Air conditioner

Abstract

The utility model discloses an air conditioner which comprises a temperature detection circuit which is used for detecting the temperature of the position where a temperature sensor is located and comprises a voltage division circuit which comprises a thermistor of the temperature sensor, and the divided voltage output by the voltage division circuit changes along with the change of the resistance value of the thermistor; the in-phase input end of the operational amplifier receives the divided voltage, the anti-phase input end of the operational amplifier is grounded through a resistor, and the output end of the operational amplifier is fed back to the anti-phase input end of the operational amplifier through a change-over switch and a feedback resistor which are connected in parallel; and the controller is used for receiving the voltage signal output by the operational amplifier and outputting a control signal for controlling the switching switch to be switched off when the voltage signal output by the operational amplifier reaches the lower limit value of the threshold voltage. According to the utility model, the divided voltage can be amplified in a single-time or multi-time manner based on the magnitude of the divided voltage, and the temperature detection accuracy of the temperature sensor at low divided voltage is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of air conditioner detection, in particular to an air conditioner. Background Art

[0002] Air conditioners are used in our daily lives. When using air conditioners, temperature sensors are needed to detect the temperatures at different locations in the air conditioner (such as indoor temperature, outdoor temperature, radiator temperature, etc.). At this time, the temperature sensor needs to be combined with a temperature detection circuit to obtain the measured temperature.

[0003] The existing temperature detection circuit mainly adopts a bridge design, which uses a voltage divider resistor and a thermistor to change the voltage through the bridge. The output voltage divider is directly input into a microcontroller with a built-in analog-to-digital conversion function for collection and measurement after filtering and voltage clamping. In this way, the resistance of the temperature sensor is inferred, and then the temperature at different positions where the temperature sensor is placed in the air conditioner is calculated.

[0004] The temperature range of the temperature sensor test is relatively wide, and the corresponding thermistor variation range is relatively large. The maximum and minimum values ​​of the thermistor can differ by about 1000 times. Therefore, even if the appropriate voltage divider resistance is selected, when the temperature is different and the thermistor resistance value differs greatly, the smaller voltage divider collected will be more likely to be affected by noise signals when entering the analog-to-digital converter, affecting the temperature detection accuracy, thereby affecting the judgment of the temperature accuracy at different locations.

[0005] The above information disclosed in the background technology is only used to increase the understanding of the background technology of the present application, and therefore, it may include information that does not constitute the prior art known to ordinary technicians in the field. Utility Model Content

[0006] In view of the problems pointed out in the background technology, the utility model provides an air conditioner, which controls the single or multiple amplification of the partial pressure based on the partial pressure size, so as to improve the temperature detection accuracy of the temperature sensor at low partial pressure.

[0007] In order to achieve the above-mentioned utility model purpose, the utility model adopts the following technical solutions:

[0008] The present application also relates to an air conditioner, comprising:

[0009] A refrigerant circulation loop, wherein the refrigerant circulates in the compressor, the condenser, the expansion valve, and the evaporator, wherein the compressor is used to compress the low-temperature and low-pressure refrigerant gas into a high-temperature and high-pressure refrigerant gas and discharge it to the condenser;

[0010] An outdoor heat exchanger and an indoor heat exchanger, one of which works as a condenser and the other works as an evaporator;

[0011] A temperature detection circuit is used to detect the temperature at a location where a temperature sensor is located, and comprises:

[0012] A voltage divider circuit, comprising a thermistor of the temperature sensor, wherein the divided voltage output by the voltage divider circuit varies with the resistance value of the thermistor;

[0013] An operational amplifier, whose non-inverting input terminal receives the divided voltage, whose inverting input terminal is grounded through a resistor, and whose output terminal is fed back to the inverting input terminal of the operational amplifier through a switching switch and a feedback resistor connected in parallel;

[0014] A controller receives the voltage signal output by the operational amplifier, and outputs a control signal for controlling the switch to be disconnected when the voltage signal output by the operational amplifier reaches a lower limit value of a threshold voltage.

[0015] The air conditioner involved in the present application detects the temperature at the location of the temperature sensor by means of a set temperature detection circuit.

