Fault detection circuit, detection method and air conditioner

Abstract

The application discloses a fault detection circuit, a detection method and an air conditioner. The fault detection circuit comprises a first detection circuit composed of a first detection unit and a first signal transmission unit, a second detection circuit composed of a second detection unit and a second signal transmission unit, and a relay circuit. The detection method is that the first signal transmission unit is connected to the first detection unit or the second detection unit through the relay circuit to determine the fault position, so that the technical problems of a complicated fault detection process and high time cost when the switch quantity detection circuit is abnormal are solved.

Description

Technical Field

[0001] This invention relates to the field of fault detection technology, and in particular to fault detection circuits, detection methods, and air conditioners. Background Technology

[0002] Currently, optocouplers are generally used in the switching detection circuits of air conditioning or water heater units. When the switching detection circuit malfunctions, it directly affects the user's needs and safety, requiring troubleshooting and step-by-step testing to determine whether the problem lies with the switch and its connected terminals or other components such as the optocoupler. This fault diagnosis process is cumbersome and time-consuming. In addition, commercial water heaters include both circulating and direct-heating units, both of which use the same mainboard. Therefore, some load-related circuits, such as switches, may not be used, resulting in wasted resources. Summary of the Invention

[0003] In order to solve the technical problems of complex and time-consuming fault detection process when the switch quantity detection circuit is abnormal in the prior art, the present invention proposes a fault detection circuit, detection method and air conditioner.

[0004] The technical solution adopted in this invention is:

[0005] A fault detection circuit is proposed, comprising a first detection circuit consisting of a first detection unit and a first signal transmission unit connected together, and a second detection circuit consisting of a second detection unit and a second signal transmission unit connected together. The circuit is characterized in that it further comprises a relay circuit connecting the first detection unit, the second detection unit, and the first signal transmission unit, and the relay circuit is capable of switching the connection of the first signal transmission unit to the first detection unit or the second detection unit.

[0006] Furthermore, the first detection unit includes: resistor R1, resistor R2, resistor R3, capacitor C1, and optocoupler U1;

[0007] In this configuration, the first end of the control terminal of the optocoupler U1 is connected to the relay circuit as the input terminal of the first signal transmission unit, and the second end is connected to ground after being connected in series with the resistor R3. The first end of the controlled terminal of the optocoupler U1 is connected to the power supply after being connected in series with the resistor R1, and the second end is connected to the output terminal of the first signal transmission unit to output the first detection signal. One end of the resistor R2 is connected to the second end of the controlled terminal of the optocoupler U1, and the other end is grounded. One end of the capacitor C1 is connected between the first end of the control terminal of the optocoupler U1 and the relay circuit, and the other end is connected between the second end of the control terminal of the optocoupler U1 and the resistor R3.

[0008] Furthermore, the second detection circuit includes: resistor R4, resistor R5, resistor R6, capacitor C2, and optocoupler U2;

[0009] In this configuration, the first end of the control terminal of the optocoupler U2 is connected to the second detection unit as the input terminal, and the second end is connected to ground after being connected in series with the resistor R6. The first end of the controlled terminal of the optocoupler U2 is connected to the power supply after being connected in series with the resistor R4, and the second end is connected to the output terminal of the second signal transmission unit to output the second detection signal. One end of the resistor R5 is connected to the second end of the controlled terminal of the optocoupler U2, and the other end is grounded. One end of the capacitor C2 is connected between the first end of the control terminal of the optocoupler U2 and the second detection unit, and the other end is connected between the second end of the control terminal of the optocoupler U2 and the resistor R6.

[0010] Furthermore, the relay circuit includes a diode D1 and a relay K1;

[0011] The first terminal of the control terminal of the relay K1 is connected to a control signal, and the second terminal is connected to a power supply. The stationary contact of the controlled terminal of the relay K1 is connected to the first signal transmission unit, the first moving contact is connected to the first detection unit, and the second moving contact is connected to the second detection unit. The positive terminal of the diode D1 is connected to the first terminal of the control terminal of the relay K1, and the negative terminal is connected to the second terminal of the control terminal of the relay K1.

[0012] This invention also proposes a detection method for the fault detection circuit described above:

[0013] When the device under test is faulty, detect the fault state of the device under test;

[0014] Adjust the conduction state of the relay circuit according to the fault condition;

[0015] Acquire a first detection signal and a second detection signal, and determine the fault location of the device under test based on the first detection signal and the second detection signal.

[0016] Furthermore, the fault state includes:

[0017] In the first fault state, when the first signal transmission unit is connected to the first detection unit, the second detection signal is always at a low level during each detection.

[0018] In the second fault state, when the first signal transmission unit is connected to the first detection unit, the second detection signal is at a high level during each detection.

[0019] In the third fault state, when the first signal transmission unit is connected to the first detection unit, the second detection signal is always at a low level and cannot be recovered by the handheld device.

[0020] Furthermore, when the device under test is in a first fault state, the detection method includes:

[0021] Adjust the conduction state of the relay circuit so that the first signal transmission unit is connected to the second detection unit;

[0022] Determine whether the first detection signal is at a low level;

[0023] If not, then the second signal transmission unit is determined to be faulty;

[0024] If so, the second signal transmission unit is determined to be normal.

