CN214953745U

CN214953745U - Non-isolated voltage sampling circuit, voltage sampling system and electric quantity metering device

Info

Publication number: CN214953745U
Application number: CN202120876383.4U
Authority: CN
Inventors: 罗国发; 胡广江; 沈海燕
Original assignee: SHENZHEN HEGUANG MEASUREMENT CONTROL TECHNOLOGY CO LTD
Current assignee: SHENZHEN HEGUANG MEASUREMENT CONTROL TECHNOLOGY CO LTD
Priority date: 2021-04-26
Filing date: 2021-04-26
Publication date: 2021-11-30
Anticipated expiration: 2031-04-26

Abstract

The utility model relates to and belongs to the technical field of electronic circuit, a non-isolation voltage sampling circuit, voltage sampling system and electric quantity metering device are provided, the circuit connection to a common ground, this common ground is still through a ground connection impedance ground connection, non-isolation voltage sampling circuit includes: the sampling branch circuit is configured to be connected with a live wire of an alternating current power supply to access alternating current voltage and bias voltage and output voltage components of the alternating current voltage and the bias voltage, and the number of the sampling branch circuits is one or three so as to respectively correspond to a single-phase alternating current power supply and a three-phase alternating current power supply; the first end of the first voltage divider is connected with a zero line of a power supply, and the second end of the first voltage divider is connected with the sampling branch; and the output module is configured to receive the voltage component and output the sampling voltage after voltage stabilization and filtering. A voltage transformer is not needed, so that the equipment cost is reduced; in addition, the circuit takes the earth as a reference point instead of a zero line, and the inequality of the single-phase common-mode voltage and the three-phase common-mode voltage does not exist.

Description

Non-isolated voltage sampling circuit, voltage sampling system and electric quantity metering device

Technical Field

The application belongs to the technical field of electronic circuits, and particularly relates to a non-isolated voltage sampling circuit, a voltage sampling system and an electric quantity metering device.

Background

Electricity metering is a common application in life, two basic data of electricity metering are voltage waveform data and Current waveform data, wherein the Current data are obtained through a Current Transformer (CT) with an isolation effect, and because the Current at the primary side can reach dozens of amperes and the surge Current even reaches thousands of amperes, a non-isolation scheme is difficult to adopt. The voltage data has a controllable range of 220V household voltage and 380V industrial line voltage, so that the voltage data can be implemented by an isolation scheme of a Potential Transformer (PT) and a non-isolation scheme of dividing voltage by using a resistor. The isolation scheme has the advantages that strong current and weak current are isolated, and common-mode potential cannot be introduced into weak current ends. The resistance voltage division is non-isolated, common-mode potential can be brought on weak current, and bare metal on a human touch circuit board can get an electric shock.

In the early days, each electric controller (such as a relay controller and an air switch controller) is independently supplied with power by an ACDC (automatic digital control computer), and optical coupling isolation is adopted for external communication. With the progress of times, the electrical complexity of engineering projects is higher and higher, and dozens of electrical controllers are arranged in the same cabinet. In order to save cost, a centralized power supply mode gradually appears, each electric controller is not provided with a power supply, and the power supply is uniformly supplied by a power supply module in the cabinet.

A problem arises in this case, if the electrical controllers also have a function of electrical measurement or pure voltage measurement, and a resistance voltage division scheme is used, the common mode voltage of each controller is different due to different circuit parameters, and each controller is connected in series by a centralized power supply, the common mode voltage of the system becomes a new value, and the voltage measurement is inaccurate. Moreover, if the user misconnects the phase and neutral wires, irreversible damage to the circuit board can result.

In order to overcome the defect that the common-mode voltage of the system causes inaccurate voltage measurement, three phases are divided by resistors, and a single phase adopts an isolation scheme to avoid different common-mode voltages being connected together, but the cost of the PT is increased.

