CN203422410U - Diverter current sampling circuit of smart electric meter - Google Patents
Diverter current sampling circuit of smart electric meter Download PDFInfo
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- CN203422410U CN203422410U CN201320558857.6U CN201320558857U CN203422410U CN 203422410 U CN203422410 U CN 203422410U CN 201320558857 U CN201320558857 U CN 201320558857U CN 203422410 U CN203422410 U CN 203422410U
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Abstract
Disclosed is a diverter current sampling circuit of a smart electric meter. The circuit structure is simple, packaging is convenient, and production costs are low. The smart electric meter includes an MCU; the diverter current sampling circuit comprises a diverter CM, a resistor R1, a resistor R2, a capacitor C1, a capacitor C2, an analog switch K1, an analog switch K2, an analog switch K3 and an analog switch K4; the control terminals of the analog switch K1 and the analog switch K3 receive control signals of one I/O port of the MCU simultaneously; and the control terminals of the analog switch K2 and the analog switch K4 receive control signals of the other I/O port of the MCU simultaneously. According to the diverter current sampling circuit, the on-state resistance characteristic of an analog switch chip is smartly utilized, a novel technology scheme based on segment acquisition is provided, the circuit structure is simple, not much change for a printed board is required, the area of the printed board is minimized, and an electromagnetic compatibility problem caused by the additional circuit is prevented as much as possible. The diverter current sampling circuit is novel and unique, application is simple, and costs are low.
Description
Technical field
The utility model relates to the electric energy metrical field of electric energy meter, relates in particular to the improvement to family, office, industrial intelligent electric meter metering current sample circuit.
Background technology
Intelligent electric energy meter, as the measuring products of electric energy metrical and charge calculation, requires product to have and stablizes accurate metering performance, guarantees that electricity consumption, power supply both sides' interests are without prejudice.The range of current of electric energy meter requires to improve constantly at present, and what at present conventional scheme adopted is to adopt wide-range computation chip or SOC (System on Chip) scheme.In prior art, shunt current sampling circuit as shown in Figure 6, in prior art, transformer current sample circuit as shown in Figure 7, restriction due to metered chip dynamic range, all can not guarantee the high-acruracy survey in whole range of current, cannot meet super-large current and minimum electric current and carry out the requirement of accurately measuring simultaneously.For this problem, Chinese patent CN102809678 A, Chinese patent CN102426290 A have proposed improvement method for designing, but implementation method is more complicated all, also unrealistic in actual use, mainly contain the following aspects reason: (1) is because State Grid Corporation of China has formulated the pattern standard of various electric energy meters, the external dimensions of electric energy meter and shape can not change, and therefore can not allow increases too many circuit, and above-mentioned patent all exists this problem; (2) because State Grid Corporation of China carries out electric energy meter uniform bidding buying, by the bid and purchase of 4 years, the procurement price of electric energy meter is basicly stable, the cost that increases several yuans can cause because bid price is too high, cannot get the bid or bid price suitably make acceptance of the bid after profitless, therefore can not allow increases too many circuit, and above-mentioned patent equally all exists this problem; (3) before voltage sample and current sampling circuit, increasing too many circuit and not only may reduce sampling precision on the contrary, and may also can bring the problem of electromagnetic compatibility aspect, equally all there is this problem in above-mentioned patent; (4) because the metering units current acquisition passage of MCU in computation chip or SOC scheme is limited, therefore also not allowing to carry out by size segmentation collection to improve acquisition precision by different acquisition port current, just there is this problem in Chinese patent CN102426290 A.
Summary of the invention
The utility model, in order to overcome above deficiency, has proposed a kind of circuit structure simple, is convenient to encapsulation, the shunt current sampling circuit of the intelligent electric meter that production cost is low.
