True RMS conversion system and method

Abstract

The invention provides a true RMS conversion system and method, and belongs to the technical field of signal processing.The true RMS conversion system comprises an amplitude limiting protection module, a signal shaping module and a filtering module, and the circuit structure is simplified. The amplitude limiting protection module, the signal shaping module and the filtering module mainly utilize a low-cost operational amplifier, a diode, a resistor, a capacitor and other components to realize the function of true RMS conversion of any complex signal, and have the advantages of simple circuit structure, reliable performance, low cost and high response speed.

Description

Technical Field

[0001] The present invention belongs to the technical field of signal processing, relates to true root mean square (RMS) conversion technology, and specifically provides a true RMS conversion system and method. Background Art

[0002] True RMS refers to the root mean square value of voltage, which can reflect the RMS value of positive and negative voltages and will not produce different errors due to different waveforms. Currently, mainstream products all use imported ADC integrated conversion chips to convert alternating current (AC) signals into direct current (DC) signals. The core device is an RMS-TO-DC converter, which is realized through a complete monolithic integrated circuit. The working principle is as follows: The input AC voltage is converted into a voltage within the input voltage range of the converter through a signal processing circuit. The input voltage enters a complex RMS-DC conversion circuit, and a DC voltage signal representing the true RMS of the AC voltage is output. Then, after passing through a protection circuit, it enters an AD converter. After AD conversion, the microcontroller reads the AD conversion result to obtain the true RMS of the AC voltage. Although this monolithic integrated circuit can realize the conversion from AC signals to DC signals, its internal circuit structure is complex. Especially after the requirements for domestic products are upgraded, there are currently few available types and they are expensive, resulting in a high equipment cost for the true RMS detector prepared therefrom, which limits the development of low-cost and high-reliability domestic circuits. Summary of the Invention

[0003] In view of the problems described in the above background art, such as the complex internal circuit structure, high production cost, and few types of existing domestic RMS-TO-DC converters, the present invention proposes a true RMS conversion system and method to address this problem.

[0004] The present invention proposes a replacement solution different from the complex monolithic integrated RMS-TO-DC converter, and uses a limiting protection module, a signal shaping module, and a filtering module for true RMS conversion, which simplifies the conversion circuit structure and increases its reliability. Among them, the limiting protection module, the signal shaping module, and the filtering module mainly use low-cost operational amplifiers, diodes, resistors, capacitors and other components to realize the function of true RMS conversion for any complex signal, and have the advantages of simple circuit structure, reliable performance, low cost, and high response speed. It can be widely promoted to the further development of low-cost and high-reliability domestic circuits.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A true RMS conversion system of the present invention includes a limiting protection module, a signal shaping module, and a filtering module connected in sequence along the transmission direction of the electrical signal;

[0007] The clipping protection module is used to perform clipping protection on the out-of-range voltage signal in the input signal, so that the out-of-range voltage signal in the input signal matches the voltage signal range of the signal shaping module, form a clipped signal, and send the clipped signal to the signal shaping module;

[0008] The signal shaping module is used to receive the clipped signal, process the clipped signal into a positive level signal, and send the positive level signal to the filtering module;

[0009] The filtering module is used to receive the positive level signal, perform filtering processing on the positive level signal to obtain a direct current signal, and realize the conversion of true root mean square value.

[0010] Further defined, the true root mean square conversion system further includes an ADC sampling module. The ADC sampling module is connected to the filtering module and is used to obtain the direct current signal of the filtering module and convert the direct current signal into a binary code for output.

[0011] Further defined, the clipping protection module includes a resistor R1, a resistor R2, and a zener diode D1.

[0012] One end of the resistor R1 is the input terminal of the input signal;

[0013] The other end of the resistor R1 is respectively connected to one end of the resistor R2 and one end of the zener diode D1, and the formed connection terminal is used to output the clipped signal;

[0014] The other end of the resistor R2 is connected to the other end of the zener diode D1, and the formed connection terminal is grounded.

[0015] Further defined, the relationship between the out-of-range voltage signal in the input signal and the voltage signal range of the signal shaping module is:

[0016]

[0017] In the formula, R2 is the resistance value of the resistor R2, unit: Ω; R1 is the resistance value of the resistor R1, unit: Ω; V cm is the maximum output voltage value of the voltage signal in the signal shaping module, unit: V; V imax is the maximum voltage value of the out-of-range voltage signal in the input signal, unit: V.