[0025] Furthermore, when the device under test is in a second fault state, the detection method includes:

[0026] When the second detection signal remains high for a first preset time, the conduction state of the relay circuit is adjusted so that the first signal transmission unit is connected to the second detection unit.

[0027] Determine whether a low-level signal exists in the first detection signal within a second preset time period;

[0028] If not, then the second signal transmission unit is determined to be normal;

[0029] If so, the second signal transmission unit is determined to be faulty.

[0030] Furthermore, when the device under test is in a second fault state, before the first detection signal has a low level signal and the second signal transmission unit is determined to be faulty, the detection method further includes: adjusting the conduction state of the relay circuit so that the first signal transmission unit is connected to the first detection unit;

[0031] Determine whether a low-level signal exists in the second detection signal;

[0032] If so, then the second signal transmission unit is determined to be normal;

[0033] If not, then the second signal transmission unit is determined to be faulty.

[0034] Furthermore, when the device under test is in a third fault state, the detection method includes:

[0035] Adjust the conduction state of the relay circuit so that the first signal transmission unit is connected to the second detection unit;

[0036] Determine whether a low-level signal exists in the first detection signal within a third preset time period;

[0037] If not, then the second signal transmission unit is determined to be faulty;

[0038] If so, the second signal transmission unit is determined to be normal.

[0039] Furthermore, when the device under test is in a third fault state, before determining that the second signal transmission unit is faulty due to a low-level signal in the first detection signal, the detection method further includes:

[0040] The conduction state of the relay circuit is periodically switched so that the first signal transmission unit is periodically switched to be connected to the first signal detection unit or the second signal detection unit.

[0041] Determine whether the first detection signal contains a low-level signal;

[0042] If so, the second signal transmission unit is determined to be normal.

[0043] The present invention also proposes an air conditioner having a fault detection circuit as described above.

[0044] Compared with the prior art, the present invention has at least the following beneficial effects:

[0045] This invention overcomes the shortcomings of existing technologies by integrating and utilizing some load circuits such as switches in the motherboard to detect the fault location of abnormal switch quantity detection circuits. This solves the technical problems of cumbersome and time-consuming fault detection processes in existing technologies when switch quantity detection circuits malfunction, avoiding potential safety hazards. Furthermore, users do not need to incur additional time costs due to repairs, and daily use is not affected. Secondly, it fully utilizes motherboard resources to optimize the detection and control of the unit's operation, reducing downtime due to faults. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a circuit connection diagram of an embodiment of the present invention;

[0048] Figure 2 This is a timing diagram of the circuit switching in the first embodiment of the present invention;

[0049] Figure 3 This is a timing diagram of circuit switching in the second embodiment of the present invention. Detailed Implementation

[0050] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0051] Therefore, a feature pointed out in this specification is used to describe one feature of one embodiment of the invention, and does not imply that every embodiment of the invention must have the described feature. Furthermore, it should be noted that this specification describes many features. Although certain features may be combined to illustrate possible system designs, these features may also be used in other combinations not explicitly stated. Therefore, unless otherwise stated, the described combinations are not intended to be limiting.

[0052] The principles and structure of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0053] Currently, optocouplers are generally used in the switching detection circuits of air conditioning or water heater units. When the switching detection circuit malfunctions, it directly affects the user's needs and safety, requiring troubleshooting and step-by-step testing to determine whether the problem lies with the switch and its connected terminals or other components such as the optocoupler. This fault diagnosis process is cumbersome and time-consuming. In addition, commercial water heaters include both circulating and direct-heating units, both of which use the same mainboard. Therefore, some load-related circuits, such as switches, may not be used, resulting in wasted resources.

[0054] Therefore, in order to solve the technical problem of complex and cumbersome fault detection process when the switch quantity detection circuit is abnormal in the prior art, the present invention proposes a fault detection circuit, including:

[0055] The first detection circuit includes a first detection unit and a first signal transmission unit, used to detect a first switching quantity;

[0056] The second detection circuit includes a second detection unit and a second signal transmission unit, used to detect the second switching quantity;

[0057] A relay circuit is used to switch the connection of the first signal transmission unit to the first detection unit or the second detection unit.

[0058] The present invention also proposes a control method, comprising:

[0059] When the device under test is faulty, the fault state of the device under test is detected; the conduction state of the relay circuit is adjusted according to the fault state; a first detection signal and a second detection signal are acquired, and the fault location of the device under test is determined according to the first detection signal and the second detection signal.

[0060] Its working principle is as follows: when the device under test (DUT) malfunctions, a relay circuit switches the connection of the first signal transmission unit to either the first or second detection unit to obtain a detection signal, thereby determining the location of the fault in the DUT. In summary, the fault detection circuit and control method proposed in this invention obtain corresponding detection signals through relay circuit switching to confirm the location of the fault in the DUT, solving the problem of high time costs in existing technologies where, when a switch quantity detection circuit malfunctions, step-by-step repair and testing are required to determine the fault location.

