JPS6117643Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a light receiving circuit particularly suitable for use in, for example, a remote control device for a television receiver.

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, and the like. Among these, remote control devices that use light beams or ultrasonic waves are used for small-scale remote control such as controlling television receivers, etc. because the circuits that make up these devices are relatively simple. ing. In particular, remote control devices that use ultrasonic waves require that ultrasonic signals can be transmitted even if there are some obstacles between the transmitter that transmits the remote control operation signal and the receiver that receives the remote control signal. It was widely used because it could modulate ultrasonic waves with signals. However, this ultrasonic remote control device has disadvantages in that echoes are likely to occur and dead points occur. Furthermore, there is another drawback in that the ultrasonic remote control device malfunctions 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 rays in a general household, so the remote control device does not move erroneously, and the transmission characteristics of infrared rays from the transmitter to the receiver are better than those of visible light. It's because it's good. The light receiving circuits used in this infrared remote control device are generally those shown in FIGS. 1 and 2.

That is, FIG. 1 shows a block diagram for explaining a light receiving circuit of a receiving section in a remote control device. In this figure, reference numeral 1 is a light receiving element into which infrared rays are incident, and this light receiving element 1 is composed of a photo diode, a photo transistor, etc., and its cathode is connected to a power supply _VB in order to apply a bias to it. , and its anode is grounded via a resistor R, forming a photoelectric conversion circuit. The infrared signal incident on the light receiving element 1 is converted into a current signal, which is taken out from the resistor R as a voltage signal and supplied to the amplifier circuit 2. Therefore, the connection point between the light receiving element 1 and the resistor R is connected to the input end of the amplifier circuit 2. This amplifier circuit 2
amplifies a predetermined signal component of the input voltage signal and outputs the amplified signal (remote control operation signal component)
is configured to output from its output end.

The output end of the amplifier circuit 2 is connected to a band pass filter (BPF) 3 that allows only signals of a predetermined bandwidth (for example, a carrier signal for a remote control operation signal) to pass through, and the passed signal can be obtained from the output end of the BPF 3. It's becoming like that. That is, the output end of the BPF 3 is connected to the waveform shaping circuit 4 and supplies the remote control operation signal that has passed through the BPF 3 to the shaping circuit 4. The shaping circuit 4 is a circuit that converts a remote control operation signal into a predetermined waveform, and supplies this to a control circuit (not shown) or the like.

FIG. 2 is a block diagram showing a conventional light receiving circuit, and the same members as in FIG. 1 are given the same reference numerals and will be explained. The configuration shown in FIG. 2 is characterized in that a tuning circuit 5 is added to the input end of the amplifier circuit 2, and that the BPF 3 between the amplifier circuit 2 and the waveform shaping circuit 4 is removed. It has the same configuration as the one in FIG.
That is, the tuned circuit 5 has a resistor R and an inductance L.
and a capacitor C are connected in parallel.

Incidentally, recently, fluorescent lamps that are lit by an inverter circuit have been commercially available for the purpose of power saving. This fluorescent lamp generates a high frequency wave using an inverter circuit, and is turned on by this high frequency wave. This fluorescent lamp emits not only visible light but also infrared rays when lit.

The remote control device light receiving element 1 also receives infrared rays from this fluorescent lamp, and the amplifier circuit 2 amplifies this. Therefore, in the circuit shown in FIG. 1, as the distance between the fluorescent lamp and the light receiving element 1 becomes shorter, the circuit becomes saturated before reaching the final amplification stage of the amplification circuit 2. If the level of the infrared signal from the transmitter of the remote control device is lower than that of the fluorescent light, the infrared signal from the remote control device will not be amplified correctly and the signal will not function properly. There were times when I was unable to obtain proper remote control operation.

Furthermore, the circuit shown in FIG. 2 has the tuning circuit 5 at the first stage, which is advantageous in terms of the above-mentioned disadvantages. However, in this case, if the Q of the tuning circuit 5 is set high, ringing is likely to occur due to the action of the tuning circuit 5 when a strong level of infrared rays is received. Since this is amplified by the subsequent amplifier circuit 2, due to the ringing waveform, remote control devices using PCM (Pulse Code Modulation) or PWM (Pulse Width Conversion) methods receive light with the wrong code content. There are cases. As a result, the tuning circuit 5
It is not possible to obtain a high Q value, and in this case as well, the same problem as shown in FIG. 1 will occur.

As described above, the configuration of the conventional light receiving circuit has the disadvantage that normal remote control operation cannot be obtained due to a noise source emitting infrared rays that has been modulated at a high frequency, such as from a high frequency lighting type fluorescent lamp.