[0016] Based on the magnitude of the divided voltage output by the operational amplifier, the controller controls the switching switch. In the initial state, the switching switch is normally closed, and the operational amplifier is used as a voltage follower.

[0017] When the divided voltage reaches the upper limit of the threshold voltage, the switch remains closed and the operational amplifier acts as a voltage follower.

[0018] When the divided voltage reaches the lower limit of the threshold voltage, the controller controls the switching switch to be disconnected, and the operational amplifier amplifies the divided voltage, thereby reducing the influence of the noise signal on the divided voltage signal and improving the temperature detection accuracy at low divided voltage.

[0019] In some embodiments of the present application, in order to improve the accuracy of the output voltage division, the temperature detection circuit further includes:

[0020] A filter circuit is connected to the voltage divider output terminal of the voltage divider circuit and the non-inverting input terminal of the operational amplifier.

[0021] In some embodiments of the present application, the filtering circuit adopts a low-pass filtering circuit, which can filter out high-frequency noise signals in the voltage-divided signal. The filtering circuit includes:

[0022] A filter resistor connected between the voltage divider output terminal and the in-phase input terminal;

[0023] A first filter capacitor, one end of which is connected between the voltage divider output end and one end of the filter resistor, and the other end of which is grounded;

[0024] A second filter capacitor has one end connected between the other end of the filter resistor and the in-phase input terminal, and the other end grounded.

[0025] In some embodiments of the present application, in order to protect the back-end circuit and prevent the output voltage division from exceeding the amplitude range of the operational amplifier, the temperature detection circuit further includes:

[0026] A voltage clamping circuit is arranged between the voltage-dividing output terminal and the in-phase input terminal, and is used for limiting the amplitude range of the voltage divided by the voltage-dividing output terminal.

[0027] In some embodiments of the present application, the voltage clamping circuit includes:

[0028] A first diode, an anode of which is connected to the voltage-dividing output terminal and the non-inverting input terminal, and a cathode of which is grounded;

[0029] The second diode has an anode connected to the ground and a cathode connected to the anode of the first diode and the non-inverting input terminal.

[0030] In some embodiments of the present application, in order to realize that when the temperature changes, the change in the resistance value of the thermistor is reflected in the divided voltage output by the voltage divider circuit, the voltage divider circuit includes:

[0031] A voltage divider resistor has one end grounded and the other end connected to one end of the thermistor. The other end of the thermistor is connected to a power supply VCC. The position between the thermistor and the voltage divider resistor is the voltage divider output end.

[0032] In some embodiments of the present application, in order to achieve controllable switching of the switch, the temperature detection circuit further includes:

[0033] A relay, which is powered by the power supply, and the switch is a normally closed contact of the relay;

[0034] A switch control circuit connected to a power supply circuit for supplying power to the coil, and a control end of the switch control circuit connected to an output end of the controller for outputting a control signal;

[0035] When the voltage signal output by the operational amplifier reaches the lower limit of the threshold voltage, the control signal output by the controller closes the switch control circuit, and the coil is energized;

[0036] When the voltage signal output by the operational amplifier reaches the upper limit of the threshold voltage, the control signal output by the controller disconnects the switch control circuit and the coil loses power.

[0037] In some embodiments of the present application, the switch control circuit includes a switch control element;

[0038] The control end of the switch control element is connected to the controller;

[0039] When the voltage signal output by the operational amplifier reaches the lower limit of the threshold voltage, the controller outputs a signal to the control terminal to disconnect the switch control element;

[0040] When the voltage signal output by the operational amplifier reaches an upper limit value of a threshold voltage, the controller outputs a signal to the control terminal to turn on the switch control element.

[0041] In some embodiments of the present application, the switch control element is a switch element that is turned on at a high level or a switch element that is turned on at a low level.

[0042] In some embodiments of the present application, when the switch control element is a switch element that is turned on at a high level, the switch control element is an NMOS tube;

[0043] The gate of the NMOS tube receives the control signal output by the controller, the drain is connected to the coil, and the source is connected to the ground;

[0044] When the switch control element is a switch element that is turned on at a low level, the switch control element is a PMOS tube;

[0045] The gate of the PMOS tube receives the control signal output by the controller, the source is connected to the power supply, and the drain is connected to the coil.

