Metering circuit and electric energy meter

Abstract

The utility model provides a metering circuit and an electric energy meter. The metering circuit comprises a three-phase sampling circuit and a metering chip. Each phase sampling circuit comprises an isolation power supply circuit, a first sampling circuit, a digital isolation circuit and a second sampling circuit. The isolation power supply circuit provides an isolation power supply for the first sampling circuit, the first sampling circuit is used for realizing sampling of alternating current power supply phase current, and a digital isolation circuit is arranged between the first sampling circuit and the metering chip so as to realize electrical isolation between the first sampling circuit and the metering chip; the second sampling circuit is used for sampling the phase voltage of the AC power supply. The metering chip can meter the electric energy of the AC power supply based on the phase current and the phase voltage. According to the scheme provided by the utility model, high-precision, high-stability and small-size electric energy metering can be realized.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of electric energy measurement, especially to a metering circuit and an electric energy meter. BACKGROUND

[0002] With the rapid development of economy, the demand for electricity of various industries also increases accordingly, so the demand and technical requirements of electric energy meters also increase accordingly, especially the accuracy, anti-interference performance and other performances of electric energy meters are required.

[0003] At present, the electric energy meter is usually a mutual inductance type electric energy meter, which is based on the electromagnetic induction technology of a current transformer (CT) and realizes the measurement of large current through non-contact measurement.

[0004] However, the mutual inductance type electric energy meter has high cost, large size and is easily disturbed by external magnetic fields. UTILITY MODEL CONTENTS

[0005] The utility model provides a metering circuit and an electric energy meter to solve the problems of high cost, large size and easy disturbance by external magnetic fields of the mutual inductance type electric energy meter.

[0006] In a first aspect, the utility model provides a metering circuit, which comprises a three-phase sampling circuit and a metering chip. Each phase of the sampling circuit comprises an isolation power supply circuit, a first sampling circuit, a digital isolation circuit and a second sampling circuit. The isolation power supply circuit is connected with the first sampling circuit. The first sampling circuit is connected with the metering chip through the digital isolation circuit. The second sampling circuit is connected with the metering chip. The isolation power supply circuit is used to output an isolation voltage to the first sampling circuit. The first sampling circuit is used to collect an analog voltage signal at both ends of a manganese copper resistor and convert the analog voltage signal into a digital voltage signal. The voltage signal at both ends of the manganese copper resistor is used to determine a phase current signal of an alternating current power supply. The manganese copper resistor is connected in series in the line of each phase of the alternating current power supply. The digital isolation circuit is used to realize the electrical isolation between the first sampling circuit and the metering chip. The second sampling circuit is used to collect a phase voltage signal of the alternating current power supply. The metering chip is used to determine a digital phase current signal of the alternating current power supply based on the digital voltage signal and realize the electric energy measurement of the alternating current power supply based on the digital phase current signal and the phase voltage signal.

[0007] With reference to the first aspect, in a possible implementation manner of the first aspect, the isolated power supply circuit comprises: an input filter capacitor, a driving circuit, an isolation transformer, a rectifier circuit and an output filter capacitor; the input filter capacitor is configured to perform filter processing on an input power supply of the isolated power supply circuit; the driving circuit is configured to drive the isolation transformer to output an alternating voltage to the rectifier circuit; the rectifier circuit is configured to convert the alternating voltage into a direct voltage; and the output filter capacitor is configured to perform filter processing on the direct voltage to obtain the isolated voltage.

[0008] With reference to the first aspect, in a possible implementation manner of the first aspect, the first sampling circuit comprises: a filter circuit and an analog-to-digital conversion unit; the filter circuit is configured to perform filter processing on the analog voltage signal to obtain a target analog voltage signal; and the analog-to-digital conversion unit is configured to amplify the target analog voltage signal and convert the target analog voltage signal into the digital voltage signal.

[0009] With reference to the first aspect, in a possible implementation manner of the first aspect, the phase voltage signal is a differential signal; and the second sampling circuit comprises: a voltage dividing resistor circuit and a differential circuit; the voltage dividing resistor circuit is configured to divide the phase voltage signal of the alternating power supply to obtain a target phase voltage signal meeting input requirements of the metering chip; and the differential circuit is configured to convert the target phase voltage signal into a differential signal.

[0010] With reference to the first aspect, in a possible implementation manner of the first aspect, the first sampling circuit and the digital isolation circuit each further comprise: a clock circuit.

