Electrical audio signal processing systems and devices – Including amplitude or volume control – Automatic
Patent
1997-08-22
1999-05-18
Chang, Vivian
Electrical audio signal processing systems and devices
Including amplitude or volume control
Automatic
381107, 330284, H03G3/00
Patent
active
059058021
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention concerns electronic devices which have an audio output, and more particularly, television receivers.
BACKGROUND
The sound output level from a television receiver can vary with changes of channel and/or program. Such a situation is considered by many users to be disturbing, and sometimes readjustment of the volume control is desired. For such situations, an automatic sound level control can enhance user comfort.
Accordingly, it is desirable to provide apparatus for the automatic control of sound level when there is a variation in the sound output level between channels and/or programs.
SUMMARY OF THE INVENTION
The present invention provides a dual action ability for automatically controlling sound level. Sudden peak signal levels are controlled with a fast time constant of response, and changes in the overall sound level are controlled with a slower time constant of response. A further feature of the invention allows that the automatic control of sound level can be enabled or disabled via a microprocessor, for example, responsive to a remote control.
BRIEF DESCRIPTION OF THE DRAWING
The sole FIGURE shows a schematic diagram of an automatic sound level controller according to aspects of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the FIGURE, there is shown an exemplary stereophonic audio output stage for a television receiver or the like. Since the "right" and "left" channels are identical, only the "right" channel will be described in detail. A right stereo signal 10R is coupled to stereo audio amplifier 12R at input terminal 14R through capacitor 13R and resistance 15R. Resistance 15R can be a physical resistor or equivalent circuit impedance. Stereo signal 10R has been previously processed by operational controls, e.g., volume, bass and treble. The amplified stereo signal at output 16R is coupled to stereo loudspeaker 18R.
The stereo output signals provided to loudspeakers 18R and 18L are coupled via summing resistors 20R and 20L to the base electrode of transistor 22, which is an emitter follower amplifier and serves as a buffer. The signal at the emitter electrode of transistor 22, is coupled through resistor 24 to the base electrode of transistor 26, with the amplified summed signals being provided at the collector electrode.
Transistor 26 is normally conducting due to the bias voltage applied to the base electrode by voltage divider 28, 30 connected between the supply voltage +V and a reference potential, e.g., ground. The collector of transistor 26 is also coupled to supply voltage +V via a load resistor 32. When transistor 26 is "on" (conducting), the collector electrode voltage is about 100 mV and diode 34 is not conducting, so that any charge on capacitor 36 discharges via resistor 38.
The audio signals provided to loudspeakers 18R and 18L are AC signals with positive and negative amplitudes. The positive part of the summed signal has no effect on transistor 26, because it would act to make transistor 26 conductive and it is already conducting. However, negative peaks of sufficient amplitude drive transistor 26 "off" and cause capacitor 36 to charge with a fast charging time constant via resistor 32 and diode 34 from the supply voltage +V. The charge on capacitor 36 is a control signal for controlling the resistance value of an attenuator portion 40, which is the lower portion of an AC voltage divider including resistors 15R and 15L, and coupling capacitors 54R and 54L.
In the exemplary embodiment, attenuator portion 40 is a CD4016 made by Harris Semiconductor Corporation of the United States, which are identified as integrated circuit quad bilateral "switches", each switch comprising a complementary pair of FET transistors. As the control voltage varies from 2 to 18 volts, the "on" resistance of each "switch" is continuously variable between the values of 3k ohms to 140 ohms. In the exemplary embodiment, two "switches" are connected in parallel for each channel, and all control gates 42 are connecte
REFERENCES:
patent: 3790896 (1974-02-01), Shimizu et al.
patent: 4115741 (1978-09-01), Skutta
patent: 4771472 (1988-09-01), Williams, III et al.
*Patent Abstracts Of Japan, vol. 006, No. 160, Aug. 21, 1992 & Japanese 57-079722, Matsushita Electric Ind. Co. Ltd. May 1982.
Chang Vivian
RCA Thomson Licensing Corporation
Tripoli Joseph S.
Wein Frederick A.
LandOfFree
Dual action automatic sound level control does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Dual action automatic sound level control, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dual action automatic sound level control will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1766487