A smart electric meter and its power failure backup power supply circuit

Abstract

The present application discloses a smart meter and a power-off backup power supply circuit thereof, which includes a switching circuit, a voltage detection circuit, and a supercapacitor. The switching circuit includes a first switch module, a second switch module, and an LDO circuit. The voltage detection circuit is connected to the switching circuit and is used to detect the voltage value of a detection point in the switching circuit. The switching circuit determines the current path flowing to the rear-end load according to the voltage value. The first switch module is between the rear-end load and the supercapacitor, and is used to connect the rear-end load to the supercapacitor when the voltage value is less than a threshold value. The second switch module is between the LDO circuit and the supercapacitor, and is used to connect the LDO circuit and the supercapacitor when the voltage is not less than a threshold value. This circuit sets a detection point in the switching circuit, and determines the path taken by the current according to the voltage of the detection point. When switching to the first switch module, there is no voltage drop of the LDO, and the supercapacitor can be discharged to a lower voltage, thereby improving the energy utilization rate of the supercapacitor.

Description

Technical Field

[0001] The present application relates to the field of power supply, and in particular to a smart electric meter and a power failure backup power supply circuit thereof. Background Art

[0002] With the development of science and technology, traditional meters are gradually being replaced by smart meters. Smart meters are one of the basic devices for data collection in smart grids. They undertake the tasks of collecting, measuring and transmitting original electric energy data, and are the basis for realizing information integration, analysis optimization and information display. In addition to the basic electricity consumption metering function of traditional electric energy meters, in order to adapt to the use of smart grids and new energy, smart meters also have intelligent functions such as two-way multi-rate metering function, user-side control function, two-way data communication function with multiple data transmission modes, and anti-electricity theft function. Among them, the communication function of smart meters is an important part of smart meters. The communication module of smart meters needs to ensure the supply of electric energy, which is usually achieved through a power-off backup power supply circuit. Figure 1 This is the LDO circuit diagram in the traditional power-off backup power supply circuit. Figure 2 The charging circuit diagram of the super capacitor E1 in the traditional power failure backup power supply circuit is as follows: Figure 1 and Figure 2 As shown, in the case of power failure, the power supply of the electric meter passes through a low dropout regulator (LDO) or a DC-DC converter, wherein one path of +VMAIN passes through a Schottky diode D23 to reach the LDO input, and the LDO output supplies the subsequent circuit, and the other path of +VMAIN passes through a current limiting resistor R63 and a Schottky diode D19 to charge the super capacitor E1. After the electric meter loses power, +VMAIN loses power, and the super capacitor E1 supplies power to the LDO through a Schottky diode D4, and the LDO output supplies the subsequent circuit.

[0003] Since the output power is converted by LDO, when the smart meter is in working state for a long time, the current inside the meter will be very small, and when it is converted by LDO, it will cause the problem of increased power consumption.

[0004] In view of the above technology, seeking a power-off switching circuit is an urgent problem to be solved by those skilled in the art. Summary of the invention

[0005] The purpose of the present application is to provide a power failure backup power supply circuit, which can select a current path for the current flowing to the rear-end load according to the voltage value of the detection point. In addition, the present application also provides a smart meter.

[0006] In order to solve the above technical problems, the present application provides a power-off backup power supply circuit, including: a voltage detection circuit 11, a switching circuit 12, and a super capacitor; wherein the switching circuit 12 includes a first switch module 13, a second switch module 14, and an LDO circuit 15;

[0007] The voltage detection circuit 11 is connected to the switching circuit 12 and is used to detect the voltage value of the detection point in the switching circuit 12; the switching circuit 12 determines the current path flowing to the rear-end load according to the voltage value;

[0008] The first switch module 13 is located between the rear-end load and the supercapacitor, and is used to connect the rear-end load to the supercapacitor when the voltage value is less than a threshold value; the LDO circuit 15 is connected to the rear-end load, and the second switch module 14 is located between the LDO circuit 15 and the supercapacitor, and is used to connect the LDO circuit 15 to the supercapacitor when the voltage value is not less than a threshold value.

[0009] Preferably, the first switch module 13 includes a first MOS transistor, a second MOS transistor, a third MOS transistor, a first diode, a first resistor, and a second resistor;

[0010] The output end of the voltage detection circuit 11 is connected to the gate of the first MOS tube; the source of the first MOS tube is grounded, and the drain of the first MOS tube is respectively connected to the second end of the first resistor and the gate of the second MOS tube; the source of the second MOS tube is respectively connected to the first end of the first resistor and the source of the third MOS tube, the drain of the second MOS tube is respectively connected to the first end of the second resistor and the gate of the third MOS tube, and the second end of the second resistor is grounded; the anode of the first diode is connected to the drain of the third MOS tube, and the cathode of the first diode is used to be connected to the back-end load.