[0011] With reference to the first aspect, in a possible implementation manner of the first aspect, the phase voltage signal comprises: an analog phase voltage signal; and the metering circuit further comprises: a mode setting circuit configured to set a working mode of the metering chip, the working mode comprising: performing analog-to-digital conversion on the phase voltage signal to obtain a digital phase voltage signal, and implementing electric energy metering of the alternating power supply based on the digital phase current signal and the digital phase voltage signal.

[0012] With reference to the first aspect, in a possible implementation manner of the first aspect, the metering circuit further comprises: a reset circuit connected with the metering chip; the reset circuit is configured to output a reset signal to the metering chip to start the metering chip.

[0013] With reference to the first aspect, in a possible implementation manner of the first aspect, the metering circuit further comprises: a clock generation circuit connected with the metering chip; the clock generation circuit is configured to output a clock signal to the metering chip.

[0014] With reference to the first aspect, in a possible implementation manner, the metering circuit further includes a communication circuit, and the metering chip communicates with an external circuit through the communication circuit.

[0015] With reference to the first aspect, in a possible implementation manner, the metering circuit further includes a communication circuit, and the metering chip communicates with an external circuit through the communication circuit.

[0016] The utility model provides a kind of metering circuit and electric energy meter.The utility model designs a kind of metering circuit according to manganese copper resistance metering principle, and the metering circuit includes: three-phase sampling circuit and metering chip, and each phase sampling circuit includes isolation power supply circuit, first sampling circuit, digital isolation circuit and second sampling circuit.Isolation power supply circuit is used to provide isolation power supply for first sampling circuit, so that alternating current power supply and the power supply of metering circuit are mutually isolated, short circuit is avoided, and the operation safety of metering circuit is improved;First sampling circuit is used to realize the sampling of alternating current power supply phase current, and second sampling circuit is used to realize the sampling of alternating current power supply phase voltage, and metering chip can realize the electric energy metering of alternating current power supply based on phase current and phase voltage.Through being provided with digital isolation circuit between first sampling circuit and metering chip, the electrical isolation between first sampling circuit and metering chip is realized, so that the metering accuracy can be improved;In addition, the power supply ground of metering chip and the N line of alternating current power supply are connected together by being provided with digital isolation circuit, to reduce the voltage resistance requirement of digital isolation circuit, and the current on N line can be directly input into metering chip, so that the metering of current on N line can be directly realized, without providing independent isolation power supply circuit for N phase, and then cost can be reduced.In addition, isolation power supply circuit and digital isolation circuit are independently provided to form complete isolation system, and the volume of digital isolation circuit is smaller, so that the volume of metering circuit can be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A schematic system structure diagram of the metering circuit provided by the utility model is shown in Figure 1.

[0018] Figure 2 A schematic structure diagram of the isolation power supply circuit provided by the utility model is shown in Figure 2.

[0019] Figure 3 A schematic structure diagram of the first sampling circuit and the digital isolation circuit provided by the utility model is shown in Figure 3.

[0020] Figure 4 A schematic structure diagram of the second sampling circuit provided by the utility model is shown in Figure 4.

[0021] Figure 5 A schematic system structure diagram of another metering circuit provided by the utility model is shown in Figure 5. DETAILED DESCRIPTION

[0022] The technical solution of this utility model will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0023] To address the problems of high cost, large size, and susceptibility to external magnetic field interference in inductive energy meters, this invention provides a metering circuit and an energy meter. Based on the metering principle of manganese copper resistors, this invention utilizes their advantages such as high temperature stability, high measurement accuracy, excellent frequency characteristics and wide bandwidth response, no phase error, no magnetic saturation problems, and small size to design a metering circuit with high precision, high stability, and small size. The manganese copper resistor uses a manganese copper alloy as its material, and its metering principle is based on Ohm's law. When current flows through the manganese copper resistor, a voltage drop is generated. By measuring the voltage across the manganese copper resistor, the current flowing through it can be determined, thereby determining the energy value. The technical solution provided in this application can achieve high-precision, high-stability, and small-size energy metering, and also provides a new design method and technical approach for the application of manganese copper resistors in the field of energy meters.

[0024] The following is combined with Figures 1 to 5 The technical solution provided by this utility model will be described below.

[0025] Figure 1 This is a schematic system structure diagram of a metering circuit provided by the present invention. Figure 1 The metering circuit 100 shown includes a three-phase sampling circuit 110 and a metering chip 120. The metering circuit 100 is used to measure the electrical energy of a three-phase AC power supply.

