Non-isolated voltage sampling circuit, voltage sampling system and electricity metering device

Abstract

The present application relates to the field of electronic circuit technology, and provides a non-isolated voltage sampling circuit, a voltage sampling system and an electric quantity metering device. The circuit is connected to a common ground, and the common ground is also grounded through a grounding impedance. The non-isolated voltage sampling circuit includes: a sampling branch, which is configured to be connected to the live wire of an AC power supply to access the AC voltage, and a bias voltage, outputting the voltage components of the AC voltage and the bias voltage, and the sampling branch is one or three to correspond to a single-phase AC power supply and a three-phase AC power supply respectively; a first voltage divider, the first end of the first voltage divider is connected to the neutral wire of the power supply, and the second end is connected to the sampling branch; an output module, which is configured to receive the voltage component and output the sampling voltage after voltage stabilization and filtering. No voltage transformer is required, which reduces the equipment cost; in addition, the circuit uses the earth as a reference point instead of the neutral wire, and there is no inequality between the single-phase common mode voltage and the three-phase common mode voltage.

Description

Technical Field

[0001] The present application belongs to the technical field of electronic circuits, and in particular relates to a non-isolated voltage sampling circuit, a voltage sampling system and an electric quantity metering device. Background Art

[0002] Electricity metering is a very common application in life. The two basic data of electricity metering are voltage waveform data and current waveform data. The current data is obtained through the current transformer (CT) with isolation effect. Because the current on the primary side can reach tens of amperes, and the surge current can even reach thousands of amperes, it is difficult to use a non-isolated solution. As for voltage data, because the household voltage is 220V and the industrial line voltage is 380V, the range is controllable, so there are two methods: isolation solution using potential transformer (PT) and non-isolation solution using resistor voltage division. The advantage of the isolation solution is that strong and weak electricity are isolated, and the weak current end will not introduce common mode potential. However, resistor voltage division is non-isolated, and the weak current will carry common mode potential. If a person touches the exposed metal on the circuit board, he may get an electric shock.

[0003] In the early days, each electrical controller (such as relay controller, air switch controller) was independently powered by ACDC, and external communication also used optocoupler isolation. As the times progress, the electrical complexity of engineering projects has become increasingly higher, and there will be dozens of electrical controllers in the same cabinet. In order to save costs, centralized power supply has gradually emerged. Each electrical controller no longer has its own power supply, but is uniformly powered by the power module in the cabinet.

[0004] At this time, a problem arises. If the electrical controller also has the function of electricity metering or simple voltage measurement, and uses a resistor voltage division scheme, due to different circuit parameters, the common mode voltage of each controller is different, and each controller is connected in series through a centralized power supply, then the common mode voltage of the system will become a new value, resulting in inaccurate voltage measurement. Moreover, if the user connects the phase line and the neutral line incorrectly, it will cause irreversible damage to the circuit board.

[0005] In order to overcome the disadvantage of inaccurate voltage measurement caused by the common-mode voltage of the system, three-phase voltage division is done by resistors, and single-phase voltage division uses isolation scheme to avoid different common-mode voltages being connected together, but this increases the cost of PT. Summary of the invention

[0006] The purpose of the present application is to provide a non-isolated voltage sampling circuit and an electronic device, aiming to solve the problems of high cost and inaccurate voltage measurement in traditional voltage sampling circuits.

[0007] A first aspect of an embodiment of the present application provides a non-isolated voltage sampling circuit, which is connected to a common ground, and the common ground is also grounded through a grounding impedance. The non-isolated voltage sampling circuit includes:

[0008] A sampling branch is configured to be connected to the live wire of the AC power supply to access the AC voltage and a bias voltage, and output the voltage components of the AC voltage and the bias voltage. The sampling branch is one or three to correspond to the single-phase AC power supply and the three-phase AC power supply respectively.

[0009] A first voltage divider, wherein a first end of the first voltage divider is connected to a neutral line of a power supply, and a second end of the first voltage divider is connected to the sampling branch;

[0010] The output module is configured to receive the voltage component and output a sampled voltage after voltage stabilization and filtering.

[0011] In one embodiment, the sampling branch includes a second voltage divider and a third voltage divider, the first end of the second voltage divider is connected to the live wire, the second end of the second voltage divider is connected to the first end of the third voltage divider, the second end of the third voltage divider is connected to the bias voltage and the second end of the first voltage divider, and the second end of the second voltage divider also serves as the output of the sampling branch.

