JPH0115212B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a volume adjustment device that can be used in television receivers and the like.

Configuration of Conventional Example and Its Problems FIG. 1 is a circuit diagram of a conventional volume adjusting device. A pulse generation circuit 1 is provided which can change the duty of the output pulse according to a received remote control signal, and the output pulse of the pulse generation circuit 1 is converted into an analog signal by a D-A converter 2, and the volume is adjusted. It is applied to adjustment volume 3. This volume adjustment volume 3 is used for auxiliary volume adjustment, and is usually used to set the maximum volume to be adjusted by remote control. The control voltage output from the variable terminal of the volume adjustment volume 3 is applied to the control terminal of the voltage-controlled variable gain amplifier 13 for audio amplification, and the volume is adjusted by controlling the gain. The volume can be adjusted by setting the volume adjustment volume 3 at a suitable location and changing the duty of the output pulses from the pulse generation circuit 1 using remote control. Now, with this circuit, if the remote control signal transmitter is lost or damaged while the duty of the output pulse of the pulse generation circuit 1 is adjusted to a small state, the volume adjustment volume 3 is set to the maximum volume. However, there is a drawback that the volume cannot be increased.

OBJECTS OF THE INVENTION The present invention seeks to eliminate the above-mentioned drawbacks and to provide sufficient control of the volume using the volume control volume even if the remote control signal transmitter is lost or damaged.

Structure of the Invention The present invention controls a switching element to turn on and off for a certain period of time when the power is turned on, and sets the control terminal of the pulse generation circuit to a high or low level to temporarily increase the duty of the output pulse of the pulse generation circuit, thereby increasing the volume. This is to set the state.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 2, a pulse generating circuit 4 is provided which can change the duty of the output pulse according to a received remote control signal. As this pulse generating circuit 4a, a circuit as shown in FIG. 3 can be used. This circuit basically uses the circuit described in Japanese Patent Application Laid-Open No. 54-51365. The cascaded flip-flop group 4d creates a pulse group with different phases, and the gate group 4c selects a predetermined pulse from the pulse group based on the outputs A to E of the counter 4b and applies it to the flip-flop 4e. A pulse with a duty ratio corresponding to the outputs A to E of is created. D whose output is composed of an integrating circuit
-A converter 5 generates an analog volume control signal. The duty ratio of the output pulses of the pulse generating circuit 4 can be changed by applying a clock pulse to the counter 4b via the counters 4f and 4g to change the output of the counter 4b. Therefore, the counter 4b can be controlled remotely. Control the volume by controlling with a signal. By setting the voltage at the control terminal 4a of the pulse generating circuit 4 to a high or low level, the duty of the output pulse can be increased. Such a pulse generation circuit is integrated into an IC and is commonly used.
The output pulse of the pulse generating circuit 4 is converted into an analog signal by a DA converter 5 and applied to a volume adjustment volume 6.

On the other hand, a switch 9 that operates in conjunction with the power switch 7 is provided, and this switch 9 is turned on for a short time after the power switch 7 is turned on, and then turned off. A DC voltage from a rectifying and smoothing circuit 8 is applied to this switch 9, and current flows into a capacitor 11 when the switch 9 is turned on.
The voltage of this capacitor 11 is applied to the base of a transistor 10, which is a switching element. A resistor 12 constituting a discharge circuit is connected in parallel to the capacitor 11. Transistor 10 is connected between control terminal 4a and ground.

Now, assume that the power is turned off while the duty of the output pulse of the pulse generating circuit 4 is set to be small by remote control. Next, when the power switch 7 is turned on, the switch 9 is turned on for a short time, current flows into the capacitor 11, and the voltage of the capacitor 11 increases. As a result, the transistor 10 becomes conductive and the control terminal 4a becomes low level. Therefore, during the period when the duty of the output pulse of the pulse generating circuit 4 increases and the transistor 10 is conducting, the switch 9 is turned off and the electric charge of the capacitor 11 is discharged to the resistor 12. This is the short time it takes for the voltage to drop below a certain level. During this period, the output pulse duty is
Become 100%. As a result, the volume is set to the maximum level, and can be adjusted appropriately using the volume adjustment volume. It can also be adjusted by remote control. In the above embodiment, the duty of the output pulse increases when the control terminal 4a becomes low level, but in the case where the duty of the output pulse increases when the control terminal 4a becomes high level, the control is performed for a certain period of time after the power is turned on. terminal 4
It is sufficient to create a circuit in which the voltage of a is at a high level for a short period of time.

Effects of the Invention As described above, according to the present invention, the duty of the output pulse of the pulse generation circuit is increased once the power is turned on, so even if the remote control signal transmitter is lost or damaged, the volume adjustment volume can be adjusted even if the remote control signal transmitter is lost or damaged. You can freely adjust the volume.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional volume adjustment device, FIG. 2 is a circuit diagram of a volume adjustment device according to an embodiment of the present invention, and FIG. 3 is a circuit diagram of a specific example of a part of the circuit. 4... Pulse generation circuit, 5... D-A converter,
6...Volume adjustment volume, 4a...Control terminal, 1
0...Transistor, 11...Capacitor, 12
...Resistor, 9...Switch, 7...Power switch.

Claims (1)

[Claims] 1. The duty of the output pulse can be changed by the received remote control signal, and the duty of the output pulse can be increased by changing the voltage of the control terminal to a high level or a low level. A pulse generation circuit, a DA converter that converts the output of this pulse generation circuit into an analog signal, and a volume adjustment device that outputs a volume control signal from a variable terminal to which the analog signal of the output of this DA converter is applied. A volume adjusting device comprising a volume control device and a duty setting means for increasing the duty of the output pulse by setting a control terminal of the pulse generating circuit at a high level or a low level for a short time after turning on a power switch of a device such as a television receiver.