[0026] like Figure 1 As shown, each phase sampling circuit in the three-phase sampling circuit includes: an isolation power supply circuit, a first sampling circuit, a digital isolation circuit, and a second sampling circuit. The isolation power supply circuit and the first sampling circuit are connected. The first sampling circuit is connected to the metering chip through the digital isolation circuit, and the second sampling circuit is connected to the metering chip.

[0027] The isolation power supply circuit is used to output an isolation voltage to the first sampling circuit so that the AC power supply and the working power supply of the metering circuit are isolated from each other, avoiding short circuits, enabling the metering circuit to work normally, and improving the operating safety of the metering circuit.

[0028] The first sampling circuit is configured to collect an analog voltage signal across the manganese-copper resistor and convert the analog voltage signal into a digital voltage signal. The voltage signal across the manganese-copper resistor is used to determine the phase current signal of the AC power supply, and the manganese-copper resistor is connected in series in the line of each phase of the AC power supply. As shown in Figure 1 The AC power supply is a three-phase four-wire system, such as the ABC three-phase and the center line N in the figure. The manganese-copper resistor is connected in series in the line of each phase of the AC power supply, or in other words, the manganese-copper resistor is connected in series in each phase line of the AC power supply. When the phase current signal of the AC power supply flows through the manganese-copper resistor, a voltage drop is generated, so that the phase current signal can be determined by measuring the voltage across the manganese-copper resistor. The first sampling circuit can be understood as a current sampling circuit.

[0029] The digital isolation circuit is configured to electrically isolate the first sampling circuit from the metering chip to reduce interference between the two and improve metering accuracy.

[0030] The second sampling circuit is configured to collect the phase voltage signal of the AC power supply. The second sampling circuit can be understood as a voltage sampling circuit.

[0031] The metering chip is configured to determine the digital phase current signal of the AC power supply based on the digital voltage signal, and to implement electric energy metering of the AC power supply based on the digital phase current signal and the phase voltage signal. For example, when the phase voltage signal collected by the second sampling circuit is an analog phase voltage signal, the metering chip can convert the analog phase voltage signal into a digital phase voltage signal, so as to determine the electric energy of the AC power supply based on the digital phase current signal and the digital phase voltage signal.

[0032] Taking the A-phase sampling circuit in Figure 1 For example, MT1 is a manganese-copper resistor connected in series in the A-phase line of the AC power supply, and the A-phase current signal Ia generates an analog voltage signal Via when passing through MT1 and inputs the analog voltage signal Via into the first sampling circuit A. The first sampling circuit A converts the analog voltage signal Via into a digital voltage signal Dia, and the digital voltage signal Dia is input into the metering chip after being converted into a digital voltage signal Diia by the digital isolation circuit A. In addition, the A-phase voltage signal is input into the metering chip after being converted into a voltage signal Vva by the second sampling circuit A. The metering chip can determine the A-phase current digital signal based on the digital voltage signal Diia, and implement electric energy metering of the AC power supply based on the A-phase current digital signal and the voltage signal Vva, such as determining the A-phase electric energy, power, effective value and other data.

[0033] Correspondingly, MT2 is a manganin resistor connected in series with the B-phase AC power supply line. The B-phase current signal Ib passes through MT2 and generates an analog voltage signal Vib, which is then input to the first sampling circuit B. The first sampling circuit B converts the analog voltage signal Vib into a digital voltage signal Dib. The digital voltage signal Dib passes through the digital isolation circuit B to generate a digital voltage signal Diib, which is then input to the metering chip. Additionally, the B-phase voltage signal passes through the second sampling circuit B to obtain a voltage signal Vvb, which is then input to the metering chip. The metering chip can determine the B-phase current digital signal based on the digital voltage signal Diib, and use the B-phase current digital signal and voltage signal Vvb to perform AC power metering, such as determining B-phase energy, power, and RMS value.

[0034] Correspondingly, MT3 is a manganin resistor connected in series with the C-phase AC power supply line. The C-phase current signal Ic passes through MT3 to generate an analog voltage signal Vic, which is then input to the first sampling circuit C. The first sampling circuit C converts the analog voltage signal Vic into a digital voltage signal Dic. The digital voltage signal Dic passes through the digital isolation circuit C to generate a digital voltage signal Diic, which is then input to the metering chip. Additionally, the C-phase voltage signal passes through the second sampling circuit C to obtain a voltage signal Vvc, which is then input to the metering chip. The metering chip can determine the C-phase current digital signal based on the digital voltage signal Diic, and use the C-phase current digital signal and the voltage signal Vvc to perform AC power metering, such as determining C-phase energy, power, and RMS value.

