JP2002199478A - Carrier detection circuit and infrared remote control receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier detection circuit and an infrared remote control receiver that can reduce the occurrence of malfunctions. SOLUTION: An output signal Dout denoting the presence of a carrier is fed back(FB) to a transistor(TR) 43 provided to a detector 34. When the output signal Dout is active, output Dett of the detector 34 that is the detection level of a pulse group is set to a constant voltage VC, and even when an input signal Sig to the carrier detection circuit 30 dose not exceed a carrier detection level Det due to the swelling of the Sig, the sensitivity is reduced by increasing the level Det, so as to make an integration output Int restore to the initial state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier detection circuit and an infrared remote control receiver suitably implemented as a demodulator for a signal containing a carrier.

[0002]

FIG. 14 shows a receiver 1 of the infrared remote controller.
15 is a block diagram showing an example of the configuration of the general receiver 1. FIG. In this receiver 1, the infrared signal is converted by the photodiode 2 into a photocurrent signal Iin as shown in FIG. 15A, and the photocurrent signal Iin is subjected to current-voltage conversion in the amplifier 3 and further to the amplifier 4. , And then input to the band-pass filter 5. In the band-pass filter 5, FIG.
5 (b), the carrier frequency component is extracted as indicated by reference numeral α1, and the detection circuit 6 further extracts the transmission code component of the baseband frequency from the carrier frequency component as indicated by reference numeral α11 in FIG. Is detected, and the detection output is compared with a predetermined threshold level indicated by reference numeral α12 in the output circuit 7, so that the presence or absence of the carrier is determined and the digital code signal is restored. It is output as an output signal Dout indicated by 15 (d). The output circuit 7 including the detection circuit 6 and the hysteresis comparator forms a carrier detection circuit.

FIG. 16 is an equivalent circuit diagram of a typical prior art carrier detection circuit 10. As shown in FIG. This carrier detection circuit 10 is disclosed in Japanese Patent Application No. 2000-234926 by the present applicant.
It was proposed in the issue. This carrier detection circuit 10
Comprises a detection circuit 11, an integration circuit 12, and the hysteresis comparator 7. The detection circuit 11 generates a carrier detection level Det from the output Sig of the band-pass filter 5, and the integration circuit 12 generates the output Sig. The result is compared with the carrier detection level Det, the result of the comparison is integrated, and the result is given to the hysteresis comparator 7.

It should be noted that this carrier detection circuit 10
In the detection circuit 11, a pulse of the carrier frequency to be detected by the detector 13 is detected in a group, the time during which the pulse group exists is integrated by the integrator 14, and the integrated output is used as the carrier detection level Det. It is to be. That is, the detector 13 is used not to directly generate the carrier detection level Det of the entire receiving system, but to generate the carrier detection level Det.

The detector 13 amplifies the difference between the output Sig and the carrier detection level Det at a high speed capable of sufficiently responding to a carrier frequency and outputs a voltage, and a high-speed amplifier 15 for outputting the voltage. And a capacitor c charged by the output voltage of the high-speed amplifier 15 via the diode d1.
1 and a constant current source 16 for discharging the capacitor c1 with a constant current i1.

The integrator 14 includes an amplifier 18 that outputs a current corresponding to a difference between a charging voltage of the capacitor c 1, that is, an output Dett of the detector 13 and a predetermined reference voltage Vs from a reference voltage source 17. , Which is charged with the output current of the amplifier 18 and outputs the charge voltage as the carrier detection level Det.

The integrating circuit 12 is a current output amplifier 1.
9, a capacitor c3, and a constant current source 20 for discharging the capacitor c3 with a constant current i2. The output Sig of the band-pass filter 5 is set to a carrier detection level D.
, and a current corresponding to the comparison result is expressed as a capacitance c3.
, The time during which the carrier is present is integrated and output as an integrated output Int.

FIG. 17 is a waveform diagram for explaining the operation of the carrier detection circuit 10. In the high-speed amplifier 15, FIG.
7 (a), when the difference between the output Sig of the band-pass filter 5 indicated by the reference sign β1 and the carrier detection level Det indicated by the reference sign β2 is amplified, as shown in FIG. In the period W1 during which the pulse of the carrier frequency is detected by the action, the capacitor c1 is charged, the output Dett, which is the detection level of the pulse group of the carrier frequency, is high, and the period W1 during which the pulse is not detected.
When the output becomes 2, the output Dett decreases due to the discharge by the constant current source 16 and becomes zero level. Thus, the period W1 is the time during which there is a pulse group of the carrier frequency to be detected as described above, and the integrator 14 integrates the period W1, and the integrated output shown in FIG.
This becomes the carrier detection level Det.

Here, the infrared signal is 30 to 60 k.
ASK modulated with a predetermined carrier of about Hz
In the prior art, the capacity for outputting the carrier detection level Det has been charged and discharged at the carrier frequency. On the other hand, the periods W1 and W2 have a time constant that is sufficiently longer than the carrier frequency of about 100 msec. The capacity c2 for outputting the carrier detection level Det is reduced to, for example, about 100 pF, so that it can be formed in an integrated circuit.

[0010]

However, in the above-described carrier detection circuit 10 of the prior art, the carrier detection level Det is reduced during the idle period for a code signal transmitted with a predetermined idle period. If this occurs, noise will be detected. Since one transmission code of the infrared remote controller is about 50 msec, pulses of the carrier frequency are detected as a group as described above, and the capacitor c2 is stored in the integrated circuit. The long discharge time constant is obtained as the capacity that can be created.