SUMMERY OF THE UTILITY MODEL

An object of the application is to provide a non-isolation voltage sampling circuit and electronic equipment, aim at solving traditional voltage sampling circuit and have with high costs, the inaccurate problem of voltage measurement.

A first aspect of an embodiment of the present application provides a non-isolated voltage sampling circuit, connected to a common ground, the common ground further connected to ground through a ground impedance, the non-isolated voltage sampling circuit comprising:

the sampling branch circuit is configured to be connected with a live wire of an alternating current power supply to access alternating current voltage and bias voltage and output voltage components of the alternating current voltage and the bias voltage, and the number of the sampling branch circuits is one or three so as to respectively correspond to a single-phase alternating current power supply and a three-phase alternating current power supply;

the first end of the first voltage divider is connected with a zero line of a power supply, and the second end of the first voltage divider is connected with the sampling branch;

and the output module is configured to receive the voltage component and output the sampling voltage after voltage stabilization and filtering.

In one embodiment, the sampling branch includes a second voltage divider and a third voltage divider, a first end of the second voltage divider is connected to the live line, a second end of the second voltage divider is connected to a first end of the third voltage divider, a second end of the third voltage divider is connected to the bias voltage and a second end of the first voltage divider, and a second end of the second voltage divider is further used as an output of the sampling branch.

In one embodiment, the second voltage divider comprises at least one megaohm-scale resistor, and the resistors are connected in series when a plurality of resistors are connected.

In one embodiment, the first voltage divider comprises at least one megaohm resistor, and the resistors are connected in series.

In one embodiment, the ground impedance is a circuit composed of one or more of an inductor, a magnetic bead, a capacitor, and an ohmic resistor.

In one embodiment, the device further comprises a piezoresistor, and the piezoresistor is connected between the live wire and the neutral wire of the alternating current power supply.

In one embodiment, the output module includes a transient diode, a first resistor, and a first capacitor, a first pole of the transient diode is connected to the voltage component, a second pole of the transient diode is connected to the common ground, one end of the first resistor is connected to the first pole of the transient diode, and the other end of the first resistor is used as the output of the output module, and the first capacitor is connected between the other end of the first resistor and the common ground.

In one embodiment, the power supply module is used for providing the bias voltage, and is connected with the common ground.

In one embodiment, the power module comprises an amplifying circuit and a voltage-stabilizing filter circuit;

the amplifying circuit is a voltage follower circuit or a current series negative feedback amplifying circuit formed on the basis of an operational amplifier, the input end of the amplifying circuit is connected with a stable voltage, and the output end of the amplifying circuit outputs a voltage signal;

and the voltage stabilizing and filtering circuit carries out voltage stabilizing and filtering on the voltage signal to generate the bias voltage.

A second aspect of the embodiments of the present application provides an electricity metering device, which is characterized by comprising one or more non-isolated voltage sampling circuits as described above;

and the sampling end of the controller is connected with the output of the output module in each non-isolated voltage sampling circuit, receives the sampling voltage and calculates the electric quantity according to the sampling voltage.

A third aspect of the embodiments of the present application provides a voltage sampling system, which includes one or more electricity metering devices as described above, and a plurality of electricity metering devices are connected to the same power supply, and are commonly disposed on the power supply.

The non-isolated voltage sampling circuit, the electric quantity metering device and the voltage sampling system adopt a non-isolated mode to sample alternating current voltage, a voltage transformer is not needed, and the equipment cost is reduced; in addition, each electric quantity metering device in the whole system is supplied with power through a power supply, the common ground is arranged on the power supply and is connected with the ground through a grounding impedance, so that the circuit/device takes the ground as a reference point instead of a zero line, when a plurality of non-isolated voltage sampling circuits are used simultaneously and connected in parallel, the inequality of single-phase common-mode voltage and three-phase common-mode voltage does not exist, and the problem of inaccurate voltage measurement caused by the defect is solved.

