Circuit for thermal protection in audio power amplifier and method thereof

An audio amplifier comprising:

• a pre-amplifier, having an output terminal, receiving and amplifying an audio signal for generating an amplified a audio signal, wherein the preamplifier outputs the amplified audio signal from the output terminal;
• an output stage amplifier, having an input terminal, wherein the output stage amplifier is used for driving a load;
• a temperature detector, detecting the temperature of the output stage amplifier for outputting a temperature signal;
• and
• a gain adjusting circuit, for adjusting an amplitude of the amplified audio signal outputted from the pre-amplifier according to the temperature signal, wherein the gain adjusting circuit comprises an attenuator,
• wherein the attenuator has an input terminal and an output terminal, the input terminal of the attenuator is coupled to the output terminal of the pre-amplifier and the output terminal of the attenuator is coupled to the input terminal of the output stage amplifier,
• wherein the input terminal of the attenuator receives the amplified audio signal from the output terminal of the pre-amplifier for adjusting the amplitude of the amplified audio signal according to the temperature signal outputted from the temperature detector and then the attenuator outputs the attenuated amplified audio signal to the input terminal of the output stage amplifier, wherein the higher the temperature is, the smaller an amplitude of the amplified audio signal is adjusted by the attenuator.

An integrated audio amplifier, comprising:

• a pre-amplifier, receiving and amplifying an audio signal for generating an amplified audio signal, wherein the pre-amplifier comprises a differential pair;
• an output stage amplifier, receiving the amplified audio signal and output to a load;
• a temperature detector, detecting the temperature of the output stage amplifier for outputting a temperature signal;
• and
• a gain adjusting circuit, for adjusting an amplitude of the amplified audio signal outputted from the pre-amplifier according to the temperature signal,
• wherein the pre-amplifier, the output stage amplifier, the temperature detector and the gain adjusting circuit are integrated into a same integrated circuit, wherein the gain adjusting circuit comprises an adjusting current source, coupled to the differential pair and the temperature detector, for adjusting the direct current bias supplied to the differential pair according to the temperature signal outputted from the temperature detector.

An integrated audio amplifier, comprising:

• a pre-amplifier, having an output terminal, receiving and amplifying an audio signal for generating an amplified audio signal, wherein the preamplifier outputs the amplified audio signal from the output terminal;
• an output stage amplifier, having an input terminal, wherein the output stage amplifier is used for driving a load;
• a temperature detector, detecting the temperature of the output stage amplifier for outputting a temperature signal;
• and
• a gain adjusting circuit, for adjusting an amplitude of the amplified audio signal outputted from the pre-amplifier according to the temperature signal, wherein the gain adjusting circuit comprises an attenuator,
• wherein the attenuator has an input terminal and an output terminal, the input terminal of the attenuator is coupled to the output terminal of the pre-amplifier and the output terminal of the attenuator is coupled to the input terminal of the output stage amplifier,
• wherein the input terminal of the attenuator receives the amplified audio signal from the output terminal of the pre-amplifier for adjusting the amplitude of the amplified audio signal according to the temperature signal outputted from the temperature detector and then the attenuator outputs the attenuated amplified audio signal to the input terminal of the output stage amplifier, where the higher the temperature is, the smaller an amplitude of the amplified audio signal is adjusted by the attenuator.