Doorbell AC power supply circuit

Abstract

The utility model discloses a doorbell AC power supply circuit comprising a control unit, an AC interface, an AC rectification and protection circuit, a short circuit, an AC determination circuit, a DC-DC circuit, a battery charging circuit and a doorbell detection circuit. The corresponding end of the control unit is electrically connected with the corresponding ends of the short-circuit circuit, the AC judgment circuit, the DC-DC circuit and the doorbell detection circuit. The corresponding end of the AC rectification and protection circuit is electrically connected with the corresponding ends of the AC interface, the short circuit, the AC judgment circuit and the DC-DC circuit, and the corresponding end of the DC-DC circuit is also connected with the battery charging circuit. According to the utility model, through the efficient AC rectification and protection circuit and the DC-DC circuit, the system can convert an unstable AC power supply into a stable low-voltage DC power supply, thereby ensuring that the doorbell system can operate stably under various power supply conditions.

Description

Technical Field

[0001] This utility model relates to the field of doorbell power supply technology, and in particular to a doorbell AC power supply circuit. Background Technology

[0002] Traditional doorbell systems typically rely on a direct connection to AC power. While this works when the power supply is stable, its functionality is affected by instability or interruption. Furthermore, many existing doorbell systems lack effective battery backup, failing to maintain operation during power failures. For systems containing traditional mechanical doorbells, responsiveness significantly degrades under unstable power conditions. With the increasing prevalence of smart home systems, the demands for efficiency and reliability in doorbell systems are rising, necessitating a doorbell power supply and charging system capable of stable operation under various power conditions.

[0003] Existing doorbell power supply system designs typically involve complex circuits and control logic, but lack specific system functionality and are inadequate in handling AC power short circuits and battery charging. For example, some systems may fail to protect the circuit during AC power short circuits or provide constant current and voltage during battery charging, potentially leading to degraded battery performance and shortened battery life. Utility Model Content

[0004] To address the problems existing in the prior art, this utility model provides an AC power supply circuit for a doorbell.

[0005] To achieve the above objectives, the technical solution of this utility model is as follows:

[0006] This utility model provides a doorbell AC power supply circuit, including: a control unit, an AC interface, an AC rectification and protection circuit, a short circuit circuit, an AC judgment circuit, a DC-DC circuit, a battery charging circuit, and a doorbell detection circuit;

[0007] The corresponding terminals of the control unit are electrically connected to the corresponding terminals of the short-circuit circuit, AC judgment circuit, DC-DC circuit, and doorbell detection circuit, respectively.

[0008] The corresponding terminals of the AC rectification and protection circuit are electrically connected to the corresponding terminals of the AC interface, short circuit circuit, AC judgment circuit, and DC-DC circuit, respectively. The corresponding terminal of the DC-DC circuit is also connected to the battery charging circuit.

[0009] The AC interface is used for AC power connection;

[0010] The AC rectification and protection circuit is used to convert the input AC power supply into a stable DC power supply.

[0011] The short-circuit circuit is used to short-circuit the AC power supply to support the doorbell ringing operation;

[0012] The AC detection circuit is used to detect the AC power supply status;

[0013] The DC-DC circuit is used to convert the high-voltage power input from the AC rectification and protection circuit into a low-voltage usable power supply.

[0014] The battery charging circuit is used to convert available power into constant current and constant voltage power for use by the lithium battery.

[0015] The doorbell detection circuit is used to detect doorbell button commands.

[0016] Preferably, the doorbell AC power supply circuit further includes a connector, the corresponding ends of which are electrically connected to the corresponding ends of the DC-DC circuit and the battery charging circuit, respectively; the control unit is configured as an MCU.

[0017] Preferably, the AC rectification and protection circuit consists of an AC input access and protection circuit, an AC rectification circuit, and an input voltage regulator circuit;

[0018] The AC input access and protection circuit includes a primary protection circuit, a diode protection circuit, and a common-mode protection circuit. The primary protection circuit includes a fuse F1 and a varistor RV1. The diode protection circuit consists of a fuse F2, a diode ESD1, a diode D11, and a diode ESD2. The common-mode protection circuit consists of a ferrite bead R1, a ferrite bead R2, and a common-mode inductor L5.

[0019] The AC rectifier circuit includes a rectifier diode VD1;

[0020] The input voltage regulator circuit includes capacitors C1, C30, C31, C32, C33, and C34.

[0021] The first end of the fuse F1 is connected to the negative input terminal of the AC power supply, and the second end of the fuse F1 is electrically connected to the first end of the varistor RV1 and the second pin of the rectifier diode VD1. The second end of the varistor RV1 is electrically connected to the positive input terminal of the AC power supply and the first pin of the rectifier diode VD1.

[0022] The third pin of the rectifier diode VD1 is electrically connected to the first terminal of diode ESD1 and fuse F2, respectively, and the fourth pin of the rectifier diode VD1 is electrically connected to the second terminal of diode ESD1 and the first terminal of diode D11, respectively.

[0023] The second end of the fuse F2 is electrically connected to the first end of the ferrite bead R1 and the fourth pin of the common mode inductor L5, respectively; the second end of the diode D11 is electrically connected to the first end of the ferrite bead R2 and the first pin of the common mode inductor L5, respectively.

[0024] The second end of the ferrite bead R1 is electrically connected to the third pin of the common mode inductor L5, capacitor C1, diode ESD2, capacitor C30, capacitor C31, capacitor C32, capacitor C33, and capacitor C34, respectively; the second end of the ferrite bead R2 is electrically connected to the second pin of the common mode inductor L5, capacitor C1, diode ESD2, capacitor C30, capacitor C31, capacitor C32, capacitor C33, and capacitor C34, respectively.

[0025] Preferably, the DC-DC circuit includes a power chip U1, resistors R4, R5, R7, R9, R11, R47, capacitors C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, diode D3, and inductor L3.

[0026] The first pin of the power chip U1 is electrically connected to the first end of capacitor C2, diode D3, and inductor L3 respectively. The second end of capacitor C2 is electrically connected to the eighth pin of power chip U1. The second end of diode D3 is grounded. The second end of inductor L3 is electrically connected to the first end of capacitor C4, capacitor C7, capacitor C3, resistor R5, and capacitor C8 respectively.

[0027] The fourth pin of the power chip U1 is electrically connected to the first end of resistor R7, the second end of resistor R5, and the second end of capacitor C8, respectively, and the second end of resistor R7 is grounded.

