AC voltage measuring circuit

Abstract

The utility model discloses an AC voltage measuring circuit, which comprises an AC voltage input coupling step-down circuit, a voltage bias reference circuit and a differential voltage signal processing output circuit, and is characterized in that the differential voltage signal processing output circuit comprises an operational amplifier U1A, a pin 2 and a pin 3 of the operational amplifier U1A are respectively connected with the AC voltage input coupling step-down circuit; the third pin of the operational amplifier U1A is further connected with a voltage bias reference circuit, the first pin of the operational amplifier U1A is connected with one end of a resistor R7, and the other end of the resistor R7 is connected with an ADC sampling input pin of a post-stage MCU. According to the utility model, the differential voltage signal processing output circuit converts small L and N phase alternating voltage signals after coupling and voltage reduction into alternating voltage signals with reference bias voltage as a zero point, and outputs the alternating voltage signals, so that the ADC of a post-stage MCU carries out sampling and calculation processing, the measurement of alternating voltage is realized, and the circuit has the characteristics of simple structure, high reliability and low cost.

Description

Technical Field

[0001] This utility model belongs to the field of AC voltage measurement technology, and specifically relates to an AC voltage measurement circuit. Background Technology

[0002] In electronics, how to measure AC voltage using a low-cost and simple circuit has become a key aspect of product design.

[0003] Current solutions all use a combination of voltage transformers and dedicated metering chips to measure voltage, but this approach suffers from high hardware costs and significant circuit redundancy.

[0004] For applications with high hardware cost requirements, finding a safe, low-cost, and simple circuit to measure AC voltage becomes a key aspect of product design. Therefore, an AC voltage measurement circuit is proposed. Utility Model Content

[0005] The purpose of this invention is to provide an AC voltage measurement circuit to solve the problems mentioned in the background section. The AC voltage measurement circuit provided by this invention features simple structure, high reliability, and low cost.

[0006] To achieve the above objectives, this utility model provides the following technical solution: an AC voltage measurement circuit, comprising an AC voltage input coupling step-down circuit, a voltage bias reference circuit, and a differential voltage signal processing output circuit. The differential voltage signal processing output circuit includes an operational amplifier U1A. Pins 2 and 3 of the operational amplifier U1A are connected to the AC voltage input coupling step-down circuit, pin 3 of the operational amplifier U1A is also connected to the voltage bias reference circuit, pin 4 of the operational amplifier U1A is connected to ground, pin 8 of the operational amplifier U1A is connected to a +12V power supply, a resistor R6 and a capacitor C6 are connected in parallel between pins 1 and 2 of the operational amplifier U1A, pin 1 of the operational amplifier U1A is connected to one end of a resistor R7, and the other end of the resistor R7 is connected to the ADC sampling input pin of the subsequent MCU.

[0007] To step down the L-phase input, the AC voltage input coupling step-down circuit further includes capacitors C1 and C2, resistors R1 and R2 connected in series. The other end of capacitor C1 is connected to the L-phase of the 220V AC power supply, and the other end of resistor R2 is connected to pin 2 of operational amplifier U1A.

[0008] To further reduce the voltage of the N-phase input, the AC voltage input coupling buck circuit also includes capacitors C3 and C4, resistors R3 and R4 connected in series. The other end of capacitor C3 is connected to the N-phase of the 220V AC power supply, and the other end of resistor R4 is connected to pin 3 of operational amplifier U1A.

[0009] For signal input clamping protection, the AC voltage input coupling buck circuit further includes diodes D1 and D2. Pin 1 of diode D1 is connected to ground, pin 2 of diode D1 is connected to the +12V power supply, and pin 3 of diode D1 is connected to pin 2 of op-amp U1A. Pin 1 of diode D2 is connected to ground, pin 2 of diode D2 is connected to the +12V power supply, and pin 3 of diode D2 is connected to pin 3 of op-amp U1A.

