An AC voltage measurement circuit

Abstract

The present application belongs to the technical field of AC voltage measurement, and in particular, relates to an AC voltage measurement circuit. It includes: a transformer unit, the input end of which is electrically connected to the AC power through a plurality of voltage-dividing resistors; a rectifier circuit, which is electrically connected to the output end of the transformer unit; a filter circuit, which is electrically connected to the output end of the rectifier circuit; and a measuring unit, which is electrically connected to the filter circuit and is used to measure voltage. The input end of the transformer unit of the utility model is connected to the AC power through a voltage-dividing resistor, which can not only achieve voltage reduction, but also separate strong current from weak current, and avoid interference from strong current during measurement.

Description

Technical Field

[0001] The present application belongs to the technical field of alternating current voltage measurement, and in particular relates to an alternating current voltage measurement circuit and a rectifier circuit. Background Art

[0002] At present, the traditional voltage measurement method is generally: use a voltage divider circuit to divide the target voltage, obtain a certain proportion of voltage, and then convert the voltage signal into a current signal for collection; this measurement method, when applied to higher AC voltages, is prone to poor isolation between strong and weak electricity, and strong electricity can interfere with weak electricity systems. Utility Model Content

[0003] The purpose of the present application is to provide an AC voltage measurement circuit, aiming to solve the problem of poor isolation of strong and weak currents and easy mutual interference in traditional measurement methods.

[0004] An AC voltage measurement circuit, comprising:

[0005] A transformer unit, the input end of which is electrically connected to the AC power via a plurality of voltage-dividing resistors;

[0006] A rectifier circuit, electrically connected to the output end of the transformer unit;

[0007] A filter circuit is electrically connected to the output end of the rectifier circuit;

[0008] The measuring unit is electrically connected to the filter circuit and is used to measure the voltage.

[0009] Preferably, the rectifier circuit includes a half-wave precision rectifier circuit, which includes: an operational amplifier U1, the non-phase input terminal of the operational amplifier U1 is grounded through a resistor R5, the inverting input terminal of the operational amplifier U1 is connected to the input terminal of the rectifier circuit, the inverting input terminal of the operational amplifier U1 is connected to the output terminal of the operational amplifier U1 through a diode D1, and the output terminal of the diode D1 is connected to the output terminal of the rectifier circuit through a diode D2; the inverting input terminal of the operational amplifier U1 is connected to the output terminal of the rectifier circuit through a resistor R4.

[0010] Preferably, the rectification circuit comprises a full-wave rectification circuit.

[0011] Furthermore, the transformer unit includes a voltage transformer P1; one input end of the voltage transformer is connected to the live wire of the alternating current through a voltage dividing resistor R1, and the other input end of the voltage transformer is connected to the neutral wire of the alternating current through a voltage dividing resistor R2.

[0012] Furthermore, it also includes a high-voltage protection circuit, which is arranged between the transformer unit and the rectifier circuit.

[0013] Preferably, the high-voltage protection circuit comprises a TVS tube, and two ends of the TVS tube are respectively connected to two output ends of the transformer unit.

[0014] Furthermore, a capacitor C1 is connected between the high-voltage protection circuit and the rectifier circuit.

[0015] Furthermore, the filter circuit includes a resistor R6, one end of the resistor R6 is connected to the output end of the rectifier circuit, and the other end of the resistor R6 is grounded through a capacitor unit; the other end of the resistor R6 is connected to the output end of the filter circuit.

[0016] Preferably, the capacitor unit includes a capacitor C2 and a capacitor C3 connected in parallel.

[0017] Preferably, the full-wave rectifier circuit includes: an operational amplifier U1 and an operational amplifier U2; the input end of the full-wave rectifier circuit is connected to the inverting input end of the operational amplifier U1 and the inverting input end of the operational amplifier U2 through resistors R7 and R8 respectively; the inverting input end of the operational amplifier U1 is connected to the output end of the operational amplifier U1 through a diode D1, the output end of the operational amplifier U1 is connected to a diode D2, and the inverting input end of the operational amplifier U1 is connected to the output end of the diode D2 through a resistor R4; the output end of the diode D2 is connected to the inverting input end of the operational amplifier U2 through a resistor R6; the inverting input end of the operational amplifier U2 is connected to the output end of the operational amplifier U2 through a resistor R9.

