CN105092948A - High-precision alternating-current signal zero crossing detection device and method - Google Patents

Abstract

The invention discloses a high-precision AC signal zero-crossing detection device, which includes an optocoupler U1, an optocoupler U2 and a programmable logic device. The cathode of the device U2 is electrically connected, and the N terminal is electrically connected to the cathode of the optocoupler U1 and the anode of the optocoupler U2 respectively; the collector of the optocoupler U1 and the collector of the optocoupler U2 are respectively connected to the I of the programmable logic device The /O input port is connected, and is electrically connected to the power supply VCC respectively at the same time; the emitter of the optocoupler device U1 and the emitter of the optocoupler device U2 are respectively grounded; the invention also discloses a high-precision AC signal zero-crossing detection method, which can be programmed The logic device processes the level signals output by the optocoupler U1 and the optocoupler U2, and finally outputs a narrow pulse signal corresponding to the zero-crossing point of the AC signal. The invention has the advantages of simple structure, stable and reliable, convenient use and strong anti-interference ability.

Description

High-precision AC signal zero-crossing detection device and method

technical field

The invention relates to a high-precision AC signal zero-crossing detection device and a high-precision AC signal zero-crossing detection method, belonging to the technical field of signal detection.

Background technique

There are various kinds of zero-crossing detection circuits of existing AC signals, among which the circuits using optocoupler devices for zero-crossing detection are widely used.

The existing optocoupler device detection device is composed of two optocouplers, and its detection method is to realize the zero-crossing detection by utilizing the characteristic that the photocoupler cuts off when the AC signal is close to the zero-crossing point. Since the cut-off of the optocoupler does not strictly correspond to the zero-crossing point of the AC signal, there are problems such as dead zone, inaccurate zero-crossing, and large error.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, provide a high-precision AC signal zero-crossing detection device, and solve the technical problems in the prior art that the zero-crossing detection of optocoupler devices has dead zones, inaccurate zero-crossing, and large errors .

In order to solve the above technical problems, the technical solution adopted in the present invention is: a high-precision AC signal zero-crossing detection device, including an optocoupler U1, an optocoupler U2 and a programmable logic device, and the optocoupler U1, optocoupler U2 respectively includes: respective light-emitting diodes and phototransistors corresponding to the light-emitting diodes;

The L terminal of the AC signal to be detected is electrically connected to the anode of the optocoupler U1 and the cathode of the optocoupler U2 respectively, and the N terminal is electrically connected to the cathode of the optocoupler U1 and the anode of the optocoupler U2 respectively;

The collector of the optocoupler U1 and the collector of the optocoupler U2 are respectively connected to the I/O input ports of the programmable logic device, and are electrically connected to the output terminals of the power supply VCC respectively; the emitters of the optocoupler U1, The emitters of the optocoupler U2 are grounded respectively;

The I/O output port of the programmable logic device is connected with the digital quantity input port of the main circuit;

When the waveform of the L-N terminal of the AC signal outputs a positive half cycle, the light-emitting diode of the optocoupler U1 is turned on and emits light, and the phototransistor of the optocoupler U1 is turned on and outputs a low level; at the same time, the light-emitting diode of the optocoupler U2 is cut off, and the light The phototransistor of the coupling device U2 is cut off and outputs a high level;

When the waveform of the L-N terminal of the AC signal outputs a positive half cycle, the light-emitting diode of the optocoupler U2 turns on and emits light, and the phototransistor of the optocoupler U2 turns on and outputs a low level; at the same time, the light-emitting diode of the optocoupler U1 is cut off, and the light The phototransistor of the coupling device U1 is cut off and outputs a high level;

The programmable logic device detects the zero-crossing point according to the level signals output by the optocoupler U1 and the optocoupler U2.

As a further improvement of the present invention, the L terminal of the AC signal is connected in series with the current-limiting resistor R1 and the current-limiting resistor R2 in sequence, and then electrically connected to the anode of the optocoupler U1 and the cathode of the optocoupler U2 respectively.

As a further improvement of the present invention, the collector of the optocoupler U1 and the collector of the optocoupler U2 are electrically connected to the output end of the power supply VCC through respective pull-up resistors.

Another object of the present invention is to provide a high-precision AC signal zero-crossing detection method, comprising the following steps:

Step 1: The programmable logic device collects the level signals output by the optocoupler U1 and the optocoupler U2, and inverts the collected level signals, which are recorded as: S1 and S2 respectively;

Step 2: The programmable logic device performs an NOR logic operation on the signals S1 and S2 to obtain a square wave signal S3;

Step 3: the programmable logic device measures the pulse width of the square wave signal S3;

Step 4: The programmable logic device outputs a narrow pulse S4 through the I/O output port when the width of the square wave signal S3 is half, and S4 corresponds to the zero-crossing point of the AC signals L and N.

Compared with the prior art, the beneficial effects achieved by the present invention are: simple structure, stable and reliable, easy to use, and strong anti-interference ability.

Description of drawings

Fig. 1 is a circuit diagram of a high-precision AC signal zero-crossing detection device provided by the present invention.

Fig. 2 is a flow chart of the high-precision AC signal zero-crossing detection method provided by the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings. The following examples are only used to illustrate the technical solution of the present invention more clearly, but not to limit the protection scope of the present invention.