The technical solution of the utility model is: described intelligent electric meter comprises MCU, in described MCU, establish differential amplifier, comprise shunt CM, resistance R 1, resistance R 2, capacitor C 1, capacitor C 2, analog switch K1, analog switch K2, analog switch K3 and analog switch K4;
Described shunt CM has shunt interface one and shunt interface two, the import of described shunt interface one rear portion connecting analog K switch 1, the outlet of described analog switch K1 connects respectively described resistance R 1 and analog switch K2, and described resistance R 1 outlet connects respectively the positive input terminal of capacitor C 1 and differential amplifier; The import of described shunt interface two rear portion connecting analog K switch 3, the outlet of described analog switch K3 connects respectively described resistance R 2 and analog switch K4, and described resistance R 2 outlets connect respectively capacitor C 2 and differential amplifier negative input end;
Described analog switch K2 is connected with the outlet of analog switch K4; The outlet of described capacitor C 1 and capacitor C 2 is connected and ground connection;
The control end of described analog switch K1 and analog switch K3 receives an I/O mouth control signal of described MCU to control break-make simultaneously; The control end of described analog switch K2 and analog switch K4 receives another I/O mouth control signal of MCU to control break-make simultaneously.
The value of described resistance R 1 and resistance R 2 is 100-1000 Ω, and the value of capacitor C 1 and capacitor C 2 is 33-100nF, and the conducting resistance of analog switch K1, analog switch K2, analog switch K3 and analog switch K4 is 20-25 Ω.
The utility model utilizes the on-resistance characteristics of analog switch chip cleverly, has formed the technical scheme that a kind of new segmentation gathers.While being applied to common electric energy meter, namely having increased by 1 four-way bidirectional analog switch, is all conventional device, even purchase by the acceptance of the bid quantity of 100,000, and every cost that also only needs to increase by 0.5 yuan of left and right.If be applied to single-phase intelligent electric energy meter, namely increased by 1 four-way bidirectional analog switch, be all conventional device, even purchase by the acceptance of the bid quantity of 100,000, every cost that also only needs to increase by 1 yuan of left and right.Meanwhile, because circuit structure is simple, also do not need printed board to change too much, both reduced the area size of printed board as far as possible, also maximum possible has avoided due to the electromagnetic compatibility problem that increases circuit generation.The utility model is novel unique, implements simply, and cost is lower.
Accompanying drawing explanation
Fig. 1 is intelligent electric meter functional block diagram,
Fig. 2 is the functional structure chart of MCU chip,
Fig. 3 is shunt current sampling circuit in the utility model,
Fig. 4 is shunt current sampling circuit in prior art.
Specific embodiments
As Figure 1-3, described intelligent electric meter comprises MCU to the utility model, in described MCU, establishes differential amplifier, comprises shunt CM, resistance R 1, resistance R 2, capacitor C 1, capacitor C 2, analog switch K1, analog switch K2, analog switch K3 and analog switch K4;
Described shunt CM has shunt interface one and shunt interface two, the import of described shunt interface one rear portion connecting analog K switch 1, the outlet of described analog switch K1 connects respectively described resistance R 1 and analog switch K2, and described resistance R 1 outlet connects respectively the positive input terminal of capacitor C 1 and differential amplifier; The import of described shunt interface two rear portion connecting analog K switch 3, the outlet of described analog switch K3 connects respectively described resistance R 2 and analog switch K4, and described resistance R 2 outlets connect respectively capacitor C 2 and differential amplifier negative input end;
Described analog switch K2 is connected with the outlet of analog switch K4; The outlet of described capacitor C 1 and capacitor C 2 is connected and ground connection;
The control end of described analog switch K1 and analog switch K3 receives an I/O mouth control signal of described MCU to control break-make simultaneously; The control end of described analog switch K2 and analog switch K4 receives another I/O mouth control signal of MCU to control break-make simultaneously.
The value of described resistance R 1 and resistance R 2 is 100-1000 Ω, and the value of capacitor C 1 and capacitor C 2 is 33-100nF, and the conducting resistance of analog switch K1, analog switch K2, analog switch K3 and analog switch K4 is 20-25 Ω.
Analog switch chip is selected to follow following principle: (1) chip power adopts existing electric energy meter MCU power supply, because increasing analog switch chip, does not additionally increase power supply on the one hand, is also can control analog switch for MCU on the other hand; (2) analog switch encapsulation is as far as possible little, to reduce as far as possible PCB(circuit board) area; (3) analog switch conducting resistance resistance and variation with temperature thereof will reduce the impact on current acquisition precision as far as possible.
