Communication device for air conditioner

Abstract

To provide a communication device for an air conditioner capable of stabilizing communications.SOLUTION: A communication device for an air conditioner is configured by including a plurality of apparatuses connected by two AC power supply lines and one communication line. The communication device for the air conditioner has a power supply circuit and a transmission circuit. The power supply circuit generates DC voltage as the basis for a phase of either one of the two AC power supply lines. The transmission circuit fluctuates voltage of the communication line on the basis of a signal transmitted from a control device that controls the air conditioner. A capacitor is connected to a space between the transmission circuit and the communication line. When a reference potential of the communication line rises, voltage of the communication signal flowing in the communication line is boosted by using an electric charge of the capacitor.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] An embodiment of the present invention relates to a communication device for an air conditioner. [Background technology]

[0002] There is a communication device for air conditioners that uses two switches to suppress communication failures caused by charges accumulated in the parasitic capacitor of the communication line. In this method, one switch is used to raise the communication line voltage, and the other switch is used to discharge the parasitic capacitance. Of these, the former switch raises the voltage by shorting the communication circuit power supply and the communication line. However, if the communication line voltage is higher than the communication circuit power supply voltage, the voltage cannot be raised, and communication may become unstable, with communication content being dropped or communication being interrupted. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3578134 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a communication device for an air conditioner that can stabilize communication. [Means for solving the problem]

[0005] The communication device of the air conditioner of the embodiment is composed of a plurality of devices connected by two AC power lines and one communication line. The communication device of the air conditioner includes a power supply circuit and a transmission circuit. The power supply circuit generates a DC voltage based on the phase of one of the two AC power lines. The transmission circuit varies the voltage of the communication line based on a signal transmitted by a control device that controls the air conditioner. A capacitor is connected between the transmission circuit and the communication line. When the reference potential of the communication line rises, the charge of the capacitor is used to boost the voltage of the communication signal.

[0006] In addition, a communication device for an air conditioner in another embodiment is composed of a plurality of devices connected by two AC power lines and one communication line. The communication device for an air conditioner includes a power supply circuit and a transmission circuit. The power supply circuit generates a DC voltage based on the phase of one of the two AC power lines. The transmission circuit varies the voltage of the communication line based on a signal transmitted by a control device that controls the air conditioner. A circuit in which a diode and a capacitor are connected in parallel is provided between the transmission circuit and the communication line. The diode is connected in a direction that causes a current to flow from the transmission circuit to the communication line. When the reference potential of the communication line rises, the charge of the capacitor is used to boost the voltage of the communication signal. [Brief description of the drawings]

[0007] [Figure 1] 1 is a block diagram showing an example of the configuration of an air conditioner according to a first embodiment. [Diagram 2] 2 is a block diagram showing the circuits and functions of a communication device of the air conditioner according to the first embodiment. [Diagram 3] 4A to 4C are diagrams showing examples of various parasitic components occurring in a wiring section 80. [Figure 4] 1A and 1B are diagrams showing examples of communication waveforms on the transmitting side and the receiving side when a disturbance occurs in a conventional communication circuit. [Diagram 5] 4A and 4B are diagrams showing examples of communication waveforms on the transmitting side and communication waveforms on the receiving side when a disturbance occurs in the communication circuit of the air conditioner of the first embodiment. [Figure 6] FIG. 11 is a block diagram showing the circuits and functions of a communication device of an air conditioner according to a second embodiment. [Figure 7] FIG. 11 is a block diagram showing the circuits and functions of a communication device for an air conditioner according to a third embodiment. [Figure 8] FIG. 13 is a block diagram showing the circuits and functions of a communication device for an air conditioner according to a fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, a communication device for an air conditioner according to an embodiment will be described with reference to the drawings.

[0009] (First embodiment) FIG. 1 is a block diagram showing an example of the configuration of an air conditioner 1 of the first embodiment. The air conditioner 1 includes, for example, one outdoor unit 10 and multiple indoor units 20 (20A, 20B, . . . , 20M). The outdoor unit 10 and the multiple indoor units 20 are all connected to a commercial AC power supply 31 by two AC power lines (a first AC power line 32 and a second AC power line 33), and are connected to each other by one communication line 34. Note that the commercial AC power supply 31 is illustrated as a single-phase power supply, but a three-phase AC power supply may be used as a power supply for the outdoor unit 10 that is equipped with a compressor and consumes large power, and any two phases of the three-phase AC power supply may be connected to the indoor unit 20 as AC power supply lines 32 and 33. Furthermore, when a four-wire three-phase AC power supply having an N phase that is a neutral point is used, one phase and the N phase of the three-phase AC power supply may be used as AC power supply lines 32 and 33 to supply operating power to the indoor unit 20.

