Current loop communication circuit and air conditioning

Abstract

The present invention discloses a current loop communication circuit and an air conditioner. The current loop communication circuit includes: a first communication circuit and a second communication circuit. The first communication circuit and the second communication circuit share a neutral line N. The first communication circuit and the second communication circuit are connected to a communication S line for communication, and a discharge circuit is provided between the communication S line and the neutral line N. The discharge circuit eliminates the parasitic capacitance generated between the communication S line and the neutral line N. When the first communication circuit and the second communication circuit are connected, the present invention realizes high-level signal transmission between the two; when the first communication circuit sends a low-level signal to the second communication circuit, the parasitic capacitance is eliminated, thereby reducing the limitation of the current loop communication circuit on the length of the connection line and increasing the communication distance. At the same time, when the second communication circuit sends a low-level signal to the first communication circuit, a power supply boost control method is adopted to pull the communication S line voltage up to the power supply voltage to ensure the stability of the communication S line voltage.

Description

Technical Field

[0001] The present invention relates to the field of communications, in particular to a current loop communication circuit and an air conditioner. Background Art

[0002] Currently, communication between indoor and outdoor units of household air conditioners is typically achieved using a current loop communication circuit. This circuit utilizes three wires: the live and neutral wires (L and N) of the AC power supply, plus a communication wire (S). These three wires form a current loop communication circuit, enabling communication between the indoor and outdoor units. This circuit utilizes fewer wires and is cost-effective.

[0003] Among them, the current loop communication needs to share the neutral line N with the power circuit, and in the actual installation and use process, the communication S line and the power line are often run in parallel. The parallel running will generate parasitic capacitance, which in turn affects the communication quality. For the same type of wire, when the connecting line is short, the parasitic capacitance is small, and the charging and discharging of the parasitic capacitance has little effect on the level of the current loop communication S line; as the connecting line is gradually lengthened, the parasitic capacitance also increases, the stored energy will also increase, and the impact of charging and discharging on the level of the communication S line will also increase; when the connecting line is added to a certain length, the level fluctuation caused by the charging and discharging of the parasitic capacitance will interfere with the transmission of the effective level on the communication S line, thereby causing communication failure. Therefore, the communication distance of the current loop communication circuit in the existing technology is relatively short, usually only 30m-50m. Summary of the Invention

[0004] In order to solve the technical problem in the prior art that parasitic capacitance exists when the power line and the communication line are run in parallel, resulting in a short communication line distance, the present invention proposes a current loop communication circuit and an air conditioner.

[0005] The technical solution adopted in the present invention is:

[0006] The present invention proposes a current loop communication circuit and an air conditioner. The current loop communication circuit includes: a first communication circuit and a second communication circuit. The first communication circuit and the second communication circuit share a neutral line N. The first communication circuit and the second communication circuit are connected to a communication S line for communication; in particular, a discharge circuit is provided between the communication S line and the neutral line N, and the discharge circuit eliminates parasitic capacitance between the communication S line and the neutral line N.

[0007] Furthermore, when the first communication circuit and the second communication circuit are connected, the discharge circuit does not work; when the first communication circuit and the second communication circuit are disconnected, the discharge circuit works.

[0008] Furthermore, the discharge circuit includes: a forward discharge circuit and a reverse discharge circuit; when the voltage of the communication S line is greater than the voltage of the neutral line N, the forward discharge circuit works; otherwise, the reverse discharge circuit works.

[0009] In one embodiment, when the voltage sent by the signal sending end of the first communication circuit or the second communication circuit is higher than or equal to a set high voltage value, current is connected between the first communication circuit and the second communication circuit and flows through the current; when the voltage sent by the signal sending end of the first communication circuit or the second communication circuit is lower than or equal to a set low voltage value, current is interrupted between the first communication circuit and the second communication circuit and no current flows through the current.

[0010] Furthermore, the current loop communication circuit also includes: a first power loop and a second power loop sharing a live wire L; the first power loop is connected to the first communication circuit to supply power to the first communication circuit; the second power loop is connected to the second communication circuit to supply power to the second communication circuit.

[0011] In one embodiment, a pull-up circuit is provided between the second power supply loop and the second communication circuit; when the voltage output by the second communication circuit is lower than or equal to a set low voltage value, the pull-up circuit works to pull up the voltage of the communication S line to the output voltage of the second power supply loop, thereby fixing the voltage of the communication S line unchanged.