[0018] Compared with the prior art, the utility model has the following beneficial effects: the input end of the transformer unit is connected to the AC power through the voltage dividing resistor, which can not only reduce the voltage, but also separate the strong current from the weak current, thus avoiding the interference of the strong current during measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the principle of this embodiment 1.

[0020] Figure 2 This is an exemplary circuit schematic diagram of Embodiment 1.

[0021] Figure 3 This is an exemplary circuit schematic diagram of Embodiment 2.

[0022] Reference numerals:

[0023] 1——Transformer unit;

[0024] 2——rectifier circuit;

[0025] 3——Filter circuit;

[0026] 4——High voltage protection circuit. DETAILED DESCRIPTION

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] Embodiment 1: Figure 1 Shows a preferred embodiment of the present application ( Figure 1 The schematic diagram of the principle of the AC voltage measurement circuit provided in the first embodiment of the present application is shown. For the convenience of explanation, only the part related to the present embodiment is shown, which is described in detail as follows: An AC voltage measurement circuit, comprising:

[0032] A transformer unit 1, wherein the input end of the transformer unit 1 is electrically connected to the AC power through a plurality of voltage-dividing resistors;

[0033] The rectifier circuit 2 is electrically connected to the output end of the transformer unit 1;

[0034] The filter circuit 3 is electrically connected to the output end of the rectifier circuit 2;

[0035] The measuring unit is electrically connected to the filter circuit 3 and is used to measure the voltage.

[0036] The difference between this technical solution and the prior art is that: while dividing the voltage, the transformer unit 1 is used for voltage transformation; the high voltage is reduced to a low voltage; the strong current system is directly isolated to avoid the interference of the strong current system on the weak current system. The rectifier circuit 2, the filter circuit 3, and the measuring unit can all be the prior art, and the measuring unit can measure IC, MCU, CPU, voltmeter, etc.

[0037] Preferably, the rectifying circuit 2 includes a rectifying diode.

[0038] When using a rectifier diode, ideally, AC can only pass through the rectifier diode when the AC waveform is in the positive half. Secondly, since there is a PN junction inside the rectifier diode, a certain forward bias voltage needs to be formed at both ends of it before the rectifier diode can be turned on; this forward bias voltage is generally around 0.7V.

[0039] When the input AC current signal is rectified by the rectifier diode, the current greater than the bias voltage flows through the rectifier diode, and when it is lower than the bias voltage, the rectifier diode is cut off; the circuit is open. When using a rectifier diode, the current waveform passing through will be lost; only the current higher than the bias voltage can pass. Therefore, there will be a slight deviation when measuring voltage.

[0040] It should also be pointed out that: the diode, as a rectifying element, needs to be selected according to different rectification methods and load sizes. If the selection is inappropriate, it cannot work safely and may even burn out the diode. In this embodiment: if the voltage is large, one or more voltage-dividing resistors need to be connected in series to the rectifying diode; if the current is large, multiple rectifying diodes need to be used, and these rectifying diodes are connected in parallel, each rectifying diode is shunted, and the current flowing through each rectifying diode is averaged. Secondly, during measurement, since the characteristics of each diode are not completely consistent, the current passing through cannot be evenly divided; causing the risk of overcurrent burning of the diode, it is necessary to connect a resistor in series to each rectifying diode, and by adjusting the resistor, the current of each parallel branch is close to the same.

[0041] Furthermore, the rectifier circuit 2 includes a full-bridge rectifier circuit.

[0042] The use of rectifier diodes will cause more than half of the energy to be damaged. In order to avoid this energy loss, this technical solution adopts a full-bridge rectifier circuit. Under ideal conditions, both the positive half of the alternating current and the negative half of the alternating current can pass through the full-bridge rectifier circuit. However, since the diodes that constitute the full-bridge rectifier circuit have a bias voltage V0, the alternating current between -2V0 and 2V0 cannot pass through the full-bridge rectifier circuit, which will still cause measurement deviations.

