[0018] The first transmitting module has an input terminal for connecting to the transmitting terminal of the first controller in the host, and an output terminal for connecting to one end of the communication line.

[0019] The second transmitting module has an input terminal for connecting to the transmitting terminal of the second controller in the slave device, and an output terminal for connecting to the other end of the communication line.

[0020] The first comparator has its inverting input connected to one end of the communication line, and its output connected to the receiving end of the first controller.

[0021] The second comparator has its inverting input connected to the other end of the communication line, and its output connected to the receiving end of the second controller.

[0022] The first transmitting module is further configured to output the first communication signal output by the first controller to the second comparator via a communication line, and the second comparator is configured to output the first communication signal to the second controller; the second transmitting module is further configured to output the second communication signal output by the second controller to the first comparator via a communication line, and the first comparator is configured to output the second communication signal to the first controller.

[0023] In some embodiments of the communication circuit, the first transmitting module includes a third switch, a sixth resistor, a seventh resistor, and an eighth resistor. The first end of the third switch is connected to one end of the sixth resistor and one end of the seventh resistor. The other end of the sixth resistor is used to connect to the transmitting end of the first controller. The second end of the third switch and the other end of the seventh resistor are both grounded. The collector of the third switch is connected to one end of the eighth resistor and one end of the communication line. The other end of the eighth resistor is energized.

[0024] In some embodiments of the communication circuit, the second transmitting module includes a fourth switch, a ninth resistor, and a tenth resistor. The first end of the fourth switch is connected to one end of the ninth resistor and one end of the tenth resistor. The other end of the ninth resistor is used to connect to the transmitting end of the second controller. The second end of the fourth switch and the other end of the tenth resistor are both grounded. The third end of the fourth switch is connected to the other end of the communication line.

[0025] This application also provides a communication device, which includes a circuit board on which the above-described communication circuit is integrated.

[0026] This application also provides an air conditioner, which includes a main unit and a slave unit. The main unit includes a first controller, and the slave unit includes a second controller. The first controller and the second controller are connected to each other through the communication circuit described above.

[0027] This application provides a communication circuit, device, and air conditioner. The communication circuit uses a monostable multivibrator or comparator as the communication receiving circuit. When the monostable multivibrator is powered, the maximum communication current is at the microamp level, which can reduce the line loss of the communication line. Therefore, compared with the current communication circuits, the microamp level communication current can be adapted to longer communication lines under the same line loss, thereby meeting the needs of long-distance communication. Attached Figure Description

[0028] The technical solution and other beneficial effects of this application will become apparent from the following detailed description of specific embodiments in conjunction with the accompanying drawings.

[0029] Figure 1 This is a first structural block diagram of a communication circuit provided in an embodiment of this application.

[0030] Figure 2 The schematic diagram of the first type of communication circuit provided in the embodiments of this application.

[0031] Figure 3 This is a second structural block diagram of a communication circuit provided in an embodiment of this application.

[0032] Figure 4 The second circuit schematic diagram is provided in the communication circuit of the embodiment of this application. Detailed Implementation

[0033] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0034] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Features thus defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this utility model, "multiple" means two or more, unless otherwise explicitly specified.

[0035] Please see Figure 1 This embodiment provides a communication circuit, which includes a first transmitting module 11, a second transmitting module 12, a first monostable multivibrator 13, and a second monostable multivibrator 14. In practical applications, the first transmitting module 11 and the first monostable multivibrator 13 can be located on the host side, and the second transmitting module 12 and the second monostable multivibrator 14 can be located on the slave side. The host side and the slave side can establish a communication connection based on a communication line.

[0036] The input terminal of the first transmitting module 11 is connected to the transmitting terminal of the first controller 15 in the host, and the output terminal of the first transmitting module 11 is connected to one end of the communication line; the input terminal of the second transmitting module 12 is connected to the transmitting terminal of the second controller 16 in the slave, and the output terminal of the second transmitting module 12 is connected to the other end of the communication line; the input terminal of the first monostable multivibrator 13 is connected to one end of the communication line, and the output terminal of the first monostable multivibrator 13 is connected to the receiving terminal of the first controller 15; the input terminal of the second monostable multivibrator 14 is connected to the other end of the communication line, and the output terminal of the second monostable multivibrator 14 is connected to the receiving terminal of the second controller 16.