[0011] Preferably, the second switch module 14 includes a fourth MOS transistor, a fifth MOS transistor, a second diode, and a third resistor;

[0012] The input end of the voltage detection circuit 11 is respectively connected to the anode of the second diode and the drain of the fifth MOS tube; the cathode of the second diode is connected to the input end of the LDO circuit 15; the first end of the super capacitor is respectively connected to the source of the third MOS tube, the first end of the third resistor and the source of the fifth MOS tube, and the second end of the super capacitor is grounded; the second end of the third resistor is respectively connected to the gate of the fifth MOS tube and the drain of the fourth MOS tube; the gate of the fourth MOS tube is connected to the first end of the second resistor, and the source of the fourth MOS tube is grounded.

[0013] Preferably, the detection point is between the anode of the second diode and the drain of the fifth MOS transistor.

[0014] Preferably, the voltage detection circuit 11 includes a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a first capacitor and a voltage detection chip;

[0015] The first end of the first capacitor, the first end of the fourth resistor and the first end of the seventh resistor are connected to the first end of the voltage detection chip; the second end of the fourth resistor, the first end of the fifth resistor and the first end of the sixth resistor are connected to the second end of the voltage detection chip, and the second end of the sixth resistor, the second end of the seventh resistor and the first end of the eighth resistor are connected to the third end of the voltage detection chip; the second end of the first capacitor, the second end of the fifth resistor, the second end of the eighth resistor and the fourth end of the voltage detection chip are grounded; the first end of the voltage detection chip serves as the input end of the voltage detection circuit 11, and the third end of the voltage detection chip serves as the output end of the voltage detection circuit 11.

[0016] Preferably, it is characterized in that the LDO circuit 15 includes an LDO chip, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor and a sixth capacitor; wherein the first end of the second capacitor and the first end of the third capacitor are connected to the first end of the LDO chip, and the first end of the fourth capacitor, the first end of the fifth capacitor and the first end of the sixth capacitor are connected to the second end of the LDO circuit 15; the second end of the second capacitor, the second end of the third capacitor, the second end of the fourth capacitor, the second end of the fifth capacitor, the second end of the sixth capacitor and the third end of the LDO chip are grounded; the fourth end of the LDO chip is connected to the first end of the LDO chip; the first end of the LDO chip is the input end of the LDO circuit 15, and the second end of the LDO chip is the output end of the LDO circuit 15.

[0017] Preferably, a current limiting charging circuit is further included, and the output end of the current limiting charging circuit is connected to the detection point of the switching circuit 12 for current limiting charging of the super capacitor.

[0018] In order to solve the above technical problems, the present application also provides a smart electric meter, including the power-off backup power supply circuit.

[0019] The power-off backup power supply circuit provided in the present application includes a switching circuit, a voltage detection circuit, and a supercapacitor, wherein the switching circuit includes a first switch module, a second switch module and an LDO circuit, the voltage detection circuit is connected to the switching circuit, and is used to detect the voltage value of a detection point in the switching circuit, and the switching circuit determines the current path flowing to the rear-end load according to the voltage value, the first switch module is between the rear-end load and the supercapacitor, and is used to connect the rear-end load to the supercapacitor when the voltage value is less than a threshold value, and the second switch module is between the LDO circuit and the supercapacitor, and is used to connect the LDO circuit and the supercapacitor when the voltage is not less than a threshold value. It can be seen that this circuit sets a detection point in the switching circuit, and determines the path of the current according to the voltage of the detection point. When switching to the first switch module, there is no voltage drop of the LDO, and the supercapacitor can be discharged to a lower voltage, thereby improving the energy utilization rate of the supercapacitor, increasing the service life of the equipment, and improving the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 This is the LDO circuit diagram in the traditional power-off backup power supply circuit;

[0022] Figure 2 This is a charging circuit diagram of the supercapacitor E1 in the traditional power failure backup power supply circuit;

[0023] Figure 3 A schematic diagram of a power-off backup power supply circuit provided in an embodiment of the present application;

[0024] Figure 4 A schematic diagram of the structure of a switching circuit provided in an embodiment of the present application;

[0025] Figure 5 A schematic diagram of the structure of a voltage detection circuit provided in an embodiment of the present application;

[0026] Figure 6 A schematic diagram of the structure of a current limiting charging circuit provided in an embodiment of the present application.