[0043] Furthermore, the rectifier circuit 2 includes a half-wave precision rectifier circuit, which includes: an operational amplifier U1, the non-phase input terminal of the operational amplifier U1 is grounded through a resistor R5, the inverting input terminal of the operational amplifier U1 is connected to the input terminal of the rectifier circuit 2, the inverting input terminal of the operational amplifier U1 is connected to the output terminal of the operational amplifier U1 through a diode D1, and the output terminal of the diode D1 is connected to the output terminal of the rectifier circuit 2 through a diode D2; the inverting input terminal of the operational amplifier U1 is connected to the output terminal of the rectifier circuit 2 through a resistor R4.

[0044] The half-wave precision rectifier circuit rectifies the input AC power to obtain a half-wave waveform. During operation, 1. When the positive half of the AC waveform is input, since diode D1 is connected in series with diode D2 and in parallel with resistor R4, the resistance of diodes D1 and D2 is much smaller than the resistance of resistor R4, and the current no longer flows through resistor R4; diode D1 will be turned on, operational amplifier U1 will act as an inverter, and the voltage at the output end of operational amplifier U1 will be negative, which will cause diode D2 to be cut off, and the output end of rectifier circuit 2 will be 0 potential; 2. When the negative half of the AC waveform is input, diode D1 is in a reverse biased state, and the current will flow through resistor R4. At the same time, the output end of operational amplifier U1 is a positive voltage, so the output end of rectifier circuit 2 has a potential, and because of the negative feedback of resistor R4, operational amplifier U1 will compensate for the 0.7V voltage drop of diode D2, so that the waveform at the output end of rectifier circuit 2 corresponds to the input waveform.

[0045] In addition to the above, the half-wave rectifier circuit can also directly use a diode for rectification. Secondly, the rectifier circuit 2 can also be a full-wave rectifier circuit, such as a full-bridge rectifier circuit.

[0046] Furthermore, the transformer unit 1 comprises a voltage transformer P1; one input end of the voltage transformer is connected to the live wire of the alternating current through a voltage dividing resistor R1, and the other input end of the voltage transformer is connected to the neutral wire of the alternating current through a voltage dividing resistor R2.

[0047] The combination of voltage transformer P1, voltage-dividing resistor R1 and voltage-dividing resistor R2 can effectively reduce the high voltage. First, the impedance of voltage transformer P1 is very small. After being connected in series with voltage-dividing resistor R1 and voltage-dividing resistor R2, the voltage at the input end of voltage transformer P1 is relatively small. After the voltage transformer itself is transformed, the voltage at its output end is basically within a safe range, such as AC12V, AC5V, etc.

[0048] Furthermore, a high-voltage protection circuit 4 is included, and the high-voltage protection circuit 4 is arranged between the transformer unit 1 and the rectifier circuit 2 .

[0049] The high-voltage protection circuit 4 is used to prevent the voltage of the input rectifier circuit 2 from being too high and damaging the subsequent circuits.

[0050] Preferably, the high-voltage protection circuit 4 includes a TVS tube, and two ends of the TVS tube are respectively connected to two output ends of the transformer unit 1 .

[0051] The use of a TVS tube can prevent the input voltage from being too high; when the voltage is too high, the TVS tube is broken down to form a short circuit. More preferably, the TVS tube is connected in parallel with a resistor R3. Resistor R3 can prevent the two output ends of the voltage transformer from being directly short-circuited when the TVS tube is broken down, thereby protecting the voltage transformer. In a specific setting, one end of the TVS tube is connected to the output end of the high-voltage protection circuit 4, and the other end of the TVS tube is grounded.

[0052] Furthermore, a capacitor C1 is connected between the high-voltage protection circuit 4 and the rectifier circuit 2 .

[0053] Capacitor C1 blocks direct current and allows alternating current to pass through, and also acts as a filter.

