Signal output circuit and air conditioner

Abstract

The utility model discloses a signal output circuit and an air conditioner, and the signal output circuit comprises a filter circuit, the input end of which is used for being electrically connected with a controller, and the filter circuit is used for accessing a driving signal with a corresponding duty ratio output by the controller and outputting the driving signal after filtering processing; the first input end of the operational amplifier circuit and the output end of the filter circuit are connected with a feedback resistor and are connected in series between the second input end of the operational amplifier circuit and the ground; the gain control network is used for accessing the controller and is electrically connected with the output interface, the second input end of the operational amplifier circuit and the output end of the operational amplifier circuit, and the gain control network is further used for forming different gain loops with the feedback resistor under the control of the controller; the operational amplifier circuit is used for converting the filtered driving signal under the control of the gain loop and outputting a control signal corresponding to a current value or a voltage value to the output interface; according to the technical scheme, the compatibility of the output interface of the air conditioner is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of air conditioners, in particular to a signal output circuit and an air conditioner. Background Art

[0002] At present, in the air-conditioning control circuit, an output interface is reserved for connecting to functional loads, wherein the output interface will output different control signals to drive the load according to its model. According to the different control signals, the output interface is divided into two types: current type (such as 0-20mA) and voltage type control signal (such as 0-10V). This will require the microcontroller to set up peripheral circuits separately for conversion when outputting through the output interface, resulting in a waste of the microcontroller I / O port. Utility Model Content

[0003] The main purpose of the utility model is to provide a signal output circuit and an air conditioner, aiming to improve the compatibility of the output interface of the air conditioner.

[0004] To achieve the above-mentioned purpose, the signal output circuit proposed in the present invention is applied to an air conditioner. The air conditioner includes an output interface and a controller. The signal output circuit includes:

[0005] A filter circuit, whose input end is used to connect to the controller, and the filter circuit is further used to filter the driving signal with adjustable duty cycle output by the controller into a stable driving voltage output;

[0006] an operational amplifier circuit, a first input terminal of which is connected to the output terminal of the filter circuit;

[0007] a feedback resistor connected in series between the second input terminal of the operational amplifier circuit and ground;

[0008] a gain control network, adapted to be connected to the controller and electrically connected to the output interface, the second input terminal of the operational amplifier circuit, and the output terminal thereof, respectively; the gain control network being further adapted to form different gain loops with the feedback resistor under the control of the controller;

[0009] The operational amplifier circuit is used to convert the driving voltage under the control of the gain loop and output a control signal corresponding to a current value or a voltage value to the output interface.

[0010] In some embodiments, the output interface includes a first pin and a second pin, and the gain control network includes:

[0011] A first control circuit is used to be connected to the controller and electrically connected to the output terminal of the operational amplifier circuit and the second input terminal of the operational amplifier circuit respectively;

[0012] a second control circuit, configured to be connected to the controller and electrically connected to the second input terminal of the operational amplifier circuit, the second pin, and the ground;

[0013] Under the control of the controller, the first control circuit connects the output terminal of the operational amplifier circuit to the first pin, and when the first control circuit connects the second input terminal of the operational amplifier circuit to the second pin, the operational amplifier circuit is further configured to perform voltage conversion and amplification processing on the driving voltage and output a control signal corresponding to a current value; and

[0014] The first control circuit connects the output end of the operational amplifier circuit to its second input end and the first pin respectively. When the first control circuit grounds the second pin, the operational amplifier circuit is further used to amplify the driving voltage and output a control signal corresponding to the voltage value.

[0015] In some embodiments, the first control circuit includes:

[0016] a first resistor connected in series between the output terminal of the operational amplifier circuit and the first pin;

[0017] a second resistor, a first end of which is connected to the second input end of the operational amplifier circuit;

[0018] The first switch is connected in series between the output terminal of the operational amplifier circuit and the second terminal of the second resistor.

[0019] In some embodiments, the first switch includes an analog switch or a switch tube.

[0020] In some embodiments, the second control circuit includes:

[0021] a second switch connected in series between the output terminal of the operational amplifier circuit and the second pin;

[0022] A third switch is connected in series between the second pin and the ground.

