Backup battery switching circuit and metering instrument

Abstract

The utility model is applicable to the technical field of electronic information, and relates to a backup battery switching circuit and a metering instrument, which comprise a main power supply sampling and power supply circuit, a meter reading battery sampling and power supply circuit, a clock battery power supply circuit, a first LDO (Low Dropout Regulator) circuit, a second LDO circuit, a power flow control circuit and an MCU (Microprogrammed Control Unit). The device is simple in structure and convenient to work, can switch the clock battery to the low-power-consumption operation power supply of the MCU when the meter reading battery is under-voltage or is taken off to cause power failure, enables the cover opening detection function to be effective, and closes the clock battery to provide a channel for the low-power-consumption operation of the MCU and the power supply of the cover opening detection circuit after the meter is operated for a preset time length, so that the safety of the meter is improved. The electric quantity of the clock battery is effectively saved, and the influence on reliable operation of the real-time clock circuit is small.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the electronic information technical field, especially relate to a backup battery switching circuit and metering instrument. BACKGROUND

[0002] Now the three-phase meter product of the national south net market has clock battery and meter battery, the clock battery is specially given real-time clock circuit power supply, the meter battery gives the low power consumption operation power supply of MCU, can support the function such as key display, infrared reading, cover detection.Generally, the clock battery is marked voltage 3.6V, is welded on the circuit board, and can not be replaced in the field, and the meter battery is marked voltage 6V, and can be replaced in the field.The national grid updates technical specification, and requires that the electric energy meter stops power in the case of meter battery under voltage or being taken off, and still can record the cover opening event after stopping power for two days, the cover opening detection function is invalid, the meter can only maintain the clock operation, can not supply the low power consumption operation and cover opening detection circuit of MCU, and can not close the low power consumption operation and cover opening detection circuit of MCU after the clock battery supplies the low power consumption operation and cover opening detection circuit of MCU for a period of time.

[0003] The patent with publication number CN106532908B provides a double-core electric energy meter and a power supply control method thereof.The double-core electric energy meter includes a metering core for realizing electric energy metering function, a management core for realizing non-electric energy metering management function, and a power supply management control module for realizing independent power supply to the metering core and the management core.The power supply management control module is composed of a main power supply, a clock battery and a metering battery, and the control method is that when the main power supply is powered on, all power supplies are provided by the main power supply, and the metering core is powered by an independent power supply branch;when the main power supply is powered off, the clock battery provides power supply to the clock circuit RTC of the metering core, and the metering battery provides power supply to the management core;when the clock battery is replaced, the super capacitor temporarily provides power supply to the clock circuit RTC in the metering core.This patent also uses the clock battery to supply power to the clock circuit, and cannot be used for cover opening detection circuit after power failure, which has the same disadvantages as the prior art.

[0004] Therefore, how to make the meter stop power in the case of meter battery under voltage or being taken off, and make the clock battery be used for the low power consumption operation and cover opening detection circuit power supply of MCU, so that the cover opening detection function is effective, is a problem to be solved by the personnel in the technical field. Utility model content

[0005] In view of the deficiencies of the prior art, the utility model discloses a backup battery switching circuit to solve the problem that the clock battery cannot supply the low power consumption operation of MCU and the cover opening detection circuit in the prior art, and the clock battery cannot provide the power supply channel for the low power consumption operation of MCU and the cover opening detection circuit after a period of time of supplying the low power consumption operation of MCU and the cover opening detection circuit, and further provides a metering instrument.