[0035] In the technical solution provided by this utility model, a digital isolation circuit is set between the first sampling circuit and the metering chip, so that the power ground of the metering chip is connected to the N line of the AC power supply. This reduces the withstand voltage requirement of the digital isolation circuit, and the current on the N line can be directly input into the metering chip, thereby directly realizing the measurement of the current on the N line without the need to provide a separate isolation power supply circuit for the N phase, thus reducing costs. In addition, by independently setting up the isolation power supply circuit and the digital isolation circuit to form a complete isolation system, and the small size of the digital isolation circuit, the size of the metering circuit can be reduced.

[0036] Figure 2 This is a schematic structural diagram of an isolated power supply circuit provided by this utility model. It should be noted that... Figure 2 The isolated power supply circuit shown is for Figure 1 The exemplary description of the isolation power supply circuit is not intended to limit the technical solution of this application. It should be understood that this application relates to a three-way isolation power supply circuit, each of which is used to power the first sampling circuit in each phase sampling circuit. Figure 2 Only one isolated power supply circuit is shown, and Figure 2The following example illustrates an isolated power supply circuit with an input voltage of 3.3V and an output isolation voltage of 3.3V.

[0037] like Figure 2 As shown, the isolation power supply circuit includes: an input filter capacitor (capacitor C1 in the figure), a drive circuit (U1 in the figure), an isolation transformer (T1 in the figure), a rectifier circuit (diodes D1 and D2 in the figure), and an output filter capacitor (capacitor C2 in the figure). It can be seen that the isolation transformer has a center tap. Resistor R1 is a dummy load for the isolation voltage.

[0038] The input filter capacitor is used to filter the input power supply of the isolation power supply circuit to improve the stability of the input power supply.

[0039] A drive circuit is used to drive the isolation transformer to output AC voltage to the rectifier circuit. For example, the drive circuit may include an internal oscillator and two switching transistors. The internal oscillator generates a high-frequency switching frequency, and the outputs of the two switching transistors (VD1 and VD2 in the figure) can alternately switch based on the high-frequency switching frequency, thereby generating AC voltages with opposite phases across the primary windings of the isolation transformer (Np1 and Np2 in the figure). The isolation transformer can then couple the AC voltage to the secondary side and output it to the rectifier circuit. Optionally, the high-frequency switching frequency can be 420 kHz to meet electromagnetic compatibility (EMC) requirements such as low noise and low electromagnetic interference (EMI).

[0040] A rectifier circuit is used to convert the AC voltage output from the isolation transformer into a DC voltage. Optionally, the amplitude of the DC voltage can be related to the turns ratio of the primary and secondary windings of the isolation transformer.

[0041] The output filter capacitor is used to filter the DC voltage to obtain a stable isolation voltage.

[0042] Figure 3 This is a schematic structural diagram of a first sampling circuit and a digital isolation circuit provided by this utility model. It should be noted that... Figure 3 The first sampling circuit shown is for Figure 1 The exemplary description of the first sampling circuit is not intended to limit the technical solution of this application. Figure 3 Only one first sampling circuit is shown.

[0043] like Figure 3 As shown, the first sampling circuit includes a filter circuit and an analog-to-digital conversion unit.

[0044] The filtering circuit is configured to filter an analog voltage signal across the manganese-copper resistance to obtain a target analog voltage signal, thereby improving stability of the analog voltage signal. Figure 3 The filtering circuit includes a resistor R3, a capacitor C3, a resistor R4 and a capacitor C4.

[0045] The analog-to-digital conversion (ADC) unit is configured to amplify the target analog voltage signal and convert the analog voltage signal into a digital voltage signal.

[0046] In the utility model, the first sampling circuit and the digital isolation circuit can each include a clock circuit.

