CN216851941U - Anti-interference high-precision alternating current signal periodic sampling circuit - Google Patents
Anti-interference high-precision alternating current signal periodic sampling circuit Download PDFInfo
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- CN216851941U CN216851941U CN202123173283.4U CN202123173283U CN216851941U CN 216851941 U CN216851941 U CN 216851941U CN 202123173283 U CN202123173283 U CN 202123173283U CN 216851941 U CN216851941 U CN 216851941U
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Abstract
The utility model relates to an anti-interference high accuracy alternating current signal periodic sampling circuit for gather alternating current signal's cycle, including preceding stage schmitt comparison circuit, asymmetric filter circuit and schmitt trigger U201A, preceding stage schmitt comparison circuit's input and alternating current signal are connected, preceding stage schmitt comparison circuit's output is connected with asymmetric filter circuit's input, asymmetric filter circuit's output with schmitt trigger U201A's input is connected, schmitt trigger U201A's output is connected to control chip's input. The utility model provides an anti-interference high accuracy alternating current signal periodic sampling circuit, the periodic signal of its collection is accurate, has high anti-interference, high reliability.
Description
Technical Field
The utility model relates to a sampling circuit technical field especially relates to an anti-interference high accuracy alternating current signal periodic sampling circuit.
Background
The existing alternating current signal period sampling generally includes acquiring a positive zero crossing point and a negative zero crossing point of an alternating current signal, calculating a time interval of the two zero crossing points, wherein the time interval of the two zero crossing points is half of the period of the alternating current signal, and further obtaining the period of the alternating current signal; however, the above-mentioned acquisition method has the following problems: when the negative zero crossing point is acquired, if negative interference exists in the acquisition circuit, the acquired negative zero crossing point is prone to be inaccurate, and further, the measured periodic data has large errors, and the accuracy of the measurement result is affected. In order to improve accuracy, a low-pass filter is required to be added in a conventional periodic sampling circuit to filter out high-frequency signals, and the circuit is complex and inconvenient to use.
SUMMERY OF THE UTILITY MODEL
In order to solve the problem, the utility model provides an anti-interference high accuracy alternating current signal periodic sampling circuit, its periodic signal who gathers is accurate, has the characteristics of high anti-interference, high reliability.
The utility model adopts the technical proposal that: the period for collecting alternating current signals comprises a preceding-stage Schmitt comparison circuit, an asymmetric filter circuit and a Schmitt trigger U201A, wherein the input end of the preceding-stage Schmitt comparison circuit is connected with alternating current signals, the output end of the preceding-stage Schmitt comparison circuit is connected with the input end of the asymmetric filter circuit, the output end of the asymmetric filter circuit is connected with the input end of the Schmitt trigger U201A, and the output end of the Schmitt trigger U201A is connected to the input end of a control chip.
As a further limitation to the above technical solution, the preceding schmitt comparator circuit includes a resistor R109, a resistor R106, a diode D30, and an operational amplifier U20B, one end of the resistor R109 is connected to an ac signal, the other end of the resistor R109 is connected to a positive input terminal of the operational amplifier U20B and one end of the resistor R106, the other end of the resistor R106 is connected to a cathode of the diode D30, an anode of the diode D30 is connected to an output terminal of the operational amplifier U20B, and a negative input terminal of the operational amplifier U20B is grounded.
As a further limitation to the above technical solution, one end of the resistor R106 is connected to a capacitor C128, and the other end of the capacitor C128 is connected to an anode of a diode D30.
As a further limitation to the above technical solution, the asymmetric filter circuit includes a resistor R110, a resistor R115, a diode D31, a diode D32, and a capacitor C131, one end of the resistor R110 is connected to the output end of the operational amplifier U20B and one end of the resistor R115, the other end of the resistor R110 is connected to the anode of the diode D32, the cathode of the diode D32 is connected to one end of the capacitor C131, the other end of the capacitor C131 is grounded, the other end of the resistor R115 is connected to the cathode of the diode D31, and the anode of the diode D31 is connected to the cathode of the diode D32 and one end of the capacitor C131.
As a further limitation to the above technical solution, an input end of the schmitt trigger U201A is connected to one end of the capacitor C131, and an output end of the schmitt trigger U201A is connected to an input end of the control chip.
