Protection device and protection method for combustible refrigerant and refrigerator

Abstract

The embodiment of the invention provides a flammable refrigerant protection device and method and a refrigerator, and the device comprises a sensor which is used for detecting the concentration of the flammable refrigerant leaked in the air around a pipeline containing the flammable refrigerant; a fan; a live wire of the commercial power is connected in series with upper half knives of the first relay and the second relay, and a null line of the commercial power is connected with a lower half knife of the second relay; and the controller is electrically connected with the sensor, the fan, the first relay and the second relay, and is used for driving the fan to work when the concentration of the combustible refrigerant reaches a first threshold value, and turning off the first relay to disconnect the live wire and then turning off the second relay to disconnect the null line when the concentration of the combustible refrigerant reaches a second threshold value. The first threshold is smaller than the second threshold. According to the combustible refrigerant leakage detection device, timely detection can be carried out when the combustible refrigerant leaks, and corresponding treatment can be carried out according to the leakage concentration of the combustible refrigerant, so that equipment applying the combustible refrigerant can be protected, and the safety of the equipment is improved.

Description

Technical Field

[0001] This application belongs to the field of refrigerator technology, and particularly relates to a protective device, protection method and refrigerator for flammable refrigerants. Background Technology

[0002] Flammable refrigerants such as isobutane have an ozone depletion potential of 0 and offer advantages such as environmental friendliness, economy, and high efficiency in specific applications. Flammable refrigerants such as isobutane are widely used in household appliances, with small charge quantities but are flammable. The internal space of the device is enclosed and there are many ignition sources, which places high demands on the anti-ignition capability of the electrical design.

[0003] Therefore, how to protect equipment that uses flammable refrigerants is an urgent problem to be solved. Summary of the Invention

[0004] This application provides a protective device, method, and refrigerator for flammable refrigerants, which can protect equipment using flammable refrigerants and thus improve equipment safety. In a first aspect, embodiments of this application provide a protective device for flammable refrigerants, applied to a refrigerator, comprising: Sensors are used to detect the concentration of leaked flammable refrigerant in the air around pipes containing flammable refrigerant. A fan is used to blow leaked flammable refrigerant to the outside of the refrigerator; The first relay and the second relay are connected in series with the upper half of the first relay and the upper half of the second relay, and the neutral wire of the mains power is connected to the lower half of the second relay. The controller is electrically connected to the sensor, the fan, the first relay, and the second relay respectively. The controller is used to drive the fan to work when the concentration of the combustible refrigerant reaches a first threshold, and to first turn off the first relay to disconnect the live wire when the concentration of the combustible refrigerant reaches a second threshold, and then turn off the second relay to disconnect the neutral wire. The first threshold is less than the second threshold.

[0005] Optionally, the protective device further includes: The first isolation unit is connected between the sensor and the controller; The second isolation unit is connected between the controller and the first relay and the second relay.

[0006] Optionally, the first isolation unit includes: A sampling unit, one of whose input terminals is connected to the sensor via a voltage divider node, is used to generate sampling data based on the sensor. A first isolation chip has its input terminal connected to an output terminal of the sampling unit and its output terminal connected to the controller. The first isolation chip is used to isolate and transmit the sampled data to the controller.

[0007] Optionally, the first isolation unit further includes: The self-test unit has its output connected to the voltage divider node. The self-test unit is used to inject a microcurrent into the voltage divider node to form an equivalent flammable refrigerant concentration.

[0008] Optionally, the first isolation unit further includes: The protection unit has one end connected to the sensor ground terminal and the other end connected to the sensor power supply terminal. Its controlled terminal is connected to the voltage divider node. The protection unit is used to protect the voltage of the voltage divider node by clamping it between the power rails.

[0009] Optionally, the first isolation unit further includes: The second isolation chip has its input terminal connected to the controller to receive control signals from the controller; A first switching element has one end connected to the heating wire of the sensor, the other end grounded, and its controlled end connected to the second isolation chip. The first switching element is used to close under the control signal transmitted by the second isolation chip, so as to enable the sensor to operate.

[0010] Optionally, the second isolation unit includes: The third isolation chip has its first and second input terminals both connected to the controller, and its output terminal connected to the first and second relays.

[0011] Optionally, the protective device further includes: An isolation converter has two input terminals connected to a first power supply and two output terminals connected to the sensor. The isolation converter is used to isolate and step down the first power supply before outputting it to the sensor and powering the sensor.

[0012] Secondly, embodiments of this application also provide a method for protecting flammable refrigerants, comprising: Detect the concentration of leaked flammable refrigerant in the air surrounding pipelines containing flammable refrigerant; If the concentration of the flammable refrigerant reaches the first threshold, the fan is driven to run in order to blow the leaked flammable refrigerant to the outside of the refrigerator. If the concentration of the flammable refrigerant reaches the second threshold, the first relay and the second relay are turned off in sequence to disconnect both the live wire and the neutral wire of the mains power. The second threshold is greater than the first threshold.

[0013] Thirdly, embodiments of this application also provide a refrigerator, including a protection device for flammable refrigerant as described in any of the preceding claims.

[0014] In the protective device, protection method, and refrigerator for flammable refrigerants in this application embodiment, a sensor is installed to detect the concentration of flammable refrigerant. This allows for timely detection of flammable refrigerant leaks and appropriate actions to be taken based on the leak concentration. This protects equipment using flammable refrigerants and improves equipment safety. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings. In the following description, the same reference numerals denote the same parts.

[0017] Figure 1 A schematic diagram of a protective device for flammable refrigerants provided in an embodiment of this application.

[0018] Figure 2 This is another structural schematic diagram of the protection device for flammable refrigerants provided in the embodiments of this application.

[0019] Figure 3 This is a structural block diagram of the sensor side in the flammable refrigerant protection device provided in the embodiments of this application.

[0020] Figure 4 The diagram shows the structure of the protective device for flammable refrigerants provided in the embodiments of this application in three states.

[0021] Figure 5 A structural block diagram of the execution domain in the protection device for flammable refrigerants provided in the embodiments of this application.

[0022] Figure 6 The circuit diagram of the intrinsically safe power supply in the protection device for flammable refrigerants provided in the embodiments of this application.

[0023] Figure 7 A circuit diagram showing sensor isolation in a protection device for flammable refrigerants provided in an embodiment of this application.

