A power failure detection circuit and power failure detection method for electric energy meter

Abstract

The present application relates to the technical field of electric energy meter circuits, and in particular to an electric energy meter power failure detection circuit and a power failure detection method, which includes a transformer and a switching power supply module connected between the primary coil of the transformer and the power grid, for changing its own on-off state based on the detection result; a positive half-cycle sampling terminal for sampling the positive half-cycle signal; a negative half-cycle sampling terminal for sampling the negative half-cycle signal; a signal processing circuit for processing the positive half-cycle signal and the negative half-cycle signal to obtain an operating voltage and a negative level voltage; a voltage divider circuit connected to the signal processing circuit for dividing the operating voltage and the negative level voltage to obtain a sampling voltage; a comparison circuit for comparing the sampling voltage with a preset voltage and generating a corresponding comparison signal based on the comparison result; a control circuit connected to the comparison circuit to obtain a comparison signal, and judging whether there is a power failure based on the comparison signal. The present application has the effect of improving the reliability of power failure detection.

Description

Technical Field

[0001] The present application relates to the technical field of electric energy meter circuits, and in particular to an electric energy meter power failure detection circuit and a power failure detection method. Background Art

[0002] Electronic energy meters use power supply solutions to convert AC to DC, including RC, linear transformer, and switching power supplies. When the grid loses power, the energy meter needs to send a power-loss event signal to the MCU at the instant of the power outage, allowing the MCU to store parameters such as the current power level and time in EEPROM.

[0003] In the related art, in the electric energy meter used in the switching power supply, detection is generally performed at the primary or secondary of the transformer. If the primary output voltage is detected, in order to meet the isolation requirements, the voltage detected at the primary level needs to be isolated after passing through a comparator and an optocoupler. However, setting an optocoupler in the circuit will lead to high circuit cost, and the current transfer ratio of the optocoupler is greatly affected by temperature changes, resulting in poor reliability. If the secondary output voltage is detected, it is difficult to ensure the integrity and reliability of the storage of the remaining power when the power-off signal is detected, because the MCU does not have enough time to store data when the power-off signal is sampled. Summary of the Invention

[0004] The purpose of this application is to improve the reliability of power-off detection.

[0005] In a first aspect, the present application provides an electric energy meter power-off detection circuit, which adopts the following technical solution:

[0006] A power-off detection circuit for an electric energy meter includes a transformer connected to a power grid, including:

[0007] A switching power supply module, connected between the primary coil of the transformer and the power grid, for detecting whether a power outage occurs and changing its on / off state based on the detection result;

[0008] A positive half-cycle sampling terminal connected to the secondary coil of the transformer for sampling the positive half-cycle signal output by the transformer when the switching power supply module is turned off;

[0009] A negative half-cycle sampling terminal connected to the secondary coil of the transformer for sampling the negative half-cycle signal output by the transformer when the switching power supply module is turned on;

[0010] a signal processing circuit connected to the positive half-cycle sampling terminal and the negative half-cycle sampling terminal to obtain the positive half-cycle signal and the negative half-cycle signal, and to process the positive half-cycle signal to obtain a working voltage, and further to process the negative half-cycle signal to obtain a negative level voltage;

[0011] A voltage divider circuit is connected to the signal processing circuit to obtain the working voltage and the negative level voltage, and is used to divide the working voltage and the negative level voltage to obtain a sampling voltage;

[0012] a comparison circuit, for comparing the sampled voltage with a preset voltage and generating a corresponding comparison signal according to the comparison result;

[0013] The control circuit is connected to the comparison circuit to obtain the comparison signal, and determines whether there is a power failure according to the comparison signal, and executes a power failure event to complete the data storage operation when a power failure occurs.

[0014] In other embodiments, a grid filter EMI and a rectifier bridge circuit are further included, wherein the grid filter EMI is connected to the grid, and one end of the rectifier bridge circuit is connected to the grid filter EMI and the other end is connected to the primary coil of the transformer.

[0015] In some other embodiments, the positive half-cycle sampling terminal and the negative half-cycle sampling terminal are connected in parallel with each other;

[0016] The positive half-cycle sampling terminal includes a first diode D1, the anode of the first diode D1 is connected to the eleventh pin of the transformer, and the cathode of the first diode D1 is connected to the signal processing circuit;

[0017] The negative half-cycle sampling terminal includes a second diode D2 , a cathode of the second diode D2 is connected to the eleventh pin of the transformer, and an anode of the second diode D2 is connected to the signal processing circuit.

