Under-voltage alarm circuit of refrigerator and refrigerator

Abstract

The utility model discloses an under-voltage alarm circuit of a refrigerator and the refrigerator, the under-voltage alarm circuit comprises a voltage detection circuit which comprises a first voltage stabilizing diode, a second voltage stabilizing diode and a first switch circuit; the cathode of the first voltage stabilizing diode is connected with the positive output end of the filtering and rectifying circuit; the anode of the first voltage-stabilizing diode is connected with the cathode of the second voltage-stabilizing diode through the first current-limiting resistor, the anode of the second voltage-stabilizing diode is grounded, the cathode of the second voltage-stabilizing diode is connected with the control end of the first switching circuit, and one end of a switching path of the first switching circuit is connected with the direct-current power supply through the pull-up resistor. The other end of the switch path of the first switch circuit is grounded; the alarm circuit comprises a second switch circuit and an alarm; the control end of the second switching circuit is connected with one end of the switching path of the first switching circuit, and the switching path of the second switching circuit is connected in series in the power supply loop of the alarm. The device can give an alarm prompt in time when the mains supply is under-voltage so as to inform a user in time.

Description

Technical Field

[0001] The utility model relates to the technical field of circuits, in particular to an undervoltage alarm circuit of a refrigerator and a refrigerator. Background Art

[0002] Refrigerators on the market today all have a nominal rated voltage. When designing a refrigerator, the power supply must be designed accordingly based on the nominal rated voltage to ensure that the refrigerator will not malfunction due to voltage fluctuations within a certain input voltage range.

[0003] If the power grid loses power, that is, there is a power outage, users will sense it in time and choose to take appropriate measures for the items stored in the refrigerator as needed.

[0004] If the grid is not powered off, but the grid voltage remains below the lower limit of the design voltage range, the refrigerator will cut off the power for protection and stop working. However, the user will be unaware of this and will not handle the items stored in the refrigerator, which may cause the items in the refrigerator to deteriorate and become corrupt.

[0005] Therefore, current refrigerators fail to promptly notify users when the power grid is undervoltage, causing food in the user's refrigerator to spoil, thereby reducing the user's experience. Summary of the invention

[0006] The utility model provides an undervoltage alarm circuit for a refrigerator, which solves the technical problem in the prior art that a prompt cannot be issued in time when the mains voltage is undervoltage.

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

[0008] The utility model provides an undervoltage alarm circuit for a refrigerator, the refrigerator comprising a power supply circuit, the power supply circuit comprising a filter rectifier circuit; the undervoltage alarm circuit comprises:

[0009] A voltage detection circuit, comprising a first voltage-stabilizing diode, a second voltage-stabilizing diode, and a first switch circuit; the cathode of the first voltage-stabilizing diode is connected to the positive output end of the filter rectifier circuit; the anode of the first voltage-stabilizing diode is connected to the cathode of the second voltage-stabilizing diode via a first current-limiting resistor, the anode of the second voltage-stabilizing diode is grounded, the cathode of the second voltage-stabilizing diode is connected to the control end of the first switch circuit, one end of the switch path of the first switch circuit is connected to a DC power supply via a pull-up resistor, and the other end of the switch path of the first switch circuit is grounded; an alarm circuit, comprising a second switch circuit and an alarm; the control end of the second switch circuit is connected to one end of the switch path of the first switch circuit, and the switch path of the second switch circuit is connected in series in the power supply circuit of the alarm.

[0010] In some embodiments of the present application, the first switch circuit includes a first switch tube;

[0011] The control end of the first switch tube is connected to the cathode of the second voltage stabilizing diode;

[0012] One end of the switch path of the first switch tube is connected to a DC power supply through the pull-up resistor;

[0013] The other end of the switch path of the first switch tube is grounded.

[0014] In some embodiments of the present application, the second switch circuit includes a second switch tube;

[0015] The control end of the second switch tube is connected to one end of the switch path of the first switch tube;

[0016] One end of the switch path of the second switch tube is connected to a DC power supply via a second current limiting resistor;

[0017] The other end of the switch path of the second switch tube is connected to the positive power supply end of the alarm; the negative power supply end of the alarm is grounded.

[0018] In some embodiments of the present application, one end of the first current limiting resistor is connected to the anode of the first voltage zener diode;

[0019] The other end of the first current limiting resistor is grounded via a first electrolytic capacitor;

[0020] The other end of the first current limiting resistor is connected to the cathode of the second voltage stabilizing diode through a third current limiting resistor.

[0021] In some embodiments of the present application, the alarm includes a buzzer and / or an indicator light.

[0022] Refrigerator, including:

[0023] The undervoltage alarm circuit;

[0024] The power supply circuit comprises a filter and rectifier circuit and a voltage conversion circuit; the positive output end of the filter and rectifier circuit is respectively connected to the undervoltage alarm circuit and the voltage conversion circuit; the negative output end of the filter and rectifier circuit is grounded.