[0006] In order to solve the above technical problems, the utility model adopts the following technical scheme:

[0007] Firstly, the utility model provides a backup battery switching circuit, which comprises a mains sampling and power supply circuit, a meter battery sampling and power supply circuit, a clock battery power supply circuit, a first LDO circuit, a second LDO circuit, a power flow control circuit and an MCU, the input of the mains sampling and power supply circuit is connected with a mains VHH, the output VBB_IN is respectively connected with the output of the meter battery sampling and power supply circuit, the input of the first LDO circuit and the input of the second LDO circuit, the output VRTC of the clock battery power supply circuit is connected with a real-time clock circuit power VRTC, the power pin of the power flow control circuit is connected with the real-time clock circuit power VRTC, the other end of the power flow control circuit is connected with the output VDD of the first LDO circuit, the output end VBB of the second LDO circuit is connected with the power pin of the MCU, the voltage division sampling signal output LVD of the mains sampling and power supply circuit is connected with the power-down detection port LVDIN of the MCU, the voltage division sampling signal output VB_6V of the meter battery sampling and power supply circuit is connected with the analog port ADCIN of the MCU, and the controlled end BAT_CTRL of the power flow control circuit is connected with an IO port of the MCU.

[0008] Further, the mains sampling and power supply circuit comprises a resistor R1, a resistor R2, a capacitor C1 and a diode D2, one end of the resistor R1 and the anode of the diode D2 are connected with the mains input VHH, the other end of the resistor R1 is connected with one end of the resistor R2 and one end of the capacitor C1, and then connected with the power-down detection port LVDIN of the MCU, the other end of the resistor R2 and the other end of the capacitor C1 are both connected with the power supply ground, and the cathode of the diode D2 is connected with the output of the meter battery sampling and power supply circuit as the output VBB_IN, and also connected with the input of the first LDO circuit and the input of the second LDO circuit.

[0009] Further, the meter battery sampling and power supply circuit comprises a resistor R4, a resistor R5, a resistor R6, a capacitor C2, a meter battery BAT2 and a diode D3, a negative electrode of the meter battery BAT2 is connected to a power supply ground, a positive electrode of the meter battery BAT2 is connected to one end of the resistor R6, the other end of the resistor R6 is connected to one end of the resistor R4 and an anode of the diode D3 respectively, the other end of the resistor R4 is connected to one end of the resistor R5 and one end of the capacitor C2, and then connected to an analog port ADCIN of the MCU, the other end of the resistor R5 and the other end of the capacitor C2 are both connected to the power supply ground, a cathode of the diode D3 is connected to an output VBB_IN of the main power supply sampling and power supply circuit, and also connected to an input of the first LDO circuit and an input of the second LDO circuit.

[0010] Further, the clock battery power supply circuit comprises a clock battery BAT1, a resistor R3 and a diode D1, a negative electrode of the clock battery BAT1 is connected to a power supply ground, a positive electrode of the clock battery BAT1 is connected to one end of the resistor R3, the other end of the resistor R3 is connected to an anode of the diode D1, and a cathode of the diode D1 is connected to a real-time clock circuit power supply VRTC, and also connected to the power supply current flow control circuit.

[0011] Further, the power supply current flow control circuit comprises a diode D4, a diode D5 and a controlled switch K, one end of the controlled switch K is connected to a cathode of the diode D4, and then connected to VRTC, the other end of the controlled switch K is connected to an anode of the diode D5, a controlled end BAT_CTRL of the controlled switch K is connected to an IO port of the MCU, and an anode of the diode D4 is connected to a cathode of the diode D5, and then connected to an output VDD of the first LDO circuit.

[0012] Further, the first LDO circuit comprises a voltage stabilizing chip U1, a capacitor C4 and a capacitor C6, a power supply input pin of the voltage stabilizing chip U1 is connected to one end of the capacitor C4, and then connected to VBB_IN, a power supply output pin of the voltage stabilizing chip U1 is connected to one end of the capacitor C6, and then connected to the power supply current flow control circuit as an output VDD, and a grounding pin of the voltage stabilizing chip U1, the other end of the capacitor C4 and the other end of the capacitor C6 are all connected to the power supply ground.