[0061] The fault detection circuit and control method proposed in this invention are applicable to fault detection of switch quantity detection circuits in air conditioning or water heater units. Generally, switch quantity detection circuits in air conditioning or water heater units use optocoupler components. Specifically, their operation is as follows: Under normal conditions, the switch contacts are normally closed, the optocoupler is always conducting, and it outputs a high-level signal; when the system pressure rises to the level that would cause the high-pressure switch to disconnect, the pressure diaphragm in the switch flips, the switch contacts automatically open, the optocoupler stops conducting, and it outputs a low-level signal.

[0062] In a preferred embodiment of the present invention, the fault detection circuit and control method proposed in the present invention are applied to the high-pressure switch detection circuit and the water pressure switch detection circuit in a water heater unit.

[0063] When the optocoupler circuit in the high-pressure switch detection circuit is normal, according to the water heater unit's operating logic, if high-pressure protection is detected within 3 consecutive seconds, the unit enters the [shutdown sequence]. If the switch recovers after 10 seconds (i.e., the system pressure drops below the pressure at which the high-pressure switch was disconnected, and the high-pressure switch is short-circuited), operation will automatically resume. If this repeats 3 times, the unit enters the [unrecoverable fault] state, which needs to be manually cleared using a handheld device. Under normal circumstances, with the high-pressure switch short-circuited, the optocoupler remains conductive. When the system pressure reaches the pressure at which the high-pressure switch was disconnected, the diaphragm in the switch flips, the switch contacts automatically open, the optocoupler stops conducting, and a low-level signal is output, causing the unit to report a high-pressure protection fault.

[0064] When the optocoupler circuit in the high-voltage switch detection circuit malfunctions, the unit will report a high-voltage protection fault even after only one report (this means the malfunction occurred within the first, second, or third report under normal conditions). When manually cleared using the handheld device, the unit will remain in standby mode and cannot start. Even with the handheld device, it will continue to report high-voltage protection, meaning the optocoupler will continuously output a low-level signal, and the unit will report high-voltage protection. The possible causes of this high-voltage switch detection circuit malfunction are:

[0065] 1. Even when the system pressure is lower than the pressure at which the high-voltage switch is disconnected, the terminals of the high-voltage switch that should be short-circuited remain open, indicating that the fault is in the switch and its connected terminals.

[0066] 2. Even when the terminals connected to the high-voltage switch are short-circuited, the optocoupler, which should be conducting, remains in a non-conducting state, indicating that the fault is in the optocoupler.

[0067] As mentioned above, there are two reasons for abnormalities in the high-voltage switch detection circuit. When the high-voltage switch detection circuit malfunctions, it is necessary to perform step-by-step repairs to identify the fault location, resulting in high time costs.

[0068] Therefore, the present invention proposes a fault detection circuit, comprising a first detection circuit, a second detection circuit, and a relay circuit. The first detection circuit is composed of a first detection unit connected to a first signal transmission unit; the second detection circuit is composed of a second detection unit connected to a second signal transmission unit; the relay circuit connects the first detection unit, the second detection unit, and the first signal transmission unit, and the relay circuit can switch the connection of the first signal transmission unit to either the first detection unit or the second detection unit.

[0069] Please see Figure 1 This is a circuit connection diagram according to a preferred embodiment of the present invention. In this embodiment, the fault detection circuit provided by the present invention includes a first detection circuit, a second detection circuit, and a relay circuit. The first detection circuit, composed of a first detection unit CN2 and a first signal transmission unit, is a water pressure switch detection circuit; the second detection circuit, composed of a second detection unit CN1 and a second signal transmission unit, is a high-voltage switch detection circuit.

[0070] Furthermore, in other embodiments of the present invention, the detection unit may be other switch detection units.

[0071] Please see Figure 1 In this embodiment, two detection units are provided, namely a first detection unit and a second detection unit. The first detection unit consists of resistors R1, R2, and R3, capacitor C1, and optocoupler U1.

[0072] The second detection unit consists of resistors R1, R2, and R3, capacitor C1, and optocoupler U1.

[0073] Here, the circuit structures of the first detection unit and the second detection unit are completely identical. Therefore, the working principle of the present invention will be explained below using the first detection unit. Specifically, the first detection unit includes resistors R1, R2, and R3, capacitor C1, and optocoupler U1.

[0074] In this configuration, the first end of the control terminal of optocoupler U1 (port 4 of U1) is connected to the relay circuit as the input terminal of the first signal transmission unit, and the second end (port 3 of U1) is connected to ground after being connected in series with resistor R3. The first end of the controlled terminal of optocoupler U1 (port 1 of U1) is connected to the power supply after being connected in series with resistor R1, and the second end (port 2 of U1) is connected to the output terminal of the first signal transmission unit to output the first detection signal. One end of resistor R2 is connected to the second end of the controlled terminal of optocoupler U1 (port 2 of U1), and the other end is grounded. One end of capacitor C1 is connected between the first end of the control terminal of optocoupler U1 (port 4 of U1) and the relay circuit, and the other end is connected between the second end of the control terminal of optocoupler U1 and resistor R3.