[0024] Figure 8 The circuit diagram of the AC side double cut-off in the protection device for flammable refrigerants provided in the embodiments of this application.

[0025] Figure 9 The circuit diagram of the warning and sparkless fan in the protection device for flammable refrigerants provided in the embodiments of this application.

[0026] Figure 10 The circuit diagram of DC bus discharge in the protection device for flammable refrigerants provided in this application embodiment. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0028] The widespread use of flammable refrigerants, such as isobutane, in household appliances, with small charge quantities but still flammable, and the enclosed internal space of the equipment with multiple ignition sources such as relays, fans, and rectifier buses, places high demands on the anti-ignition capability of the electrical design.

[0029] In related technologies, there are issues with intrinsic safety on the sensing side. Typically, gas sensors are directly connected to the motherboard's 5V or 3.3V, lacking capacity limits and isolation. Short circuits or abnormalities can release energy exceeding the ignition threshold. Furthermore, there is the problem of unprocessed residual energy. Even after AC power is cut off, some models still store tens of joules of energy on the DC bus after rectification / PFC (Power Factor Correction) circuitry, posing a potential hazard of live charging / discharging to downstream stages and contacts. Additionally, there are issues with arcing or surges at the actuator end. Single mechanical relays disconnect at non-zero crossing points, resulting in significant contact arcing and surges. Solid-state relays alone suffer from leakage current and incomplete shut-off. There are also issues with insufficient link reliability. Sensor aging, contamination, or detachment are difficult to self-check promptly. Sampling or control and execution share a common ground, making electromagnetic interference or surges easily introduced into the measurement link, leading to false alarms or missed alarms.

[0030] In view of the above problems, this application provides a protective device, a protective method and a refrigerator for flammable refrigerants, which will be described below with reference to the accompanying drawings.

[0031] For example, please refer to Figure 1 As shown, Figure 1 This is a schematic diagram of a protective device for flammable refrigerants provided in an embodiment of this application. This application provides a protective device 100 for flammable refrigerants; for ease of explanation, the protective device 100 for flammable refrigerants will be referred to simply as protective device 100 below.

[0032] The protection device 100 can be applied to refrigerators, mainly to protect the refrigerator and reduce safety risks caused by flammable refrigerants.

[0033] The protection device 100 includes a sensor 110, a fan 120, a first relay SSR, a second relay K1, and a controller MCU.

[0034] Sensor 110 is used to detect the concentration of leaked flammable refrigerant in the air surrounding a pipeline containing flammable refrigerant. Sensor 110 can be a gas sensor. The core function of a gas sensor is to detect the presence of a target gas and determine its concentration. Its principle is mainly based on the physical or chemical reaction between gas molecules and the sensitive material inside the sensor, resulting in a measurable change in a certain physical or chemical property of the sensitive material. This change is converted into an electrical signal (such as a change in resistance, current, voltage, or frequency), which is then processed and output by a circuit. Depending on the physical or chemical mechanism used, gas sensors can be categorized into semiconductor sensors, electrochemical sensors, catalytic combustion sensors, infrared sensors, etc. This application uses a semiconductor sensor as an example for illustration, and should not be construed as a limitation on sensor 110.

[0035] The core of a semiconductor sensor is a heating element coated with a metal oxide semiconductor. When the sensor is in normal air, oxygen (O2) from the air is adsorbed on the surface of the metal oxide. Oxygen molecules take electrons from the semiconductor lattice to form negative oxygen ions (O2). - O2 - This results in the formation of an electron depletion layer (space charge layer) on the semiconductor surface, leading to a higher resistance value in the sensor. When the sensor is exposed to a target reducing gas (such as H2, CO, CH4, ethanol, propane, etc.), these reducing gases react with adsorbed oxygen ions (mainly through surface catalytic oxidation), releasing electrons back into the semiconductor. The released electrons reduce the thickness of the space charge layer on the semiconductor surface, causing a significant decrease in the overall resistance of the semiconductor material. The degree of this resistance decrease is usually a function of the concentration of the target gas. Conversely, for oxidizing gases (such as O3, Cl2, NO2, etc.), they will draw more electrons from the semiconductor, leading to an increase in resistance.

[0036] The fan 120 is used to disperse leaked flammable refrigerant to the outside of equipment such as a refrigerator. The fan 120 can be separately installed in a space containing flammable refrigerant piping, such as facing the refrigerator's ventilation holes. This facilitates dispersing the leaked flammable refrigerant to the outside of the refrigerator, thereby diluting the flammable refrigerant inside and reducing the risk of ignition. In some embodiments, an existing fan in the refrigerator, such as a refrigerator fan or a freezer fan, can be used. For example, the refrigerator fan can be installed in a sealed box, which may have a first air damper facing the refrigerator compartment and a second air damper facing the refrigerator's ventilation holes. A switch can be used to open the first air damper to blow air into the refrigerator compartment and / or open the second air damper to blow air into the refrigerator's ventilation holes, thereby reducing the need for a separate fan and saving costs.

[0037] The first relay (SSR) and the second relay (K1) are of different types; for example, the first relay (SSR) can be a zero-crossing solid-state relay, while the second relay (K1) can be a mechanical relay. The zero-crossing solid-state relay is a specially designed solid-state relay that turns on when the AC voltage crosses zero and turns off when the current crosses zero, effectively reducing electrical interference and inrush current. The zero-crossing solid-state relay operates through an internal zero-crossing detection circuit. When an input control signal is applied, the relay does not immediately turn on but waits for the AC voltage waveform to cross zero, i.e., the instantaneous voltage value is zero, before turning on the output. Similarly, when the control signal is removed, the relay waits for the load current to cross zero before fully turning off. This mechanism avoids switching at voltage or current peaks, significantly reducing radio frequency interference and impact on the load.

[0038] For example, the live wire of the mains power is connected in series with the upper half of the first relay SSR and the second relay K1, and the neutral wire of the mains power is connected to the lower half of the second relay K1. The upper half of the second relay K1 is also the normally open contact of the mechanical relay, and the lower half of the second relay K1 is also the normally closed contact of the mechanical relay.