[0025] In some embodiments of the present application, the voltage conversion circuit includes a switching power supply chip, a transformer, a DC filter circuit, and a DC output terminal;

[0026] The opposite-name end of the first primary winding of the transformer is connected to the positive output end of the filter and rectifier circuit;

[0027] The same-name end of the first primary winding is connected to the drain pin of the switching power supply chip;

[0028] The source pin of the switching power supply chip is grounded;

[0029] The control pin of the switching power supply chip is connected to the output end of the light receiving end of the optocoupler; the input end of the light receiving end of the optocoupler is connected to the same-name end of the second primary winding of the transformer; the opposite-name end of the second primary winding is grounded;

[0030] The input end of the light-emitting end of the optocoupler is connected to the same-name end of the secondary winding of the transformer, the output end of the light-emitting end of the optocoupler is connected to the cathode of a three-terminal voltage regulator, the anode of the three-terminal voltage regulator is grounded, and the reference level of the three-terminal voltage regulator is connected to the DC output end through a voltage divider circuit; the same-name end of the secondary winding is connected to the DC output end through the DC filter circuit; the opposite-name end of the secondary winding is grounded.

[0031] In some embodiments of the present application, the drain pin of the switching power supply chip is connected to the anode of the first diode, the cathode of the first diode is connected to one end of the RC parallel circuit, and the other end of the RC parallel circuit is connected to the positive output end of the filter rectifier circuit.

[0032] In some embodiments of the present application, the same-name end of the second primary winding is connected to the anode of the second diode, and the cathode of the second diode is connected to the input end of the light-receiving end of the optical coupler;

[0033] The cathode of the second diode is grounded through a parallel circuit of an electrolytic capacitor and a resistor.

[0034] The DC filter circuit includes a third diode, an inductor, a second electrolytic capacitor, a third electrolytic capacitor, a first filter capacitor, and a second filter capacitor;

[0035] The same-name end of the secondary winding is connected to the anode of the third diode, the cathode of the third diode is connected to one end of the inductor, and the other end of the inductor is connected to the DC output end;

[0036] The positive electrode of the second electrolytic capacitor is connected to one end of the inductor, and the negative electrode of the second electrolytic capacitor is grounded; the first filter capacitor is connected in parallel to both ends of the second electrolytic capacitor;

[0037] The positive electrode of the third electrolytic capacitor is connected to the other end of the inductor, and the negative electrode of the third electrolytic capacitor is grounded; the second filter capacitor is connected in parallel to both ends of the third electrolytic capacitor.

[0038] The technical solution of the utility model has the following technical effects compared with the prior art: the undervoltage alarm circuit of the refrigerator and the refrigerator of the utility model detect the output voltage of the filter rectifier circuit by designing a voltage detection circuit. When it is detected that the output voltage of the filter rectifier circuit is lower than the set threshold, the first switch circuit is turned off, the second switch circuit is turned on, the power supply circuit of the alarm is turned on, and the alarm sounds to remind the user; by designing a first voltage stabilizing diode in the voltage detection circuit, it plays the role of voltage stabilization and voltage division, avoiding burning of the back-end circuit when the output voltage of the filter rectifier circuit is large; by designing a second voltage stabilizing diode, the voltage is clamped when its cathode voltage is large. The nominal voltage of the second voltage-stabilizing diode is set to protect the first switch circuit, avoiding excessive voltage from burning the first switch circuit, so as to protect the circuit safety; by controlling the on-off of the first switch circuit, the on-off of the second switch circuit is controlled, and then the on-off of the power supply circuit of the alarm is controlled, and the control is simple and convenient; therefore, the undervoltage alarm circuit of the refrigerator of the utility model can detect the undervoltage of the mains power, and promptly issue an alarm prompt when the mains power is undervoltage, so as to promptly notify the user of the undervoltage state of the refrigerator, which solves the technical problem in the prior art that the alarm prompt is not issued in time when the mains power is undervoltage, improves the user's experience, and improves the competitiveness of the refrigerator.

[0039] After reading the specific embodiments of the present invention in conjunction with the accompanying drawings, other features and advantages of the present invention will become more clear. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 This is a principle block diagram of an embodiment of the undervoltage alarm circuit of the refrigerator of the utility model;

[0042] Figure 2 This is the control schematic diagram of the undervoltage alarm circuit;

[0043] Figure 3 A circuit schematic diagram of an embodiment of an undervoltage alarm circuit;

[0044] Figure 4 A circuit schematic diagram of another embodiment of an undervoltage alarm circuit;

[0045] Figure 5 It is the connection principle block diagram of the filter rectifier circuit and the undervoltage alarm circuit;

[0046] Figure 6is a principle block diagram of an embodiment of a power supply circuit;

[0047] Figure 7 A principle block diagram of an embodiment of a filter and rectifier circuit;

[0048] Figure 8 is a principle block diagram of an embodiment of a voltage conversion circuit;

[0049] Fig. 9 It is a block diagram of the connection principle between the filter rectifier circuit and the voltage conversion circuit;

[0050] Fig.10 This is a block diagram of the connection principle between the power supply circuit and the undervoltage alarm circuit. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0052] In the description of the present application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0053] The terms "first", "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0054] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0055] In the present utility model, unless otherwise clearly stipulated and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0056] The disclosure below provides many different embodiments or examples for realizing different structures of the utility model. In order to simplify the disclosure of the utility model, the components and settings of specific examples are described below. Of course, they are merely examples, and the purpose is not to limit the utility model. In addition, the utility model may repeat reference numbers and / or reference letters in different examples, and such repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the utility model provides various specific examples of processes and materials, but those of ordinary skill in the art may be aware of the application of other processes and / or the use of other materials.

