JP3426910B2 - Infrared data receiver - 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 data receiver which prevents malfunctions caused by incident ambient light such as sunlight or incandescent light whose frequency is lower than the signal transmission speed.

[0002]

2. Description of the Related Art A basic circuit configuration of a conventional infrared data receiver is shown in FIG.

That is, the conventional infrared data receiver is
A photoelectric conversion circuit 81 that converts the received infrared data into an electric signal, a noise removal circuit 82 that removes low-frequency ambient light noise such as sunlight or incandescent light from the output signal of the photoelectric conversion circuit 81, and this noise removal circuit. An amplifier circuit (amplifier) 83 that amplifies the output of the amplifier 82 to a predetermined level and an output circuit 84 that shapes the waveform of the output of the amplifier 83 are provided.

FIG. 10 shows the output waveform of each circuit block shown in FIG. That is, the signal light waveform S51 received by the light receiving element (not shown) of the photoelectric conversion circuit 81
On the other hand, the waveform S52 of the signal amplified by the amplifier 83 through the noise removal circuit 82 is a waveform obtained by differentiating the pulse signal. When the output waveform S52 from the amplifier 83 becomes larger than the detection voltage V1, the output voltage of the output circuit 84 is inverted and becomes the output waveform S53.

FIG. 11 shows an example of a more specific circuit block diagram of the above-mentioned conventional infrared data receiver.

In this example, a photodiode 81a is used as a photoelectric conversion element, and the amplifier 83 is divided into two stages (amplifiers 83a and 83b) to obtain a large gain.
The noise removal circuit 82 is composed of an ABCC (auto bias current control) circuit 82a and an AC coupling circuit (AC coupling capacitor 82b and resistor 82c), and the output circuit 84 uses a comparator 84a.

The ABCC circuit 82a has a pre-stage amplifier 83.
The amplifier 83a is for preventing a from being saturated.
Is a circuit that takes out the low frequency component of the output voltage of 1 by a low pass filter, converts it into a current, and supplies the current to the input of the amplifier 83a so as to cancel the low frequency current component of the photodiode 81a. The AC coupling circuit is a circuit that extracts a harmonic component of the output voltage of the amplifier 83a with a high pass filter (that is, a low cut filter).

In the circuit shown in FIG. 11, the waveform of each part when low-frequency ambient light noise such as sunlight or incandescent light is not incident on the photodiode 81a is shown in FIG.
Is the same as.

[0009]

On the other hand, an infrared signal (pulse data signal) containing a harmonic component and low-frequency ambient light noise such as sunlight or incandescent light are generated by the photodiode 81a.
FIG. 12 shows the waveform of each part when incident on the.

That is, when low-frequency disturbance light noise is incident on the photodiode 81a, the ABCC circuit 82a operates. The ABCC circuit 82a has a low-pass filter (integrator circuit). Therefore, when the integrating circuit is connected in parallel with the amplifier 83a as shown in FIG.
The output voltage of 3a is differentiated. Since the signal is differentiated again by the AC coupling circuit, the output voltage waveform of the amplifier 83b becomes the waveform S54 shown in FIG.

As a result, the output voltage of the amplifier 83b becomes larger than the detection voltage V1 in the unnecessary portion (indicated by reference numeral 92), and the malfunction pulse 93 is generated in the output waveform S55 of the comparator 84a. However, this malfunction pulse 93 does not occur as shown in FIG. 13 when the amplitude of the output voltage of the amplifier 83b is not very large (for example, when the reception distance is long), and when the amplitude of the output voltage is large to some extent. (For example, when the reception distance is short).

The present invention was devised to solve such problems, and its purpose is to make an infrared signal and low-frequency disturbance light noise such as sunlight or incandescent light incident on an infrared data receiver. It is an object of the present invention to provide an infrared data receiver that can reduce malfunctions (a signal is not output from the output of the receiver, or an unnecessary signal is output) that occurs when there is an error.