[0027] Among them, 11 is a voltage detection circuit, 12 is a switching circuit, 13 is a first switch module, 14 is a second switch module, and 15 is an LDO circuit. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0029] The core of this application is to provide a power-off backup power supply circuit, which is used to select a suitable current path to the rear-end load when the voltage at the detection point is greater than or less than the threshold value, so as to avoid the problem of increased power consumption caused by the long-term discharge of the supercapacitor through the LDO circuit. In order to enable people in this technical field to better understand the application scheme, the application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0030] Figure 3 A schematic diagram of a power failure backup power supply circuit provided in an embodiment of the present application is shown below. Figure 3 The structure of the power-off backup power supply circuit shown in the figure is explained.

[0031] The communication function of smart meters is an important part of smart meters. The communication module of smart meters needs to ensure power supply, which is usually achieved through a power failure backup power supply circuit. It is understandable that in the case of power failure, the existing technology Figure 1 and Figure 2 As shown, the power supply of the meter passes through LDO or DC-DC converter, where one of the +VMAIN passes through Schottky diode D23 to reach LDO input, and LDO output supplies the subsequent circuit. The other +VMAIN passes through current limiting resistor R63 and Schottky diode D19 to charge super capacitor E1. After the meter is powered off, +VMAIN is powered off, super capacitor E1 supplies power to LDO through Schottky diode D4, and LDO output supplies the subsequent circuit. However, since the output power is converted by LDO, when the smart meter is in working state for a long time, the current inside the meter will be very small, and when it is converted by LDO, it will cause the problem of increased power consumption. Therefore, as Figure 3As shown, the power-off backup power supply circuit includes a switching circuit 12, a voltage detection circuit 11, and a super capacitor, wherein the switching circuit 12 includes a first switch module 13, a second switch module 14, and an LDO circuit 15. The voltage detection circuit 11 is connected to the switching circuit 12, and is used to detect the voltage value of the detection point in the switching circuit 12. The switching circuit 12 determines the current path flowing to the rear-end load according to the detected voltage value. The first switch module 13 is located between the rear-end load and the super capacitor, and is used to connect the rear-end load to the super capacitor when the voltage value is less than a threshold value, and the LDO circuit 15 is connected to the rear-end load. The second switch module 14 is located between the LDO circuit 15 and the super capacitor, and is used to connect the LDO circuit 15 to the super capacitor when the voltage value is not less than a threshold value, thereby solving the problem of energy loss of the LDO circuit 15 during the discharge process.

[0032] In addition, there is no limitation on the type of supercapacitor, and it is only necessary to ensure that the rated capacity of the capacitor can store enough electricity to meet the use of the back-end load and can be recycled. In addition, there is no limitation on the specific structure of the first switch module 13 and the second switch module 14, nor on the specific connection method of the first switch module 13 with the supercapacitor and the back end, nor on the specific connection method of the second switch module 14 with the supercapacitor and the LDO circuit 15, nor on the connection method of the LDO circuit 15 with the back-end load, which can be determined according to the specific implementation situation.

[0033] In addition, when the voltage value at the detection point is less than the threshold value, the super capacitor is connected to the rear-end load through the first switch module 13, and the current is emitted by the super capacitor and flows to the rear-end load through the first switch module 13. When the voltage value at the detection point is not less than the threshold value, the power-off backup power supply circuit can withstand the loss of electric energy by the LDO circuit 15, so the super capacitor is connected to the LDO circuit 15 through the second switch module 14, and the LDO circuit 15 itself is connected to the rear-end load, and the LDO circuit 15 plays a role in voltage stabilization. Therefore, when the voltage value at the detection point is not less than the threshold value, the current is emitted by the super capacitor and reaches the LDO circuit 15 through the second switch module 14, and finally flows to the rear-end load.

[0034] It is worth noting that this embodiment does not limit the specific position of the detection point in the switching circuit 12, which can be determined according to the specific implementation situation. At the same time, the specific structure of the voltage detection circuit 11 for detecting the voltage at the detection point in the switching circuit 12 is not limited. In addition, there is no limitation on the charging method of the supercapacitor, which can be selected according to the specific implementation situation.

[0035] It can be seen that the power-off backup power supply circuit provided in this embodiment is mainly used in the communication module in the smart meter. The circuit includes a switching circuit, a voltage detection circuit, and a supercapacitor, wherein the switching circuit includes a first switch module, a second switch module and an LDO circuit. The voltage detection circuit is connected to the switching circuit and is used to detect the voltage value of the detection point in the switching circuit. The switching circuit determines the current path flowing to the rear-end load according to the voltage value. The first switch module is between the rear-end load and the supercapacitor, and is used to connect the rear-end load to the supercapacitor when the voltage value is less than the threshold. The second switch module is between the LDO circuit and the supercapacitor, and is used to connect the LDO circuit and the supercapacitor when the voltage is not less than the threshold. It can be seen that this circuit sets a detection point in the switching circuit, and determines the path of the current according to the voltage of the detection point. When switching to the first switch module, there is no voltage drop of the LDO, and the supercapacitor can be discharged to a lower voltage, thereby improving the energy utilization rate of the supercapacitor, improving the service life of the equipment and improving the user experience.