[0046] After reading the specific embodiments of the present invention in conjunction with the accompanying drawings, other features and advantages of the present invention will become more clear. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0048] Figure 1 is a principle block diagram of an embodiment of an air conditioner, which shows the refrigerant flow direction when the air conditioner is cooling;

[0049] Figure 2 is a principle block diagram of an embodiment of an air conditioner, which shows the refrigerant flow direction when the air conditioner is heating;

[0050] Figure 3 The principle of the temperature detection circuit in the air conditioner embodiment proposed in this application Figure 1 ;

[0051] Figure 4 The principle of the temperature detection circuit in the air conditioner embodiment proposed in this application Figure 2 ;

[0052] Figure 5 The principle of the temperature detection circuit in the air conditioner embodiment proposed in this application Figure 3 ;

[0053] Figure 6 A circuit diagram of a voltage divider circuit in a temperature detection circuit in an air conditioner embodiment proposed in this application;

[0054] Figure 7 A circuit diagram of a temperature detection circuit of an air conditioner embodiment proposed in this application;

[0055] Figure 8 A structural diagram of an embodiment of a switching switch in an air conditioner embodiment proposed in this application;

[0056] Fig. 9 A structural diagram of another embodiment of the switching switch in the air conditioner embodiment proposed in this application;

[0057] Fig.10 This is a structural diagram of another embodiment of the switching switch in the air conditioner embodiment proposed in this application; reference numerals:

[0058] 10. Voltage divider circuit; 20. Operational amplifier; 30. Controller; 40. Filter circuit; 50. Voltage clamping circuit; 60. Relay. DETAILED DESCRIPTION

[0059] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0060] In the description of the present application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0061] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0062] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0063] In the present utility model, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0064] The disclosure below provides many different embodiments or examples for realizing different structures of the utility model. In order to simplify the disclosure of the utility model, the components and settings of specific examples are described below. Of course, they are merely examples, and the purpose is not to limit the utility model. In addition, the utility model may repeat reference numbers and / or reference letters in different examples, and such repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the utility model provides examples of various specific processes and materials, but those of ordinary skill in the art may be aware of the application of other processes and / or the use of other materials.

[0065] The basic operating principle of air conditioner

[0066] See also Figure 1 and Figure 2 , the air conditioner performs the refrigeration cycle of the air conditioner by using a compressor, condenser, throttling element (such as expansion valve) and evaporator. The refrigeration cycle includes a series of processes involving compression, condensation, expansion and evaporation to cool or heat the indoor space.

[0067] The low-temperature and low-pressure refrigerant enters the compressor, which compresses it into high-temperature and high-pressure refrigerant gas and discharges the compressed refrigerant gas. The discharged refrigerant gas flows into the condenser. The condenser condenses the compressed refrigerant into a liquid phase, and the heat is released to the surrounding environment through the condensation process.

[0068] The expansion valve expands the high-temperature and high-pressure liquid refrigerant condensed in the condenser into a low-pressure liquid refrigerant. The evaporator evaporates the refrigerant expanded in the expansion valve and returns the low-temperature and low-pressure refrigerant gas to the compressor. The evaporator can achieve a cooling effect by utilizing the latent heat of evaporation of the refrigerant to exchange heat with the material to be cooled. In the entire cycle, the air conditioner can adjust the temperature of the indoor space.

[0069] The outdoor unit of the air conditioner refers to a portion of a refrigeration cycle including a compressor and an outdoor heat exchanger, the indoor unit of the air conditioner includes an indoor heat exchanger, and an expansion valve may be provided in the indoor unit or the outdoor unit.

[0070] The indoor heat exchanger and the outdoor heat exchanger function as a condenser or an evaporator. When the indoor heat exchanger functions as a condenser, the air conditioner functions as a heater in a heating mode, and when the indoor heat exchanger functions as an evaporator, the air conditioner functions as a cooler in a cooling mode.

[0071] The outdoor unit of an air conditioner is also commonly referred to as an air conditioner outdoor unit, and the indoor unit of an air conditioner is also commonly referred to as an air conditioner indoor unit.