For this reason, malfunction can be prevented with respect to optical noise exceeding the discharge time constant, but malfunction can be prevented with respect to optical noise that periodically changes within the discharge time constant. There is a problem in that

FIG. 18 is a diagram showing waveforms of respective parts when continuous optical noise is input from an inverter fluorescent lamp or the like substantially equal to the carrier frequency of the infrared signal.
In FIG. 18A, the detector 13 outputs the signal Sig of the band-pass filter 5 indicated by reference numeral β11.
When the output Dett shown in (b) is derived and exceeds the reference voltage Vs, the carrier detection level Det indicated by reference numeral β12 in FIG. 18A increases with a long time constant, and in FIG. The integral output Int indicated by the reference symbol β13 also increases. If the threshold level of the output circuit 7 indicated by reference numeral β14 is exceeded, the threshold level is reduced due to hysteresis, and the output signal Dout shown in FIG. 18D is also inverted, resulting in malfunction.

However, this malfunction stops increasing the carrier detection level Det near the peak of the output Sig of the bandpass filter 5, and in this state, the amplifier 1
9, the output becomes low level due to the input offset of 9, and the constant current source 20 discharges the capacitor c3 with the constant current i2 to lower the integrated output Int. It can return to normal.

On the other hand, in reality, the optical noise of the fluorescent lamp includes other frequency components such as a commercial frequency component of a power supply line, and swells with other frequency components. A malfunction occurs due to optical noise that changes periodically within the discharge time constant. FIG. 19 is a waveform diagram for explaining the operation for such undulating optical noise. The waveforms in FIGS. 19A to 19D correspond to the waveforms in FIGS. 18A to 18D, respectively.

First, in the same manner as described above, the undulating output Sig from the band-pass filter 5 indicated by reference numeral β11a in FIG.
When the output Dett shown in (b) is derived and exceeds the reference voltage Vs, the carrier detection level Det indicated by the reference numeral β12a in FIG. 19A increases, and at the same time, the carrier detection level Det shown in FIG. Integral output In shown
t also rises. When the output level exceeds the threshold level of the output circuit 7 indicated by the reference symbol β14a, the threshold level is lowered due to hysteresis,
The output signal Dout indicated by 9 (d) is also inverted, and a malfunction occurs.

However, due to the swelling of the output Sig, the output Dett may become lower than the reference voltage Vs, whereby the carrier detection level Det decreases.
Again, the output Sig exceeds the carrier detection level Det.
Thus, the peak of the noise cannot be detected, and the integrated output Int repeatedly increases and decreases at a constant level, and does not become lower than the threshold level which is lowered due to the hysteresis. Therefore, the output signal Dout is not inverted, and a malfunction is caused. Will continue.

FIG. 20 (a) shows an example of a transmitted code signal, FIG. 20 (b) shows an output signal Dout during normal operation, and FIG. 20 (c) shows the undulating optical noise. 5 shows an output signal Dout in a malfunction state due to the above.
Even with the undulating optical noise, the noise is substantially captured, so that if the level of the transmission signal itself is large to some extent, it is possible to restore the data as shown in FIG. However, a code as a start code is added immediately before the data to the code signal of many remote controllers, and if the header is not recognized as shown in FIG. 20C, the subsequent data is recognized. Cannot be performed, resulting in a malfunction.

An object of the present invention is to provide a carrier detection circuit and an infrared remote control receiver capable of reducing malfunctions.

[0019]

A carrier detection circuit according to the present invention generates a carrier detection level based on a received signal and detects the presence or absence of a carrier using the carrier detection level. A detector that detects a pulse of a carrier frequency to be detected, and a pulse of the carrier frequency is detected in a group by integrating a time when an output from the detector is equal to or greater than a predetermined integration reference value, and the integrated output is detected. An integrator that outputs the carrier detection level and a level change circuit that relatively increases the output from the detector with respect to the integration reference value during a period in which the presence of a carrier is detected. It is characterized by.

According to the above configuration, the detector responds to noise superimposed on the carrier, and increases the carrier detection level created by the integrator. On the other hand, in the integrator, the transistor for charging and discharging in response to the presence or absence of the carrier has a responsiveness not to the carrier frequency but to the frequency of the baseband component to the integration capacity for outputting the carrier detection level. It suffices if a margin for the response of the transistor is secured and the charging / discharging current for the capacitor can be made a very small current.

As described above, even if the capacitor is a capacitor that can be integrated, a carrier detection circuit that detects the presence or absence of a carrier with high responsiveness is further provided with a level changing circuit to detect the presence of a carrier. time limit,
For example, as described later in detail, the output from the detector is increased relative to the integration reference value in the integrator.

Therefore, even if the pulse level is reduced due to the swell of a frequency lower than the carrier frequency, the output from the detector indicating the detection level of the pulse group of the carrier frequency is in a state of continuously detecting the carrier. A decrease in the carrier detection level due to the undulation is suppressed, and after the pulse level due to the undulation is recovered, the pulse level is reliably reduced to the carrier detection level or less, thereby preventing erroneous carrier detection.

In this manner, the baseband component and the noise component are separated from each other, the malfunction of the undulating noise is reduced, and the baseband component can be accurately detected.

In the carrier detection circuit according to the present invention, the level change circuit limits an output from the detector to a constant voltage slightly higher than the integration reference value during a period when the carrier exists. The output from the detector is relatively increased with respect to the integration reference value.

According to the above configuration, the output from the detector, which is the detection level of the pulse group, is limited to a constant voltage slightly higher than the integral reference voltage in the period in which the carrier exists, as compared with the period in which the carrier does not exist. , Corresponding to the swell of the pulse level.

Therefore, it is possible to eliminate a problem that the detection level of the pulse group becomes excessively high in a state where there is no carrier, and when an original signal is transmitted, it cannot be received.

Still further, in the carrier detection circuit according to the present invention, the level change circuit reduces a discharge current of a capacitor in an output stage of the detector during a period when the carrier is present, so that an output from the detector is reduced. Is relatively increased with respect to the integration reference value.