[0036] On the basis of the above embodiment, the connection mode between the voltage detection circuit 11 and the first switch module 13 is limited, the specific structure of the first switch module 13 is limited, and how the first switch module 13 is connected to the rear-end load is also limited. Figure 4 A schematic diagram of the structure of the switching circuit 12 provided in the embodiment of the present application is shown in FIG. Figure 4 As shown, the first switch module 13 includes a first MOS transistor Q1, a second MOS transistor Q2, a third MOS transistor Q3, a first diode D1, a first resistor R1, and a second resistor R2. In addition, the first MOS transistor Q1 is an N-channel MOS transistor, and the second MOS transistor Q2 and the third MOS transistor Q3 are P-channel MOS transistors.

[0037] The specific connection mode is that the output end of the voltage detection circuit 11 is connected to the gate of the first MOS tube Q1; the source of the first MOS tube Q1 is grounded, the drain of the first MOS tube Q1 is respectively connected to the second end of the first resistor R1 and the gate of the second MOS tube Q2, the source of the second MOS tube Q2 is respectively connected to the first end of the first resistor R1 and the source of the third MOS tube Q3, the drain of the second MOS tube Q2 is respectively connected to the first end of the second resistor R2 and the gate of the third MOS tube Q3, the second end of the second resistor R2 is grounded, the anode of the first diode D1 is connected to the drain of the third MOS tube Q3, and the cathode of the first diode D1 is used to be connected to the rear-end load.

[0038] The first switch module 13 plays a role in connecting the super capacitor E1 and the back-end load when the voltage value at the detection point is lower than the threshold value. When the voltage value at the detection point is less than the threshold value, the voltage detection circuit 11 outputs a low-level signal to the gate of the first MOS tube Q1, so the source and drain of the first MOS tube Q1 and the second MOS tube Q2 are not conducting, and the second end of the second resistor R2 is grounded, and the other end is connected to the gate of the third MOS tube Q3, pulling down the gate voltage of the third MOS tube Q3, so the source and drain of the third MOS tube Q3 are conducting, so the super capacitor E1 is connected to the back-end load through the conducting third MOS tube Q3 and the first diode D1, and supplies power to the back-end load.

[0039] In addition, the diode plays the role of unidirectional conduction in this circuit. This embodiment does not limit the type of diode, which can be an ordinary diode or a Schottky diode. As the most common diode, the ordinary diode can play the role of unidirectional conduction, and its voltage resistance performance is relatively good, but its recovery speed is relatively low, and it can only be used in low-frequency rectification. If it is used in high frequency, reverse leakage will occur due to the inability to recover quickly, and finally cause the diode to heat up and burn out seriously. The Schottky diode can not only play the role of unidirectional conduction, but also has a fast recovery speed, and can be used in high-frequency occasions. The recovery time of the Schottky diode is about one hundred times shorter than that of the ordinary diode. Therefore, the Schottky diode can be used as the diode used in this application.

[0040] It can be seen that the specific connection method between the first switch module and the voltage detection circuit and the rear-end load, as well as the specific structure of the first switch module provided in this embodiment, are provided with three MOS tubes in the first switch module, and the third MOS tube is turned on by outputting a low level to the first MOS tube, so that the supercapacitor and the rear-end load are connected. In addition, the possibility of damage to components is reduced by the Schottky diode. Therefore, this method reduces the power consumption of the circuit and increases the service life of the components.

[0041] On the basis of the above embodiment, the connection mode of the voltage detection circuit 11 and the second switch module 14 is limited, the specific structure of the second switch module 14 is limited, and how the second switch module 14 and the LDO circuit 15 are connected is also limited, such as Figure 4 As shown, the second switch module 14 includes a fourth MOS transistor Q4, a fifth MOS transistor Q5, a second diode D2, and a third resistor. In addition, the fourth MOS transistor Q4 is an N-channel MOS transistor, and the fifth MOS transistor Q5 is a P-channel MOS transistor. The type of the second diode D2 is not limited, and it can be a Schottky diode or a common diode.

[0042] The specific connection method is that the input end of the voltage detection circuit 11 is respectively connected to the anode of the second diode D2 and the drain of the fifth MOS tube Q5; the cathode of the second diode D2 is connected to the input end of the LDO circuit 15; the first end of the super capacitor E1 is respectively connected to the source of the third MOS tube Q3, the first end of the third resistor R3 and the source of the fifth MOS tube Q5, and the second end of the super capacitor E1 is grounded; the second end of the third resistor R3 is respectively connected to the gate of the fifth MOS tube Q5 and the drain of the fourth MOS tube Q4; the gate of the fourth MOS tube Q4 is connected to the first end of the second resistor, and the source of the fourth MOS tube Q4 is grounded.