[0018] Further defined, the signal shaping module includes an operational amplifier U1A, a diode D2, a diode D3, a capacitor C1, a resistor R3, a resistor R4, a resistor R5, and an operational amplifier U1B.

[0019] The positive input terminal of the operational amplifier U1A is the input terminal of the signal after amplitude limiting; the negative input terminal of the operational amplifier U1A is respectively connected to one end of the diode D2, one end of the capacitor C1, and one end of the resistor R3; the output terminal of the operational amplifier U1A is respectively connected to the other end of the diode D2, the other end of the capacitor C1, and one end of the diode D3;

[0020] The other end of the resistor R3 is respectively connected to one end of the resistor R4 and the negative input terminal of the operational amplifier U1B;

[0021] The other end of the resistor R4 is connected to the output terminal of the operational amplifier U1B, and the output terminal of the operational amplifier U1B is used to output a positive level signal;

[0022] The other end of the diode D3 is respectively connected to one end of the resistor R5 and the positive input terminal of the operational amplifier U1B;

[0023] The other end of the resistor R5 is grounded.

[0024] Further defined, the filtering module is a second-order Butterworth low-pass filter.

[0025] A true RMS conversion method of the present invention is applied to the above-mentioned true RMS conversion system, including the following steps:

[0026] S1: Receive an input signal, perform amplitude limiting protection on the out-of-range voltage signal in the input signal, so that the out-of-range voltage signal in the input signal matches the voltage signal range of the signal shaping module, and form a signal after amplitude limiting;

[0027] S2: Process the signal after amplitude limiting into a positive level signal;

[0028] S3: Perform filtering processing on the positive level signal to obtain a DC signal, and realize the conversion of true RMS.

[0029] Further defined, the true RMS conversion method further includes S4: Output the DC signal.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. A true RMS conversion system of the present invention proposes an alternative solution different from complex monolithic integrated RMS-TO-DC converters. It uses a limiter protection module, a signal shaping module, and a filtering module to perform true RMS conversion, simplifying the circuit structure. Among them, the limiter protection module, the signal shaping module, and the filtering module mainly use low-cost components such as operational amplifiers, diodes, resistors, and capacitors to achieve the function of true RMS conversion for any complex signal, having the advantages of simple circuit structure, reliable performance, low cost, and high response speed. It can be widely promoted to the further development of low-cost and high-reliability domestic circuits and has broad market application prospects.

[0032] 2. In the present invention, the voltage signal in the input signal is matched with the voltage signal range of the signal shaping module, and an operational amplifier with an appropriate bandwidth can be selected according to the voltage signal in the input signal. That is, when the output signal of the detection object is low-frequency, an operational amplifier with a lower bandwidth can be selected to reduce the circuit cost; when the output signal of the detection object is high-frequency, the resistance R1 and the resistance R2 can be selected according to the voltage range of the input signal in combination with the input voltage range of the operational amplifier, which can reduce the equipment cost.

[0033] 3. A true RMS conversion system of the present invention uses a limiter protection module to limit and protect the out-of-range voltage signal in the input signal, so that the out-of-range voltage signal of the input signal is within the input range of the operational amplifier, playing a protective role for the entire circuit system; under the action of the signal shaping module, the negative level signal in the limited signal (AC signal) is flipped to obtain a DC signal with all positive level signals; then under the action of the filtering module, the DC signal that is not suitable for the ADC sampling module is converted into a true RMS value and then output to the ADC sampling module, reducing the requirements and sampling rate for the ADC sampling module. The present invention converts an AC signal into a true RMS value for the ADC sampling module to sample through the limiter protection module, the signal shaping module, and the filtering module. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a schematic structural diagram of the true RMS conversion system of the present invention;

[0035] Figure 2 is a schematic internal circuit structure diagram of the limiter protection module;

[0036] Figure 3 is a schematic internal circuit structure diagram of the signal shaping module;

[0037] Figure 4 is a schematic internal circuit structure diagram of the filtering module;

[0038] Figure 5 is a flowchart of the true RMS conversion circuit system;

[0039] Figure 6 The simulation circuit diagram used for the multisim simulation of the true RMS conversion system of the present invention;

[0040] Figure 7 Two simulation waveform diagrams formed by the multisim simulation of the true RMS conversion system of the present invention. Among them, (a) is the first simulation waveform diagram, and (b) is the second simulation waveform diagram. Detailed implementation manners

[0041] The technical solution of the present invention will be further explained below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited to the following described embodiments.