Drawings

Fig. 1 is a block diagram of a voltage sampling system according to an embodiment of the present application.

Fig. 2 is a schematic circuit diagram of a voltage sampling system according to an embodiment of the present application.

Fig. 3 is a schematic diagram of a three-phase connection of a non-isolated voltage sampling circuit according to an embodiment of the present application.

Fig. 4 is a schematic diagram of a single-phase access of a non-isolated voltage sampling circuit according to an embodiment of the present application.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.

It will be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like, refer to an orientation or positional relationship illustrated in the drawings for convenience in describing the present application and to simplify description, and do not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present application.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.

Fig. 1 shows a circuit schematic diagram of a voltage sampling system provided in an embodiment of the present application, and for convenience of description, only the portions related to the embodiment are shown, and detailed descriptions are as follows:

the voltage sampling system comprises one or more electric quantity metering devices 100, the power supplies 200 connected to the plurality of electric quantity metering devices 100 are the same, and a common ground GND is arranged on the power supply 200, for example, a 12V power supply, and the common ground GND is generally a power supply ground. So that the individual fuel gauge devices 100 are equivalently wired together. The problem that voltage measurement is inaccurate and even damaged due to the fact that power ground of each electric quantity metering device 100 is brought to different electric potentials by the input fire zero line in non-isolated sampling can be solved. Since such different potentials do not interfere with or even damage each other if there is no connection between each of the fuel cell metering devices 100; if they share the power source 200, the different potentials will interfere with each other and even break down. Therefore, the grounds of the electricity metering devices 100 are connected together, so that the reference ground has only one potential, and the inequality between the single-phase common-mode voltage and the three-phase common-mode voltage does not exist, thereby solving the problem of inaccurate voltage measurement caused by the defect.

The electricity metering device 100 may be an independent electricity meter device or an air switch device having an electricity metering function.

Referring to fig. 2, the voltage sampling system shown in fig. 2 includes a non-isolated voltage sampling circuit 10 connected to a three-phase ac power source and a non-isolated voltage sampling circuit 10 connected to a single-phase ac power source, and the present application will explain related embodiments by using the system architecture, where the two non-isolated voltage sampling circuits 10 may be respectively disposed in two electric quantity metering devices 100, or may be disposed in the same electric quantity metering device 100 at the same time. Specifically, in the electricity quantity metering device 100, each non-isolated voltage sampling circuit 10 is connected to the bias voltage V1 and the transmission line of the alternating current power supply to be detected respectively.

Referring to fig. 1 to 4, in the embodiment of the present application, each non-isolated voltage sampling circuit 10 includes a sampling branch 11, a first voltage divider 12, and an output module 13. Each non-isolated voltage sampling circuit 10 is connected to the same common ground GND, which is also connected to ground through a ground impedance 14, which common ground GND is provided on the power supply 200 as previously described. The sampling branch 11 is configured to be connected with live lines UL or UA, UB, UC of the alternating current power supply to access the alternating current voltage, and a bias voltage V1 to output the alternating current voltage and voltage components UD or UA, UB, UC of the bias voltage V1, the sampling branch 11 is one or three to correspond to the single-phase alternating current power supply and the three-phase alternating current power supply respectively; a first end of the first voltage divider 12 is connected with a zero line UN of the power supply 200, and a second end of the first voltage divider 12 is connected with the sampling branch 11; the output module 13 is configured to receive the voltage component UD or Ua, Ub, Uc and output the sampled voltage VD or sampled voltages Va, Vb, Vc after voltage stabilization and filtering.

It can be understood that when the ac power supply is a single-phase ac power supply, the sampling branch 11 is one and is connected to the live wire UL of the ac power supply, and the output module 13 outputs one sampling voltage VD; when the alternating current power supply is a three-phase alternating current power supply, the number of the sampling branch circuits 11 is three, the sampling branch circuits are respectively connected to three live wires UA, UB and UC of the three-phase alternating current power supply, and the output module 13 outputs three sampling voltages Va, Vb and Vc.