[0043] The second switch module 14 is used to connect the super capacitor E1 and the LDO circuit 15 when the voltage detection circuit 11 detects that the voltage value at the detection point in the switching circuit 12 is not less than the threshold value. When the voltage value at the detection point is not less than the threshold value, the voltage detection circuit 11 outputs a high-level signal to the gate of the first MOS tube Q1, so the source and drain of the first MOS tube Q1 and the second MOS tube Q2 are turned on, the source and drain of the third MOS tube Q3 are not turned on, and the gate of the fourth MOS tube Q4 is connected to the first end of the second resistor R2, so the source and drain of the fourth MOS tube Q4 are turned on, and the source and drain of the fifth MOS tube Q5 are also turned on, so the super capacitor E1 is connected to the LDO circuit 15 through the turned-on fifth MOS tube Q5 and the second diode D2, and the current flows out from the super capacitor E1 through the fifth MOS tube Q5 and the second diode D2 to reach the LDO circuit 15, and the LDO circuit 15 has established a connection with the back-end load. After the current reaches the LDO circuit 15, it finally flows to the back-end load.

[0044] It can be seen that the specific connection method between the second switch module and the voltage detection circuit and the LDO circuit provided in this embodiment, as well as the specific structure of the second switch module, is that two MOS tubes are arranged in the second switch module, and current flows out by turning on the MOS tubes, and the source and drain of the third MOS tube are turned on by outputting a high level to the first MOS tube. Since the gate of the fourth MOS tube is connected to the first end of the second resistor, the source and gate of the fourth MOS tube are turned on, and the source and gate of the fifth MOS tube are also turned on, so that the super capacitor and the LDO circuit are turned on, and the LDO circuit is connected to the back-end load, then the current flows out from the super capacitor through the LDO circuit and flows to the back-end load. This method reduces the power consumption of the circuit and improves the service life of components.

[0045] On the basis of the above embodiment, the specific position of the detection point in the switching circuit 12 is limited, and the detection point is located between the anode of the second diode D2 and the drain of the fifth MOS transistor Q5.

[0046] It is understandable that this embodiment only provides a preferred implementation method, and the position of the detection point can also be selected according to the specific implementation situation. The detection point is between the anode of the second diode D2 and the drain of the fifth MOS tube Q5, so that the power consumption of the capacitor can be directly detected.

[0047] In addition, the voltage detection circuit 11 detects the voltage in the switching circuit 12 to provide a basis for the switching circuit 12 to switch to a specific circuit. Figure 4 As shown, when power failure occurs, the super capacitor E1 discharges. If the detection point is directly set at the first end of the super capacitor E1, the voltage detection circuit 11 will consume part of the power of the super capacitor E1, wasting resources. Therefore, it is necessary to set the detection point at other positions. The best position for setting the detection point is between the anode of the second diode D2 and the drain of the fifth MOS tube Q5.

[0048] It should be noted that this position is also the connection position between the output end of the charging circuit for charging the super capacitor E1 and the switching circuit 12. Specifically, when power failure does not occur, the charging circuit is connected to the detection point, and the voltage detection circuit 11 detects that the voltage value of the detection point at this time is greater than the threshold, and sends a high level to the gate of the first MOS tube Q1. It can be seen from the above embodiment that the source and drain of the fifth MOS tube Q5 are finally turned on, and the charging current charges the super capacitor E1 through the fifth MOS tube Q5.

[0049] It can be seen that the detection point provided in this embodiment is between the anode of the second diode D2 and the drain of the fifth MOS tube, which avoids directly measuring the voltage value at the connection between the supercapacitor and the switching circuit, resulting in the voltage detection circuit consuming the power of the supercapacitor after switching to the first switch module.

[0050] In a specific embodiment, the voltage detection circuit 11 detects the detection point in the switching circuit 12 and sends the detection result to the switching circuit 12, and the switching circuit 12 selects the path for the current to flow to the rear-end load. Figure 5 A schematic diagram of a voltage detection circuit 11 provided in an embodiment of the present application is shown in FIG. Figure 5 As shown, the voltage detection circuit 11 includes a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a first capacitor C1 and a voltage detection chip. The specific structure of the voltage detection circuit 11 is as follows:

[0051] The first end of the first capacitor C1, the first end of the fourth resistor R4 and the first end of the seventh resistor R7 are connected to the first end of the voltage detection chip; the second end of the fourth resistor R4, the first end of the fifth resistor R5 and the first end of the sixth resistor R6 are connected to the second end of the voltage detection chip, and the second end of the sixth resistor R6, the second end of the seventh resistor R7 and the first end of the eighth resistor R8 are connected to the third end of the voltage detection chip; the second end of the first capacitor C1, the second end of the fifth resistor R5, the second end of the eighth resistor R8 and the fourth end of the voltage detection chip are grounded; the first end of the voltage detection chip serves as the input end of the voltage detection circuit 11, and the third end of the voltage detection chip serves as the output end of the voltage detection circuit 11.