[0072] See also Figure 1 , which shows the refrigerant flow direction when the air conditioner performs a refrigeration cycle.

[0073] When the four-way valve is powered on, the compressor compresses the low-temperature and low-pressure refrigerant into a high-temperature and high-pressure state, and the refrigerant discharged from the compressor enters the outdoor heat exchanger through the four-way valve.

[0074] After heat exchange inside the outdoor heat exchanger, it condenses and releases heat to become liquid refrigerant. The refrigerant is then throttled to a low-temperature and low-pressure gas-liquid state through the indoor throttling device. The two-phase refrigerant enters the indoor heat exchanger, evaporates, absorbs heat, and becomes gaseous.

[0075] The refrigerant coming out of the indoor heat exchanger enters the gas-liquid separator through the four-way valve and is finally sucked into the compressor for compression to complete the refrigeration cycle.

[0076] In the above refrigeration cycle, the outdoor heat exchanger serves as a condenser and the indoor heat exchanger serves as an evaporator.

[0077] See also Figure 2 , which shows the refrigerant flow direction when the air conditioner performs a heating cycle.

[0078] When the four-way valve is powered on, the compressor compresses the low-temperature and low-pressure refrigerant into a high-temperature and high-pressure state, and the refrigerant discharged from the compressor enters the indoor heat exchanger through the four-way valve.

[0079] After heat exchange inside the indoor heat exchanger, it condenses and releases heat to become liquid refrigerant. The refrigerant is then throttled to a low-temperature and low-pressure gas-liquid state through the indoor throttling device. The two-phase refrigerant enters the outdoor heat exchanger, evaporates and absorbs heat, and becomes gaseous.

[0080] The refrigerant coming out of the outdoor heat exchanger enters the gas-liquid separator through the four-way valve and is finally sucked into the compressor for compression to complete the heating cycle.

[0081] In the above heating cycle, the indoor heat exchanger serves as a condenser and the outdoor heat exchanger serves as an evaporator.

[0082] Temperature detection circuit

[0083] In the control process of the air conditioner, multiple temperatures (eg, indoor temperature, outdoor temperature, radiator temperature, etc.) are usually required, and these temperatures are generally detected and obtained through temperature sensors.

[0084] The temperature sensor includes a thermistor. When the temperature changes, the resistance of the thermistor changes. A positive temperature coefficient thermistor or a negative temperature coefficient thermistor can be used.

[0085] According to the change in the resistance of the thermistor, it is converted into a voltage signal that changes with the resistance, so that the current temperature is estimated based on the voltage signal. This part of estimating the current temperature based on the voltage signal also belongs to the existing technology and will not be introduced here.

[0086] In some embodiments of the present application, the main concern is to accurately obtain the voltage signal caused by the change in the resistance of the thermistor due to temperature change.

[0087] In the temperature detection circuit using the same hardware, the noise signal has a greater impact on the acquisition of small voltage signals, which will reduce the temperature detection accuracy of the noise signal when the voltage division is small.

[0088] Therefore, in some embodiments of the present application, the processing of voltage signals with smaller values ​​is mainly concerned.

[0089] In some embodiments of the present application, a temperature detection circuit is used to detect the temperature at the location of the thermistor by detecting the change of the thermistor.

[0090] See also Figures 3 to 7 The temperature detection circuit includes a voltage divider circuit 10, and the voltage divider circuit 10 includes a thermistor (denoted as R1) of a temperature sensor.

[0091] When the temperature changes, the resistance of the thermistor also changes with the temperature.

[0092] In some embodiments of the present application, the thermistor is selected to be a positive temperature coefficient thermistor.

[0093] When the temperature increases, the resistance of the thermistor increases, and when the temperature decreases, the resistance of the thermistor decreases.

[0094] In some embodiments of the present application, see Figure 6 The voltage divider circuit 10 includes a thermistor R1 and a voltage divider resistor R2 which are connected in series to a power supply Vcc.

[0095] The connection position between the resistor R1 and the voltage-dividing resistor R2 is the voltage-dividing output terminal OUT of the voltage-dividing circuit.

