Chopper Clock Management for Current and Voltage Sensor Spurs
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Solution Overview
Problem
Existing sensor systems in battery management face challenges in accurately sensing current and voltage due to the introduction of chop clock frequency tones, which intermodulate with in-band and out-of-band signals, leading to spurs that overwhelm the desired signal and limit performance.
Innovation Solution
A signal processing system with a chopper and low-pass filter, coupled with a chop management circuit that dynamically manages the energy and frequency of clock signals to filter out intermodulation products, thereby reducing the impact of aggressor tones and improving signal accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If chopping is used to minimize direct current offset, then offset reduction is achieved, but chop clock frequency tones are introduced that intermodulate with signals to create in-band spurs
Solution Approach 1:
The patent dynamically adjusts the chopping frequency based on the operational state of the power converter. When the power converter is active, the chopping frequency is set to avoid intermodulation with switching frequencies. When the power converter is inactive, chopping is disabled entirely. This dynamic adaptation resolves the contradiction by making the chopping frequency variable rather than fixed, allowing offset cancellation when needed while avoiding spur generation when power converter interference is present.
Solution Approach 2:
The patent changes the chopping frequency parameter based on the power converter's operational state. The control circuit monitors the power converter state and adjusts the chopping frequency accordingly - using higher frequencies when safe and lower or zero frequency when power converter interference is detected. This parameter change strategy allows the system to maintain measurement precision through chopping when beneficial while eliminating in-band spurs when the power converter is active.
2Measurement precision
If chopping frequency is increased to improve offset cancellation, then offset reduction improves, but intermodulation products fall within in-band frequency spectrum
Solution Approach 1:
The patent implements dynamic chopping frequency selection where the control circuit adjusts the chopping frequency based on real-time monitoring of the power converter state and signal characteristics. Instead of using a fixed high chopping frequency that causes intermodulation, the system adaptively selects the optimal frequency - using higher frequencies for better offset cancellation when the power converter is inactive, and lowering or disabling chopping when the power converter is active to prevent intermodulation products from falling in-band.
Solution Approach 2:
The control circuit employs feedback mechanisms to monitor the power converter operational state and adjust the chopping frequency accordingly. The system continuously observes whether the power converter is active or inactive and uses this feedback to dynamically modify the chopping frequency, ensuring that intermodulation products do not fall within the in-band frequency spectrum while maintaining effective offset cancellation when conditions permit.
3Device complexity
If fixed chopping frequency is used to simplify circuit design, then device complexity is reduced, but performance is limited by intermodulation with power converter switching frequencies
Solution Approach 1:
The patent transitions from a fixed chopping frequency approach to a dynamic frequency selection approach. The control circuit monitors the power converter state and adjusts the chopping frequency in real-time - using higher frequencies when the power converter is inactive for better offset cancellation, and lowering or disabling chopping when the power converter is active to avoid intermodulation. This dynamic approach maintains relatively simple circuit architecture while dramatically improving sensing accuracy by adapting to operational conditions.
Solution Approach 2:
The control circuit serves multiple functions: it monitors the power converter state, determines optimal chopping frequency, generates appropriate clock signals, and manages the overall sensing operation. By making the control circuit multi-functional, the patent avoids adding significant complexity while achieving dynamic frequency adaptation. The same control infrastructure that manages power converter operation is also used to optimize chopping frequency, thereby maintaining device simplicity while improving measurement precision.
Data Source
AI summary
A signal processing system may include a signal path and a chop management circuit. The signal path may comprise a chopper configured to chop a differential input signal to the signal path at a chopping frequency and a low-pass filter downstream of the chopper and configured to filter out intermodulation products of a direct current offset of the signal path and intermodulation products of an aggressor on the differential input signal in order to generate an output signal. The chop management circuit may be communicatively coupled to the chopper and configured to, based on operational parameters associated with the signal path, dynamically manage energy of one or more clock signals used to define the chopping frequency.