JPH0414886B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a zero-cross signal output device, particularly a zero-cross signal output device that outputs a zero-cross signal in response to a zero potential of an AC input. Two sets of series circuits are provided in which a photo coupler is connected in series to a Zener diode, and each photo coupler in the two series circuits is connected in series.
A zero-cross signal output device configured to output the zero-cross signal based on the output from the coupler, and capable of outputting an accurate zero-cross signal without being affected by noise contained in the AC input. It is related to.

(Prior art and problems to be solved by the present invention) Conventionally, as a zero-cross signal output device that outputs a zero-cross signal in response to zero potential of AC input,
As shown in FIG. 3, a device using a photo coupler is known.

In the conventional example shown in FIG. 3, an AC input is full-wave rectified by a rectifier 1, and the DC output voltage of the rectifier 1 is applied to a photocoupler 16 via a resistor 14. Therefore, the photo
The coupler 16 will be controlled by the DC output voltage of the rectifier 1. And the photo above
The reference voltage Ve is applied to the collector of the light receiving element 16' in the coupler 16 via the resistor 15, and the emitter is connected to the ground. A pulse signal, that is, a zero-cross signal is output.

The conventional example shown in FIG. 3 described above can output an accurate zero-cross signal when the AC input does not contain noise, but when the AC input contains noise, In particular, there is an undesirable problem in that noise in the vicinity of zero potential of the AC input causes cracks in the zero-crossing signal, making it impossible to obtain an accurate zero-crossing signal.

(Means for Solving the Problems) The present invention solves the above problems and makes it possible to obtain accurate zero-crossing signals even from AC inputs containing noise. The output device is a zero-cross signal output device that outputs a zero-cross signal in response to a zero potential of an AC input, and includes a rectifier that rectifies the AC input, and a first zener that is controlled by a DC output voltage from the rectifier. Diode and first photo
a series circuit with a second zener diode having a lower zener voltage than the first zener diode and a second photocoupler; an output from the second photocoupler; is configured to strobe with the output from the first photo coupler to extract the output timing from the second photo coupler, and the zero cross signal is output based on the output timing. It is characterized by the fact that
This will be explained below with reference to the drawings.

(Embodiment of the invention) FIG. 1 shows a circuit configuration in an embodiment of the invention,
FIG. 2 shows a voltage waveform diagram corresponding to the arrow shown in FIG. 1. In FIG. 1, 1 is a rectifier, 2 and 3 are Zener diodes, 4 and 5 are photocouplers, 6 and 7 are amplifiers, 8 is a D-type flip-flop, and 9 to 12 are resistors. .

In FIG. 1, a rectifier 1 converts an alternating current input (as shown in FIG. 2) into a direct current as shown in FIG. The DC output voltage of the rectifier 1 is then supplied to the first photo coupler 4 via the resistor 9 and the first Zener diode 2, and is also supplied to the first photo coupler 4 via the resistor 10 and the second Zener diode 3. 2 photo coupler 5.

In the embodiment shown in FIG. 1, the Zener voltage V _z1 of the first Zener diode 2 is set larger than the Zener diode V _z2 of the second Zener diode 3. Further, the emitters of the light receiving elements 4' and 5' in the first photo coupler 4 and the second photo coupler 5 are respectively connected to ground, and the respective collectors are connected to a resistor 11.
A reference voltage Ve is applied through 12 and 12. The collector of the light receiving element 4' in the first photo coupler 4 is connected to the D terminal and the clear (CLR) terminal of the D flip-flop 8 via the amplifier 6, and The collector of the light receiving element 5' in 5 is connected to the clock (CK) terminal of the D-type flip-flop 8 through an amplifier 7. The operation of the embodiment shown in FIG. 1 will be explained below with reference to the voltage waveform diagram shown in FIG. 2.

As mentioned above, the AC input shown in FIG. 2 is rectified by the rectifier 1 and converted into the DC voltage shown in FIG. The DC voltage is then supplied to the first photo coupler 4 via the resistor 9 and the first Zener diode 2, and is also supplied to the second photo coupler via the resistor 10 and the second Zener diode 3. It is supplied to coupler 5. The light receiving element 4' in the first photo coupler 4 is
When the DC voltage becomes equal to or less than the Zener voltage V _z1 of the first Zener diode 2 (for example, in the range of time t ₁ to t ₄ shown in the second figure), it becomes an OFF state, and in the range of the Zener voltage V _z1 or more. is in the on state. Therefore, the above D
The signals applied to the D and CLR terminals of the flip-flop 8 are the pulse signals shown in FIG. Similarly, the second photo coupler 5
The light-receiving element 5' in
When the Zener voltage V _z2 of the Zener diode 3 becomes lower than V z2 (for example, in the range of time t ₂ to t ₃ shown in FIG. 2), the D-type flip-flop 8 is turned off via the amplifier 7. The signal applied to the CK terminal becomes the pulse signal shown in FIG. Therefore, the Q of the D-type flip-flop 8 is
From the terminal, as shown by the pulse signal shown in FIG. 2, from the rising edge of the pulse signal (e.g., time t 2 shown in FIG. ₂ ) to the falling edge of the pulse signal (e.g., time t 2 shown in FIG. 2), A pulse signal that is at a high level until t ₄ ) is output. That is, the pulse signal output from the Q terminal of the D-type flip-flop 8 is a signal that outputs a high level in response to the zero potential of the AC input (for example, time t ₀ shown in FIG. 2). This is a zero-cross signal according to the present invention. Therefore, the pulse signal output from the Q terminal of the D-type flip-flop 8 will not erroneously detect a zero cross due to noise contained near the zero potential of the AC input. , which can be used as an accurate zero-crossing signal.

(Effects of the Invention) As explained above, according to the present invention, it is possible to eliminate erroneous detection of zero cross points due to noise contained in AC input, so it is possible to obtain accurate zero cross signals. It is possible to provide a zero-cross signal output device that provides a zero-cross signal output device.

[Brief explanation of drawings]

FIG. 1 shows a circuit configuration in an embodiment of the present invention.
FIG. 2 is a voltage waveform diagram corresponding to the arrow shown in FIG. 1, and FIG. 3 shows a conventional configuration of a zero-cross signal output device. In the figure, 1 is a rectifier, 2 and 3 are Zener diodes, 4 and 5 are photocouplers, 6 and 7 are amplifiers, 8 is a D-type flip-flop, and 9 to 12 are resistors.

Claims (1)

[Claims] 1. A zero-cross signal output device that outputs a zero-cross signal in response to a zero potential of an AC input, comprising a rectifier that rectifies the AC input, a first Zener diode controlled by the DC output voltage from the rectifier, and a first Zener diode that is controlled by the DC output voltage from the rectifier. Series circuit with photo coupler 1,
a series circuit of a second zener diode having a lower zener voltage than the first zener diode and a second photo coupler;
strobe the output from the photo coupler with the output from the first photo coupler,
A zero-cross signal output device characterized in that the device is configured to extract an output timing from the second photo coupler, and output the zero-cross signal based on the output timing.