[0012] In one embodiment, the second voltage divider includes at least one megaohm resistor, and a plurality of the resistors are connected in series.

[0013] In one embodiment, the first voltage divider includes at least one megaohm resistor, and a plurality of the resistors are connected in series.

[0014] 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.

[0015] In one of the embodiments, a varistor is further included, and the varistor is connected between the live wire and the neutral wire of the AC power supply.

[0016] In one embodiment, the output module includes a transient diode, a first resistor and a first capacitor, the first pole of the transient diode is connected to the voltage component, the second pole 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 serves 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.

[0017] In one of the embodiments, a power supply module for providing the bias voltage is further included, and the power supply module is connected to the common ground.

[0018] In one of the embodiments, the power module includes an amplifier circuit and a voltage stabilizing and filtering circuit;

[0019] The amplifier circuit is a voltage follower circuit or a current series negative feedback amplifier circuit based on an operational amplifier, the input end of the amplifier circuit is connected to a stable voltage, and the output end outputs a voltage signal;

[0020] The voltage stabilizing and filtering circuit performs voltage stabilizing and filtering on the voltage signal to generate the bias voltage.

[0021] A second aspect of an embodiment of the present application provides an electric quantity metering device, characterized in that it comprises one or more non-isolated voltage sampling circuits as described above;

[0022] One or more controllers, wherein the sampling end of the controller is connected to the output of the output module in each of the non-isolated voltage sampling circuits, receives the sampled voltage, and calculates the electric quantity according to the sampled voltage.

[0023] A third aspect of an embodiment of the present application provides a voltage sampling system, comprising one or more power metering devices as described above, wherein the power supply to which the multiple power metering devices are connected is the same, and the common ground is arranged on the power supply.

[0024] The above-mentioned non-isolated voltage sampling circuit, electricity metering device and voltage sampling system adopt a non-isolated method to perform AC voltage sampling, and do not need to use a voltage transformer, thereby reducing equipment costs; in addition, each electricity metering device in the entire system is powered by a power supply, and a common ground is set on the power supply and connected to the ground through a grounding impedance, so that the circuit / device uses the ground as a reference point instead of the neutral line. When multiple non-isolated voltage sampling circuits are used and connected in parallel at the same time, there is no inequality between the single-phase common-mode voltage and the three-phase common-mode voltage, thereby solving the problem of inaccurate voltage measurement caused by this defect. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A module diagram of a voltage sampling system provided in an embodiment of the present application.

[0026] Figure 2 A circuit diagram of a voltage sampling system provided in an embodiment of the present application.

[0027] Figure 3 A schematic diagram of a three-phase access to a non-isolated voltage sampling circuit provided in an embodiment of the present application.

[0028] Figure 4 A schematic diagram of a single-phase access to a non-isolated voltage sampling circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0029] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0030] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or 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 indirectly connected to the other element.

[0031] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0032] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0033] Figure 1 A circuit diagram of a voltage sampling system provided in an embodiment of the present application is shown. For ease of explanation, only the part related to the present embodiment is shown, which is described in detail as follows:

[0034] The voltage sampling system includes one or more power metering devices 100. The power supply 200 connected to the multiple power metering devices 100 is the same, and the common ground GND is set on the power supply 200. For example, for a 12V power supply 200, the common ground GND is generally the power ground. So that each power metering device 100 is equivalent to being connected together. It can solve the problem that during non-isolated sampling, the power ground of each power metering device 100 will be brought to a different potential by the input live and neutral wires, causing inaccurate voltage measurement or even damage. If there is no connection between each power metering device 100, such different potentials will not cause mutual interference or even damage; and if they share the power supply 200, the different potentials will interfere with each other or even damage. Therefore, the grounds of each power metering device 100 are connected together, so that the reference ground has only one potential, then there is no inequality between the single-phase common mode voltage and the three-phase common mode voltage, and the problem of inaccurate voltage measurement caused by this defect is solved.

[0035] The electricity metering device 100 may be a separate electricity meter device, or an air switch device with an electricity metering function.

[0036] See also Figure 2 , Figure 2 The voltage sampling system shown includes a non-isolated voltage sampling circuit 10 connected to a three-phase AC power supply and a non-isolated voltage sampling circuit 10 connected to a single-phase AC power supply. The present application will use this system architecture to describe the relevant embodiments, wherein the two non-isolated voltage sampling circuits 10 can be respectively arranged in two power metering devices 100, or can be simultaneously arranged in the same power metering device 100. Specifically, in the power metering device 100, each non-isolated voltage sampling circuit 10 is respectively connected to the bias voltage V1 and the transmission line of the AC power supply to be detected.