Referring to fig. 1 and fig. 2, in an embodiment of the present application, the electric quantity metering device 100 includes one or more non-isolated voltage sampling circuits 10 and one or more controllers (not shown), where a sampling terminal of each controller is connected to an output of the output module 13 in each non-isolated voltage sampling circuit 10, receives the sampled voltage VD or the sampled voltages Va, Vb, and Vc, and calculates the electric quantity according to the sampled voltage VD or the sampled voltages Va, Vb, and Vc.

The bias voltage V1 connected to the non-isolated voltage sampling circuits 10 in the fuel gauge device 100 is provided for the same power module 15 (see fig. 3 and 4) to save cost. Or may be provided by respectively different power modules.

The fuel gauge device 100 may have one or more controllers, which are typically implemented as a single-chip, although a dedicated fuel gauge chip may be used. Each sampling end of the controller is connected with the output of the output module 13 in each non-isolated voltage sampling circuit 10, and receives single-phase sampling voltage VD or three-phase sampling voltages Va, Vb, Vc. The controller is used for processing according to the demand and the sampling voltage VD or the sampling voltages Va, Vb and Vc, such as electric quantity measurement, voltage protection, input and output control and the like. When the electric quantity metering device 100 includes a plurality of non-isolated voltage sampling circuits 10, the number of the controllers may be the same as that of the non-isolated voltage sampling circuits 10, and the controllers are used for respectively receiving the sampling voltages VD or the sampling voltages Va, Vb, Vc output by the different non-isolated voltage sampling circuits 10; or a controller is adopted, and different sampling ends are connected to sampling voltages VD or sampling voltages Va, Vb and Vc output by different non-isolated voltage sampling circuits 10.

In fig. 2, ROP1 and ROP2 are equivalent resistances of an output terminal of the power supply module 15 (see fig. 3 and 4) generating the bias voltage V1 to a common ground GND (which may be a digital ground), RAD1 to RAD4 are equivalent resistances of sampling terminals of the respective controllers to the common ground GND, RG is an equivalent resistance of the common ground GND to the ground, and RN is an equivalent resistance of the neutral line UN to the ground. After the common ground GND is introduced into the ground through the grounding impedance 14, when the three-phase alternating-current power supply is sampled, the non-isolated voltage sampling circuit 10 and the controller use the ground as a reference point instead of the zero line UN, and the influence of the resistance of the zero line UN is not existed, so that the problem of the difference of the common-mode potentials does not exist. In addition, after the common ground GND has been connected to ground, the first voltage divider 12 of the neutral line UN is essentially bypassed by a new branch formed by the equivalent resistance RAD in parallel with ROP and RG, since this branch has a lower resistance. The single-phase condition is similar, and the earth is used as the main reference, so even if the power is supplied in a centralized way, the problem of different common-mode voltages is avoided.

Optionally, whether single-phase or three-phase connection is performed, the first voltage divider 12 includes at least one megohm-level resistor, and the resistors R1 and R2 are connected in series when there are multiple resistors, for example, the resistor R1 is 1 megohm, and the resistor R2 is 0 megohm. The total resistance of the first voltage divider 12 is megaohms, and the specific resistance is properly adjusted according to different equivalent resistors ROP1, ROP2, RAD1 through RAD 4. The purpose of adopting a plurality of resistances connected in series is to improve creepage distance and be beneficial to improving safety level.

For example, the resistance value of the first voltage divider 12 is 0805 packaged 1 mega ohm resistor, the power is 125mW, the maximum voltage that a single resistor can bear is 353V, if a user connects the live wire UA and the zero wire UN of three phases reversely, the alternating voltage connected to the live wire UA passes through the first voltage divider 12, the equivalent resistors ROP1, ROP2 and RG reach the ground, the leakage current is less than 220UA, the leakage trip cannot be triggered, the current is very small, and the circuit board cannot be damaged. When the single phase is reversed, the current paths are similar and are not described in detail.