[0052] It is worth noting that the voltage detection chip in the voltage detection circuit 11 is not limited in this embodiment, and can be a chip of the SGM897A or TPS3803 series, or can be changed to a triode circuit for detection, and it is only necessary to ensure that the voltage of the detection point in the switching circuit 12 is detected in real time, and the voltage detection chip can be selected according to the specific implementation situation. In addition, the threshold value compared with the voltage value detected by the voltage detection circuit 11 is set by the resistance values ​​of the fourth resistor R4, the fifth resistor R5 and the sixth resistor R6.

[0053] It can be seen that the voltage detection circuit provided in this embodiment sets the resistance values ​​of the fourth resistor, the fifth resistor and the sixth resistor as the setting of the threshold value, and detects the voltage of the detection point in the switching circuit through the voltage detection circuit. This method can accurately detect the voltage of the detection point, and can also change the resistance to change the size of the threshold value according to the specific situation of the circuit, thereby effectively reducing the power consumption of the circuit and improving the service life of components.

[0054] In a specific embodiment, the current flowing out of the super capacitor E1 can flow to the rear-end load through the first switch module 13, or can reach the LDO circuit 15 through the second switch module 14 and flow to the rear-end load, and the current path is determined by the switching circuit 12. Figure 2 The schematic diagram of the structure of the LDO circuit 15 provided in the embodiment of the present application is as follows: Figure 2 As shown, the LDO circuit 15 includes an LDO chip, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5 and a sixth capacitor C6, and the specific structure of the LDO circuit 15 is as follows:

[0055] The first end of the second capacitor C2 and the first end of the third capacitor C3 are connected to the first end of the LDO chip, and the first end of the fourth capacitor C4, the first end of the fifth capacitor C5 and the first end of the sixth capacitor C6 are connected to the second end of the LDO circuit 15; the second end of the second capacitor C2, the second end of the third capacitor C3, the second end of the fourth capacitor C4, the second end of the fifth capacitor C5, the second end of the sixth capacitor C6 and the third end of the LDO chip are grounded; the fourth end of the LDO chip is connected to the first end of the LDO chip; the first end of the LDO chip is the input end of the LDO circuit 15, and the second end of the LDO chip is the output end of the LDO circuit 15.

[0056] It is understandable that LDO is a low-cost, low-noise, low-quiescent current low-dropout linear regulator. In addition, LDO has relatively few peripheral devices, usually only a few bypass capacitors. These are the more prominent advantages of LDO.

[0057] It can be seen that this method uses the LDO circuit as the circuit to be taken when the voltage value at the detection point is greater than the threshold value. The advantages of LDO such as low cost, low noise, and small static current can effectively reduce the power consumption in the circuit. When the voltage value at the detection point is less than the threshold value, the current path is not the LDO circuit, which can effectively improve the service life of the LDO chip and reduce the power consumption of the circuit.

[0058] In the above embodiment, there is no limitation on the specific structure of the charging circuit for charging the super capacitor E1, which is determined according to the specific implementation situation. As a preferred embodiment, in this embodiment, the circuit for charging the super capacitor E1 is a current limiting charging circuit; wherein the output end of the current limiting charging circuit is connected to the detection point.