[0096] When the temperature rises, the resistance value of the thermistor increases, and the divided voltage outputted by the voltage divider output terminal OUT decreases; when the temperature decreases, the resistance value of the thermistor decreases, and the divided voltage outputted by the voltage divider output terminal OUT increases.

[0097] In some embodiments of the present application, the voltage divider circuit 10 may also be designed with different forms of resistor series-parallel connections, as long as the output voltage divider can characterize the trend of the thermistor changing with temperature.

[0098] In some embodiments of the present application, the temperature detection circuit includes an operational amplifier 20, which is used to single-fold or multiple-fold amplify the divided voltage output by the voltage divider output terminal OUT.

[0099] The non-inverting input terminal V+ of the operational amplifier 20 is connected to the voltage-dividing output terminal OUT, the inverting input terminal V− is grounded through the resistor R4 , and the output terminal Vout is fed back to the inverting input terminal V− of the operational amplifier 20 through the parallel switching switch K1 and the feedback resistor R5 .

[0100] When the switch K1 is closed, the operational amplifier 20 is used as a voltage follower with an amplification factor of 1, and does not amplify the divided voltage output by the voltage divider circuit 10 .

[0101] When the switch K1 is turned off, the amplification factor of the operational amplifier 20 is (1+R5 / R4), and the divided voltage output by the voltage divider circuit 10 is amplified.

[0102] In some embodiments of the present application, after power-on, the switch K1 is closed by default.

[0103] The specific magnification requirement can be selected and determined according to the state of the switch K1 and the resistance values ​​of the resistor R4 and the resistor R5.

[0104] In some embodiments of the present application, the temperature detection circuit further includes a controller 30 .

[0105] The controller 30 receives the voltage signal output by the operational amplifier 20 , and outputs a control signal for controlling the switch K1 to be disconnected when the voltage signal output by the operational amplifier 20 reaches a lower limit value of a threshold voltage.

[0106] The threshold voltage may be a preset voltage value or a preset voltage range, which is specifically set according to needs.

[0107] Taking voltage fluctuations into consideration, in some embodiments of the present application, the threshold voltage may be set to a preset voltage interval to avoid the collected voltage value fluctuating around the preset voltage value, causing the switching switch K1 to be frequently opened and closed, thereby affecting its service life.

[0108] For example, the threshold voltage is set to a voltage range of 60mV~70mV. When the voltage signal output by the operational amplifier 20 is lower than 60mV, the controller 30 outputs a control signal to control the switching switch K1 to be disconnected. The operational amplifier 20 amplifies the voltage signal by (1+R5 / R4) times, amplifies the smaller voltage division, and reduces the interference of the noise signal on it.

[0109] The amplified voltage signal is transmitted to the controller 30 (specifically, to the analog-to-digital conversion module in the controller 30 ) for temperature detection.

[0110] When the voltage signal output by the operational amplifier 20 is higher than 70 mV, the controller 30 outputs a control signal to control the switch K to close, and the operational amplifier 20 functions as a voltage follower.

[0111] At this time, the voltage signal output by the operational amplifier 20 is transmitted to the controller 30 for temperature detection.

[0112] In some embodiments of the present application, in order to improve the accuracy of the output divided voltage, the temperature detection circuit further includes a filter circuit 40 .

[0113] The filter circuit 40 can filter out noise signals in the voltage-divided signal, thereby ensuring the accuracy of the voltage-divided signal transmitted backward.

[0114] In some embodiments of the present application, see Figure 7 The filter circuit 40 is an RC low-pass filter circuit, which is used to filter out high-frequency noise signals in the voltage-divided signal.

[0115] The filter circuit 40 is disposed between the voltage-dividing output terminal OUT and the non-inverting input terminal V+ of the operational amplifier 20 .

[0116] In some embodiments of the present application, the filter circuit 40 includes a filter resistor R3, a first filter capacitor C1 and a second filter capacitor C2.

[0117] One end of the filter resistor R3 is connected to the voltage-dividing output terminal OUT and one end of the first filter capacitor C1 respectively, and the other end of the first filter capacitor C1 is grounded.