[0013]

In order to solve the above-mentioned problems, an infrared data receiver of the present invention comprises a photoelectric conversion circuit for converting received infrared data into an electric signal, and a low frequency signal from an output signal of the photoelectric conversion circuit. Noise eliminating circuit for eliminating the ambient light noise, the first and second amplifier circuits connected in series for amplifying the output of the noise eliminating circuit to a predetermined level, and the output of the second amplifier circuit to one input terminal. And a detection voltage is introduced to the other input terminal of the comparator, and the noise removing circuit includes the first amplifying circuit.
Auto bias current controller connected in parallel to
Connected between the first amplifier circuit and the second amplifier circuit
Infrared data receiver including an AC coupling circuit, the output voltage of the first amplifier circuit or the second amplifier circuit
Using the auto bias current control circuit
Of a malfunction pulse due to twice differentiation between the AC coupling circuit and
The configuration is provided with a malfunction prevention circuit that generates an increased voltage for preventing the above and adds it to the detected voltage .

[0014] According to the infrared data receiver of the present invention
For example , the malfunction prevention circuit may be the output voltage of the first amplifier circuit .
The pressure is used to generate an increased voltage, which is added to the detected voltage .

[0015] According to the infrared data receiver of the present invention
For example , the malfunction prevention circuit is configured to peak-hold the output voltage of the second amplifier circuit and add this hold voltage to the detection voltage.

[0016] In addition, according to the infrared data receiver of the present invention
If the malfunction prevention circuit, and the peak hold <br/> output voltage of opposite phase of the second amplifier circuit is configured to apply a this hold voltage to the detection voltage.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the electrical construction of the infrared data receiver of the present invention.

In the figure, 1 is a photodiode which is a photoelectric conversion element, 2 is an amplifier (first amplifier circuit) in the preceding stage,
Reference numeral 3 is an ABCC circuit, 4 is a capacitor for AC coupling, 5 is a resistor, 6 is an amplifier (second amplifier circuit) in the latter stage, and 7 is a comparator, and these configurations are the same as those of the conventional one shown in FIG.

In the present embodiment, in the above configuration, a malfunction prevention circuit (low-pass filter) 8 which receives the output of the amplifier 2 and adds the output to the detected voltage V1 is provided.

FIG. 2 shows the output waveform of each circuit block shown in FIG. 1, S1 is the waveform of the signal light incident on the photodiode 1, S2 is the output waveform of the amplifier 6, and FIG.
S3 is an output waveform of the comparator 7.

When the infrared signal and the low frequency disturbance light noise are incident on the photodiode 1, a malfunction pulse 93 is generated as shown in FIG. This malfunction pulse 93 occurs when the amplitude of the output voltage of the amplifier 6 is large to some extent (see FIG. 12). Therefore, the output voltage of the amplifier 2 is added to the detection voltage V1 through the malfunction prevention circuit 8 to increase the detection voltage V1 (the increased detection voltage is shown by the symbol V10 in FIG. 2), and thereby the malfunction pulse 1
0 (indicated by a broken line in FIG. 2) is prevented from occurring.

FIG. 3 shows a specific configuration example of the malfunction prevention circuit 8.

The malfunction prevention circuit 8 includes a constant current source 9, three transistors Q1 to Q3, and a capacitor C as shown in the figure.
1 and a resistor R1, and a transistor Q2
A node a, which is a base connection point of Q3, functions as a low-pass filter, and a voltage is output through the emitter of the NPN transistor Q3 and the resistor R1.

That is, when the DC component of the output voltage of the amplifier 2 increases, the voltage of the node a increases and the detected voltage V
1 increases. Here, by appropriately selecting the capacitance value c of the capacitor C1, the cutoff frequency fc of the low-pass filter is determined by fc = 1 / 2πrc (where r is the impedance of the node a when the capacitor C1 is not present). . Further, by appropriately selecting the resistance value of the resistor R1, the voltage component (increased voltage) added to the detection voltage V1 can be obtained.
Can be determined.

FIG. 4 shows another embodiment of the infrared data receiver of the present invention.

In the present embodiment, the malfunction prevention circuit is configured by the peak hold circuit 11 that peak-holds the output voltage of the amplifier 6, and the hold voltage is the detected voltage V.
It is configured to be added to 1. Since other configurations are similar to those of each circuit block shown in FIG. 1, the same reference numerals are given to the same blocks here, and detailed description thereof will be omitted.