According to the above configuration, the discharge current is reduced in the period with the carrier compared to the period without the carrier with respect to the capacity of the output stage of the detector whose output voltage indicates the detection level of the pulse group. By setting the discharge time longer, it is possible to cope with the swell of the pulse level.

Therefore, it is possible to eliminate a problem that the detection level of the pulse group becomes excessively high in a state where no carrier is present and an original signal cannot be received when the original signal is transmitted.

In the carrier detection circuit according to the present invention, the level change circuit increases an input offset voltage of a reception signal to the detector during a period in which the carrier is present, thereby changing an output from the detector. It is characterized by an increase relative to the integration reference value.

According to the above configuration, by increasing the input offset voltage of the received signal to the detector, the signal level is apparently increased in the period where the carrier is present compared with the period where the carrier is not present. Respond to level swell.

Therefore, since the output from the detector is not directly manipulated, the time during which the sensitivity is reduced can be reduced.

Further, in the carrier detection circuit according to the present invention, the level change circuit reduces an integration reference value in the integrator during a period when the carrier exists.
The output from the detector is relatively increased with respect to the integration reference value.

According to the above configuration, by lowering the integration reference value of the integrator, the output level from the detector is apparently increased in the period where the carrier is present, compared with the period where the carrier is not present, so that the pulse is increased. Respond to level swell.

Therefore, since the output from the detector is not directly operated, the influence of new noise due to the control can be reduced, and the tolerance to malfunction can be improved.

Further, the infrared remote control receiver of the present invention
It is characterized by using any one of the above carrier detection circuits.

According to the above configuration, during the period in which the presence of the carrier is detected, the output from the detector is relatively increased with respect to the integration reference value of the integrator, and the reception of the undulating noise is suppressed. The malfunction of the machine can be reduced.

Further, the infrared remote control receiver according to the present invention inputs a reception signal obtained by receiving an infrared signal to a band-pass filter via an amplifier, extracts a carrier frequency component to be detected, and then outputs the carrier frequency component. A pulse of the carrier frequency is detected in a detection circuit, and a pulse of the carrier frequency is detected in a group by integrating a time when the detection result is equal to or more than a predetermined integration reference value, and the integrated output is used as a carrier detection level. In the infrared remote control receiver configured to detect the presence or absence of a carrier, a period in which the presence of a carrier is detected includes a gain changing circuit that reduces a gain of at least one of the amplifier and the band-pass filter. I do.

According to the above configuration, by detecting the pulses of the carrier frequency in groups, the infrared remote control receiver can integrate the capacity for integration for outputting the carrier detection level in the integrator. , A gain changing circuit is provided, and the gain of at least one of the amplifier and the band-pass filter is reduced during a period in which the presence of a carrier is detected.

Therefore, even if the pulse level fluctuates due to the swell of a frequency lower than the carrier frequency, the probability that the received signal becomes equal to or lower than the carrier detection level increases due to a decrease in the gain of at least one of the amplifier and the bandpass filter, and the carrier False detection can be prevented.

In the infrared remote control receiver according to the present invention, the gain changing circuit has a time constant when the gain is lowered.

According to the above configuration, by delaying the response of the control by the time constant, it is possible to reduce the influence of noise due to switching of the detection result of the presence / absence of the carrier, and to improve the resistance to malfunction. Can be.

[0043]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a block diagram showing an electrical configuration of the carrier detection circuit 30 according to the first embodiment of the present invention. The carrier detection circuit 30 generally includes a detection circuit 31, an integration circuit 32, and an output circuit 33. From the output Sig of the band-pass filter 5 in FIG. 14, in the detection circuit 31, pulses of the carrier frequency to be detected by the detector 34 are detected as a group, and the time during which the group of pulses is present is integrated by the integrator 35. The output signal Dout is created by comparing the output Sig with the carrier detection level Det in an integration circuit 32, integrating the comparison result, and discriminating the level in an output circuit 33 to generate an output signal Dout. And the carrier detection circuit 10 shown in FIG.

That is, the detector 34 outputs the output S
ig, and a difference between the carrier detection level Det, a high-speed amplifier 36 that amplifies at a high speed capable of sufficiently responding to the carrier frequency and outputs a voltage, a diode D1 that rectifies the output of the high-speed amplifier 36, It comprises a capacitor C1 charged with the output voltage of the high-speed amplifier 36 via a diode D1, and a constant current source 37 for discharging the capacitor C1 with a constant current I1, and performs a peak hold operation of the output Sig.

The integrator 35 calculates the charging voltage of the capacitor C 1, that is, the output Dett of the detector 34, and a reference voltage V which is a predetermined integral reference value from a reference voltage source 38.
s and a capacitor C2 charged with the output current of the amplifier 39 and outputting the charged voltage as the carrier detection level Det.

The integrating circuit 32 includes a current output amplifier 4.
0, a capacitor C3, and a constant current source 41 for discharging the capacitor C3 with a constant current I2. The output Sig of the bandpass filter 5 is set to a carrier detection level D.
and a current corresponding to the comparison result is stored in the capacitor C3.
, The time during which the carrier is present is integrated and output as an integrated output Int. The output circuit 33 is composed of a hysteresis comparator. The output circuit 33 discriminates the level of the integrated output Int from the integration circuit 32 to generate an output signal Dout of a baseband frequency.

It should be noted that this carrier detection circuit 30
Is provided with a feedback loop 42 that feeds back the output signal Dout from the output circuit 33 to the detector 34. When the output signal Dout is turned on by the transistor 43 to which the output signal Dout is supplied, a pulse group is output. The charging voltage of the capacitor C1, which is the detection level, that is, the output Dett of the detector 34 is set to a predetermined constant voltage VC that is substantially the maximum value, whereby the carrier detection level Det increases, and the sensitivity decreases. That is, the integral output Int can be returned to the initial state.