[0023] In some embodiments, the operational amplifier circuit includes:

[0024] An operational amplifier, comprising a positive input pin, a negative input pin, an output pin, a power pin, and a ground pin, wherein the positive input pin is a first input terminal of the operational amplifier circuit, the negative input pin is a second input terminal of the operational amplifier circuit, the output pin is an output terminal of the operational amplifier circuit, the power pin is used to connect to a first power supply, and the ground pin is grounded;

[0025] A first capacitor is connected in series between the inverting input pin and the ground.

[0026] In some embodiments, the operational amplifier circuit further includes:

[0027] The second capacitor and the third capacitor, the first end of the second capacitor and the first end of the third capacitor are respectively used to connect to the first power supply, and the second end of the second capacitor and the second end of the third capacitor are respectively grounded.

[0028] In some embodiments, the filtering circuit includes:

[0029] a third resistor, a first end of which is the input end of the filter circuit and a second end of which is the output end of the filter circuit;

[0030] The fourth capacitor is connected in series between the second end of the third resistor and the ground.

[0031] In some embodiments, the signal output circuit further includes:

[0032] The surge suppression circuit has a power supply end for connecting to a second power supply, an input end connected to the output end of the filter circuit, and a ground end connected to ground. The surge suppression circuit is used to discharge surges connected to the filter circuit.

[0033] The present invention further provides an air conditioner, comprising a controller, an output interface and the above-mentioned signal output circuit, wherein the signal output circuit is connected in series between the controller and the output interface.

[0034] The technical solution of the present invention filters a driving signal with an adjustable duty cycle into a driving voltage that can be processed by an operational amplifier circuit by setting a filtering circuit, and utilizes the principle that the operational amplifier circuit can realize different signal processing functions under different gain loops to set a gain control network so that it can be combined with a feedback resistor to form different gain loops to control the functions realized by the operational amplifier circuit, so that the air conditioner can only set up one signal output circuit to switch the control signal output by the output interface between current type and voltage type, without having to set up peripheral circuits separately for signal switching, thereby improving the compatibility of the output interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, 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 the structures shown in these drawings without paying any creative work.

[0036] Figure 1 This is a structural diagram of an embodiment of a signal output circuit of the present utility model;

[0037] Figure 2This is a structural diagram of another embodiment of the signal output circuit of the present utility model;

[0038] Figure 3 This is a circuit connection diagram of an embodiment of the signal output circuit of the present utility model;

[0039] Figure 4 This is a circuit connection diagram for outputting a control signal corresponding to a current value of the utility model;

[0040] Figure 5 This is a circuit connection diagram for outputting a control signal corresponding to a voltage value of the utility model;

[0041] Figure 6 This is a circuit connection diagram of another embodiment of the signal output circuit of the present utility model;

[0042] Figure 7 This is a circuit connection diagram of another embodiment of the signal output circuit of the present invention.

[0043] Description of Figure Numbers:

[0044] Label name Label name 100 filter circuit U1 Operational amplifier 200 Op amp circuit U2~U3 First analog switch to second analog switch 300 Feedback resistor TVS1 Static electricity tube 400 Gain Control Network S1~S3 First switch to third switch 410 First control circuit C1~C4 First capacitor to fourth capacitor 420 Second control circuit R1~R3 First resistor to third resistor 500 Surge suppression circuit

[0045] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0047] In addition, in this utility model, the descriptions of "first" and "second" are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features specified as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this utility model.

[0048] The utility model provides a signal output circuit applied to an air conditioner. The air conditioner comprises an output interface and a controller.