FIG. 5 shows a concrete example of the configuration of the peak hold circuit 11.

The peak hold circuit 11 includes two constant current sources 12, 13 and ten transistors Q11 to Q2.
0, 1 capacitor C11 and 3 resistors R11 to R
It is composed of 13.

That is, when the output voltage of the amplifier 6 input to the base of the transistor Q11 becomes larger than the voltage generated in the resistor R11, the transistor Q17,
The charge is stored in the capacitor C11 by Q18. The time for which this charge is discharged from the capacitor C11 is determined by the capacitance value of the capacitor C11 and the constant current source 13.

FIG. 6 shows the output waveform of each circuit block shown in FIG. 4, S11 is the waveform of the signal light incident on the photodiode 1, S12 is the output waveform of the amplifier 6, and S is the waveform.
Reference numeral 13 is an output waveform of the comparator 7. The output voltage of the amplifier 6 is peak-held by the peak-hold circuit 11, and the detected voltage V1 is increased by adding this hold voltage to the detected voltage V1 (the detected voltage after the increase is shown by symbol V11 in FIG. 6). This prevents the malfunction pulse 12 (shown by a broken line in FIG. 6) from being generated.

FIG. 7 shows still another embodiment of the infrared data receiver of the present invention.

In this embodiment, the malfunction prevention circuit is configured by the peak hold circuit 11 for peak-holding the output voltage of the negative phase of the differential amplifier 6a, and the hold voltage is added to the detection voltage V1. is there. Since other configurations are similar to those of each circuit block shown in FIG. 1, the same reference numerals are given to the same blocks here,
Detailed description is omitted.

FIG. 8 shows the output waveform of each circuit block shown in FIG. 7, S21 is the waveform of the signal light incident on the photodiode 1, S22 is the output waveform of the differential amplifier 6a, and S23 is the comparator 7. Is an output waveform of. The output voltage of the opposite phase of the differential amplifier 6a is peak-held by the peak-hold circuit 11, and the detected voltage V1 is increased by adding the held voltage to the detected voltage V1 (the detected voltage after the increase is denoted by V12 in FIG. 8). This is to prevent the malfunction pulse 25 (shown by a broken line in FIG. 8) from being generated.

When peak-holding the in-phase output voltage of the differential amplifier 6a, it is necessary to lengthen the discharge time from the capacitor C11, as can be seen from FIG. When peak-holding the output voltage, the capacitor C
The discharge time from 11 can be shortened. That is,
It is possible to shorten the time during which the sensitivity to the signal decreases.

In the embodiment shown in FIG. 1, the output voltage of the amplifier 2 is used to reduce malfunctions by the low-pass filter, so that it is necessary to set the absolute voltage level. In the embodiment, since the in-phase or anti-phase output voltage of the amplifier 6 and the differential amplifier 6a is peak-held, the relative voltage may be set, so that malfunctions can be more reliably performed even when there are variations in elements. Can be reduced to.

[0037]

The infrared data receiver of the present invention comprises a photoelectric conversion circuit for converting received infrared data into an electric signal,
A noise removal circuit for removing low-frequency disturbance light noise from the output signal of the photoelectric conversion circuit, and first and second series-connected circuits for amplifying the output of the noise removal circuit to a predetermined level .
An amplifier circuit and a comparator in which an output of the second amplifier circuit is led to one input terminal and a detection voltage is led to the other input terminal, and the noise removal circuit is provided with the first amplifier.
Auto bias current controller connected in parallel to the width circuit
Between the trawl circuit and the first amplifier circuit and the second amplifier circuit
An infrared data receiver comprising an AC coupling circuit connected to the output of the first amplifier circuit or the second amplifier circuit.
Input voltage, using the auto bias current controller
Pulse due to the second differentiation between the circuit and the AC coupling circuit
The configuration is provided with a malfunction prevention circuit that generates an increased voltage that prevents the occurrence of noise and adds it to the detected voltage . Also, the present invention
According to the infrared data receiver, the malfunction prevention circuit, raw increased voltage with an output voltage of the first amplifier circuit
It is configured to be added to the detected voltage . As a result, malfunctions that occur when low-frequency ambient light noise such as sunlight or incandescent light is incident can be reduced.