This invention was made in view of the above points,
A photoelectric conversion circuit that receives light such as infrared rays and converts it photoelectrically, a first amplifier circuit that amplifies the output signal of this photoelectric conversion circuit, and a first band that passes only the signal to be transmitted among the signals of this amplifier circuit. In the photodetector circuit consisting of a pass filter, a second amplification circuit that amplifies the output signal of the photoelectric conversion circuit and prevents the amplification degree from saturating under noise conditions in normal use, and a passband of the signal to be transmitted. A second filter separating the noise frequency band from the noise frequency band is disposed between the photoelectric conversion circuit and the first amplifier circuit, so that even if there is a noise source of high frequency modulated light beam, the remote control operation signal etc. can be reliably detected. It is an object of the present invention to provide a light receiving circuit that can obtain a signal to be transmitted.

An embodiment of the present invention will be described below with reference to FIGS. 3 and 4.

FIG. 3 shows a block diagram of a light receiving circuit according to an embodiment of the present invention. In this diagram,
The light receiving element 11 is an element that receives an infrared signal and converts it photoelectrically, and as mentioned above, it is a photo diode or a photo transistor, and its cathode is connected to the power supply +V _B in order to apply a bias, and its anode is connected to a resistor. It is grounded via 12. The light receiving element 11 converts the infrared signal into a current signal, extracts this as a voltage signal from the resistor 12, and supplies it to the amplifier circuit 13.
The connection point between the resistor 1 and the resistor 12 is connected to the input end of the amplifier circuit 13. This configuration is a photoelectric conversion circuit.

This amplifier circuit 13 is set to an amplification level that will not saturate when a noise source that outputs high-frequency modulated light, such as a high-frequency fluorescent lamp, is used under normal conditions in an ordinary household, and this circuit 13 is configured to amplify the remote control operation signal.

The output end of this amplifier circuit 13 is connected to a BPF 14 having a predetermined bandwidth (for example, a pass band width that allows only a carrier wave for a remote control operation signal to pass), and is configured to pass a predetermined signal. That is,
This BPF 14 sets the center frequency of this passband width to be a carrier wave frequency for a remote control operation signal, and sets the carrier wave frequency to a high frequency modulated light ray emitted from a noise source such as the fluorescent lamp, especially a high frequency infrared ray. It shall be configured so that it is different from the components. By configuring the BPF 14 in this way, the output signal of the BPF 14 can be obtained without attenuating the level of the remote control operation signal, and with the level of the infrared component from a noise source such as a fluorescent lamp being attenuated. It is becoming more and more popular.

Further, the output signal of this BPF 14 is configured to be supplied to a control circuit (not shown) via a normal amplifier circuit 15, BPF 16, and waveform shaping circuit 17. That is, it is assumed that the amplifier circuit 15, BPF 16, and waveform shaping circuit 17 correspond to the amplifier circuit 2, BPF 3, and waveform shaping circuit 4 in FIG. 1, respectively, and have the same performance as these.

The light receiving circuit having the above structure operates as follows.

The infrared rays received by the light receiving element 11 are photoelectrically converted and amplified by the amplifier circuit 13. At this time, the amplification circuit 13 is designed so that the amplification degree does not saturate under normal fluorescent lamp usage conditions, so that it can perform an amplification effect regardless of whether infrared rays are received, whether it is a signal to be received or a noise. It is.

Therefore, the output signal of the amplifier circuit 13 is
4, and only the remote control operation signal (signal to be received) is extracted from these infrared rays. This is supplied to a control circuit (not shown) through the amplifier circuit 15→BPF 16→waveform shaping circuit 17.

Since it operates in this way, the influence of ringing can be suppressed to a minimum, and damage prevention by fluorescent lights can be eliminated, and normal remote control operation can be obtained.

FIG. 4 shows a circuit diagram of a specific example of the light receiving circuit configured as shown in FIG. 3. In this figure, elements that are the same as those shown in FIG.
The light receiving element 11 has been described as using a photodiode D ₁ or the like, the anode of which is grounded via the resistor 12 . In this figure, the resistor 12 connects the anode of the light receiving element 11 to the collector of the transistor _Q1 via the resistor _R1 , and also connects the anode to the ground with a resistor _R2 ,
A series circuit consisting of R ₃ is arranged, and this resistor R ₁ and R ₂
The connection point of the circuit is connected to the base of a grounded emitter transistor to form a constant current circuit. still,
The light receiving element 11 has its cathode grounded via a bypass capacitor _C1 , and similarly its cathode connected to a power supply line _VLL via a resistor _R4 . This is a photoelectric conversion circuit.