[0037] In specific implementation, the first transmitting module 11 is also used to output the first communication signal output by the first controller 15 to the second monostable multivibrator 14 via a communication line, and the second monostable multivibrator 14 is used to output the first communication signal to the second controller 16; the second transmitting module 12 is also used to output the second communication signal output by the second controller 16 to the first monostable multivibrator 13 via a communication line, and the first monostable multivibrator 13 is used to output the second communication signal to the first controller 15. In this application, by setting a monostable multivibrator as the communication receiving circuit, the maximum communication current of the monostable multivibrator is at the microamp level, such as 50 microamps, when powered by a voltage of 5V. This reduces the line loss of the communication line. Compared with the current communication circuit, under the same line loss, the microamp level communication current can be adapted to a longer communication line, thereby meeting the needs of long-distance communication. The operating current of the receiving circuit mainly depends on the input current of the trigger terminal and the threshold terminal of the monostable multivibrator. This input current is at the microamp level, thus the power supply requirements on the host side are very low.

[0038] Please see Figure 2 In some embodiments, the input terminal of the first monostable multivibrator 13 includes a first trigger terminal (TRIG1 signal terminal in this embodiment) and a first threshold terminal (TH1 signal terminal in this embodiment); the output terminal of the second monostable multivibrator 14 includes a second trigger terminal (TRIG2 signal terminal in this embodiment) and a second threshold terminal (TH2 signal terminal in this embodiment); the first transmitting module 11 is specifically used to output a low-level signal to the second trigger terminal through a communication line based on the high-level signal output by the first controller 15, and the second monostable multivibrator 14 outputs a high-level signal to the receiving terminal of the second controller 16 based on the low-level signal, so as to complete the transmission of a high-level communication signal; the first transmitting module 11 is used to output a high-level signal to the second threshold terminal through a communication line based on the low-level signal output by the first controller 15, and the second monostable multivibrator 14 outputs a low-level signal to the receiving terminal of the second controller 16 based on the high-level signal, so as to complete the transmission of a low-level communication signal, thereby realizing the transmission of communication signals from the host side to the slave side.

[0039] Specifically, the second transmitting module 12 is used to output a low-level signal to the first trigger terminal via a communication line based on the high-level signal output by the second controller 16, and the first monostable multivibrator 13 outputs a high-level signal to the receiving terminal of the first controller 15 based on the low-level signal, thereby completing the transmission of the high-level communication signal; the second transmitting module 12 is used to output a high-level signal to the first threshold terminal via a communication line based on the low-level signal output by the second controller 16, and the first monostable multivibrator 13 outputs a low-level signal to the receiving terminal of the first controller 15 based on the high-level signal, thereby completing the transmission of the low-level communication signal, thereby realizing the transmission of communication signals from the machine side to the host side.

[0040] Please see Figure 2 In one embodiment, the first transmitting module 11 includes a first switch Q1, a first resistor R1, a second resistor R2, and a third resistor R3. The first terminal of the first switch Q1 is connected to one end of the first resistor R1 and one end of the second resistor R2. The second terminal of the first switch Q1 and the other end of the second resistor R2 are both energized. The third terminal of the first switch Q1 is connected to one end of the communication line and one end of the third resistor R3. The other end of the third resistor R3 is energized. The other end of the first resistor R1 is used to connect to the transmitting end of the first controller 15. When the first controller 15 outputs a high-level signal, the first switch Q1 is saturated and turned on, and the communication line is at a low level. This low level is recognized by the second trigger port of the second monostable multivibrator 14 and outputs a high level through its internal trigger structure. Thus, the high-level signal output by the first controller 15 on the host side is received by the second controller 16 on the slave side. When the first controller 15 outputs a low-level signal, the first switch Q1 is turned off, and the communication line is pulled up by the third resistor R3 to present a high level. After the second threshold terminal of the second monostable trigger 14 recognizes the high-level signal, it outputs a low-level signal through the internal trigger. Thus, the low-level signal of the first controller 15 on the host side is received by the second controller 16 on the slave side, realizing communication between the host and the slave.

[0041] In one embodiment, the second transmitting module 12 includes a second switch Q2, a fourth resistor R4, and a fifth resistor R5. The first terminal of the second switch Q2 is connected to one end of the fourth resistor R4 and one end of the fifth resistor R5. The second terminal of the second switch Q2 and the other end of the fifth resistor R5 are both grounded. The other end of the fourth resistor R4 is used to connect to the transmitting terminal of the second controller 16. The third terminal of the second switch Q2 is connected to the other end of the communication line. When the second controller 16 outputs a high-level signal, the second switch Q2 is saturated and turned on, and the communication line is at a low level. This low level is recognized by the first trigger port of the first monostable multivibrator 13 and outputs a high level through its internal trigger structure. Thus, the high-level signal output by the first controller 15 on the slave side is received by the first controller 15 on the host side. When the second controller 16 outputs a low-level signal, the second switch Q2 is turned off. The first threshold terminal of the first monostable multivibrator 13 on the master side is pulled up by the third resistor R3 and presents a high level. After the first threshold terminal of the first monostable multivibrator 13 recognizes the high-level signal, it outputs a low-level signal through the internal trigger. Thus, the low-level signal of the second controller 16 on the slave side is received by the first controller 15 on the master side, realizing communication between the master and slave.

