Matsushita Electric Industrial Co., Ltd.

Panasonic Semiconductor Asia Pte. Ltd.

Yasuo Higuchi

Shiah Siew Wong

Chew Yuan Woong

An amplifier circuit that uses multiple power supplies includes a class D amplifier circuit, input bias generator and feedback network. By creating a voltage using the input bias generator at the non inverting terminal of the integrator, the inverting terminal of the integrator will follow the same voltage as the non inverting terminal. The offset voltage between the input signal DC bias and the input DC bias of the integrator will create an offset current flowing through the feedback resistors, thus resulting in the desired output DC bias.

Amplifier circuit with multiple power supplies

A output offset protection circuit provides protection of the load and the power amplifier through monitoring the temperature of the power transistor in the operational amplifier to detect fault conditions of an output block. In the output offset protection circuit, a sensor block monitors the temperature differences between the power transistors, while the output block is driving the load. Upon detection of the temperature differences reaching a 1st threshold level, the cutoff block sends a cutoff signal to a protection switch block, and the hysteresis block is activated. The hysteresis block shifts the threshold level lower to the 2nd threshold level. The sensor block continues to monitor the temperature differences until the 2nd threshold level is reached. Then the cutoff block is deactivated.

Output offset protection for power amplifier

A voltage level detector () which activates itself by monitoring the voltage level (V) at a standby pin () during power-up of an audio power amplifier (), and can detect fault conditions of an output block (), such as a short to ground at an output terminal (), in contrast to conventional protection circuits that can operate only after power-up.

Voltage level detector for power amplifier protection control

A voltage level detector () activates itself through monitoring the voltage level (VSTB) at a standby pin () during power-up of an audio power amplifier (), and can detect fault conditions of an output block (). Upon detection of the (VSTB) reaching a first threshold level (Vth) and a short to ground at the output terminal (), the second short-to-ground detection block () activates a the second cutoff signal generating block (). The recovery block () monitors the voltage level (VSTB) at the standby pin () during power-up. Upon detection of the voltage level (VSTB) reaching a second threshold level (Vth&#x3e;Vth), the recovery block () deactivates the cutoff signal generating block (). The cutoff signal generating block () sends a cutoff signal (Sc) to a protection switch block () as a request for turn-off of protection switches (A) on activation, and on the other hand, terminal the sending of the cutoff signal (Sc) on deactivation.

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Yasuo Higuchi