[0028] The third pin of the power chip U1 is electrically connected to the first end of capacitor C10, capacitor C11 and resistor R11 respectively. The second ends of capacitor C10 and capacitor C11 are grounded, and the second end of resistor R11 is electrically connected to the input voltage AC_DC_5V_F terminal.

[0029] The 7th pin of the power chip U1 is electrically connected to the first terminals of resistor R4, capacitor C6, and capacitor C5 respectively. The second terminal of resistor R4 is electrically connected to the DC_VIN_CTRL signal terminal, the first terminal of resistor R47, the 2nd pin of power chip U1, and the first terminal of capacitor C9 respectively. The second terminal of capacitor C9 is electrically connected to the second terminal of resistor R47 and grounded. The second terminals of capacitors C6 and C5 are both grounded. The 6th pin of power chip U1 is grounded through resistor R9.

[0030] Preferably, the short-circuit circuit includes diode D6, diode D10, resistor R3, resistor R12, resistor R39, resistor R53, MOSFET Q1, and MOSFET Q3.

[0031] The drain of MOSFET Q1 is electrically connected to the first terminal of resistor R3 and diode D10, respectively. The gate of MOSFET Q1 is electrically connected to the first terminal of resistor R39, resistor R3, and the second terminal of diode D10 via resistor R53. The second terminal of resistor R39 is electrically connected to the source of MOSFET Q3. The gate of MOSFET Q3 is electrically connected to the first terminal of resistor R12 and diode D6, respectively. The drain of MOSFET Q1 is electrically connected to the second terminal of resistor R12. The second terminal of diode D6 is connected to the MC_TIME_CTRL signal terminal.

[0032] Preferably, the AC judgment circuit includes a comparator circuit and a voltage regulator circuit electrically connected to the corresponding terminal of the comparator circuit;

[0033] The voltage regulator circuit includes capacitor C17, capacitor C18, resistor R54, and voltage regulator chip U8. The first pin of voltage regulator chip U8 is electrically connected to the first terminals of capacitor C17 and capacitor C18, the second pin of voltage regulator chip U8 is electrically connected to the second terminal of capacitor C17, and the third pin of voltage regulator chip U8 is electrically connected to the first terminal of resistor R54, the second terminal of capacitor C18, and the corresponding terminal of comparator circuit.

[0034] The comparator circuit includes a comparator chip U19, resistors R24, R25, R26, R27, R29, R33, R41, R42, R51, capacitor C16, and capacitor C19. The first pin of the comparator chip U19 is electrically connected to the first terminals of resistors R29, R33, and capacitor C16, respectively. The second terminal of resistor R33 is electrically connected to the second terminal of capacitor C16 and grounded.

[0035] The third pin of the comparator chip U19 is electrically connected to the first terminals of resistors R41 and R42, respectively. The second terminal of resistor R41 is electrically connected to the first terminals of resistors R25, C19, and R24, respectively. The second terminal of resistor R25 is electrically connected to the second pin of comparator chip U19 and the second terminal of capacitor C19, respectively. The second terminal of resistor R42 is electrically connected to the fourth pin of comparator chip U19, the first terminals of resistors R26 and R51, respectively. The second terminal of resistor R26 is electrically connected to the fifth pin of comparator chip U19, and the second terminal of resistor R51 is grounded through resistor R27.

[0036] Preferably, the battery charging circuit includes a charging constant current circuit and a constant voltage measurement circuit;

[0037] The constant current charging circuit includes a constant current charging chip U2, resistors R34, R35, R36, and R37, a diode D9, a MOSFET Q6, capacitors C22, C23, C24, C25, and C26, and an inductor L4. The first pin of the constant current charging chip U2 is electrically connected to the first terminals of resistors R34, inductor L4, and capacitor C22. The second terminal of capacitor C22 is electrically connected to the first terminal of resistor R35 and the ninth pin of the constant current charging chip U2. The second terminal of resistor R35 is electrically connected to the second terminal of resistor R34 and the fifth pin of the constant current charging chip U2. The second terminal of inductor L4 is electrically connected to the third pin of the constant current charging chip U2 and the first terminal of diode D9. The second terminal of diode D9 is electrically connected to… The first terminal of capacitor C23 is electrically connected to the drain of MOSFET Q6, and the second terminal of capacitor C23 is grounded. The gate of MOSFET Q6 is electrically connected to pin 8 of constant current charging chip U2 and the first terminal of capacitor C24, and the second terminal of capacitor C24 is grounded. The source of MOSFET Q6 is electrically connected to pin 6 of constant current charging chip U2 and the first terminal of resistor R36. The second terminal of resistor R36 is electrically connected to pin 7 of constant current charging chip U2 and the first terminal of capacitor C25, and the second terminal of capacitor C25 is grounded. The second pin of constant current charging chip U2 is electrically connected to the first terminal of resistor R37 and capacitor C26. The second terminal of resistor R37 is electrically connected to pin 4 of constant current charging chip U2, and the second terminal of capacitor C26 is grounded.

[0038] The constant voltage measurement circuit includes a constant voltage charging chip U20, capacitor C20, capacitor C21, and capacitor C36; the first pin of the constant voltage charging chip U20 is electrically connected to the first terminals of capacitors C20, C21, and C36 respectively; the second pin of the constant voltage charging chip U20 is electrically connected to the second terminals of capacitors C20 and C36 respectively; and the third pin of the constant voltage charging chip U20 is electrically connected to the second terminal of capacitor C22.

[0039] Preferably, the doorbell detection circuit includes a resistor R20, a diode D4, a switch SW1, and a capacitor C15; the first end of the resistor R20 is electrically connected to the RST_KEY signal terminal and the first end of the capacitor C15, respectively; the second end of the resistor R20 is electrically connected to the first end of the diode D4 and the corresponding end of the switch SW1, respectively; the second ends of the capacitor C15 and the diode D4 are both grounded.

[0040] The technical solution of this utility model has the following beneficial effects:

[0041] This invention can adapt to a wide range of AC power input (10-24VAC), ensuring the doorbell works normally even under unstable or poor power conditions, thereby improving the system's applicability and reliability. It can maintain power supply for multiple power systems, eliminating the need to charge batteries after connecting to AC. Through efficient AC rectification and protection circuits and DC-DC circuits, the system can convert unstable AC power into stable low-voltage DC power, ensuring the doorbell system can operate stably under various power conditions.

[0042] Efficient battery charging management: The battery charging circuit adopts a constant current and constant voltage charging method to ensure that the lithium battery is neither overcharged nor undercharged during the charging process, thereby improving the battery's lifespan and charging efficiency.