[0057] Embodiment 1

[0058] The undervoltage alarm circuit of the refrigerator of this embodiment includes a voltage detection circuit, an alarm circuit, etc. Figures 1 to 5 shown.

[0059] The refrigerator comprises a power supply circuit, and the power supply circuit comprises a filtering and rectifying circuit and a voltage conversion circuit.

[0060] The filter and rectifier circuit is used to filter and rectify the AC power and output DC power. The voltage conversion circuit is used to convert the DC power output by the filter and rectifier circuit into a voltage.

[0061] The filter rectifier circuit filters and rectifies the input AC power and outputs DC power. The filter rectifier circuit has a live terminal IN1, a neutral terminal IN2, a positive output terminal OUT1, and a negative output terminal OUT2. The live terminal IN1 is connected to the live wire, and the neutral terminal IN2 is connected to the neutral wire; the AC power (mains power) enters the filter rectifier circuit through the live terminal IN1 and the neutral terminal IN2, and the filter rectifier circuit filters and rectifies the AC power, and then outputs DC power through the positive output terminal OUT1 and the negative output terminal OUT2. Among them, the negative output terminal OUT2 of the filter rectifier circuit is grounded (AGND).

[0062] The voltage detection circuit includes a first voltage zener diode ZD1, a second voltage zener diode ZD2, and a first switch circuit; the cathode of the first voltage zener diode ZD1 is connected to the positive output terminal OUT1 of the filter rectifier circuit; the anode of the first voltage zener diode ZD1 is connected to the cathode of the second voltage zener diode ZD2 through a first current limiting resistor R4, the anode of the second voltage zener diode ZD2 is grounded (AGND), the cathode of the second voltage zener diode ZD2 is connected to the control terminal of the first switch circuit, one end of the switch path of the first switch circuit is connected to a DC power supply VDD through a pull-up resistor R7, and the other end of the switch path of the first switch circuit is grounded (AGND). One end of the switch path of the first switch circuit outputs an alarm signal to the alarm circuit.

[0063] The alarm circuit comprises a second switch circuit and an alarm; the control end of the second switch circuit is connected to one end of the switch path of the first switch circuit, and the switch path of the second switch circuit is connected in series in the power supply circuit of the alarm.

[0064] When the mains voltage is higher than the lower limit of the voltage range, the output voltage Ubr of the filter rectifier circuit is also greater than the set threshold value, the first voltage zener diode ZD1 and the second voltage zener diode ZD2 are reversely broken down, and the voltage value at Uc is the nominal voltage of the voltage zener diode ZD2. At this time, Uc is greater than the conduction voltage of the first switch circuit, the first switch circuit is turned on, and the current provided by the DC power supply VDD flows to the ground (AGND) through the pull-up resistor R7 and the switch path of the first switch circuit. At this time, the control end of the second switch circuit is low level, the second switch circuit is turned off, the power supply circuit of the alarm is disconnected, and the alarm does not work.

[0065] When the mains voltage is lower than the lower limit of the voltage range, the output voltage Ubr of the filter and rectifier circuit is also correspondingly smaller than the set threshold value, the first Zener diode ZD1 is reversely broken down, the second Zener diode ZD2 is not reversely broken down, and the voltage Uc at the cathode of the second Zener diode ZD2 is lower than the nominal voltage of the second Zener diode ZD2. At this time, Uc is smaller than the turn-on voltage of the first switch circuit, the first switch circuit is turned off, the control end of the second switch circuit is at a high level, the second switch circuit is turned on, the power supply circuit of the alarm is turned on, the alarm works, and an alarm is triggered to remind the user.

[0066] Therefore, when the mains voltage is lower than the lower limit of the voltage range, the output voltage Ubr of the filter rectifier circuit cannot reversely break down the second zener diode ZD2 after passing through the first zener diode ZD1 and the resistor R4. Since the current flowing through the first zener diode ZD1 is extremely small, the voltage value of the resistor R4 can be ignored. It can be obtained that Ubr-Uzd1-Uc≈0, then Uc≈Ubr-Uzd1. Uzd1 is the nominal stable voltage of the first zener diode ZD1, which is a fixed value. The nominal stable voltage of the second zener diode ZD2 is selected according to the lower limit of the designed input voltage range. From the above, it can be seen that when the mains voltage is lower than the lower limit of the voltage range, Uc will increase or decrease accordingly as the Ubr value increases or decreases.