[0010] The multiple indoor units 20A, 20B,..., 20M have the same configuration, and in the following description, when the indoor units are not differentiated from one another, they are referred to as indoor units 20. The first AC power supply line 32, the second AC power supply line 33, and the communication line 34 are housed in a single cable generally called a crossover line. In this case, one wire of the three-wire cable is used as the communication line 34. In the first embodiment, multiple indoor units 20 are provided, but the number of indoor units 20 may be single (one unit).

[0011] 2, the communication device 2 of the embodiment is composed of a first communication device 40 of the outdoor unit 10 and a second communication device 50 of the indoor unit 20. The outdoor unit 10 is further provided with a first air conditioning circuit 60, and the indoor unit 20 is provided with a second air conditioning circuit 70. The first air conditioning circuit 60 and the second air conditioning circuit 70 are examples of control devices, and each operates in conjunction with the other to perform a predetermined air conditioning operation.

[0012] The first communication device 40 and the second communication device 50 are connected by the first AC power supply line 32, the second AC power supply line 33, and the communication line 34 via the wiring section 80, which is the above-mentioned three-wire cable. The wiring section 80 is connected to the first AC power supply line 32 on the first communication device 40 side by a connection terminal L, connected to the second AC power supply line 33 by a connection terminal N, and connected to the communication line 34 by a connection terminal S. The wiring section 80 is connected to the first AC power supply line 32 on the second communication device 50 side by a connection terminal L', connected to the second AC power supply line 33 by a connection terminal N', and connected to the communication line 34 by a connection terminal S'.

[0013] The first communication device 40 includes, for example, a power supply circuit 41, a transmission circuit 42, a reception circuit 43, a reverse voltage protection diode 44, and a capacitor 45. The second communication device 50 includes, for example, a power supply circuit 51, a transmission circuit 52, a reception circuit 53, a reverse voltage protection diode 54, and a capacitor 55. The first communication device 40 and the second communication device 50 have similar configurations. These configurations will be described below using the first communication device 40.

[0014] The power supply circuit 41 is connected to two AC power supply lines 32, 33 connected to a commercial AC power supply 31, and generates a DC voltage based on one of the phases, here the phase of the second AC power supply line 33. The transmission circuit 42 varies the voltage of the communication line 34 based on a signal generated by a first air conditioning circuit 60 that controls the outdoor unit 10 of the air conditioner 1, i.e., a transmission signal to the indoor unit 20. For example, a communication method is used for the voltage variation of the communication line 34, in which if the transmission signal is "1" during a carrier cycle in a certain period, a high potential is maintained for a predetermined period, while if the transmission signal is "0", a low potential state is maintained during the carrier cycle.

[0015] The transmission circuit 42 includes a series circuit of a first switch 42A and a second switch 42B connected to a power supply circuit 41. The first switch 42A and the second switch 42B are both configured, for example, from components with low on-resistance. The first switch 42A and the second switch 42B may be configured from components other than the components with low on-resistance.

[0016] The first switch 42A located on the high potential side of the power supply circuit 41 is a switch for increasing the voltage of the communication line 34, and the second switch 42B connected to the reference potential side of the power supply circuit 41, i.e., the second AC power supply line 33, is a switch for decreasing the voltage of the communication line 34. The communication line 34 is connected to the interconnection point of both switches 42A, 42B. This connection causes the first switch 42A or the second switch 42B to be closed (turned ON), generating a square wave voltage in the communication line 34. The upper limit of the voltage of the communication line 34 at this time is limited to the voltage of the power supply circuit 41.