As a further limitation to the above technical solution, an input terminal of the schmitt trigger U201A is connected to a cathode of the zener diode D33, and an anode of the zener diode D33 is grounded.
The utility model discloses the anti-interference high accuracy alternating current signal periodic sampling circuit who obtains samples under the minimum condition of positive half cycle zero passage signal time influence, guarantees the accuracy of signal positive zero crossing. Meanwhile, hysteresis comparison and low-pass filtering are carried out on the negative zero crossing point, and the acquired periodic signal has the advantages of high anti-interference performance and high reliability.
Drawings
Fig. 1 is a circuit diagram of the anti-interference high-precision alternating current signal periodic sampling circuit of the utility model;
FIG. 2 is a waveform diagram of the same period of the AC signal and the output signal of the preceding Schmitt comparator circuit when there is no interference;
FIG. 3 is a waveform diagram of the same period of the AC signal and the output signal of the preceding Schmitt comparator circuit when there is high frequency interference;
FIG. 4 is a waveform diagram of an AC signal without interference according to the present invention;
FIG. 5 is a waveform diagram of an AC signal with high frequency interference according to the present invention;
FIG. 6 is a waveform diagram of the output signal when the asymmetric filter circuit of the present invention is not interfered;
FIG. 7 is a waveform diagram of the output signal of the asymmetric filter circuit of the present invention when there is high frequency interference;
fig. 8 is a waveform diagram of schmitt trigger U201A when the present invention is not interfering;
fig. 9 is a waveform diagram of schmitt trigger U201A when there is high frequency interference according to the present invention;
fig. 10 is a waveform diagram of the ac signal and the output signal of the schmitt trigger U201A in the same period when the present invention is not interfering;
fig. 11 is a waveform diagram of the ac signal and the output signal of the schmitt trigger U201A in the same period when the high frequency interference occurs according to the present invention.
Description of the drawings: 1-alternating current signal waveform, 2-preceding stage Schmitt comparison circuit output signal waveform, and 3-Schmitt trigger U201A output signal waveform.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
As shown in fig. 1, the anti-interference high-precision alternating current signal period sampling circuit is used for collecting the period of an alternating current signal, and comprises a preceding stage schmitt comparison circuit, an asymmetric filter circuit and a schmitt trigger U201A. The input end of the preceding-stage Schmitt comparison circuit is connected with an alternating current signal, the output end of the preceding-stage Schmitt comparison circuit is connected with the input end of the asymmetric filter circuit, the output end of the asymmetric filter circuit is connected with the input end of the Schmitt trigger U201A, and the Schmitt trigger U201A shapes the signal and outputs the signal to the control chip.
The pre-stage Schmitt comparison circuit comprises a resistor R109, a resistor R106, a diode D30 and an operational amplifier U20B, wherein the operational amplifier is short for operational amplifiers, one end of the resistor R109 is connected with an alternating current signal, namely one end of the resistor R109 is connected with the alternating current signal to be measured, the other end of the resistor R109 is respectively connected with the positive input end of the operational amplifier U20B and one end of the resistor R106, the other end of the resistor R106 is connected with the cathode of the diode D30, the anode of the diode D30 is connected with the output end of the operational amplifier U20B, and the negative input end of the operational amplifier U20B is grounded. One end of the resistor R106 is connected with the capacitor C128, the other end of the capacitor C128 is connected with the anode of the diode D30, and the operation of the operational amplifier is stabilized by adding the capacitor C128.
The asymmetric filter circuit comprises a resistor R110, a resistor R115, a diode D31, a diode D32 and a capacitor C131, wherein one end of the resistor R110 is connected with the output end of the operational amplifier U20B and one end of the resistor R115 respectively, the other end of the resistor R110 is connected with the anode of the diode D32, the cathode of the diode D32 is connected with one end of the capacitor C131, the other end of the capacitor C131 is grounded, the other end of the resistor R115 is connected with the cathode of the diode D31, and the anode of the diode D31 is connected with the cathode of the diode D32 and one end of the capacitor C131 respectively.