[0067] Therefore, the voltage detection circuit is connected to the rear end of the filter and rectifier circuit to detect whether the output voltage Ubr of the filter and rectifier circuit is lower than a set threshold.

[0068] When the output voltage Ubr of the filter and rectifier circuit is higher than the set threshold, that is, when the AC voltage is higher than the lower limit of the voltage range, the first switch circuit is turned on and outputs an invalid alarm signal (low-level signal) to the control end of the second switch circuit. The second switch circuit is turned off, the alarm is powered off, and the alarm does not operate.

[0069] When the output voltage Ubr of the filter and rectifier circuit is lower than the set threshold, that is, when the AC voltage is lower than the lower limit of the voltage range, the first switch circuit is turned off and an effective alarm signal (high level signal) is output to the control end of the second switch circuit. The second switch circuit is turned on, the alarm is powered on, and the alarm sounds.

[0070] Therefore, when the voltage detected by the voltage detection circuit is lower than the set threshold, the voltage detection circuit outputs a valid alarm signal to the alarm circuit, and the alarm circuit performs an alarm operation.

[0071] In some embodiments of the present application, the alarm includes a buzzer and / or an indicator light. When the second switch circuit is turned on, the power supply circuit of the alarm is turned on, the buzzer sounds, and / or the indicator light turns on to remind the user.

[0072] The first voltage stabilizing diode ZD1 mainly plays the role of voltage stabilization and voltage division, and the second voltage stabilizing diode ZD2 plays the role of protecting the first switch circuit.

[0073] The undervoltage alarm circuit of the refrigerator of this embodiment detects the output voltage of the filter and rectifier circuit by designing a voltage detection circuit. When it is detected that the output voltage of the filter and rectifier circuit is lower than the set threshold, the first switch circuit is turned off, the second switch circuit is turned on, the power supply circuit of the alarm is turned on, and the alarm sounds to remind the user; by designing a first voltage stabilizing diode in the voltage detection circuit, it plays a role of voltage stabilization and voltage division, avoiding burning of the back-end circuit when the output voltage of the filter and rectifier circuit is large; by designing a second voltage stabilizing diode, the voltage is clamped to the nominal voltage of the second voltage stabilizing diode when its cathode voltage is large , which plays a role in protecting the first switch circuit, preventing the first switch circuit from being burned by excessive voltage, so as to protect the circuit safety; by controlling the on and off of the first switch circuit, the on and off of the second switch circuit is controlled, and then the on and off of the power supply circuit of the alarm is controlled, and the control is simple and convenient; therefore, the undervoltage alarm circuit of the refrigerator in this embodiment can detect the undervoltage of the mains power, and promptly issue an alarm prompt when the mains power is undervoltage, so as to promptly notify the user of the undervoltage state of the refrigerator, which solves the technical problem in the prior art that the alarm prompt cannot be issued in time when the mains power is undervoltage, improves the user's usage experience, and improves the competitiveness of the refrigerator.

[0074] The undervoltage alarm circuit of the refrigerator of this embodiment uses a voltage detection circuit to detect the AC power voltage. When it is detected that the AC power voltage is lower than the lower limit of the voltage range (undervoltage), that is, when it is detected that the output voltage of the filter rectifier circuit is lower than the set threshold, the drive buzzer sounds and / or the LED indicator light up to issue an alarm prompt.

[0075] The undervoltage alarm circuit of the refrigerator of this embodiment detects the mains voltage in real time. When the mains voltage is too low, an alarm action is immediately performed to remind the user, so as to avoid the situation that the refrigerator is automatically powered off due to undervoltage, the user is unaware of it, and fails to deal with the items stored in the refrigerator in time, resulting in the items being spoiled or deteriorated.

[0076] The undervoltage alarm circuit of this embodiment does not require an additional filter and rectifier circuit, and can be added to the rear end of the filter and rectifier circuit of the power circuit of the refrigerator.

[0077] The undervoltage alarm circuit of this embodiment does not require a backup power supply and can be integrated on a power supply board, thus saving space; at the same time, it does not require a backup power supply, thus avoiding the increase of additional costs.

[0078] In some embodiments of the present application, the first switch circuit includes a first switch tube N1, see Figure 3 shown.

[0079] The control end of the first switch tube N1 is connected to the cathode of the second voltage stabilizing diode ZD2; one end of the switch path of the first switch tube N1 is connected to the DC power supply VDD through the pull-up resistor R7; the other end of the switch path of the first switch tube N1 is grounded (AGND).

[0080] By designing the first switch tube N1, it is convenient to control the on and off of the first switch circuit, and the structure is simple and easy to control.

[0081] In some embodiments of the present application, the second switch circuit includes a second switch tube N2, see Figure 3 shown.