[0012] In one embodiment, the forward discharge circuit includes: a resistor R14 and a photocoupler PC11; one end of the resistor R14 is connected to the communication S line, and the other end is connected to the collector of the photocoupler PC11, the emitter of the photocoupler PC11 is connected to the neutral line N, and the light-emitting diode of the photocoupler PC11 is connected to the signal sending end of the first communication circuit.

[0013] In one embodiment, the reverse discharge circuit includes: a diode D5; an anode of the diode D5 is connected to the neutral line N, and a cathode of the diode D5 is connected to the communication S line.

[0014] In one embodiment, the pull-up circuit includes: a photocoupler PC21; the collector of the photocoupler PC21 is connected to the output end of the second power supply loop, the emitter of the photocoupler PC21 is connected to the communication S line, and the light-emitting diode of the photocoupler PC21 is connected to the signal sending end of the second communication circuit.

[0015] In one embodiment, the first communication circuit includes: a photocoupler PC10, a photocoupler PC12, a diode D4, a resistor R13, a resistor R2, and a diode D6; the collector of the transistor of the photocoupler PC10 is connected to the first power supply loop, the emitter of the transistor of the photocoupler PC10 is connected to the anode of the light-emitting diode of the photocoupler PC12, the cathode of the light-emitting diode of the photocoupler PC12 is connected in series with the resistor R2 and the anode of the diode D6, and the anode of the diode D4 is connected to the cathode of the light-emitting diode of the photocoupler PC12, the cathode of the diode D4 is connected to the anode of the light-emitting diode of the photocoupler PC12, and the resistor R13 is connected in parallel to both ends of the diode D4.

[0016] In one embodiment, the second communication circuit includes: a photocoupler PC20, a photocoupler PC22, a diode D9, a resistor R20, a diode D8, a resistor R15, and a resistor R17; the collector of the photocoupler PC20 is connected in series with the resistor R15 and the cathode of the diode D8 in sequence; one end of the resistor R17 is connected between the resistor R15 and the collector of the photocoupler PC20, and the other end is connected to the emitter of the photocoupler PC20; the emitter of the photocoupler PC20 is connected to the anode of the light-emitting diode of the photocoupler PC22; the cathode of the light-emitting diode of the photocoupler PC22 is connected to the neutral line N; the anode of the diode D9 is connected to the cathode of the light-emitting diode of the photocoupler PC22; the cathode of the diode D9 is connected to the anode of the light-emitting diode of the photocoupler PC22; and the resistor R20 is connected in parallel with both ends of the diode D9.

[0017] In one embodiment, when the voltage sent by the signal sending end of the first communication circuit is higher than or equal to the set high voltage value, the photoelectric coupler PC10 and the photoelectric coupler PC22 are turned on; when the voltage sent by the signal sending end of the second communication circuit is higher than or equal to the set high voltage value, the photoelectric coupler PC20, the photoelectric coupler PC10, and the photoelectric coupler PC12 are turned on.

[0018] An air conditioner includes: an indoor unit provided with the first communication circuit, and an outdoor unit provided with the second communication circuit, wherein the indoor unit and the outdoor unit communicate with each other using the current loop communication circuit described above.

[0019] In one embodiment, when the voltage sent by the indoor unit is lower than or equal to the set low voltage value, the outdoor unit receives a low level signal; when the voltage sent by the indoor unit is higher than or equal to the set high voltage value, the outdoor unit receives a high level signal; when the voltage sent by the outdoor unit is lower than or equal to the set low voltage value, the indoor unit receives a low level signal; when the voltage sent by the outdoor unit is higher than or equal to the set high voltage value, the indoor unit receives a high level signal.

[0020] Compared to existing technologies, the present invention implements dual-loop control: when the first and second communication circuits are performing high-level transmission, the first and second communication circuits are connected, forming a communication loop and enabling high-level signal transmission between them. When the first communication circuit sends a low-level signal to the second communication circuit, parasitic capacitance is eliminated, increasing the communication distance. Furthermore, the present invention employs a power supply boost control method. When the second communication circuit sends a low-level signal to the first communication circuit, the voltage on the communication line S is pulled up to the power supply voltage, ensuring the stability of the voltage on the communication line S. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0023] Figure 2 Schematic diagram of the overall structure of an embodiment of the present invention;

[0024] Figures 3 to 5 is a specific circuit diagram in an embodiment of the present invention;

[0025] Figure 6 FIG. 4 is a specific circuit diagram of another embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] Because industrial control applications often involve accurate long-distance transmission of data or control signals, using current as a carrier for data transmission can increase the signal's noise tolerance and improve its resistance to attenuation. Current loop communication circuits, which carry signals on a current loop to achieve long-distance signal transmission, often share a common line with the neutral line of the AC power supply, forming a common-zero current loop communication circuit. Due to their inherent advantages, current loop communication circuits are widely used. In existing technology, air conditioner indoor and outdoor units often communicate using a common-zero current loop communication circuit due to their long distance.