[0017] The receiving circuit 43 has, for example, a function as a voltage sensor that reads a voltage, a function of generating a signal corresponding to a voltage fluctuation, and a function of transmitting the generated signal to the first air conditioning circuit 60. The receiving circuit 43 is connected between the communication line 34 and the second AC power supply line 33 which is the low potential side of the power supply circuit 41, reads a voltage fluctuation occurring in the communication line 34, and transmits a signal corresponding to the read voltage fluctuation to the first air conditioning circuit 60. Although not shown, a general receiving circuit including an RC filter that extracts a voltage change of the communication signal, and an isolation circuit that responds to the rising and falling edges of the signal output from the RC filter, isolates the signal, and outputs it as a high / low signal is used as the receiving circuit 43.

[0018] The reverse voltage protection diode 44 is provided in parallel with the receiving circuit 43. The reverse voltage protection diode 44 protects the receiving circuit 43 from a reverse voltage that is applied to the receiving circuit 43 in a direction opposite to the direction in which the receiving circuit 43 is designed.

[0019] The capacitor 45 is inserted between the transmission circuit 42 and the communication line 34 and is included in the communication circuit. It stores electricity when a current flows through the communication line 34. When the reference potential of the communication line 34 rises, the capacitor 45 releases the stored charge to boost the voltage of the communication signal flowing through the communication line 34.

[0020] The first air conditioning circuit 60 receives a signal corresponding to the voltage fluctuation transmitted by the receiving circuit 43. The first air conditioning circuit 60 generates a control signal for controlling the opening and closing of the first switch 42A and the second switch 42B in the transmitting circuit 42 based on the settings of the air conditioner 1, the operating status of the outdoor unit 10, and the received signal. The first air conditioning circuit 60 transmits the generated control signal to the transmitting circuit 42.

[0021] The second air conditioning circuit 70 receives a signal corresponding to the voltage fluctuation transmitted by the receiving circuit 53. The second air conditioning circuit 70 generates a control signal for controlling the opening and closing of the first switch 52A and the second switch 52B in the transmitting circuit 52, based on the settings of the air conditioner 1, the operating status of the indoor unit 20, and the received signal. The second air conditioning circuit 70 transmits the generated control signal to the transmitting circuit 42. Note that the settings of the air conditioner 1 include, but are not limited to, operation modes such as on / off, cooling / heating, and indoor temperature settings.

[0022] In the communication device of the air conditioner of the first embodiment, one wire of a three-wire cable is used as the communication line 34. If the communication line 34 is in the same cable as the AC power lines 32 and 33, it will be affected by the AC power lines 32 and 33, compared to when the communication lines are independent. Therefore, the communication line 34 may experience distortion of the communication waveform due to each or a combination of parasitic inductance, parasitic resistance, and / or parasitic capacitance.

[0023] 3, in the wiring section 80, a wiring 81 is connected to a connection terminal L, a wiring 82 is connected to a connection terminal N, and a wiring 83 is connected to a connection terminal S. A wiring 84 is connected to a connection terminal L', a wiring 85 is connected to a connection terminal N', and a wiring 86 is connected to a connection terminal S'. The wiring 81 and the wiring 84 are connected to the first AC power supply line 32, and the wiring 82 and the wiring 85 are connected to the second AC power supply line 33. A parasitic reactor 87 (parasitic inductance) and a parasitic resistance 88 are generated between the connection terminals L-L', between the connection terminals N-N', and between the connection terminals S-S', respectively. A parasitic capacitor 89 (parasitic capacitance) is generated between the wirings connecting the respective terminals.

[0024] Here, the reference potentials of the transmitting side (e.g., the outdoor unit 10 side) and the receiving side (e.g., the indoor unit 20 side) of the communication are equal when no current flows through the AC power supply lines 32, 33, but become unequal when a current flows through the AC power supply lines 32, 33. The cause of the unequal reference potentials is the influence of the parasitic inductance in the parasitic reactor 87 in the wiring section 80 and the parasitic resistance in the parasitic resistor 88, and at commercial frequencies, the parasitic resistance is dominant in this influence. Then, the voltage generated by this current flow can adversely affect the communication operation.

