JPH0311996Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention provides a method for performing a predetermined operation in a remote control transmitter/receiver, such as channel selection on a television receiver, for example, when the first The present invention relates to an input prohibition circuit for a remote control receiver that blocks the first signal when the signal and a second signal accompanying the operation of the operating section on the side of the set body are applied to the remote control receiver.

(b) Prior art In general, there are two types of remote control methods for electronic devices such as television receivers and video tape recorders (VTRs): wired and wireless methods, with the latter wireless method, called wireless remote control, being the mainstream. I'm getting used to it. In such wireless remote control devices, ultrasonic waves, radio waves, or infrared rays are used, but malfunctions due to noise have been raised as countermeasures for all of them.
As shown in Japanese Patent No. 30074, a method for preventing malfunctions caused by noise has been proposed.

However, in addition to the countermeasures against malfunctions mentioned above, countermeasures are needed when, for example, when a television receiver is selecting a channel, a channel selection operation using a remote control transmitter and a channel selection operation using a channel button built into the television receiver are performed at the same time. becomes.

(c) Purpose of the invention The present invention prevents or prohibits the signals from the remote control transmitter of the TV receiver, for example, when operating the operating section of the TV receiver body, and prevents the signals from being transmitted from the remote control transmitter of the TV receiver when operating the operating section of the TV receiver. The present invention provides an input prohibition circuit for a remote control receiver that is controlled by a remote controller, and is particularly characterized in that a clamp capacitor is used for improving noise resistance, setting prohibition, and setting a prohibition period.

(d) Structure of the invention The invention provides a remote control receiver comprising a receiving circuit of a remote control receiver that receives a first signal transmitted from a remote control transmitter, and an input inhibiting circuit connected to the output side of the receiving circuit. In a differential amplifier, the base of one transistor is connected to the input terminal, the base of the other transistor is connected to a clamp capacitor, and the emitters are connected in common, and the base of one transistor is connected to the output terminal of the differential amplifier. and a second signal is applied to the base of the other transistor, and the emitter and collector are each commonly connected, and the collector is connected to the amplifier connected to the clamping capacitor and to the base of one transistor of the amplifier. The differential amplifier is configured to block an input signal from being applied to one transistor of the differential amplifier for a period when the second signal is applied to the input side of the amplifier and for a predetermined period.

(E) Embodiment The present invention will be explained with reference to the drawings. Fig. 1 is a principle circuit diagram showing the input prohibition circuit of the remote control transmitter/receiver of the present invention, Fig. 2 is an implementation circuit diagram of the input prohibition circuit, and Fig. FIG. 3 shows an explanatory waveform diagram. In the drawing, 1 is a photodiode for receiving a first signal as a transmission signal from a transmitter (not shown); 2;
is a reference voltage source, 3 and 4 are bias resistors, 5 is an operational amplifier, 6 is a tuning circuit for tuning amplification, 7
is an amplification transistor, 8 and 9 are time constant circuits 10
11 is an emitter follower stage, 12, 13, and 14 are constant current sources, 1
5 and 16 are series diodes, 17 is a series resistor, 1
8 and 19 are first and second transistors forming the differential amplifier 20 , 21 and 22 are third and fourth transistors forming the amplifier 23 , 24 is a clamping capacitor, 25 and 25' are output transistors, 26 is a load resistance, 27 is a DC power supply terminal, 2
8 is a control terminal to which a control signal as a second signal is applied, 29 is an output terminal, the broken line in Fig. 1 shows the detection section and the input inhibiting section, and Fig. 2 shows the constant current source 14
An example of an input inhibiting section using a current mirror 30 is shown below.

First, referring to FIG. 1, a signal from a remote control transmitter is applied to a photodiode 1, and a predetermined bias is applied to the photodiode 1.
A current flows through the operational amplifier 5, and the sine wave (for example, 40 KHz, FIG. 3C) signal is amplified by the amplification transistor 7, and the output side of the amplification transistor 7 coil 31
and the frequency determined by the capacitor 32 ( ₀ )
Emitter follower transistor 11
A signal of the frequency ( ₀ ) is added to the base of (waveform in Fig. 3A). The signal is applied from the emitter of transistor 11 to the base of one transistor 18 of differential amplifier 20 via level shift resistor 17. The collector of the transistor 18 is connected to the base of the transistor 21, and the collector of the transistor 21 is further connected to the base of the transistor 19 and the capacitor 24, so that when an AC signal is applied to the base of the transistor 18, the transistor The base of No. 19 follows its lowest point potential V _CC -2V _BE -IR. A charging current (I ₁ in the direction of the solid arrow) flows through the clamping capacitor 24 via the third transistor 21, and a discharging current flows through the constant current source 14 (I ₂ in the direction of the broken arrow).

Due to the tracking of the clamp capacitor 24, the third
As is clear from Figure B, the differential amplifier 20 has a frequency
It has an offset during the arrival of a signal of ₀ . As a result, the differential amplifier 20 becomes unresponsive to much noise present near voltage V1.