[0042] In one embodiment, both the first switch Q1 and the second switch Q2 include transistors. The first terminal of the first switch Q1 and the second terminal of the second switch Q2 are the base of the transistors. The second terminal of the first switch Q1 and the second terminal of the second switch Q2 are connected to the emitter of the transistors. The third terminal of the first switch Q1 and the third terminal of the second switch Q2 are the collector of the transistors.

[0043] As one embodiment, the VCC voltage on the host side and the VDD voltage on the slave side are both 5V, and the power supply of the first controller 15 and the second controller 16 is also 5V, with the high-level signal being 5V and the low-level signal being 0V.

[0044] Please see Figure 3 This application also provides a communication circuit, which includes a first transmitting module 11, a second transmitting module 12, a first comparator 18, and a second comparator 19. In practical applications, the first transmitting module 11 and the first comparator 18 can be located on the host side, and the second transmitting module 12 and the second comparator 19 can be located on the slave side. The host side and the slave side can establish a communication connection based on a communication line.

[0045] The input terminal of the first transmitting module 11 is connected to the transmitting terminal of the first controller 15 in the host, and the output terminal of the first transmitting module 11 is connected to one end of the communication line; the input terminal of the second transmitting module 12 is connected to the transmitting terminal of the second controller 16 in the slave, and the output terminal of the second transmitting module 12 is connected to the other end of the communication line; the inverting input terminal of the first comparator 18 is connected to one end of the communication line, and the output terminal of the first comparator 18 is connected to the receiving terminal of the first controller 15; the inverting input terminal of the second comparator 19 is connected to the other end of the communication line, and the output terminal of the second comparator 19 is connected to the receiving terminal of the second controller 16.

[0046] In specific implementation, the first transmitting module 11 is also used to output the first communication signal output by the first controller 15 to the second comparator 19 via a communication line. The second comparator 19 is used to output the first communication signal to the second controller 16. The second transmitting module 12 is also used to output the second communication signal output by the second controller 16 to the first comparator 18 via a communication line. The first comparator 18 is used to output the second communication signal to the first controller 15. Similarly, in this embodiment, by setting the comparator as the communication receiving circuit on both the master and slave sides, when the communication circuit is powered by 5V, the maximum communication current is at the microamp level, such as 5 microamps. This reduces the line loss of the communication line. Compared with the current communication circuit, under the same line loss, the microamp level communication current can be adapted to a longer communication line, thereby meeting the needs of long-distance communication. The operating current of the receiving circuit mainly depends on the operating current of the comparator, which can be at the milliamp level, such as about 1mA. Therefore, the power supply requirements on the master side are very low.

[0047] In one embodiment, the non-inverting input terminal of the first comparator 18 is connected to the eleventh resistor R11 and the twelfth resistor R12, and the output terminal of the first comparator 18 is connected to the thirteenth resistor R13. The eleventh resistor R11 and the twelfth resistor R12 act as voltage divider resistors, providing a reference voltage for the first comparator 18. The non-inverting input terminal of the second comparator 19 is connected to the fourteenth resistor R14 and the fifteenth resistor R15, and the output terminal of the second comparator 19 is connected to the sixteenth resistor R16. Similarly, the fourteenth resistor R14 and the fifteenth resistor R15 act as voltage divider resistors, providing a reference voltage for the second comparator 19.

[0048] Please see Figure 4In one embodiment, the first transmitting module 11 includes a third switch Q3, a sixth resistor R6, a seventh resistor R7, and an eighth resistor R8. The first end of the third switch Q3 is connected to one end of the sixth resistor R6 and one end of the seventh resistor R7. The other end of the sixth resistor R6 is used to connect to the transmitting end of the first controller 15. The second end of the third switch Q3 and the other end of the seventh resistor R7 are both grounded. The collector of the third switch Q3 is connected to one end of the eighth resistor R8 and one end of the communication line. The other end of the eighth resistor R8 is energized.