[0039] The controller MCU is the control center, or logic operation center, of the protection device 100. The MCU is electrically connected to the sensor 110, the fan 120, the first relay SSR, and the second relay K1. The MCU drives the fan 120 to operate when the flammable refrigerant concentration reaches a first threshold, diluting the leaked flammable refrigerant to the outside of the refrigerator. When the flammable refrigerant concentration reaches a second threshold, it first shuts off the first relay SSR to disconnect the live wire, and then shuts off the second relay K1 to disconnect the neutral wire. The first threshold is less than the second threshold. In other words, the system operates in stages based on isobutane concentration. When the first threshold is reached, an early warning is triggered and the fan 120 is driven to run; when the second threshold is reached, a double AC side cutoff is performed, and the system can only recover after the reset conditions are met.

[0040] It should be noted that both the first threshold and the second threshold can be concentration ranges. For example, the first threshold can be 10%LFL-15%LFL, where %LFL represents the percentage of gas concentration relative to the lower limit; and the second threshold can be 20%LFL-25%LFL.

[0041] In the flammable refrigerant protection device 100 provided in this application embodiment, a sensor 110 is set to detect the concentration of flammable refrigerant. This allows for timely detection of flammable refrigerant leaks and appropriate actions to be taken based on the leak concentration. This protects equipment using flammable refrigerants and improves equipment safety.

[0042] The above are remedial measures taken when a flammable refrigerant leak is detected to a certain concentration, in order to reduce the risk of combustion of the leaked flammable refrigerant. On this basis, in order to reduce the risk of combustion of flammable refrigerant from the source, such as reducing the risk of sparks generated by ignition sources, the embodiments of this application have also made improvements in electrical design.

[0043] For example, please refer to Figure 2 As shown, Figure 2 This is another schematic diagram of the protective device for flammable refrigerants provided in this application embodiment. The protective device 100 also includes a first isolation unit 130 and a second isolation unit 140. The first isolation unit 130 is connected between the sensor 110 and the controller MCU, and the second isolation unit 140 is connected between the controller MCU and an actuator such as a first relay SSR and a second relay K1. It should be noted that by performing three-domain electrical isolation, that is, two isolations between the sensing domain, the control domain, and the execution domain, and by ensuring that the ground wires are not directly connected, and by transmitting signals across domains only through the isolation devices, the risk of sparks causing mutual interference can be reduced from the source, thereby reducing the risk of flammable refrigerant combustion from the source.

[0044] In this regard, please combine Figure 1 and Figure 2 And see Figure 3 As shown, Figure 3This is a block diagram of the sensor side of the protection device for flammable refrigerants provided in this application embodiment. The sensing domain consists of an isolation converter, an energy-limiting grid, a sensor 110, an instrumentation amplifier, an ADC, and a digital isolator. The isolation converter is an isolated DC-DC converter. The energy-limiting grid is composed of Rlim (current limiting), F1 (fuse), and a Zener pair (anti-parallel clamp). The isolation converter outputs a low voltage of 3.3V / 5V, i.e., SELV (Safety Extra-Low Voltage), isolated from mains power or high-voltage power. The energy-limiting grid, formed by Rlim (current limiting), F1 (fuse), and Zener pair (anti-parallel clamp), ensures that the maximum open-circuit voltage, short-circuit current, and energy of this domain are limited. The sensing signal is sampled by the instrumentation amplifier and a high-precision ADC, and then sent to the controller domain through the digital isolator. The sensor ground is physically isolated from the high-voltage ground, and signals are transmitted only through isolation devices.

[0045] Please combine Figure 1 and Figure 2 And see Figure 4 As shown, Figure 4 This is a schematic diagram of the three states of the protection device for flammable refrigerant provided in this application embodiment. The protection device 100 includes three states: S0 normal monitoring, S1 early warning and fan, and S2 safety latch, which is also known as double cut-off and discharge. This is also the operation of the control domain. The controller MCU is used to generate different control signals according to the concentration of flammable refrigerant: when %LFL is greater than or equal to the first threshold and lasts for t1, it enters S1 from S0; when %LFL is greater than or equal to the second threshold or self-test fails, it enters S2 and latches. Reset requires the simultaneous satisfaction of four conditions: %LFL < HYS, Vbus < 60V, quiet time reached and manual reset triggered, before it can return from S2 to S0. Here, HYS refers to hysteresis, and recovery from early warning / latch is only allowed when it falls below HYS. Here, Vbus is the bus voltage.

[0046] Please combine Figure 1 and Figure 2 And see Figure 5 As shown, Figure 5 This is a block diagram of the execution domain in the flammable refrigerant protection device provided in this application embodiment. The execution domain includes a SELV sparkless fan drive channel for early warning and two channels for safety cut-off and energy discharge. When the first threshold is triggered, the controller MCU opens the fan 120 channel through drive isolation to achieve 25kHz open-drain PWM speed regulation. When the second threshold is triggered, the first relay SSR (i.e., zero-crossing solid-state relay) and the second relay K1 are controlled to achieve double cut-off on the AC side, while the discharge branch is turned on, reducing the bus voltage Vbus to below 60V within, for example, 2 seconds. Both drive commands are isolated across the domain, with RC absorption and discharge resistors connected in parallel on the load side, and a varistor connected in parallel at the inlet to suppress surges.

[0047] The above is an overall overview of the sensing domain, control domain, and execution domain. The following will describe the circuit components of each part.

[0048] For example, the protection device 100 in this application embodiment is equipped with an intrinsically safe power supply. Intrinsically safe is a design principle that ensures no ignition energy is generated by limiting voltage, current or energy.

[0049] For example, please refer to Figures 1 to 5 And see Figure 6 As shown, Figure 6 The circuit diagram of the intrinsically safe limited power supply in the flammable refrigerant protection device provided in the embodiments of this application is shown. The protection device 100 also includes an isolation converter U1. The two input terminals of the isolation converter U1 are connected to a first power supply, and the two output terminals of the isolation converter U1 are connected to a sensor 110. The isolation converter U1 is used to isolate and step down the first power supply and output it to the sensor 110, and to supply power to the sensor 110.

[0050] In other words, the sensing domain uses an isolated DC / DC converter, where the primary and secondary isolation withstand voltages are greater than or equal to 2.5kVrms, and the secondary output is 3.3V / 5V (SELV). An energy-limiting grid is placed between the secondary and the load.