At this time, no control signal is applied to the terminal 28, the fourth transistor 22 remains off, and the signal with the frequency ₀ is transmitted to the output transistor 22.
5, the signal appears at the output terminal 29, and a signal obtained by integrating this signal is used to control a microcomputer (CPU) etc. as a controlled circuit connected to the next stage, for example, to perform a channel selection operation. Execute.

On the other hand, when a control signal is applied to the control terminal 28, the fourth
transistor 22 is turned on, and the base potential of the second transistor 19 is the same as that of the fourth transistor 22.
The voltage drops to the collector-emitter saturation voltage (V _CESAT ) of , one end of the clamping capacitor 24 becomes almost at ground potential, the second transistor 19 is turned on, and the first transistor 18 is cut off. Like, photodiode 1
Even if a remote control signal from a remote control transmitter is applied to , the base potential of transistor 18 is V _I −
It cannot be less than V _BE .

Therefore, the output transistor 25 is in a cut-off state, and the output terminal 29 is connected to the transistor 2.
5' amplifies the signal.

In order to inhibit the remote control signal using the control signal shown in FIG. 3D applied to the control terminal 28, it is necessary to once integrate the control signal shown in FIG. 3D. Therefore, in the present invention, the clamping capacitor 24 is used to perform integration and inhibit the remote control signal.

Here, the recovery time T from when the control signal disappears to when the signal from the remote control transmitter is received depends on the saturation voltage (V _CESAT ) of the output transistor 25 and the signal application in the active region of the second transistor 19. When the base potential at the time is V _B (clamp voltage), it is determined by the following formula.

T = C (V _B - V _CESAT ) / I ₀ In the above formula, C is the capacitance value of the clamp capacitor 24, I ₀ is the current value of the constant current source 14, and V _CE is the collector-emitter saturation voltage of the transistor 22. .
As an example, when the DC power supply voltage V _CC =5 (V), V ₁ =5-0.7×2-IR=2.9 (V), and the above-mentioned clamp voltage also becomes 2.9V. In the above formula, I represents the current flowing through the resistor 17 (resistance value R). In FIG. 3, C represents a signal applied to the base of transistor 11, D represents a control signal applied to terminal 28, and E represents base voltage V _B of transistor 19.

In this way, the clamp capacitor 24 can be used for improving noise resistance, shaping the waveform of the control signal from the main body of the device, and setting the prohibition period of the remote control signal.

Next, FIG. 2 shows a specific circuit example of the input inhibiting section 32 shown in FIG.
In the configuration shown in the figure, the collector current of the second transistor 19 is larger than the collector current of the first transistor 18, and in order to reduce this, a sixth transistor 33 is connected, and a constant current source is also connected. A current mirror 30 composed of transistors 34 and 35 is used as the fourth
The base of transistor 22 is controlled. As a result, the resistors 36 and 37 set the amplitude to a predetermined value, and the control signal is applied to the control input transistor 3.
3 and its output can be applied to the base of the fourth transistor 22.

(f) Effects of the invention According to the input prohibition circuit of the remote control receiver of the invention, even if a signal from the remote control transmitter is added as a control signal when operating the operating section on the main body of the set, this is prohibited. Furthermore, the prohibition period can also be set using a capacitor provided as a clamp capacitor, making it possible to use the circuit of the present invention.
When integrated into an IC, there is an advantage that it is sufficient to connect only one capacitor to its external terminal. Moreover, the capacitor 24 prevents malfunction even in the presence of noise during a small period.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an input prohibition circuit of the remote control receiver of the present invention, Fig. 2 is a circuit diagram showing an example of an input prohibition section used in the circuit, and Fig. 3 is an explanatory waveform diagram of the circuit. be. Explanation of main figure numbers, 1...Photodiode, 5
... operational amplifier, 6 ... tuned circuit, 20 ... first
differential amplifier, 23 ... second differential amplifier, 24
... Clamp capacitor, 25 ... Output transistor, 28 ... Control terminal, 29 ... Output terminal.

Claims (1)

[Scope of utility model registration request] A receiving circuit of a remote control receiver that receives a first signal transmitted from a remote control transmitter, and a first and second transistor whose emitters are commonly connected, and a base of the first transistor is connected to a receiving circuit from the receiving circuit. a differential amplifier to which a first signal is applied; a diode to prevent the base voltage of the first transistor from changing by more than a predetermined value; discharge and change the output voltage to the second
a clamp capacitor applied to the base of the transistor; a third transistor for feeding back the output signal of the first transistor to the base of the second transistor with the clamp capacitor as a load; and a third transistor for feeding back the output signal of the first transistor to the base of the second transistor; A second signal from the main unit corresponding to the machine is applied to the base of a fourth transistor, the collector of which is connected to the clamp capacitor as a load, and the output signal of the first transistor and the second signal are applied to the base of the fourth transistor. a logical sum output means for generating a logical sum output of signals, and during a period in which the second signal is applied to the base of the fourth transistor and a predetermined period after the period, the fourth transistor outputs the logical sum of the differential amplifier. An input prohibition circuit for a remote control receiver, characterized in that it blocks a first signal applied to a first transistor.