[0075] The working principle of the first detection unit is as follows: When the first terminal of the control end of optocoupler U1 (port 4 of U1), acting as the input terminal of the first signal transmission unit, receives a high-level signal, optocoupler U1 is turned on, and the second terminal of the controlled end of optocoupler U1 (port 2 of U1), acting as the output terminal of the first signal transmission unit, outputs a high-level detection signal. When the first terminal of the control end of optocoupler U1 (port 4 of U1), acting as the input terminal of the first signal transmission unit, receives a low-level signal, optocoupler U1 is not turned on, and the second terminal of the controlled end of optocoupler U1 (port 2 of U1), acting as the output terminal of the first signal transmission unit, outputs a low-level detection signal. Similarly, the working principle of the second detection unit is the same as that of the first detection unit: when a high-level signal is received, the optocoupler is turned on and outputs a high-level signal; when a low-level signal is received, the optocoupler is not turned on and outputs a low-level signal.

[0076] The relay circuit in the fault detection circuit proposed in this invention includes a diode D1 and a relay K1;

[0077] Specifically, the first terminal (port 1 of K1) of the control terminal of relay K1 is connected to a control signal MCU_CHANGE, and the second terminal (port 5 of K1) is connected to a 12V power supply. The stationary contact (port 2 of K1) of the controlled terminal of relay K1 is connected to the first signal transmission unit, the first moving contact (port 3 of K1) is connected to the first detection unit CN2, and the second moving contact (port 4 of K1) is connected to the second detection unit CN1. The positive terminal of diode D1 is connected to the first terminal (port 1 of K1) of the control terminal of relay K1, and the negative terminal is connected to the second terminal (port 5 of K1) of the control terminal of relay K1.

[0078] The relay circuit works as follows: The second terminal (port 2 of K1) of the control terminal of relay K1 is connected to a 12V power supply, and the first terminal (port 1 of K1) of the control terminal of relay K1 is connected to the control signal MCU-CHANGE. When the control signal MCU-CHANGE outputs a low-level signal to the first terminal (port 1 of K1) of the control terminal of relay K1, relay K1 controls the stationary contact (port 2 of K1) of the controlled terminal of relay K1 to connect to the first moving contact (port 3 of K1), that is, the first signal transmission unit is connected to the first detection unit CN2; when the control signal MCU-CHANGE outputs a high-level signal to the first terminal (port 1 of K1) of the control terminal of relay K1, relay K1 controls the stationary contact (port 2 of K1) of the controlled terminal of relay K1 to connect to the second moving contact (port 4 of K1), that is, the first signal transmission unit is connected to the second detection unit CN1.

[0079] This invention also proposes a detection method for the fault detection circuit described above:

[0080] When the device under test (DUT) is faulty, the fault state of the DUT is detected; the conduction state of the relay circuit is adjusted according to the fault state; a first detection signal and a second detection signal are acquired, and the fault location of the DUT is determined based on the first detection signal and the second detection signal.

[0081] Specifically, there are three fault states of the device under test:

[0082] In the first fault state, when the first signal transmission unit is connected to the first detection unit, the second detection signal is always at a low level during each detection.

[0083] In the second fault state, when the first signal transmission unit is connected to the first detection unit, the second detection signal is at a high level during each detection.

[0084] In the third fault state, when the first signal transmission unit is connected to the first detection unit, the second detection signal is always at a low level and cannot be recovered by the handheld device.

[0085] When the device under test is in the first fault state, the detection method is as follows:

[0086] Adjust the conduction state of the relay circuit to connect the first signal transmission unit to the second detection unit; determine whether the first detection signal is low level;

[0087] If not, the second signal transmission unit is determined to be faulty; if yes, the second signal transmission unit is determined to be normal.

[0088] When the device under test is in the second fault state, the detection method is as follows:

[0089] When the second detection signal remains high for a first preset time, the conduction state of the relay circuit is adjusted so that the first signal transmission unit is connected to the second detection unit; it is then determined whether a low-level signal exists in the first detection signal within the second preset time.

[0090] If not, the second signal transmission unit is determined to be normal; if yes, the second signal transmission unit is determined to be faulty.

[0091] Furthermore, when the device under test is in a second fault state, before determining that the second signal transmission unit is faulty due to the presence of a low-level signal in the first detection signal, the detection method further includes: adjusting the conduction state of the relay circuit to connect the first signal transmission unit to the first detection unit; and determining whether a low-level signal exists in the second detection signal.

[0092] If yes, the second signal transmission unit is determined to be normal; if no, the second signal transmission unit is determined to be faulty.

[0093] When the device under test is in the third fault state, the detection method is as follows:

[0094] Adjust the conduction state of the relay circuit to connect the first signal transmission unit to the second detection unit; determine whether a low-level signal exists in the first detection signal within a third preset time period;

[0095] If not, the second signal transmission unit is determined to be faulty; if yes, the second signal transmission unit is determined to be normal.

[0096] When the device under test is in the third fault state, before determining that the second signal transmission unit is faulty due to the presence of a low-level signal in the first detection signal, the detection method also includes:

[0097] The conduction state of the relay circuit is periodically switched, causing the first signal transmission unit to periodically switch between being connected to the first signal detection unit or the second signal detection unit; it is determined whether there is a low-level signal in the first detection signal; if so, the second signal transmission unit is determined to be normal.

