JPS58175331A - Photodetecting circuit - Google Patents

Abstract

PURPOSE:To prevent a malfunction to a noise source which radiates the infrared rays underwent a high frequency modulation, by providing a frequency divider at a following stage of a peak detector and feeds the output of the divider to a BPF to obtain a stable output of a fixed amplitude at the BPF. CONSTITUTION:The output of a BPF13 obtained during a small input amplitude is fed to a peak wave detector 14. The detector 14 detects the peak of a small input amplitude wave, and this output is divided 26. The output of a frequency divider undergoes a peak wave detection 28 after passing through a BPF27 and is fed to an integration waveform circuit 29. As a result, a control signal of a fixed level is obtained at an output terminal 30 as long as an input signal exists and regardless of the amplitude of the input signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a light receiving circuit used in a remote control device t of a television receiver, etc.
- [Technical backbone of the invention] As is well known, a remote control (hereinafter referred to as a remote control) device remotely controls a controlled object using radio waves, light beams, ultrasonic waves, etc. Among these, remote control devices that use light beams or ultrasonic waves are used for small-scale remote control of television receivers and the like because the circuits and the like that constitute them can be relatively simple.

In particular, a remote control device that uses ultrasonic waves has the ability to transmit ultrasonic signals even if there are obstacles, no matter how small or large, between the transmitter that transmits the remote control operation signal and the receiver that receives the remote control signal. It is widely used because it can modulate ultrasonic waves with signals. However, this ultrasonic remote control device has drawbacks in that echoes are likely to occur and dead points occur. Furthermore, the ultrasonic remote control device rarely operates due to ultrasonic components in sounds generated from telephone bells, coins, etc.

Therefore, recently, remote control devices that use light, particularly infrared rays, have been proposed. This is because there is no noise source that generates high-frequency modulated infrared light in ordinary homes, so the remote control device does not generate IAhn, and the infrared light is transmitted from the transmitter to the receiver. Characteristics are visible light 111
This is because it is better than others. As a light receiving circuit used in this infrared remote control device, the one shown in FIG. 1 is generally used.

In FIG. 1, reference numeral 11 denotes a light-receiving element section into which infrared rays are incident, and this light-receiving element section 11 is provided with a photodiode, a phototransistor, etc., and is equipped with a photoelectric conversion function.

Due to infrared rays incident on this light receiving element section 11. Photoelectric conversion 11! The signal is amplified by the amplifier 12, and the signal is amplified by the amplifier 12.
is input. This band Shitonami! ! 113 is set to pass No. 111 (carrying ON signal for remote control operation signal) in a predetermined band portion.

Band>The signal that has passed through the P wave detector 13 is subjected to peak detection 431
4 for peak detection. This peak detector 14 has a detection level that is varied according to the strength of the input signal, so if the signal is larger than the disturbance light, the disturbance light signal is cut and the signal wave is detected. The output signal of the beam detector 14 is inputted to an integral waveform shaping circuit @15, where the waveform is shaped, and the output signal is derived from the output terminal 16 and supplied to the control circuit.

[Background technology introduction 1] Recently, fluorescent lamps that use an inverter circuit for lighting are on the market for the purpose of power saving and high performance.Uko fluorescent lamps generate a high frequency wave in the inverter circuit, and are lit by this high frequency. This is how it was done. This fluorescent lamp emits not only visible light but also infrared rays when lit. Therefore, when using this type of fluorescent lamp, the above infrared m I
If you have a J-control device, it will receive infrared rays when the fluorescent light is turned on, which is a problem! ! The signal is amplified by the amplifier 12 and inputted to the band 5R wave generator 13. Since the band P-wave device 13 generally has the band characteristics shown in Fig. 3, even if the tuning frequency is minus 9 points, it outputs a very small signal (No. 11).
Remote control operation - When there is no signal, the peak detector 14 may perform peak detection of the output and supply the signal to the control circuit. As a result, normal remote control operations may not be obtained and erroneous operations may occur. As described above, the above-mentioned conventional light receiving circuit has the problem that normal remote control operation cannot be obtained due to the noise source emitting infrared rays that have been subjected to frequency changes, such as in a high frequency lighting type fluorescent lamp. .

[Purpose of the invention]

This invention was made in view of the above circumstances, and provides a light receiving circuit that can prevent malfunctions in response to noise sources such as fluorescent lamps that emit infrared rays that have been modulated at high frequencies. The purpose is to provide.

[@Overview of Ming]

In this invention, by providing the splitter 26, the output of the bandpass filter 27 is made to have a stable and constant amplitude, as explained in FIGS. 5 and 6, regardless of the magnitude of the necessary input signal tR@. This prevents the IA from responding to unnecessary human input signals.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings. In other words, the same parts as those in FIG. A frequency divider 26, a band waver 27, a detector 28, and an integrating aSS type circuit 29 are connected in series at the subsequent stage.