Further illustrate principle of work of the present utility model below:
As shown in Figure 4, the voltage that electric current produces on shunt is sent into respectively the two ends of computation chip current sample passage differential amplifier after by R1, C1 and R2, C2 low-pass filtering to general shunt current sampling circuit.The resistance of general R1 and R2 is 150 Ω, and the capacitance of C1 and C2 is 47nF.Because shunt resistance is fixed, be therefore difficult to take into account the measuring accuracy of very big electric current and minimum electric current simultaneously.
Shunt current sampling circuit after improvement as shown in Figure 3.Before low-pass filter, install 4 passage bidirectional analog switch chips additional.Analog switch chip is selected to follow following principle: (1) chip power adopts existing electric energy meter MCU power supply, because increasing analog switch chip, does not additionally increase power supply on the one hand, is also can control analog switch for MCU on the other hand; (2) analog switch encapsulation is as far as possible little, to reduce as far as possible the area of PCB; (3) analog switch conducting resistance resistance and variation with temperature thereof will reduce the impact on current acquisition precision as far as possible.According to above principle, the present embodiment is chosen the MC74LVX4066 four-way bidirectional analog switch chip of ON company, is encapsulated as TSSOP-14, is also a kind of conventional chip.During+5V Power supply, in the time of-55 ℃～25 ℃, conducting resistance is 20 Ω, and when 85 ℃ of <, conducting resistance is 25 Ω, and when 125 ℃ of <, conducting resistance is 30 Ω.Because the electric energy meter limit of working temperature is-40 ℃～70 ℃, so the conducting resistance of electric energy meter when work MC74LVX4066 is between 20 Ω～25 Ω.
Four passage K1, K2 of four-way bidirectional analog switch, K3, the K4 connection in circuit are as shown in Figure 3.K1 is connected with resistance R 1 with shunt one end respectively; K3 is connected with resistance R 2 with the shunt other end respectively; K2 one end is connected with R1 with K1, and the other end is connected with K4; K4 one end is connected with R2 with K3, and the other end is connected with K2.The control end of K1, K3 is connected, and receives an I/O mouth control signal of MCU to control break-make; The control end of K2, K4 is connected, and receives another I/O mouth control signal of MCU to control break-make.
Adopt Fig. 3 shunt current sample to improve the principle of work of circuit.The I/O that MCU controls K1 and K3 exports high level all the time, and K1 and K3 are all in closure state.The threshold Ith that configuration switch state switches, when actual current is switched by MCU control simulation switch during higher or lower than Ith.(1) the I/O output low level of MCU control K2 and K4 when electric current is less than Ith, K2 and K4 are in off-state.The conducting resistance of analog switch is between 20 Ω～25 Ω, the resistance of differential amplifier input end low-pass filter is between 170 Ω～175 Ω, compare and be more or less the same with original 150 Ω, therefore the phase place causing after filtering is lagged behind little, with before improvement project during electric energy meter calibration phase correction parameter compare, during electric energy meter calibration, do not need phase correction parameter to do larger change, and the resistance that can increase R1 and R2 is ignored it.Meanwhile, owing to adopting two passages of same analog switch, therefore no matter how temperature changes, and the conducting resistance of K1 and K3 is all almost consistent, therefore guarantees the circuit balancing of differential amplifier two input ends completely.(2) the I/O output high level of MCU control K2 and K4 when electric current is greater than Ith, K2 and K4 are in closure state.The first, the electric current of differential amplifier input end is approximately 0, so sampling resistor is that shunt resistance is in parallel with the resistance in series of K1, K2, K3 and K4.Because the conducting resistance of analog switch is between 20 Ω～25 Ω, thus the resistance in series of K1, K2, K3 and K4 between 80 Ω～100 Ω, and the resistance of shunt is 250 μ Ω, the Current calculation error therefore causing due to analog switch in parallel is ignored.Second, the voltage of collecting unit differential amplifier collection is the input terminal voltage of R1 and R2, also be the voltage at K2 and K4 two ends, because the conducting resistance of K1, K2, K3 and K4 is equal, and also keep equal during temperature change, therefore no matter under which kind of temperature conditions, sampling voltage is guaranteed for shunt gathers 0.5 times of voltage, as long as MCU knows that now to gather voltage be 0.5 times and carries out corresponding amplification and process.The 3rd, the input voltage of differential amplifier is the input terminal voltage of R1 and R2, the resistance of input end low-pass filter is still R1 and R2, the same with original sample circuit resistance, therefore compare with primary circuit and can not cause filtered phase place to lag behind, during electric energy meter calibration, phase correction parameter is the same, and the circuit balancing of differential amplifier two input ends is without any change simultaneously.