[0028] In order to facilitate understanding of the principles of the present invention, the current loop communication circuit proposed in the present invention is applied to the communication scenario between the indoor unit and the outdoor unit of the air conditioner, and the present invention is explained in conjunction with this usage scenario. However, this usage scenario is not a limitation of the present invention, and the current loop communication circuit proposed in the present invention can also be applied to other situations.

[0029] Communication between the indoor and outdoor air conditioner units is typically achieved using a current loop communication circuit. This circuit utilizes three wires: the live (L) and neutral (N) wires of the AC power supply, plus a communication line. However, because the current loop communication circuit shares the neutral line (N) with the power supply circuit, and during actual installation and use, the communication line (S) and the power line are often routed in parallel, this parallel routing creates parasitic capacitance, which reduces communication distance.

[0030] In order to solve the problem in the prior art that the parasitic capacitance generated by the parallel running of the neutral line N and the communication line S affects the communication distance, the present invention proposes a current loop communication circuit.

[0031] The principle and structure of the present invention are described in detail below with reference to the accompanying drawings and embodiments.

[0032] The present invention proposes a current loop communication circuit, such as Figure 1 As shown, it includes: a first communication circuit and a second communication circuit, and the first communication circuit and the second communication circuit are connected with an AC power live wire L, a neutral wire N, and a communication S wire, so as to realize communication. At the same time, a discharge circuit is connected between the neutral wire N and the communication S wire. When the first communication circuit and the second communication circuit are connected, the communication circuit has a large effective communication current, a strong anti-interference ability, and is less affected by parasitic capacitance, so the discharge circuit does not work; when the first communication circuit and the second communication circuit are interrupted, the voltage between the communication S wire and the neutral wire N is affected by the voltage fluctuation of the power line live wire L, and the discharge circuit works. The current loop communication circuit proposed by the present invention eliminates the parasitic capacitance generated between the communication S wire and the neutral wire N, improves the communication quality, and increases the communication distance.

[0033] like Figure 2As shown, in this embodiment, specifically, the first communication circuit is connected to a first power loop, and the second communication circuit is connected to a second power loop. The first and second power loops share a neutral line N and a live line L, thereby powering the first and second communication circuits. Furthermore, a communication S line is connected between the first and second communication circuits, thereby forming a complete circuit loop comprising the first and second communication circuits, the first and second power loops. Furthermore, the first and second power loops share a neutral line N, and a discharge circuit is connected between the communication S line and the neutral line N. Because the first and second communication circuits implement long-distance communication, the provision of a first and second power loops, respectively, to power the first and second communication circuits meets actual needs and usage, facilitating communication control.

[0034] In the present invention, the discharge circuit is specifically configured as: a forward discharge circuit and a reverse discharge circuit. If the voltage of the communication S line is higher than the voltage of the neutral line N, the forward discharge circuit operates to equalize the voltage of the communication S line with the voltage of the neutral line N; if the voltage of the communication S line is lower than the voltage of the neutral line N, the reverse discharge circuit operates to equalize the voltage of the communication S line with the voltage of the neutral line. The design of two unidirectional discharge circuits is highly reliable and practical, and can more accurately and quickly detect whether a discharge circuit has failed. If one of the discharge circuits fails, because the other discharge circuit can still be used, when only one discharge circuit is working for a long time, a prompt can be given to the user, reminding the user to conduct a test and eliminate the fault in time.

[0035] According to the specific functions and requirements of the above-mentioned current loop circuit, the present invention designs a specific circuit that is simple and convenient for practical use.

[0036] like Figure 3 As shown, the first communication circuit includes: a photoelectric coupler PC10, a photoelectric coupler PC12, a diode D4, a resistor R13, a resistor R2, and a diode D6; the collector of the transistor of the photoelectric coupler PC10 is connected to the first power supply loop, the emitter of the transistor of the photoelectric coupler PC10 is connected to the positive electrode of the light-emitting diode of the photoelectric coupler PC12, the negative electrode of the light-emitting diode of the photoelectric coupler PC12 is connected in series with the resistor R2 and the positive electrode of the diode D6 in sequence, and the positive electrode of the diode D4 is connected to the negative electrode of the light-emitting diode of the photoelectric coupler PC12, the negative electrode of the diode D4 is connected to the positive electrode of the light-emitting diode of the photoelectric coupler PC12, and the resistor R13 is connected in parallel to both ends of the diode D4.