[0013] Further, the second LDO circuit comprises a voltage stabilizing chip U2, a capacitor C5 and a capacitor C7, a power input pin of the voltage stabilizing chip U2 is connected with one end of the capacitor C5 and then connected with VBB_IN, a power output pin of the voltage stabilizing chip U2 is connected with one end of the capacitor C7 and then connected with a power pin VCC of the MCU, a cover opening detection circuit power supply VBB and other low-power circuit power supplies as an output VBB, and a grounding pin of the voltage stabilizing chip U2, the other end of the capacitor C5 and the other end of the capacitor C7 are all connected with a power ground.

[0014] In a second aspect, the utility model provides a kind of metering instrument, comprising backup battery switching circuit described above.

[0015] Compared with prior art, the backup battery switching circuit and metering instrument provided by the utility model have at least the following beneficial effects:

[0016] In prior art, clock battery cannot supply low-power operation of MCU and cover opening detection circuit, and cannot close the power supply channel of clock battery to low-power operation of MCU and cover opening detection circuit after a period of time of supplying low-power operation of MCU and cover opening detection circuit by clock battery.The utility model has simple structure and convenient operation, can supply power to low-power operation of MCU and cover opening detection circuit by clock battery when metering battery is under voltage or is removed and power is off, make cover opening detection function effective, and close clock battery after running preset length, supply power to low-power operation of MCU and cover opening detection circuit to provide channel, save clock battery power, and have little influence on reliable operation of real-time clock circuit. BRIEF DESCRIPTION OF DRAWINGS

[0017] To more clearly illustrate the scheme of the utility model, the following will introduce the drawings needed in the embodiment description, and obviously, the drawings in the following description are some embodiments of the utility model, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0018] Figure 1 A circuit diagram of backup battery switching circuit provided for the embodiment of the utility model is shown in the following figure:

[0019] Figure 2 A power flow control circuit diagram of backup battery switching circuit provided for the embodiment of the utility model is shown in the following figure:

[0020] Figure 3 A circuit diagram of backup battery switching circuit provided for another embodiment of the utility model is shown in the following figure:

[0021] Figure 4The utility model provides a kind of circuit diagram of backup battery switching circuit for another embodiment of the utility model. DETAILED DESCRIPTION

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used in the specification herein is for describing particular embodiments only and is not intended to be limiting of the application, for example, the terms "length", "width", "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like specify relative positions according to the orientations shown in the drawings and are for convenience not for limiting the present application.

[0023] The terms "include", "has", "having" and any variations thereof in the specification and claims of the utility model and the above description of drawings are intended to cover the inclusion not the exclusion; the terms "first", "second" and the like in the specification and claims of the utility model or the above description of drawings are used to distinguish different objects and are not used to describe a particular order. In the specification and claims of the utility model and the above description of drawings, when an element is referred to as "fixed to" or "mounted to" or "set to" or "connected to" another element, it can be directly or indirectly on the other element. For example, when an element is referred to as "connected to" another element, it can be directly or indirectly connected to the other element.

[0024] In addition, the reference herein to "embodiment" means that the specific features, structures or characteristics described in connection with the embodiment can be included in at least one embodiment of the utility model. The appearance of this phrase in various places in the specification does not necessarily mean the same embodiment, nor is it an independent or alternative embodiment to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0025] The utility model embodiment provides a kind of backup battery switching circuit, it is applied to the process of opening cover detection function realization after the power failure of metering instrument, the backup battery switching circuit includes:

[0026] The main power supply sampling and power supply circuit, the meter battery sampling and power supply circuit, the clock battery power supply circuit, the first LDO circuit, the second LDO circuit, the power flow control circuit and the MCU; the main power supply sampling and power supply circuit is connected with the main power supply VHH, and the output VBB_IN is connected with the output of the meter battery sampling and power supply circuit, the input of the first LDO circuit and the input of the second LDO circuit respectively, the output VRTC of the clock battery power supply circuit is connected with the real-time clock circuit power supply VRTC, the power supply pin of the power flow control circuit is connected with the real-time clock circuit power supply VRTC, the other end of the power flow control circuit is connected with the output VDD of the first LDO circuit, the output end VBB of the second LDO circuit is connected with the power supply pin of the MCU, the voltage division sampling signal output LVD of the main power supply sampling and power supply circuit is connected with the power-down detection port LVDIN of the MCU, the voltage division sampling signal output VB_6V of the meter battery sampling and power supply circuit is connected with the analog port ADCIN of the MCU, and the controlled end BAT_CTRL of the power flow control circuit is connected with an IO port of the MCU.

[0027] The utility model discloses simple structure, convenient work can make the meter in the meter battery under voltage or be taken off and power off condition, will clock battery switch MCU's low -power consumption operation power supply, makes the uncapping detection function effective, and after running preset length, close clock battery and give MCU's low -power consumption operation and uncapping detection circuit power supply provides the passage, effectively saves clock battery electric quantity, and the reliable operation influence of real -time clock circuit is little.

[0028] In order to make the personnel in the technical field better understand the utility model scheme, below will combine the drawings, and the technical scheme in the utility model embodiment is clearly and completely described.

[0029] The utility model embodiment provides a kind of backup battery switching circuit, applied to the uncapping detection function implementation process of metering instrument power failure, combines Figure 1 With Figure 2 In the embodiment, the backup battery switching circuit includes:

[0030] The main power supply sampling and power supply circuit, the meter battery sampling and power supply circuit, the clock battery power supply circuit, the first LDO circuit, the second LDO circuit, the power flow control circuit and the MCU; the main power supply sampling and power supply circuit is connected with the main power supply VHH in input, and the output VBB_IN is connected with the output of the meter battery sampling and power supply circuit, the input of the first LDO circuit and the input of the second LDO circuit respectively, the output VRTC of the clock battery power supply circuit is connected with the real-time clock circuit power supply VRTC, the power supply pin of the power flow control circuit is connected with the real-time clock circuit power supply VRTC, the other end of the power flow control circuit is connected with the output VDD of the first LDO circuit, the output end VBB of the second LDO circuit is connected with the power supply pin of the MCU, the voltage division sampling signal output LVD of the main power supply sampling and power supply circuit is connected with the power-down detection port LVDIN of the MCU, the voltage division sampling signal output VB_6V of the meter battery sampling and power supply circuit is connected with the analog port ADCIN of the MCU, and the controlled end BAT_CTRL of the power flow control circuit is connected with an IO port of the MCU. Through the backup battery switching circuit provided in the embodiment of the utility model, under the condition that the MCU does not participate in the control, the MCU, VRTC, cover detection circuit and other low-power circuits are preferentially powered by the main power supply VHH, when the main power supply VHH has no electricity, it is automatically switched to the meter battery BAT2 with a nominal voltage of 6V for power supply, the clock battery power consumption is not consumed in the above two cases, when the voltage of the meter battery BAT2 is lower than the voltage of the clock battery BAT1 or the meter battery BAT2 is not installed, the clock battery with a nominal voltage of 3.6V is used to power VRTC, and the MCU, cover detection circuit and other low-power circuits are not powered and do not run.

[0031] Further, in the embodiment, the main power supply sampling and power supply circuit comprises a resistor R1, a resistor R2, a capacitor C1 and a diode D2, one end of the resistor R1 and an anode of the diode D2 are connected with the main power supply input VHH, the other end of the resistor R1 is connected with one end of the resistor R2 and one end of the capacitor C1, and then connected with the power-down detection port LVDIN of the MCU, the other end of the resistor R2 and the other end of the capacitor C1 are both connected with the power supply ground, and a cathode of the diode D2 is connected with the output of the meter battery sampling and power supply circuit as the output VBB_IN, and also connected with the input of the first LDO circuit and the input of the second LDO circuit.