[0043] Compatible with traditional and modern doorbells: Through the design of the short-circuit circuit, the system can support the operation of traditional mechanical doorbells when the AC power is shorted, while maintaining compatibility with modern electronic doorbells.

[0044] Fast-response doorbell detection: The doorbell detection circuit can quickly respond to the user's ringing action and promptly notify the MCU for processing, ensuring a fast doorbell response and improving the user experience.

[0045] Optimized power management logic: The MCU intelligently controls the switching on and off of the high-voltage DC-DC circuit based on the signal from the AC judgment circuit, thus optimizing the power management logic and reducing unnecessary energy consumption.

[0046] Enhanced system safety: The AC detection circuit can promptly output a signal to the MCU when abnormal power conditions are detected, triggering protection measures to protect the entire doorbell system from damage.

[0047] This invention integrates AC rectification and protection circuits, short-circuit circuits, AC judgment circuits, DC-DC circuits, battery charging circuits, and doorbell detection circuits. This design simplifies the circuit structure, reduces the number of components, and lowers costs and complexity.

[0048] Efficient battery management: The battery charging circuit adopts a constant current and constant voltage charging method, which effectively manages the battery charging process, extends the battery life, and ensures that the battery can provide a stable power supply when needed.

[0049] Supports traditional doorbell operation: Through the design of the short-circuit circuit, the system can support the operation of traditional mechanical doorbells when the AC power is shorted, maintaining compatibility with the old system.

[0050] Improved user experience: The system can automatically switch to battery power when the power supply is unstable or interrupted, ensuring the doorbell's continuous response and thus improving the user experience.

[0051] Reliable power supply judgment and protection: The AC judgment circuit can accurately monitor the power supply status and output a signal to the MCU in a timely manner when an unstable power supply is detected, triggering protection measures to protect the system from damage.

[0052] Easy to maintain and upgrade: The modular design of the system makes maintenance and upgrades simpler, reduces maintenance costs, and improves system scalability. Attached Figure Description

[0053] Figure 1 This is a circuit control block diagram of the present invention;

[0054] Figure 2 This is the circuit schematic diagram of the AC to DC rectifier and protection circuit of this utility model;

[0055] Figure 3 This is the circuit diagram of the AC short-circuit circuit of this utility model;

[0056] Figure 4 This is the circuit schematic diagram of the DC-DC circuit of this utility model;

[0057] Figure 5 This is a circuit diagram of the battery charging circuit of this utility model;

[0058] Figure 6 This is the circuit diagram of the AC judgment circuit of this utility model;

[0059] Figure 7 This is a circuit diagram of the doorbell detection circuit of this utility model;

[0060] Figure 8 This is a connection diagram of the circuit of this utility model when connected to a traditional mechanical doorbell.

[0061] Figure 9 This is a schematic diagram of the detection and control timing of this utility model. Detailed Implementation

[0062] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model.

[0063] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0064] Furthermore, 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, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0065] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0066] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0067] Reference Figures 1 to 9 This utility model provides a doorbell AC power supply circuit, including: a control unit 600, an AC interface 100, an AC rectification and protection circuit 200, a short circuit circuit 300, an AC judgment circuit 700, a DC-DC circuit 400, a battery charging circuit 500, and a doorbell detection circuit 800.

[0068] The corresponding terminals of the control unit 600 are electrically connected to the corresponding terminals of the short-circuit circuit 300, AC judgment circuit 700, DC-DC circuit 800, and doorbell detection circuit 800, respectively.

[0069] The corresponding terminals of the AC rectification and protection circuit 200 are electrically connected to the corresponding terminals of the AC interface 100, the short circuit circuit 300, the AC judgment circuit 700, and the DC-DC circuit 400, respectively. The corresponding terminal of the DC-DC circuit 400 is also connected to the battery charging circuit 500.

[0070] The AC interface 100 is used for AC power input;

[0071] The AC rectifier and protection circuit 700 is used to convert the input AC power supply into a stable DC power supply.

[0072] The short-circuit circuit 300 is used to short-circuit the AC power supply to support the doorbell ringing operation;

[0073] The AC detection circuit 700 is used to detect the AC power supply status;

[0074] The DC-DC circuit 400 is used to convert the high-voltage power input to the AC rectification and protection circuit 300 into a low-voltage usable power supply.

[0075] The battery charging circuit 500 is used to convert available power into constant current and constant voltage power for use by the lithium battery.

[0076] The doorbell detection circuit 800 is used to detect doorbell button commands.

[0077] Furthermore, the doorbell AC power supply circuit also includes a connector 900, whose corresponding ends are electrically connected to the corresponding ends of the DC-DC circuit 400 and the battery charging circuit 500, respectively. The control unit 600 is an MCU. Connector 900 serves as a connection point between internal circuits, allowing the outputs of the DC-DC circuit 400 and the battery charging circuit 500 to be flexibly connected to other system components. This design improves the system's scalability and adaptability, making the circuit design more modular and facilitating maintenance and upgrades. The microcontroller (MCU) as control unit 600: As the core control unit of the system, the MCU is responsible for coordinating the operation of various circuits, including the AC interface 100, AC rectification and protection circuit 200, short-circuit circuit 300, AC judgment circuit 700, DC-DC circuit 400, battery charging circuit 500, and doorbell detection circuit 800. The intelligent control logic of the MCU improves the system's efficiency and response speed while also reducing energy consumption.

[0078] Reference Figure 2The AC rectification and protection circuit 200 consists of an AC input access and protection circuit, an AC rectification circuit, and an input voltage regulator circuit.

[0079] The AC input access and protection circuit includes a primary protection circuit, a diode protection circuit, and a common-mode protection circuit. The primary protection circuit includes a fuse F1 and a varistor RV1, and can be connected via a connector or wire harness, etc. The primary protection circuit is used to cope with large current surges and voltage fluctuations, protecting the circuit from damage. The diode protection circuit consists of a fuse F2, diode ESD1, diode D11, and diode ESD2, and is used to prevent electrostatic discharge and other transient voltage surges, ensuring stable circuit operation. The common-mode protection circuit consists of ferrite beads R1 and R2, and a common-mode inductor L5, and is used to suppress common-mode noise, reduce electromagnetic interference, and improve circuit stability.

[0080] The AC rectifier circuit includes a rectifier diode VD1, which uses a TB310 to convert AC power to DC power. It is responsible for converting the AC power into pulsating DC power to provide DC power for the subsequent input voltage regulator circuit.