[0049] When the first controller 15 on the host side sends a high-level signal, the third switch Q3 is saturated and turned on, and the communication line presents a low level. This low level is received by the inverting input of the second comparator 19 on the slave side. At this time, the voltage of the non-inverting input of the second comparator 19 on the slave side is R_14 / (R_14+R_15)*VDD=1 / 2*VDD=2.5V. At this time, the potential of the inverting input of the second comparator 19 on the slave side is less than the potential of the non-inverting input, and the second comparator 19 outputs a high level. Thus, the high level output by the first controller 15 on the host side is received by the receiving end of the second controller 16 on the slave side. When the first controller 15 on the master side sends a low level, the third switch Q3 is turned off, and the communication line presents a high level under the pull-up effect of the eighth resistor R8. This level is received by the inverting input terminal of the second comparator 19 on the slave side. At this time, the voltage of the non-inverting input terminal of the second comparator 19 on the slave side is R_14 / (R_14+R_15)*VDD=1 / 2*VDD=2.5V. At this time, the potential of the inverting input terminal of the second comparator 19 on the slave side is greater than the potential of the non-inverting input terminal, and the second comparator 19 outputs a low level. Thus, the low level output by the first controller 15 on the master side is received by the receiving terminal of the second controller 16 on the slave side, thereby realizing the communication between the master and the slave.

[0050] In one embodiment, the second transmitting module 12 includes a fourth switch Q4, a ninth resistor R9, and a tenth resistor R10. The first end of the fourth switch Q4 is connected to one end of the ninth resistor R9 and one end of the tenth resistor R10. The other end of the ninth resistor R9 is used to connect to the transmitting end of the second controller 16. The second end of the fourth switch Q4 and the other end of the tenth resistor R10 are both grounded. The third end of the fourth switch Q4 is connected to the other end of the communication line.

[0051] When the second controller 16 on the slave side sends a high level, the fourth switch Q4 is saturated and conducts, transmitting the potential to the inverting input of the first comparator 18 on the master side via the communication line. The potential of the inverting input of the first comparator 18 on the master side is R0 / (R8+R0)*VCC (R8 = 100KΩ, which is much larger than the set value of R0 = 10KΩ), where R0 is the line loss of the communication line. The potential of the non-inverting input of the first comparator 18 is R12 / (R11+R12)*VCC = 1 / 2*VCC = 2.5V. In summary, when the second controller 16 on the slave side sends a high level, the potential of the inverting input of the first comparator 18 on the master side is less than the potential of the non-inverting input, and the first comparator 18 outputs a high level. Therefore, the receiving end of the first controller 15 can correctly receive the high level sent by the slave. When the second controller 16 on the slave side sends a low level, the fourth switch Q4 is turned off, and the potential of the inverting input terminal of the first comparator 18 on the master side is pulled up by the eighth resistor R8 to present a high level. This satisfies the condition that the potential of the inverting input terminal is greater than the potential of the non-inverting input terminal, and the first comparator 18 outputs a low level. Thus, the low level sent by the second controller 16 on the slave side is received by the first controller 15 on the master side, thereby realizing communication between the master and slave.

[0052] As one embodiment, the third switch Q3 and the fourth switch Q4 in this embodiment include transistors. The first terminal of the third switch Q3 and the first terminal of the fourth switch Q4 are the bases of the transistors. The second terminal of the third switch Q3 and the second terminal of the fourth switch Q4 are connected to the emitters of the transistors. The third terminal of the third switch Q3 and the third terminal of the fourth switch Q4 are the collectors of the transistors.

[0053] This application embodiment also provides a communication device, which includes a circuit board on which the above-described communication circuit is integrated. Since the communication circuit has been described in detail above, it will not be repeated here.

[0054] This application also provides an air conditioner, which includes a main unit and a slave unit. The main unit includes a first controller, and the slave unit includes a second controller. The first controller and the second controller are connected by the communication circuit described above. Since the communication circuit has been described in detail above, it will not be repeated here.

[0055] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0056] The communication circuits provided in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A communication circuit, characterized in that, The communication circuit includes: The first transmitting module has an input terminal for connecting to the transmitting terminal of the first controller in the host, and an output terminal for connecting to one end of a communication line. The second transmitting module has an input terminal for connecting to the transmitting terminal of the second controller in the slave device, and an output terminal for connecting to the other end of the communication line. The first monostable multivibrator has its input terminal connected to one end of the communication line, and its output terminal connected to the receiving end of the first controller. The second monostable multivibrator has its input connected to the other end of the communication line and its output connected to the receiving end of the second controller. The first transmitting module is further configured to output the first communication signal output by the first controller to the second monostable multivibrator via the communication line, and the second monostable multivibrator is configured to output the first communication signal to the second controller; the second transmitting module is further configured to output the second communication signal output by the second controller to the first monostable multivibrator via the communication line, and the first monostable multivibrator is configured to output the second communication signal to the first controller.