[0010] In order to boost the AC voltage zero-crossing point to the reference voltage so that the MCU's ADC can sample the effective amplitude range, the voltage bias reference circuit further includes a reference voltage chip U2. Pins 1 and 2 of the reference voltage chip U2 are connected to resistor R8 and pin 3 of operational amplifier U1A, respectively. The other end of resistor R8 is connected to the +5V power supply, and pin 3 of the reference voltage chip U2 is connected to the ground terminal.

[0011] To provide output filtering for the bias reference voltage, a capacitor C8 is connected in parallel between pins 2 and 3 of the reference voltage chip U2.

[0012] To provide filtering for the bias reference input, the differential voltage signal processing output circuit further includes a resistor R5 and a capacitor C5. One end of the resistor R5 is connected to pin 3 of the operational amplifier U1A, and the other end of the resistor R5 is connected to pin 2 of the reference voltage chip U2. The capacitor C5 is connected in parallel across the two ends of the resistor R5.

[0013] To perform signal output filtering, the differential voltage signal processing output circuit further includes capacitor C7. One end of capacitor C7 is connected to the ADC sampling input pin of the subsequent MCU, and the other end of capacitor C7 is connected to the ground terminal.

[0014] Compared with the prior art, the beneficial effects of this utility model are:

[0015] 1. This utility model converts the small L and N phase alternating voltage signals after coupling and voltage reduction into an alternating voltage signal with the reference bias voltage as the zero point through a differential voltage signal processing output circuit. This signal is then used by the ADC of the subsequent MCU for sampling and calculation, thereby realizing the measurement of AC voltage. It features simple structure, high reliability and low cost.

[0016] 2. The AC voltage input coupling step-down circuit of this utility model reduces the AC220V high voltage step-down ...

[0017] 3. This utility model provides a reference bias voltage through a voltage bias reference circuit, thereby raising the AC voltage zero-crossing point to the reference voltage so that the ADC pin of the MCU can sample the effective amplitude range. Attached Figure Description

[0018] Figure 1 This is the circuit diagram of this utility model. Detailed Implementation

[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0020] Example 1

[0021] Please see Figure 1 This utility model provides the following technical solution: an AC voltage measurement circuit, including an AC voltage input coupling step-down circuit, a voltage bias reference circuit, and a differential voltage signal processing output circuit. The differential voltage signal processing output circuit includes an operational amplifier U1A. Pins 2 and 3 of operational amplifier U1A are connected to the AC voltage input coupling step-down circuit, pin 3 of operational amplifier U1A is also connected to the voltage bias reference circuit, pin 4 of operational amplifier U1A is connected to ground, pin 8 of operational amplifier U1A is connected to a +12V power supply, and pin 1 of operational amplifier U1A... A resistor R6 and a capacitor C6 are connected in parallel between pin 1 and pin 2, respectively. Resistor R6 is the inverting proportional resistor of op-amp U1A with a resistance of 10KΩ, and capacitor C6 is the phase compensation capacitor for the AC input signal with a capacitance of 100nF. Pin 1 of op-amp U1A is connected to one end of resistor R7, and the other end of resistor R7 is connected to the ADC sampling input pin of the subsequent MCU. Op-amp U1A processes differential AC voltage signals and its model is LM2904DR2G. Resistor R7 is the impedance matching resistor for the signal output with a resistance of 2KΩ.

[0022] By adopting the above technical solution, this utility model converts the small L and N phase alternating voltage signals after coupling and voltage reduction into an alternating voltage signal with the reference bias voltage as the zero point through a differential voltage signal processing output circuit. This signal is then used by the ADC of the subsequent MCU for sampling and calculation, thereby realizing the measurement of AC voltage. It features simple structure, high reliability, and low cost.

[0023] Specifically, the AC voltage input coupling buck circuit includes capacitors C1 and C2, resistors R1 and R2 connected in series. The other end of capacitor C1 is connected to the L phase of the 220V AC power supply, and the other end of resistor R2 is connected to pin 2 of operational amplifier U1A.

[0024] By adopting the above technical solution, the L-phase input voltage is reduced.