Further, according to the Infrared Data receiver of the present invention
For example , the malfunction prevention circuit is configured to peak-hold the output voltage of the second amplifier circuit and add the hold voltage to the detection voltage. Therefore, the relative voltage may be set, so that variations in elements may occur. Even if there is, malfunction can be reduced more reliably.

Further, according to the Infrared Data receiver of the present invention
If the malfunction prevention circuit, and the peak hold <br/> output voltage of opposite phase of the second amplifying circuit, since it is configured to apply the hold voltage to the detection <br/> wave voltage, relative voltage Since the setting can be made in step 1, malfunctions can be more reliably reduced even if there are variations in elements. Moreover, since the discharge time from the capacitor of the peak hold circuit can be shortened, the time during which the sensitivity to signals is lowered can be shortened.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of an infrared data receiver of the present invention.

FIG. 2 is a timing chart showing output waveforms of each circuit block shown in FIG.

FIG. 3 is a circuit diagram of a malfunction prevention circuit.

FIG. 4 is a block diagram showing another embodiment of the infrared data receiver of the present invention.

FIG. 5 is a circuit diagram of a peak hold circuit.

6 is a timing chart showing an output waveform of each circuit block shown in FIG.

FIG. 7 is a block diagram showing still another embodiment of the infrared data receiver of the present invention.

8 is a timing chart showing an output waveform of each circuit block shown in FIG.

FIG. 9 is a block diagram showing a basic configuration of a conventional infrared data receiver.

10 is a timing chart showing an output waveform of each circuit block shown in FIG.

FIG. 11 is a more specific circuit block diagram of a conventional infrared data receiver.

FIG. 12 is a timing chart showing output waveforms of respective parts when an infrared signal and low-frequency disturbance light noise enter a photodiode.

FIG. 13 is a timing chart showing an output waveform of each part when an infrared signal and low-frequency disturbance light noise enter a photodiode.

[Explanation of symbols]

1 Photodiode 2 amplifier 3 ABCC circuit 4 AC coupling capacitors 5 resistance 6 amplifier 6a differential amplifier 7 comparator 8 Malfunction prevention circuit 11 Peak hold circuit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H04B 10/26 10/28 (56) References JP-A-8-265055 (JP, A) JP-A-9-8739 (JP, A) JP-A-7-231307 (JP, A) JP-A-4-196632 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04Q 9/00 H04B 10/06

Claims (4)

(57) [Claims] 1. A photoelectric conversion circuit for converting received infrared data into an electric signal, a noise removal circuit for removing low-frequency disturbance light noise from an output signal of the photoelectric conversion circuit, and an output of the noise removal circuit. Series connection that amplifies to level
First and second amplifier circuit continues, the output of the second amplifier circuit is led to one input terminal, composed of a comparator detected voltage is led to the other input terminal, wherein the noise removal
An auto circuit in which the other circuit is connected in parallel to the first amplifier circuit.
Bias current control circuit and the first amplification circuit
An infrared data receiver comprising an AC coupling circuit connected between the first amplification circuit and the second amplification circuit.
Or using the output voltage of the second amplifier circuit,
Twice the current control circuit and the AC coupling circuit
Generates increased voltage to prevent malfunction pulses due to
An infrared data receiver characterized by being provided with a malfunction prevention circuit for applying the detected voltage to the detected voltage . 2. The malfunction prevention circuit generates an increased voltage using the output voltage of the first amplifier circuit and adds the increased voltage to the detected voltage.
Infrared data receiver of claim 1, wherein Rukoto. 3. The malfunction prevention circuit peak-holds an output voltage of the second amplifier circuit, and holds the output voltage.
The infrared data receiver according to claim 1, wherein is added to the detection voltage. Wherein said malfunction prevention circuit, the output voltage of the reverse phase of the second amplifier circuit and a peak hold, the holes
The infrared data receiver according to claim 1, wherein a reception voltage is added to the detection voltage.