[0081] The input voltage regulator circuit includes capacitors C1, C30, C31, C32, C33, and C34, providing a minimum 400mA 9.5VAC power supply capability. Currently, a 330uF + 5*10uF voltage regulator is used; the input voltage regulator circuit is used to smooth the pulsating DC power after rectification and provide a stable DC power supply for subsequent circuits.

[0082] The first end of the fuse F1 is connected to the negative input terminal of the AC power supply, and the second end of the fuse F1 is electrically connected to the first end of the varistor RV1 and the second pin of the rectifier diode VD1, respectively, to ensure stable power supply connection and to disconnect the circuit through the fuse F1 in abnormal conditions to protect the system safety.

[0083] The second end of the varistor RV1 is electrically connected to the positive input terminal of the AC power supply and the first pin of the rectifier diode VD1, respectively, to absorb voltage fluctuations and protect the circuit from voltage surges.

[0084] The third pin of the rectifier diode VD1 is electrically connected to the first terminal of diode ESD1 and fuse F2, respectively. The fourth pin of the rectifier diode VD1 is electrically connected to the second terminal of diode ESD1 and the first terminal of diode D11, respectively, to complete the AC to DC conversion and provide protection for the subsequent circuit.

[0085] The second end of the fuse F2 is electrically connected to the first end of the ferrite bead R1 and the fourth pin of the common mode inductor L5, respectively, to provide further overcurrent protection and electromagnetic interference suppression for the circuit.

[0086] The second terminal of the diode D11 is electrically connected to the first terminal of the magnetic bead R2 and the first pin of the common mode inductor L5, respectively.

[0087] The second end of the ferrite bead R1 is electrically connected to the third pin of the common-mode inductor L5, capacitor C1, diode ESD2, capacitors C30, C31, C32, C33, and C34, respectively. The second end of the ferrite bead R2 is electrically connected to the second pin of the common-mode inductor L5, capacitor C1, diode ESD2, capacitors C30, C31, C32, C33, and C34, respectively. The second ends of ferrite beads R1 and R2 are connected to components such as the common-mode inductor L5 and capacitor C1, forming a common-mode protection circuit, which effectively reduces electromagnetic interference and improves circuit stability.

[0088] Reference Figure 4 The DC-DC circuit 400 includes a power chip U1, resistors R4, R5, R7, R9, R11, R47, capacitors C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, diode D3, and inductor L3.

[0089] The first pin of the power chip U1 is electrically connected to the first end of capacitor C2, diode D3, and inductor L3 respectively. The second end of capacitor C2 is electrically connected to the eighth pin of power chip U1. The second end of diode D3 is grounded. The second end of inductor L3 is electrically connected to the first end of capacitor C4, capacitor C7, capacitor C3, resistor R5, and capacitor C8 respectively.

[0090] The fourth pin of the power chip U1 is electrically connected to the first end of resistor R7, the second end of resistor R5, and the second end of capacitor C8, respectively, and the second end of resistor R7 is grounded.

[0091] The third pin of the power chip U1 is electrically connected to the first end of capacitor C10, capacitor C11 and resistor R11 respectively. The second ends of capacitor C10 and capacitor C11 are grounded, and the second end of resistor R11 is electrically connected to the input voltage AC_DC_5V_F terminal.

[0092] The 7th pin of the power chip U1 is electrically connected to the first terminals of resistor R4, capacitor C6, and capacitor C5 respectively. The second terminal of resistor R4 is electrically connected to the DC_VIN_CTRL signal terminal, the first terminal of resistor R47, the 2nd pin of power chip U1, and the first terminal of capacitor C9 respectively. The second terminal of capacitor C9 is electrically connected to the second terminal of resistor R47 and grounded. The second terminals of capacitors C6 and C5 are both grounded. The 6th pin of power chip U1 is grounded through resistor R9.

[0093] In this design, U1 is composed of the JW5121 power supply chip, and the entire circuit meets the 5V 1.5A load capacity requirement. The DC-DC circuit is the key component responsible for converting the input high-voltage power supply into a low-voltage power supply suitable for the system. The design of this circuit ensures the stability of the power supply and the energy efficiency of the system. Power supply chip U1: As the core of the DC-DC circuit, it is responsible for controlling the voltage conversion process, ensuring the stability and adjustability of the output voltage. Resistors, capacitors, and inductors: These components work together to provide filtering, stabilization, and energy storage functions, ensuring the quality of the output voltage.

[0094] Reference Figure 3 The short-circuit circuit 300 includes diode D6, diode D10, resistor R3, resistor R12, resistor R39, resistor R53, MOSFET Q1, and MOSFET Q3.

[0095] The drain of MOSFET Q1 is electrically connected to the first terminal of resistor R3 and diode D10, respectively. The gate of MOSFET Q1 is electrically connected to the first terminal of resistor R39, resistor R3, and the second terminal of diode D10 via resistor R53. The second terminal of resistor R39 is electrically connected to the source of MOSFET Q3. The gate of MOSFET Q3 is electrically connected to the first terminal of resistor R12 and diode D6, respectively. The drain of MOSFET Q1 is electrically connected to the second terminal of resistor R12. The second terminal of diode D6 is connected to the MC_TIME_CTRL signal terminal.

[0096] In this embodiment, the design uses a DMP6180SK MOSFET Q3. The MCU controls the conduction of MOSFET Q3 to turn on MOSFET Q1. Under normal circumstances, MOSFET Q1 is off, and the AC power supply only powers the system and charges the battery. The short-circuit circuit is a key component of the doorbell power supply system; it is responsible for short-circuiting the AC power supply under specific conditions to support the normal operation of the doorbell. This circuit design aims to improve system flexibility and user experience.

[0097] Reference Figure 6 The AC judgment circuit 700 includes a comparator circuit and a voltage regulator circuit electrically connected to the corresponding terminal of the comparator circuit.

[0098] The voltage regulator circuit includes capacitor C17, capacitor C18, resistor R54, and voltage regulator chip U8. The first pin of voltage regulator chip U8 is electrically connected to the first terminals of capacitor C17 and capacitor C18, the second pin of voltage regulator chip U8 is electrically connected to the second terminal of capacitor C17, and the third pin of voltage regulator chip U8 is electrically connected to the first terminal of resistor R54, the second terminal of capacitor C18, and the corresponding terminal of comparator circuit.

[0099] The comparator circuit includes a comparator chip U19, resistors R24, R25, R26, R27, R29, R33, R41, R42, R51, capacitor C16, and capacitor C19. The first pin of the comparator chip U19 is electrically connected to the first terminals of resistors R29, R33, and capacitor C16, respectively. The second terminal of resistor R33 is electrically connected to the second terminal of capacitor C16 and grounded.