[0051] The isolation converter U1, also known as an isolated DC-DC converter, isolates the motherboard's SELV power supply (typically 5V) to +3V_SENSE / GND_SENSE, with a primary / secondary isolation withstand voltage greater than or equal to 2.5kVrms. After isolation, SENSE is electrically separated from the high-voltage / motherboard ground, preventing fault energy from crossing the voltage range. The output capability of the isolation converter U1 is 3.3V, 300mA, 1W, but the subsequent energy-limiting gate strictly limits the usable current to the mA level. The isolation converter U1 has a first input terminal -Vin, a second input terminal +Vin, a first output terminal -Vout, and a second output terminal +Vout.

[0052] The first input terminal -Vin and the second input terminal +Vin are connected to the two input ports of the motherboard, namely the GND terminal and the Vin terminal, respectively. The protection device 100 also includes a first capacitor C1 and a fourth capacitor C4, both connected in parallel between the first input terminal -Vin and the second input terminal +Vin. The first capacitor C1 and the fourth capacitor C4 are used to decouple the primary input of the isolation converter U1. For example, the first capacitor C1 can be 0.1 microfarads and the fourth capacitor C4 can be 10 microfarads. The fourth capacitor C4 handles low-frequency or startup ripple, and the first capacitor C1 suppresses high-frequency spikes. Connected in parallel between the Vin and GND inputs of the motherboard, they reduce the switching stress of the isolation converter U1 and the backlash to the motherboard.

[0053] The protection device 100 also includes a first resistor R1, a reset fuse F1, a Zener pair D2, a second capacitor C2, and a third capacitor C3. The first output terminal -Vout is connected to the intrinsically safe output terminal, i.e., +3.3V_SENSE, and the second output terminal +Vout is connected to the intrinsically safe output terminal, i.e., GND_SENSE. Specifically, the first resistor R1, the reset fuse F1, and the Zener pair D2 are connected in series between the second output terminal +Vout and the intrinsically safe output terminal GND_SENSE, and the second capacitor C2 and the third capacitor C3 are connected in parallel between the intrinsically safe output terminal +3.3V_SENSE and GND_SENSE.

[0054] In this circuit, the first resistor R1 is a current-limiting resistor, such as 3.3 kΩ. The function of the first resistor R1 is to ensure that all load current in the secondary circuit passes through it. In the event of any short circuit or fault, the current can be limited to 1 mA, with an instantaneous power consumption of 3.3 mW, which is extremely low. If a larger available current is required in the subsequent stage, the first resistor R1 can be selected in the range of 2.2 kΩ to 4.7 kΩ, and the current and energy limits should be evaluated accordingly.

[0055] The reset fuse F1 serves as backup protection. It will only self-recover and disconnect in the 50-100mA range when the first resistor R1 fails and short-circuits, or when the isolation converter U1 abnormally raises its output, further cutting off energy. It should be noted that since the first resistor R1 already limits the current to 1mA, the reset fuse F1 will not trip under normal short-circuit conditions. Therefore, the reset fuse F1 can be considered a fallback device in case the first resistor R1 fails.

[0056] Zener diodes, also known as bidirectional TVS diodes, are transient voltage suppressor diodes used for surge / ESD protection at gate, bus, or signal ports. Two Zener diodes or one bidirectional TVS are connected in anti-parallel, connected between +3.3V_SENSE and GND_SENSE. Normally, they do not conduct. When a secondary winding experiences an induced spike, is incorrectly reversed, or experiences a transient, the output is clamped to a few volts, dissipating excess energy within itself and the first resistor R1, preventing external discharge.

[0057] The second capacitor C2 and the third capacitor C3 are used for intrinsically safe decoupling or energy storage on the secondary side. The second capacitor C2 and the third capacitor C3 are connected in parallel with the Zener pair D2 at +3.3V_SENSE and GND_SENSE. The second capacitor C2 can be 0.1 microfarads, and the third capacitor C3 can be 1 microfarad. The second capacitor C2 handles high-frequency bypass, while the third capacitor C3 provides low-frequency micro-energy storage and reduces measurement link ripple. The energy calculation E = ½·(C2+C3)·V²≈ ½·1.1µF·3.3²≈ 6 µJ, far below the ignition energy level.

[0058] For example, please refer to Figures 1 to 5And see Figure 7 As shown, Figure 7 The circuit diagram for sensor isolation in the protection device for flammable refrigerants provided in this application embodiment is shown. The first isolation unit 130 includes a sampling unit, a first isolation chip U3, a self-test unit, a protection unit, a second isolation chip U5, and a first switch Q1.

[0059] It should be noted that, taking sensor 110 as a gas-sensitive sensor as an example, a sensor holder is provided for easy connection. The sensor holder has four interfaces: A, B, H+, and H-. Interface A is connected to 3.3V_SENSE to power the upper end of the gas-sensitive resistor. Interface B is connected to VSIG, which is the sampling point and the voltage divider node between the gas-sensitive resistor and the second resistor R2. Interface H+ is the positive terminal of the heating wire, connected to the SELV power supply. Interface H- is the negative terminal of the heating wire, pulled to ground by the first switching element Q1 to achieve PWM heating.

[0060] One input terminal of the sampling unit is connected to the sensor 110 through the voltage divider node VSIG. The sampling unit is used to generate sampling data based on the sensor 110.

[0061] For example, the sampling unit includes a second resistor R2, a fifth capacitor C5, a third resistor R3, and a sampling chip U2.

[0062] One end of the second resistor R2 is connected to interface B of the sensor mount via a voltage divider node VSIG, and the other end of the second resistor R2 is grounded to GND_SENSE. The second resistor R2 and the gas-sensitive resistor form a voltage divider, providing bias and setting the sensitivity.

[0063] One end of the fifth capacitor C5 is connected to the voltage divider node VSIG, and the other end of the fifth capacitor C5 is grounded to GND_SENSE. The fifth capacitor C5, together with the second resistor R2 connected in parallel and the gas-sensitive resistor, form a low-pass filter to filter out noise and PWM interference.

[0064] One end of the third resistor R3 is connected to the voltage divider node VSIG, and the other end is connected to the sampling chip U2. The third resistor R3 is a current-limiting damper, which, together with the protection unit, prevents surges from impacting the ADC.