[0032] Further, in the embodiment, the meter battery sampling and power supply circuit includes resistor R4, resistor R5, resistor R6, capacitor C2, meter battery BAT2, and diode D3. The negative electrode of the meter battery BAT2 is connected to the power supply ground, and the positive electrode is connected to one end of the resistor R6. The other end of the resistor R6 is connected to one end of the resistor R4 and the anode of the diode D3, respectively. The other end of the resistor R4 is connected to one end of the resistor R5 and one end of the capacitor C2, and then connected to the analog port ADCIN of the MCU. The other end of the resistor R5 and the other end of the capacitor C2 are both connected to the power supply ground. The cathode of the diode D3 is connected to the output VBB_IN of the main power supply sampling and power supply circuit, and also connected to the input of the first LDO circuit and the input of the second LDO circuit.

[0033] Further, in the embodiment, the clock battery power supply circuit includes clock battery BAT1, resistor R3, and diode D1. The negative electrode of the clock battery BAT1 is connected to the power supply ground, and the positive electrode is connected to one end of the resistor R3. The other end of the resistor R3 is connected to the anode of the diode D1. The cathode of the diode D1 is connected to the real-time clock circuit power supply VRTC, and also connected to the power supply current control circuit.

[0034] Further, in the embodiment, as shown in Figure 1 the power supply current control circuit includes diode D4, diode D5, and controlled switch K. One end of the controlled switch K is connected to the cathode of the diode D4, and then connected to VRTC. The other end of the controlled switch K is connected to the anode of the diode D5. The controlled end BAT_CTRL of the controlled switch K is connected to one IO port of the MCU. The anode of the diode D4 is connected to the cathode of the diode D5, and then connected to the output VDD of the first LDO circuit. After the MCU participates in control, the controlled switch K can be turned on as appropriate, so that VRTC supplies power to the output VDD of the first LDO circuit through the controlled switch K and the diode D5. Then, the low-power supply VBB_IN is supplied with power through the MOS inside the voltage stabilizing chip U1, and then the MCU, the cover detection circuit, and other low-power circuits are supplied with power through the second LDO circuit.

[0035] In another embodiment, as shown in Figure 2As shown, the power flow control circuit includes diodes D4 and D5 and a controlled switch K. One end of the controlled switch K is connected to the cathode of diode D4 and then to VRTC. The other end of the controlled switch K is connected to the anode of diode D5. The controlled terminal BAT_CTRL of the controlled switch K is connected to an I / O port of the MCU. The anode of diode D4 is connected to the output VDD of the first LDO circuit, and the cathode of diode D5 is connected to the low-power power supply VBB_IN. When the MCU turns on the controlled switch K, VRTC supplies power to the low-power power supply VBB_IN through the controlled switch K and diode D5, and then supplies power to the MCU, the cover-opening detection circuit, and other low-power circuits through the second LDO circuit.

[0036] In another embodiment, such as Figure 3 As shown, the power flow control circuit includes diodes D4 and D5, buffer U3, and resistor R7. The power supply pin of buffer U3 is connected to VRTC, and the output pin of buffer U3 is connected to the anode of diode D5. The enable pin of buffer U3, the signal input pin of buffer U3, and one end of resistor R7 are connected to an IO port BAT_CTRL of the MCU. The ground pin of buffer U3 and the other end of resistor R7 are both connected to the power ground. The anode of diode D4 and the cathode of diode D5 are connected to the output VDD of the first LDO circuit, and the cathode of diode D4 is connected to VRTC.