[0042] See Figure 1 , a true RMS conversion system of the present invention includes a limiter protection module, a signal shaping module, and a filtering module connected in sequence along the transmission direction of the electrical signal; specifically, the output signal of the limiter protection module is the input signal of the signal shaping module, and the output signal of the signal shaping module is the input signal of the filtering module.

[0043] The limiter protection module is connected to the input signal and receives the input signal at the same time. It is used to perform limiter protection on the out-of-range voltage signal in the input signal, so that the out-of-range voltage signal in the input signal matches the voltage signal range of the signal shaping module. It has a limiter protection function, forms a limited signal, and sends the limited signal to the signal shaping module.

[0044] The signal shaping module is used to receive the limited signal, process the limited signal into a positive level signal, and send the positive level signal to the filtering module; specifically, the signal shaping module flips the negative level signal in the limited signal into a positive level signal and directly outputs the positive level signal in the limited signal, so that all the outputs are positive level signals.

[0045] The filtering module is used to receive the positive level signal, perform filtering on the positive level signal, and obtain a DC electrical signal to achieve the conversion of the true RMS; preferably, the filtering module is a second-order Butterworth low-pass filter. In addition, it can also be other filters well-known to those skilled in the art.

[0046] Preferably, a true RMS conversion system of the present invention further includes an ADC sampling module. The ADC sampling module is connected to the filtering module and is used to obtain the DC electrical signal of the filtering module and convert the DC electrical signal into a binary code for output.

[0047] A true RMS conversion system of the present invention limits and protects out-of-range voltage signals in an input signal through a limiter protection module, so that the out-of-range voltage signals in the input signal are within the input range of an operational amplifier, playing a protective role for the entire circuit system; under the action of a signal shaping module, negative level signals in the limited signal (AC signal) are flipped to obtain a DC signal with all positive level signals; then, under the action of a filtering module, the DC signal unsuitable for an ADC sampling module is converted into a true RMS value, and thus output to the ADC sampling module, reducing the requirements and sampling rate for the ADC sampling module. The present invention converts an AC signal into a true RMS value through a limiter protection module, a signal shaping module and a filtering module for sampling by the ADC sampling module.

[0048] See Figure 2 , in the present invention, the limiter protection module includes a resistor R1, a resistor R2 and a zener diode D1. One end of the resistor R1 is the input end of the input signal, and the other end of the resistor R1 is respectively connected to one end of the resistor R2 and one end of the zener diode D1, and the formed connection end is used to output the limited signal; the other end of the resistor R2 is connected to the other end of the zener diode D1, and the formed connection end is grounded. According to the input voltage and the maximum input voltage when the operational amplifier U1 works normally, a suitable resistor network (i.e., resistor R1 and resistor R2) is selected. The resistor R1 is connected in series in the circuit, which not only plays the role of voltage division of the resistor network, but also plays a role in current limiting protection. The selection of the zener diode D1 is mainly determined by the output voltage of the operational amplifier U1. When there is an abnormal voltage at the output, the abnormal voltage is suppressed by the zener diode D1 and output to the operational amplifier U1, so as to achieve the function of abnormal voltage protection and realize the current limiting and abnormal voltage protection functions of the input signal.

[0049] Preferably, the relationship between the out-of-range voltage signal in the input signal and the voltage signal range of the signal shaping module is:

[0050]

[0051] In the formula, R2 is the resistance value of the resistor R2, unit: Ω; R1 is the resistance value of the resistor R1, unit: Ω; V cm is the maximum output voltage value of the voltage signal in the signal shaping module, unit: V; V imax is the maximum voltage value of the out-of-range voltage signal in the input signal, unit: V.