[0065] Both the ADDR and GND pins of sampling chip U2 are grounded to GND_SENSE. The ADDR pin of sampling chip U2 is used to set the slave address of the ADC chip. The ALERT / RDY pin of sampling chip U2 is left floating. The ALERT / RDY pin is a multi-function pin, mainly used to indicate conversion completion or comparator trigger status. The AIN0 pin of sampling chip U2 is connected to the third resistor R3. The AIN0 pin is an analog input pin. The AIN1, AIN2, and AIN3 pins of sampling chip U2 are all left floating. The AIN1, AIN2, and AIN3 pins are all analog input pins. The VDD pin of sampling chip U2 is the positive power supply pin and is connected to the +3.3V_SENSE power supply. The SCL and SDA pins of sampling chip U2 are both connected to the first isolation chip U3. The SCL pin is the serial clock pin, and the SDA pin is a bidirectional serial data line pin.

[0066] Among them, sampling chip U2 is used to convert the voltage divider voltage at voltage divider node VSIG into a digital quantity, VDD=+3.3V_SENSE, I 2 C follows SCL_S / SDA_S.

[0067] One input terminal of the first isolation chip U3 is connected to one output terminal of the sampling unit, and the output terminal of the first isolation chip U3 is connected to the controller MCU. The first isolation chip U3 is used to isolate and transmit the sampled data to the controller MCU.

[0068] For example, the VDD1 pin of the first isolation chip U3 is connected to the +3.3V_SENSE power supply, and the VDD2 pin of the first isolation chip U3 is connected to the +3.3V_LOGIC power supply, where both VDD1 and VDD2 pins are positive power supply pins. The GND1 pin of the first isolation chip U3 is grounded to GND_SENSE, and the GND2 pin of the first isolation chip U3 is grounded to GND_LOGIC. The SDA1 pin of the first isolation chip U3 is connected to the SDA pin of the sampling chip U2, and the SCL1 pin of the first isolation chip U3 is connected to the SCL pin of the sampling chip U2. The SDA2 pin and SCL2 pin of the first isolation chip U3 are connected to SDA_M and SCL_M, respectively.

[0069] The first isolation chip U3 is I 2 The C isolator isolates the SCL_S / SDA_S on the sensor side to the SCL_M / SDA_M on the controller MCU side. Both sides are pulled up to 3.3V and not connected to ground.

[0070] One end of the protection unit is connected to the sensor ground terminal GND_SENSE, and the other end is connected to the sensor power supply terminal +3.3V_SENSE. The controlled end of the protection unit is connected to the voltage divider node VSIG. The protection unit is used to clamp the voltage of the voltage divider node VSIG between the power rails for protection.

[0071] For example, the protection unit includes dual diodes D3, which clamp the voltage of the voltage divider node VSIG between GND_SENSE and +3.3V_SENSE, providing overvoltage and ESD protection, with low leakage current and low junction capacitance.

[0072] The MOS gas-sensitive resistor of sensor 110 and the second resistor R2 form a voltage divider to obtain the voltage of the voltage divider node VSIG. The voltage of the voltage divider node VSIG is first filtered by RC (i.e., the third resistor R3 and the fifth capacitor C5), and protected by dual diodes D3 clamped between the power rails. Then it is sent to the sampling chip U2 for sampling. The sampled data is transmitted through the first isolation chip U3 to the SENSE side I 2 C is isolated to the controller MCU side.

[0073] The output of the self-test unit is connected to the voltage divider node VSIG. The self-test unit is used to inject a microcurrent into the voltage divider node VSIG to form an equivalent flammable refrigerant concentration.

[0074] For example, the self-test unit includes a self-test chip U4 and a fourth resistor R4. The A0 pin of the self-test chip U4 is grounded to GND_SENSE and connected to the VSS pin of the self-test chip U4. The A0 pin is one of the address input pins used to set the device address, and the VSS pin is a ground pin, providing a reference potential for the circuit and ensuring the stability of signal transmission. The SCL and SDA pins of the self-test chip U4 are connected to SCL_S and SDA_S, respectively. The VDD pin of the self-test chip U4 is connected to the +3.3V_SENSE power supply. The VOUT pin of the self-test chip U4 is connected to one end of the fourth resistor R4, and the other end of the fourth resistor R4 is connected to the voltage divider node VSIG.

[0075] The self-test chip U4 is used for self-testing. Its VOUT pin, which is also the output pin, injects a microamp-level current into the voltage divider node VSIG through the fourth resistor R4 to simulate the equivalent concentration. The fourth resistor R4 is a high-impedance DAC injector, which converts the DAC voltage into a small current of 0 to 2 microamps injected into the voltage divider node VSIG to avoid disturbing the measurement.

[0076] The input terminal of the second isolation chip U5 is the controller MCU, used to receive control signals from the controller MCU. For example, the VDD1 and VDD2 pins of the second isolation chip U5 are connected to the +3.3V_LOGIC and +3.3V_SENSE power supplies, respectively, and the GND1 and GND2 pins are connected to GND_LOGIC and GND_SENSE, respectively. The VI pin of the second isolation chip U5 is connected to MCU_PWM to receive control signals from the controller MCU, and the VO pin of the second isolation chip U5 is connected to the fifth resistor R5.

[0077] The second isolation chip U5 is a single-channel digital isolation chip that isolates the MCU_PWM to the SENSE side and outputs VO to drive the controlled terminal of the first switching device Q1. The fifth resistor R5 is the gate series resistance of the first switching device Q1, which limits the gate charging and discharging current and suppresses rectification.

[0078] One end of the first switch Q1 is connected to the heating wire of the sensor 110, and the other end of the first switch Q1 is grounded to GND_SENSE. The controlled terminal of the first switch Q1 is connected to the second isolation chip U5 through the fifth resistor R5. The first switch Q1 is used to close under the control signal transmitted by the second isolation chip U5, so that the sensor 110 can operate. For example, the first switch Q1 can be a MOSFET, with one end, the other end, and the controlled terminal of the first switch Q1 corresponding to the drain, source, and gate of the MOSFET, respectively. The first switch Q1 is a low-side switch, controlling the on / off state of the H-interface of the sensor base to ground to realize heating PWM. The D / S is connected between the H-interface of the sensor base and GND_SENSE.

[0079] For example, please refer to Figures 1 to 5 And see Figure 8 As shown, Figure 8 The circuit diagram for the AC side double cutoff in the flammable refrigerant protection device provided in the embodiments of this application is shown. The second isolation unit 140 includes a third isolation chip U9. The first and second input terminals of the third isolation chip U9 are both connected to the controller MCU, and the output terminal of the third isolation chip U9 is connected to the first relay SSR and the second relay K1.