[0047] The analog-to-digital conversion unit is U2 in Figure 3 It can be seen that the analog-to-digital conversion unit includes multiple interfaces. The AVDD interface is configured to receive an isolation voltage, the RST interface is configured to receive a reset signal, and the reset signal is configured to start or restart the analog-to-digital conversion unit. The V1P interface and the V1N interface are configured to receive the target analog voltage signal. The REFV interface is configured to input a reference voltage, and the reference voltage is a reference for conversion accuracy in the process of converting the analog voltage signal into the digital voltage signal. The GND interface is configured to be grounded. The ADC1 interface is configured to output the digital voltage signal Dia to the digital isolation circuit. The CLK interface is configured to receive a clock signal.

[0048] The digital isolation circuit is U3 in Figure 3 The VDD1 interface in the digital isolation circuit is configured to receive the isolation voltage, the VDD2 interface is configured to receive a working power supply, the VIA interface is configured to receive the digital voltage signal Dia, the VOA interface is configured to output a digital voltage signal Diia, the VIB interface is configured to receive a clock signal CLK1 from the metering chip, and the VOB interface is configured to output the clock signal to the analog-to-digital conversion unit, so that the clock is homologous in the metering process, and metering calculation is facilitated. The GND1 interface and the GND2 interface are configured to be grounded.

[0049] The working principle of the first sampling circuit is described below by taking the A phase as an example.

[0050] The A-phase current of the AC power supply flows through the manganese-copper resistor MT1, generating analog voltage signals, as shown in the differential signals M1+ and M1- in the figure. The filtering circuit filters the differential signals M1+ and M1- to obtain the target analog voltage signal, as shown in the differential signals IAP and IAN in the figure. The analog-to-digital conversion unit amplifies the differential signals IAP and IAN and converts them into a digital voltage signal Dia. The digital voltage signal Dia is then processed by a digital isolation circuit to generate Diia before being input to the metering chip. It should be noted that M1+ and M1- can be understood as... Figure 1 The differential signal of the analog voltage signal Via.

[0051] It should be noted that the first sampling circuit may also include other circuits, and this utility model does not impose specific limitations on this. For example, the first sampling circuit may also include: a bias resistor (such as...) Figure 3 The first sampling circuit may also include a reset circuit (resistor R2 in the figure) to adjust the voltage range of the differential signals M1+ and M1- for subsequent processing by the analog-to-digital conversion unit. The reset circuit outputs a reset signal to the analog-to-digital conversion unit. The first sampling circuit may also include a power supply filtering circuit (capacitors C6, C7, and C8 in the figure). Capacitors C6 and C7 filter the reference voltage in the analog-to-digital conversion unit to obtain a stable reference voltage. Capacitor C8 filters the isolation voltage input to the digital isolation circuit.

[0052] Figure 4 This is a schematic structural diagram of a second sampling circuit provided by this utility model. It should be noted that... Figure 4 The second sampling circuit shown is for Figure 1 The exemplary description of the second sampling circuit is not intended to limit the technical solution of this application. It should be noted that... Figure 4 The second sampling circuit in the A-phase sampling circuit is shown.

[0053] like Figure 4 As shown, the second sampling circuit includes a voltage divider resistor circuit and a differential circuit.

[0054] The voltage divider resistor circuit is used to divide the phase voltage signal of the AC power supply to obtain the target phase voltage signal that meets the input requirements of the metering chip. The voltage divider resistor circuit includes resistors R6, R7, R8, and R9 as shown in the figure. The target phase voltage signal is the voltage signal VAP across resistor R9.

[0055] A differential circuit is used to convert the target phase voltage signal into a differential signal. The differential circuit is resistor R10 in the figure. The voltage signals VAN and VAP across resistor R10 constitute a differential signal. VAN and VAP can be understood as Figure 1 a differential signal of the medium voltage signal Vva.

[0056] After the differential signal is generated, the second sampling circuit inputs the differential signal to the metering chip.

[0057] It should be noted that the second sampling circuit can also include other circuits, and the utility model does not make specific limitations thereon. For example, the second sampling circuit can also include a filter capacitor, such as Figure 4 capacitor C9 and capacitor C10. Capacitor C9 is used to filter process the differential signal VAP to improve the stability of VAP. Capacitor C10 is used to filter process the differential signal VAN to improve the stability of VAN.

[0058] Figure 5 Another schematic system structure diagram of the metering circuit provided by the utility model is shown in the figure. Figure 5 The metering circuit shown in the figure includes a metering chip, such as U4 in the figure.

[0059] Optionally, the metering circuit can also include a power supply filter circuit, a reset circuit, a clock generation circuit and a communication circuit. Among them, the power supply filter circuit, the reset circuit, the clock generation circuit and the communication circuit are connected with the metering chip.