[0037] like Figure 3As shown, the second communication circuit includes: a photocoupler PC20, a photocoupler PC22, a diode D9, a resistor R20, a diode D8, a resistor R15, and a resistor R17; the collector of the photocoupler PC20 is connected in series with the resistor R15 and the cathode of the diode D8 in sequence, one end of the resistor R17 is connected between the resistor R15 and the collector of the photocoupler PC20, and the other end is connected to the emitter of the photocoupler PC20, the emitter of the photocoupler PC20 is connected to the anode of the light-emitting diode of the photocoupler PC22, the cathode of the light-emitting diode of the photocoupler PC22 is connected to the neutral line N, and the anode of the diode D9 is connected to the cathode of the light-emitting diode of the photocoupler PC22, the cathode of the diode D9 is connected to the anode of the light-emitting diode of the photocoupler PC22, and the resistor R20 is connected in parallel with both ends of the diode D9.

[0038] A communication S line is connected between the cathode of the diode D6 and the anode of the diode D8, so that the first communication circuit is connected to the indoor unit communication circuit to form a complete loop.

[0039] like Figure 4 As shown, the forward discharge circuit includes: a parasitic capacitor C2 generated between the communication S line and the neutral line N, a resistor R14, and a photocoupler PC11; the reverse discharge circuit includes: a parasitic capacitor C2 and a diode D5; one end of the resistor R14 is connected to the communication S line, and the other end is connected to the collector of the photocoupler PC11, the emitter of the photocoupler PC11 is connected to the neutral line N, the cathode of the diode D5 is connected to the communication S line, and the anode of the diode D5 is connected to the neutral line N.

[0040] At the same time, if Figure 5 As shown, in this embodiment, the first power supply loop includes: resistor R1, diode D1, capacitor C1, resistor R4, diode D2, and clamping diode D3; the second power supply loop includes: resistor R27, diode D10, capacitor C3, resistor R26, diode D12, and clamping diode D11; one end of the resistor R1 is connected to the live wire L, and the other end is connected to the positive electrode of the diode D1; the capacitor C1, resistor R4, diode D2, and clamping diode D3 are connected in parallel as a whole, and one end is connected to the negative electrode of the diode D1, and the other end is connected to the neutral line N, and specifically, the negative electrodes of the diode D2 and the clamping diode D3 are connected to the negative electrode of the diode D1, and the positive electrodes of the diode D2 and the clamping diode D3 are connected to the neutral line N. One end of the resistor R27 is connected to the live wire L, and the other end is connected to the anode of the diode D10; the capacitor C3, the resistor R26, the diode D12, and the clamping diode D11 are connected in parallel as a whole, and one end is connected to the cathode of the diode D10, and the other end is connected to the neutral wire N. Specifically, the cathodes of the diode D12 and the clamping diode D11 are connected to the cathode of the diode D10, and the anodes of the diode D12 and the clamping diode D11 are connected to the neutral wire N.

[0041] Because the first power supply loop supplies power to the first communication circuit, the collector of the transistor of the photocoupler PC10 is connected to the capacitor C1, and the connection is between the capacitor C1 and the diode D1. Similarly, the second power supply loop supplies power to the second communication circuit, and a photocoupler PC21 is connected between the second power supply loop and the second communication circuit. The collector of the transistor of the photocoupler PC21 is connected between the capacitor C3 and the diode D10, and the emitter of the photocoupler PC21 is connected to the anode of the diode D8. When the second communication circuit is operating, the photocoupler PC21 is kept conductive, so that the second power supply loop can supply power to the second communication circuit.

