JP3675917B2 - Remote control signal identification circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, when a remote control receiving unit built in an electronic device such as a TV receiver receives a remote control signal, the remote control receiving unit misinterprets the remote control signal, and as a result, the electronic device malfunctions. The present invention relates to a remote control signal identification circuit.
[0002]
[Prior art]
At present, most electronic devices such as TV receivers have a remote control function (remote control function). FIG. 5 is a circuit block diagram showing a general remote control receiving unit, which is built in an electronic apparatus.
In FIG. 5, reference numeral (1) denotes a light receiving diode which receives a remote control signal generated from a wireless remote controller (not shown) provided outside the electronic device. Here, the remote control signal is a signal in which a specific frequency (for example, 38 KHz) is intermittently combined for each arbitrary time (for example, several tens of μsec), and a plurality of operations of the electronic device can be controlled by this combination. (2) is a first input amplifier, which amplifies the current flowing through the light receiving diode (1) and amplifies the amplitude of the remote control signal. (3) is a second input amplifier, which amplifies the output of the first input amplifier (2). (4) is a band-pass filter that extracts a specific frequency band of the remote control signal. (5) is a detector, which detects the output of the bandpass filter (4) to form an envelope. (6) is a drive circuit, which has a built-in comparator that uses a voltage lower than the envelope voltage of the bandpass filter (4) as a reference voltage. When the envelope voltage is higher than the reference voltage, an envelope of 5 V (high level) is generated. When the envelope voltage is lower than the reference voltage, 0V (low level) is output. The binary output of the drive circuit (6) is applied to a 5 V drive microcomputer (not shown), and remote control of the electronic device is realized based on the output of the microcomputer. Note that the power source Vcc of the electronic device is commonly applied to the remote control receiver.
[0003]
However, when the electronic device is a TV receiver, the TV receiver has a built-in horizontal oscillator for performing horizontal scanning on a cathode ray tube, and the oscillation frequency (16.6 KHz) of the horizontal oscillator is a power source as noise. It will be superimposed on the line. Then, the superimposed noise is first amplified together with the remote control signal by the first and second input amplifiers (2) and (3). Thereafter, since the superposed noise (16.6 KHz) is close to the specific frequency (38 KHz) of the remote control signal, it is attenuated to an amplitude smaller than the specific frequency of the remote control signal but passes through the band filter (4). Here, the amplitude of the superimposed noise that has passed through the band filter (4) exceeds the detection level of the detector (5) due to the amplification factors of the first and second input amplifiers (2) and (3). In this case, an extra envelope is formed in the portion where the superimposed noise is generated. As a result, the place where the output of the drive circuit (6) should originally be 0V becomes 5V, which causes a problem of causing malfunction of the electronic device.
[0004]
Therefore, in order to solve the above-described problem, it is only necessary to devise measures not to apply the power supply noise to the power supply input of the first input amplifier (2) at the first stage. FIG. 4 shows an example in which the above-described device is applied, and only the first input amplifier (2) of FIG. 5 is taken out in order to avoid duplication with the description of FIG.
In FIG. 4, (7) is a reference voltage unit, and (8) is an amplifying unit, which constitutes a regulator. Each power source of the reference voltage unit (7) and the amplifier unit (8) is commonly connected to the power source Vcc of the electronic device. As an operation, the reference voltage is output from the reference voltage unit (7). The reference voltage is amplified by the amplifying unit (8). That is, a voltage Vcc ′ equal to the power supply voltage Vcc is output from the amplifier (8). The voltage Vcc ′ becomes the power supply voltage of the first input amplifier (2). Since the power supply voltage Vcc ′ is regulated, even if the power supply Vcc causes noise fluctuation, it is not affected by the noise. Thus, if the countermeasure of FIG. 4 is taken, the problem of FIG. 5 can be largely solved.
[0005]
[Problems to be solved by the invention]
However, since the regulator includes a resistor and a transistor, thermal noise generated from the resistor and shot noise generated from the transistor are superposed on the power supply Vcc ′ although the levels are very small. Here, the thermal noise and the shot noise pass through the band filter (4), similarly to the power supply Vcc noise. The amplification factors of the first and second input amplifiers (2) and (3) are set so that the amplitudes of the thermal noise and shot noise that have passed through the band filter (4) exceed the detection level of the detector (5). In such a case, the electronic device malfunctions similarly to the case of FIG.
[0006]
Accordingly, an object of the present invention is to provide a remote control signal identification circuit capable of preventing an electronic device from malfunctioning based on thermal noise and shot noise generated from a regulator.