[0054] Furthermore, the filter circuit 3 includes a resistor R6, one end of which is connected to the output end of the rectifier circuit 2, and the other end of which is grounded through a capacitor unit; the other end of the resistor R6 is also connected to the output end of the filter circuit 3.

[0055] The capacitor unit may be a single capacitor or a plurality of capacitors connected in parallel. In this embodiment, the capacitor unit includes capacitors C2 and C3 connected in parallel. The capacitor unit filters the rectified current signal to eliminate the background signal in the current signal.

[0056] Embodiment 2: The main difference from Embodiment 1 is that the rectifier circuit 2 is a full-wave rectifier circuit, see Figure 3 .

[0057] The full-wave rectifier circuit includes: an operational amplifier U1 and an operational amplifier U2; the input end of the full-wave rectifier circuit is connected to the inverting input end of the operational amplifier U1 and the inverting input end of the operational amplifier U2 through resistors R7 and R8 respectively; the inverting input end of the operational amplifier U1 is connected to the output end of the operational amplifier U1 through a diode D1, the output end of the operational amplifier U1 is connected to a diode D2, and the inverting input end of the operational amplifier U1 is connected to the output end of the diode D2 through a resistor R4; the output end of the diode D2 is connected to the inverting input end of the operational amplifier U2 through a resistor R6; the inverting input end of the operational amplifier U2 is connected to the output end of the operational amplifier U2 through a resistor R9.

[0058] When the full-wave rectifier circuit is working, for the convenience of analysis, the input AC power is divided into two parts: the positive half and the negative half for analysis.

[0059] When the input is the positive half of the alternating current, the output terminal of the operational amplifier U1 is a negative voltage, and the diode D2 is cut off. Combining the content of Example 1, it can be known that the potential of the output terminal of the diode D2 is 0; then the potential of the output terminal of the resistor R6 is 0. At this time, the alternating current can only pass through the resistor R8, the operational amplifier U2, and the resistor R9 to output the amplified negative voltage.

[0060] For the convenience of calculation, the resistance values ​​of resistors R9 and R8 can be set equal, that is, resistance R9=R8. The potential of the input AC power is V0, and the potential of the output terminal of the operational amplifier U2 is -V0.

[0061] When the input is the negative half of the AC power, Figure 3 It can be seen that the input end of the diode D1 is at a negative potential, so the diode D1 is cut off; at the same time, the alternating current is amplified by the inverting amplifier U1, the output end of the operational amplifier U1 is at a positive potential, the diode D2 is turned on and has an output current to the outside; therefore, there are two currents flowing into the inverting input end of the operational amplifier U2, one of which is through the resistor R6; the other is through the resistor R8.

[0062] For the convenience of calculation, these two paths are calculated separately; for the first path, the resistance values ​​of resistors R4 and R7 are set to be equal, that is, R4=R7; the potential of the input alternating current is V0, the potential of the output end of diode D2 is -V0, and the current flows through resistor R6, operational amplifier U2 and resistor R9, and the potential at the output end of operational amplifier U2 is: R9 / R6*V0.

[0063] As for the description of the second alternating current, when the input is the positive half of the alternating current, it can be seen that the output potential after passing through resistor R8, operational amplifier U2, and resistor R9 is: -V0.

[0064] For the convenience of calculation, R9=2R6 is continued to be set, then the comprehensive potential at the output end of the operational amplifier U2 is 2V0+(-V0)=V0; that is, it is equal to the input potential of the alternating current.

[0065] In summary, by setting the resistance ratio of resistors R7, R4, R6, R8, and R9, we can obtain: when the input is the positive half of the alternating current, the potential of the input alternating current is V0, and the potential of the output terminal of the operational amplifier U2 is -V0; when the input is the negative half of the alternating current, the potential of the input alternating current is -V0, and the potential of the output terminal of the operational amplifier U2 is -V0. This makes detection convenient.

[0066] Preferably, the resistance values ​​of the resistors R4 and R7 are equal; the resistance value of the resistor R9 is twice the resistance value of the resistor R6; and the resistance values ​​of the resistor R9 and the resistor R8 are equal.