[0037] In another embodiment, such as Figure 4 As shown, the power flow control circuit includes diodes D4 and D5, PMOS transistor Q1, NMOS transistor Q2, resistors R7 and R8. The source of PMOS transistor Q1 is connected to one end of resistor R8 and the cathode of diode D4, and then connected to VRTC. The anode of diode D4 is connected to the output VDD of the first LDO circuit. The other end of resistor R8 is connected to the gate of PMOS transistor Q1 and the drain of NMOS transistor Q2. The source of PMOS transistor Q1 is connected to the anode of diode D5. The cathode of diode D5 is connected to VBB_IN as an output. The source of NMOS transistor Q2 is connected to the power supply ground. The gate of NMOS transistor Q2 is connected to one end of resistor R7 and then connected to an IO port BAT_CTRL of the MCU. The other end of resistor R7 is connected to the power supply ground.

[0038] Furthermore, in this embodiment, the first LDO circuit includes a voltage regulator chip U1, a capacitor C4, and a capacitor C6. The power input pin of the voltage regulator chip U1 is connected to one end of the capacitor C4, and then connected to VBB_IN. The power output pin of the voltage regulator chip U1 is connected to one end of the capacitor C6 and then serves as the output VDD connected to the power flow control circuit. The ground pin of the voltage regulator chip U1, the other end of the capacitor C4, and the other end of the capacitor C6 are all connected to the power ground.

[0039] Further, in the embodiment, the second LDO circuit includes a voltage stabilizing chip U2, a capacitor C5 and a capacitor C7, a power input pin of the voltage stabilizing chip U2 is connected with one end of the capacitor C5 and then connected with VBB_IN, a power output pin of the voltage stabilizing chip U2 is connected with one end of the capacitor C7 and then connected with a power pin VCC of the MCU, a cover opening detection circuit power VBB and other low-power circuit power, a grounding pin of the voltage stabilizing chip U2, the other end of the capacitor C5 and the other end of the capacitor C7 are all connected with a power ground.

[0040] The utility model embodiment further provides a metering instrument, including the backup battery switching circuit of above-mentioned embodiment.

[0041] Compared with the prior art, the backup battery switching circuit and the metering instrument described in the above embodiment can supply power to the low-power operation and the cover opening detection circuit of the MCU by switching the clock battery, can make the cover opening detection function effective, and can close the clock battery to supply power to the low-power operation and the cover opening detection circuit of the MCU after running for a preset time, provide a power supply channel for the low-power operation and the cover opening detection circuit of the MCU, save the clock battery power, and have little effect on the reliable operation of the real-time clock circuit.

[0042] Obviously, the above-described embodiments are only the preferred embodiments of the utility model, not all the embodiments, and the drawings show the preferred embodiments of the utility model, but do not limit the patent range of the utility model. The utility model can be realized in many different forms, and conversely, the purpose of providing these embodiments is to make the understanding of the disclosure of the utility model more thorough and comprehensive. Although the utility model is described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing specific embodiments or make equivalent substitutions for some technical features. Any equivalent structure made by using the contents of the utility model specification and drawings, directly or indirectly applied to other related technical fields, is also within the patent protection range of the utility model.

Claims

1. A backup battery switching circuit, characterized by, The utility model relates to a kind of real-time clock circuit, including: Main power supply sampling and power supply circuit, meter battery sampling and power supply circuit, clock battery power supply circuit, first LDO circuit, second LDO circuit, power flow control circuit and MCU; The output VBB_IN of the main power supply sampling and power supply circuit is connected with the output of the meter battery sampling and power supply circuit, the input of the first LDO circuit and the input of the second LDO circuit respectively, the output VRTC of the clock battery power supply circuit is connected with the real-time clock circuit power supply VRTC, the power supply pin of the power flow control circuit is connected with the real-time clock circuit power supply VRTC, the other end of the power flow control circuit is connected with the output VDD of the first LDO circuit, the output end VBB of the second LDO circuit is connected with the power supply pin of the MCU, the voltage division sampling signal output LVD of the main power supply sampling and power supply circuit is connected with the power-down detection port LVDIN of the MCU, the voltage division sampling signal output VB_6V of the meter battery sampling and power supply circuit is connected with the analog port ADCIN of the MCU, and the controlled end BAT_CTRL of the power flow control circuit is connected with one IO port of the MCU.