The input end of the Schmitt trigger U201A is connected with one end of the capacitor C131, and the output end of the Schmitt trigger U201A is connected with the input end of the control chip. The input terminal of the schmitt trigger U201A is connected to the cathode of the zener diode D33, the anode of the zener diode D33 is grounded, and the zener diode D33 is disposed between the capacitor C131 and the input terminal of the schmitt trigger U201A.
When the utility model is operated, when the alternating current signal is more than 0V, the preceding Schmidt comparison circuit outputs + VO 1; when the AC signal is less than
The preceding schmitt comparator outputs-VO 1. Diode D30 turns off when the ac signal is positive, and does not affect the positive zero crossing. When the alternating current signal is negative, the diode D30 is turned on, and the preceding schmitt comparator circuit generates a comparison hysteresis voltage through the resistor R109 and the resistor R106, thereby preventing the operational amplifier U20B from oscillating. Fig. 2 and 3 show waveforms of the ac signal and the output signal of the preceding schmitt comparator in the same period, where curve 1 is the waveform of the ac signal and curve 2 is the waveform of the output signal of the preceding schmitt comparator.
When the output voltage VO1 of the operational amplifier U20B is positive, the diode D31 is cut off, the diode D32 is conducted, the resistor R110 and the capacitor C131 form a forward RC filter, and high level is output; when the output voltage VO1 of the operational amplifier U20B is negative, the diode D31 is turned on, the diode D32 is turned off, the resistor R115 and the capacitor C131 form a negative RC filter, and a low level is output, and the negative RC filter is a large-time-constant low-pass filter. The positive zero-crossing voltage filter constant is adjusted through the resistor R110, the negative zero-crossing voltage filter constant is adjusted through the resistor R115, the operational amplifier U20B is used as a zero-crossing point comparator, the 6 pin of the operational amplifier is grounded and used as a reference zero voltage, the positive RC filter is provided with a short time constant, the asymmetric filter circuit immediately outputs a high level after the signal voltage exceeds the reference zero voltage, and the accuracy of signal zero crossing is guaranteed.
Because the positive zero-crossing point signal is only needed twice for measuring the period of the alternating current signal, the negative zero-crossing point signal is not needed, the negative zero-crossing point signal only plays the aim of resetting the output signal in one period, and the acquisition of the period of the signal is not influenced, the negative RC filter sets a long time constant, the effective time of the negative zero-crossing point signal is 3-5 times longer than that of the positive zero-crossing point signal, and when the zero-crossing time of the negative zero-crossing point signal exceeds the filtering time, the asymmetric filtering circuit outputs a low level to wait for the positive zero-crossing point signal of the next period. When the signal has oscillation near the zero point, the circuit effectively outputs a positive zero-crossing signal, and if negative interference exists, the interference pulse time is less than the negative filtering time, so that the output signal is not influenced, and the section pulse interference signal at the zero-crossing point can be effectively filtered. Fig. 6 and 7 show waveforms of the output signals of the asymmetric filter circuit when the ac signal is the ac signal shown in fig. 4 and 5. The ac signals in fig. 4 and 5, and fig. 2 and 3 are ac signals of different time periods.
The output signal VO2 after passing through the asymmetric filter circuit passes through a voltage regulator D33, and is processed by a schmitt trigger U201A as an input signal of the schmitt trigger U201A, and then a signal VO3 is output. The input voltage of the Schmitt trigger U201A is protected from exceeding the input voltage range of the Schmitt trigger U201 by connecting a voltage regulator tube D33 as a protection device. When an output signal VO2 of the asymmetric filter circuit is from a high level to a negative zero-crossing point voltage, the Schmitt trigger U201A outputs a high level, and because the negative RC filter sets a long time constant, when the zero-crossing time of the negative zero-crossing point signal VO2 of the output signal of the asymmetric filter circuit exceeds the filtering time, the Schmitt trigger U201A outputs a low level, so that signal interference is avoided; when the asymmetric filter circuit output signal VO2 exceeds the forward zero crossing voltage, schmitt trigger U201A immediately outputs a high level due to the short time constant set by the forward RC filter. When the alternating current signal is as shown in fig. 4 and 5, the waveform of the output signal of the schmitt trigger U201A is as shown in fig. 8 and 9.