[0025] Specifically, the AC voltage input coupling buck circuit also includes capacitors C3 and C4, resistors R3 and R4 connected in series. The other end of capacitor C3 is connected to the N phase of the 220V AC power supply, and the other end of resistor R4 is connected to pin 3 of op-amp U1A.

[0026] By adopting the above technical solution, the N-phase input voltage is reduced.

[0027] In this embodiment, capacitors C1, C2, C3, and C4 serve as coupling capacitors for the AC input, with a specification of 100nF / 450V; resistors R1, R2, R3, and R4 serve as series voltage divider resistors for the AC input, with a resistance value of 2MΩ.

[0028] Specifically, the voltage bias reference circuit includes a reference voltage chip U2, model TL431. Pins 1 and 2 of the reference voltage chip U2 are connected to resistor R8 and pin 3 of operational amplifier U1A, respectively. The other end of resistor R8 is connected to the +5V power supply. Pin 3 of the reference voltage chip U2 is connected to the ground terminal. Resistor R8 is the current limiting resistor of the bias reference circuit, with a resistance value of 1KΩ.

[0029] By adopting the above technical solution, the zero-crossing point of the AC voltage is raised to the reference voltage, so that the MCU's ADC can sample the effective amplitude range.

[0030] Specifically, a capacitor C8 with a capacitance of 100nF is connected in parallel between pins 2 and 3 of the reference voltage chip U2.

[0031] The above technical solution is used as the output filter capacitor for the bias reference voltage.

[0032] Example 2

[0033] The difference between this embodiment and Embodiment 1 is that, specifically, the AC voltage input coupling buck circuit further includes diodes D1 and D2. Pin 1 of diode D1 is connected to ground, pin 2 of diode D1 is connected to the +12V power supply, and pin 3 of diode D1 is connected to pin 2 of operational amplifier U1A. Pin 1 of diode D2 is connected to ground, pin 2 of diode D2 is connected to the +12V power supply, and pin 3 of diode D2 is connected to pin 3 of operational amplifier U1A. Both diodes D1 and D2 are Schottky diodes, model BAT54S.

[0034] The above technical solution is used for signal input clamping protection.

[0035] Example 3

[0036] The difference between this embodiment and embodiment 1 is that, specifically, the differential voltage signal processing output circuit also includes a resistor R5 and a capacitor C5. One end of the resistor R5 is connected to pin 3 of the operational amplifier U1A, and the other end of the resistor R5 is connected to pin 2 of the reference voltage chip U2. The capacitor C5 is connected in parallel across the two ends of the resistor R5.

[0037] By adopting the above technical solution, resistor R5 serves as the proportional resistor for the bias reference input of operational amplifier U1A, and the resistance value of resistor R5 is 10KΩ; capacitor C5 serves as the filter capacitor for the bias reference input, and the capacitance value of capacitor C5 is 100nF.

[0038] Specifically, the differential voltage signal processing output circuit also includes capacitor C7. One end of capacitor C7 is connected to the ADC sampling input pin of the subsequent MCU, and the other end of capacitor C7 is connected to the ground terminal.

[0039] By adopting the above technical solution, capacitor C7 is used as a signal output filter capacitor with a capacitance of 100nF.

[0040] In this invention, the L-phase and N-phase are stepped down to an AC voltage peak of approximately 0.5V after passing through an AC voltage input coupling step-down circuit. This voltage is then input to pin 2 (inverting input) and pin 3 (non-inverting input) of operational amplifier U1A. The voltage bias reference circuit outputs a 2.5V DC reference bias voltage, which is then output to pin 3 (non-inverting input) of operational amplifier U1A through resistor R5. Operational amplifier U1A lifts the zero-crossing point of the input differential AC voltage signal to the 2.5V DC reference voltage to meet the sampling range of the ADC for the DC component. This voltage is then output from pin 1 of U1A, and after passing through resistor R7, it is output to the ADC sampling input pin of the subsequent MCU for sampling and calculation processing by the subsequent MCU.