FIG. 2 is a waveform diagram for explaining the operation of the carrier detection circuit 30 configured as described above with respect to undulating optical noise. In FIG. 2A, the output Det shown in FIG. 2B is derived from the detector 34 by the output Sig of the band-pass filter 5 indicated by reference numeral γ1, and when the output Dett exceeds the reference voltage Vs, FIG. In FIG. 2A, the carrier detection level Det indicated by the reference numeral γ2 increases with a long time constant.
In (c), the integral output Int indicated by the reference numeral γ3 also increases. When the threshold level of the output circuit 33 indicated by reference numeral γ4 is exceeded at time t1, the threshold level is reduced due to hysteresis, and the output signal Dout shown in FIG. State.

However, in this state, the output Dett of the detector 34 is output by the transistor 43 as described above.
Is set to the constant voltage VC, even if the level of the output Sig shown in FIG. 2A is reduced due to the swell, the output Dett remains above the reference voltage Vs, and the carrier detection level Det becomes substantially the maximum value. To increase. As a result, the integrated output Int decreases and eventually falls below the threshold level of the output circuit 33 at the time t2, and the output signal Dout is turned off and returns to the normal state. When the output Dett becomes equal to or lower than the reference voltage Vs at the time t3, the carrier detection level Det also starts to decrease.

Although the above-described on / off operation of the output signal Dout is like an oscillation phenomenon, the cycle is relatively long because the time constant of the circuit is large as described above.
When the header of the transmission signal as shown in FIG. 20A is received with the output signal Dout turned off, FIG.
As shown by, the subsequent data can be correctly received without any problem. Further, even in the state where the on / off operation is repeated, the power consumption can be reduced as compared with the case where the on / off operation is always performed as shown in FIG. Since this does not occur in the state where the signal is being received, there is no practical problem.

As described above, when the output signal Dout, which has been detected as having a carrier, is turned on, the output Si
A state in which the output Dett indicating the detection level of the pulse group having the carrier frequency is maintained at a constant voltage VC higher than the reference voltage Vs for the undulation lower than the carrier frequency of g, and the pulse group is continuously detected in a pseudo manner. Thus, after the level of the output Sig due to the undulation is recovered, the integrated output Int is set to be equal to or lower than the threshold level of the output circuit 33, so that the output signal Dout can be reliably returned to the off state, and malfunction can be prevented. Thus,
The code signal of the baseband frequency can be separated from the undulating noise and detected accurately.

Here, for example, Japanese Patent Application Laid-Open No. Hei 6-188835
In order to eliminate shot noise generated in a photodiode and passing through a band-pass filter, Japanese Patent Application Laid-Open Publication No. H11-15064 focuses on the fact that the current due to the shot noise depends on the square root of the current due to incident light. It is configured to be input to an amplifier through a matching circuit that converts a current due to light into a square root.

However, any of the prior arts considering the elimination of such noises corresponds by manipulating the input level to the amplifier, and the carrier is detected by ordinary envelope detection. . In this regard, in the present invention and the aforementioned Japanese Patent Application No. 2000-234926, the carrier detection level Det substantially catches the peak of disturbance light noise,
That is, since the noise component is removed according to the level of the disturbance light noise, not only the shot noise but also a high noise removing ability can be exhibited.

FIG. 3 shows a second embodiment of the present invention.
5 will be described below.

FIG. 3 is a block diagram showing an electrical configuration of the carrier detection circuit 50 according to the second embodiment of the present invention. This carrier detection circuit 50 is similar to the above-described carrier detection circuit 30, and corresponding portions are denoted by the same reference numerals and description thereof will be omitted. It should be noted that in the carrier detection circuit 50, the aforementioned carrier detection circuit 30
Is the output Det of the detector 34 when the output signal Dout is on.
While t is maintained at a constant voltage VC, it is limited to a constant voltage Vc slightly higher than the reference voltage Vs.

Therefore, in connection with the detector 34, a voltage limiting circuit 51 for limiting the output Dett to the voltage Vc.
Is provided. The voltage limiting circuit 51 generally takes in the reference voltage Vs from the reference voltage source 38 and generates the voltage Vc slightly higher than the reference voltage Vs, and the feedback loop 42
And the output signal Dout is supplied to a line 53 from the capacitor C1 to the amplifier 39.
In the on state, the voltage Vc from the limiting voltage generating circuit 52 is applied, and in the off state, the limiting voltage generating circuit 52 is connected to the line 5.
And a switching element 54 that is open from the third position.

FIG. 4 is an electric circuit diagram showing a configuration example of the voltage limiting circuit 51. The voltage limiting circuit 51 includes a reference current source 55 and a reference current I
01 is turned on / off in response to the output signal Dout and turned back, and the transistors Q0 to Q3 forming the switch element 54, the resistor R1, the diode D10 forming the limited voltage generation circuit 52 for generating the voltage Vc, and the like. Transistors Q4 to Q9 and a constant current source 56;
Input transistor Q10 that takes in the output Data from
It is comprised including.

The transistor Q4 and the transistor Q5 form a pair, the base of the transistor Q4 is supplied with the reference voltage Vs, and the emitter is connected via a resistor R1 to the collector of the transistor Q2 supplying the reference current I01. , The collector is grounded via transistor Q6. On the other hand, the base of the transistor Q5 is a diode D1.
0, the collector of the transistor Q3 supplying the reference current I01 and the transistor Q10 of the input.
Connected to the emitter of a transistor Q9 paired with the transistor Q9, and grounded via a transistor Q8. Also,
The base of the transistor Q5 is connected to the connection point between the input transistor Q10 connected in series between the power supply lines and the constant current source 56. The base serves as the output terminal of the output Dett to the amplifier 39. The collector of the transistor Q2 is connected to the collector of the transistor Q6 forming a current mirror circuit with the transistor Q6.
7 is grounded.