[0049] Reference Figure 1In one embodiment, the signal output circuit includes:

[0050] The filter circuit 100 has an input terminal for connecting to the controller. The filter circuit 100 is also used to filter the duty cycle adjustable drive signal output by the controller into a stable drive voltage output;

[0051] an operational amplifier circuit 200 , a first input terminal of which is connected to the output terminal of the filter circuit 100 ;

[0052] A feedback resistor 300 is connected in series between the second input terminal of the operational amplifier circuit 200 and the ground;

[0053] a gain control network 400, adapted to be connected to the controller and electrically connected to the output interface, the second input terminal of the operational amplifier circuit 200, and the output terminal thereof; the gain control network 400 is further adapted to form different gain loops with the feedback resistor 300 under the control of the controller;

[0054] The operational amplifier circuit 200 is used to convert the driving voltage under the control of the gain loop and output a control signal corresponding to the current value or voltage value to the output interface.

[0055] In this embodiment, the signal output circuit is arranged between the controller and the output interface, and converts and processes the driving signal output by the controller to control the external load connected to the output interface, wherein the driving signal is a PWM signal with an adjustable duty cycle, and the filtering circuit 100 can be RC filtering or LC filtering.

[0056] When the air conditioner is working, the filter is connected to the driving signal with adjustable duty cycle. The duty cycle of the driving signal is set by the controller according to the signals output by the interactive components, feedback circuit and other circuit units. I Taking the input voltage of the operational amplifier circuit 200 as an example, the relationship between the duty cycle of the driving signal and the driving voltage is U I =5V*D.

[0057] Specifically, under the control of the controller, the gain control network 400 adjusts the internal connection mode to form different feedback loops with the feedback circuit. For example, when the gain control network 400, under the control of the controller, forms a feedback loop with the feedback circuit to control the operational amplifier circuit 200 to implement the voltage-current conversion function, the operational amplifier circuit 200 converts the driving voltage and outputs a control signal corresponding to the current value; or, when the gain control network 400, under the control of the controller, forms a feedback loop with the feedback circuit to control the operational amplifier circuit 200 to implement the voltage amplification function, the operational amplifier circuit 200 converts the driving voltage and outputs a control signal corresponding to the current value.

[0058] It should be noted that the controller can communicate with the driven load to obtain the required control signal type, or the user can input the required control signal type into the controller through the interactive component.

[0059] The technical solution of the present invention filters the driving signal with adjustable duty cycle into a driving voltage that can be processed by the operational amplifier circuit 200 by setting a filter circuit 100, and utilizes the principle that the operational amplifier circuit 200 can realize different signal processing functions under different gain loops to set a gain control network 400 so that it can be combined with the feedback resistor 300 to form different gain loops to control the functions realized by the operational amplifier circuit 200, so that the air conditioner can only set up one signal output circuit to switch the control signal output by the output interface between current type and voltage type, without having to set up peripheral circuits separately for signal switching, thereby improving the compatibility of the output interface.

[0060] Reference Figures 1 to 2 In one embodiment, the output interface includes a first pin and a second pin, and the gain control network 400 includes:

[0061] A first control circuit 410 is used to be connected to the controller and electrically connected to the output terminal of the operational amplifier circuit 200 and the second input terminal of the operational amplifier circuit 200;

[0062] A second control circuit 420 is configured to be connected to the controller and electrically connected to the second input terminal, the second pin, and the ground of the operational amplifier circuit 200;

[0063] Under the control of the controller, the first control circuit 410 connects the output terminal of the operational amplifier circuit 200 to the first pin. When the first control circuit 410 connects the second input terminal of the operational amplifier circuit 200 to the second pin, the operational amplifier circuit 200 is further configured to perform voltage conversion and amplification processing on the driving voltage and output a control signal corresponding to the current value; and

[0064] The first control circuit 410 connects the output end of the operational amplifier circuit 200 to its second input end and the first pin respectively. When the first control circuit 410 grounds the second pin, the operational amplifier circuit 200 is further used to amplify the driving voltage and output a control signal corresponding to the voltage value.

[0065] In this embodiment, the first control circuit 410 is used to control the connection mode between the first pin and the operational amplifier circuit 200 , and the second control circuit 420 is used to control the connection mode between the second pin and the operational amplifier circuit 200 .

[0066] It can be understood that the functions implemented by the operational amplifier circuit 200 are different under different gain loops. When its output end is not connected to its second input end, and the second input end is directly connected to the second pin after being connected to the feedback resistor 300, the operational amplifier circuit 200 is set as a voltage-current converter, so the input driving voltage is converted and processed into a control signal of the corresponding current value.