After the output signal VO3 of the schmitt trigger U201A enters the control chip, the control chip accurately measures the period of the ac signal by calculating the time between two rising edges because the positive zero crossing signal corresponds to the rising edge of the low level of the output signal of the schmitt trigger U201A. Fig. 10 and 11 show waveforms of the ac signal and the output signal of the schmitt trigger U201A in the same period, where the ac signal in fig. 10 and 11 is a waveform of a different time period from the ac signal in fig. 2 and 3, and the ac signal in fig. 4 and 5, the curve 1 in fig. 10 and 11 is an ac signal waveform, and 3 is an output signal waveform of the schmitt trigger U201A.
Fig. 2-11 are mainly used to show a complete cycle waveform of the input/output signals of each circuit, so that the initial positions of the graphs are not consistent when comparing a cycle waveform in the middle of the graphs.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be covered by the present invention within the technical scope of the present invention, and the technical solution obtained by replacing or changing the technical idea of the present invention with equivalents.
Claims (6)
1. The utility model provides an anti-interference high accuracy alternating current signal periodic sampling circuit for gather alternating current signal's cycle, its characterized in that: the input end of the preceding-stage Schmitt comparison circuit is connected with an alternating current signal, the output end of the preceding-stage Schmitt comparison circuit is connected with the input end of the asymmetric filter circuit, the output end of the asymmetric filter circuit is connected with the input end of the Schmitt trigger U201A, and the output end of the Schmitt trigger U201A is connected with the input end of a control chip.
2. The anti-jamming high-precision alternating current signal periodic sampling circuit according to claim 1, wherein: the pre-stage Schmitt comparison circuit comprises a resistor R109, a resistor R106, a diode D30 and an operational amplifier U20B, wherein one end of the resistor R109 is connected with an alternating current signal, the other end of the resistor R109 is respectively connected with a positive input end of the operational amplifier U20B and one end of the resistor R106, the other end of the resistor R106 is connected with a cathode of a diode D30, an anode of a diode D30 is connected with an output end of the operational amplifier U20B, and a negative input end of the operational amplifier U20B is grounded.
3. The anti-jamming high-precision alternating current signal periodic sampling circuit according to claim 2, wherein: one end of the resistor R106 is connected with a capacitor C128, and the other end of the capacitor C128 is connected with the anode of the diode D30.
4. The anti-jamming high-precision alternating current signal periodic sampling circuit according to claim 1, wherein: the asymmetric filter circuit comprises a resistor R110, a resistor R115, a diode D31, a diode D32 and a capacitor C131, wherein one end of the resistor R110 is connected with the output end of the operational amplifier U20B and one end of the resistor R115 respectively, the other end of the resistor R110 is connected with the anode of the diode D32, the cathode of the diode D32 is connected with one end of the capacitor C131, the other end of the capacitor C131 is grounded, the other end of the resistor R115 is connected with the cathode of the diode D31, and the anode of the diode D31 is connected with the cathode of the diode D32 and one end of the capacitor C131 respectively.
5. The anti-jamming high-precision alternating current signal periodic sampling circuit according to claim 1, wherein: the input end of the Schmitt trigger U201A is connected with one end of the capacitor C131, and the output end of the Schmitt trigger U201A is connected with the input end of the control chip.
6. The anti-jamming high-precision alternating current signal periodic sampling circuit according to claim 5, wherein: the input end of the Schmitt trigger U201A is connected with the cathode of a voltage stabilizing diode D33, and the anode of the voltage stabilizing diode D33 is grounded.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202123173283.4U CN216851941U (en) | 2021-12-16 | 2021-12-16 | Anti-interference high-precision alternating current signal periodic sampling circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202123173283.4U CN216851941U (en) | 2021-12-16 | 2021-12-16 | Anti-interference high-precision alternating current signal periodic sampling circuit |
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| Publication Number | Publication Date |
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| CN216851941U true CN216851941U (en) | 2022-06-28 |
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| CN202123173283.4U Active CN216851941U (en) | 2021-12-16 | 2021-12-16 | Anti-interference high-precision alternating current signal periodic sampling circuit |
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2021
- 2021-12-16 CN CN202123173283.4U patent/CN216851941U/en active Active
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