The amplifier circuit 13 has the following configuration.
That is, the connection point between the light receiving element 11 and the resistor 12 is connected to the gate of a field effect transistor (FET) _Q2 via a capacitor _C2 . Also, this
FETQ ₂ has its gate grounded via a resistor _R5 , its source grounded via a parallel circuit consisting of a resistor _R6 and a capacitor _C3 , and its drain connected to the power supply line _VLL via a resistor _R7 . is connected to.
The drain of this FETQ ₂ is connected to the base of a common emitter transistor Q ₃ via a capacitor C ₄ . The base of this transistor _Q3 is grounded via a diode _D2 and connected to its collector via a resistor _R8 , and the collector is connected to the power supply line _VLL via a resistor _R9 . It is connected. This power line V _LL
connects the bypass capacitor C ₅ to its line V _LL
and ground, and is connected to the connection point V _p via a resistor R ₁₀ .

The signal output from the collector of the transistor _Q3 is configured to be supplied to the BPF 14 via a series circuit of a capacitor _C30 and a resistor _R30 .
This BPF 14 has a configuration in which an inductance L ₃₀ is connected in parallel to a capacitor C ₃₁ . In this embodiment, the BPF 14 is composed of a capacitor C ₃₁ and an inductance L ₃₀ , but it goes without saying that it may be composed of an active filter or the like that is a combination of a resistor, a capacitor, and an active element.

The amplifier circuit 15 is configured as follows. In other words, the output terminal of BPF14 is a capacitor.
It is connected to the base of transistor Q ₃₁ via C' ₃₁ . This transistor _Q31 has its emitter grounded via a semi-fixed resistor _VR , its collector connected to the power supply +12 [V] via a resistor _R31 , and its collector connected to the base via a resistor _R32 . In addition, the base thereof is grounded through a diode _D32 to form an amplifier circuit. still,
Voltage is supplied from the power supply +12 [V] to the connection point V _P through the resistor ₃₃ . transistor
The collector of Q ₃₁ is connected to the base of transistor Q ₃₂ via capacitor C ₃₂ . This transistor _Q32 has its base connected to the power supply +12 [V] via a resistor _R34 , and its base connected to a resistor _R35.
The configuration is such that it is grounded. This transistor _Q32 has its collector connected to +12 [V] via the input terminal of BPF16 and resistor _R36 , and its emitter is grounded via a parallel circuit of resistor _R37 and capacitor _C33 . An amplifier circuit is constructed by disposing a diode _D33 between the emitter and the base.

In addition, the BPF 16 includes a primary winding L _M1 connected to the primary input terminal and a secondary winding L for configuring the BPF.
A tuning circuit is formed by connecting a capacitor C ₃₄ to both ends of this secondary winding L _M2 , and a waveform is transmitted from the middle point of this secondary winding L _M2 via a detection diode D _{34 .} It is connected to the base of transistor _Q33 of shaping circuit 17.

Since this waveform shaping circuit 17 is a well-known Schmitt trigger circuit, a description of the configuration will be omitted and only the parts will be explained.

That is, symbols Q ₃₃ and Q ₃₄ are transistors, R ₃₈
R ₄₅ is a resistor, and C ₃₅ is a capacitor. The collector of the transistor Q ₃₄ is grounded through a series circuit _of resistors R ₄₄ and R ₄₅ .
₄₅ is connected to the base of transistor _Q35 , its emitter is grounded, and its collector is supplied to a microcomputer or the like.

According to the above configuration, the functions and effects shown in the block diagram shown in FIG. 3 can be obtained.

As described above, according to the present invention, by providing an amplifier circuit and BPF, normal remote control operation can be obtained even in the presence of a noise source of high frequency modulated light beams such as a high frequency lighting fluorescent lamp. There is an effect.

[Brief explanation of the drawing]

1 and 2 are block diagrams showing a conventional light receiving circuit, FIG. 3 is a block diagram showing a light receiving circuit according to an embodiment of the present invention, and FIG. 4 is a specific example of the circuit shown in FIG. 3. FIG. 11... Light receiving element, 13 and 14... Amplifying circuit, 14 and 16... Band pass filter.

Claims (1)

[Scope of utility model registration request] A photoreceiver circuit comprising a photoelectric conversion circuit which receives light such as infrared rays and performs photoelectric conversion, a first amplifier circuit which amplifies an output signal of the photoelectric conversion circuit, and a first bandpass filter which passes only a signal to be transmitted among the signals of the amplifier circuit, characterized in that a second amplifier circuit which amplifies the output signal of the photoelectric conversion circuit and does not saturate the amplification degree under noise conditions in normal use, and a second filter which sets the pass band of the signal to be transmitted away from the frequency band of noise are disposed between the photoelectric conversion circuit and the first amplifier circuit.