[0098] Please see Figure 1 In the first embodiment of the present invention, the water heater is a direct-heating model. The direct-heating model is characterized by the following: under normal conditions, the water pressure switch detection circuit is used to detect the water pressure, and the high-pressure switch detection circuit is used to detect the high-pressure condition. The water pressure switch detection circuit in the water heater unit is a first detection circuit, the high-pressure switch detection circuit is a second detection circuit, the optocoupler circuit connected to the water pressure switch is a first signal transmission unit, the optocoupler circuit connected to the high-pressure switch is a second signal transmission unit, the water pressure switch terminal is the first detection unit CN2, and the high-pressure switch terminal is the second detection unit CN1.

[0099] Under normal operating conditions, the control signal MCU_CHANGE outputs a low-level signal, and the stationary contact (port 2 of K1) of the controlled terminal of relay K1 is connected to the first moving contact (port 3 of K1), that is, the optocoupler circuit of the water pressure switch is connected to the water pressure switch terminal CN2.

[0100] Please see Figure 2 This is a timing diagram of the circuit switching in the first embodiment of the present invention. t1 is set as the time when the optocoupler circuit connected to the water pressure switch is connected to the high-voltage switch terminal, and t2 is set as the time when the optocoupler circuit connected to the water pressure switch is connected to the water pressure switch terminal.

[0101] When the high-voltage switch detection circuit malfunctions, and the malfunction condition is that the second detection signal MCU_HP remains low during each detection, resulting in a high-voltage protection event, the conduction state of the relay circuit is periodically switched, causing the optocoupler circuit connected to the water pressure switch to periodically switch between the water pressure switch terminal CN2 and the high-voltage switch terminal CN1. When the optocoupler circuit connected to the water pressure switch is connected to the high-voltage switch terminal, the first detection signal MCU_SHUIYA is actually the high-voltage switch detection signal, and it is determined whether the first detection signal MCU_SHUIYA is a low-level signal within a continuous time interval t1.

[0102] If so, it means that the system pressure has reached the pressure that would cause the high-pressure switch to disconnect. When the high-pressure switch disconnects, the optocoupler is not conducting, and the second detection signal MCU_HP outputs a low-level signal. Therefore, when the optocoupler circuit connected to the water pressure switch is connected to the high-pressure switch terminal CN1, the first detection signal MCU_SHUIYA also outputs a low-level signal, thus determining that the optocoupler circuit connected to the high-pressure switch is normal.

[0103] If not, it means that the system pressure has not reached the pressure that would cause the high-pressure switch to disconnect. The high-pressure switch is short-circuited, and the optocoupler is conducting. Therefore, when the optocoupler circuit connected to the water pressure switch is connected to the high-pressure switch terminal CN1, the first detection signal MCU_SHUIYA outputs a high-level signal. However, when the high-pressure switch is short-circuited, the second detection signal MCU_HP, which should output a high-level signal, outputs a low-level signal. Therefore, it is determined that the optocoupler circuit connected to the high-pressure switch has malfunctioned.

[0104] When the high-pressure switch detection circuit malfunctions, and the malfunction occurs when the second detection signal remains high for a continuous period t2, meaning the high-pressure protection does not activate during the water heater's hot water mode, the relay circuit periodically switches its conduction state, causing the optocoupler circuit connected to the water pressure switch to periodically switch between the water pressure switch terminal CN2 and the high-pressure switch terminal CN1. Within a continuous period t1, it is determined whether the first detection signal MCU_SHUIYA is low.

[0105] If not, it means that the system pressure has not reached the pressure that would cause the high-pressure switch to disconnect. The high-pressure switch is short-circuited, and the optocoupler is on. Therefore, the second detection signal MCU_HP is always a high-level signal. When the optocoupler circuit connected to the water pressure switch is connected to the high-pressure switch terminal CN1, the first detection signal MCU_SHUIYA is also a high-level signal. In this case, it is determined that the optocoupler circuit connected to the high-pressure switch is normal, and the current relay circuit continues to poll and switch the optocoupler circuit connected to the water pressure switch terminal CN2 or the high-pressure switch terminal CN1 during the t2-t1 time interval to continue detection.

[0106] If so, there are two possible scenarios: ① The system pressure reaches the pressure that would cause the high-pressure switch to disconnect, so when the optocoupler circuit connected to the water pressure switch is connected to terminal CN1 of the high-pressure switch, the first detection signal MCU_SHUIYA is a low-level signal. However, due to a fault in the optocoupler circuit connected to the high-pressure switch, the second detection signal remains a high-level signal. ② The system pressure did not reach the pressure that would cause the high-pressure switch to disconnect before the relay circuit switched, but after the relay circuit switched, the system pressure rose and reached the pressure that would cause the high-pressure open pipe to disconnect. Therefore, further testing and confirmation are needed, and it is preliminarily determined that the optocoupler circuit connected to the high-pressure switch is faulty. Adjust the conduction state of the relay circuit so that the optocoupler circuit connected to the water pressure switch is connected to terminal CN2 of the water pressure switch, and check whether the second detection signal MCU_HP is a low-level signal within a continuous time t3. If not, it indicates that scenario ① is true, and it is determined that the optocoupler circuit connected to the high-pressure switch is faulty. If so, it means that situation ② above is true. Then it is determined that the optocoupler circuit connected to the high-voltage switch is normal, and the current relay circuit continues to poll and switch the optocoupler circuit connected to the water pressure switch to the water pressure switch terminal CN2 or the high-voltage switch terminal CN1 for testing.