[0037] See also Figures 1 to 4In 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 grounded through a grounding impedance 14. As mentioned above, the common ground GND is set on the power supply 200. The sampling branch 11 is configured to be connected to the live wire UL or UA, UB, UC of the AC power supply to access the AC voltage, and a bias voltage V1, and output the voltage components UD or Ua, Ub, Uc of the AC voltage and the bias voltage V1. The sampling branch 11 is one or three to correspond to the single-phase AC power supply and the three-phase AC power supply respectively; the first end of the first voltage divider 12 is connected to the neutral line UN of the power supply 200, and the second end of the first voltage divider 12 is connected to the sampling branch 11; the output module 13 is configured to receive the voltage component UD or Ua, Ub, Uc and output the sampling voltage VD or the sampling voltage Va, Vb, Vc after voltage stabilization and filtering.

[0038] It can be understood that when the AC power supply is a single-phase AC power supply, there is one sampling branch 11, which is connected to the live wire UL of the AC power supply, and the output module 13 outputs one sampling voltage VD; when the AC power supply is a three-phase AC power supply, there are three sampling branches 11, which are respectively connected to the three live wires UA, UB, and UC of the three-phase AC power supply, and the output module 13 outputs three sampling voltages Va, Vb, and Vc.

[0039] See also Figure 1 and Figure 2 In one embodiment of the present application, the power metering device 100 includes one or more non-isolated voltage sampling circuits 10 and one or more controllers (not shown), the sampling end of the controller is connected to the output of the output module 13 in each non-isolated voltage sampling circuit 10, receives the sampling voltage VD or the sampling voltages Va, Vb, Vc, and calculates the power according to the sampling voltage VD or the sampling voltages Va, Vb, Vc.

[0040] The bias voltage V1 connected to the multiple non-isolated voltage sampling circuits 10 in the electric quantity metering device 100 is the same power supply module 15 (see Figure 3 , 4 ) to save costs. It can also be provided by different power modules.

[0041] The power metering device 100 may have one or more controllers. The controller generally adopts a single-chip microcomputer chip, and of course a dedicated power metering chip may also be used. The sampling end of the controller is connected to the output of the output module 13 in each non-isolated voltage sampling circuit 10, and receives a single-phase sampling voltage VD or a three-phase sampling voltage Va, Vb, Vc. The controller is used to process according to the demand and the sampling voltage VD or the sampling voltage Va, Vb, Vc, such as power metering, voltage protection, input and output control, etc. Among them, when the power metering device 100 includes multiple non-isolated voltage sampling circuits 10, the number of controllers can be the same as the non-isolated voltage sampling circuits 10, so as to respectively receive the sampling voltage VD or the sampling voltage Va, Vb, Vc output by different non-isolated voltage sampling circuits 10; or one controller is used to connect the sampling voltage VD or the sampling voltage Va, Vb, Vc output by different non-isolated voltage sampling circuits 10 with different sampling ends. In addition, Figure 2 In the figure, ROP1 and ROP2 are the equivalent resistances of the output end generating the bias voltage V1 to the common ground GND (which can be a digital ground), RAD1 to RAD4 are the equivalent resistances of the sampling end of each controller to the common ground GND, RG is the equivalent resistance of the common ground GND to the earth, and RN is the equivalent resistance of the neutral line UN to the earth. After the common ground GND is introduced to the earth through the grounding impedance 14, when sampling the three-phase AC power supply, the non-isolated voltage sampling circuit 10 and the controller use the earth as the reference point instead of the neutral line UN, and the great influence of the resistance of the neutral line UN does not exist, so there is no problem of unequal common mode potential. In addition, after the common ground GND is connected to the earth, the first voltage divider 12 of the neutral line UN is basically bypassed by the new branch formed by the equivalent resistor RAD and ROP in parallel and RG, because the resistance of this branch is smaller. The single-phase situation is similar, and the earth is used as the main reference, so even if the power supply is centralized, there will be no problem of different common mode voltages.