[0100] The third pin of the comparator chip U19 is electrically connected to the first terminals of resistors R41 and R42, respectively. The second terminal of resistor R41 is electrically connected to the first terminals of resistors R25, C19, and R24, respectively. The second terminal of resistor R25 is electrically connected to the second pin of comparator chip U19 and the second terminal of capacitor C19, respectively. The second terminal of resistor R42 is electrically connected to the fourth pin of comparator chip U19, the first terminals of resistors R26 and R51, respectively. The second terminal of resistor R26 is electrically connected to the fifth pin of comparator chip U19, and the second terminal of resistor R51 is grounded through resistor R27.

[0101] In this embodiment, a hysteresis comparator circuit composed of U19 (model AS331A) is used. The power supply for this part is provided by a 5V output from a U8 (SE8650) LDO. The AC judgment circuit is responsible for monitoring and judging the state of the AC power supply, ensuring that the system can operate stably under different power conditions. This circuit provides accurate power judgment and stable power output through the combination of the comparator circuit and the voltage regulator circuit. The voltage regulator circuit provides a stable power supply to the comparator circuit, ensuring the operational stability of the comparator chip U19. The comparator circuit monitors the state of the AC power supply and outputs corresponding signals according to the power state. The voltage regulator circuit provides a stable power supply to the comparator circuit, ensuring the operational stability of the comparator chip U19, thereby improving the reliability of the entire AC judgment circuit. The comparator circuit can accurately monitor the state of the AC power supply, providing accurate power judgment for the system and ensuring stable operation under different power conditions.

[0102] Stable power supply judgment and output improve the system's response speed and reliability, thereby enhancing the end-user experience.

[0103] Reference Figure 5 The battery charging circuit 500 includes a charging constant current circuit and a constant voltage measurement circuit;

[0104] The constant current charging circuit includes a constant current charging chip U2, resistors R34, R35, R36, and R37, a diode D9, a MOSFET Q6, capacitors C22, C23, C24, C25, and C26, and an inductor L4. The first pin of the constant current charging chip U2 is electrically connected to the first terminals of resistors R34, inductor L4, and capacitor C22. The second terminal of capacitor C22 is electrically connected to the first terminal of resistor R35 and the ninth pin of the constant current charging chip U2. The second terminal of resistor R35 is electrically connected to the second terminal of resistor R34 and the fifth pin of the constant current charging chip U2. The second terminal of inductor L4 is electrically connected to the third pin of the constant current charging chip U2 and the first terminal of diode D9. The second terminal of diode D9 is electrically connected to… The first terminal of capacitor C23 is electrically connected to the drain of MOSFET Q6, and the second terminal of capacitor C23 is grounded. The gate of MOSFET Q6 is electrically connected to pin 8 of constant current charging chip U2 and the first terminal of capacitor C24, and the second terminal of capacitor C24 is grounded. The source of MOSFET Q6 is electrically connected to pin 6 of constant current charging chip U2 and the first terminal of resistor R36. The second terminal of resistor R36 is electrically connected to pin 7 of constant current charging chip U2 and the first terminal of capacitor C25, and the second terminal of capacitor C25 is grounded. The second pin of constant current charging chip U2 is electrically connected to the first terminal of resistor R37 and capacitor C26. The second terminal of resistor R37 is electrically connected to pin 4 of constant current charging chip U2, and the second terminal of capacitor C26 is grounded.

[0105] The constant voltage measurement circuit includes a constant voltage charging chip U20, capacitors C20, C21, and C36. The first pin of the constant voltage charging chip U20 is electrically connected to the first terminals of capacitors C20, C21, and C36, respectively. The second pin of the constant voltage charging chip U20 is electrically connected to the second terminals of capacitors C20 and C36, respectively. The third pin of the constant voltage charging chip U20 is electrically connected to the second terminal of capacitor C22. In this embodiment, the constant current circuit mainly consists of a constant current charging chip U2 (model LP28400ASPF). The resistor R36 is set to I = 5mV / R36 = 5mV / 0.12 = 42mA. The constant voltage circuit uses U20 (model SE8650) to output a constant 5V voltage. Through the constant current and constant voltage circuits, a stable 5V / 42mA charging power is provided to the battery, ensuring stable low-current charging operation of the system. The constant current charging circuit ensures that the battery is charged with a constant current in the initial stage of charging, improving charging efficiency and shortening charging time. The constant-voltage charging circuit maintains a constant voltage as the battery approaches full charge, preventing overcharging and extending battery life. By combining constant-current and constant-voltage charging, the battery charging process is optimized, improving battery efficiency and safety. The battery charging circuit design simplifies power management logic, reducing system complexity and cost. Stable charging performance and battery management enhance device reliability and user satisfaction.

[0106] Reference Figure 7 The doorbell detection circuit 800 includes a resistor R20, a diode D4, a switch SW1, and a capacitor C15. The first terminal of resistor R20 is electrically connected to the RST_KEY signal terminal and the first terminal of capacitor C15, respectively. The second terminal of resistor R20 is electrically connected to the first terminal of diode D4 and the corresponding terminal of switch SW1, respectively. The second terminals of capacitor C15 and diode D4 are both grounded. The doorbell detection circuit 800 mainly detects button presses, identifying whether a doorbell has been pressed by changing high or low voltage levels.

[0107] This embodiment of the solution can provide normal power to the entire system when the AC power input is from 10-24VAC, while charging the battery with a constant current, and can also support the functions of traditional mechanical doorbells or electronic doorbells; when the voltage is insufficient, it can charge the battery but not power the system.

[0108] 1. When no external power supply is connected to the traditional mechanical or electronic doorbell, the AC charging logic for the system is designed as follows:

[0109] When AC power is connected, the rectifier diode VD1 and the capacitors C1 (330µF), C30, C31, C32, C33, and C34 (5*10µF) at the back end of the input voltage regulator circuit convert the power into DC voltage. The hysteresis comparator of U19 (model AS331A) makes the AC_DC_DET signal output high or low level. This model will supply the MCU, and the MCU will use high and low logic to determine whether the input voltage is sufficient to control the conduction and shutdown of the high voltage DC-DC circuit U1 (model JW5121).

[0110] The reference voltage for U19 (model AS331A) is 5*R33 / (R29+R33)=5*2 / (2+3)=2V. The input judgment voltage is VIN*R25 / (R25+R24)=VIN*1 / (1+3.3)=0.2326*VIN. This is based on the derivation...