[0067] Embodiment 2 is different from Embodiment 1 in that:

[0068] The filter circuit includes a capacitor C2 and a capacitor C3 connected in parallel.

[0069] The filter circuit directly uses capacitors C2 and C3 for filtering, which is simple and convenient.

[0070] The filter circuit eliminates background clutter in the full-wave rectifier circuit to improve the accuracy of MCU detection.

[0071] Finally, the applicant needs to explain that: in addition to the basic circuit designed in this application, the full-wave rectifier circuit can also be equipped with a filter circuit and the like.

[0072] Secondly, the MCU can also set up analog-to-digital conversion circuits during detection; these are all existing technologies and will not be described in detail here. If a voltmeter is used, a voltage follower circuit is added to eliminate the influence of impedance when the voltmeter is measuring.

[0073] The embodiments described above 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, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such 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. An AC voltage measurement circuit, characterized in that: It includes: A transformer unit, the input end of which is electrically connected to the AC power via a plurality of voltage-dividing resistors; A rectifier circuit, electrically connected to the output end of the transformer unit; A filter circuit is electrically connected to the output end of the rectifier circuit; A measuring unit, electrically connected to the filter circuit, for measuring voltage; The voltage transformation unit includes a voltage transformer P1; one input end of the voltage transformer is connected to the live wire of the alternating current through a voltage dividing resistor R1, and the other input end of the voltage transformer is connected to the neutral wire of the alternating current through a voltage dividing resistor R2.

2. An AC voltage measurement circuit as claimed in claim 1, characterized in that: The rectifier circuit includes a half-wave precision rectifier circuit, which includes: an operational amplifier U1, a non-phase input terminal of the operational amplifier U1 is grounded through a resistor R5, an inverting input terminal of the operational amplifier U1 is connected to an input terminal of the rectifier circuit, an inverting input terminal of the operational amplifier U1 is connected to an output terminal of the operational amplifier U1 through a diode D1, an output terminal of the diode D1 is connected to an output terminal of the rectifier circuit through a diode D2; and an inverting input terminal of the operational amplifier U1 is connected to an output terminal of the rectifier circuit through a resistor R4.

3. An AC voltage measurement circuit as claimed in claim 1, characterized in that: The rectifier circuit includes a full-wave rectifier circuit.

4. An AC voltage measurement circuit as claimed in claim 1, characterized in that: It also includes a high-voltage protection circuit, which is arranged between the transformer unit and the rectifier circuit.

5. An AC voltage measurement circuit as claimed in claim 4, characterized in that: The high-voltage protection circuit includes a TVS tube, and two ends of the TVS tube are respectively connected to two output ends of the transformer unit.

6. An AC voltage measurement circuit as claimed in claim 4 or 5, characterized in that: A capacitor C1 is connected between the high voltage protection circuit and the rectifier circuit.

7. An AC voltage measurement circuit as claimed in claim 1 or 2, characterized in that: The filter circuit comprises a resistor R6, one end of which is connected to the output end of the rectifier circuit, and the other end of which is grounded via a capacitor unit; the other end of the resistor R6 is connected to the output end of the filter circuit.

8. An AC voltage measurement circuit as claimed in claim 7, characterized in that: The capacitor unit includes a capacitor C2 and a capacitor C3 connected in parallel.

9. An AC voltage measurement circuit as claimed in claim 3, characterized in that: The full-wave rectifier circuit includes: an operational amplifier U1 and an operational amplifier U2; the input end of the full-wave rectifier circuit is connected to the inverting input end of the operational amplifier U1 and the inverting input end of the operational amplifier U2 through resistors R7 and R8 respectively; the inverting input end of the operational amplifier U1 is connected to the output end of the operational amplifier U1 through a diode D1, the output end of the operational amplifier U1 is connected to a diode D2, and the inverting input end of the operational amplifier U1 is connected to the output end of the diode D2 through a resistor R4; the output end of the diode D2 is connected to the inverting input end of the operational amplifier U2 through a resistor R6; the inverting input end of the operational amplifier U2 is connected to the output end of the operational amplifier U2 through a resistor R9.

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