[0107] When the high-voltage switch detection circuit malfunctions, and the second detection signal remains low and cannot be recovered via the handheld device (i.e., after the high-voltage protection alarm reaches an unrecoverable number of times, it continues to alarm even after manual clearing via the handheld device, or it remains unrecoverable regardless of the number of times the high-voltage protection alarm occurs), the conduction state of the relay circuit is periodically switched, causing the optocoupler circuit connected to the water pressure switch to periodically switch between the water pressure switch terminal CN2 and the high-voltage switch terminal CN1. When the optocoupler circuit connected to the water pressure switch is connected to the high-voltage switch terminal, the first detection signal MCU_SHUIYA is actually the high-voltage switch detection signal, and it is determined whether the first detection signal MCU_SHUIYA is a low-level signal within a continuous time interval t1.

[0108] If so, it means that the system pressure has reached the pressure that would cause the high-pressure switch to disconnect. When the high-pressure switch disconnects, the optocoupler is not conducting, and the second detection signal MCU_HP outputs a low-level signal. Therefore, when the optocoupler circuit connected to the water pressure switch is connected to the high-pressure switch terminal CN1, the first detection signal MCU_SHUIYA also outputs a low-level signal, thus determining that the optocoupler circuit connected to the high-pressure switch is normal.

[0109] If not, it means that the system pressure has not reached the pressure required to disconnect the high-pressure switch. The high-pressure switch is short-circuited, and the optocoupler is on. Therefore, when the optocoupler circuit connected to the water pressure switch is connected to the high-pressure switch terminal CN1, the first detection signal MCU_SHUIYA outputs a high-level signal. However, when the high-pressure switch is disconnected, the second detection signal MCU_HP, which should output a high-level signal, outputs a low-level signal. Therefore, it is determined that the optocoupler circuit connected to the high-pressure switch has malfunctioned.

[0110] Please see Figure 1 In the second embodiment of the present invention, the water heater is a circulating water heater. The circulating water heater is characterized by the following: under normal conditions, the water pressure switch detection circuit is idle, and the high-pressure switch detection circuit is used to detect high pressure. The water pressure switch detection circuit in the water heater unit is a first detection circuit, the high-pressure switch detection circuit is a second detection circuit, the optocoupler circuit connected to the water pressure switch is a first signal transmission unit, the optocoupler circuit connected to the high-pressure switch is a second signal transmission unit, the water pressure switch terminal is the first detection unit CN2, and the high-pressure switch terminal is the second detection unit CN1.

[0111] Under normal operating conditions, the control signal MCU_CHANGE outputs a low-level signal, and the stationary contact (port 2 of K1) of the controlled terminal of relay K1 is connected to the first moving contact (port 3 of K1), that is, the optocoupler circuit of the water pressure switch is connected to the water pressure switch terminal CN2.

[0112] Please see Figure 3 This is a timing diagram of the circuit switching in the second embodiment of the present invention. t1 is set as the time when the optocoupler circuit connected to the water pressure switch is connected to the high-voltage switch terminal, and t2 is set as the time when the optocoupler circuit connected to the water pressure switch is connected to the water pressure switch terminal.

[0113] When the high-voltage switch detection circuit malfunctions, and the malfunction condition is that the second detection signal MCU_HP remains low during each detection, resulting in a high-voltage protection event, the conduction state of the switching relay circuit is activated, connecting the optocoupler circuit connected to the water pressure switch to the high-voltage switch terminal CN1. When the optocoupler circuit connected to the water pressure switch is connected to the high-voltage switch terminal CN1, the first detection signal MCU_SHUIYA is actually the high-voltage switch detection signal. Within a continuous time interval t1, it is determined whether the first detection signal MCU_SHUIYA is a low-level signal.

[0114] If so, it means that the system pressure has reached the pressure that would cause the high-pressure switch to disconnect. When the high-pressure switch disconnects, the optocoupler is not conducting, and the second detection signal MCU_HP outputs a low-level signal. Therefore, when the optocoupler circuit connected to the water pressure switch is connected to the high-pressure switch terminal CN1, the first detection signal MCU_SHUIYA also outputs a low-level signal, thus determining that the optocoupler circuit connected to the high-pressure switch is normal.

[0115] If not, it means that the system pressure has not reached the pressure required to disconnect the high-pressure switch. The high-pressure switch is short-circuited, and the optocoupler is conducting. Therefore, when the optocoupler circuit connected to the water pressure switch is connected to the high-pressure switch terminal CN1, the first detection signal MCU_SHUIYA outputs a high-level signal. However, when the high-pressure switch is short-circuited, the second detection signal MCU_HP, which should output a high-level signal, outputs a low-level signal. This indicates that the optocoupler circuit connected to the high-pressure switch has malfunctioned, and the optocoupler circuit connected to the water pressure switch is fixed to the high-pressure switch terminal CN1 and no longer switched.

[0116] When the high-pressure switch detection circuit malfunctions, and the malfunction occurs when the second detection signal remains high for a continuous period t2 (i.e., the water heater unit does not activate high-pressure protection during hot water mode), the relay circuit's conduction state is switched, causing the optocoupler circuit connected to the water pressure switch to switch to the high-pressure switch terminal CN1. Within a continuous period t1, it is determined whether the first detection signal MCU_SHUIYA is low.