[0042] Optionally, whether single-phase or three-phase access, the first voltage divider 12 includes at least one megaohm resistor, and the resistors R1 and R2 are connected in series when there are multiple resistors, such as resistor R1 is 1 megaohm and resistor R2 is 0 megaohm. Then the total resistance of the first voltage divider 12 is megaohm, and the specific resistance is appropriately adjusted according to different equivalent resistors ROP1, ROP2, RAD1~RAD4. The purpose of using multiple resistors in series is to increase the creepage distance, which is conducive to improving the safety level.

[0043] For example, the resistance of the first voltage divider 12 is a 1 megohm resistor in 0805 package, with a power of 125mW. The maximum voltage that a single resistor can withstand is 353V. If the user connects the three-phase live wire UA and the neutral wire UN in reverse, the AC voltage connected to the live wire UA passes through the first voltage divider 12, the equivalent resistors ROP1, ROP2, and RG to the ground, and the leakage current is <220uA, which will not trigger the leakage trip. The current is very small and will not damage the circuit board. When the single phase is connected in reverse, the current path is similar and will not be repeated.

[0044] In one embodiment, taking the access to a three-phase AC power supply as an example, three sampling branches 11 are included, and one of them is used as an example for explanation. The sampling branch 11 includes a second voltage divider 111 and a third voltage divider 112. The first end of the second voltage divider 111 is connected to the live wire UA, the second end of the second voltage divider 111 is connected to the first end of the third voltage divider 112, the second end of the third voltage divider 112 is connected to the bias voltage V1 and the second end of the first voltage divider 12, and the second end of the second voltage divider 111 is also used as the output of the sampling branch 11. The second voltage divider 111 receives the AC voltage, which is collected after passing through the third voltage divider 112, and returns to the neutral line UN through the first voltage divider 12. The bias voltage V1 and the voltage component Ua of the AC voltage obtained from the third voltage divider 112 are input to the output module 13.

[0045] The second voltage divider 111 includes at least one megohm resistor, and multiple resistors R3 and R4 are connected in series. Figure 2 In the example, there are two resistors, namely, resistors R3 and R4. The purpose of using multiple resistors connected in series is to increase the creepage distance, which is conducive to improving the safety level. For example, the resistor R3 is 3 megohms and the resistor R4 is 5 megohms. The third voltage divider 112 includes at least one sampling resistor R5, and the size of the sampling resistor R5 is set according to the requirements, for example, in the kilo-ohm level.

[0046] Other sampling branches connected to a three-phase AC power source or a sampling branch connected to a single-phase AC power source are similar to the above-mentioned sampling branch 11 and will not be described in detail here.

[0047] In some embodiments, the ground impedance 14 is a circuit composed of one or more of an inductor, a magnetic bead, a capacitor, and an ohmic resistor. Figure 3 In the example, the grounding impedance 14 is implemented by an inductor L1, and the common ground GND is connected to the ground through this high-current inductor. The grounding point can be placed inside the power supply 200 that provides centralized power supply.

[0048] Generally, the non-isolated voltage sampling circuit 10 also includes a varistor, which is connected between the live wire and the neutral wire of the AC power supply for overvoltage protection. Figure 3When the connected AC power supply is single-phase, the non-isolated voltage sampling circuit 10 uses a varistor R22; when the connected AC power supply is three-phase, the non-isolated voltage sampling circuit 10 uses three varistors R12, R13, and R14, which are respectively connected between the three live wires UA, UB, and UC and the neutral wire UN.

[0049] See also Figure 3 and Figure 4 In one embodiment, the output module 13 includes one or three identical branches, which correspond to the sampling output of the single-phase AC power supply and the sampling output of the three-phase AC power supply. Taking the connection to the three-phase AC power supply as an example, one of the branches 131 includes a transient diode D1, a first resistor R15 and a first capacitor C1. The first pole of the transient diode D1 is connected to the voltage component Ua, that is, the second end of the second voltage divider 111, and the second pole 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, and the other end is used as the output of the output module 13. 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 used to clamp the connected voltage component Ua to stabilize the voltage. The first resistor R15 and the first capacitor C1 form an RC filter for filtering the voltage component Ua. 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 above-mentioned branch 131, which will not be repeated here.

[0050] See also Figure 3 and Figure 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 can provide a bias voltage V1 to one or more non-isolated voltage sampling circuits 10 in the electric quantity metering device 100.

[0051] The power module 15 includes an amplifier circuit 151 and a voltage stabilizing filter circuit 152. The amplifier circuit is based on a voltage follower circuit or a current series negative feedback amplifier circuit (such as Figure 3 or Figure 4 As shown), the amplifier circuit 151 has the function of increasing the input and output resistance and stabilizing the output current.