[0007]
[Means for Solving the Problems]
The present invention has been made to solve the above-mentioned problems, and is characterized in that a remote control for controlling the operation of an electronic device, which has a predetermined frequency and is intermittently generated every predetermined time. An input amplifier that receives a signal, a band filter that extracts the predetermined frequency band from the output of the input amplifier, a detector that detects the output of the band filter, and the remote control signal that corresponds to the remote control signal based on the output of the detector In a remote control signal identification circuit comprising: a drive circuit that generates a drive signal for controlling the operation of the electronic device; and a regulator that outputs a power supply voltage for the input amplifier. A noise filter for removing noise is provided.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Details of the present invention will be specifically described with reference to the drawings.
FIG. 1 is a circuit block diagram showing the present invention, in which a noise filter (9) is provided between the output of the amplifier (8) constituting the regulator and the power input of the first input amplifier (2). Thus, thermal noise and shot noise superimposed on the power supply Vcc ′ can be removed.
[0009]
FIG. 2 shows an embodiment of the noise filter (9), in which a smoothing capacitor (10) is provided between the output of the amplifier (8) constituting the regulator and the ground. For example, when the first and second input amplifiers (2) and (3), the band filter (4), the detector (5), and the drive circuit (6) constituting the remote control receiver are integrated, a smoothing capacitor (10) is an external component of the integrated circuit. In order to smooth the thermal noise and shot noise superimposed on the power supply Vcc ′, it is preferable to set the capacitance of the smoothing capacitor (10) to about 10 μF.
[0010]
FIG. 3 shows another specific example of the noise filter (9), in which the remote control receiver and the noise filter (9) are integrated.
In FIG. 3, (11) is a comparator, the-terminal is connected to the output of the reference voltage unit (7), and the + terminal is connected to the output of the amplifying unit (8). (12) (13) (14) are NPN type transistors, and the collector-emitter path is connected in series between the output of the reference voltage section (7) and the ground. (15) is a PNP transistor, (16) is a diode-connected NPN transistor, (17) is a PNP transistor, and the collector-emitter paths of the transistors (15), (16), and (17) are connected in series. Has been. The bases of the transistors (12) (15), (13) (16), (14) and (17) are connected, and the common emitters of the transistors (16) and (17) are connected to the output of the comparator (11). Has been. The emitter of the transistor (15) is connected to the input of the amplifying unit (8). (18) is a capacitor having a capacitance C, and is connected between the common base of the transistors (12) and (15) and the ground. (19) is an NPN type transistor, the base is connected to the output of the reference voltage section (7), and the emitter is grounded via a resistor (20). (21) and (22) are PNP transistors constituting a current mirror circuit. The emitter of the diode-connected transistor (21) is connected to the power source Vcc via the resistor (23), and the collector is connected to the collector of the transistor (19). The emitter of the transistor (22) is connected to the power source Vcc via the resistor (24), and the collector is connected to the emitter of the transistor (15). The transistors (19), (21), and (22) constitute a bias circuit.
[0011]
In FIG. 3, a case is considered where thermal noise and shot noise are superimposed on the reference voltage output from the reference voltage unit (7), and the reference voltage fluctuates in the positive direction. First, the output voltage of the comparator (11) fluctuates in the negative direction, and accordingly, the collector voltage of the transistor (13), the base voltage of the transistor (12), and the emitter voltage of the transistor (15) fluctuate in the positive direction. . Then, the input / output voltage of the amplifying unit (8) varies in the positive direction. As a result, the + terminal voltage of the comparator (11) varies in the positive direction. Therefore, the change width in the negative direction of the output voltage of the comparator (11) becomes small.
[0012]
Now, paying attention to the capacitor (18), since the emitter voltage of the transistor (15) increases by the amount of the increase in the base voltage of the transistor (12), the capacitor (18) is substantially charged and discharged. Not in a state. In other words, the capacitor (18) is equivalent to a state having a large capacity while actually having a small capacity. Specifically, if the current amplification factor of the transistor (15) is β, it is equivalent to the capacitance of Cβ being coupled between the emitter of the transistor (15), that is, the input of the amplifying unit (8) and the ground. Become.
[0013]
The above operation is repeated as long as a negative change occurs in the output voltage of the comparator (11). Here, in the process of repeating the above operation, each time the above operation is repeated, the capacitance of Cβ is accumulated and coupled to the emitter of the transistor (15). That is, every time the above operation in FIG. 3 is repeated once, the input capacity of the amplifier (8) constituting the regulator is increased by the power of Cβ (when the above operation is repeated n times, The capacitance is Cβ ↑ n), which is equivalent to a considerably large capacitance coupled to the input of the amplifying unit (8). It should be noted that even when the thermal noise and the shot noise are superimposed on the output of one reference voltage unit (7) constituting the regulator and the negative terminal input of the comparator (11) fluctuates in the negative direction, the above operation is performed. Similarly, it is possible to create an equivalent state in which a large capacitance is coupled to the input of the other amplifying unit (8) constituting the regulator.