[0082] The control end of the second switch tube N2 is connected to one end of the switch path of the first switch tube N1; one end of the switch path of the second switch tube N2 is connected to the DC power supply VDD through the second current limiting resistor R9; the other end of the switch path of the second switch tube N2 is connected to the positive power supply end of the alarm; the negative power supply end of the alarm is grounded (AGND).

[0083] By designing the second switch tube N2, it is convenient to control the on and off of the second switch circuit, and the structure is simple and easy to control.

[0084] The first switch tube N1 and the second switch tube N2 are both high conduction voltage drop switch tubes.

[0085] In some embodiments of the present application, the first switch tube N1 is an NPN transistor; the base of the first switch tube N1 is connected to the cathode of the second voltage-stabilizing diode ZD2; the collector of the first switch tube N1 is connected to the DC power supply VDD through the pull-up resistor R7; and the emitter of the first switch tube N1 is grounded (AGND).

[0086] The base of the first switch tube N1 is grounded through a bias resistor R6. The resistor R6 provides a bias voltage for the first transistor N1, and can turn on the first transistor N1 when the cathode voltage Uc of the first voltage stabilizing diode ZD1 is greater than the bias voltage of the first transistor N1.

[0087] In some embodiments of the present application, the second switch tube N2 is an NPN transistor; the base of the second switch tube N2 is connected to the collector of the first switch tube N1; the collector of the second switch tube N2 is connected to the DC power supply VDD through the second current limiting resistor R9; the emitter of the second switch tube N2 is connected to the positive power supply end of the alarm; and the negative power supply end of the alarm is grounded.

[0088] The base of the second switch tube N1 is grounded (AGND) through a resistor R8 . The resistor R8 provides a bias voltage for the transistor N2 .

[0089] In some embodiments of the present application, in order to further improve circuit safety, one end of the first current limiting resistor R4 is connected to the anode of the first voltage zener diode ZD1; the other end of the first current limiting resistor R4 is grounded (AGND) through the first electrolytic capacitor E2; the other end of the first current limiting resistor R4 is connected to the cathode of the second voltage zener diode ZD2 through the third current limiting resistor R5, see Figure 3 shown.

[0090] The first electrolytic capacitor E2 is used for filtering to ensure the voltage flowing to the first switch circuit is stable; the third current limiting resistor R5 plays a current limiting role to ensure circuit safety.

[0091] When the output voltage Ubr of the filter rectifier circuit is greater than the set threshold, the cathode voltage Uc of the second voltage stabilizing diode ZD2 is greater than the bias voltage required for the first transistor N1 to conduct, the first transistor N1 is saturated and conducted, and the current provided by the DC power supply VDD flows through the collector and emitter of the first transistor N1 to AGND via the resistor R7. At this time, the voltage value Uo across the resistor R8 is 0, the second transistor N2 is turned off, no current flows through the collector and emitter of the second transistor N2, and the buzzer does not work.

[0092] When the output voltage Ubr of the filter rectifier circuit is less than the set threshold, the cathode voltage Uc of the second voltage stabilizing diode ZD2 is less than the bias voltage required for the first transistor N1 to turn on, the first transistor N1 is turned off, and the current provided by the DC power supply VDD passes through the resistors R7 and R8 to AGND. The voltage Uo across the resistor R8 is greater than the bias voltage required for the second transistor N2 to turn on, and the second transistor N2 is saturated and turned on. At this time, the current provided by the DC power supply VDD passes through the resistor R9, the collector and emitter of the second transistor N2, and flows through the buzzer to AGND, and the buzzer emits an alarm sound, realizing the alarm action.

[0093] Embodiment 2

[0094] Based on the design of the undervoltage alarm circuit of the first embodiment, the second embodiment further proposes a refrigerator, including a power supply circuit and the undervoltage alarm circuit, see Figures 6 to 10 shown.

[0095] The power supply circuit includes a filter rectifier circuit and a voltage conversion circuit. The positive output terminal of the filter rectifier circuit is connected to the undervoltage alarm circuit and the voltage conversion circuit respectively; the negative output terminal of the filter rectifier circuit is grounded (AGND).

[0096] The power supply circuit is designed on the power supply board, and the undervoltage alarm circuit can also be designed on the power supply board to save space.

[0097] The refrigerator of this embodiment can detect the undervoltage of the mains power by designing an undervoltage alarm circuit, and promptly issue an alarm prompt when the mains power is undervoltage, so as to promptly notify the user of the undervoltage state of the refrigerator, thereby solving the technical problem of failing to promptly issue an alarm prompt when the mains power is undervoltage in the prior art, improving the user's usage experience, and enhancing the competitiveness of the refrigerator.

[0098] In some embodiments of the present application, the filtering and rectifying circuit includes a live terminal IN1, a neutral terminal IN2, a positive output terminal OUT1, a negative output terminal OUT2, a fuse FUSE1, a varistor RV1, a thermistor NTC1, a filtering circuit, a rectifying circuit, etc.