[0111] Where VH=2V, R24=3.3K, R25=1K, R41=1K, R42=4K, R26=10K, Vmin=10.23V, which is approximately 10.23 / 1.414 ≈ 7.23VAC in AC power supply.

[0112] Based on the derivation

[0113] Where VH=2V, R24=3.3K, R25=1K, R41=1K, R42=4K, R26=10K, Vmax=12.4V, which is approximately 12.4 / 1.414 ≈ 8.8VAC when converted to AC power.

[0114] The detection and judgment circuit of this solution supports a range of 7.23VAC-8.8VAC, which fully meets the design judgment requirements of 10VAC-24VAC as per product requirements.

[0115] When 10VAC is input, the AC voltage detection circuit outputs a high level. Upon receiving this high level, the MCU sets DC_VIN_CTRL high, and the high-voltage DC-DC output is normally 5V, supplying power to the external system. Simultaneously, due to the presence of the AC voltage, the constant current and constant voltage circuit delivers 5V / 42mA of power to the battery.

[0116] When 7VAC is input, the AC voltage detection circuit outputs a low level. Upon receiving this low level, the MCU sets DC_VIN_CTRL low, resulting in a 0V output for the high-voltage DC-DC converter. The AC power supply will not provide power to the downstream system, but it can still charge the battery. During this time, the system will not disconnect the battery charging circuit; the AC power supply will continue to charge the battery through a constant current and constant voltage circuit, ensuring that the battery is not completely depleted during use.

[0117] Reference Figures 8-7 When a traditional mechanical doorbell is connected to the system externally, this solution provides a doorbell control method for the aforementioned doorbell AC power supply circuit, including the following steps:

[0118] Step S1: Check the AC power supply connection. The AC power is converted to DC power through the AC rectification and protection circuit; ensure the AC power supply is correctly connected. The AC rectification and protection circuit converts AC power to DC power, providing a stable power foundation for subsequent circuits.

[0119] Step S2: The AC power supply status is detected by the AC judgment circuit, and the corresponding signal is output to the MCU;

[0120] The AC judgment circuit monitors the stability of the power supply, ensuring it remains within acceptable limits. If an unstable power supply is detected, it outputs a signal to the microcontroller (MCU) so the MCU can take appropriate action.

[0121] Step S3: The MCU controls the switching on and off of the high-voltage DC-DC circuit based on the signal from the AC judgment circuit; the MCU determines the power supply status based on the signal from the AC judgment circuit and controls the switching on and off of the high-voltage DC-DC circuit accordingly. When the power supply is stable, the DC-DC circuit is allowed to operate, converting the high-voltage DC power supply into a low-voltage power supply suitable for the system.

[0122] Step S4: When the AC power is short-circuited, the AC power is short-circuited through the short-circuit circuit to support the operation of the traditional mechanical doorbell; when the user operates the doorbell, the short-circuit circuit will short-circuit the AC power for a short time to support the operation of the traditional mechanical doorbell. This step ensures that the doorbell can work normally even when the power supply is unstable.

[0123] Step S5: When the AC power supply is stable, the battery charging circuit provides constant current and constant voltage charging to the lithium battery. This ensures safe and efficient charging of the battery, while extending its lifespan.

[0124] When AC power is connected to the system, it first undergoes preliminary processing through an AC rectification and protection circuit. This circuit includes primary protection, AC rectification, and input voltage regulation to ensure the stability and safety of the power supply.

[0125] The AC detection circuit monitors the state of the rectified power supply and outputs the result as a signal to the microcontroller (MCU). The MCU uses these signals to determine whether the power supply is stable and whether battery power should be activated. Based on the MCU's control signals, the high-voltage DC-DC circuit converts the rectified high-voltage DC power supply into a low-voltage DC power supply suitable for the doorbell system, ensuring power supply stability and reliable system operation.

[0126] When the AC power supply is stable, the battery charging circuit charges the lithium battery using a constant current and constant voltage method, ensuring that the battery is charged under safe and efficient conditions, thus extending the battery's lifespan.

[0127] When the AC power supply is shorted, the short-circuit circuit is activated, allowing the AC power supply to directly power the doorbell system while also supporting the operation of traditional mechanical doorbells.

[0128] The doorbell detection circuit monitors the status of the doorbell button. When the user presses the doorbell button, the circuit detects this action and triggers the MCU to process it. The MCU then controls the corresponding circuit to respond to the user's operation.

[0129] In the event of power instability or interruption, the MCU control system switches to battery power to ensure the doorbell system continues to operate. Simultaneously, the system activates a protection mechanism to prevent damage caused by power instability.

[0130] This solution employs multiple steps of detection and control, enabling the system to operate stably under varying power conditions and improving overall reliability. The system responds quickly to user actions, providing immediate feedback whether via a mechanical or electronic doorbell. The constant current / constant voltage charging method ensures effective battery charging, preventing overcharging and over-discharging, and extending battery life. The system's modular design simplifies maintenance and troubleshooting, reducing maintenance costs. Through precise power management and control, the system reduces energy loss and improves energy efficiency.

[0131] Furthermore, in step S1, the power supply is converted into DC voltage through rectifier diode VD1 and capacitors C1, C30, C31, C32, C33, and C34 of the input voltage regulator circuit; in step S2, the MCU detects the edge trigger signal of the RST_KEY pin of the doorbell detection circuit; in step S3, the MCU pulls the AC_DC_CTRL signal from high level to low level, turning off the high-voltage DC-DC circuit that supplies power to the downstream system; in step S3, after 300ms, the MC_TIME_CTRL signal of the AC short-circuit circuit turns on MOSFET Q1, realizing AC short-circuiting and turning on the external mechanical doorbell, and the AC supply to the downstream circuit will be continuously disconnected; in step S4, the AC_DC_CTRL signal terminal and the MC_TIME_CTRL signal terminal are continuously at low level for 1000ms and then released to high level, the AC only charges the battery and does not supply power to the downstream, and after 1000ms, the normal power supply and charging state is restored.

[0132] This solution uses circuit control to turn on MOSFET Q1, disconnecting the entire downstream system and enabling the external mechanical doorbell to operate. To avoid repetitive actions and for anti-jitter function, the system is set to only activate once per 1 second, resulting in a single "ding-dong" sound from the doorbell. During this control process, the system shuts off all AC power to ensure its safety and reliability. With AC power off, the system is then powered by a battery or other electrical source.