[0118] The other end of the filter resistor R3 is connected to the non-inverting input terminal V+ of the operational amplifier 20 and one end of the second filter capacitor C2 respectively, and the other end of the second filter capacitor C2 is grounded.

[0119] In some embodiments of the present application, the filter circuit 40 may also adopt other filtering forms.

[0120] In some embodiments of the present application, the temperature detection circuit further includes a voltage clamping circuit 50 for limiting the voltage amplitude sent to the operational amplifier 20 to protect the back-end circuit from damage.

[0121] See also Figure 7 , the voltage clamping circuit 50 includes a first diode D1 and a second diode D2.

[0122] The anode of the first diode D1 is connected to the voltage-dividing output terminal OUT, the cathode of the second diode D2 and the non-inverting input terminal V+ of the operational amplifier 20 respectively, and the cathode of the first diode D1 is connected to the power supply Vcc.

[0123] The anode of the second diode D2 is connected to the anode of the first diode D1 and the non-inverting input terminal V+ of the operational amplifier 20 respectively, and the cathode of the second diode D2 is grounded.

[0124] As described above, the switching switch K1 is a controllable switch that can remain closed when powered on. When the divided voltage is lower than 60mV, the controller 30 controls the switching switch K1 to be disconnected, and the divided voltage is amplified by the operational amplifier 20 and input into the analog-to-digital conversion module of the controller 30. The amplified divided voltage can reduce the influence of the noise signal on the divided voltage signal, thereby improving the accuracy of temperature detection.

[0125] In some embodiments of the present application, see Figures 8 to 10 , the switch K1 can be selected as the normally closed contact of the relay 60.

[0126] When the coil KM of the relay 60 is not energized, the normally closed contact KM is closed, that is, the switch K1 is closed, so that the gain of the operational amplifier 20 is 1.

[0127] When the coil KM of the relay 60 is energized, the normally closed contact KM is opened, that is, the switch K1 is opened, so that the amplification factor of the operational amplifier 20 is 1+R5 / R4.

[0128] See also Figures 8 to 10 , a switch control circuit is used to control whether the power source Vcc supplies power to the coil of relay 60.

[0129] The switch control circuit is connected to a power supply circuit for supplying power to the coil of relay 60. When the switch control circuit is connected, the power supply Vcc supplies power to the coil and the coil is energized. When the switch control circuit is disconnected, the power supply Vcc does not supply power to the coil and the coil loses power.

[0130] When the voltage signal output by the operational amplifier 20 is lower than 60mV, the control signal output by the controller 30 at the output terminal closes the switch control circuit, energizes the coil KM, disconnects the corresponding normally closed contact KM, and amplifies the voltage division signal using the amplification factor (1+R5 / R4) of the operational amplifier 20.

[0131] When the voltage signal output by the operational amplifier 20 is higher than 70mV, the control signal output by the controller 30 at the output terminal disconnects the switch control circuit, so that the coil KM is not energized, and the corresponding normally closed contact KM is closed. The operational amplifier 20 acts as a voltage follower and does not amplify the voltage-dividing signal.

[0132] When the voltage signal output by the operational amplifier 20 is within the range of 60 mV to 70 mV, the relay 60 maintains the current state.

[0133] In some embodiments of the present application, see Figures 8 to 10 , the switch control circuit includes a switch control element.

[0134] The switch control element may be a high level switch control element or a low level switch control element.

[0135] In some embodiments of the present application, the high-level switch control element can be selected from the NMOS tube Q1, see Figure 8 .

[0136] The gate of the NMOS tube Q1 is connected to the output terminal of the controller 30 outputting the control signal through the current limiting resistor R2 ′, the source is grounded, the drain is connected to one end of the coil KM, and the other end of the coil KM is connected to the power supply Vcc through the current limiting resistor R6 .

[0137] When the voltage signal output by the operational amplifier 20 is lower than 60 mV, the controller 30 outputs a high level signal at the output terminal, and the NMOS tube Q1 is turned on. At this time, the power supply Vcc supplies power to the coil KM, and its normally closed contact is disconnected.

[0138] That is, the switch K1 is turned off, and the voltage-divided signal is amplified by the amplification factor (1+R5 / R4) of the operational amplifier 20.