[0025] For example, if the capacitor 45 is not provided between the transmission circuit 42 and the communication line 34, when the equipment in the outdoor unit 10 and / or the indoor unit 20 operates and a current flows through the AC power lines 32, 33, a voltage (disturbance voltage) is generated in the wiring due to the presence of the parasitic reactor 87, parasitic resistor 88, and parasitic capacitor 89 in the wiring section 80. This disturbance voltage changes the reference potential of the communication line. For example, the voltage (disturbance voltage) V generated by the parasitic resistor 88 is V=IR, where I is the current flowing through the AC power lines 32, 33 and R is the parasitic resistance. In this way, the disturbance voltage V increases as the current I flowing through the outdoor unit 10 and / or the indoor unit 20 increases. In particular, a large current generated by the operation of the compressor of the outdoor unit 10 increases this disturbance voltage V. For this reason, the reference potential BV of the receiving side, shown in the lower part of FIG. 4, increases relative to the output voltage of the power supply circuit 41 of the transmitting side, shown in the upper part of the communication waveform, and the voltage of the communication waveform becomes relatively small. As a result, the amplitude width (voltage) of the square wave, which is the communication signal, is suppressed and reduced, and the receiving side (here, the power supply circuit 51 side) is unable to read the correct waveform, making normal communication impossible. In particular, when the disturbance voltage exceeds the power supply voltage of the communication circuit, i.e., the output voltage of the power supply circuits 41 and 51, the receiving circuit 43 cannot read the voltage change, and communication is not established.

[0026] In contrast to this, in the communication device 2 of the first embodiment, a circuit is provided on the transmitting side in which a capacitor 45 is connected between the transmitting circuit 42 and the communication line 34. When the reference potential of the communication line 34 rises on the receiving side due to the above-mentioned disturbance, the capacitor 45 releases the stored charge and boosts the voltage of the communication signal flowing through the communication line 34.

[0027] Therefore, even if the reference potential BV of the communication line 34 on the receiving side, which is the envelope of the lower end of the pulse signal shown in FIG. 5, rises, the amplitude width of the square wave communication signal flowing through the communication line 34 is maintained at approximately the same magnitude as when the voltage of the communication line 34 is normal. Therefore, the receiving side (here, the power supply circuit 51 side) can receive a correct signal, and communication disturbance can be suppressed. Note that, as in FIG. 4, FIG. 5 shows the communication waveform of the transmitting side in the upper part and the communication waveform of the receiving side in the lower part. For reference, FIG. 5 also shows a case where the transmission signal is all "1". Here, when the transmission signal is "0", there is no high voltage (pulse) section during a specified communication duty period, and the voltage remains at the minimum voltage.

[0028] Incidentally, it is conceivable to suppress the influence of parasitic resistance and parasitic inductance by setting the DC voltage output from the transmission circuit 42 to a value higher than the disturbance voltage, but it is necessary to configure the power supply circuits 41 and 51 as DC power supply circuits with high voltage output, which causes the device to become larger and more complicated. In this respect, in the communication device 2 of the first embodiment, by simply connecting a capacitor 45 between the transmission circuit 42 and the communication line 34, the output of the power supply circuits 41 and 51 is low voltage, enabling smooth communication, and cost reduction can be expected due to the miniaturization and simplification of the power supply circuit. Similarly, on the receiving side, a capacitor 55 is connected between the transmission circuit 52 and the communication line 34, so the same effect is obtained. In addition, the configuration can be simpler than that of the communication devices of other embodiments described later.

[0029] Second embodiment Next, the second embodiment will be described with reference to FIG. 6. The communication device 2 of the second embodiment is different from the first embodiment in that the resistors 46, 56 are inserted in series on the downstream side of the power supply circuits 41, 51 in the communication circuits in which the capacitors 45, 55 are provided, respectively. That is, the capacitor 45 and the resistor 46 are connected in series to the communication line 34 of the transmission circuit 42 connected to the output of the power supply circuit 41 of the outdoor unit 10. Similarly, the capacitor 55 and the resistor 56 are connected in series to the communication line 34 of the transmission circuit 52 connected to the output of the power supply circuit 51 of the indoor unit 20. The other points have the same configuration as the communication device of the first embodiment. Note that the order of connection of the resistors 46, 56 and the capacitors 45, 55 does not matter. The resistors 46, 56 may be connected to the output of the power supply circuits 41, 51, and the capacitors 45, 55 may be connected to the output of the power supply circuits 41, 51.

[0030] As in the first embodiment, the communication device 2 of the second embodiment is provided with capacitors 45 and 55, so that even if the voltage of the communication line 34 increases due to an external disturbance, the effects of parasitic resistance and parasitic inductance can be suppressed.