[0060] The power supply filter circuit is capacitor C11, capacitor C12, capacitor C13, capacitor C14, capacitor C16, capacitor C19, capacitor C20 and capacitor C21 in the figure. Figure 5 Among them, capacitor C11, capacitor C12, capacitor C16 and capacitor C21 are used for filter processing of the input power supply (such as Vin3.3V in the figure). Capacitor C13 and capacitor C14 are used for filter processing of the reference voltage in the metering chip to improve the stability of the reference voltage. It should be noted that if the phase voltage signal collected by the second sampling circuit is an analog phase voltage signal, the metering chip needs to convert the analog phase voltage signal into a digital phase voltage signal to realize the electric energy metering of the alternating current power supply. The reference voltage is the reference for the conversion accuracy in the process of converting the analog phase voltage signal into the digital phase voltage signal. Capacitor C19 and capacitor C20 are used for filter processing of the output voltage of the voltage stabilizing module in the metering chip. The output voltage of the voltage stabilizing module serves as the core power supply of the metering chip to provide voltage for the internal circuit of the metering chip.

[0061] The reset circuit is resistor R11 and capacitor C15 in the figure. Figure 5 The reset circuit is used to provide a reset signal to the metering chip to start / restart the metering chip. The reset signal can be a low-level signal.

[0062] The clock generating circuit is, for example, X1, capacitor C17 and capacitor C18 in Figure 5 The clock generating circuit is used to output a clock signal to the metering chip. The metering chip can output the clock signal CLK1 to the digital isolation circuit through the CKO interface to provide a synchronous clock.

[0063] The communication circuit is, for example, the communication lines of SDI, SDO, SCLK, SCS and the like in Figure 5 The metering chip can communicate with an external control circuit (not shown in the figure) through a serial peripheral interface (SPI). For example, the metering chip can perform SPI communication through the communication lines of SDI, SDO, SCLK, SCS and the like, such as setting and reading related register data, setting the working mode of the metering chip, and obtaining metering data and the like.

[0064] In some implementations, the metering circuit can further include a mode setting circuit (not shown in the figure), which can be connected with the metering chip. The mode setting circuit is used to set the working mode of the metering chip, and the working mode includes: when the phase voltage signal is an analog phase voltage signal, performing analog-digital conversion on the phase voltage signal to obtain a digital phase voltage signal, and implementing electric energy metering of the alternating current power supply based on the digital phase current signal and the digital phase voltage signal.

[0065] In the utility model, the metering chip can receive the mode setting parameters input by the analog setting circuit through the MODE interface and the PM interface. For example, when the parameter received by the MODE interface is 1 and the parameter received by the PM interface is 0, it can be considered that the working mode of the metering chip is the sampling current external ADC mode, that is, the digital phase current signal of the alternating current power supply is determined by the signal collected by the first sampling circuit, and the digital phase voltage signal of the alternating current power supply is determined by the metering chip performing analog-digital conversion on the phase voltage signal collected by the second sampling circuit.

[0066] In some implementations, the phase voltage signal collected by the second sampling circuit can be a digital phase voltage signal, and the working mode of the metering chip is the sampling current external ADC and sampling voltage external ADC mode, that is, the metering chip does not need to perform analog-digital conversion on the phase voltage signal collected by the second sampling circuit.

[0067] As shown in Figure 5 The differential signals of the three-phase voltage signals are input to the VAP interface, the VAN interface, the VBP interface, the VBN interface, the VCP interface and the VCN interface of the metering chip in sequence, the three-phase digital voltage signals are input to the IA-DIN interface, the IB-DIN interface and the IC-DIN interface of the metering chip in sequence, and the metering chip can perform electric energy, power and effective value calculation according to the input signals.

[0068] The utility model also provides a kind of electric energy meter, and the electric energy meter includes the metering circuit in the preceding described embodiment. Optionally, electric energy meter can also include control circuit.

[0069] In the description of the utility model, it needs to be explained that the description for indicating orientation or positional relation in the specification is based on the orientation or positional relation shown in the drawing, and is only for the convenience of describing the utility model and simplifying the description, and is not for indicating or implying that the indicated device or element must have specific orientation, be constructed and operated in specific orientation, so it cannot be understood as the limitation of the utility model.

