JP4419882B2 - Zero cross detection circuit - Google Patents

Description

  The present invention relates to a zero cross detection circuit that generates a pulse signal synchronized with a timing at which an AC voltage crosses a zero potential. Zero cross detection circuits are widely used in products that use power phase, such as power measurement related products.

  Prior art documents related to the zero-cross detection circuit include the following.

JP-A-2-223218

  FIG. 6 is a functional block diagram showing the basic configuration of the zero-cross detection circuit. Reference numeral 1 denotes a commercial power source. Reference numeral 2 denotes DC insulation / rectification means, which receives the voltage E of the commercial power source 1 and outputs a signal F that has undergone full-wave rectification after DC insulation. Reference numeral 3 denotes a comparator having a threshold value L, which generates a pulse signal Po during a period when the signal F is equal to or lower than the threshold value, and uses this as a zero-cross detection signal.

  FIG. 7 is a circuit configuration diagram of the zero-cross detection circuit disclosed in Patent Document 1. In FIG. The AC voltage E of the commercial power source 1 is subjected to DC insulation and equivalent full-wave rectification via the photocoupler means 21 and 22 every half cycle. The monostable multivibrator 4 is triggered by one half cycle signal F1 obtained from the photocoupler means 21.

  A signal obtained by adding an output pulse P1 of the monostable multivibrator 4 and a signal P2 obtained by directly amplifying the other half-cycle signal F2 obtained from the photocoupler means 22 by an OR circuit composed of diodes 51 and 52 is a zero-cross detection signal. Let it be Po.

  FIG. 8 is a signal waveform diagram of each part of the functional block diagram shown in FIG. 8A shows the waveform of the AC voltage E, FIG. 8B shows the waveform of the signal F obtained by full-wave rectification of the AC voltage E, and FIG. 8C shows the waveform of the pulse signal Po that is turned on during the period in which the signal F is below the threshold value L. It is.

  When the waveform of the AC voltage E is a clean sine wave as shown in FIG. 8A, one stable pulse signal Po can be obtained at the zero cross timing as shown in FIG. When the AC voltage E is disturbed by this, or when waveform distortion is applied, there is a problem that stable zero cross detection cannot be performed.

  FIG. 9 is a waveform diagram when the AC voltage E is disturbed by the superimposed noise. As shown in FIG. 9A, when the AC voltage E reciprocates the threshold value L a plurality of times in the vicinity of the zero cross, the pulse signal Po continues two or more times as shown in FIG. 9B. appear. For this reason, a zero-cross waveform with a fixed period cannot be obtained.

  FIG. 10 is a waveform diagram when the AC voltage E is subjected to waveform distortion and becomes a rectangular wave. At timings t1 and t2 in FIG. 10A, the change in the AC voltage E near the zero cross is steep, and the pulse signal Po shown in FIG. 10B becomes a steep pulse signal in order to cross the threshold value L in a short time. A sufficient pulse width cannot be obtained. In the worst case, the pulse signal Po is lost as at the timing t3, and similarly, a zero-cross waveform with a fixed period cannot be obtained.

  In the configuration in which the monostable multivibrator 4 is triggered in response to the half cycle of the AC voltage shown in FIG. However, the problem is not solved in the other half cycle.

  Furthermore, the monostable multivibrator 4 is directly triggered by the signal F1 obtained by amplifying the output of the photocoupler means 21. When the AC signal E is disturbed by noise, the trigger is not stably applied, and the signal P1 may be lost, and a zero-cross waveform with a constant period cannot be stably obtained as a whole.

  Therefore, the problem to be solved by the present invention is to realize a zero-cross detection circuit capable of detecting a zero-cross at a constant period and stably with respect to superimposed noise and waveform distortion with respect to an AC voltage of a commercial power supply.

In order to achieve such an object, the configuration of the present invention is as follows.
(1) In a zero cross detection circuit that generates a pulse signal synchronized with the timing at which the AC voltage crosses the zero potential,
First rectangular wave conversion means having a filter circuit for generating a rectangular wave signal synchronized with the positive half cycle of the AC voltage, and a filter circuit for generating a rectangular wave signal synchronized with the negative half cycle of the AC voltage Second rectangular wave conversion means having
First retriggerable monostable multivibrator means triggered by a square wave signal synchronized with the positive half cycle, and second retriggerable monostable multi triggered by a square wave signal synchronized with the negative half cycle Vibrator means;
A logic circuit for calculating a logical sum of an output pulse signal of the first retriggerable monostable multivibrator means and an output pulse signal of the second retriggerable monostable multivibrator means;
A zero-cross detection circuit comprising:

( 2 ) The zero-cross detection circuit according to (1), further comprising a DC insulation means for DC-insulating the circuit for supplying the AC voltage from other circuit elements.