Therefore, when the output signal Dout is off, the transistors Q0 to Q3 are turned off and the transistor Q0 is turned off.
4 to Q9 do not operate, a voltage lower than the output Data of the capacitor C1 by the voltage between the base and the emitter of the transistor Q10 is output to the output Dett, and the normal peak hold operation by the detector 34 is performed. . On the other hand, when the output signal Dout is on, the transistors Q0 to Q3 are turned on and the transistors Q4 to Q9 are activated, and the output Dett is Vc (Vc = Vs + (I01 / 2) slightly higher than the reference voltage Vs. ) · R1) is limited to a constant voltage.

FIG. 5 is a waveform diagram for explaining the operation against undulating optical noise. 5 (a) to 5 (d) correspond to the waveforms in FIGS. 2 (a) to 2 (d), respectively. As shown in FIG. 5B, when the output signal Dout turns on at the time t1, the output Dett is limited to a constant voltage of Vc.

Also in this case, when the output signal Dout in which the presence of the carrier is detected is turned on, the swell lower than the carrier frequency of the output Sig is prevented.
Output De indicating the detection level of the pulse group of the carrier frequency
tt is maintained above the reference voltage Vs, and the pulse group is continuously detected in a pseudo manner, whereby after a predetermined time, the integrated output Int is reduced below the threshold level of the output circuit 33, and the output signal Dout is reliably output. Can be returned to the off state, and malfunction can be prevented.

Further, when the output signal Dout is turned on by the voltage limiting circuit 51, the output Det, which is the detection level of the pulse group of the carrier frequency, is limited to a constant voltage Vc slightly higher than the reference voltage Vs. Therefore, it is possible to eliminate a problem that the output Dett becomes excessively high, the receiving sensitivity is reduced, and the original infrared signal cannot be received.

FIG. 6 shows a third embodiment of the present invention.
8 will be described below.

FIG. 6 is a block diagram showing an electrical configuration of a carrier detection circuit 60 according to the third embodiment of the present invention. This carrier detection circuit 60 is similar to the above-described carrier detection circuits 30 and 50, and corresponding portions are denoted by the same reference numerals and description thereof will be omitted. Notable is that
In the carrier detection circuit 60, the output signal Dout via the feedback loop 42 is supplied to the constant current source 67 of the detector 64 of the detection circuit 61, and the constant current source 67
Is to reduce the constant current I1 to a predetermined first current value I1off when the output signal Dout is in an off state and to a predetermined second current value I1on smaller than the I1off when the output signal Dout is in an on state. It is.

FIG. 7 is an electric circuit diagram showing a configuration example of the constant current source 67. The constant current source 67 includes a reference current source 68
, Four transistors Q11 to Q14, and two resistors R11 and R12. The reference current source 68, the transistor Q11, and the resistor R11 are interposed in series between the power supply lines, and the base of the diode-connected transistor Q11 has a transistor Q12 and a transistor constituting a current mirror circuit. The base of Q13 is connected. The collector of the transistor Q13 is connected to the capacitor C1 to extract the constant current I1, and the emitter is grounded via a resistor R12. On the other hand, the emitter of transistor Q12 is also grounded via resistor R12, and the collector of transistor Q12 is connected via transistor Q14 to a high-level Vcc power supply line. Transistor Q
The output signal Dout is supplied to the base of the signal generator 14 via a feedback loop 42.

The emitter area ratio of transistors Q11, Q12 and Q13 is formed to be 1: n: 1 (n> 1). Therefore, when output signal Dout is off, transistors Q14 and Q12 are off. The constant current I1
Is relatively large, and when turned on, the transistors Q14 and Q12 are turned on, and the current from these transistors Q14 and Q12 flows into the resistor R12, so that the constant current I1 is relatively small.
Becomes

The current values I1off and I1on are given by (kT / q) ln (I02 / I1off) where k is Boltzmann's constant, T is absolute temperature, q is elementary charge, and the current value of the reference current source 68 is I02. ) + I02 · R
11−I1off · R12 = 0 (kT / q) ln (I02 / I1on) + I02 · R1
1− (1 + n) I1on · R12 = 0 is set.

FIG. 8 is a waveform diagram for explaining the operation for undulating optical noise. 8 (a) to 8 (d) correspond to the waveforms of FIGS. 2 (a) to 2 (d) and FIGS. 5 (a) to 5 (d), respectively. I have. As shown in FIG. 8B, when the output signal Dout is turned on at the time t1, the discharge current I1 of the capacitor C1 by the constant current source 67 is reduced to I1on as described above. Dett gradually decreases and remains above the reference voltage Vs until the time t3.

In this way, it is also possible to prevent a malfunction due to the undulation, and to cope with the undulation by setting the discharge current I1 of the capacitor C1 to be longer and the discharge time longer. It is also possible to eliminate a problem that the output Dett becomes excessively high in a state where no carrier is present, the receiving sensitivity is reduced, and the original infrared signal cannot be received.

FIG. 9 shows a fourth embodiment of the present invention.
The following is a description based on FIG. 10 and FIG.

FIG. 9 is a block diagram showing an electrical configuration of a carrier detection circuit 70 according to the fourth embodiment of the present invention. The carrier detection circuit 70 is similar to the carrier detection circuits 30, 50, and 60 described above. Notable is that
In the carrier detection circuit 70, the output Sig of the bandpass filter 5 is output from the detector 74 of the detection circuit 71.
The input offset voltage of the high-speed amplifier 76 that amplifies the difference between the signal and the carrier detection level Det and outputs a voltage is increased when the output signal Dout is turned on.