[0031] Furthermore, in the communication device 2 of the second embodiment, resistors 46, 56 are inserted in series with the capacitors 45, 55 on the downstream side as viewed from the power supply circuits 41, 51. The first switches 42A, 52A and the second switches 42B, 52B in the transmission circuits 42, 52 are components with low on-resistance, so that a large current may flow instantaneously. The large current is generated because the capacitors 45, 55 are charging currents and the resistance of the charging path is extremely low. Such a large current may shorten the life of the capacitors 45, 55. Therefore, by inserting the resistors 46, 56, respectively, the peak value of the current flowing through the reception circuits 43, 53 and the wiring section 80 can be suppressed, the generation of a large instantaneous current flowing through the communication line 34 can be suppressed, and the life of the capacitors 45, 55 can be extended.

[0032] Furthermore, when the impedance of the communication line 34 and the receiving circuits 43, 53 is low, a pulsed current flows through the communication line. When a pulsed current flows, components of frequencies higher than the communication frequency are propagated as noise, which may interfere with other devices. In this regard, by inserting resistors 46, 56 in series with the capacitors 45, 55, the outflow of the pulsed current can also be prevented.

[0033] (Third embodiment) Next, a third embodiment will be described with reference to Fig. 7. The communication device 2 of the third embodiment is different from the first embodiment in that it includes circuits in which diodes 47 and 57 that pass current downstream from the transmission circuit 42 are provided in parallel with the capacitors 45 and 55 in the first embodiment. In other respects, it has the same configuration as the communication device of the first embodiment.

[0034] As in the first embodiment, the communication device 2 of the third embodiment is provided with capacitors 45 and 55, so that even if the voltage of the communication line 34 increases due to an external disturbance, disruption of communication via the communication line 34 can be suppressed.

[0035] Furthermore, in the communication device 2 of the third embodiment, diodes 47, 57 are provided in parallel with the capacitors 45, 55 to pass current downstream from the transmission circuit 42. Therefore, when the first switch 42A is closed and the voltage of the communication line 34 rises on the receiving side from the DC voltage generated by the power supply circuit 41, the capacitors 45, 55 release the stored charge, thereby increasing the voltage of the communication signal flowing through the communication line 34. Therefore, the timing at which the capacitors 45, 55 release the charge can be made appropriate.

[0036] (Fourth embodiment) Next, a fourth embodiment will be described. The communication device 2 of the fourth embodiment differs from the third embodiment in that resistors similar to those of the second embodiment are provided downstream of the circuit in which the capacitors 45, 55 and the diodes 47, 57 are provided in parallel, as viewed from the transmission circuit 42. In other respects, the communication device 2 of the fourth embodiment has the same configuration as the communication device of the third embodiment.

[0037] As in the third embodiment, the communication device 2 of the fourth embodiment can suppress the disruption of communication via the communication line 34 even if the voltage of the communication line 34 rises due to a disturbance, and can appropriately time the capacitors 45, 55 to release electric charge. Furthermore, since the communication device 2 of the fourth embodiment is provided with resistors, it is possible to suppress the peak value of the current flowing through the receiving circuits 43, 53 and the wiring unit 80, and to suppress the occurrence of a large current flowing through the communication line 34.

[0038] Fifth embodiment Next, a fifth embodiment will be described with reference to Fig. 8. The communication device 2 of the fifth embodiment is different from the first embodiment in that a filter, for example, a low-pass filter 90, for suppressing a change in the voltage of the communication line 34 is provided between the communication line 34 and the capacitors 45, 55 in the first embodiment. In other respects, the communication device has the same configuration as the communication device of the first embodiment.

[0039] The low-pass filter 90 includes a resistor 91 and a capacitor 92. The resistor 91 is provided in series with the communication line 34 between the transmitting circuits 42, 52 and the capacitors 45, 55. The capacitor 92 is provided in parallel with the receiving circuits 43, 53. The low-pass filter 90 suppresses changes in the voltage of the communication line 34 of frequency components higher than the communication signal.

[0040] The communication device 2 of the fifth embodiment can suppress the disturbance of the communication via the communication line 34 by the capacitors 45 and 55, similarly to the first embodiment.

