Amplifier Auxiliary Path for Power Supply Noise Cancellation
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Solution Overview
Problem
Traditional amplifiers in personal audio devices suffer from poor power supply rejection ratio, leading to noise-induced current variations and a raised noise floor due to high-frequency noise mixing with out-of-band noise, which degrades the dynamic range of audio systems.
Innovation Solution
An amplifier design featuring a main signal path with feedback elements and an independent auxiliary path that generates a compensation current proportional to power supply noise to cancel noise-induced currents in the feedback elements, thereby improving power supply rejection ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional amplifier design with feedback elements is used, then the amplifier can provide stable gain and bandwidth, but power supply noise is rejected poorly leading to raised noise floor
Solution Approach 1:
The amplifier is divided into two independent signal paths: a main signal path for audio processing and an auxiliary path for power supply noise compensation. The auxiliary path separately processes power supply noise and generates compensation current, which is then injected into the main path to cancel noise-induced currents. This segmentation allows independent optimization of noise rejection without affecting audio signal processing.
Solution Approach 2:
An auxiliary compensation path acts as an intermediary between the power supply and the main signal path. This intermediate path detects power supply noise, processes it through a transconductance stage and feedback network, and generates compensation current that is injected into the main path to neutralize the harmful effects of power supply noise before it reaches the audio output.
2Stability of the object's composition
If feedback elements are used for stability, then gain stability is improved, but power supply-induced current variations are not adequately compensated
Solution Approach 1:
The auxiliary path implements a dedicated feedback mechanism that specifically targets power supply noise. A feedback network with capacitors and resistors monitors power supply voltage variations, and this information is fed back through a transconductance stage to generate compensation current that is injected into the main signal path, creating a negative feedback loop that actively cancels power supply-induced current variations.
Solution Approach 2:
The auxiliary compensation path performs preliminary anti-action by detecting and compensating for power supply noise before it can significantly degrade the audio output. The compensation current is generated and injected in advance to counteract the harmful effects of power supply variations, preventing rather than merely correcting the noise-induced current variations in the main amplifier path.
Data Source
AI summary
An amplifier may include a main signal path having a plurality of stages compensated by feedback elements, the plurality of stages comprising an output stage configured to receive electrical energy from a power supply and an auxiliary path independent of the main signal path and comprising an output stage compensation circuit configured to generate a compensation current proportional to noise present in the power supply and apply the compensation current to cancel a power supply-induced current present in at least one of the feedback elements.