[0117] If not, it means that the system pressure has not reached the pressure that would cause the high-pressure switch to disconnect. The high-pressure switch is short-circuited, and the optocoupler is on. Therefore, the second detection signal MCU_HP is always a high-level signal. When the optocoupler circuit connected to the water pressure switch is connected to the high-pressure switch terminal CN1, the first detection signal MCU_SHUIYA is also a high-level signal. It is then determined that the optocoupler circuit connected to the high-pressure switch is normal, and the current relay circuit continues to poll and switch the optocoupler circuit connected to the water pressure switch terminal CN2 or the high-pressure switch terminal CN1 during the t2-t1 time interval to continue detection.

[0118] If so, there are two possible scenarios: ① The system pressure has reached the pressure required to disconnect the high-pressure switch, so when the optocoupler circuit connected to the water pressure switch is connected to terminal CN1 of the high-pressure switch, the first detection signal MCU_SHUIYA is a low-level signal. However, due to a fault in the optocoupler circuit connected to the high-pressure switch, the second detection signal remains a high-level signal. ② The system pressure did not reach the pressure required to disconnect the high-pressure switch before the relay circuit switched, but reached the pressure required to disconnect the high-pressure open pipe after the relay circuit switched. Therefore, further testing and confirmation are needed, and it is preliminarily determined that the optocoupler circuit connected to the high-pressure switch is faulty. Adjust the conduction state of the relay circuit so that the optocoupler circuit connected to the water pressure switch is connected to terminal CN2 of the water pressure switch. Detect whether the second detection signal MCU_HP is a low-level signal within a continuous time t3. If not, it indicates that scenario ① is true, and it is determined that the optocoupler circuit connected to the high-pressure switch is faulty. Fix the optocoupler circuit connected to the water pressure switch to terminal CN1 of the high-pressure switch and do not switch it again. If so, it means that situation ② above is true. Then it is determined that the optocoupler circuit connected to the high-voltage switch is normal, and the current relay circuit continues to poll and switch the optocoupler circuit connected to the water pressure switch to the water pressure switch terminal CN2 or the high-voltage switch terminal CN1 for testing.

[0119] When the high-voltage switch detection circuit malfunctions, and the second detection signal remains low and cannot be recovered via the handheld device (i.e., after the high-voltage protection alarm reaches an unrecoverable number of times, it continues to alarm even after manual clearing via the handheld device, or it remains unrecoverable regardless of the number of times the high-voltage protection alarm occurs), the switching relay circuit's conduction state is activated, causing the optocoupler circuit connected to the water pressure switch to switch to the high-voltage switch terminal CN1. When the optocoupler circuit connected to the water pressure switch is connected to the high-voltage switch terminal, the first detection signal MCU_SHUIYA is actually the high-voltage switch detection signal. Within a continuous time interval t1, it is determined whether the first detection signal MCU_SHUIYA is a low-level signal.

[0120] If so, it means that the system pressure has reached the pressure that would cause the high-pressure switch to disconnect. When the high-pressure switch disconnects, the optocoupler is not conducting, and the second detection signal MCU_HP outputs a low-level signal. Therefore, when the optocoupler circuit connected to the water pressure switch is connected to the high-pressure switch terminal CN1, the first detection signal MCU_SHUIYA also outputs a low-level signal, thus determining that the optocoupler circuit connected to the high-pressure switch is normal.

[0121] If not, it means that the system pressure has not reached the pressure required to disconnect the high-pressure switch. The high-pressure switch is short-circuited, and the optocoupler is conducting. Therefore, when the optocoupler circuit connected to the water pressure switch is connected to the high-pressure switch terminal CN1, the first detection signal MCU_SHUIYA outputs a high-level signal. However, the second detection signal MCU_HP, which should output a high-level signal when the high-pressure switch is short-circuited, outputs a low-level signal. This indicates that the optocoupler circuit connected to the high-pressure switch has malfunctioned, and the optocoupler circuit connected to the water pressure switch is fixed to the high-pressure switch terminal CN1, and no further switching is performed.

[0122] Furthermore, the present invention also proposes an air conditioner having the above-mentioned fault detection circuit.

[0123] This invention overcomes the shortcomings of existing technologies by integrating and utilizing some load circuits such as switches in the motherboard to detect the fault location of abnormal switch quantity detection circuits. This solves the technical problems of cumbersome and time-consuming fault detection processes in existing technologies when switch quantity detection circuits malfunction, avoiding potential safety hazards. Furthermore, users do not need to incur additional time costs due to repairs, and daily use is not affected. Secondly, it fully utilizes motherboard resources to optimize the detection and control of the unit's operation, reducing downtime due to faults.

[0124] 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 within the protection scope of the present invention.