[0041] Moreover, leakage of high-frequency noise to the outside can be suppressed by providing a low-pass filter 90 between the transmission circuits 42, 52 and the capacitors 45, 55. Furthermore, by providing the low-pass filter 90, a resistor can be omitted.

[0042] According to at least one of the embodiments described above, a communication device for an air conditioner is configured to include an outdoor unit 10 and one or more indoor units 20 connected by two AC power lines and one communication line, and is equipped with a power supply circuit that generates a DC voltage based on the phase of one of the two AC power lines, and a transmission circuit that varies the voltage of the communication line based on a signal transmitted by a control device that controls the air conditioner, and a circuit in which a diode and a capacitor are connected in parallel is provided between the transmission circuit and the communication line, and the diode is connected in a direction that allows current to flow from the transmission circuit to the communication line, and when the reference potential of the communication line rises, the charge of the capacitor is used to boost the voltage of the communication signal flowing through the communication line, thereby stabilizing communication.

[0043] In each of the above embodiments, the communication device is applied as a communication device between the outdoor unit 10 and the multiple indoor units 20, but it may be applied as a communication device between multiple other devices. For example, the communication device may be applied as a communication device between an indoor unit 20 and another indoor unit 20. In addition, while both the communication devices on the transmitting side and the communication side are configured to be capable of transmitting and receiving, other configurations may also be used. For example, one may have only a transmitting function and the other may have only a receiving function. In addition, one may have only a transmitting function and the other may have a transmitting and receiving function, or one may have a transmitting and receiving function and the other may have only a receiving function.

[0044] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0045] Reference Signs List 1...air conditioner, 2...communication device, 10...outdoor unit, 20...indoor unit, 31...commercial AC power source, 32...first AC power line, 33...second AC power line, 34...communication line, 40...first communication device, 41, 51...power supply circuit, 42, 52...transmitting circuit, 42A, 52A...first switch, 42B, 52B...second switch, 43, 53...receiving circuit, 45, 55, 92...capacitor, 46, 56, 91...resistor, 47, 57...diode, 50...second communication device, 60...first air conditioning circuit, 70...second air conditioning circuit, 80...wiring section, 81 to 86...wiring, 90...low-pass filter, L, L', N, N'S, S'...connecting terminal

Claims

1. A communication device for an air conditioner that is composed of a plurality of devices connected by two AC power lines and one communication line, a power supply circuit that generates a DC voltage based on one of the phases of the two AC power supply lines; a transmission circuit that varies a voltage of the communication line based on a signal transmitted by a control device that controls the air conditioner; a capacitor is connected between the transmission circuit and the communication line; a communication device for an air conditioner, comprising: a communication circuit for increasing a voltage of a communication signal flowing through the communication line by using the charge of the capacitor when a reference potential of the communication line increases;

2. A resistor is inserted in series with the capacitor, a terminal of the capacitor or a terminal of the resistor is connected to the communication line; A communication device for an air conditioner according to claim 1.

3. A communication device for an air conditioner including an outdoor unit and one or more indoor units connected by two AC power lines and one communication line, a power supply circuit that generates a DC voltage based on one of the phases of the two AC power supply lines; A transmission circuit that varies a voltage of the communication line based on a signal transmitted by a control device that controls the air conditioner, a circuit in which a diode and a capacitor are connected in parallel is provided between the transmission circuit and the communication line; the diode is connected in a direction to pass a current from the transmission circuit to the communication line, a communication device for an air conditioner, comprising: a communication circuit for increasing a voltage of a communication signal flowing through the communication line by using the charge of the capacitor when a reference potential of the communication line increases;

4. a receiving circuit that reads a voltage fluctuation of the communication line and transmits a signal corresponding to the voltage fluctuation to the control device; The communication device for an air conditioner according to claim 1 or 3.

5. a resistor is inserted in series with the circuit in which the diode and the capacitor are connected in parallel; The communication device for an air conditioner according to claim 3.

6. a filter for suppressing a change in the voltage of the communication line is inserted between the communication line and the capacitor; A communication device for an air conditioner according to claim 1.

7. The plurality of devices are an outdoor unit and one or more indoor units. A communication device for an air conditioner according to claim 1.

8. The plurality of devices are a plurality of indoor units, A communication device for an air conditioner according to claim 1.

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