[0099] The live terminal IN1 is connected to the first input end of the filter circuit through a fuse FUSE1; the neutral terminal IN2 is connected to the second input end of the filter circuit.

[0100] A varistor RV1 is connected between the first input terminal and the second input terminal of the filter circuit.

[0101] The first output end of the filter circuit is connected to the first input end of the rectifier circuit; the second output end of the filter circuit is connected to the second input end of the rectifier circuit through the thermistor NTC1.

[0102] The first output end of the rectifier circuit is connected to the positive output end OUT1 ; the second output end of the rectifier circuit is connected to the negative output end OUT2 .

[0103] The filter circuit is used to filter the input alternating current and output the filtered alternating current.

[0104] The rectifier circuit is used to rectify the filtered alternating current and output direct current.

[0105] When the voltage across the varistor RV1 exceeds its threshold, the varistor RV1 is turned on, short-circuiting the subsequent circuit. The current passing through the fuse FUSE1 exceeds the current threshold, and the fuse FUSE1 blows, preventing the voltage connected to the filter circuit from being too high, thereby protecting the circuit.

[0106] The resistance of the thermistor NTC1 increases as the temperature increases. When the temperature is high, the resistance of the thermistor NTC1 is large, thereby reducing the current flowing through to ensure circuit safety.

[0107] By designing the filter and rectifier circuit of the above structure, the filtering and rectifying functions are realized, and the safety of the subsequent circuit is ensured through the fuse FUSE1, the varistor RV1 and the thermistor NTC1.

[0108] In some embodiments of the present application, in order to improve the filtering effect, the filtering circuit includes a resistor circuit, a first filtering capacitor CX1, a common mode inductor LX1, and a second filtering capacitor CX2, see Figure 3 , Figure 4 shown.

[0109] The common mode inductor LX1 includes a first winding and a second winding.

[0110] The input end of the first winding is connected to the live terminal IN1 through a fuse FUSE1; the input end of the second winding is connected to the neutral terminal IN2.

[0111] A resistor circuit and a filter capacitor CX1 are connected in parallel between the input end of the first winding and the input end of the second winding. The filter capacitor CX1 is used to filter out clutter.

[0112] The resistor circuit includes three resistors connected in series.

[0113] A filter capacitor CX2 is connected between the output end of the first winding and the output end of the second winding to filter out clutter.

[0114] In some embodiments of the present application, the rectifier circuit is a rectifier bridge BD1, which is constructed by four diodes and has a simple structure.

[0115] An electrolytic capacitor E1 is connected in parallel between the positive output terminal OUT1 and the negative output terminal OUT2 of the filter and rectifier circuit to filter the output voltage.

[0116] The voltage conversion circuit is used to provide a stable low-voltage DC power supply for the entire refrigerator.

[0117] The positive output terminal OUT1 and the negative output terminal OUT2 of the filter and rectifier circuit output high-voltage DC power, which is converted by the voltage conversion circuit to generate a stable low-voltage DC power.

[0118] In some embodiments of the present application, the voltage conversion circuit includes a switching power supply chip IC1, a transformer T1, a DC filter circuit, a DC output terminal OUT, etc. Figure 4 shown.

[0119] The DC filter circuit is used to filter the DC power. The input end of the DC filter circuit is connected to the secondary winding of the transformer T1, and the output end of the DC filter circuit is connected to the DC output end OUT.

[0120] The switching power supply chip IC1 controls the operation of the transformer T1, which controls the transformer T1 to step down the received high-voltage DC power supply to generate a low-voltage DC power supply, which is then output to the DC filter circuit. After filtering by the DC filter circuit, the DC output terminal OUT outputs a stable low-voltage DC power supply.

[0121] The transformer T1 has a first primary winding, a second primary winding, and a secondary winding.

[0122] The opposite-name end of the first primary winding is connected to the positive output end OUT1 of the filter and rectifier circuit.

[0123] The same-name end of the first primary winding is connected to the drain pin D of the switching power chip IC1.

[0124] The source pin S of the switching power supply chip IC1 is grounded (AGND).

[0125] The control pin C of the switching power supply chip IC1 is connected to the output end of the light receiving end of the optocoupler IC2; the input end of the light receiving end of the optocoupler IC2 is connected to the same-name end of the second primary winding; and the opposite-name end of the second primary winding is grounded (AGND).

[0126] The input end of the light-emitting end of the optocoupler IC2 is connected to the same-name end of the secondary winding through the current-limiting resistor R19, the output end of the light-emitting end of the optocoupler IC2 is connected to the cathode of the three-terminal voltage regulator IC3, the anode of the three-terminal voltage regulator IC3 is grounded (GND), and the reference level of the three-terminal voltage regulator IC3 is connected to the DC output terminal OUT through a voltage divider circuit; the same-name end of the secondary winding is connected to the DC output terminal OUT through a DC filter circuit; the opposite-name end of the secondary winding is grounded (GND).