From analyzing above, the scheme that the utility model adopts provides the easy embodiment of a raising galvanometer accuracy of measurement.If be applied to common electric energy meter, namely increased by 1 four-way bidirectional analog switch and greatly saved cost of products.Meanwhile, because circuit structure is simple, also do not need printed board to change too much, both reduced the area size of printed board as far as possible, also maximum possible has avoided due to the electromagnetic compatibility problem that increases circuit generation.
Claims (2)
1. the shunt current sampling circuit of intelligent electric meter, described intelligent electric meter comprises MCU, in described MCU, establish differential amplifier, it is characterized in that, comprise shunt CM, resistance R 1, resistance R 2, capacitor C 1, capacitor C 2, analog switch K1, analog switch K2, analog switch K3 and analog switch K4;
Described shunt CM has shunt interface one and shunt interface two, the import of described shunt interface one rear portion connecting analog K switch 1, the outlet of described analog switch K1 connects respectively described resistance R 1 and analog switch K2, and described resistance R 1 outlet connects respectively the positive input terminal of capacitor C 1 and differential amplifier; The import of described shunt interface two rear portion connecting analog K switch 3, the outlet of described analog switch K3 connects respectively described resistance R 2 and analog switch K4, and described resistance R 2 outlets connect respectively capacitor C 2 and differential amplifier negative input end;
Described analog switch K2 is connected with the outlet of analog switch K4; The outlet of described capacitor C 1 and capacitor C 2 is connected and ground connection;
The control end of described analog switch K1 and analog switch K3 receives an I/O mouth control signal of described MCU to control break-make simultaneously; The control end of described analog switch K2 and analog switch K4 receives another I/O mouth control signal of MCU to control break-make simultaneously.
2. the shunt current sampling circuit of intelligent electric meter according to claim 1, it is characterized in that, the value of described resistance R 1 and resistance R 2 is 100-1000 Ω, the value of capacitor C 1 and capacitor C 2 is 33-100nF, and the conducting resistance of analog switch K1, analog switch K2, analog switch K3 and analog switch K4 is 20-25 Ω.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201320558857.6U CN203422410U (en) | 2013-09-09 | 2013-09-09 | Diverter current sampling circuit of smart electric meter |
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| CN201320558857.6U CN203422410U (en) | 2013-09-09 | 2013-09-09 | Diverter current sampling circuit of smart electric meter |
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| CN203422410U true CN203422410U (en) | 2014-02-05 |
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| CN201320558857.6U Expired - Fee Related CN203422410U (en) | 2013-09-09 | 2013-09-09 | Diverter current sampling circuit of smart electric meter |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109324307A (en) * | 2018-09-02 | 2019-02-12 | 青岛鼎信通讯科技有限公司 | A kind of electric energy meter Hz noise counteracting method based on PCB |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109324307A (en) * | 2018-09-02 | 2019-02-12 | 青岛鼎信通讯科技有限公司 | A kind of electric energy meter Hz noise counteracting method based on PCB |
| CN109324307B (en) * | 2018-09-02 | 2022-02-08 | 青岛鼎信通讯科技有限公司 | Electric energy meter power frequency interference cancellation method based on PCB |
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| Date | Code | Title | Description |
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| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20140205 Termination date: 20150909 |
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| EXPY | Termination of patent right or utility model |