JPH02146923A - Instantaneous interruption detecting circuit for ac power source - Google Patents

Abstract

PURPOSE:To isolate AC circuit from DC circuit by providing an AC photo- coupler for subjecting an AC input to half-wave rectification, a shaper gate for subjecting the output signal from the AC input photo-coupler to shaping and producing pulses and a counter for counting the number of pulses fed from the shaper gate. CONSTITUTION:A ternary counter 6 is driven by a clock signal 4 having frequency five times that of an AC input. When the AC input is normal, the ternary counter 6 is reset periodically based on an output pulse fed from a shaper gate 5 to maintain the output signal 7 from the ternary counter 6 at Low level, but when the AC input is missed for longer than one half period, pulse signal for resetting the ternary counter 6 is also missed and the ternary counter 6 counts out to bring the counter output signal 7 to high level thus enabling detection of missing of AC input. By such arrangement, AC circuit can be isolated from DC circuit with a few components.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an AC power supply instantaneous interruption detection circuit.

[Conventional technology]

BACKGROUND ART Conventionally, AC power supply instantaneous interruption detection circuits have been used in various electronic devices, and as this type of AC power supply instantaneous interruption detection circuits, a full-wave rectifier circuit using a diode has been used.

[Problem to be solved by the invention]

The conventional AC power supply instantaneous interruption detection circuit described above uses full-wave rectification using diodes, so insulation between the AC circuit and DC circuit cannot be maintained, and the DC circuit may malfunction due to impulse noise mixed in the AC power supply. There is a problem with this occurring.

Furthermore, when a DC input photocoupler is used for insulation, a full-wave rectifier circuit and a photocoupler are required, resulting in an increase in the number of parts.

An object of the present invention is to provide an AC power supply instantaneous interruption detection circuit that is configured with a small number of parts and maintains insulation between an AC circuit and a DC circuit.

[Means to solve the problem]

The AC power supply instantaneous interruption detection circuit of the present invention includes an AC input photocoupler that half-wave rectifies an AC input and outputs it, and a waveform shaping gate that waveforms the output signal of the AC input photocoupler to generate and output pulses. and a counter that counts the pulses output from the waveform shaping gate.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention.

The AC power supply instantaneous interruption detection circuit shown in Fig. 1 includes a current limiting resistor 2 that limits the current of AC input, an AC input cuff coupler 3 that outputs half-wave rectification of the AC input, and a waveform shaping of the output signal of the AC input cuff coupler 3. The waveform shaping gate 5 includes a waveform shaping gate 5 that generates pulses, and a ternary counter 6 that counts the pulses output from the waveform shaping gate 5.

Next, the operation will be explained.

FIG. 2 is a waveform diagram showing signal waveforms of the AC power supply instantaneous interruption detection circuit of FIG. 1.

A case will be described in which the AC input applied to the input terminals 1a and 1b misses half a cycle as shown in FIG. 2(a).

A applied to the photocoupler 3 via the current limiting resistor 2
The C input is as shown in Figure 2 (b) by the rectification function of the photocoupler 3.
) is converted to the waveform shown below. The signal shown in FIG. 2(b) is turned into a pulse signal shown in FIG. 2(c) by the waveform shaping gate 5, and is applied to the reset input of the ternary counter 6 for detecting instantaneous interruption. As shown in FIG. 2(d), the ternary counter 6 is driven by a tarok signal 4 having a frequency five times that of the AC input. While the AC input is normal, the waveform shaping gate 5
The ternary counter 6 is periodically reset by the output pulse of the ternary counter 6, and the counter output signal 7 of the ternary counter 6 maintains a low level as shown in FIG. 2(e), but when the AC input is ), the pulse signal that resets the ternary counter 6 is missing, and the ternary counter 6
is counted out, and the counter output signal 7 is as shown in Fig. 2 (e
), it becomes High level and outputs the detection of the lack of AC input.

〔Effect of the invention〕

As explained above, the present invention uses an AC input photocoupler in an AC power supply instantaneous interruption detection circuit, thereby maintaining insulation between an AC circuit and a DC circuit with a small number of components. This has the effect that a detection circuit can be configured.

1. Brief Description of the Drawings FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a waveform diagram showing signal waveforms of the AC power supply instantaneous interruption detection circuit of FIG.

la, lb...Detection circuit input terminal, 2...
...Current limiting resistor, 3...AC photocoupler,
4... Clock signal, 5... Waveform shaping gate, 6... Ternary counter, 7...
・Counter output signal.

Figure 21’ Agent Patent Attorney Susumu Uchihara

Claims (1)

[Claims] an AC input photocoupler that half-wave rectifies an AC input and outputs it; a waveform shaping gate that shapes the output signal of the AC input photocoupler to generate and output pulses; and a waveform shaping gate that outputs a pulse that is output from the waveform shaping gate. An AC power supply instantaneous interruption detection circuit comprising a counter that counts pulses.