[0127] The voltage monitoring pin V of the switching power supply chip IC1 is connected to the positive output terminal OUT1 of the filter rectifier circuit through a resistor circuit for voltage monitoring. When the voltage at the voltage monitoring pin V is detected to be less than a low threshold (undervoltage occurs) or greater than a high threshold (overvoltage occurs), the connection between the drain pin D and the source pin S can be cut off, that is, the transformer is turned off, the DC power supply is cut off, and undervoltage protection and overvoltage protection are achieved.

[0128] Therefore, the voltage conversion circuit has undervoltage and overvoltage protection functions. When the AC voltage is lower than the lower limit of the voltage range or higher than the upper limit of the voltage range, the power supply automatically protects itself, turns off the output, and the refrigerator stops working.

[0129] The resistance circuit includes resistances R14, R13, and R12 connected in series.

[0130] The external current limit pin X of the switching power supply chip IC1 is connected to ground (AGND) through a resistor R15.

[0131] The frequency pin F of the switching power supply chip IC1 is connected to the control pin C.

[0132] The voltage divider circuit includes a resistor R22 and a resistor R23 connected in series. The DC output terminal OUT is grounded (GND) through the voltage divider circuit. The reference level of the three-terminal voltage regulator IC3 is connected to the voltage divider node of the resistor R22 and the resistor R23.

[0133] The voltage outputted from the DC output terminal OUT affects the conduction of the three-terminal voltage regulator IC3, thereby affecting the current at the light-emitting end of the optocoupler IC2, and further affecting the control pin C of the switching power supply chip IC1 through the light-receiving end of the optocoupler IC1. The control pin C controls the on-off state between the drain pin D and the source pin S, thereby controlling the operation of the transformer T1.

[0134] Therefore, the output voltage of the DC output terminal OUT is fed back to the switching power supply chip IC1 through the three-terminal voltage regulator IC3 and the optical coupler IC1, thereby controlling the operation of the transformer T1, so that the DC output terminal OUT outputs a stable low-voltage DC power supply.

[0135] In some embodiments of the present application, the drain pin D of the switching power supply chip IC1 is connected to the anode of the first diode D1, the cathode of the first diode D1 is connected to one end of the RC parallel circuit, and the other end of the RC parallel circuit is connected to the positive output end OUT1 of the filter rectifier circuit.

[0136] The first diode D1 is used to prevent the current of the positive output terminal OUT1 from flowing to the drain pin D of the switching power supply chip IC1. When the drain pin D is disconnected from the source pin S, a reverse electromotive force is generated, which is transmitted to the RC parallel circuit through the first diode D1 and filtered out by the RC parallel circuit to ensure circuit safety.

[0137] In some embodiments of the present application, the same-name end of the second primary winding is connected to the anode of the second diode D2, and the cathode of the second diode D2 is connected to the input end of the light-receiving end of the optocoupler IC2 to ensure the current direction.

[0138] The cathode of the second diode D2 is grounded through a parallel circuit of an electrolytic capacitor E3 and a resistor R16 for filtering and stabilizing the circuit.

[0139] The same-name end of the second primary winding provides a DC power supply VDD for the voltage detection circuit and the alarm circuit.

[0140] In some embodiments of the present application, the DC filter circuit includes a third diode D3, an inductor L1, a second electrolytic capacitor E5, a third electrolytic capacitor E6, a first filter capacitor C7, a second filter capacitor C8, etc.

[0141] The same-name end of the secondary winding of the transformer T1 is connected to the anode of the third diode D3 , the cathode of the third diode D3 is connected to one end of the inductor L1 , and the other end of the inductor L1 is connected to the DC output end OUT.

[0142] The positive electrode of the second electrolytic capacitor E5 is connected to one end of the inductor L, and the negative electrode of the second electrolytic capacitor E5 is grounded (GND); the first filter capacitor C7 is connected in parallel to both ends of the second electrolytic capacitor E5.

[0143] The positive electrode of the third electrolytic capacitor E6 is connected to the other end of the inductor L1, and the negative electrode of the third electrolytic capacitor E6 is grounded (GND); the second filter capacitor C8 is connected in parallel to both ends of the third electrolytic capacitor E6.

[0144] By designing the DC filter circuit, the clutter in the DC power can be effectively filtered out, ensuring that the DC output terminal OUT outputs a stable low-voltage DC power supply.

[0145] In some embodiments of the present application, in order to further improve the filtering effect, an RC series circuit is connected in parallel between the two ends of the third diode D3, and the RC series circuit is formed by a capacitor C4 and a resistor R18 connected in series.

[0146] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0147] The above is only a specific implementation of the utility model, but the protection scope of the utility model is not limited to this. Any changes or substitutions that can be easily thought of by technicians familiar with the technical field within the technical scope disclosed by the utility model should be included in the protection scope of the utility model. Therefore, the protection scope of the utility model should be based on the protection scope of the claims.