[0018] In other embodiments, the signal processing circuit includes a first capacitor C1 and a linear regulator LDO, the first capacitor C1 is respectively connected to the cathode and the twelfth pin of the first diode D1, the first capacitor C1 is used to filter the positive half-cycle signal to obtain a DC voltage, and the linear regulator LDO is connected to the first capacitor C1 to step down the DC voltage to obtain the working voltage.

[0019] In other embodiments, the signal processing circuit includes a second capacitor C2, one end of the second capacitor C2 is connected to the positive electrode of the second diode D2, and the other end is grounded, and the second capacitor C2 is used to filter the negative half-cycle signal to obtain a negative level voltage.

[0020] In other embodiments, the voltage divider circuit includes a first resistor R1 and a second resistor R2, one end of the first resistor R1 is connected to the signal processing circuit to receive the operating voltage, and the other end is connected to the second resistor R2, the other end of the second resistor R2 is connected to the signal processing circuit to receive the negative level voltage, and the node between the first resistor R1 and the second resistor R2 is connected to the comparison circuit.

[0021] In a second aspect, the present application provides a method for detecting power failure in an electric energy meter, which adopts the following technical solution:

[0022] A method for detecting power failure of an electric energy meter comprises the following steps:

[0023] Determining the on / off state of the switching power supply module;

[0024] If the switching power supply module is turned off, sampling the positive half-cycle signal;

[0025] If the switching power supply module is turned on, the negative half-cycle signal is sampled;

[0026] Performing signal processing on the positive half-cycle signal and the negative half-cycle signal to obtain a working voltage of the positive half-cycle signal after signal processing and a negative level voltage of the negative half-cycle signal after signal processing, respectively;

[0027] Dividing the operating voltage and the negative level voltage to obtain a sampling voltage;

[0028] Comparing the sampled voltage with a preset voltage to generate a corresponding comparison signal;

[0029] It is determined whether a power failure occurs according to the comparison signal, and if a power failure occurs, a power failure event is executed to complete the data storage operation.

[0030] In some other embodiments, performing signal processing on the positive half-cycle signal and the negative half-cycle signal comprises the following steps:

[0031] Performing rectification and filtering operations on the positive half-cycle signal to obtain a DC voltage;

[0032] Stepping down the DC voltage to obtain the operating voltage;

[0033] The negative half-cycle signal is rectified and filtered to obtain the negative level voltage.

[0034] In summary, this application has the following beneficial technical effects:

[0035] The negative half-cycle signal is sampled from the secondary coil of the transformer. After voltage division, the voltage signal is input into the comparison circuit composed of precision comparators. The comparison circuit outputs a digital signal to the control circuit, that is, the MCU to generate an external interrupt. When the MCU detects the interrupt signal, it immediately executes the power-off time to complete the data storage operation. At this time, the output voltage can still ensure a stable output for about 2 seconds, ensuring the reliability of data storage in the event of a power outage. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the overall circuit connection of the power-off detection circuit of the electric energy meter in the embodiment of the present application;

[0037] Figure 2 It is a flow chart of a method for detecting power failure of an electric energy meter in an embodiment of the present application;

[0038] In the figure, 1. Transformer; 2. Switching power supply module; 3. Positive half-cycle sampling terminal; 4. Negative half-cycle sampling terminal; 5. Signal processing circuit; 6. Voltage divider circuit; 7. Comparison circuit; 8. Control circuit; 9. Rectifier bridge circuit. DETAILED DESCRIPTION

[0039] The following is combined with Figure 1 -Attached Figure 2 , further details of this application are given.

[0040] like Figure 1 As shown, the present application discloses a power-off detection circuit for an electric energy meter, comprising a transformer 1 connected to a power grid, and further comprising:

[0041] The switching power supply module 2 is connected between the primary coil of the transformer 1 and the power grid, and is used to detect whether a power outage occurs and change its own on / off state based on the detection result.

[0042] The positive half-cycle sampling terminal 3 is connected to the primary coil of the transformer 1 to sample the positive half-cycle signal output by the transformer 1 when the switching power supply module 2 is turned off.

[0043] The negative half-cycle sampling terminal 4 is connected to the primary coil of the transformer 1 to sample the negative half-cycle signal output by the transformer 1 when the switching power supply module 2 is turned on.