FIG. 10 is an electric circuit diagram showing a specific configuration of the high-speed amplifier 76. The high-speed amplifier 76 includes a comparator 72 and an offset switching circuit 73. The comparator 72 determines the carrier detection level Det and the output S of the bandpass filter 5.
a pair of transistors Q21 and Q22 whose igs are respectively applied to their bases; a load resistor R21 connected to the emitter of the transistor Q22;
A constant current source 77 for supplying a current from the emitter of the first transistor 1 and the load resistor R21 to the emitter of the transistor Q22;
Transistors Q23 and Q24 are connected to the collectors of the transistors Q21 and Q22 and form a current mirror circuit with an equal area. The connection point between the transistor Q22 and the transistor Q24 is
An output terminal to the diode D1.

The constant current source 77 supplies a constant current of 2 × I03, so that the current flowing through the transistors Q23 and Q24 is I03. Where Sig> D
At the time of et, the input offset is approximately I03 × R21.

On the other hand, the offset switching circuit 73 comprises a pair of transistors Q25 and Q26 to which the output signal Dout and the predetermined reference voltage Vref from the reference voltage source 78 are respectively applied to the base, and the transistor Q25.
It comprises a constant current source 79 for supplying a current to the emitters of the transistors Q25 and Q26 in common, and transistors Q27 and Q28 connected to the collectors of the transistors Q25 and Q26 and forming a current mirror circuit with an equal area to each other. You. A connection point between the transistor Q26 and the transistor Q28 is connected to a connection point between the transistor Q22 and the load resistor R21.

Therefore, when the output signal Dout is at the ground level lower than the off reference voltage Vref,
The transistors Q25 to Q28 are turned off, and the input offset is I03 × R21, whereas the output signal Do
When ut goes to a high level higher than the ON reference voltage Vref, the transistors Q25 to Q28 turn on, the constant current I04 from the constant current source 79 flows into the load resistor R21, and the input offset increases to (I03 + I04) × R21. I do.

With this configuration, when the output signal Dout in which the presence of the carrier is detected is turned on, the level of the output Sig is apparently increased.
In the same manner as described above, for the undulation lower than the carrier frequency, the output Dett indicating the detection level of the pulse group of the carrier frequency is maintained above the reference voltage Vs, and the pulse group is continuously detected in a pseudo manner. The output signal Dout can be reliably returned to the off state by setting the integrated output Int to be equal to or lower than the threshold level of the output circuit 33 after a predetermined time, thereby preventing malfunction.

The point that the sensitivity is lowered by increasing the output Dett, that is, increasing the carrier detection level Det is the same as in the above-described carrier detection circuits 30, 50 and 60, but the output Dett is directly operated. Therefore, the time during which the sensitivity is reduced can be reduced.

FIG. 1 shows a fifth embodiment of the present invention.
1 and FIG. 12 are as follows.

FIG. 11 is a block diagram showing an electrical configuration of a carrier detection circuit 80 according to the fifth embodiment of the present invention. This carrier detection circuit 80 is similar to the carrier detection circuits 30, 50, 60, 70 described above. It should be noted that, in the carrier detection circuit 80, in the detection circuit 81, the reference voltage Vs of the reference voltage source 88 of the integrator 85 is used.
Is reduced when the output signal Dout is turned on.

FIG. 12 is an electric circuit diagram showing a specific configuration of the reference voltage source 88. The reference voltage source 88 includes a constant voltage generation circuit 82, a switching circuit 83, and an output buffer circuit 84. Constant voltage generator 8
2 includes transistors Q31 to Q36 and resistors R31 to R31.
A constant current I05 is supplied to the resistor R31 to generate a constant voltage of I05 × R31.

On the other hand, the switching circuit 83 outputs the output signal D
out and a pair of transistors Q37 and Q38 whose bases are respectively supplied with a predetermined reference voltage Vref from the reference voltage source 86, and the transistors Q37 and Q3.
A constant current source 87 for supplying a current to the emitters of the common 8;
Transistors Q39 and Q40 which are connected to the collectors of the transistors Q37 and Q38 and form a current mirror circuit with an equal area to each other. The connection point between the transistor Q37 and the transistor Q39 is
It is connected to a connection point between the transistor Q36 and the resistor R31.

The output buffer circuit 84 comprises transistors Q41 to Q43, a resistor R34, and a constant current source 89. The voltage at the connection point between the transistor Q36 and the resistor R31 to which the base of the transistor Q41 is connected, ie, the resistor R31 Of the transistor Q43
As the reference voltage Vs.

Therefore, when output signal Dout is at the ground level lower than off reference voltage Vref,
The transistors Q37 to Q40 are turned on, the constant current I06 from the constant current source 87 flows into the resistor R31, and the reference voltage Vs is (I05 + I06) × R31. On the other hand, when the output signal Dout is turned on the reference voltage Vref.
When the level becomes higher than that of the transistors Q37 to
Q40 turns off, and the reference voltage Vs drops to the aforementioned I05 × R31.

With this configuration, when the output signal Dout, in which the presence of a carrier is detected, is turned on, the reference voltage Vs is reduced, thereby suppressing the swell lower than the carrier frequency as described above. The output Dett indicating the detection level of the pulse group having the carrier frequency is maintained at a level exceeding the reference voltage Vs, and the pseudo pulse group is continuously detected. After a predetermined time, the integrated output Int is output to the output circuit 33. , The output signal Dout can be reliably returned to the off state to prevent malfunction.

By operating the reference voltage Vs instead of operating the output Dett, it is possible to reduce the influence of new noise accompanying such control.
The tolerance against the malfunction can be improved.

FIG. 1 shows a sixth embodiment of the present invention.
3 will be described below.