[0014]
Thus, when the thermal noise and the shot noise are superimposed on the output of one reference voltage unit (7) constituting the regulator, and as a result, the output of the reference voltage unit (7) fluctuates in the positive direction and the negative direction. However, the noise can be smoothed and removed by making a capacitor with a large capacity equivalently at the input part of the other amplifier section (8) constituting the regulator, and the noise of the first input amplifier (2) can be removed. A stable power supply voltage Vcc ′ can be supplied. Here, the first input amplifier (2) is the first stage amplifier, and if the noise of the power input of the first stage amplifier is suppressed, the amplification factor of the second input amplifier (3) of the next stage is set large. Even so, noise detection at the detector (5) can be reliably prevented, and malfunction of the electronic device can be prevented.
[0015]
As described above, by providing an example of the noise filter (9) as shown in FIGS. 2 and 3, reliable remote control can be realized for an electronic device such as a TV receiver.
[0016]
【The invention's effect】
According to the present invention, in the regulator that supplies the power supply voltage to the first input amplifier that is the first stage amplifier of the remote control receiver, the noise filter that removes the specific thermal noise and shot noise generated from the regulator is provided. As a result, a stable power supply voltage can always be supplied to the first input amplifier, and an advantage that reliable remote control of the electronic device incorporating the remote control receiver can be obtained.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram showing a remote control signal identification circuit of the present invention.
FIG. 2 is a circuit block diagram showing a first specific example of FIG. 1;
FIG. 3 is a circuit block diagram showing a second specific example of FIG. 1;
FIG. 4 is a circuit block diagram showing a conventional circuit.
FIG. 5 is a circuit block diagram showing a conventional circuit.
[Explanation of symbols]
(2) First input amplifier (3) Second input amplifier (4) Bandpass filter (5) Detector (6) Drive circuit (7) Reference voltage unit (8) Amplification unit (9) Noise filter (10) Smoothing capacitor (11) Comparator (12) to (17) Transistor (18) Capacitor

Claims (2)

An input amplifier that receives a remote control signal for controlling the operation of an electronic device that has a predetermined frequency and is intermittently generated every predetermined time, a bandpass filter that extracts the predetermined frequency band from the output of the input amplifier, and the bandpass filter A detector for detecting the output of the detector, a drive circuit for generating a drive signal for controlling the operation of the electronic device corresponding to the remote control signal based on the output of the detector, and a reference voltage unit for generating a reference voltage And a regulator for amplifying the reference voltage and outputting a power supply voltage (Vcc ′) for the input amplifier, and a remote control signal identification circuit comprising:
The power source that operates the identification circuit, (Vcc) compares the output of the reference voltage unit and the output of the amplification unit, and the output of the reference voltage unit when the output of the reference voltage unit is larger than the output of the amplification unit A comparator that outputs the opposite phase of the change;
Emitter connected to an output of said comparator, a first transistor having a collector is grounded (17), an emitter connected to an output of said comparator, second transistor (16) collector and base are connected in common, the base Is connected to the base of the first transistor (17), the emitter is grounded, the base is the base of the second transistor (16), the emitter is the collector of the third transistor (14) A fifth transistor connected to the collector of the second transistor (16), an emitter connected to the collector of the fourth transistor (13), and a base connected to the fifth transistor (15). sixth transistor connected to the base of) (12), said fifth and sixth transistors (15 and 1 ) Having a capacitor and an emitter connected to the common base of the seventh transistor (19) whose ground is grounded via the first resistor (20) and whose base is connected to the output of the reference voltage unit, and whose collector is the seventh transistor An eighth transistor (21) having an emitter connected to the power supply voltage (Vcc) via a second resistor (23), a base commonly connected to the collector, and a base connected to the collector of the transistor (19); A ninth transistor (22) having an emitter connected to a power supply voltage (Vcc) via a third resistor (24) and a collector connected to the emitter of the fifth transistor (15) at the base of the transistor (21) from made, the output from the emitter of the fifth transistor input to the amplifier, the phase inversion times to apply a reverse phase of the output change of the comparator to said amplifier unit And, with a,
By making the output change of the comparator zero, a large-capacitance capacitor is equivalently coupled to the input of the amplifying unit, and superimposed on the output of the amplifier due to noise from the reference voltage unit A remote control signal identification circuit, comprising a noise filter for removing the generated noise. 2. The remote control signal identification circuit according to claim 1, wherein the first and fifth transistors have opposite polarities to the second, third, fourth and sixth transistors.

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