[0044] The signal processing circuit 5 is connected to the positive half-cycle sampling terminal 3 and the negative half-cycle sampling terminal 4 to obtain the positive half-cycle signal and the negative half-cycle signal, and processes the positive half-cycle signal to obtain the working voltage, and is also used to process the negative half-cycle signal to obtain a negative level voltage.

[0045] The operating voltage is represented as MDVV in this application, and the negative level voltage is represented as -Vcc in this application.

[0046] The voltage divider circuit 6 is connected to the signal processing circuit 5 to obtain the working voltage and the negative level voltage, and is used to divide the working voltage and the negative level voltage to obtain the sampling voltage.

[0047] The comparison circuit 7 compares the sampled voltage with the preset voltage and generates a corresponding comparison signal according to the comparison result.

[0048] The control circuit 8 is connected to the comparison circuit 7 to obtain a comparison signal, and determines whether a power failure occurs according to the comparison signal, and executes a power failure time to complete the data storage operation when a power failure occurs.

[0049] The control circuit 8 in this application is an MCU.

[0050] The negative half-cycle signal is sampled from the secondary coil of the transformer 1. After voltage division, the voltage signal is input into the comparison circuit 7 composed of a precision comparator. The comparison circuit 7 outputs a digital signal to the control circuit 8, that is, the MCU to generate an external interrupt. When the MCU detects the interrupt signal, it immediately executes the power-off time to complete the data storage operation. At this time, the output voltage can still ensure a stable output for about 2 seconds, ensuring the reliability of data storage in the event of a power outage.

[0051] In the embodiment of the present application, the switching power supply module 2 is a switching power supply chip U2. The fifth, sixth, seventh, and eighth pins of the switching power supply module 2 are all connected to the fourth pin of the transformer 1. The node between the switching power supply chip U2 and the transformer 1 is also connected to the node between the sixth pin of the transformer 1 and the power grid via a third diode D3, a ninth capacitor C9, and a fourth resistor R4. The anode of the third diode D3 is connected to the switching power supply chip U2, and the cathode is connected to the ninth capacitor C9 and the fourth resistor R4, respectively.

[0052] The switching power supply chip U2 is used to determine whether a power outage occurs, and receives different enable signals to change its own on / off state according to whether the power outage occurs or not.

[0053] In other embodiments, the power-off detection circuit of the electric energy meter further includes a grid filter EMI and a rectifier bridge circuit 9, the grid filter EMI is connected to the grid, one end of the rectifier bridge circuit 9 is connected to the grid filter EMI, and the other end is connected to the primary coil of the transformer 1.

[0054] In other embodiments, the positive half-cycle sampling terminal 3 and the negative half-cycle sampling terminal 4 are connected in parallel.

[0055] The positive half-cycle sampling terminal 3 includes a first diode D1 , an anode of the first diode D1 is connected to the eleventh pin of the transformer 1 , and a cathode of the first diode D1 is connected to the signal processing circuit 5 .

[0056] The negative half-cycle sampling terminal 4 includes a second diode D2 , a cathode of the second diode D2 is connected to the eleventh pin of the transformer 1 , and an anode of the second diode D2 is connected to the signal processing circuit 5 .

[0057] Since the directions of the diodes corresponding to the positive half-cycle sampling terminal 3 and the negative half-cycle sampling terminal 4 are different, when electrical signals in different directions from the secondary end of the transformer 1 are collected, different sampling terminals can be selected according to the positive and negative half-cycles of the electrical signals.

[0058] At the same time, the first diode D1 and the second diode D2 also have a rectifying function: the first diode D1 can rectify the received positive half-cycle signal, and the second diode D2 can rectify the received negative half-cycle signal.

[0059] In other embodiments, the signal processing circuit 5 includes a first capacitor C1 and a linear regulator LDO, the first capacitor C1 is respectively connected to the cathode and the twelfth pin of the first diode D1, the first capacitor C1 is used to filter the positive half-cycle signal to obtain a DC voltage, and the linear regulator LDO is connected to the first capacitor C1 to step down the DC voltage to obtain an operating voltage.

[0060] The first capacitor C1 filters the positive half-cycle signal rectified by the first diode D1 to obtain a DC voltage, specifically a DC 13V voltage. The linear regulator LDO is used to step down the 13V voltage until it reaches the MCU operating voltage MVDD.

[0061] In other embodiments, the signal processing circuit 5 includes a second capacitor C2, one end of the second capacitor C2 is connected to the anode of the second diode D2, and the other end is grounded. The second capacitor C2 is used to filter the negative half-cycle signal to obtain a negative level voltage.

