Protection arrangement for an audio output channel

Details Protection arrangement for an audio output channel Protection arrangement for an audio output channel

1991-05-13

1993-06-29

Isen, Forester W.

Electrical audio signal processing systems and devices

Audio transducer protection circuitry

330207P, 381120, H03G 1100

Patent

active

052241696

ABSTRACT:
A protection circuit for an audio output channel of a television receiver includes a detector which detects the presence of either or both of (1) a sustained DC component applied to the loudspeaker form the audio power amplifier, (2) and the loss of a supply voltage for the power amplifier. The presence of a of a sustained DC component can damage the loudspeaker. The loss of a supply voltage of the power amplifier can damage the power amplifier and can also result in the application of a sustained DC amplifier and can also result in the application of a sustained DC component to the loudspeaker. For example, the loss of the negative supply voltage of a power amplifier incorporated in an integrated circuit results in the removal of potential from the substrate which otherwise serves to electrically isolates various semiconductor devices supported by the substrate. The detector includes a low pass filter coupled between the output of the power amplifier and inputs of first and second comparators to detect when the output of the low pass filter is within or outside of a "window". A transistor switch is coupled to output of the comparators. As long as the output of the low pass filter is within the window, each comparator generates a respective low level output signal which keeps the transistor switch turned off. However, if the output signal of the lowpass filter is outside of the window, one of the comparators generates a high level output signal signal which causes the transistor switch to be turned on. The comparators normally receive the same supply voltages as the power amplifier, and the loss of the negative supply voltages does not enable either of the comparators to generates a low enough level output signal for keeping the transistor off.

REFERENCES:
patent: 3659218 (1972-04-01), Haneda
patent: 3691427 (1972-09-01), Honda et al.
patent: 3731153 (1973-05-01), Nishimoto
patent: 3996497 (1976-12-01), Kamimura
patent: 4010402 (1977-03-01), Miyata
patent: 4034268 (1977-07-01), Klauck
patent: 4042889 (1977-08-01), Baker
patent: 4296278 (1981-10-01), Cullison et al.
patent: 4330686 (1982-05-01), Roe
patent: 4402029 (1983-08-01), Fujita

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