[0139] When the voltage signal output by the operational amplifier 20 is higher than 70 mV, the controller 30 outputs a low level signal at the output terminal, and the NMOS tube Q1 is turned off. At this time, the power supply Vcc does not supply power to the coil KM, and its normally closed contact is closed.

[0140] That is, the switch K1 is closed, and the operational amplifier 20 is used as a voltage follower and does not amplify the divided voltage signal.

[0141] When the voltage signal output by the operational amplifier 20 is within the range of 60 mV to 70 mV, the NMOS transistor Q1 maintains the current state.

[0142] In some embodiments of the present application, the high-level switch control element can select the NPN tube Q3, see Fig. 9 .

[0143] The base of the NPN tube Q3 is connected to the output terminal of the controller 30 outputting the control signal through the current limiting resistor R6', the emitter is grounded, the collector is connected to one end of the coil KM, and the other end of the coil KM is connected to the power supply Vcc through the current limiting resistor R8.

[0144] When the voltage signal output by the operational amplifier 20 is lower than 60 mV, the controller 30 outputs a high level signal at the output terminal, and the NPN tube Q3 is turned on. At this time, the power supply Vcc supplies power to the coil KM, and its normally closed contact is disconnected.

[0145] That is, the switch K1 is turned off, and the voltage-divided signal is amplified by the amplification factor (1+R5 / R4) of the operational amplifier 20.

[0146] When the voltage signal output by the operational amplifier 20 is higher than 70 mV, the controller 30 outputs a low level signal at the output terminal, and the NPN tube Q3 is turned off. At this time, the power supply Vcc does not supply power to the coil KM, and its normally closed contact is closed.

[0147] That is, the switch K1 is closed, and the operational amplifier 20 is used as a voltage follower and does not amplify the divided voltage signal.

[0148] When the voltage signal output by the operational amplifier 20 is within the range of 60 mV to 70 mV, the NPN tube Q3 maintains the current state.

[0149] In some embodiments of the present application, the low-level switch control element can be a PMOS tube Q2, see Fig.10 .

[0150] The gate of the PMOS tube Q2 is connected to the output terminal of the controller 30 outputting the control signal through the current limiting resistor R5 ′, the source is connected to the power supply Vcc, the drain is connected to one end of the coil KM, and the other end of the coil KM is grounded through the current limiting resistor R7 .

[0151] When the voltage signal output by the operational amplifier 20 is lower than 60 mV, the controller 30 outputs a low level signal at the output terminal, and the PMOS tube Q2 is turned on. At this time, the power supply Vcc supplies power to the coil KM, and its normally closed contact is disconnected.

[0152] That is, the switch K1 is turned off, and the voltage-divided signal is amplified by the amplification factor (1+R5 / R4) of the operational amplifier 20.

[0153] When the voltage signal output by the operational amplifier 20 is higher than 70 mV, the controller 30 outputs a high level signal at the output terminal, and the PMOS tube Q2 is disconnected. At this time, the power supply Vcc does not supply power to the coil KM, and its normally closed contact is closed.

[0154] That is, the switch K1 is closed, and the operational amplifier 20 functions as a voltage follower and does not amplify the divided voltage signal.

[0155] When the voltage signal output by the operational amplifier 20 is within the range of 60 mV to 70 mV, the PMOS tube Q2 maintains the current state.

[0156] In some embodiments of the present application, the controllable device having the switching switch K1 as described above may also be designed as other structures, such as an analog switch.

[0157] The air conditioner involved in the present application, when using a temperature detection circuit for temperature detection, utilizes a voltage division amplification method to amplify a low voltage division, reduce the influence of noise signals on the low voltage division, and thus improve the accuracy of temperature detection under low voltage division.

[0158] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0159] The above is only a specific implementation of the utility model, but the protection scope of the utility model is not limited to this. Any changes or substitutions that can be easily thought of by technicians familiar with the technical field within the technical scope disclosed by the utility model should be included in the protection scope of the utility model. Therefore, the protection scope of the utility model should be based on the protection scope of the claims.