[0133] As can be seen from the above embodiments, this utility model can adapt to a wide range of AC power input (10-24VAC), and can ensure the normal operation of the doorbell even under conditions of unstable or poor power supply, thereby improving the applicability and reliability of the system. It can maintain power supply for multiple power systems, and there is no need to charge the battery separately after connecting to AC. Through efficient AC rectification and protection circuits and DC-DC circuits, the system can convert unstable AC power into stable low-voltage DC power, ensuring that the doorbell system can operate stably under various power conditions.

[0134] Efficient battery charging management: The battery charging circuit adopts a constant current and constant voltage charging method to ensure that the lithium battery is neither overcharged nor undercharged during the charging process, thereby improving the battery's lifespan and charging efficiency.

[0135] Compatible with traditional and modern doorbells: Through the design of the short-circuit circuit, the system can support the operation of traditional mechanical doorbells when the AC power is shorted, while maintaining compatibility with modern electronic doorbells.

[0136] Fast-response doorbell detection: The doorbell detection circuit can quickly respond to the user's ringing action and promptly notify the MCU for processing, ensuring a fast doorbell response and improving the user experience.

[0137] Optimized power management logic: The MCU intelligently controls the switching on and off of the high-voltage DC-DC circuit based on the signal from the AC judgment circuit, thus optimizing the power management logic and reducing unnecessary energy consumption.

[0138] Enhanced system safety: The AC detection circuit can promptly output a signal to the MCU when abnormal power conditions are detected, triggering protection measures to protect the entire doorbell system from damage.

[0139] This invention integrates AC rectification and protection circuits, short-circuit circuits, AC judgment circuits, DC-DC circuits, battery charging circuits, and doorbell detection circuits. This design simplifies the circuit structure, reduces the number of components, and lowers costs and complexity.

[0140] Efficient battery management: The battery charging circuit adopts a constant current and constant voltage charging method, which effectively manages the battery charging process, extends the battery life, and ensures that the battery can provide a stable power supply when needed.

[0141] Supports traditional doorbell operation: Through the design of the short-circuit circuit, the system can support the operation of traditional mechanical doorbells when the AC power is shorted, maintaining compatibility with the old system.

[0142] Improved user experience: The system can automatically switch to battery power when the power supply is unstable or interrupted, ensuring the doorbell's continuous response and thus improving the user experience.

[0143] Reliable power supply judgment and protection: The AC judgment circuit can accurately monitor the power supply status and output a signal to the MCU in a timely manner when an unstable power supply is detected, triggering protection measures to protect the system from damage.

[0144] Easy to maintain and upgrade: The modular design of the system makes maintenance and upgrades simpler, reduces maintenance costs, and improves system scalability.

[0145] The above description is only a preferred embodiment of the present utility model and does not limit the patent scope of the present utility model. All equivalent structural transformations made under the inventive concept of the present utility model using the contents of the present utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present utility model.

Claims

1. A doorbell AC power supply circuit, characterized in that, include: Control unit, AC interface, AC rectification and protection circuit, short circuit circuit, AC judgment circuit, DC-DC circuit, battery charging circuit, doorbell detection circuit; The corresponding terminals of the control unit are electrically connected to the corresponding terminals of the short-circuit circuit, AC judgment circuit, DC-DC circuit, and doorbell detection circuit, respectively. The corresponding terminals of the AC rectification and protection circuit are electrically connected to the corresponding terminals of the AC interface, short circuit circuit, AC judgment circuit, and DC-DC circuit, respectively. The corresponding terminal of the DC-DC circuit is also connected to the battery charging circuit. The AC interface is used for AC power connection; The AC rectification and protection circuit is used to convert the input AC power supply into a stable DC power supply. The short-circuit circuit is used to short-circuit the AC power supply to support the doorbell ringing operation; The AC detection circuit is used to detect the AC power supply status; The DC-DC circuit is used to convert the high-voltage power input from the AC rectification and protection circuit into a low-voltage usable power supply. The battery charging circuit is used to convert available power into constant current and constant voltage power for use by the lithium battery. The doorbell detection circuit is used to detect doorbell button commands.

2. The doorbell AC power supply circuit according to claim 1, characterized in that, The doorbell AC power supply circuit also includes a connector, the corresponding ends of which are electrically connected to the corresponding ends of the DC-DC circuit and the battery charging circuit, respectively; the control unit is set as an MCU.

3. The doorbell AC power supply circuit according to claim 2, characterized in that, The AC rectification and protection circuit consists of an AC input access and protection circuit, an AC rectification circuit, and an input voltage regulator circuit. The AC input access and protection circuit includes a primary protection circuit, a diode protection circuit, and a common-mode protection circuit. The primary protection circuit includes a fuse F1 and a varistor RV1. The diode protection circuit consists of a fuse F2, a diode ESD1, a diode D11, and a diode ESD2. The common-mode protection circuit consists of a ferrite bead R1, a ferrite bead R2, and a common-mode inductor L5. The AC rectifier circuit includes a rectifier diode VD1; The input voltage regulator circuit includes capacitors C1, C30, C31, C32, C33, and C34. The first end of the fuse F1 is connected to the negative input terminal of the AC power supply, and the second end of the fuse F1 is electrically connected to the first end of the varistor RV1 and the second pin of the rectifier diode VD1. The second end of the varistor RV1 is electrically connected to the positive input terminal of the AC power supply and the first pin of the rectifier diode VD1. The third pin of the rectifier diode VD1 is electrically connected to the first terminal of diode ESD1 and fuse F2, respectively, and the fourth pin of the rectifier diode VD1 is electrically connected to the second terminal of diode ESD1 and the first terminal of diode D11, respectively. The second end of the fuse F2 is electrically connected to the first end of the ferrite bead R1 and the fourth pin of the common mode inductor L5, respectively; the second end of the diode D11 is electrically connected to the first end of the ferrite bead R2 and the first pin of the common mode inductor L5, respectively. The second end of the ferrite bead R1 is electrically connected to the third pin of the common mode inductor L5, capacitor C1, diode ESD2, capacitor C30, capacitor C31, capacitor C32, capacitor C33, and capacitor C34, respectively; the second end of the ferrite bead R2 is electrically connected to the second pin of the common mode inductor L5, capacitor C1, diode ESD2, capacitor C30, capacitor C31, capacitor C32, capacitor C33, and capacitor C34, respectively.