[0052] See Figure 3, in the present invention, the signal shaping module includes operational amplifier U1A, diode D2, diode D3, capacitor C1, resistor R3, resistor R4, resistor R5, and operational amplifier U1B. The positive input terminal of operational amplifier U1A is the input terminal of the limited amplitude signal (input signal); the negative input terminal of operational amplifier U1A is connected to one end of diode D2, one end of capacitor C1, and one end of resistor R3 respectively; the output terminal of operational amplifier U1A is connected to the other end of diode D2, the other end of capacitor C1, and one end of diode D3 respectively; the other end of resistor R3 is connected to one end of resistor R4 and the negative input terminal of operational amplifier U1B respectively; the other end of resistor R4 is connected to the output terminal of operational amplifier U1B, and the output terminal of operational amplifier U1B is used to output a positive level signal (output signal); the other end of diode D3 is connected to one end of resistor R5 and the positive input terminal of operational amplifier U1B respectively; the other end of resistor R5 is grounded.

[0053] According to the characteristics that the in-phase and anti-phase input terminals of the operational amplifier are "virtually short-circuited", and when the input signal is applied to the positive input terminal, the output polarity does not change, while when the input signal is applied to the anti-phase input terminal, the output polarity changes. The voltages and waveforms at the anti-phase input terminal and the positive input terminal of operational amplifier U1A are the same (both are the voltages after voltage division of the input voltage). When the input terminal signal is a positive voltage, the input signal passes through U1A → D2 → D3 → U1B to the output, and the positive and negative polarities of the signal do not change. When the input signal is a negative voltage, the input signal passes through U1A → R3 → R4 → to the output. Since the input signal is applied to the anti-phase terminal of operational amplifier U1A, the polarity of the output signal is reversed, thus flipping the input negative voltage into a positive voltage, and obtaining a signal that is all positive voltage, realizing the function of signal shaping.

[0054] See Figure 4 , in the present invention, the filtering module includes resistor R6, resistor R7, capacitor C2, capacitor C3, and operational amplifier U1C. One end of resistor R6 is the input terminal of the positive level signal (input signal), the other end of resistor R6 is connected to one end of resistor R7 and one end of capacitor C2 respectively, the other end of resistor R7 is connected to the positive input terminal of operational amplifier U1C and one end of capacitor C3 respectively; the other end of capacitor C3 is grounded; the other end of capacitor C2 is connected to the output terminal of operational amplifier U1C; the negative input terminal of operational amplifier U1C is connected to the output terminal of operational amplifier U1C, and the output terminal of operational amplifier U1C is the output terminal of the direct current signal (output signal).

[0055] The filtering module is a low-pass active filter composed of R6, resistor R7, capacitor C2, capacitor C3, and operational amplifier U1C, which filters the input non-direct current signal to obtain the required direct current signal.

[0056] In the present invention, the amplitude limiting protection module, the signal shaping module and the filtering module mainly utilize low-cost components such as operational amplifiers, diodes, resistors and capacitors to realize the function of true root mean square (RMS) conversion for any complex signal, and have the advantages of simple circuit structure, reliable performance, low cost and high response speed. It can be widely promoted to the further development of low-cost and high-reliability domestic circuits, and has broad market application prospects.

[0057] See Figure 5 , a true RMS conversion method of the present invention, which is applied to the above-mentioned true RMS conversion system, includes the following steps:

[0058] S1: Receive an input signal, perform amplitude limiting protection on the out-of-range voltage signal in the input signal, so that the out-of-range voltage signal in the input signal matches the voltage signal range of the signal shaping module, and form a signal after amplitude limiting;

[0059] S2: Shape the AC (negative level) signal in the signal after amplitude limiting into a DC (positive level) signal;

[0060] S3: Perform filtering on the positive level signal to obtain a DC electrical signal, and realize the conversion of true RMS.

[0061] Preferably, a true RMS conversion method of the present invention further includes S4: Convert the DC electrical signal into a binary code and output it.

[0062] See Figure 6 , which is the simulation circuit diagram of the present invention. The circuit composed of operational amplifier U1A and operational amplifier U1B inverts the negative level signal in the input signal to form a DC signal; operational amplifier U2A is an active low-pass filter circuit, which filters the DC signal into a DC level signal to obtain the required signal.