[0067] When the output terminal is feedback-connected to the second input terminal and connected to the feedback resistor 300 , the operational amplifier circuit 200 is configured as a voltage amplifier, so the connected driving voltage is amplified and processed into a control signal of a corresponding voltage value.

[0068] Reference Figures 1 to 5 In one embodiment, the operational amplifier circuit 200 includes:

[0069] Operational amplifier U1 includes a positive input pin, a negative input pin, an output pin, a power pin, and a ground pin. The positive input pin is the first input terminal of the operational amplifier circuit 200, the negative input pin is the second input terminal of the operational amplifier circuit 200, the output pin is the output terminal of the operational amplifier circuit 200, the power pin is used to connect to the first power supply, and the ground pin is grounded.

[0070] The first capacitor C1 is connected in series between the inverting input pin and the ground.

[0071] The first control circuit 410 includes:

[0072] A first resistor R1 is connected in series between the output terminal of the operational amplifier circuit 200 and the first pin;

[0073] a second resistor R2, a first end of which is connected to the second input end of the operational amplifier circuit 200;

[0074] The first switch S1 is connected in series between the output terminal of the operational amplifier circuit 200 and the second terminal of the second resistor R2.

[0075] The second control circuit 420 includes:

[0076] A second switch S2 is connected in series between the output terminal of the operational amplifier circuit 200 and the second pin;

[0077] The third switch S3 is connected in series between the second pin and the ground.

[0078] In this embodiment, the first switch S1 , the second switch S2 , and the third switch S3 are configured to be turned on or off under the control of the controller to combine the first resistor R1 , the second resistor R2 , and the feedback resistor 300 into different gain loops.

[0079] Specifically, when the first switch S1 and the third switch S3 are disconnected and the second switch S2 is closed, the second pin is connected to the second input terminal of the operational amplifier circuit 200, and the first pin is connected to the output terminal of the operational amplifier circuit 200 via the first resistor R1. At this time, the first resistor R1 and the feedback resistor 300 form a gain loop, which, combined with the operational amplifier U1, forms a current-voltage converter, wherein the output current is calculated as:

[0080] According to the principle of virtual short and virtual disconnect of operational amplifier U1, confirm the input voltage of operational amplifier U1:

[0081]

[0082] Among them, the R L is the resistance value corresponding to the feedback resistor 300, R1 is the resistance value corresponding to the first resistor, and U I is the input voltage (ie, driving voltage) of the operational amplifier U1, and the U o is the voltage of the first pin of the output interface.

[0083] Output voltage after conversion

[0084] The first pin of the output interface is connected in series with the feedback resistor 300 , that is, the current value of the control signal is equal to the current value flowing through the feedback resistor 300 .

[0085] Taking the amplitude of the driving signal as 5V as an example, according to the virtual disconnection principle of the operational amplifier circuit 200, the voltage across the feedback resistor 300 is U RL =U I =5V*D.

[0086] Output current:

[0087] Therefore, the duty cycle of the driving signal can be calculated according to the current value required by the control signal, thereby realizing current output control.

[0088] Likewise, the operational amplifier circuit 200 is further configured to process the input signal into a corresponding current signal for output.

[0089] When the first switch S1 and the third switch S3 are closed and the second switch S2 is open, the second pin is grounded, and the first pin is connected to the output terminal of the operational amplifier circuit 200 via the first resistor R1, and is connected to the second input terminal of the operational amplifier circuit 200 via the first resistor R1 and the second resistor R2. At this time, the first resistor R1, the second resistor R2, and the feedback resistor 300 form a gain loop, which is combined with the operational amplifier U1 to form a voltage amplifier, wherein the output voltage is calculated as:

[0090] According to the operational amplifier circuit 200, U I =U RL ,

[0091] After adjustment, the output voltage is

[0092] Therefore, the duty cycle of the driving signal can be calculated according to the voltage value required by the control signal, thereby realizing voltage output control.