[0052] The input end of the amplifier circuit 151 is connected to a stable voltage Vref, and the output end outputs a voltage signal; the resistors R18, R19 and capacitors C4, C5 set on the input side of the amplifier circuit 151 are used to divide and filter the connected stable voltage Vref. The stable voltage Vref can be provided by the internal reference power supply of the above-mentioned controller, or a DC stable voltage provided by other power supplies.

[0053] The voltage stabilizing and filtering circuit 152 performs voltage stabilizing and filtering on the voltage signal output by the amplifying circuit 151 to generate a bias voltage V1. The voltage stabilizing and filtering circuit includes a transient diode D4 for clamping, and capacitors C7 and C8 for filtering.

[0054] The circuit provided in this application can realize multiple voltage sampling and adopt both centralized power supply and non-isolated voltage acquisition scheme, and is not afraid of reverse connection by users. Although reverse connection will affect voltage measurement, it will not damage the circuit board. After the program reports an error, it can prompt the user to correct the wiring.

[0055] This application uses a centralized power supply, saving the cost of independent power supply circuits in each controller. All can be connected by resistor voltage division, saving the cost of PT isolation devices. The communication line is also non-isolated, saving the cost of communication line isolation devices. It also reduces the size of the controller, which is conducive to product miniaturization.

[0056] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A non-isolated voltage sampling circuit, characterized in that: Connected to a common ground, which is also grounded through a grounding impedance, the non-isolated voltage sampling circuit includes: A sampling branch is configured to be connected to the live wire of the AC power supply to access the AC voltage, and is also configured to access a bias voltage. The sampling branch includes a second voltage divider and a third voltage divider. The first end of the second voltage divider is connected to the live wire, the second end of the second voltage divider is connected to the first end of the third voltage divider, the second end of the third voltage divider is connected to the bias voltage and the second end of the first voltage divider, and the second end of the third voltage divider also serves as the output of the sampling branch to output the voltage component of the AC voltage and the bias voltage. The sampling branch is one or three to correspond to the single-phase AC power supply and the three-phase AC power supply respectively. A first voltage divider, wherein a first end of the first voltage divider is connected to a neutral line of a power supply, and a second end of the first voltage divider is connected to the sampling branch; An output module, connected to the sampling branch and the common ground, configured to receive the voltage component and output a sampled voltage after voltage stabilization and filtering; The first voltage divider includes at least one megohm resistor, wherein a plurality of the resistors are connected in series; The grounding impedance is a circuit composed of one or more of an inductor, a magnetic bead, a capacitor, and an ohmic resistor.

2. The non-isolated voltage sampling circuit according to claim 1, characterized in that: The second voltage divider includes at least one megaohm resistor, and a plurality of the resistors are connected in series.

3. The non-isolated voltage sampling circuit according to claim 1 or 2, characterized in that: It also includes a varistor, which is connected between the live wire and the neutral wire of the AC power supply.

4. The non-isolated voltage sampling circuit according to claim 1 or 2, characterized in that: The output module includes a transient diode, a first resistor and a first capacitor, the first pole of the transient diode is connected to the voltage component, the second pole 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 serves 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.

5. The non-isolated voltage sampling circuit according to claim 1 or 2, characterized in that: It also includes a power supply module for providing the bias voltage, and the power supply module is connected to the common ground.

6. The non-isolated voltage sampling circuit according to claim 5, characterized in that: The power supply module includes an amplifier circuit and a voltage stabilizing filter circuit; The amplifier circuit is a voltage follower circuit or a current series negative feedback amplifier circuit based on an operational amplifier, the input end of the amplifier circuit is connected to a stable voltage, and the output end outputs a voltage signal; The voltage stabilizing and filtering circuit performs voltage stabilizing and filtering on the voltage signal to generate the bias voltage.

7. An electric quantity measuring device, characterized in that: comprising one or more non-isolated voltage sampling circuits as claimed in any one of claims 1 to 6; One or more controllers, wherein the sampling end of the controller is connected to the output of the output module in each of the non-isolated voltage sampling circuits, receives the sampled voltage, and calculates the electric quantity according to the sampled voltage.

8. A voltage sampling system, characterized in that: It comprises one or more electric quantity measuring devices as claimed in claim 7, the power supply to which the multiple electric quantity measuring devices are connected is the same, and the common ground is arranged on the power supply.

Images