Claims

1. An air conditioner, characterized in that: include: A refrigerant circulation loop, wherein the refrigerant circulates in the compressor, the condenser, the expansion valve, and the evaporator, wherein the compressor is used to compress the low-temperature and low-pressure refrigerant gas into a high-temperature and high-pressure refrigerant gas and discharge it to the condenser; An outdoor heat exchanger and an indoor heat exchanger, one of which works as a condenser and the other works as an evaporator; A temperature detection circuit is used to detect the temperature at a location where a temperature sensor is located, and comprises: A voltage divider circuit, comprising a thermistor of the temperature sensor, wherein the divided voltage output by the voltage divider circuit varies with the resistance value of the thermistor; An operational amplifier, whose non-inverting input terminal receives the divided voltage, whose inverting input terminal is grounded through a resistor, and whose output terminal is fed back to the inverting input terminal of the operational amplifier through a switching switch and a feedback resistor connected in parallel; A controller receives the voltage signal output by the operational amplifier, and outputs a control signal for controlling the switch to be disconnected when the voltage signal output by the operational amplifier reaches a lower limit value of a threshold voltage.

2. The air conditioner according to claim 1, characterized in that: The temperature detection circuit also includes: A filter circuit is connected to the voltage-dividing output terminal of the voltage-dividing circuit and the non-inverting input terminal of the operational amplifier.

3. The air conditioner according to claim 2, characterized in that: The filtering circuit comprises: A filter resistor connected between the voltage divider output terminal and the in-phase input terminal; A first filter capacitor, one end of which is connected between the voltage divider output end and one end of the filter resistor, and the other end of which is grounded; A second filter capacitor has one end connected between the other end of the filter resistor and the in-phase input end, and the other end grounded.

4. The air conditioner according to claim 1 or 2, characterized in that: The temperature detection circuit also includes: A voltage clamping circuit is arranged between the voltage-dividing output terminal and the in-phase input terminal, and is used for limiting the amplitude range of the voltage divided by the voltage-dividing output terminal.

5. The air conditioner according to claim 4, characterized in that: The voltage clamping circuit comprises: A first diode, an anode of which is connected to the voltage-dividing output terminal and the non-inverting input terminal, and a cathode of which is grounded; The second diode has an anode connected to the ground and a cathode connected to the anode of the first diode and the non-inverting input terminal.

6. The air conditioner according to claim 1, characterized in that: The voltage divider circuit comprises: A voltage divider resistor has one end grounded and the other end connected to one end of the thermistor. The other end of the thermistor is connected to a power supply VCC. The position between the thermistor and the voltage divider resistor is the voltage divider output end.

7. The air conditioner according to claim 1, characterized in that: The temperature detection circuit also includes: A relay, which is powered by a power supply, and the switching switch is a normally closed contact of the relay; A switch control circuit connected to a power supply circuit for supplying power to the coil of the relay, and a control end of the switch control circuit connected to an output end of the controller for outputting a control signal; When the voltage signal output by the operational amplifier reaches the lower limit of the threshold voltage, the control signal output by the controller closes the switch control circuit, and the coil is energized; When the voltage signal output by the operational amplifier reaches the upper limit of the threshold voltage, the control signal output by the controller disconnects the switch control circuit and the coil loses power.

8. The air conditioner according to claim 7, characterized in that: The switch control circuit includes a switch control element; The control end of the switch control element is connected to the controller; When the voltage signal output by the operational amplifier reaches the lower limit of the threshold voltage, the controller outputs a signal to the control terminal to disconnect the switch control element; When the voltage signal output by the operational amplifier reaches an upper limit value of a threshold voltage, the controller outputs a signal to the control terminal to turn on the switch control element.

9. The air conditioner according to claim 8, characterized in that: The switch control element is a switch element that is turned on at a high level or a switch element that is turned on at a low level.

10. The air conditioner according to claim 9, characterized in that: When the switch control element is a switch element that is turned on at a high level, the switch control element is an NMOS tube; The gate of the NMOS tube receives the control signal output by the controller, the drain is connected to the coil, and the source is grounded; When the switch control element is a switch element that is turned on at a low level, the switch control element is a PMOS tube; The gate of the PMOS tube receives the control signal output by the controller, the source is connected to the power supply, and the drain is connected to the coil.

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