[0042] At the same time, considering the practicality of the circuit, it is necessary to design corresponding control circuits at the signal sending end and the signal receiving end of the first communication circuit and the second communication circuit. In actual use, the communication between the first communication circuit and the second communication circuit is achieved by controlling the control circuit. Figure 3 As shown, in this embodiment, specifically:

[0043] The signal transmitting terminal TX of the first communication circuit simultaneously controls the photocouplers PC10 and PC11, while the signal receiving terminal RX is connected to the photocoupler PC12. The anode of the light-emitting diode of the photocoupler PC10 is connected to resistor R3 and VCC in sequence, the cathode of the light-emitting diode of the photocoupler PC10 is connected to the collector of the switching tube Q1, the base of the switching tube Q1 is connected to resistor R5, which is in turn connected to the signal transmitting terminal TX, and the emitter of the switching tube Q1 is grounded. The anode of the light-emitting diode of the photocoupler PC11 is connected to the collector of the switching tube Q2, the base of the switching tube Q2 is connected to resistor R7, which is connected to the signal transmitting terminal. Resistor R8 is connected between the base and emitter of the switching tube Q2, and the emitter of the switching tube Q2 is connected to VCC. The cathode of the light-emitting diode of the photocoupler PC11 is connected to resistor R9 and then to ground. The collector of the transistor of photocoupler PC12 is connected to the signal receiving terminal. The collector of the transistor of photocoupler PC12 is also connected to resistor R11. The other end of resistor R11 is connected to VCC. The emitter of photocoupler PC12 is grounded. Switch Q1 is an NPN transistor, and switch Q2 is a PNP transistor.

[0044] The signal transmitting terminal TXD of the second communication circuit simultaneously controls optocouplers PC21 and PC20, while the signal receiving terminal RXD is connected to optocoupler PC22. The anode of the light-emitting diode of optocoupler PC21 is connected to the collector of switching tube Q4, the base of switching tube Q4 is connected to resistor R24, the other end of resistor R24 is connected to the signal transmitting terminal TXD, the emitter of switching tube Q4 is connected to VCC, and resistor R23 is connected between the emitter and base of switching tube Q4. The cathode of the light-emitting diode of optocoupler PC21 is connected to resistor R25 and then to ground. The anode of the light-emitting diode of optocoupler PC20 is connected to resistor R16 and then to VCC, the cathode of the light-emitting diode of optocoupler PC20 is connected to the collector of switching tube Q3, the base of switching tube Q3 is connected to resistor R18, the other end of resistor R18 is connected to the signal transmitting terminal TXD, and the emitter of switching tube Q3 is grounded. The emitter of the transistor of photocoupler PC22 is grounded, and the collector of the transistor of photocoupler PC22 is connected to the signal receiving terminal RXD. The collector of photocoupler PC22 is also connected to resistor R21, and the other end of resistor R21 is connected to VCC. Switch Q3 is an NPN transistor, and switch Q4 is a PNP transistor.

[0045] The above is a specific circuit. The communication principle is explained below in combination with the specific circuit.

[0046] First, it should be clarified that in this embodiment, the current loop communication circuit transmits digital signals. According to the design of this embodiment, the voltage value of VCC is set to a set high voltage value. When the voltage values of the signal transmitting terminal TX, the signal transmitting terminal TXD, the signal receiving terminal RX, and the signal receiving terminal RXD are higher than or equal to the set high voltage value, they are high-level signals. The voltage value 0 is set to a set low voltage value. When the voltage values of the signal transmitting terminal TX, the signal transmitting terminal TXD, the signal receiving terminal RX, and the signal receiving terminal RXD are lower than or equal to the set low voltage value, they are low-level signals. Digital signal transmission simplifies the control of the current loop communication circuit and prevents components in the circuit from being mis-conducted when the input voltage is between the set high voltage value and the set low voltage value.

[0047] When the signal transmitting end TX of the first communication circuit sends a high-level signal, the switch tube Q1 is turned on and the switch tube Q2 is turned off, thereby turning on the photoelectric coupler PC10 and turning off the photoelectric coupler PC11. At the same time, the signal transmitting end of the second communication circuit is controlled to maintain a high level, controlling the photoelectric coupler PC20 to remain in the on state. (When the photoelectric coupler PC20 is turned on, the resistor R17 is short-circuited, increasing the current of the current loop communication circuit to meet the conduction voltage drop of the light-emitting diode of the photoelectric coupler PC22. At the same time, when the photoelectric coupler PC20 is turned off, the resistor R17 can protect the circuit in the event that the communication S line is misinterpreted as the live line L). At this time, the second communication circuit and the first communication circuit are connected, forming a communication loop. The communication current starts from capacitor C1, flows through photoelectric coupler PC10, photoelectric coupler PC12, resistor R2, and diode D6 in sequence, and then flows along the communication S line into diode D8, resistor R15, and photoelectric coupler PC20 of the second communication circuit and then returns to the neutral line N. Therefore, the signal receiving end RXD of the second communication circuit can receive a high-level signal, realizing signal transmission between the first communication circuit and the second communication circuit.