[0059] like Figure 6As shown, in the current limiting charging circuit, the first end of the tenth resistor R10 is connected to the source of the sixth MOS tube Q6, the second end of the tenth resistor R10 and the first end of the seventh capacitor C7 are connected to the first end of the eleventh resistor R11, and the second end of the eleventh resistor R11 and the second end of the seventh capacitor C7 are grounded; the gate of the sixth MOS tube Q6 and the drain of the seventh MOS tube Q7 are connected to the second end of the thirteenth resistor R13, the first end of the thirteenth resistor R13 is connected to +V1F5, the gate of the seventh MOS tube Q7 is connected to the first end of the fourteenth resistor R14 and the gate of the ninth MOS tube Q9, the source of the seventh MOS tube Q7, the source of the ninth MOS tube Q9 and the second end of the fourteenth resistor R14 are grounded. The drain of the ninth MOS tube Q9 is connected to the second end of the eighteenth resistor R18, the first end of the eighteenth resistor R18 is connected to the second end of the seventeenth resistor R17 and the first end of the amplifier, and the first end of the seventeenth resistor R17 is connected to the power output end. The drain of the sixth MOS tube Q6 is connected to the drain of the eighth MOS tube Q8 and the second end of the resistor R19; the source of the eighth MOS tube Q8 is connected to the second end of the twelfth resistor R12 and the second end of the fifteenth resistor R15, and the gate of the eighth MOS tube Q8 is connected to the second end of the sixteenth resistor R16. The first end of the twelfth resistor R12 is connected to the power supply output end, the first end of the fifteenth resistor R15 is connected to the first end of the ninth capacitor C9 and the first end of the resistor R19 and the second end of the amplifier; the first end of the sixteenth resistor R16 is connected to the second end of the ninth capacitor C9 and the fifth end of the amplifier. The power supply output end is also connected to the first end of the eighth capacitor C8 and the third end of the amplifier, and the second end of the eighth capacitor C8 and the fourth end of the amplifier are grounded. In this embodiment, the output end of the current limiting charging circuit is set at the first end of the tenth resistor R10, and is connected to the switching circuit 12 at the detection point. It should be noted that the seventh MOS tube Q7 is an N-channel MOS tube, the eighth MOS tube Q8 is a P-channel MOS tube, and the ninth MOS tube Q9 is an N-channel MOS tube.

[0060] It can be seen that the circuit using current limiting charging provided in this embodiment charges the supercapacitor, has a precise output voltage, limits the output current, and can effectively protect the supercapacitor.

[0061] Finally, the embodiment of the present application further provides a smart meter, which includes a switching circuit 12 and other circuits, and also includes the voltage detection circuit 11 mentioned in the above embodiment, which is used to obtain the voltage of the detection point in the switching circuit 12. Since each circuit is described in detail above, it will not be repeated in this embodiment.

[0062] The smart meter provided in this embodiment includes a power-off backup power supply circuit, which includes a switching circuit, a voltage detection circuit, and a supercapacitor, wherein the switching circuit includes a first switch module, a second switch module, and an LDO circuit. The voltage detection circuit is connected to the switching circuit and is used to detect the voltage value of a detection point in the switching circuit. The switching circuit determines the current path flowing to the rear-end load according to the voltage value. The first switch module is between the rear-end load and the supercapacitor and is used to connect the rear-end load to the supercapacitor when the voltage value is less than a threshold value. The second switch module is between the LDO circuit and the supercapacitor and is used to connect the LDO circuit to the supercapacitor when the voltage is not less than a threshold value. It can be seen that this circuit sets a detection point in the switching circuit and determines the path taken by the current according to the voltage of the detection point. When switching to the first switch module, there is no voltage drop of the LDO, and the supercapacitor can be discharged to a lower voltage, thereby improving the energy utilization rate of the supercapacitor, improving the service life of the equipment, and improving the user experience.

[0063] The power-off backup power supply circuit provided by the present application is introduced in detail above. The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