4. The doorbell AC power supply circuit according to claim 3, characterized in that, The DC-DC circuit includes a power chip U1, resistors R4, R5, R7, R9, R11, R47, capacitors C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, diode D3, and inductor L3. The first pin of the power chip U1 is electrically connected to the first end of capacitor C2, diode D3, and inductor L3 respectively. The second end of capacitor C2 is electrically connected to the eighth pin of power chip U1. The second end of diode D3 is grounded. The second end of inductor L3 is electrically connected to the first end of capacitor C4, capacitor C7, capacitor C3, resistor R5, and capacitor C8 respectively. The fourth pin of the power chip U1 is electrically connected to the first end of resistor R7, the second end of resistor R5, and the second end of capacitor C8, respectively, and the second end of resistor R7 is grounded. The third pin of the power chip U1 is electrically connected to the first end of capacitor C10, capacitor C11 and resistor R11 respectively. The second ends of capacitor C10 and capacitor C11 are grounded, and the second end of resistor R11 is electrically connected to the input voltage AC_DC_5V_F terminal. The 7th pin of the power chip U1 is electrically connected to the first terminals of resistor R4, capacitor C6, and capacitor C5 respectively. The second terminal of resistor R4 is electrically connected to the DC_VIN_CTRL signal terminal, the first terminal of resistor R47, the 2nd pin of power chip U1, and the first terminal of capacitor C9 respectively. The second terminal of capacitor C9 is electrically connected to the second terminal of resistor R47 and grounded. The second terminals of capacitors C6 and C5 are both grounded. The 6th pin of power chip U1 is grounded through resistor R9.

5. The doorbell AC power supply circuit according to claim 4, characterized in that, The short-circuit circuit includes diode D6, diode D10, resistor R3, resistor R12, resistor R39, resistor R53, MOSFET Q1, and MOSFET Q3. The drain of MOSFET Q1 is electrically connected to the first terminal of resistor R3 and diode D10, respectively. The gate of MOSFET Q1 is electrically connected to the first terminal of resistor R39, resistor R3, and the second terminal of diode D10 via resistor R53. The second terminal of resistor R39 is electrically connected to the source of MOSFET Q3. The gate of MOSFET Q3 is electrically connected to the first terminal of resistor R12 and diode D6, respectively. The drain of MOSFET Q1 is electrically connected to the second terminal of resistor R12. The second terminal of diode D6 is connected to the MC_TIME_CTRL signal terminal.

6. The doorbell AC power supply circuit according to claim 5, characterized in that, The AC judgment circuit includes a comparator circuit and a voltage regulator circuit electrically connected to the corresponding terminal of the comparator circuit. The voltage regulator circuit includes capacitor C17, capacitor C18, resistor R54, and voltage regulator chip U8. The first pin of voltage regulator chip U8 is electrically connected to the first terminals of capacitor C17 and capacitor C18, the second pin of voltage regulator chip U8 is electrically connected to the second terminal of capacitor C17, and the third pin of voltage regulator chip U8 is electrically connected to the first terminal of resistor R54, the second terminal of capacitor C18, and the corresponding terminal of comparator circuit. The comparator circuit includes a comparator chip U19, resistors R24, R25, R26, R27, R29, R33, R41, R42, R51, capacitor C16, and capacitor C19. The first pin of the comparator chip U19 is electrically connected to the first terminals of resistors R29, R33, and capacitor C16, respectively. The second terminal of resistor R33 is electrically connected to the second terminal of capacitor C16 and grounded. The third pin of the comparator chip U19 is electrically connected to the first terminals of resistors R41 and R42, respectively. The second terminal of resistor R41 is electrically connected to the first terminals of resistors R25, C19, and R24, respectively. The second terminal of resistor R25 is electrically connected to the second pin of comparator chip U19 and the second terminal of capacitor C19, respectively. The second terminal of resistor R42 is electrically connected to the fourth pin of comparator chip U19, the first terminals of resistors R26 and R51, respectively. The second terminal of resistor R26 is electrically connected to the fifth pin of comparator chip U19, and the second terminal of resistor R51 is grounded through resistor R27.

7. The doorbell AC power supply circuit according to claim 6, characterized in that, The battery charging circuit includes a charging constant current circuit and a constant voltage measurement circuit. The constant current charging circuit includes a constant current charging chip U2, resistors R34, R35, R36, and R37, a diode D9, a MOSFET Q6, capacitors C22, C23, C24, C25, and C26, and an inductor L4. The first pin of the constant current charging chip U2 is electrically connected to the first terminals of resistors R34, inductor L4, and capacitor C22. The second terminal of capacitor C22 is electrically connected to the first terminal of resistor R35 and the ninth pin of the constant current charging chip U2. The second terminal of resistor R35 is electrically connected to the second terminal of resistor R34 and the fifth pin of the constant current charging chip U2. The second terminal of inductor L4 is electrically connected to the third pin of the constant current charging chip U2 and the first terminal of diode D9. The second terminal of diode D9 is electrically connected to… The first terminal of capacitor C23 is electrically connected to the drain of MOSFET Q6, and the second terminal of capacitor C23 is grounded. The gate of MOSFET Q6 is electrically connected to pin 8 of constant current charging chip U2 and the first terminal of capacitor C24, and the second terminal of capacitor C24 is grounded. The source of MOSFET Q6 is electrically connected to pin 6 of constant current charging chip U2 and the first terminal of resistor R36. The second terminal of resistor R36 is electrically connected to pin 7 of constant current charging chip U2 and the first terminal of capacitor C25, and the second terminal of capacitor C25 is grounded. The second pin of constant current charging chip U2 is electrically connected to the first terminal of resistor R37 and capacitor C26. The second terminal of resistor R37 is electrically connected to pin 4 of constant current charging chip U2, and the second terminal of capacitor C26 is grounded. The constant voltage measurement circuit includes a constant voltage charging chip U20, capacitor C20, capacitor C21, and capacitor C36; the first pin of the constant voltage charging chip U20 is electrically connected to the first terminals of capacitors C20, C21, and C36 respectively; the second pin of the constant voltage charging chip U20 is electrically connected to the second terminals of capacitors C20 and C36 respectively; and the third pin of the constant voltage charging chip U20 is electrically connected to the second terminal of capacitor C22.

8. The doorbell AC power supply circuit according to claim 7, characterized in that, The doorbell detection circuit includes a resistor R20, a diode D4, a switch SW1, and a capacitor C15. The first end of the resistor R20 is electrically connected to the RST_KEY signal terminal and the first end of the capacitor C15, respectively. The second end of the resistor R20 is electrically connected to the first end of the diode D4 and the corresponding end of the switch SW1, respectively. The second ends of the capacitor C15 and the diode D4 are both grounded.

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