[0041] In summary, this invention uses a differential voltage signal processing output circuit to convert the small L and N phase alternating voltage signals, after coupling and step-down, into an alternating voltage signal with a reference bias voltage as the zero point. This signal is then used by the ADC of the subsequent MCU for sampling and calculation, enabling the measurement of AC voltage. It features a simple structure, high reliability, and low cost. The AC voltage input coupling step-down circuit of this invention uses RC and resistor-based voltage reduction to progressively step down the AC 220V high-voltage AC voltage, thus meeting the sampling input range of the subsequent low-voltage stage. Furthermore, this invention provides a reference bias voltage through a voltage bias reference circuit, lifting the AC voltage from its zero-crossing point to a reference voltage, facilitating sampling of the effective amplitude range by the MCU's ADC pin.

[0042] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An AC voltage measuring circuit, characterized in that: It includes an AC voltage input coupling buck circuit, a voltage bias reference circuit, and a differential voltage signal processing output circuit. The differential voltage signal processing output circuit includes an operational amplifier U1A. Pins 2 and 3 of the operational amplifier U1A are connected to the AC voltage input coupling buck circuit, pin 3 of the operational amplifier U1A is also connected to the voltage bias reference circuit, pin 4 of the operational amplifier U1A is connected to the ground terminal, pin 8 of the operational amplifier U1A is connected to the +12V power supply, a resistor R6 and a capacitor C6 are connected in parallel between pins 1 and 2 of the operational amplifier U1A, pin 1 of the operational amplifier U1A is connected to one end of a resistor R7, and the other end of the resistor R7 is connected to the ADC sampling input pin of the subsequent MCU.

2. The AC voltage measuring circuit according to claim 1, characterized in that: The AC voltage input coupling step-down circuit includes capacitors C1 and C2, resistors R1 and R2 connected in series. The other end of capacitor C1 is connected to the L phase of the 220V AC power supply, and the other end of resistor R2 is connected to pin 2 of operational amplifier U1A.

3. The AC voltage measuring circuit according to claim 2, characterized in that: The AC voltage input coupling step-down circuit also includes capacitors C3 and C4, resistors R3 and R4 connected in series. The other end of capacitor C3 is connected to the N phase of the 220V AC power supply, and the other end of resistor R4 is connected to pin 3 of operational amplifier U1A.

4. An AC voltage measuring circuit according to claim 3, characterized in that: The AC voltage input coupling buck circuit also includes diodes D1 and D2. Pin 1 of diode D1 is connected to ground, pin 2 of diode D1 is connected to the +12V power supply, and pin 3 of diode D1 is connected to pin 2 of operational amplifier U1A. Pin 1 of diode D2 is connected to ground, pin 2 of diode D2 is connected to the +12V power supply, and pin 3 of diode D2 is connected to pin 3 of operational amplifier U1A.

5. An AC voltage measuring circuit according to claim 1, characterized in that: The voltage bias reference circuit includes a reference voltage chip U2. Pins 1 and 2 of the reference voltage chip U2 are connected to resistor R8 and pin 3 of operational amplifier U1A, respectively. The other end of resistor R8 is connected to a +5V power supply, and pin 3 of the reference voltage chip U2 is connected to ground.

6. An AC voltage measuring circuit according to claim 5, characterized in that: A capacitor C8 is connected in parallel between pins 2 and 3 of the reference voltage chip U2.

7. An AC voltage measuring circuit according to claim 5, characterized in that: The differential voltage signal processing output circuit also includes a resistor R5 and a capacitor C5. One end of the resistor R5 is connected to pin 3 of the operational amplifier U1A, and the other end of the resistor R5 is connected to pin 2 of the reference voltage chip U2. The capacitor C5 is connected in parallel across the two ends of the resistor R5.

8. An AC voltage measuring circuit according to claim 1, characterized in that: The differential voltage signal processing output circuit also includes a capacitor C7. One end of the capacitor C7 is connected to the ADC sampling input pin of the subsequent MCU, and the other end of the capacitor C7 is connected to the ground terminal.

Images