In an embodiment, taking the example of accessing a three-phase ac power supply, the sampling branch 11 includes three sampling branches, and taking one of the three sampling branches as an example, the sampling branch 11 includes a second voltage divider 111 and a third voltage divider 112, a first end of the second voltage divider 111 is connected to the live line UA, a second end of the second voltage divider 111 is connected to a first end of the third voltage divider 112, a second end of the third voltage divider 112 is connected to the bias voltage V1 and a second end of the first voltage divider 12, and the second end of the second voltage divider 111 is also used as an output of the sampling branch 11. The second voltage divider 111 receives the ac voltage, passes through the third voltage divider 112, is collected together, returns to the neutral line UN through the first voltage divider 12, and inputs the bias voltage V1 obtained from the third voltage divider 112 and the voltage component Ua of the ac voltage to the output module 13.

The second voltage divider 111 includes at least one megohm-level resistor, and a plurality of resistors R3 and R4 are connected in series, and in the example of fig. 2, there are two resistors R3 and R4. The method is realized by adopting a plurality of resistors connected in series, aims to improve the creepage distance and is beneficial to improving the safety rating, for example, the resistor R3 is 3 megaohms, and the resistor R4 is 5 megaohms. The third voltage divider 112 includes at least one sampling resistor R5, and the sampling resistor R5 is sized according to requirements, such as kilo-ohm.

The other sampling branches connected to the three-phase ac power supply or the sampling branch connected to the single-phase ac power supply are similar to the sampling branch 11 described above, and are not described herein again.

In some embodiments, the ground impedance 14 is a circuit comprising one or more of an inductor, a bead, a capacitor, and an ohmic resistor. In the example of fig. 3, the ground impedance 14 is implemented using an inductance L1, through which the common ground GND is connected to ground, which may be placed inside the power supply 200 providing a centralized power supply.

Typically, the non-isolated voltage sampling circuit 10 further comprises a voltage dependent resistor connected between the live and neutral lines of the ac power supply for overvoltage protection. Referring to fig. 3, when the ac power is single-phase, the non-isolated voltage sampling circuit 10 uses a voltage dependent resistor R22; when the connected ac power supply is three-phase, the non-isolated voltage sampling circuit 10 uses three voltage dependent resistors R12, R13, and R14, which are respectively connected between the three live wires UA, UB, UC, and the zero line UN.

Referring to fig. 3 and 4, in an embodiment, the output module 13 includes one or three branches having the same branch, and the branches correspond to a sampling output of the single-phase ac power supply and a sampling output of the three-phase ac power supply, respectively. Taking the example of being connected to a three-phase ac power supply, one of the branches 131 includes a transient diode D1, a first resistor R15, and a first capacitor C1, a first pole of the transient diode D1 is connected to the voltage component Ua, i.e., the second end of the second voltage divider 111, a second pole of the transient diode D1 is connected to the common ground GND, one end of the first resistor R15 is connected to the first pole of the transient diode D1, the other end of the first resistor R15 is used as the output of the output module 13, and the first capacitor C1 is connected between the other end of the first resistor R15 and the common ground GND. The transient diode D1 is configured to clamp the connected voltage component Ua to stabilize the voltage, the first resistor R15 and the first capacitor C1 form an RC filter to filter the voltage component Ua, and the other branches of the output module 13 or the output module 13 connected to the single-phase ac power supply are similar to the branch 131, which is not described herein again.

Referring to fig. 3 and 4, optionally, the non-isolated voltage sampling circuit 10 further includes a power module 15 for providing a bias voltage V1, and the power module 15 is connected to the common ground GND. As described above, the power module 15 may provide the bias voltage V1 to one or more non-isolated voltage sampling circuits 10 in the fuel gauge device 100.