FIG. 13 is a block diagram showing an electrical configuration of a receiver 91 of the infrared remote controller according to the sixth embodiment of the present invention. In this receiver 91, the infrared signal is converted into a photocurrent signal Iin by a photodiode 92, and the photocurrent signal Iin is current-voltage converted by an amplifier 93 and further amplified by an amplifier 94, and then a band-pass filter 95. Bandpass filter 9
5, a carrier frequency component is extracted, a baseband frequency transmission code component is further detected from the carrier frequency component in a detection circuit 96, and the detection output is compared with a predetermined threshold level in an output circuit 97, whereby the carrier frequency is detected. Is determined, the digital code signal is restored, and output from the output circuit 97 as the output signal Dout. The output circuit 97 including the detection circuit 96 and the hysteresis comparator forms a carrier detection circuit.

It should be noted that in the receiver 91, the output signal Dout from the output circuit 97 via the feedback loop 42 is given to at least one of the amplifier 94 and the band-pass filter 95, and the output signal Dout
While out is on, their gain is reduced.

With this configuration, even if the pulse level fluctuates due to the swell of a frequency lower than the carrier frequency, the output Sig of the band-pass filter 95 is reduced due to a decrease in the gain of the amplifier 94 and / or the band-pass filter 95. The probability of becoming equal to or lower than the carrier detection level Det increases, whereby the integrated output Int of the detection circuit 96 can be set to be equal to or lower than the threshold level of the output circuit 97, and the output signal Dout can be reliably returned to the off state. Also, erroneous detection of the carrier can be prevented.

The gain of the amplifier 94 and / or the bandpass filter 95 is reduced with a predetermined time constant. Therefore, by delaying the response of the control by this time constant, it is possible to reduce the influence of noise due to the switching of the output signal Dout, and it is possible to improve the resistance to occurrence of malfunction.

Further, when the gain of the amplifier 94 is reduced, there is no change in the center frequency or the bandwidth of the band-pass filter 95. On the other hand, when the gain of the band-pass filter 95 is reduced, In addition, it is not necessary to consider the response delay due to the time constant of the carrier detection circuit, and the control accuracy can be improved.

[0093]

As described above, the carrier detection circuit of the present invention detects the carrier frequency pulse to be detected by the detector and integrates the time during which the output is equal to or greater than the integration reference value by the integrator. By detecting the pulse of the carrier frequency as a group and using the integrated output as the carrier detection level of the detector, the presence or absence of the carrier can be detected with high responsiveness even if the integration capacity can be integrated. In the carrier detection circuit, the level change circuit is further provided, and during the period in which the presence of the carrier is detected, the output from the detector is relatively increased with respect to the integration reference value in the integrator, and the carrier frequency is increased. Even if the pulse level decreases due to the swell of a lower frequency, the output from the detector indicating the detection level of the pulse group of the carrier frequency indicates that the carrier To maintain a state that continues to put out.

Therefore, a decrease in the carrier detection level due to the undulation can be suppressed, and after the pulse level due to the undulation has recovered, the pulse level can be reliably reduced to the carrier detection level or less, thereby preventing erroneous carrier detection. .

Further, in the carrier detection circuit of the present invention, as described above, the level change circuit limits the output from the detector to a constant voltage slightly higher than the integration reference value during the period when the carrier exists. Then, the output from the detector is relatively increased with respect to the integration reference value, and corresponds to the swell of the pulse level.

Therefore, it is possible to eliminate a problem that the detection level of the pulse group becomes excessively high in a state where no carrier is present and an original signal cannot be received when the original signal is transmitted. .

Further, in the carrier detection circuit according to the present invention, as described above, the level change circuit reduces the discharge current of the capacitance at the output stage of the detector during the period in which the carrier exists, whereby the detector Output relative to the integral reference value corresponds to the pulse level swell.

Therefore, it is possible to eliminate a problem that the detection level of the pulse group becomes excessively high in a state where there is no carrier and an original signal cannot be received when the original signal is transmitted. .

Further, in the carrier detection circuit of the present invention, as described above, the level changing circuit increases the input offset voltage of the received signal to the detector during the period in which the carrier is present, so that the level of the signal from the detector is increased. Is relatively increased with respect to the integration reference value to correspond to the swell of the pulse level.

Therefore, since the output from the detector is not directly manipulated, the time during which the sensitivity is reduced can be reduced.

Further, in the carrier detection circuit according to the present invention, as described above, the level change circuit reduces the integration reference value in the integrator during the period when the carrier is present, thereby changing the output from the detector. It increases relative to the integration reference value and corresponds to the swell of the pulse level.

Therefore, since the output from the detector is not directly manipulated, the influence of new noise due to the control can be reduced, and the tolerance against malfunction can be improved.

Further, the infrared remote control receiver of the present invention
As described above, the output from the detector increases relative to the integration reference value of the integrator during the period in which the presence of a carrier is detected using any of the above carrier detection circuits.

[0104] Therefore, it is possible to reduce the malfunction of the receiver due to the undulating noise.

Further, as described above, the infrared remote control receiver of the present invention can integrate the integration capacity for outputting the carrier detection level in the integrator by detecting the carrier frequency pulses in groups. In the infrared remote control receiver having the capacity, a gain changing circuit is provided, and the gain of at least one of the amplifier and the band-pass filter is reduced during the period in which the presence of the carrier is detected.

Therefore, even if the pulse level fluctuates due to the swell of a frequency lower than the carrier frequency, the probability that the received signal becomes equal to or lower than the carrier detection level increases due to a decrease in the gain of at least one of the amplifier and the band-pass filter. Can be prevented from being erroneously detected.

Further, in the infrared remote control receiver of the present invention, as described above, the gain changing circuit delays the response of the control by the time constant when the gain decreases.

Therefore, it is possible to reduce the influence of noise due to the switching of the detection result of the presence or absence of the carrier, and to improve the immunity to malfunction.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an electrical configuration of a carrier detection circuit according to a first embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of the carrier detection circuit shown in FIG.

