JP2636717B2 - Infrared communication circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared transmitting circuit, and more particularly to an infrared transmitting circuit in which the carrier of an infrared signal is variable.

[0002]

2. Description of the Related Art As shown in FIG. 4 (for example, Japanese Unexamined Patent Publication No. 62-2795), a conventional transmission circuit uses a switch 4 to generate carriers having different duties generated by a carrier generator 30.
At 0, it is switched by the selection signal 20.

The selection signal 20 is an external input,
The method is selected by the operator depending on the distance from the receiving side.

[0004]

However, in the conventional transmission circuit described above, it is necessary for the operator to select an appropriate carrier duty.

[0005] As described above, the conventional transmission circuit has a defect that an unexpected error or an error is caused because the duty of the carrier is artificially selected.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances, and accordingly, an object of the present invention is to solve the above-mentioned drawbacks inherent in the prior art, and to provide a carrier pulse according to the infrared intensity around the transmission circuit. Another object of the present invention is to provide a novel infrared transmission circuit which can control the power consumption to the minimum by selecting the duty of the infrared transmission circuit.

[0007]

In order to achieve the above object, an infrared transmitting circuit according to the present invention comprises an optical sensor for converting the intensity of infrared light as ambient noise into a voltage, and an output of the optical sensor as a digital signal. An A / D converter for converting the output of the A / D converter, an oscillating circuit for outputting a plurality of carrier pulses having different duties, and a selector for selecting an appropriate one of the outputs of the oscillating circuit based on the output of the A / D converter. It is configured with.

[0008]

Next, a preferred embodiment of the present invention will be described in detail with reference to the drawings.

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

Referring to FIG. 1, an optical sensor 1 measures infrared intensity (noise) around the present infrared transmission circuit, converts the infrared intensity into a voltage, and outputs the voltage. The optical sensor 1
(Light receiving frequency band) is matched with the light receiving characteristic of the infrared receiving circuit side.

The output of the optical sensor 1 is supplied to an A / D converter 2
Is converted into a selection signal for selecting a carrier with an appropriate duty.

The oscillation circuit 3 has a duty of 38 KH.
A carrier pulse of about z to 40 KHz is output.

The selector 4 outputs an appropriate output from the output of the oscillation circuit 3 in accordance with a selection signal which is an output of the A / D converter 2. The data signal 8 is pulse-modulated in the NAND 5 by the carrier pulse selected by the selector 4 and converted into an infrared signal by the infrared LED 6.

The infrared receiving circuit and the infrared transmitting circuit are generally used in a line-of-sight environment within 10 m, and it is considered that light intensity as a disturbance element in the surroundings, particularly, infrared light intensity is equivalent.

When the sensor 1 has a high infrared intensity in accordance with the received infrared intensity, a carrier having a large duty in the output of the oscillation circuit 3 is used. .

In this circuit, the infrared signal transmitted by the sensor is received by the sensor 1, and the drive signal of the infrared LED 6 is fed back to the A / D converter 2 so as not to malfunction. It is necessary to keep the output of converter 2 unchanged.

FIG. 2 is a block diagram showing a first specific example of the oscillation circuit shown in FIG.

Referring to FIG. 2, the oscillation circuit 3 includes an oscillator 31, a monostable multivibrator 32,
3 and 34. P0 indicates a carrier source signal output from the oscillator 31, P1 indicates a carrier signal, and PS1 indicates a modulated data signal.

FIG. 3 shows an oscillation circuit 3 of the circuit shown in FIG.
(Monostable multivibrators 32, 33, 3
4) is a waveform example of outputs A, B, and C of 4), where the duty increases in the order of C>B> A. Here, T0 is the period of the carrier source signal P0 (T0 = 1 / f0, f0 = 38
TP0 is the pulse width of the output of the monostable multivibrator 32, TP2 is the pulse width of the output B of the monostable multivibrator 33, and TP3 is the pulse width of the monostable multivibrator 34. The pulse width of the output C is shown.

As a second specific example of the oscillation circuit 3, an oscillator 31 and a carrier source signal P which is an output of the oscillator 31
It is also possible to use a circuit composed of a frequency dividing circuit (counter) for dividing 0.

A specific example of the selector 4 is A / D
It can be constituted by a logic circuit or a ROM or the like that selects the signals A to C according to the output 9 of the converter 2. In the case of the present embodiment, since the output of the oscillation circuit 3 is three (A, B, C), the A / D converter 2
It is sufficient that 2 bits are output. If the number of outputs of the oscillation circuit becomes five or more, the output of the A / D converter 2 also needs three bits and four bits.

[0022]

As described above, according to the present invention,
Since the duty of the infrared signal is controlled by the intensity of the surrounding infrared light, the effect that the power consumption that increases or decreases in proportion to the duty can be reduced to a minimum value corresponding to the surrounding situation is obtained.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a specific example of the oscillation circuit shown in FIG.

FIG. 3 is a diagram illustrating an example of an output waveform of the oscillation circuit illustrated in FIG. 1;

FIG. 4 is a block diagram illustrating an example of a conventional infrared transmission circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical sensor 2 ... A / D converter 3 ... Oscillation circuit 4 ... Selector 5 ... NAND 6 ... Infrared LED 7 ... Resistor 8 ... Data signal 9 ... A / D converter output 10 ... Data generation part 20 ... Switching signal 30 ... Carrier generating unit 31 ... Oscillator 40 ... Switch 50 ... AND 60 ... Control circuit 61 ... Key input / output control unit

Claims (2)

(57) [Claims] An optical sensor for converting infrared intensity as ambient noise into a voltage and an A / D converter for converting the voltage into a digital signal are provided in a transmitting circuit for infrared communication which performs pulse modulation such as a remote control. , Career
Oscillator for generating a source signal and triggering the output of the oscillator
As a carrier signal for different pulse modulation
An oscillation circuit having a plurality of monostable multivibrators and outputting a plurality of carrier pulses for pulse modulation having different duties; and an output of the oscillation circuit based on an output of the A / D converter. A selector for selecting one, and a drive signal of an infrared LED for the A / D converter.
Feedback to the infrared LED
Do not change the output of the A / D converter during the light emission period
And a feedback circuit. 2. The plurality of monostable multi-buys.
In place of a oscillator, a counter for dividing the output of the oscillator
The infrared transmitting circuit according to claim 1, further comprising a counter circuit .