JPS626725Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a sound cancellation circuit in a remote control.

Conventionally, remote controls for electronic devices having audio circuits have had the disadvantage that clicking noise occurs in the audio output when the power is turned on or off.

The present invention is intended to provide a circuit that does not generate click noise in the audio output even in such a case.

First, the circuit configuration and operation of a conventional remote control controlled device receiving section will be explained. Since the circuit of the conventional controlled device receiving section is the same as that shown in FIG. 1 with the diode 14 removed, the circuit in FIG. 1 with the diode 14 removed will be described as the conventional circuit.

In the conventional circuit, reference numeral 1 denotes a remote control signal input section for a controlled device. This input section 1 has two output terminals, one of which is for turning the power on and off.
The control output terminal 2 is a control output terminal 3, and the other is a voice control output terminal 4. A control current limiting resistor 5 is a transistor,
6 is a relay coil, 7 is a relay contact, 8 is a D/A converter, 9 is an integrating circuit resistor, 10 is an integrating circuit capacitor, 11 is a connection point between 9 and 10,
Reference numeral 2 denotes a transistor, and 13 denotes a volume control section.

Next, to explain the operation of the conventional circuit, from the remote control transmitter, the power is turned on,
Signals related to OFF and signals related to volume UP and DOWN are sent. The signal related to the volume UP/DOWN control output is made up of variously changed numbers of rectangular wave pulses within a certain period of time, and the average value of these changes in magnitude. Now, when the aforementioned volume UP and DOWN control signals are input to the remote control signal input section 1 in FIG. The voltage at the connection point 11 between 9 and 10, which is input to the integrating circuit, gradually increases until it reaches a constant value, and that voltage is applied to the base of the transistor 12. The emitter follower voltage of the transistor 12 is then input to the volume control section 13, and the volume is controlled by controlling this.

Next, when a power ON signal is input to the remote control signal input section 1, the power is turned ON or OFF.
A high level voltage appears at the control output terminal 2.
Therefore, the transistor 5 operates via the resistor 4,
Current flows through the relay coil 6, its contacts 7 close, and the circuit of the electronic device starts operating. At this point, the volume control section 13 described above is already in operation, so that various click noises generated from the circuits of the electronic device are output to the outside.

Next, when a power OFF signal is input to signal input section 1, a low level voltage appears at output terminal 2,
Transistor 5 is cut off and relay coil 6
is non-conducting, contact 7 is open and the circuit of the electronic device enters the non-operating state, but at that point, voltage still appears at the connection point 11 between 9 and 10 of the integrating circuit, or the voltage gradually decreases. As a result, the click noise generated when the circuit of the electronic device enters a non-operating state is outputted to the outside through the volume control section 13.

As mentioned above, in the conventional circuit, the power supply
The drawback was that it produced a clicking noise when turned on and off.

In order to eliminate the above-mentioned drawbacks, the present invention has a charging capacitor 10 between the power ON/OFF control output terminal 2 of the signal input section and the connection point 11 between 9 and 10 of the integrating circuit, as shown in FIG. The above-mentioned problem is attempted to be solved by connecting the diode 14 in the direction in which the charge is discharged.

This can be explained using Figure 1. First, the power supply
When it is turned off and the electronic device circuit is in a non-operating state, the electric charge charged in the integrating capacitor 10 is in a state of being discharged through the above-mentioned diode 14 newly provided in the present invention. Therefore, turn on the power
When the power supply ON/OFF control output terminal 2 of the signal input section becomes a high level, a reverse polarity voltage is applied to the diode 14, so the diode is not conductive and the integration circuit is charged and connected. Point 1
The voltage of 1 increases along the CR curve as shown in FIG. 2a. Therefore, since the volume control output voltage gradually increases, the click noise of the electronic equipment circuit when the power is turned on does not occur in the audio output.

Next, when the power is turned off, the output terminal 2 of the signal input section 1 becomes a low level, so that the electric charge stored in the integrating circuit capacitor 10 is immediately discharged through the diode 14 as shown in FIG. 12 is immediately cut off, so that the audio output does not generate the clicking noise of electronic equipment circuits when the power is turned off.

According to this proposal, even when the power is turned on,
Click noise will not be output to the audio output even when it is OFF.

As mentioned above, according to the present invention, by adding only one diode, the power can be turned on and off.
Therefore, a sound canceling circuit is obtained which is simple in circuit, reliable in operation, and moreover is very economical.

[Brief explanation of the drawing]

FIG. 1 shows a circuit diagram of an embodiment of the present invention, and FIG. 2 shows an explanatory diagram of its operation. The symbols used in the drawings indicate the following. 1...Remote control signal input section, 2...Power ON/OFF control output terminal, 3...
D/A converter pulse train output terminal, 4...Bias current limiting resistor, 5, 12...Transistor, 6
...Relay coil, 7...Relay contact, 8...
D/A converter, 9...Integrator circuit resistance, 10...
... Integrating circuit capacitor, 11... Connection point between 9 and 10, 13... Volume control section, 14... Diode.

Claims (1)

[Scope of utility model registration request] In a system where the power can be turned on and off and the volume can be turned up and down by command signals from a remote control transmitter, the receiver of the controlled device has an ON and OFF control output and a voice control output, and is capable of voice control. In devices whose output is connected to the volume control section via a D/A converter and an integrating circuit, the charge in the capacitor forming the integrating circuit is discharged between the ON/OFF control output terminal and the terminal of the integrating circuit. A sound cancellation circuit for a remote control, characterized in that a diode is connected in the direction in which the signal is received.