[0048] At the same time, when the signal transmitting terminal TX of the first communication circuit sends a high-level signal, the second communication circuit and the first communication circuit form a conductive communication loop. The circuit current is relatively large, and the impact of the voltage fluctuation of the live line L on the communication level is almost negligible. Therefore, at this time, the forward discharge circuit and the reverse discharge circuit are inoperative.

[0049] When the signal transmitting end TX of the first communication circuit sends a low-level signal, the switch tube Q2 is turned on and the switch tube Q1 is turned off, thereby turning off the photoelectric coupler PC10 and turning on the photoelectric coupler PC11. At the same time, the signal transmitting end TXD of the second communication circuit is controlled to maintain a high level to control the photoelectric coupler PC20 to remain in the on state (because the present invention transmits high and low level signals, if the photoelectric coupler PC20 is not controlled to be turned on, the signal transmitting end TXD will be a low-level signal, causing the photoelectric coupler PC21 to be turned on, thereby pulling the voltage of the communication S line to the voltage of the capacitor C3, affecting communication). At this time, the first communication circuit and the second communication circuit are interrupted, and the receiving end RXD of the second communication circuit receives a low-level signal.

[0050] When the signal transmitting end TX of the first communication circuit sends a low-level signal, if the parasitic capacitor C2 is in a charging state due to the voltage fluctuation of the live wire L of the power line, at this time the voltage of the communication S line is higher than the voltage of the neutral wire N, the forward discharge circuit is conductive, and the parasitic capacitor C2 can be discharged through the forward discharge circuit. The current starts from the communication S line, flows through the resistor R14 and the photocoupler PC11 in sequence, and then returns to the neutral wire N until the voltage of the communication S line and the voltage of the neutral wire N are equal, and the forward discharge circuit is disconnected. If the parasitic capacitor C2 is in a discharging state due to the voltage fluctuation of the live wire L of the power line, at this time the voltage of the communication S line is lower than the voltage of the neutral wire N, the reverse discharge circuit is conductive, and the parasitic capacitor C2 can be discharged through the reverse discharge circuit. The current starts from the neutral wire N, flows through the diode D5, and then returns to the communication S line until the voltage of the communication S line and the voltage of the neutral wire N are equal, and the reverse discharge circuit is disconnected.

[0051] When the signal transmitting terminal TXD of the second communication circuit sends a high-level signal, switch Q3 turns on and switch Q4 turns off, thereby turning on photocoupler PC20 and turning off photocoupler PC21. Simultaneously, the signal transmitting terminal TX of the first communication circuit outputs a high-level signal, controlling the photocoupler PC10 to turn on. At this point, the second communication circuit and the first communication circuit are connected, forming a communication loop. Level signals can be transmitted between photocoupler PC10, photocoupler PC12, resistor R2, diode D6, communication S-line, diode D8, resistor R15, and photocoupler PC20, allowing the signal receiving terminal RX of the first communication circuit to receive the high-level signal. In other words, signal transmission and information transmission are achieved between the second communication circuit and the first communication circuit.

[0052] At the same time, when the signal transmitting terminal TXD of the second communication circuit sends a high-level signal, the first communication circuit and the second communication circuit form a conductive communication loop. The circuit current is large, and the impact of the voltage fluctuation of the live line L on the communication level is almost negligible. Therefore, at this time, the forward discharge circuit and the reverse discharge circuit are inoperative.

[0053] When the signal transmitting terminal TXD of the second communication circuit sends a low-level signal, switch Q3 turns off and switch Q4 turns on, thereby turning on photocoupler PC21 and disconnecting photocoupler PC20. Simultaneously, the signal transmitting terminal TX of the first communication circuit outputs a high-level signal, turning on photocoupler PC10. At this point, a conductive loop cannot be formed between the second and first communication circuits, and the receiving terminal RX of the first communication circuit receives a low-level signal.