[0093] Specifically, the first switch S1 includes an analog switch or a switch tube.

[0094] In this embodiment, if Figure 7 As shown, the analog switch is taken as an example for description, wherein the analog switch includes a first analog switch U2 and a second analog switch U3.

[0095] The first analog switch U2 includes a first input pin, a first selection pin, and a second selection pin. The first input pin is connected to the output end of the operational amplifier U1, the first selection pin is connected to the first end of the first resistor R1, and the second selection pin is connected to the first end of the second resistor R2.

[0096] The second analog switch U3 includes a second input pin, a third selection pin and a fourth selection pin. The second input pin is connected to the second pin, the third selection pin is connected to the inverting input terminal of the operational amplifier U1, and the second selection pin is grounded.

[0097] Specifically, when the control signal is a current signal, the first analog switch U2, under the control of the controller, connects the first selection pin, so that the output end of the operational amplifier U1 is directly connected to the first pin through the first resistor R1; the second analog resistor, under the control of the controller, connects the third selection pin, so that the second pin is respectively connected to the inverting input end of the operational amplifier U1 and the feedback resistor 300.

[0098] When the control signal is a voltage signal, the first analog switch U2, under the control of the controller, connects the first selection pin and the second selection pin at the same time, so that the output end of the operational amplifier U1 is connected to the first pin through the first resistor R1, and is respectively connected to the inverting input end of the operational amplifier U1 and the feedback resistor 300. Under the control of the controller, the second analog resistor connects the fourth selection pin, so that the second pin is directly grounded.

[0099] Reference Figures 1 to 6 In one embodiment, the operational amplifier circuit 200 further includes:

[0100] The second capacitor C2 and the third capacitor C3, the first end of the second capacitor C2 and the first end of the third capacitor C3 are respectively used to connect to the first power supply, and the second end of the second capacitor C2 and the second end of the third capacitor C3 are respectively grounded.

[0101] In this embodiment, the second capacitor C2 and the third capacitor C3 are filter capacitors for filtering the connected first power supply to ensure stable operation of the operational amplifier U1.

[0102] Reference Figures 1 to 6 In one embodiment, the filtering circuit 100 includes:

[0103] a third resistor R3, a first end of which is the input end of the filter circuit 100 and a second end of which is the output end of the filter circuit 100;

[0104] The fourth capacitor C4 is connected in series between the second end of the third resistor R3 and the ground.

[0105] In this embodiment, the third resistor R3 and the fourth capacitor C4 combine to form an RC filter circuit 100. Specifically, when the air conditioner is operating, the controller outputs a PWM waveform drive signal with an adjustable duty cycle of 0-100%. For example, if the drive signal amplitude is 5V, the drive signal is filtered by the third resistor R3 and the fourth capacitor C4, converted into a 0-5V drive voltage, and input into the operational amplifier circuit 200.

[0106] Reference Figures 1 to 6 In one embodiment, the signal output circuit further includes:

[0107] The surge suppression circuit 500 has a power supply end for connecting to a second power supply, an input end connected to the output end of the filter circuit 100 , and a ground end connected to ground. The surge suppression circuit 500 is used to discharge surges connected to the filter circuit 100 .

[0108] In this embodiment, the surge suppression circuit 500 includes:

[0109] The electrostatic tube TVS1 has a power supply terminal for connecting to a second power supply, an input terminal connected to the output terminal of the filter circuit 100 , and a ground terminal connected to ground.

[0110] Since the filter circuit 100 is directly connected to the I / O port of the controller, and the interface is easily connected to surges due to thunderstorms, internal interference of the equipment terminal, etc., a surge suppression circuit 500 including an electrostatic tube TVS1 is provided to discharge the surge and avoid interference of voltage fluctuations on the internal circuit.

[0111] The present invention also proposes an air conditioner, which includes a controller, an output interface and the above-mentioned signal output circuit. The signal output circuit is connected in series between the controller and the output interface. The specific structure of the signal output circuit refers to the above-mentioned embodiment. Since this air conditioner adopts all the technical solutions of all the above-mentioned embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above-mentioned embodiments, which will not be repeated here.