FIG. 3 is a block diagram illustrating an electrical configuration of a carrier detection circuit according to a second embodiment of the present invention.

4 is an electric circuit diagram showing one configuration example of a voltage limiting circuit in the carrier detection circuit shown in FIG.

FIG. 5 is a waveform chart for explaining the operation of the carrier detection circuit shown in FIG.

FIG. 6 is a block diagram illustrating an electrical configuration of a carrier detection circuit according to a third embodiment of the present invention.

7 is an electric circuit diagram showing a configuration example of a constant current source in the carrier detection circuit shown in FIG.

8 is a waveform chart for explaining the operation of the carrier detection circuit shown in FIG.

FIG. 9 is a block diagram illustrating an electrical configuration of a carrier detection circuit according to a fourth embodiment of the present invention.

10 is an electric circuit diagram showing a specific configuration of a high-speed amplifier in the carrier detection circuit shown in FIG.

FIG. 11 is a block diagram illustrating an electrical configuration of a carrier detection circuit according to a fifth embodiment of the present invention.

12 is an electric circuit diagram showing a specific configuration of a reference voltage source in the carrier detection circuit shown in FIG.

FIG. 13 is a block diagram showing an electric configuration of a receiver of the infrared remote controller according to the sixth embodiment of the present invention.

FIG. 14 is a block diagram illustrating a configuration example of a receiver of the infrared remote controller.

15 is a waveform chart of each part in the receiver of FIG.

FIG. 16 is an equivalent circuit diagram of a typical prior art carrier detection circuit.

FIG. 17 is a waveform chart for explaining the operation of the carrier detection circuit shown in FIG.

FIG. 18 is a diagram illustrating waveforms of various parts of the carrier detection circuit when continuous optical noise is input.

FIG. 19 is a diagram illustrating waveforms of respective parts of the carrier detection circuit when undulating optical noise is input.

FIG. 20 is a waveform diagram showing a transmission code signal and a reception code signal of the infrared remote controller.

[Explanation of symbols]

30, 50, 60, 70, 80 Carrier detection circuit 31, 61, 71, 81 Detection circuit 32 Integrator 33 Output circuit 34, 64, 74 Detector 35, 85 Integrator 36 High-speed amplifier 37 Constant current source 38, 86 Reference Voltage source 39, 40 Amplifier 41, 56, 77, 79, 87, 89 Constant current source 42 Feedback loop (level change circuit, gain change circuit) 43 Transistor (level change circuit) 51 Voltage limit circuit (level change circuit) 52 Limit Voltage generation circuit 54 Switch element 55 Reference current source 67 Constant current source (level change circuit) 68, 78 Reference current source 76 High-speed amplifier (level change circuit) 72 Comparator 73 Offset switching circuit 88 Reference voltage source (level change circuit) 82 Constant Voltage generation circuit 83 Switching circuit 84 Output buffer circuit 91 Reception 92 photodiodes 93, 94 amplifier 95 band-pass filter 96 detection circuit 97 output circuits C1, C2, C3 capacitor D1, D10 diode Q0~Q10; Q11~Q14; Q21~Q28; Q3
1 to Q43 transistors R1; R11, R12; R31 to R34 Resistance R21 Load resistance

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5K004 AA01 AA03 BA02 DF04 5K048 CA13 DB04 HA06 5K052 AA12 AA14 BB02 BB20 CC01 DD24 EE04 EE18 EE24 FF11 GG16 GG45

Claims (8)

[Claims] A detector for detecting a pulse of a carrier frequency to be detected in a carrier detection circuit for generating a carrier detection level based on a received signal and detecting presence / absence of a carrier using the carrier detection level. An integrator for detecting a pulse of the carrier frequency in a group by integrating a time when an output from the detector is equal to or greater than a predetermined integration reference value, and outputting the integrated output as the carrier detection level; And a level change circuit that relatively increases the output from the detector with respect to the integration reference value during a period in which the presence of the carrier is detected. 2. The level changing circuit according to claim 1, wherein the output from the detector is limited to a constant voltage slightly higher than the integration reference value during a period when the carrier is present, thereby integrating the output from the detector. 3. The carrier detection circuit according to claim 1, wherein the carrier detection circuit increases relative to a reference value. 3. The level changing circuit according to claim 1, wherein the level change circuit reduces a discharge current of a capacitor in an output stage of the detector during a period in which the carrier is present, thereby making an output from the detector relative to an integration reference value. 2. The carrier detection circuit according to claim 1, wherein the number is increased. 4. The level changing circuit increases an input offset voltage of a received signal to the detector during a period in which the carrier is present, thereby making an output from the detector relative to an integration reference value. 2. The carrier detection circuit according to claim 1, wherein the number is increased. 5. The level changing circuit according to claim 1, wherein said level changing circuit decreases an integration reference value in said integrator during a period when said carrier is present, thereby increasing an output from said detector relative to said integration reference value. The carrier detection circuit according to claim 1, wherein 6. An infrared remote control receiver using the carrier detection circuit according to claim 1. 7. A reception signal obtained by receiving an infrared signal is input to a band-pass filter via an amplifier to extract a carrier frequency component to be detected, and then a carrier detection circuit detects a pulse of the carrier frequency. Infrared light for detecting a pulse of the carrier frequency as a group by integrating a time during which the detection result is equal to or greater than a predetermined integration reference value, and using the integrated output as a carrier detection level to detect the presence or absence of a carrier. An infrared remote control receiver, characterized in that the remote control receiver includes a gain changing circuit for lowering the gain of at least one of the amplifier and the band-pass filter during a period in which the presence of a carrier is detected. 8. The gain changing circuit according to claim 1, wherein when the gain decreases,
The infrared remote control receiver according to claim 7, having a time constant.