[0070] In the description of the utility model, it needs to be explained that the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0071] In the description of the utility model, it needs to be explained that, unless otherwise explicitly specified and limited, the term "connection" should be understood broadly, for example, it can be fixed connection, can be detachable connection, or integrally connected;It can be electrically connected;It can be directly connected, or indirectly connected through intermediate medium, it can be the communication inside two elements. For ordinary skilled in the art, the specific meaning of the above-mentioned terms in the utility model can be understood according to specific circumstances. In addition, the technical features involved in the above-described different embodiments of the utility model can be combined with each other as long as there is no conflict.

[0072] It needs to be emphasized that: the above is only the preferred embodiment of the utility model, and is not for limiting the utility model in any form, any simple modification, equivalent change and modification made according to the technical essence of the utility model to the above embodiment, still belongs to the scope of the technical scheme of the utility model.

Claims

1. A metering circuit, characterized by The method comprises the following steps: a three-phase sampling circuit and a metering chip; The sampling circuit of each phase comprises an isolation power supply circuit, a first sampling circuit, a digital isolation circuit, and a second sampling circuit, the isolation power supply circuit and the first sampling circuit are connected, the first sampling circuit is connected with the metering chip through the digital isolation circuit, and the second sampling circuit is connected with the metering chip; The isolation power supply circuit is used for outputting an isolation voltage to the first sampling circuit; The first sampling circuit is used for collecting an analog voltage signal across a manganese-copper resistor, and converting the analog voltage signal into a digital voltage signal, the voltage signal across the manganese-copper resistor is used for determining a phase current signal of an alternating current power supply, and the manganese-copper resistor is connected in series in a line of each phase of the alternating current power supply; The digital isolation circuit is used for realizing electrical isolation between the first sampling circuit and the metering chip; The second sampling circuit is used for collecting a phase voltage signal of the alternating current power supply; The metering chip is used for determining a digital phase current signal of the alternating current power supply based on the digital voltage signal, and realizing electric energy metering of the alternating current power supply based on the digital phase current signal and the phase voltage signal.

2. The metering circuit of claim 1, wherein, The isolation power supply circuit comprises an input filter capacitor, a driving circuit, an isolation transformer, a rectifier circuit, and an output filter capacitor; The input filter capacitor is used for filtering an input power supply of the isolation power supply circuit; The driving circuit is used for driving the isolation transformer to output an alternating voltage to the rectifier circuit; The rectifier circuit is used for converting the alternating voltage into a direct current voltage; The output filter capacitor is used for filtering the direct current voltage to obtain the isolation voltage.

3. The metering circuit of claim 1, wherein, The first sampling circuit comprises a filter circuit and an analog-to-digital conversion unit; The filter circuit is used for filtering the analog voltage signal to obtain a target analog voltage signal; The analog-to-digital conversion unit is used for amplifying the target analog voltage signal and converting the target analog voltage signal into the digital voltage signal.

4. The metering circuit of claim 1, wherein, The phase voltage signal is a differential signal; The second sampling circuit comprises a voltage dividing resistor circuit and a differential circuit; The voltage dividing resistor circuit is used for dividing the phase voltage signal of the alternating current power supply to obtain a target phase voltage signal meeting the input requirement of the metering chip; The differential circuit is used for converting the target phase voltage signal into a differential signal.

5. The metering circuit of any one of claims 1 to 4, wherein, The first sampling circuit and the digital isolation circuit both further comprise a clock circuit.

6. The metering circuit of claim 1, wherein, The phase voltage signal comprises an analog phase voltage signal; The metering circuit further comprises a mode setting circuit, the mode setting circuit is used for setting a working mode of the metering chip, and the working mode comprises: performing analog-to-digital conversion on the phase voltage signal to obtain a digital phase voltage signal, and realizing electric energy metering of the alternating current power supply based on the digital phase current signal and the digital phase voltage signal.

7. The metering circuit of claim 1, wherein, The metering circuit further comprises a reset circuit, the reset circuit is connected with the metering chip; The reset circuit is used for outputting a reset signal to the metering chip to start the metering chip.

8. The metering circuit of claim 1, wherein, The metering circuit further comprises a clock generation circuit connected with the metering chip. The clock generation circuit is configured to output a clock signal to the metering chip.

9. The metering circuit of claim 1, wherein, The metering circuit further comprises a communication circuit through which the metering chip communicates with an external circuit.

10. An electric energy meter, characterized by A metering circuit as claimed in any one of claims 1 to 9.

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