JPS60141037A - Infrared-ray remote control receiving circuit - Google Patents

Abstract

PURPOSE:To prevent mis-operation by adding a noise elimination circuit generating an output in response to a specific state of a pulse to an output side of an infrared ray signal pulse detecting circuit. CONSTITUTION:The noise eliminating circuit 17 is installed to the output side of the infrared ray signal pulse detecting circuit 10. When consecutive pulses Ps to be detected and a single shot noise pulse PN are produced at the output of the detection circuit 10, a capacitor 16 of a charge/discharge circuit 18 is charged at the high level section of the pulse and discharged at a low level section. When >=2 pulses are consecutive at least and its interval is within a prescribed time, a terminal voltage B is increased and exceeds a reference comparison voltage Vr of the comparator 20, the capacitor is discharged by a single shot pulse PN and the terminal voltage B restores to the initial state. In case of the former, the output of the comparator 20 is inverted and a Tr54 is conductive. The pulse input is waveform-shaped by an integration circuit and a pulse is generated at an output terminal 14. Thus, single shot pulse input is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an infrared remote control receiving circuit, and in particular, to avoid the influence of noise in the detection output of a receiving circuit used to remotely control channel switching, etc. of a television receiver using infrared rays. Regarding noise removal.

FIG. 1 shows a general infrared remote control receiving circuit. The transmitted infrared rays are converted into electrical signals by a light receiving element 6 connected between the power supply terminal 2 and the input of the amplifier 4, and then applied to the amplifier 4. A filter 8 constituting a tuning circuit is added to the amplifier 4, and an output tuned to a predetermined frequency is extracted from the amplifier 4. That is, the frequency of infrared rays used in this type of remote control I-roll is usually 38K Ilz, and is tuned by a filter 8 installed at the input stage to distinguish it from noise.

The output of the amplifier 4 is applied to a detection circuit 10, its peak value is detected, and after being waveform-shaped by an output circuit 12, it is taken out from an output terminal 14 as a control output to be applied to a predetermined control section.

However, in conventional infrared remote control receiving circuits, similar frequencies are used for recent high-frequency fluorescent lights, motor switch pulses, etc., so it is difficult to distinguish between signals emitted by these and remote control signals. There is a risk of erroneous operation.

An object of the present invention is to provide an infrared remote control receiving circuit that removes noise in the detection output and improves the S/N ratio.

This invention adds a noise removal circuit to the output side of a detection circuit that detects infrared signal pulses, which generates an output when at least two or more infrared signal pulses arrive in succession and the pulse interval is within a predetermined time. It is characterized by what it did.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.

FIG. 2 shows an embodiment of the infrared remote control receiving circuit of the present invention, and the same parts as those of the infrared remote control receiving circuit shown in FIG. 1 are given the same reference numerals.

In FIG. 2, a noise filter that generates an output when at least two or more infrared signal pulses arrive consecutively and the pulse interval is within a predetermined time is provided on the output side of a detection circuit 10 that detects infrared signal pulses. A circuit 17 is installed. Immediately, a charging/discharging circuit 18 is installed to charge/discharge the capacitor 16 in response to the detection output, and on the output side of this charging/discharging circuit 18, when the terminal voltage of the capacitor 16 exceeds a predetermined level, the output is reversed. A comparator 20 is installed.

The charge/discharge amount 1118 is ]・Raran jitter 2224.26
．． 28 and resistor 30, transistor 22.2
4.26 constitutes a switching circuit that performs a switching operation in response to the detection output pulse, and also forms a charging path for the capacitor 16, and the resistor 30 forms a discharging path. 1 - The bases of transistors 26, 28 are connected in common and a constant bias voltage VBt is applied to their bases.

Further, when the infrared remote control receiving circuit is configured with a semiconductor integrated circuit, the capacitor 16 and the resistor 30 are connected between the external terminal 32 and the reference potential point (GND) terminal 34, and the time constant thereof is determined by the infrared signal pulse. It is assumed that the setting is made so that charging is faster than discharging when at least two consecutive pulses ζ arrive and the pulse interval is within a predetermined time.