2. The communication circuit according to claim 1, characterized in that, The input terminals of the first monostable multivibrator include a first trigger terminal and a first threshold terminal; the output terminals of the second monostable multivibrator include a second trigger terminal and a second threshold terminal. The first transmitting module is specifically used to output a low-level signal to the second trigger terminal via the communication line based on the high-level signal output by the first controller; the first transmitting module is also used to output a high-level signal to the second threshold terminal via the communication line based on the low-level signal output by the first controller. The second transmitting module is specifically used to output a low-level signal to the first trigger terminal via the communication line based on the high-level signal output by the second controller; the second transmitting module is also used to output a high-level signal to the first threshold terminal via the communication line based on the low-level signal output by the second controller.

3. The communication circuit according to claim 2, characterized in that, The first transmitting module includes a first switch, a first resistor, a second resistor, and a third resistor; a first end of the first switch is connected to one end of the first resistor and one end of the second resistor, a second end of the first switch and the other end of the second resistor are both energized, a third end of the first switch is connected to one end of the communication line and one end of the third resistor, the other end of the third resistor is energized, and the other end of the first resistor is used to connect to the transmitting end of the first controller.

4. The communication circuit according to claim 3, characterized in that, The second transmitting module includes a second switch, a fourth resistor, and a fifth resistor. The first end of the second switch is connected to one end of the fourth resistor and one end of the fifth resistor. The second end of the second switch and the other end of the fifth resistor are both grounded. The other end of the fourth resistor is used to connect to the transmitting end of the second controller. The third end of the second switch is connected to the other end of the communication line.

5. The communication circuit according to claim 4, characterized in that, Both the first and second switching transistors include transistors. The first terminal of the first switching transistor and the second terminal of the second switching transistor are the base of the transistor. The second terminal of the first switching transistor and the second terminal of the second switching transistor are connected to the emitter of the transistor. The third terminal of the first switching transistor and the third terminal of the second switching transistor are the collector of the transistor.

6. A communication circuit, characterized in that, The communication circuit includes: The first transmitting module has an input terminal for connecting to the transmitting terminal of the first controller in the host, and an output terminal for connecting to one end of a communication line. The second transmitting module has an input terminal for connecting to the transmitting terminal of the second controller in the slave device, and an output terminal for connecting to the other end of the communication line. A first comparator, wherein the inverting input of the first comparator is connected to one end of the communication line, and the output of the first comparator is connected to the receiving end of the first controller; The second comparator has its inverting input connected to the other end of the communication line, and its output connected to the receiving end of the second controller. The first transmitting module is further configured to output the first communication signal output by the first controller to the second comparator via the communication line, and the second comparator is configured to output the first communication signal to the second controller; the second transmitting module is further configured to output the second communication signal output by the second controller to the first comparator via the communication line, and the first comparator is configured to output the second communication signal to the first controller.

7. The communication circuit according to claim 6, characterized in that, The first transmitting module includes a third switch, a sixth resistor, a seventh resistor, and an eighth resistor. The first end of the third switch is connected to one end of the sixth resistor and one end of the seventh resistor. The other end of the sixth resistor is used to connect to the transmitting end of the first controller. The second end of the third switch and the other end of the seventh resistor are both grounded. The collector of the third switch is connected to one end of the eighth resistor and one end of the communication line. The other end of the eighth resistor is energized.

8. The communication circuit according to claim 7, characterized in that, The second transmitting module includes a fourth switch, a ninth resistor, and a tenth resistor. The first end of the fourth switch is connected to one end of the ninth resistor and one end of the tenth resistor. The other end of the ninth resistor is used to connect to the transmitting end of the second controller. The second end of the fourth switch and the other end of the tenth resistor are both grounded. The third end of the fourth switch is connected to the other end of the communication line.

9. A communication device, characterized in that, The communication device includes a circuit board on which the communication circuit as described in any one of claims 1-8 is integrated.

10. An air conditioner, characterized in that, The air conditioner includes a main unit and a slave unit. The main unit includes a first controller, and the slave unit includes a second controller. The first controller and the second controller are connected by a communication circuit as described in any one of claims 1-8.

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