[0080] It should be noted that for AC-side double disconnection, the neutral and live wires of the mains power first pass through EMI filtering and varistor suppression for surge and conducted interference. The live wire passes sequentially through the neutral crossing solid-state relay (i.e., the first relay SSR) and the upper half of the second relay K1, while the neutral wire is simultaneously disconnected by the lower half of the second relay K1, thus forming a double disconnection.

[0081] When the second threshold is triggered, the controller MCU first turns off the first relay SSR through the third isolation chip U9. It will disconnect without arcing at the next zero crossing point, and then release the coil of the second relay K1. The mechanical contacts disconnect when there is almost no current, without arcing. If one device fails, the other device can still disconnect, forming redundancy.

[0082] For example, the second isolation unit 140 also includes an AC socket, a sixth resistor R6, a common mode choke L1, a relay chip U7, a seventh resistor R7, a second switch Q2, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a relay switch QK, and a freewheeling diode D4.

[0083] AC sockets are used for AC power input and have L, PE and N interfaces.

[0084] The sixth resistor, R6, is a varistor connected between the live wire L and the neutral wire N to absorb lightning strikes or surges during plugging and unplugging.

[0085] The two input terminals of the common-mode choke L1 are connected to the live wire L and the neutral wire N to suppress conducted noise between lines or between ground.

[0086] The first disconnection, i.e., the OUT_T1 and OUT_T2 interfaces of the relay chip U7 of the first relay SSR, are connected in series on the live wire L, after EMI, and then to the second relay K1. The IN+ interface of the relay chip U7 is supplied with +5V by the seventh resistor R7, and the IN- interface of the relay chip U7 is pulled down by the second switch Q2.

[0087] The second switch Q2 can be a MOSFET. Q2 acts as a low-side switch. Its drain is connected to the IN- interface of relay chip U7, its source is grounded, and its gate is controlled by the output of the third isolation chip U9 via the eighth resistor R8. The ninth resistor R9 pulls down the gate of Q2 by default, turning it off.

[0088] The second disconnection is also the second relay K1, and the contact connection is also a double-pole simultaneous disconnection: the live wire L path, the upper half of the middle pin comes from the output of the relay chip U7, and the upper half of the upper pin is connected to the AC_L_OUT of the second relay K1; the neutral wire L path, the lower half of the middle pin comes from the EMI, and the lower half of the upper pin is connected to the AC_N_OUT of the second relay K1; the coil pin1 of the second relay K1 is connected to the +24V power supply, and the coil pin2 of the second relay K1 is connected to the drain of the relay switch QK.

[0089] The relay switch QK can be a MOSFET. Relay switch QK is the low-side MOSFET of the second relay K1 coil. The source of relay switch QK is grounded, and the gate of relay switch QK is controlled by the output of the third isolation chip U9 via the eleventh resistor R11. The tenth resistor R10 is connected in parallel between the gate and source of relay switch QK, and the tenth resistor R10 is pulled down by default to turn off.

[0090] The freewheeling diode D4 is the freewheeling diode across the coil of the second relay K1. The K terminal of the freewheeling diode D4 is connected to the +24V power supply, and the A terminal of the freewheeling diode D4 is connected to the drain of the relay switch QK. The freewheeling diode D4 is used to absorb the de-energizing spike of the coil of the second relay K1, thereby protecting the relay switch QK.

[0091] The third isolation chip U9 is a dual-channel in-direction isolation chip. Its VDD1 and GND1 pins are connected to +3.3V_LOGIC and GND_LOGIC respectively, which is the MCU side of the controller. A 0.1µF capacitor is connected between VDD1 and GND1. Its VDD2 and GND2 pins are connected to +5V and GND respectively, which is the execution side. Two 0.1µF capacitors are connected in parallel between VDD2 and GND2. Its VIA and VIB pins are the input pins on the MCU side, connected to MCU.SSR_CTRL and MCU.K_CTRL respectively. Its VOA and VOB pins are the output pins on the execution side, connected to the second switch Q2 via resistor R8 and to the relay switch QK via resistor R11.

[0092] Please combine Figures 1 to 5 And see Figure 9 As shown, Figure 9 The circuit diagram for the warning and sparkless fan in the flammable refrigerant protection device provided in this application embodiment is shown. For the warning and sparkless fan, the protection device 100 also includes a fan base H2, a voltage regulator chip U11, a sixth capacitor C6, a seventh capacitor C7, a third switch Q3, a fourth switch Q4, a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a transient suppression diode D5, a dual-channel digital isolation chip U15, a fifth switch Q5, and a seventeenth resistor R17.

[0093] The fan mount H2 is a four-wire fan mount. Pin 1 of the fan mount H2 is connected to Vin such as +5V, +12V, or +24VSELV. Pin 2 of the fan mount H2 is grounded to GND. Pin 3 of the fan mount H2 is connected to FG, which is the open-drain speed feedback. Pin 4 of the fan mount H2 is connected to the PWM signal, which is pulled up by an external 5V according to the specification, and the control terminal is pulled low by the open-drain signal.

[0094] The voltage regulator chip U11 provides a local 3.3V voltage regulator for use with local small logic or the isolated side. The GND pin of the voltage regulator chip U11 is connected to one end of the seventh capacitor C7, and the OUT pin is connected to one end of the sixteenth resistor R16, which is also connected to the other end of the seventh capacitor C7. The sixth capacitor C6 is connected between the VIN pin and the GND pin of the voltage regulator chip U11.

[0095] The sixth capacitor C6 is used for input decoupling of the voltage regulator chip U11, and the seventh capacitor C7 is used for output decoupling of the voltage regulator chip U11.

[0096] The third switch, Q3, can be a MOSFET. The source of Q3 is connected to the power supply VCC, and the drain is connected to the VIN pin of the fan base H2. The gate of Q3 is connected between the twelfth resistor R12 and the thirteenth resistor R13, with the other end of the thirteenth resistor R13 connected to the power supply VCC. Q3 is the high-side switch for fan power supply; it conducts when its gate is pulled low, supplying VCC to the fan.

[0097] The fourth switch, Q4, can also be a MOSFET. The drain of Q4 is connected to the twelfth resistor, R12, and the source is grounded. The gate of Q4 is connected to the input control MCU, MCU.Vin_CTRL, via the fourteenth resistor, R14. The gate and source of Q4 are connected via the fifteenth resistor, R15. Q4 is the gate driver of the third switch, Q3, and its low-side is pulled to ground.

