Digital Chopping Feedback Circuit for Current Sensor Ripple Error
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Solution Overview
Problem
Current sensors face challenges with high frequency chopper noise causing residual offsets and in-band noise, which reduces the dynamic range and increases the ratio of smallest to largest signal, due to chopping of input signals for reducing offset errors.
Innovation Solution
A system comprising a first circuit, a second circuit, and a feedback circuit, where the second circuit chops input signals and provides digital output signals, and the feedback circuit accumulates error signals to convert them into an analog signal to reduce ripple error, using a chopping circuit, integrator circuit, and digital to analog converter circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If chopping is applied to reduce offset errors, then offset accuracy is improved, but high frequency chopper noise is generated causing residual offsets and in-band noise
Solution Approach 1:
A feedback circuit is introduced that receives digital output signals, extracts chopper noise components, converts them to analog signals via DAC, and feeds them back to cancel the noise. The feedback signal is generated by processing the digital output signals through a noise extraction path that identifies and isolates chopper noise components, then reconstructs them as analog cancellation signals.
Solution Approach 2:
A digital-to-analog converter (DAC) is used as an intermediary to convert digital chopper noise components into analog signals that can be properly fed back to cancel the original chopper noise. The DAC serves as a bridge between the digital noise extraction stage and the analog feedback cancellation stage, enabling effective noise suppression.
2Object-generated harmful factors
If low-pass filtering is applied to filter chopper noise, then noise is reduced, but more area on the integrated circuit chip is consumed
Solution Approach 1:
Traditional analog low-pass filtering is replaced with a digital noise extraction and feedback cancellation approach. Instead of using large analog filters, the system uses digital signal processing to identify chopper noise components, converts them to analog via DAC, and feeds them back for cancellation. This substitution dramatically reduces the chip area required while maintaining effective noise suppression.
3Measurement precision
If analog feedback loops are used to reduce offset error, then offset accuracy is improved, but more area on the integrated circuit chip is consumed and low-pass filtering frequency is reduced
Solution Approach 1:
The feedback system is segmented into distinct functional paths: a forward path that processes input signals and generates digital output, and a separate feedback path that extracts chopper noise from the digital output, converts it to analog, and feeds it back for cancellation. This segmentation allows independent optimization of each path and reduces the area requirements compared to a monolithic analog feedback loop.
4Measurement precision
If chopping frequency is increased to reduce residual offset, then offset accuracy is improved, but high frequency chopper noise is generated that reduces dynamic range
Solution Approach 1:
The chopper noise that was previously considered a harmful byproduct of offset correction is converted into a useful signal for cancellation. The system extracts the chopper noise components from the digital output signals, processes them through a DAC to generate analog feedback signals, and uses these signals to actively cancel the original chopper noise. This transforms the harmful noise into a beneficial cancellation mechanism, allowing high chopping frequencies to be used for offset accuracy without sacrificing dynamic range.
Data Source
AI summary
A system including a first circuit, a second circuit, and a feedback circuit. The first circuit is configured to provide input signals. The second circuit is configured to receive the input signals and provide digital output signals that correspond to the input signals. The feedback circuit includes a chopping circuit, an integrator circuit, and a digital to analog converter circuit. The digital to analog converter circuit is configured to convert an error signal into an analog signal that is received by the second circuit to reduce ripple error.