As is apparent from the above description, the present invention has the following effects.
(1) It is possible to reliably trigger the monostable multivibrator unit by introducing a rectangular wave conversion unit that generates a rectangular wave signal synchronized with at least one of the positive half cycle and the negative half cycle of the AC voltage. it can. Thereby, even when the power supply waveform is disturbed due to noise as shown in FIG. 9, it is possible to stably obtain a zero-cross signal having a fixed period whose waveform is shaped by the monostable multivibrator means.

(2) Even when the waveform of the AC voltage E is distorted as shown in FIG. 10 and becomes a rectangular wave, by introducing the rectangular wave converting means in both the positive half cycle and the negative half cycle, the AC voltage is changed. It becomes possible to obtain positive-negative and negative-positive positive zero crossing of the voltage as a rectangular wave signal. Therefore, it is possible to stably obtain a zero-cross signal having a fixed period obtained by shaping the waveform by the monostable multivibrator means.

(3) By using a retriggerable monostable multivibrator as the monostable multivibrator means, it becomes possible to always generate one zero-cross detection signal every half cycle of the AC voltage even if the waveform is unstable. A zero-cross signal having a fixed period can be obtained stably.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a functional block diagram showing an embodiment of a zero cross detection circuit to which the present invention is applied. The same elements as those described in FIG. 6 and FIG. Hereinafter, the characteristic part of the present invention will be described.

  In FIG. 1, reference numerals 101 and 102 denote first and second DC insulation / rectification means corresponding to positive and negative half cycles of the AC voltage E, and output signals F1 and F2, respectively. Reference numerals 201 and 202 denote first and second rectangular wave conversion means for inputting the signals F1 and F2, and output rectangular wave signals G1 and G2 synchronized with the signals F1 and F2.

  Reference numerals 301 and 302 denote first and second monostable multivibrator means triggered by rectangular wave signals G1 and G2, respectively, and pulses having a predetermined pulse width synchronized with the falling edges (or rising edges) of G1 and G2. Signals P1 and P2 are output.

  Reference numeral 400 denotes a logic circuit that calculates a logical sum of the pulse signals P1 and P2, and finally outputs a zero-cross detection signal Po.

  FIG. 2 is a circuit configuration diagram showing a specific configuration of the functional block shown in FIG. The first and second DC insulation / rectification means 101 and 102 have the same function as the photocoupler means 21 and 22 shown in FIG. 7, perform DC insulation and equivalent full-wave rectification, and each AC voltage E The signals F1 and F2 synchronized with the half cycle are output.

  The first rectangular wave converting means 201 is composed of a filter circuit including an inverter A1 that receives the signal F1 and a resistor R1 and a capacitor C1 connected to the output side thereof, and outputs a rectangular wave signal G1.

  Similarly, the second rectangular wave conversion means 202 includes a filter circuit including an inverter A2 that receives the signal F2 and a resistor R2 and a capacitor C2 connected to the output side of the inverter A2, and outputs a rectangular wave signal G2.

  The first monostable multivibrator unit 301 is triggered by the falling edge of the rectangular wave signal G1 and outputs a pulse signal P1 having a pulse width determined by a time constant set by the resistor R3 and the capacitor C3.

  Similarly, the second monostable multivibrator means 302 outputs a pulse signal P2 that is triggered at the falling edge of the rectangular wave signal G2 and has a pulse width determined by a time constant set by the resistor R4 and the capacitor C4.

  These pulse signals P1 and P2 are input to the logic circuit 400, and are subjected to a logical sum operation to output a final zero cross detection signal Po.

  FIG. 3 is a signal waveform diagram of each part when the AC voltage is not affected by noise or distortion. 3A is a waveform diagram of the AC voltage E. FIG. (B) is a waveform diagram of the rectified wave F1 corresponding to the positive half cycle output from the photocoupler means 201, (C) is a waveform diagram of the rectangular wave signal G1 synchronized with the signal F1, and (D) is a rectangular wave. It is a wave form diagram of pulse signal P1 of the 1st monostable multivibrator means 301 triggered by the fall of signal G1.

  3E is a waveform diagram of the rectified wave F2 corresponding to the negative half cycle output from the photocoupler means 202, FIG. 3F is a waveform diagram of the rectangular wave signal G2 synchronized with the signal F2, and FIG. It is a wave form chart of pulse signal P2 of the 2nd monostable multivibrator means 302 triggered by falling of rectangular wave signal G2.

  FIG. 3 (H) is a waveform diagram of the final zero-cross detection signal Po. The pulse signal P1 of the first monostable multivibrator means 301 shown in (D) and the second monostable multivibrator shown in (G). It is a logical sum of the pulse signal P2 of the means 302.

  According to the present invention, the first monostable multivibrator unit 301 and the second monostable multivibrator unit 302 are provided at the falling edge of the rectangular wave signal of the first rectangular wave converting unit 201 and the second rectangular wave converting unit 202 in the previous stage. The zero-cross signal Po can be reliably generated every half cycle of the AC voltage E.