[0112] The above description is merely an optional embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by utilizing the contents of the present invention specification and drawings under the utility model concept, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A signal output circuit, applied to an air conditioner, the air conditioner comprising an output interface and a controller, characterized in that: The signal output circuit includes: A filter circuit, whose input end is used to connect to the controller, and the filter circuit is further used to filter the driving signal with adjustable duty cycle output by the controller into a stable driving voltage output; an operational amplifier circuit, a first input terminal of which is connected to the output terminal of the filter circuit; a feedback resistor connected in series between the second input terminal of the operational amplifier circuit and ground; a gain control network, adapted to be connected to the controller and electrically connected to the output interface, the second input terminal of the operational amplifier circuit, and the output terminal thereof, respectively; the gain control network being further adapted to form different gain loops with the feedback resistor under the control of the controller; The operational amplifier circuit is used to convert the driving voltage under the control of the gain loop and output a control signal corresponding to a current value or a voltage value to the output interface.

2. The signal output circuit according to claim 1, wherein: The output interface includes a first pin and a second pin, and the gain control network includes: A first control circuit is used to be connected to the controller and electrically connected to the output terminal of the operational amplifier circuit and the second input terminal of the operational amplifier circuit respectively; a second control circuit, configured to be connected to the controller and electrically connected to the second input terminal of the operational amplifier circuit, the second pin, and the ground; Under the control of the controller, the first control circuit connects the output terminal of the operational amplifier circuit to the first pin, and when the first control circuit connects the second input terminal of the operational amplifier circuit to the second pin, the operational amplifier circuit is further configured to perform voltage conversion and amplification processing on the driving voltage and output a control signal corresponding to a current value; and The first control circuit connects the output end of the operational amplifier circuit to its second input end and the first pin respectively. When the first control circuit grounds the second pin, the operational amplifier circuit is further used to amplify the driving voltage and output a control signal corresponding to the voltage value.

3. The signal output circuit according to claim 2, wherein: The first control circuit includes: a first resistor connected in series between the output terminal of the operational amplifier circuit and the first pin; a second resistor, a first end of which is connected to the second input end of the operational amplifier circuit; The first switch is connected in series between the output terminal of the operational amplifier circuit and the second terminal of the second resistor.

4. The signal output circuit according to claim 3, wherein: The first switch includes an analog switch or a switch tube.

5. The signal output circuit according to claim 2, wherein: The second control circuit includes: a second switch connected in series between the output terminal of the operational amplifier circuit and the second pin; A third switch is connected in series between the second pin and the ground.

6. The signal output circuit according to claim 1, wherein: The operational amplifier circuit comprises: An operational amplifier, comprising a positive input pin, a negative input pin, an output pin, a power pin, and a ground pin, wherein the positive input pin is a first input terminal of the operational amplifier circuit, the negative input pin is a second input terminal of the operational amplifier circuit, the output pin is an output terminal of the operational amplifier circuit, the power pin is used to connect to a first power supply, and the ground pin is grounded; A first capacitor is connected in series between the inverting input pin and the ground.

7. The signal output circuit according to claim 6, wherein: The operational amplifier circuit further includes: The second capacitor and the third capacitor, the first end of the second capacitor and the first end of the third capacitor are respectively used to connect to the first power supply, and the second end of the second capacitor and the second end of the third capacitor are respectively grounded.

8. The signal output circuit according to claim 1, wherein: The filtering circuit comprises: a third resistor, a first end of which is the input end of the filter circuit and a second end of which is the output end of the filter circuit; The fourth capacitor is connected in series between the second end of the third resistor and the ground.

9. The signal output circuit according to claim 1, wherein: The signal output circuit further includes: The surge suppression circuit has a power supply end for connecting to a second power supply, an input end connected to the output end of the filter circuit, and a ground end connected to ground. The surge suppression circuit is used to discharge surges connected to the filter circuit.

10. An air conditioner, characterized in that: It comprises a controller, an output interface and the signal output circuit according to any one of claims 1 to 9, wherein the signal output circuit is connected in series between the controller and the output interface.

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