The power module 15 includes an amplifier circuit 151 and a voltage regulator filter circuit 152. The amplifier circuit 151 is a voltage follower circuit or a current series negative feedback amplifier circuit (as shown in fig. 3 or 4) configured by an operational amplifier U1, and the amplifier circuit 151 has a function of increasing the input/output resistance and stabilizing the output current.

The input end of the amplifying circuit 151 is connected to a stable voltage Vref, and the output end outputs a voltage signal; the resistors R18 and R19 and the capacitors C4 and C5 disposed at the input side of the amplifier 151 are used for dividing and filtering the connected regulated voltage Vref, which may be provided by the internal reference power supply of the controller or by a dc regulated voltage provided by another power supply.

The voltage stabilizing filter circuit 152 performs voltage stabilizing filtering on the voltage signal output from the amplifier circuit 151 to generate the bias voltage V1. The voltage stabilizing filter circuit comprises a transient diode D4 for clamping and capacitors C7 and C8 for filtering.

The circuit that this application provided can realize that a plurality of voltage sampling both adopted the centralized power supply, can adopt the voltage acquisition scheme of non-isolation again, is not afraid of the user moreover and connects conversely, though connect can influence the voltage measurement after turning over, can not damage the circuit board, suggestion user after the procedure is reported the mistake correct the wiring can.

The application uses the centralized power supply, saves the cost of an independent power supply circuit in each controller, can adopt a resistor voltage division connection method, and saves the cost of a PT isolation device. The communication lines are also non-isolated, which also saves the cost of the isolation devices of the communication lines. And the size of the controller is reduced, which is beneficial to the miniaturization of the product.

The above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present application and are intended to be included within the scope of the present application.

Claims

1. A non-isolated voltage sampling circuit connected to a common ground that is also connected to ground through a ground impedance, said non-isolated voltage sampling circuit comprising:

2. The non-isolated voltage sampling circuit according to claim 1, wherein the sampling branch comprises a second voltage divider and a third voltage divider, a first end of the second voltage divider is connected to the live line, a second end of the second voltage divider is connected to a first end of the third voltage divider, a second end of the third voltage divider is connected to the bias voltage and a second end of the first voltage divider, and a second end of the second voltage divider is further used as an output of the sampling branch.

3. The non-isolated voltage sampling circuit of claim 2 wherein the second voltage divider comprises at least one megaohm-scale resistor, the resistor being a plurality of resistors connected in series.

4. A non-isolated voltage sampling circuit according to any of claims 1 to 3 wherein the first voltage divider comprises at least one megaohm resistor, the resistors being connected in series.

5. The non-isolated voltage sampling circuit of any of claims 1 to 3 wherein the ground impedance is a circuit comprising one or more of an inductor, a bead, a capacitor, and an ohmic resistor.

6. The non-isolated voltage sampling circuit of any of claims 1 to 3 further comprising a varistor connected between the live and neutral conductors of the AC power source.

7. The non-isolated voltage sampling circuit according to any of claims 1 to 3, wherein the output module comprises a transient diode, a first resistor and a first capacitor, a first pole of the transient diode is connected to the voltage component, a second pole of the transient diode is connected to the common ground, one end of the first resistor is connected to the first pole of the transient diode, the other end of the first resistor is used as the output of the output module, and the first capacitor is connected between the other end of the first resistor and the common ground.

8. The non-isolated voltage sampling circuit of any of claims 1 to 3 further comprising a power supply module for providing the bias voltage, the power supply module being connected to the common ground.

9. The non-isolated voltage sampling circuit of claim 8 wherein the power module comprises an amplification circuit and a voltage regulation filter circuit;

10. An electrical quantity metering device comprising one or more non-isolated voltage sampling circuits according to any one of claims 1 to 9;

11. A voltage sampling system comprising one or more coulometric devices as claimed in claim 10, connected to the same power supply, said common ground being arranged on said power supply.