The operation of the light receiving circuit of the present invention will be explained with reference to the operation signal waveform diagrams of FIGS. 5 and 6. The signal waveform shown in FIG. For the amplitude (3rd
Peak detection is performed (according to the characteristic A2 shown in the figure) to obtain an output hI as shown in FIG. This output is input to the divider 26 configured with flip-flops, so at the output terminal of the divider 26, a divided output of -1 as shown in Figure 5 is obtained. #l is band oscillator 2
7 (the suspension frequency is set to the divided output frequency 72 f o). The signal outputted from the band upp waver 27 becomes the signal d1 shown in FIG. 5d.

The 1M waveform generator 27 has a band characteristic as shown in Figure 4, J, and its center frequency is set to the divided output frequency fo/2. The output of this band>p waveform generator 27 is peak-detected by a peak detector 28 and then input to an integral waveform shaping circuit 29 . The integral waveform shaping circuit 29 has, for example, Schmitt Tori circuit characteristics, and is shown in Figure 5.
-1 shown in can be obtained.

On the other hand, FIG. 6a-- shows each part 1 to No. cedar at the time of large input amplitude. FIG. 6 shows the output of the bandpass filter 13, the sixth
The figure shows the output of the peak detector 14, and the 610th one shows the output of the branching unit 26.
Figure 6 d is the output of the band '/r wave a27, and Figure 6- is the output of the integral waveform shaping circuit 29.This can be seen by comparing the operating waveforms in Figures 5 and 6. As shown in Figures 5-1 and 6, this circuit uses a 72 frequency divider 26, so in the case of a small input amplitude or a large force amplitude, the duty ratio shown in Figures 5-1 and 6 (6) is As a result, if there is an input signal, a control signal of a constant level can be obtained at the output terminal 30 regardless of whether the amplitude is large or small.

Assuming that there is no frequency divider 26 and the output of the peak detector 24 is directly input to the band-pass waveform generator 27, the waveforms produced are as shown in FIGS. 7 and 8. FIG. 7 shows the operation Wl when the input amplitude is small; FIG. 8 shows the operation waveform when the input amplitude is large. That is, as can be seen by comparing the signals from Hatake to d in Figure 7 and a% to d in Figure 8, the output pulse duty of the peak detector 14 is different when the input amplitude is small and when the input amplitude is large ( (Fig. 7 b1 Fig. 8) Along with this, the output amplitude of the bandpass filter 27 also differs between small input amplitude and large input amplitude, as shown in Fig. 7-1 and Fig. 8. arise.

Therefore, a difference also occurs in the output level of the integral waveform shaping circuit 29 (d in FIG. 7 and d in FIG. 8). Therefore, minute J
Without the III converter 26, the detection output (transverse wave converter 28) will not be constant depending on the strength of the input signal, making it unstable, making it difficult to shape the integral waveform in the subsequent stage, causing delayed response, and malfunction. .

However, according to this circuit, as shown in comparison in Figures 5 and 6, it is possible to always obtain a stable and constant detection output regardless of the strength of the input signal, and the control signal is also accurate. It can be done.

Here, in this circuit, when the remote control signal is input, the output pulse duty of the divider 26 is constant regardless of the magnitude of the amplitude, so in such a case, the output pulse duty of the divider 27 is Shake 114! This becomes constant.

Therefore, the peak detection-reproduction of the peak detector 28 can be made constant. In other words, the waveform shaping circuit operating point is
It can be fixed at a constant level 1111@ shown in the figure. As a result, when an unnecessary signal with a different frequency (different from the remote control signal carrier frequency) is input, the output amplitude level of the band waver waver 27 decreases, peak detection is not performed, and false sensing operation is prevented. . For example, the infrared frequency emitted when a fluorescent lamp is turned on is in the band 5Palti12.
When an unnecessary signal is input, by keeping it away from the 12 times value of the same frequency of 7, the band t @ @ 2
Since the output of 7 is small, the operating point of the integral waveform shaping circuit is not exceeded, and unnecessary control signals are not output.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a light receiving circuit that does not perform any sensitive operation even if unnecessary infrared light subjected to high J4 wave modulation is input.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of a conventional light receiving circuit, FIG. 2 is an explanatory diagram of the configuration of an embodiment of the present invention, and FIGS. 2 band is the waveform characteristic diagram of the wave device, Figure 5 (●n~《book, Figure 6 (-) ~ (-1 is the operating signal waveform diagram of the circuit in Figure 2, Figure 7 (6) ~ (
d), Figure 8 1 to (d> are each sf/Ih production signal wave shadow signal waveform diagram obtained when the frequency divider 11 is removed from the circuit of Figure 12 1l...Light receiving confectionery part 12...・Amplifier" - 1st om region=, pe, 6 14...First peak detector 26...Frequency divider 27...Second band divider 28...Second peak detector 29...Representative for the applicant of the integral waveform shaping circuit Patent attorney Watae Fuhiko Figure 5
6WI (e) EE (e) Figure 7 Figure 8 (d) (d)
. □E

Claims (1)

[Claims] A first band door e into which the amplified output of the light receiving element section is inputted.
a and a peak detector into which the output of the band wave detector is input, and in which the amplitude level of the human input signal changes and a peak detection output pulse is obtained. 9. A light receiving circuit comprising: a second band frequency divider to which the output of the frequency divider is input; and a detector for peak detecting the output of the second band frequency divider. .