[0098] Among them, the thirteenth resistor R13 pulls the gate of the third switch Q3 up to VCC, and is turned off by default when VGS=0. The twelfth resistor R12 is the gate series resistance of the third switch Q3, limiting instantaneous gate current and suppressing ringing. The fourteenth resistor R14 is the gate series resistance from the controller MCU to the fourth switch Q4. The fifteenth resistor R15 pulls down the gate of the fourth switch Q4, is turned off by default, and prevents power-on glitches.

[0099] One end of the transient voltage suppressor diode D5 is connected to the Vin pin of the fan base H2, and the other end is connected to the GND pin of the voltage regulator chip U11. The transient voltage suppressor diode D5 is used to absorb surges such as those caused by insertion / removal or motor flyback.

[0100] The PWM speed control, i.e., open-drain, is implemented through a dual-channel digital isolation chip U15. The VDD1 and GND1 pins of the U15 are connected to +3.3V_LOGIC and GND_LOGIC respectively, which are the power supply and ground on the MCU side of the controller. The VDD2 and GND2 pins are connected to +5V and GND on the fan side respectively, with 0.1µF capacitors on each side for decoupling. The VIB pin of the U15 is connected to MCU.PWM_CTRL, and the VOB pin is connected to the seventeenth resistor R17 on the fan side; this channel sends the PWM signal from the MCU side to the fan side. The VIA pin of the U15 is connected to the fan side's FG, and the VOA pin is connected to MCU.PWM_READ; this channel sends the FG signal back from the fan side to the MCU side.

[0101] The fifth switch, Q5, can be a MOSFET. The source of Q5 is grounded, and its drain is connected to the PWM pin of the fan base H2. The gate of Q5 is connected to the isolation output of the dual-channel digital isolation chip U15. The gate is pulled down by resistors R17 and R18, and is disabled by default, meaning the PWM is high. Resistor R17, acting as a series resistor from the PWM line to the input of the dual-channel digital isolation chip U15, is used to read the actual PWM signal back to the controller MCU, labeled MCU.PWM_READ, and simultaneously provides current limiting protection for the input of the dual-channel digital isolation chip U15.

[0102] The protection device 100 also includes a lamp LED2 and a 22nd resistor R22. One end of the lamp LED2 is connected to the Vin pin of the fan base H2, and the other end of the lamp LED2 is connected to one end of the 22nd resistor R22. The other end of the 22nd resistor R22 is grounded.

[0103] In general, the controller MCU sends the PWM control to the PWM pin of the fan 120 via the dual-channel digital isolation chip U15, with open-drain pull-down. Simultaneously, a P-channel high-side MOSFET (the third switch Q3) controlled by an N-channel MOSFET (the fourth switch Q4) supplies power to the fan's Vin pin. Transient voltage suppressor diode D5, along with capacitors C6 and C7, absorbs surges and ripple. LED2 is connected between the Vin pin and the PWM pin of the fan base H2, serving as a power supply or duty cycle indicator. The fan's FG speed signal returns to the controller MCU via the dual-channel digital isolation chip U15.

[0104] To reduce the risk of sparks generated by residual voltage, the protection device 100 of this application embodiment also has a DC bus discharge unit.

[0105] For example, please refer to Figures 1 to 5 And see Figure 10 As shown, Figure 10 The circuit diagram of the DC bus discharge in the flammable refrigerant protection device provided in this application embodiment is shown. The DC bus discharge unit includes a bus lead-out socket H3, a nineteenth resistor R19, a sixth switch Q6, a twentieth resistor R20, a twenty-first resistor R21, an eighth capacitor C8, and a single-channel digital isolation chip U17.

[0106] Pin 1 of busbar lead-out connector H3, also known as DC_BUS+, is connected to one end of the nineteenth resistor R19. Pin 2 of busbar lead-out connector H3, also known as DC_BUS-, is connected to the GND2 pin of the single-channel digital isolation chip U17, which is also the execution domain ground.

[0107] The nineteenth resistor, R19, is a bleeder resistor, limiting the discharge current and power consumption. The initial current I0 = Vbus / R19, for example, 325V / 3.3kΩ ≈ 0.10A; the initial power consumption P0 = Vbus 2 / R19≈32W, then decays exponentially. In practice, multiple high-voltage resistors can be connected in series or in parallel to achieve pulse tolerance.

[0108] The sixth switch, Q6, can be a MOSFET. The drain of Q6 is connected to the nineteenth resistor, R19, and the source is connected to the DC_BUS- pin of bus H3. The gate of Q6 is driven by a single-channel digital isolation chip, U17, ensuring reliable conduction under a current in the range of 0.1A. A back-to-back Zener diode is positioned between the gate and source of Q6 to limit the absolute value of Vgs, preventing overshoot of the gate-source voltage due to drive current or surges.

[0109] The twenty-first resistor R21 is connected to the gate and source of the sixth switch Q6 respectively. The twenty-first resistor R21 pulls down the gate and source of the sixth switch Q6. When it is turned off, it pulls the gate back to the source to avoid floating and misleading turn-on.

[0110] One end of the twentieth resistor R20 is connected to the gate of the sixth switch Q6, and the other end is connected to the single-channel digital isolation chip U17. The twentieth resistor R20 is a gate series resistor, used to limit the gate charging and discharging current, suppress ringing, and reduce the peak load of the single-channel digital isolation chip U17.

[0111] The eighth capacitor C8 is used to decouple the VDD2 pin of the single-channel digital isolation chip U17. The two ends of the eighth capacitor C8 are connected between the VDD2 pin and the GND2 pin of the single-channel digital isolation chip U17, respectively. That is to say, the eighth capacitor C8 is connected to the power supply and ground on the execution side to filter out the drive spikes.

[0112] The single-channel digital isolation chip U17 is used to transmit the MCU.DC_CTRL signal across isolation to the execution side. The VDD1 and GND1 pins of the single-channel digital isolation chip U17 are connected to +3.3V_LOGIC and GND_LOGIC, respectively, which is the MCU side of the controller. The VI pin of the single-channel digital isolation chip U17 is connected to MCU.DC_CTRL. The VDD2 and GND2 pins of the single-channel digital isolation chip U17 are connected to the +12V power supply and DC_BUS-, respectively, which is the execution side power supply. The VO pin of the single-channel digital isolation chip U17 is connected to the gate of the sixth switch Q6 through the twentieth resistor R20. The eighth capacitor C8 on the execution side is decoupled locally.