[0062] The second capacitor C2 filters the negative half-cycle signal to obtain a stable negative level voltage, that is, -Vcc.

[0063] In other embodiments, the voltage divider circuit 6 includes a first resistor R1 and a second resistor R2, one end of the first resistor R1 is connected to the signal processing circuit 5 to receive the operating voltage, and the other end is connected to the second resistor R2, the other end of the second resistor R2 is connected to the signal processing circuit 5 to receive the negative level voltage, and the node between the first resistor R1 and the second resistor R2 is connected to the comparison circuit 7.

[0064] The first resistor R1 and the second resistor R2 are connected between MVDD and -Vcc, and divide the voltage between MVDD and -Vcc to obtain a corresponding sampling voltage, which is represented as Vdetect in this application. The sampling voltage is sent to the comparison circuit 7 for comparison.

[0065] The comparison circuit 7 in this application is a high-precision comparator, which can compare the sampled voltage Vdetect with a preset voltage, and output a corresponding external interrupt signal to the MCU according to the comparison result.

[0066] After receiving the power-off time, the MCU will store the current power value, time and other parameters in the EEPROM.

[0067] This application has the advantages of detection signal isolation, practicality, linear detection, and low cost.

[0068] like Figure 2 As shown, the present application also discloses an electric energy meter detection method, comprising the following steps:

[0069] S100, determining the on / off state of the switching power supply module 2.

[0070] S200: If the switching power supply module 2 is turned off, the positive half-cycle signal is sampled.

[0071] S300: If the switching power supply module 2 is turned on, the negative half-cycle signal is sampled.

[0072] S400 , performing signal processing on the positive half-cycle signal and the negative half-cycle signal to respectively obtain a working voltage of the positive half-cycle signal after signal processing and a negative level voltage of the negative half-cycle signal after signal processing.

[0073] S500 , dividing the operating voltage and the negative level voltage to obtain a sampling voltage.

[0074] S600 , comparing the sampled voltage with a preset voltage to generate a corresponding comparison signal.

[0075] S700, judging whether a power failure occurs according to the comparison signal, and if a power failure occurs, executing the power failure time to complete the data storage operation.

[0076] In some other embodiments, signal processing is performed on the positive half-cycle signal and the negative half-cycle signal, comprising the following steps:

[0077] S410 , performing rectification and filtering operations on the positive half-cycle signal to obtain a DC voltage.

[0078] S420 , stepping down the DC voltage to obtain a working voltage.

[0079] S430 , rectifying and filtering the negative half-cycle signal to obtain a negative level voltage.

[0080] The implementation principle of the embodiment of this application is:

[0081] The negative half-cycle signal is sampled from the secondary coil of the transformer 1. After voltage division, the voltage signal is input into the comparison circuit 7 composed of a precision comparator. The comparison circuit 7 outputs a digital signal to the control circuit 8, that is, the MCU to generate an external interrupt. When the MCU detects the interrupt signal, it immediately executes the power-off time to complete the data storage operation. At this time, the output voltage can still ensure a stable output for about 2 seconds, ensuring the reliability of data storage in the event of a power outage.

[0082] The examples of this specific embodiment are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Identical components are represented by the same reference numerals. Therefore, any equivalent changes made based on the structure, shape, and principle of this application should be included in the scope of protection of this application.

Claims

1. A power-off detection circuit for an electric energy meter, comprising a transformer (1) connected to a power grid, characterized in that: include: Applied to electric energy meters, A switching power supply module (2) is connected between the primary coil of the transformer (1) and the power grid, and is used to detect whether a power outage occurs and change its own on / off state based on the detection result; A positive half-cycle sampling terminal (3) connected to the secondary coil of the transformer (1) for sampling the positive half-cycle signal output by the transformer (1) when the switching power supply module (2) is turned off; A negative half-cycle sampling terminal (4) is connected to the secondary coil of the transformer (1) and is used to sample the negative half-cycle signal output by the transformer (1) when the switching power supply module (2) is turned on; a signal processing circuit (5) connected to the positive half-cycle sampling terminal (3) and the negative half-cycle sampling terminal (4) to obtain the positive half-cycle signal and the negative half-cycle signal, and to process the positive half-cycle signal to obtain a working voltage, and also to process the negative half-cycle signal to obtain a negative level voltage; A voltage divider circuit (6) is connected to the signal processing circuit (5) to obtain the operating voltage and the negative level voltage, and is used to divide the operating voltage and the negative level voltage to obtain a sampling voltage; A comparison circuit (7) compares the sampled voltage with a preset voltage and generates a corresponding comparison signal according to the comparison result; A control circuit (8) is connected to the comparison circuit (7) to obtain the comparison signal, and judges whether there is a power failure according to the comparison signal, and executes a power failure event to complete the data storage operation when a power failure occurs; The processing of the positive half-cycle signal to obtain the working voltage includes: rectifying and filtering the positive half-cycle signal to obtain a DC voltage, and stepping down the DC voltage to obtain the working voltage; Processing the negative half cycle signal to obtain a negative level voltage includes: rectifying and filtering the negative half cycle signal to obtain a negative level voltage; The positive half-cycle sampling terminal (3) and the negative half-cycle sampling terminal (4) are connected in parallel.