Comparator 20 also includes transistors 36, 38, 40 .
42, 44 and a resistor 46.

The terminal voltage of the capacitor 16 is applied to the base of the transistor 36, and the terminal 48 formed at the base of the transistor 38 is connected to a predetermined reference comparison voltage V at a threshold level that causes the comparator 20 to cause an output inversion.
r is applied from a constant voltage source (not shown).

The output circuit 12 includes transistors 50, 52, 5
4.56.58, a resistor 60, and a capacitor 64 connected to an external terminal 62, and is configured to shape the output of the comparator 20 into a waveform and take it out.

Based on the above configuration, its operation will be explained with reference to the operation waveforms shown in FIG.

FIG. 3A shows the output pulses of the detection circuit 10, where the continuous pulse train portion PS is the infrared signal pulse to be detected,
The emitted pulse PN is a noise pulse.

When these pulses are applied to the base of transistor 22, during the high level portion of the pulse, transistor 22 is conductive and transistor 24 is non-conductive, so that capacitor 16 is charged.

Further, in the low level section of the pulse, the transistor 22 is non-conductive and the transistor 24 is conductive, so that at the same time the charging current is released, the capacitor 16 is connected to the resistor 30.
is discharged through. 'FIG. 3B shows the transition of the terminal voltage of the capacitor 16 due to this charging and discharging. That is,
When a burst signal consisting of at least two consecutive infrared signal pulses arrives and the interval between them is within a predetermined time, the terminal voltage of the capacitor 16 increases proportionally and exceeds the reference comparison voltage Vr of the comparator 20. However, with a single pulse, the voltage Vr is not reached and the capacitor 16 is discharged.
The terminal voltage of returns to its initial state.

When the terminal voltage of the capacitor 16 exceeds the reference comparison voltage Vr, the output of the comparator 20 is inverted, the pulse voltage shown in FIG. 3C is applied to the base of the transistor 54, and the transistor 54 becomes conductive in its high level section. become a state.

This pulse input is shaped into a waveform by the integrating circuit of the capacitor 64, and a pulse shown in the third diagram is generated at the output terminal 14.

With such a configuration, it is possible to avoid single pulse inputs, so noise and the signal to be detected can be distinguished, and the S/N
By improving the ratio, the number of components can be reduced and the circuit configuration can be extremely simplified.

In addition, in the example, two or more shots were set as the detection criterion, but
The detection standard may be set to 3 or more shots, and the capacitor 16
The value of the time constant of the resistor 30 can be set to a desired value.

As explained above, according to the present invention, highly accurate remote control can be realized by removing noise in the detection output and improving the S/N ratio.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an infrared remote control receiving circuit, FIG. 2 is a circuit diagram showing an embodiment of the infrared remote control receiving circuit of the present invention, and FIG. 3 is an explanatory diagram showing its operating waveforms. 10...Detection circuit, 12...Output circuit, 17...
Noise removal port, 16... Capacitor, 18... Charge/discharge circuit, 20... Comparator.

Claims (1)

[Scope of Claims] (Li) Noise that generates an output when at least two or more infrared signal pulses arrive in succession on the output side of a detection circuit that detects infrared signal pulses, and the pulse interval is within a predetermined time. An infrared remote control receiving circuit characterized in that an infrared remote control receiving circuit is added. (2) The noise eliminating circuit performs a switching operation in response to an infrared signal pulse to charge or discharge a capacitor so that the infrared signal pulse is at least a charging/discharging circuit that proportionally increases the charging voltage of the capacitor when two or more signals arrive in succession and the switching interval is within a predetermined time; and an output that is inverted when the terminal voltage of the capacitor exceeds a predetermined voltage level. 2. The infrared remote control receiving circuit according to claim 1, characterized in that the infrared remote control receiving circuit comprises a comparator.