Gm Global Technolgoy Operations, Inc.

Delco Electronics Corporation

David A LaRosa

David W Osburn

James R Knolinski

An audio amplifier of the type including circuitry to detect clipping and adjust the gain of an amplifier input element to control the clipping in closed loop operation further includes circuitry effective to sense the temperature of an amplifier component and change the amplifier bias voltage that determines the maximum non-clipping voltage so as to induce clipping in the amplifier when the temperature exceeds a predetermined temperature. The clipping control circuitry then reduces the input gain to the amplifier to control the clipping and, in so doing, reduces power dissipation to a level allowing the temperature to decrease to the predetermined temperature. The circuit provides for closed loop control of amplifier temperature in marginal temperature situations with minimal intrusion on the music reproduction process.

Power limiting audio amplifier temperature protection circuit

Conventional bridged amplifiers obtain output voltage range and DC operating voltage from full and half voltage outputs of a voltage divider. A low voltage unipolar supply powers the voltage divider for small signals. A peak detector selects the higher peak amplifier output; and a voltage follower with an output voltage range from a high voltage unipolar supply maintains an output voltage a predetermined level above the peak. The output of the follower controls a transistor connecting the high voltage supply to the full voltage output of the voltage divider to allow the bridged amplifier outputs to increase above the low voltage supply as necessary in class G operation. An input amplifier obtains output voltage range and DC operating level from the full and half voltage outputs of the voltage divider and has differential outputs connected in opposite phase to the inputs of the bridged amplifiers so that the DC operating level shifts with the output voltage range to maintain an undistorted output across the load in spite of clipped individual outputs due to the lack of oppositely poled supplies. The predetermined voltage is large enough to ensure that the transistor can provide sufficient current from the high voltage supply at high output levels in class G operation.

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Kokomo, IN, United States of America

David A LaRosa