[0054] When the signal transmitting terminal TXD of the second communication circuit sends a low level signal, the parasitic capacitor C2 will be affected by the voltage fluctuation of the power line live wire L and will be in a charge-discharge state. However, since the photoelectric coupler PC11 is disconnected at this time, the forward discharge circuit does not work, and the influence of the parasitic capacitor C2 voltage cannot be eliminated. In view of this problem, the present invention has designed a pull-up circuit, namely the photoelectric coupler PC21. Because the signal transmitting terminal TXD of the second communication circuit sends a low level signal, the photoelectric coupler PC21 is turned on, so the voltage of the communication S line will be pulled up to the voltage of the capacitor C3. At this time, the voltage of the communication S line is fixed to the voltage of the capacitor C3, so that the voltage of the communication S line is no longer affected by the charge and discharge of the parasitic capacitor C2. In this case, the voltage of the communication S line is greater than the voltage of the zero line N. Even if the forward discharge circuit and the reverse discharge circuit are not working at this time, the communication process will not be affected, thereby providing the anti-interference ability of the communication. At the same time, because the photocoupler PC10 is also turned on at this time, the photocoupler PC12 may be mis-turned on. To prevent this from happening, the voltage of capacitor C3 must be no lower than the voltage of capacitor C1 when designing the circuit parameters.

[0055] In summary, first, the present invention achieves dual-loop control compared to the prior art: when the first communication circuit and the second communication circuit are performing high-level transmission, the first communication circuit and the second communication circuit are connected to form a communication loop, thereby achieving high-level signal transmission between the two; when the first communication circuit sends a low-level signal to the second communication circuit, the voltage generated by the parasitic capacitor C2 is eliminated, reducing the limitation of the connection line length on the current loop communication and increasing the communication distance. Second, the present invention adopts a power boost control method. When the second communication circuit sends a low-level signal to the first communication circuit, an optocoupler is used to pull the communication S line to the power supply voltage to ensure the stability of the communication S line level.

[0056] The present invention also provides an air conditioner comprising an indoor unit and an outdoor unit. The signal receiving end and signal transmitting end of a second communication circuit are connected to the indoor unit, and the signal receiving end and signal transmitting end of a first communication circuit are connected to the outdoor unit. Thus, the indoor and outdoor units transmit signals via a current loop communication circuit. When the indoor unit transmits a low-level signal, the outdoor unit receives a low-level signal; when the indoor unit transmits a high-level signal, the outdoor unit receives a high-level signal. When the outdoor unit transmits a low-level signal, the indoor unit receives a low-level signal; when the outdoor unit transmits a high-level signal, the indoor unit receives a high-level signal.

[0057] In another embodiment, Figure 3The diode D5 in the circuit can be directly eliminated. In this embodiment, the reverse discharge circuit is eliminated, and the neutral line N cannot discharge to the communication line S through the diode D5. However, in actual use, it does not affect communication. It only causes the waveform of the low-level communication to have a negative value, which is not conducive to the analysis and processing of data during the test verification process. The circuit diagram after the change is as follows: Figure 6 In other embodiments, the switches Q1-Q4 can be replaced by MOSFET transistors or other switch devices that also have a switch control function, and the photoelectric coupler can also be replaced by any photoelectric isolation device.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. Current loop communication circuit, including: a first communication circuit and a second communication circuit, wherein the first communication circuit and the second communication circuit share a neutral line N, and the first communication circuit and the second communication circuit are connected to a communication S line for communication; characterized in that the first communication circuit further comprises: a first power loop and a second power loop sharing a live line L; the first power loop is connected to the first communication circuit to supply power to the first communication circuit; the second power loop is connected to the second communication circuit to supply power to the second communication circuit, and a pull-up circuit is provided between the second power loop and the second communication circuit; a discharge circuit is provided between the communication S line and the neutral line N, and the discharge circuit eliminates the parasitic capacitance between the communication S line and the neutral line N; The discharge circuit includes: a forward discharge circuit and a reverse discharge circuit; when the signal transmitting end TX of the first communication circuit sends a low-level signal, if the voltage of the communication S line is higher than the voltage of the neutral line N, the forward discharge circuit is turned on; if the voltage of the communication S line is lower than the voltage of the neutral line N, the reverse discharge circuit is turned on; When the signal transmitting terminal TXD of the second communication circuit sends a low level signal, the pull-up circuit works to pull up the voltage of the communication S line to the output voltage of the second power supply loop, fixing the voltage of the communication S line unchanged.

2. The current loop communication circuit according to claim 1, wherein: When the voltage sent by the signal sending end of the first communication circuit or the second communication circuit is higher than or equal to the set high voltage value, current flows between the first communication circuit and the second communication circuit; when the voltage sent by the signal sending end of the first communication circuit or the second communication circuit is lower than or equal to the set low voltage value, current is interrupted and no current flows between the first communication circuit and the second communication circuit.