[0064] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

Claims

1. A power failure backup power supply circuit, characterized in that: include: A voltage detection circuit (11), a switching circuit (12), and a super capacitor; wherein the switching circuit (12) comprises a first switch module (13), a second switch module (14), and an LDO circuit (15); The voltage detection circuit (11) is connected to the switching circuit (12) and is used to detect a voltage value at a detection point in the switching circuit (12); the switching circuit (12) determines a current path flowing to a rear-end load according to the voltage value; The first switch module (13) is located between the rear-end load and the super capacitor, and is used to connect the rear-end load to the super capacitor when the voltage value is less than a threshold value; the LDO circuit (15) is connected to the rear-end load, and the second switch module (14) is located between the LDO circuit (15) and the super capacitor, and is used to connect the LDO circuit (15) to the super capacitor when the voltage value is not less than a threshold value; The first switch module (13) comprises a first MOS transistor, a second MOS transistor, a third MOS transistor, a first diode, a first resistor, and a second resistor; the first MOS transistor is an N-channel MOS transistor, and the second MOS transistor and the third MOS transistor are P-channel MOS transistors; The output end of the voltage detection circuit (11) is connected to the gate of the first MOS tube; the source of the first MOS tube is grounded, the drain of the first MOS tube is respectively connected to the second end of the first resistor and the gate of the second MOS tube; the source of the second MOS tube is respectively connected to the first end of the first resistor and the source of the third MOS tube, the drain of the second MOS tube is respectively connected to the first end of the second resistor and the gate of the third MOS tube, and the second end of the second resistor is grounded; the anode of the first diode is connected to the drain of the third MOS tube, and the cathode of the first diode is used to be connected to the back-end load; The second switch module (14) comprises a fourth MOS tube, a fifth MOS tube, a second diode, and a third resistor; the fourth MOS tube is an N-channel MOS tube, and the fifth MOS tube is a P-channel MOS tube; The input end of the voltage detection circuit (11) is respectively connected to the anode of the second diode and the drain of the fifth MOS tube; the cathode of the second diode is connected to the input end of the LDO circuit (15); the first end of the super capacitor is respectively connected to the source of the third MOS tube, the first end of the third resistor and the source of the fifth MOS tube, and the second end of the super capacitor is grounded; the second end of the third resistor is respectively connected to the gate of the fifth MOS tube and the drain of the fourth MOS tube; the gate of the fourth MOS tube is connected to the first end of the second resistor, and the source of the fourth MOS tube is grounded; The detection point is between the anode of the second diode and the drain of the fifth MOS tube; The power-off backup power supply circuit also includes a current limiting charging circuit, the output end of which is connected to the detection point of the switching circuit (12) and is used to perform current limiting charging on the super capacitor; Wherein, the current limiting charging circuit includes: a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, an eighteenth resistor, a nineteenth resistor, a sixth MOS tube, a seventh MOS tube, an eighth MOS tube, a ninth MOS tube, a seventh capacitor, an eighth capacitor, a ninth capacitor and an amplifier; The first end of the tenth resistor is connected to the source of the sixth MOS tube, the second end of the tenth resistor and the first end of the seventh capacitor are connected to the first end of the eleventh resistor; the second end of the eleventh resistor and the second end of the seventh capacitor are grounded; the gate of the sixth MOS tube and the drain of the seventh MOS tube are connected to the second end of the thirteenth resistor, and the first end of the thirteenth resistor is connected to the power output end; the gate of the seventh MOS tube is connected to the first end of the fourteenth resistor and the gate of the ninth MOS tube; the source of the seventh MOS tube, the source of the ninth MOS tube and the second end of the fourteenth resistor are grounded; the drain of the ninth MOS tube is connected to the second end of the eighteenth resistor, and the first end of the eighteenth resistor is connected to the second end of the seventeenth resistor and the first end of the amplifier. one end, the first end of the seventeenth resistor is connected to the power output end; the drain of the sixth MOS tube is connected to the drain of the eighth MOS tube and the second end of the nineteenth resistor; the source of the eighth MOS tube is connected to the second end of the twelfth resistor and the second end of the fifteenth resistor, and the gate of the eighth MOS tube is connected to the second end of the sixteenth resistor; the first end of the twelfth resistor is connected to the power output end, the first end of the fifteenth resistor is connected to the first end of the ninth capacitor, the first end of the nineteenth resistor and the second end of the amplifier; the first end of the sixteenth resistor is connected to the second end of the ninth capacitor and the fifth end of the amplifier; the power output end is also connected to the first end of the eighth capacitor and the third end of the amplifier, and the second end of the eighth capacitor and the fourth end of the amplifier are grounded.

2. The power-off backup power supply circuit according to claim 1, characterized in that: The voltage detection circuit (11) comprises a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a first capacitor and a voltage detection chip; The first end of the first capacitor, the first end of the fourth resistor and the first end of the seventh resistor are connected to the first end of the voltage detection chip; the second end of the fourth resistor, the first end of the fifth resistor and the first end of the sixth resistor are connected to the second end of the voltage detection chip, and the second end of the sixth resistor, the second end of the seventh resistor and the first end of the eighth resistor are connected to the third end of the voltage detection chip; the second end of the first capacitor, the second end of the fifth resistor, the second end of the eighth resistor and the fourth end of the voltage detection chip are grounded; the first end of the voltage detection chip serves as the input end of the voltage detection circuit (11), and the third end of the voltage detection chip serves as the output end of the voltage detection circuit (11).

3. The power failure backup power supply circuit according to claim 1 or 2, characterized in that: The LDO circuit (15) comprises an LDO chip, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor and a sixth capacitor; wherein the first end of the second capacitor and the first end of the third capacitor are connected to the first end of the LDO chip, and the first end of the fourth capacitor, the first end of the fifth capacitor and the first end of the sixth capacitor are connected to the second end of the LDO circuit (15); the second end of the second capacitor, the second end of the third capacitor, the second end of the fourth capacitor, the second end of the fifth capacitor, the second end of the sixth capacitor and the third end of the LDO chip are grounded; the fourth end of the LDO chip is connected to the first end of the LDO chip; the first end of the LDO chip is the input end of the LDO circuit (15), and the second end of the LDO chip is the output end of the LDO circuit (15).

4. A smart electric meter, characterized in that: The invention comprises the power-off backup power supply circuit as claimed in any one of claims 1 to 3.

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