Claims

1. A fault detection circuit, comprising a first detection circuit consisting of a first detection unit and a first signal transmission unit connected together, and a second detection circuit consisting of a second detection unit and a second signal transmission unit connected together, characterized in that, It also includes a relay circuit that connects the first detection unit, the second detection unit, and the first signal transmission unit, and the relay circuit can switch the connection of the first signal transmission unit to the first detection unit or the second detection unit; The relay circuit includes diode D1 and relay K1; The first terminal of the control terminal of the relay K1 is connected to a control signal, and the second terminal is connected to a power supply. The stationary contact of the controlled terminal of the relay K1 is connected to the first signal transmission unit, the first moving contact is connected to the first detection unit, and the second moving contact is connected to the second detection unit. The positive terminal of the diode D1 is connected to the first terminal of the control terminal of the relay K1, and the negative terminal is connected to the second terminal of the control terminal of the relay K1.

2. The fault detection circuit according to claim 1, characterized in that, The first detection unit includes: resistor R1, resistor R2, resistor R3, capacitor C1, and optocoupler U1; In this configuration, the first end of the control terminal of the optocoupler U1 is connected to the relay circuit as the input terminal of the first signal transmission unit, and the second end is connected to ground after being connected in series with the resistor R3. The first end of the controlled terminal of the optocoupler U1 is connected to the power supply after being connected in series with the resistor R1, and the second end is connected to the output terminal of the first signal transmission unit to output the first detection signal. One end of the resistor R2 is connected to the second end of the controlled terminal of the optocoupler U1, and the other end is grounded. One end of the capacitor C1 is connected between the first end of the control terminal of the optocoupler U1 and the relay circuit, and the other end is connected between the second end of the control terminal of the optocoupler U1 and the resistor R3.

3. The fault detection circuit according to claim 1, characterized in that, The second detection circuit includes: resistor R4, resistor R5, resistor R6, capacitor C2, and optocoupler U2; In this configuration, the first end of the control terminal of the optocoupler U2 is connected to the second detection unit as the input terminal, and the second end is connected to ground after being connected in series with the resistor R6. The first end of the controlled terminal of the optocoupler U2 is connected to the power supply after being connected in series with the resistor R4, and the second end is connected to the output terminal of the second signal transmission unit to output the second detection signal. One end of the resistor R5 is connected to the second end of the controlled terminal of the optocoupler U2, and the other end is grounded. One end of the capacitor C2 is connected between the first end of the control terminal of the optocoupler U2 and the second detection unit, and the other end is connected between the second end of the control terminal of the optocoupler U2 and the resistor R6.

4. A detection method applied to the fault detection circuit as described in any one of claims 1 to 3, characterized in that, When the device under test is faulty, detect the fault state of the device under test; Adjust the conduction state of the relay circuit according to the fault condition; Acquire a first detection signal and a second detection signal, and determine the fault location of the device under test based on the first detection signal and the second detection signal.

5. The fault detection circuit detection method according to claim 4, characterized in that, The fault states include: In the first fault state, when the first signal transmission unit is connected to the first detection unit, the second detection signal is always at a low level during each detection. In the second fault state, when the first signal transmission unit is connected to the first detection unit, the second detection signal is at a high level during each detection. In the third fault state, when the first signal transmission unit is connected to the first detection unit, the second detection signal is always at a low level and cannot be recovered by the handheld device.

6. The detection method for the fault detection circuit according to claim 5, characterized in that, When the device under test is in a first fault state, the detection method includes: Adjust the conduction state of the relay circuit so that the first signal transmission unit is connected to the second detection unit; Determine whether the first detection signal is at a low level; If not, then the second signal transmission unit is determined to be faulty; If so, the second signal transmission unit is determined to be normal.

7. The fault detection circuit detection method according to claim 5, characterized in that, When the device under test is in a second fault state, the detection method includes: When the second detection signal remains high for a first preset time, the conduction state of the relay circuit is adjusted so that the first signal transmission unit is connected to the second detection unit. Determine whether a low-level signal exists in the first detection signal within a second preset time period; If not, then the second signal transmission unit is determined to be normal; If so, the second signal transmission unit is determined to be faulty.

8. The detection method for the fault detection circuit according to claim 7, characterized in that, When the device under test is in a second fault state, before the first detection signal has a low level signal and the second signal transmission unit is determined to be faulty, the detection method further includes: adjusting the conduction state of the relay circuit so that the first signal transmission unit is connected to the first detection unit. Determine whether a low-level signal exists in the second detection signal; If so, then the second signal transmission unit is determined to be normal; If not, then the second signal transmission unit is determined to be faulty.

9. The detection method for the fault detection circuit according to claim 5, characterized in that, When the device under test is in a third fault state, the detection method includes: Adjust the conduction state of the relay circuit so that the first signal transmission unit is connected to the second detection unit; Determine whether a low-level signal exists in the first detection signal within a third preset time period; If not, then the second signal transmission unit is determined to be faulty; If so, the second signal transmission unit is determined to be normal.

10. The detection method for the fault detection circuit according to claim 9, characterized in that, When the device under test is in a third fault state, before the first detection signal does not have a low-level signal and the second signal transmission unit is determined to be faulty, the detection method further includes: The conduction state of the relay circuit is periodically switched so that the first signal transmission unit is periodically switched to be connected to the first signal detection unit or the second signal detection unit. Determine whether the first detection signal contains a low-level signal; If so, the second signal transmission unit is determined to be normal.

11. An air conditioner, characterized in that, The air conditioner has a fault detection circuit as described in any one of claims 1 to 3.

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