[0063] See Figure 7 (a) and Figure 7 (b), Figure 7 In (a), the red curve is the input signal (test object), the black curve is the DC signal after passing through the signal shaping module, and the green is the DC level signal obtained after filtering by the filtering module. Figure 7 (b) is based on Figure 7 (a), and tests the AC component of the DC level signal after filtering by the filtering module, where the green curve is the AC component of the output DC level signal. As can be seen from Figure 7 (b), the AC component of the DC level signal in the output signal is less than ±1 mV, while the output signal of the signal shaping module is ±1 V, and the filtering effect of the filtering module is better. This shows that the designed circuit is effective and can be used in most AC-to-DC applications.

[0064] The above embodiments are only used to illustrate the technical solutions of the present application, rather than limiting the present application; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A true effective value conversion system, characterized in that: It includes a limiting protection module, a signal shaping module and a filtering module which are sequentially connected along the transmission direction of the electrical signal; The limiting protection module is used to perform limiting protection on the out-of-range voltage signal in the input signal, so that the out-of-range voltage signal in the input signal matches the voltage signal range of the signal shaping module, forms a limited signal, and sends the limited signal to the signal shaping module; The signal shaping module is used to receive the limited signal, process the limited signal into a positive level signal, and send the positive level signal to the filtering module; The filtering module is used to receive a positive level signal, filter the positive level signal, obtain a direct current signal, and realize true effective value conversion.

2. The true effective value conversion system according to claim 1, characterized in that: The true effective value conversion system also includes an ADC sampling module, which is connected to the filter module and is used to obtain the direct current signal of the filter module and convert the direct current signal into a binary code for output.

3. The true effective value conversion system according to claim 1, characterized in that: The amplitude limiting protection module includes a resistor R1, a resistor R2 and a voltage stabilizing diode D1. One end of the resistor R1 is the input end of the input signal; The other end of the resistor R1 is connected to one end of the resistor R2 and one end of the voltage stabilizing diode D1 respectively, and the formed connection end is used to output the limited signal; The other end of the resistor R2 is connected to the other end of the Zener diode D1 , and the formed connection end is grounded.

4. The true effective value conversion system according to claim 3, characterized in that: The relationship between the out-of-range voltage signal in the input signal and the voltage signal range matching of the signal shaping module is: Wherein, R2 is the resistance value of resistor R2, unit: Ω; R1 is the resistance value of resistor R1, unit: Ω; V cm It is the maximum output voltage value of the voltage signal in the signal shaping module, unit: V; V imax It is the maximum voltage value of the out-of-range voltage signal in the input signal, unit: V.

5. The true effective value conversion system according to claim 1, characterized in that: The signal shaping module includes an operational amplifier U1A, a diode D2, a diode D3, a capacitor C1, a resistor R3, a resistor R4, a resistor R5 and an operational amplifier U1B. The positive input terminal of the operational amplifier U1A is the input terminal of the limited signal; the negative input terminal of the operational amplifier U1A is respectively connected to one end of the diode D2, one end of the capacitor C1 and one end of the resistor R3; the output terminal of the operational amplifier U1A is respectively connected to the other end of the diode D2, the other end of the capacitor C1 and one end of the diode D3; The other end of the resistor R3 is connected to one end of the resistor R4 and the negative input terminal of the operational amplifier U1B respectively; The other end of the resistor R4 is connected to the output end of the operational amplifier U1B, and the output end of the operational amplifier U1B is used to output a positive level signal; The other end of the diode D3 is connected to one end of the resistor R5 and the positive input terminal of the operational amplifier U1B respectively; The other end of the resistor R5 is grounded.

6. The true effective value conversion system according to claim 1, characterized in that: The filtering module is a second-order Butterworth low-pass filter.

7. A true effective value conversion method, applied to the true effective value conversion system according to claim 1, characterized in that: The following steps are involved: S1: receiving input signals, performing amplitude limiting protection on the over-range voltage signals in the input signals, so that the over-range voltage signals in the input signals match the voltage signal range of the signal shaping module, and forming the amplitude limited signal; S2: Process the limited signal into a positive level signal; S3: Filter the positive level signal to obtain a DC signal to achieve true effective value conversion.

8. The true effective value conversion method according to claim 7, characterized in that: The true effective value conversion method further includes S4: converting the direct current signal into a binary code output.

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