Claims

1. An undervoltage alarm circuit for a refrigerator, the refrigerator comprising a power supply circuit, the power supply circuit comprising a filter rectifier circuit; characterized in that: The undervoltage alarm circuit comprises: A voltage detection circuit, comprising a first voltage zener diode, a second voltage zener diode, and a first switch circuit; the cathode of the first voltage zener diode is connected to the positive output end of the filter rectifier circuit; the anode of the first voltage zener diode is connected to the cathode of the second voltage zener diode through a first current limiting resistor, the anode of the second voltage zener diode is grounded, the cathode of the second voltage zener diode is connected to the control end of the first switch circuit, one end of the switch path of the first switch circuit is connected to a DC power supply through a pull-up resistor, and the other end of the switch path of the first switch circuit is grounded; The alarm circuit comprises a second switch circuit and an alarm; the control end of the second switch circuit is connected to one end of the switch path of the first switch circuit, and the switch path of the second switch circuit is connected in series in the power supply circuit of the alarm.

2. The undervoltage alarm circuit according to claim 1, characterized in that: The first switch circuit includes a first switch tube; The control end of the first switch tube is connected to the cathode of the second voltage stabilizing diode; One end of the switch path of the first switch tube is connected to a DC power supply through the pull-up resistor; The other end of the switch path of the first switch tube is grounded.

3. The undervoltage alarm circuit according to claim 2, characterized in that: The second switch circuit includes a second switch tube; The control end of the second switch tube is connected to one end of the switch path of the first switch tube; One end of the switch path of the second switch tube is connected to a DC power supply via a second current limiting resistor; The other end of the switch path of the second switch tube is connected to the positive power supply end of the alarm; the negative power supply end of the alarm is grounded.

4. The undervoltage alarm circuit according to claim 1, characterized in that: One end of the first current limiting resistor is connected to the anode of the first voltage stabilizing diode; The other end of the first current limiting resistor is grounded via a first electrolytic capacitor; The other end of the first current limiting resistor is connected to the cathode of the second voltage stabilizing diode through a third current limiting resistor.

5. The undervoltage alarm circuit according to any one of claims 1 to 4, characterized in that: The alarm includes a buzzer and / or an indicator light.

6. A refrigerator, characterized in that include: An undervoltage alarm circuit as claimed in any one of claims 1 to 5; A power supply circuit, which includes a filter rectification circuit and a voltage conversion circuit; The positive output end of the filtering and rectifying circuit is connected to the undervoltage alarm circuit and the voltage conversion circuit respectively; the negative output end of the filtering and rectifying circuit is grounded.

7. The refrigerator according to claim 6, characterized in that: The voltage conversion circuit includes a switching power supply chip, a transformer, a DC filter circuit, and a DC output terminal; The opposite-name end of the first primary winding of the transformer is connected to the positive output end of the filter and rectifier circuit; The same-name end of the first primary winding is connected to the drain pin of the switching power supply chip; The source pin of the switching power supply chip is grounded; The control pin of the switching power supply chip is connected to the output end of the light receiving end of the optocoupler; the input end of the light receiving end of the optocoupler is connected to the same-name end of the second primary winding of the transformer; the opposite-name end of the second primary winding is grounded; The input end of the light-emitting end of the optocoupler is connected to the same-name end of the secondary winding of the transformer, the output end of the light-emitting end of the optocoupler is connected to the cathode of a three-terminal voltage regulator, the anode of the three-terminal voltage regulator is grounded, and the reference level of the three-terminal voltage regulator is connected to the DC output end through a voltage divider circuit; the same-name end of the secondary winding is connected to the DC output end through the DC filter circuit; the opposite-name end of the secondary winding is grounded.

8. The refrigerator according to claim 7, characterized in that: The drain pin of the switching power supply chip is connected to the anode of the first diode, the cathode of the first diode is connected to one end of the RC parallel circuit, and the other end of the RC parallel circuit is connected to the positive output end of the filtering and rectifying circuit.

9. The refrigerator according to claim 7, characterized in that: The same-name end of the second primary winding is connected to the anode of the second diode, and the cathode of the second diode is connected to the input end of the light-receiving end of the optocoupler; The cathode of the second diode is grounded through a parallel circuit of an electrolytic capacitor and a resistor.

10. The refrigerator according to claim 7, characterized in that: The DC filter circuit includes a third diode, an inductor, a second electrolytic capacitor, a third electrolytic capacitor, a first filter capacitor, and a second filter capacitor; The same-name end of the secondary winding is connected to the anode of the third diode, the cathode of the third diode is connected to one end of the inductor, and the other end of the inductor is connected to the DC output end; The positive electrode of the second electrolytic capacitor is connected to one end of the inductor, and the negative electrode of the second electrolytic capacitor is grounded; the first filter capacitor is connected in parallel to both ends of the second electrolytic capacitor; The positive electrode of the third electrolytic capacitor is connected to the other end of the inductor, and the negative electrode of the third electrolytic capacitor is grounded; the second filter capacitor is connected in parallel to both ends of the third electrolytic capacitor.

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