2. The electric energy meter power-off detection circuit according to claim 1, characterized in that: It also includes a power grid filter (EMI) and a rectifier bridge circuit (9), wherein the power grid filter (EMI) is connected to the power grid, and one end of the rectifier bridge circuit (9) is connected to the power grid filter (EMI), and the other end is connected to the primary coil of the transformer (1).

3. The electric energy meter power-off detection circuit according to claim 1, characterized in that: The positive half-cycle sampling terminal (3) comprises a first diode (D1), the positive electrode of the first diode (D1) is connected to the eleventh pin of the transformer (1), and the negative electrode of the first diode (D1) is connected to the signal processing circuit (5); The negative half-cycle sampling terminal (4) includes a second diode (D2), the cathode of the second diode (D2) is connected to the eleventh pin of the transformer (1), and the anode of the second diode (D2) is connected to the signal processing circuit (5).

4. The electric energy meter power-off detection circuit according to claim 3, characterized in that: The signal processing circuit (5) comprises a first capacitor (C1) and a linear regulator (LDO), wherein the first capacitor (C1) is connected to the cathode and the twelfth pin of the first diode (D1), respectively; the first capacitor (C1) is used to filter the positive half-cycle signal to obtain a DC voltage; and the linear regulator (LDO) is connected to the first capacitor (C1) to step down the DC voltage to obtain the operating voltage.

5. The electric energy meter power-off detection circuit according to claim 3, characterized in that: The signal processing circuit (5) comprises a second capacitor (C2), one end of the second capacitor (C2) is connected to the positive electrode of the second diode (D2), and the other end is grounded, and the second capacitor (C2) is used to filter the negative half-cycle signal to obtain a negative level voltage.

6. The electric energy meter power-off detection circuit according to claim 4 or 5, characterized in that: The voltage divider circuit (6) comprises a first resistor (R1) and a second resistor (R2), one end of the first resistor (R1) is connected to the signal processing circuit (5) to receive the operating voltage, and the other end is connected to the second resistor (R2), the other end of the second resistor (R2) is connected to the signal processing circuit (5) to receive the negative level voltage, and a node between the first resistor (R1) and the second resistor (R2) is connected to the comparison circuit (7).

7. A method for detecting power failure of an electric energy meter, characterized in that: An electric energy meter power-off detection circuit according to any one of claims 1 to 6 comprises the following steps: Determining the on / off state of the switching power supply module (2); If the switching power supply module (2) is turned off, the positive half-cycle signal is sampled; If the switching power supply module (2) is turned on, the negative half-cycle signal is sampled; Performing signal processing on the positive half-cycle signal and the negative half-cycle signal to obtain a working voltage of the positive half-cycle signal after signal processing and a negative level voltage of the negative half-cycle signal after signal processing, respectively; Dividing the operating voltage and the negative level voltage to obtain a sampling voltage; Comparing the sampled voltage with a preset voltage to generate a corresponding comparison signal; determining whether a power outage occurs according to the comparison signal, and if a power outage occurs, executing a power outage event to complete the data storage operation; The signal processing of the positive half-cycle signal and the negative half-cycle signal comprises the following steps: Performing rectification and filtering operations on the positive half-cycle signal to obtain a DC voltage; Stepping down the DC voltage to obtain the operating voltage; Performing rectification and filtering operations on the negative half-cycle signal to obtain the negative level voltage; The positive half-cycle sampling terminal (3) and the negative half-cycle sampling terminal (4) are connected in parallel.

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