As shown in Figure 1, the high-precision AC signal zero-crossing detection device includes an optocoupler device U1, an optocoupler device U2, and a programmable logic device CPLD. The optocoupler device U1 and the optocoupler device U2 include: respective light-emitting diodes and The light-emitting diode corresponds to the phototransistor provided. The I/O output port of the programmable logic device CPLD is connected with the digital quantity input port of the main circuit.

The L terminal of the AC signal to be detected is connected in series with the current limiting resistor R1 and the current limiting resistor R2 in sequence, and then electrically connected to the anode of the optocoupler device U1 and the cathode of the optocoupler device U2 respectively, and the N terminal is respectively connected to the cathode of the optocoupler device U1 , The anode of the optocoupler device U2 is electrically connected. The collector of the optocoupler U1 and the collector of the optocoupler U2 are respectively connected to the I/O input port of the programmable logic device CPLD, and are electrically connected to the output terminal of the power supply VCC through respective pull-up resistors. The emitter of the optocoupler device U1 and the emitter of the optocoupler device U2 are grounded respectively.

When the waveform of the L-N terminal of the AC signal outputs a positive half cycle, the light-emitting diode of the optocoupler U1 is turned on and emits light, and the phototransistor of the optocoupler U1 is turned on and outputs a low level; at the same time, the light-emitting diode of the optocoupler U2 is cut off, and the light The phototransistor of the coupling device U2 is cut off and outputs a high level.

When the waveform of the L-N terminal of the AC signal outputs a positive half cycle, the light-emitting diode of the optocoupler U2 turns on and emits light, and the phototransistor of the optocoupler U2 turns on and outputs a low level; at the same time, the light-emitting diode of the optocoupler U1 is cut off, and the light The phototransistor of the coupling device U1 is cut off and outputs a high level.

The programmable logic device CPLD detects the zero-crossing point according to the level signals output by the optocoupler device U1 and the optocoupler device U2.

A high-precision AC signal zero-crossing detection method provided by the present invention is realized based on the above-mentioned zero-crossing detection device, and includes the following steps:

Step 1: The programmable logic device CPLD collects the level signals output by the optocoupler device U1 and the optocoupler device U2, and inverts the collected level signals, which are respectively recorded as: S1 and S2;

Step 2: The programmable logic device CPLD performs an NOR logic operation on the signals S1 and S2 to obtain a square wave signal S3;

Step 3: the programmable logic device CPLD measures the pulse width of the square wave signal S3;

Step 4: The programmable logic device CPLD outputs a narrow pulse S4 through the I/O output port when the width of the square wave signal S3 is half, and S4 corresponds to the zero-crossing point of the AC signals L and N.

The high-precision AC signal zero-crossing detection method provided by the invention has strong anti-interference ability.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and modifications can also be made. It should also be regarded as the protection scope of the present invention.

Claims (4)

1. high-precision AC signal zero crossing detection device, it is characterized in that, comprise optocoupler U1, optocoupler U2 and programmable logic device (PLD), described optocoupler U1, optocoupler U2 comprise respectively: respective light emitting diode and the phototriode that arrange corresponding to light emitting diode;

The L end of AC signal to be detected is connected with the anode of optocoupler U1, the cathodic electricity of optocoupler U2 respectively, and N end is electrically connected with the negative electrode of optocoupler U1, the anode of optocoupler U2 respectively;

The collector of described optocoupler U1, the collector of optocoupler U2 are connected with the I/O input port of programmable logic device (PLD) respectively, are electrically connected respectively with the output terminal of power supply VCC simultaneously; The emitter of optocoupler U1, the emitter of optocoupler U2 ground connection respectively;

The I/O delivery outlet of described programmable logic device (PLD) is connected with main circuit digital quantity input port;

When the L-N of AC signal holds the positive half cycle of wave form output, the LEDs ON of optocoupler U1 is also luminous, the phototriode conducting of optocoupler U1, output low level; The light emitting diode cut-off of optocoupler U2 simultaneously, the phototriode cut-off of optocoupler U2, exports high level;

When the L-N of AC signal holds the positive half cycle of wave form output, the LEDs ON of optocoupler U2 is also luminous, the phototriode conducting of optocoupler U2, output low level; The light emitting diode cut-off of optocoupler U1 simultaneously, the phototriode cut-off of optocoupler U1, exports high level;

The level signal that described programmable logic device (PLD) exports according to optocoupler U1, optocoupler U2 is detected zero point.

2. high-precision AC signal zero crossing detection device according to claim 1, is characterized in that, the L of described AC signal holds successively after series limiting resistor R1, current-limiting resistance R2, then is connected with the anode of optocoupler U1, the cathodic electricity of optocoupler U2 respectively.

3. high-precision AC signal zero crossing detection device according to claim 1, is characterized in that, the collector of described optocoupler U1, the collector of optocoupler U2 are electrically connected respectively by the output terminal of respective pull-up resistor with power supply VCC.

4. high-precision AC signal zero passage detection method, is characterized in that, comprise the steps:

Step one: programmable logic device (PLD) gathers the level signal that optocoupler U1, optocoupler U2 export, and to the level signal negate gathered, be designated as respectively: S1, S2;

Step 2: programmable logic device (PLD) carries out NOR-logic computing to signal S1 and S2, obtains square-wave signal S3;

Step 3: programmable logic device (PLD) measures the pulse width of square-wave signal S3;

Step 4: programmable logic device (PLD), at a half of square-wave signal S3 width, exports the zero crossing of burst pulse S4, S4 and corresponding AC signal L, N by I/O delivery outlet.