2. A backup battery switching circuit according to claim 1, characterized in that The main power supply sampling and power supply circuit includes resistance R1, resistance R2, capacitor C1 and diode D2, one end of the resistance R1 and the anode of the diode D2 are connected with the main power supply input VHH, the other end of the resistance R1 is connected with one end of the resistance R2 and one end of the capacitor C1, and then is connected with the power-down detection port LVDIN of the MCU, the other end of the resistance R2 and the other end of the capacitor C1 are connected with power supply ground, and the cathode of the diode D2 is connected with the output of the meter battery sampling and power supply circuit as output VBB_IN, and is also connected with the input of the first LDO circuit and the input of the second LDO circuit.

3. A backup battery switching circuit according to claim 1, wherein The meter battery sampling and power supply circuit includes resistance R4, resistance R5, resistance R6, capacitor C2, meter battery BAT2 and diode D3, the negative electrode of the meter battery BAT2 is connected with power supply ground, the positive electrode is connected with one end of the resistance R6, the other end of the resistance R6 is connected with one end of the resistance R4 and the anode of the diode D3 respectively, the other end of the resistance R4 is connected with one end of the resistance R5 and one end of the capacitor C2, and then is connected with the analog port ADCIN of the MCU, the other end of the resistance R5 and the other end of the capacitor C2 are connected with power supply ground, and the cathode of the diode D3 is connected with the output of the main power supply sampling and power supply circuit as output VBB_IN, and is also connected with the input of the first LDO circuit and the input of the second LDO circuit.

4. A backup battery switching circuit according to claim 1, wherein The clock battery power supply circuit comprises a clock battery BAT1, a resistor R3 and a diode D1, a negative electrode of the clock battery BAT1 is connected to a power supply ground, a positive electrode is connected to one end of the resistor R3, the other end of the resistor R3 is connected to an anode of the diode D1, and a cathode of the diode D1 is connected to a real-time clock circuit power supply VRTC as an output VRTC, and is also connected to the power supply current flow control circuit.

5. A backup battery switching circuit according to claim 1, wherein The power supply current flow control circuit comprises a diode D4, a diode D5 and a controlled switch K, one end of the controlled switch K is connected to a cathode of the diode D4 and then connected to VRTC, the other end of the controlled switch K is connected to an anode of the diode D5, a controlled end BAT_CTRL of the controlled switch K is connected to an IO port of the MCU, and an anode of the diode D4 is connected to a cathode of the diode D5 and then connected to an output VDD of the first LDO circuit.

6. A backup battery switching circuit according to claim 1, wherein The first LDO circuit comprises a voltage stabilizing chip U1, a capacitor C4 and a capacitor C6, a power supply input pin of the voltage stabilizing chip U1 is connected to one end of the capacitor C4 and then connected to VBB_IN, a power supply output pin of the voltage stabilizing chip U1 is connected to one end of the capacitor C6 and then connected to the power supply current flow control circuit as an output VDD, and a grounding pin of the voltage stabilizing chip U1, the other end of the capacitor C4 and the other end of the capacitor C6 are all connected to a power supply ground.

7. A backup battery switching circuit according to claim 1, wherein The second LDO circuit comprises a voltage stabilizing chip U2, a capacitor C5 and a capacitor C7, a power supply input pin of the voltage stabilizing chip U2 is connected to one end of the capacitor C5 and then connected to VBB_IN, a power supply output pin of the voltage stabilizing chip U2 is connected to one end of the capacitor C7 and then connected to a power supply pin VCC of the MCU, a cover opening detection circuit power supply VBB and a power supply of other low-power-consumption circuits, and a grounding pin of the voltage stabilizing chip U2, the other end of the capacitor C5 and the other end of the capacitor C7 are all connected to a power supply ground.

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