[0113] The protection device 100 provided in this application embodiment, through the design of the circuit surrounding the sensor 110, can achieve energy safety on the sensing side, that is, under any single-point fault, ensure that the voltage, current, and releaseable energy of the sensing domain are all below the ignition threshold; it can also achieve graded action and sparkless execution, realizing early warning dilution of the first threshold, and sparkless and redundant disconnection of the AC side when the second threshold is safely latched. It can also achieve the effect of quickly eliminating residual energy, rapidly and safely reducing the DC bus energy to a safe voltage after disconnection. It can also achieve the effect of link reliability and verifiability, stably measuring and self-checking online under noise and surge environments, and providing quantifiable reset conditions. Furthermore, it has system isolation and compatibility, limiting fault propagation through three-domain isolation, while being compatible with 4-wire fan specifications, such as external 5V pull-up and open-drain pull-down.

[0114] To more clearly illustrate the operation of the protection device 100 in this application embodiment, this application embodiment also provides a method for protecting flammable refrigerants, including: Detect the concentration of leaked flammable refrigerant in the air surrounding pipelines containing flammable refrigerant; If the concentration of flammable refrigerant reaches the first threshold, the fan will be activated to blow the leaked flammable refrigerant to the outside of the refrigerator. If the concentration of flammable refrigerant reaches the second threshold, the first and second relays are turned off in sequence to disconnect both the live and neutral wires of the mains power. The second threshold is greater than the first threshold.

[0115] It should be noted that, in order to reduce the risk of combustion of flammable refrigerant, the embodiments of this application take different measures depending on the concentration of the leaked flammable refrigerant. For example, when the concentration of flammable refrigerant is normal, a fan is driven to dilute the flammable refrigerant inside the refrigerator to reduce the concentration of flammable refrigerant and thus reduce the risk of combustion. When the concentration of flammable refrigerant is high, in order to reduce the generation of sparks from ignition sources, the power to the equipment is cut off, and both the neutral and live wires of the mains power are disconnected, thereby doubly ensuring the safety of the equipment.

[0116] In the protection method for flammable refrigerants provided in this application embodiment, by setting up a sensor to detect the concentration of flammable refrigerant, it is possible to detect flammable refrigerant leakage in a timely manner and take corresponding actions based on the leakage concentration of flammable refrigerant, thereby protecting equipment that uses flammable refrigerants and improving the safety of the equipment.

[0117] This application also provides a refrigerator that includes the aforementioned flammable refrigerant protection device. The flammable refrigerant protection device can be referred to the above description and will not be repeated here. Since this refrigerator adopts all the technical solutions of all the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated upon here.

[0118] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0119] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more features.

[0120] The above provides a detailed description of the protection device, protection method, and refrigerator for flammable refrigerants provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A protective device for flammable refrigerant, applied to a refrigerator, characterized in that, include: Sensors are used to detect the concentration of leaked flammable refrigerant in the air around pipes containing flammable refrigerant. A fan is used to blow leaked flammable refrigerant to the outside of the refrigerator; The first relay and the second relay are connected in series with the upper half of the first relay and the upper half of the second relay, and the neutral wire of the mains power is connected to the lower half of the second relay. The controller is electrically connected to the sensor, the fan, the first relay, and the second relay respectively. The controller is used to drive the fan to work when the concentration of the combustible refrigerant reaches a first threshold, and to first turn off the first relay to disconnect the live wire when the concentration of the combustible refrigerant reaches a second threshold, and then turn off the second relay to disconnect the neutral wire. The first threshold is less than the second threshold.

2. The protection device according to claim 1, characterized in that, The protective device also includes: The first isolation unit is connected between the sensor and the controller; The second isolation unit is connected between the controller and the first relay and the second relay.

3. The protection device according to claim 2, characterized in that, The first isolation unit includes: A sampling unit, one of whose input terminals is connected to the sensor via a voltage divider node, is used to generate sampling data based on the sensor. A first isolation chip has its input terminal connected to an output terminal of the sampling unit and its output terminal connected to the controller. The first isolation chip is used to isolate and transmit the sampled data to the controller.

4. The protection device according to claim 3, characterized in that, The first isolation unit further includes: The self-test unit has its output connected to the voltage divider node. The self-test unit is used to inject a microcurrent into the voltage divider node to form an equivalent flammable refrigerant concentration.

5. The protection device according to claim 3, characterized in that, The first isolation unit further includes: The protection unit has one end connected to the sensor ground terminal and the other end connected to the sensor power supply terminal. Its controlled terminal is connected to the voltage divider node. The protection unit is used to protect the voltage of the voltage divider node by clamping it between the power rails.

6. The protection device according to claim 2, characterized in that, The first isolation unit further includes: The second isolation chip has its input terminal connected to the controller to receive control signals from the controller; A first switching element has one end connected to the heating wire of the sensor, the other end grounded, and its controlled end connected to the second isolation chip. The first switching element is used to close under the control signal transmitted by the second isolation chip, so as to enable the sensor to operate.

7. The protection device according to claim 2, characterized in that, The second isolation unit includes: The third isolation chip has its first and second input terminals both connected to the controller, and its output terminal connected to the first and second relays.

8. The protection device according to claim 1, characterized in that, The protective device also includes: An isolation converter has two input terminals connected to a first power supply and two output terminals connected to the sensor. The isolation converter is used to isolate and step down the first power supply before outputting it to the sensor and powering the sensor.

9. A method for protecting a flammable refrigerant, characterized in that, include: Detect the concentration of leaked flammable refrigerant in the air surrounding pipelines containing flammable refrigerant; If the concentration of the flammable refrigerant reaches the first threshold, the fan is driven to run in order to blow the leaked flammable refrigerant to the outside of the refrigerator. If the concentration of the flammable refrigerant reaches the second threshold, the first relay and the second relay are turned off in sequence to disconnect both the live wire and the neutral wire of the mains power. The second threshold is greater than the first threshold.

10. A refrigerator, characterized in that, Includes a protective device for flammable refrigerants as described in any one of claims 1 to 8.

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