Power Supply Generator Switcher Noise Cancellation Feedback
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Solution Overview
Problem
Existing power supply generators for wireless devices face challenges in reducing noise, particularly switcher noise, which can lead to spurious emissions and degrade receiver performance, due to limited DC gain and bandwidth of envelope amplifiers.
Innovation Solution
A noise cancellation apparatus comprising a switcher, an envelope amplifier, and a feedback circuit, where the feedback circuit has a transfer function that attenuates switcher noise by providing a second version of the noise to cancel the first version at the load, using a combination of a coupling circuit and a summer to sum the signals effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a switcher is used to generate supply voltage efficiently, then power efficiency is improved, but switcher noise is introduced which degrades receiver performance
Solution Approach 1:
A feedback circuit acts as an intermediary to capture switcher noise at the switcher output and generate a compensating signal that cancels the noise at the load. The feedback circuit includes a summer that subtracts the noisy switcher output from the envelope signal, and an envelope amplifier that amplifies this difference signal to create a noise-canceling component.
Solution Approach 2:
The system uses feedback by monitoring the switcher output signal and using it to generate a compensating signal through the feedback circuit. The feedback loop captures the noise characteristics and uses them to create an opposing signal that eliminates the harmful noise at the load while preserving the efficient power conversion.
2Object-affected harmful factors
If envelope amplifier bandwidth is increased to reduce noise, then noise attenuation is improved, but device complexity and power consumption increase
Solution Approach 1:
The noise cancellation function is segmented into separate components: the feedback circuit with summer and envelope amplifier handles the noise cancellation, while the main power supply path remains unchanged. This segmentation allows the envelope amplifier to operate at lower bandwidth while still achieving effective noise attenuation through the dedicated feedback path.
3Object-affected harmful factors
If envelope amplifier DC gain is increased to reduce noise, then noise attenuation is improved, but device complexity and power consumption increase
Solution Approach 1:
The feedback circuit serves as an intermediary that processes the noise cancellation function separately from the main power supply path. This allows the envelope amplifier to use moderate DC gain while the feedback mechanism provides the additional noise attenuation needed, reducing overall power consumption compared to requiring extremely high DC gain in a single-stage amplifier.
Data Source
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AI summary
Techniques for performing noise cancellation/attenuation are disclosed. In one design, an apparatus includes a power supply generator having a switcher, a coupling circuit, an envelope amplifier, and a feedback circuit. The switcher generates DC and low frequency components and the envelope amplifier generates high frequency components of a supply voltage for a load, e.g., a power amplifier. The switcher receives a first supply voltage and provides a switcher output signal having switcher noise. The coupling circuit receives the switcher output signal and provides a first output signal having a first version of the switcher noise. The feedback circuit receives the switcher output signal and provides a feedback signal. The envelope amplifier receives an envelope signal and the feedback signal and provides a second output signal having a second version of the switcher noise, which is used to attenuate the first version of the switcher noise at the load.