3. The current loop communication circuit according to claim 1, wherein: The forward discharge circuit includes: a resistor R14 and a photoelectric coupler PC11; one end of the resistor R14 is connected to the communication S line, and the other end is connected to the collector of the photoelectric coupler PC11, the emitter of the photoelectric coupler PC11 is connected to the neutral line N, and the light-emitting diode of the photoelectric coupler PC11 is connected to the signal sending end of the first communication circuit.

4. The current loop communication circuit according to claim 1, wherein: The reverse discharge circuit includes: a diode D5; the anode of the diode D5 is connected to the neutral line N, and the cathode of the diode D5 is connected to the communication S line.

5. The current loop communication circuit according to claim 1, wherein: The pull-up circuit includes: a photocoupler PC21; the collector of the photocoupler PC21 is connected to the output end of the second power supply loop, the emitter of the photocoupler PC21 is connected to the communication S line, and the light-emitting diode of the photocoupler PC21 is connected to the signal sending end of the second communication circuit.

6. The current loop communication circuit according to claim 2, wherein: The first communication circuit includes: a photoelectric coupler PC10, a photoelectric coupler PC12, a diode D4, a resistor R13, a resistor R2, and a diode D6; the cathode of the light-emitting diode of the photoelectric coupler PC10 is connected to the signal sending end of the first communication circuit, and the collector of the transistor of the photoelectric coupler PC12 is connected to the signal receiving end of the first communication circuit; the collector of the transistor of the photoelectric coupler PC10 is connected to the first power supply loop, the emitter of the transistor of the photoelectric coupler PC10 is connected to the anode of the light-emitting diode of the photoelectric coupler PC12, the cathode of the light-emitting diode of the photoelectric coupler PC12 is connected in series with the resistor R2 and the anode of the diode D6, and the anode of the diode D4 is connected to the cathode of the light-emitting diode of the photoelectric coupler PC12, the cathode of the diode D4 is connected to the anode of the light-emitting diode of the photoelectric coupler PC12, the resistor R13 is connected in parallel to both ends of the diode D4, and the emitter of the transistor of the photoelectric coupler PC12 is grounded.

7. The current loop communication circuit according to claim 6, wherein: The second communication circuit includes: a photocoupler PC20, a photocoupler PC22, a diode D9, a resistor R20, a diode D8, a resistor R15, and a resistor R17; the cathode of the light-emitting diode of the photocoupler PC20 is connected to the signal sending end of the second communication circuit, and the collector of the transistor of the photocoupler PC22 is connected to the signal receiving end of the second communication circuit; the collector of the photocoupler PC20 is connected in series with the resistor R15 and the cathode of the diode D8 in sequence, one end of the resistor R17 is connected between the resistor R15 and the collector of the photocoupler PC20, and the other end is connected to the collector of the photocoupler PC20. The emitter of the photocoupler PC20 is connected to the anode of the light-emitting diode of the photocoupler PC22, and the cathode of the light-emitting diode of the photocoupler PC22 is connected to the neutral line N. At the same time, the anode of the diode D9 is connected to the cathode of the light-emitting diode of the photocoupler PC22, and the cathode of the diode D9 is connected to the anode of the light-emitting diode of the photocoupler PC22. The resistor R20 is connected in parallel at both ends of the diode D9, and the emitter of the transistor of the photocoupler PC22 is grounded.

8. The current loop communication circuit according to claim 7, wherein: When the voltage sent by the signal sending end of the first communication circuit is higher than or equal to the set high voltage value, the photoelectric coupler PC10 and the photoelectric coupler PC22 are turned on; when the voltage sent by the signal sending end of the second communication circuit is higher than or equal to the set high voltage value, the photoelectric coupler PC20, the photoelectric coupler PC10, and the photoelectric coupler PC12 are turned on.

9. Air conditioning, including: An indoor unit provided with the first communication circuit and an outdoor unit provided with the second communication circuit are characterized in that the indoor unit and the outdoor unit communicate using the current loop communication circuit described in any one of claims 1-8.

10. The air conditioner according to claim 9, wherein When the voltage sent by the indoor unit is lower than or equal to the set low voltage value, the outdoor unit receives a low level signal; when the voltage sent by the indoor unit is higher than or equal to the set high voltage value, the outdoor unit receives a high level signal; when the voltage sent by the outdoor unit is lower than or equal to the set low voltage value, the indoor unit receives a low level signal; when the voltage sent by the outdoor unit is higher than or equal to the set high voltage value, the indoor unit receives a high level signal.

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