JPH0314814Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a control circuit that increases or decreases the volume by controlling the pulse width, for example.

[Prior Art] FIG. 2 is a diagram showing a conventional volume control circuit. In the figure, numeral 1 denotes a volume control processor, which has key input terminals 2, 3, 4 and an output terminal 5. The output terminal 5 is connected to the base of a transistor 7 via a resistor 6, and the collector of the transistor 7 is connected to a power supply terminal 9 via a resistor 8 and to a resistor 10.
are respectively connected to the capacitor 11 via. Capacitor 11 is connected to capacitor 13 and the base of transistor 14 via resistor 12. The emitter of transistor 14 is connected to a control input terminal 18 of volume circuit 15. 1
6 is a controlled audio input terminal, and 17 is an audio output terminal.

Next, the operation will be explained. Input terminal 2 is a key for increasing volume, 3 is a key for decreasing volume, and 4 is a key for muting. Now, when an input is made from each key 2, 3, 4, the volume control processor 1 performs pulse width control and outputs a voltage with pulse width increasing, decreasing, or single high to the output terminal 5 according to each key input. Output. The output voltage of the output terminal 5 is the transistor 7
The voltage is inverted by the resistor 10 and the capacitor 11, and becomes a DC voltage according to the pulse width. Since the output voltage of the capacitor 11 includes an alternating current component, it is further smoothed through a smoothing circuit including a resistor 12 and a capacitor 13, and then applied to the base of the transistor 14. The volume circuit 15 attenuates the audio input voltage from the terminal 16 according to the DC voltage applied to the control input terminal 18 and outputs it to the audio output terminal 17 .

[Problems to be solved by the invention] The conventional volume control circuit is configured as described above, but when the sound is muted, the output of the volume control processor 1 immediately goes to a high potential, and the collector of the transistor 7 continuously goes to a low potential. Even when it comes to potential, the resistor 10, the resistor 12,
Since the time constant of the smoothing circuit constituted by the capacitors 11 and 13 is large, the transistor 14 does not immediately perform an inverting operation, and the voltage at the control input terminal 18 falls slowly.
There was a drawback that the mute operation was not performed immediately after the mute key was input.

This invention was made to eliminate the above-mentioned drawbacks of the conventional method, and when the mute key is input,
The purpose of the present invention is to provide a volume control circuit that can immediately perform operations such as muting the sound.

[Means for Solving the Problems] This invention is characterized by having a series circuit of diodes whose anodes are connected, which are connected in parallel to a resistor constituting a smoothing circuit.

[Function] The series circuit of diodes in this invention is provided at the subsequent stage of the smoothing circuit because when a silencing signal is input from the processor, the charge in the capacitor of the smoothing circuit is immediately discharged through the series circuit of diodes. The control input voltage input to the volume circuit changes abruptly, thereby immediately performing the muffling operation.

[Example] Hereinafter, an example of this invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of a volume control circuit which is an embodiment of this invention. In the figure, the same parts as in FIG. 2 are given the same reference numerals, and their explanation will be omitted. The difference between FIG. 1 and FIG. 2 is that a series circuit of a constant voltage diode 19 and a diode 20 is connected to both ends of the resistor 12. Constant voltage diode 1
The cathode of the diode 9 is connected to the capacitor 13, the anode of the diode 20 is connected to the anode of the diode 20, and the cathode of the diode 20 is connected to the capacitor 11.

In the above configuration, if the conduction voltage of the voltage regulator diode 19 is selected to be higher than the voltage generated across the resistor 12 when the volume normally decreases, the voltage regulator diode 19 and the diode 20 will not conduct when the volume normally decreases. , does not affect operation. Furthermore, when the volume is increased, the output of the output terminal 5 is at a low potential and the transistor 7 is off, so the voltage on the cathode side of the diode 20 is higher than that on the anode side, and the constant voltage diode 19 and the diode 20 become conductive as described above. No, it does not affect operation.

On the other hand, when the mute key is input to the terminal 4, the output terminal 5 of the volume control processor 1 becomes a high potential, turning on the transistor 7 and grounding its collector. In this state, the potential difference generated across the resistor 12 is sufficient to make the voltage regulator diode 19 conductive, so the voltage regulator diode 19 becomes conductive. and is immediately discharged through the series circuit of the diode 20. As a result, the transistor 14 is abruptly turned off, the control input terminal 18 is brought to a low potential, and the volume circuit 15 quickly mutes the sound.

In the above embodiment, a constant voltage diode is used in the series circuit of diodes, but by appropriately selecting the potential relationship during steady state, it is also possible to replace it with a normal diode connected in the conduction direction.

Further, in the above embodiments, volume control has been described, but this invention can also be applied to, for example, video and color gain control.

[Effects of the invention] As described above, according to this invention, a control circuit with high operating speed for noise reduction, etc. can be obtained by simply adding a simple circuit.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a volume control circuit according to an embodiment of this invention, and FIG. 2 is a circuit diagram showing a conventional volume control circuit. 1... Volume control processor, 2, 3, 4... Key input terminal, 10, 12... Resistor, 11, 13...
... Capacitor, 15 ... Volume circuit, 19 ... Constant voltage diode, 20 ... Diode. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] A processor that outputs a pulse signal that expresses the output level of a controlled signal such as a volume as a change in duty ratio, and at least a resistor that integrates this pulse signal and converts it into a DC voltage signal according to the duty ratio of the pulse signal. In a control circuit for volume, etc., comprising a smoothing circuit including a series body with a capacitor, and an output level control circuit that controls the output level of the controlled signal according to the voltage value of the DC voltage signal, the smoothing circuit comprises: 1. A control circuit for controlling volume, etc., comprising a series circuit of diodes in which the anodes of first and second diodes are connected to each other in parallel to a resistor.