  FIG. 4 is a waveform diagram when the AC voltage E is disturbed by the superimposed noise, as described with reference to FIG. As shown in FIG. 4A, when the AC voltage E reciprocates the zero potential multiple times near the zero cross, the rectangular wave signal G1 corresponding to the positive half cycle as shown in FIG. It turns on and off multiple times.

  The first monostable multivibrator means 301 triggered by the rectangular wave signal is turned on in synchronization with the first falling edge of the rectangular wave signal G1, as shown in (C), and is set by the resistor R3 and the capacitor C3. A pulse signal P1 having a pulse width (Ams) determined by the time constant is output.

  At this time, when a retriggerable monostable multivibrator is used as the monostable multivibrator, the signal P1 has a pulse width of Ams from the last falling timing of the on / off change.

  FIG. 4 (D) shows a rectangular wave signal G2 corresponding to a negative half cycle. Similar to FIG. 4 (B), the AC voltage E reciprocates the zero potential multiple times near the zero cross. Change on and off several times.

  The second monostable multivibrator means 302 triggered by the rectangular wave signal is turned on in synchronization with the first falling of the rectangular wave signal G2, as shown in (E), and is set by the resistor R4 and the capacitor C4. A pulse signal P2 having a pulse width (Ams) determined by the time constant is output.

  At this time, when a retriggerable monostable multivibrator is used as the monostable multivibrator, the signal P2 has a pulse width of Ams from the last falling timing of the on / off change.

  As described above, when the retriggerable monostable multivibrator is used as the monostable multivibrator, the pulse widths of the pulse signals P1 and P2 change due to the ON / OFF fluctuations of the pulse signals G1 and G2. There is a merit that zero cross detection can be surely performed in a half cycle.

  FIG. 5 is a waveform diagram in the case where the AC voltage E is subjected to waveform distortion and becomes a rectangular wave, as described with reference to FIG. FIG. 5A is a waveform diagram of the AC voltage E, and the change in the AC voltage E near the zero cross is steep at timings t1 to t5.

  Even if the change in the AC voltage E near the zero cross is steep, according to the present invention, as shown in FIGS. 5B and 5D, the rectangular wave converting means 201 and 202 operate reliably, and the rectangular wave signal Since G1 and G2 are reliably obtained, stable pulse signals P1 and P2 having a pulse width Ams can be obtained from the monostable multivibrators 301 and 302 as shown in (C) and (E).

  The present invention can be applied to products that require a power supply phase, such as power measurement related equipment. Specifically, the present invention can be applied to a circuit for determining a sign of power or the like based on a phase difference such as a voltage current.

It is a functional block diagram showing one embodiment of a zero cross detection circuit to which the present invention is applied. FIG. 2 is a circuit configuration diagram illustrating a specific configuration of each functional block illustrated in FIG. 1. In the structure of this invention, it is a signal waveform diagram of each part in case an alternating voltage is not influenced by noise or distortion. In the structure of this invention, it is a wave form diagram when disordered by the noise which an alternating voltage superimposes. In the structure of this invention, it is a wave form diagram when an alternating voltage receives waveform distortion and becomes a rectangular wave. It is a functional block diagram which shows the basic composition of a zero cross detection circuit. 2 is a circuit configuration diagram of a zero-cross detection circuit disclosed in Patent Document 1. FIG. It is a signal waveform diagram of each part of the functional block diagram shown in FIG. It is a wave form diagram when disordered by the noise which an alternating voltage superimposes. It is a wave form diagram when an alternating voltage receives waveform distortion and becomes like a rectangular wave.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Commercial power supply 101 1st DC insulation and rectification means 102 2nd DC insulation and rectification means 201 1st rectangular wave conversion means 202 2nd rectangular wave conversion means 301 1st monostable multivibrator 302 2nd monostable multivibrator 400 Logic circuit

Claims (2)

In the zero cross detection circuit that generates a pulse signal synchronized with the timing at which the AC voltage crosses the zero potential,
First rectangular wave conversion means having a filter circuit for generating a rectangular wave signal synchronized with the positive half cycle of the AC voltage, and a filter circuit for generating a rectangular wave signal synchronized with the negative half cycle of the AC voltage Second rectangular wave conversion means having
First retriggerable monostable multivibrator means triggered by a square wave signal synchronized with the positive half cycle, and second retriggerable monostable multi triggered by a square wave signal synchronized with the negative half cycle Vibrator means;
A logic circuit for calculating a logical sum of an output pulse signal of the first retriggerable monostable multivibrator means and an output pulse signal of the second retriggerable monostable multivibrator means;
A zero-cross detection circuit comprising: 2. The zero-cross detection circuit according to claim 1, further comprising direct current insulation means for direct current insulation of the circuit supplying the alternating current voltage from other circuit elements.

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