Battery Impedance Measurement Circuit With Orthogonal Phase References
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Solution Overview
Problem
Conventional techniques for measuring complex impedance of secondary batteries are prone to errors due to phase errors caused by the influence of electric wiring and require complex feedback control, making it difficult to achieve accurate measurements without increasing consumption current.
Innovation Solution
A battery management circuit that generates orthogonal reference frequency signals to measure complex voltage and current separately, converting these measurements into real and imaginary components to eliminate phase errors, thereby simplifying the circuit configuration and improving measurement accuracy without feedback control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional alternating-current superimposition method is used to measure complex impedance, then measurement can be performed, but phase errors occur due to electric wiring influence reducing measurement accuracy
Solution Approach 1:
The patent introduces an intermediary processing step: multiplying measured voltage and current by orthogonal reference signals (sine and cosine) to separate real and imaginary components. This mediator process eliminates phase errors caused by electric wiring, as the orthogonal multiplication inherently compensates for phase shifts. The result is accurate complex impedance measurement without requiring complex feedback control.
Solution Approach 2:
The patent changes the measurement approach by using frequency-domain analysis through orthogonal signal multiplication. Instead of directly measuring phase differences, the system transforms the problem into separating real and imaginary components through parameter multiplication with reference signals at the measurement frequency. This parameter transformation eliminates phase error accumulation.
2Measurement precision
If feedback control is implemented to eliminate phase errors, then measurement accuracy improves, but circuit complexity and control system complexity increase
Solution Approach 1:
The patent extracts the phase error component through orthogonal signal multiplication. By multiplying the measured signals with sine and cosine reference signals, the system separates the real and imaginary parts of the complex impedance, effectively taking out the phase information in a controlled manner. This eliminates the need for complex feedback control loops while maintaining measurement accuracy.
Solution Approach 2:
The patent replaces the mechanical feedback control system with a mathematical transformation approach. Instead of using active feedback control circuits to compensate for phase errors, the system uses orthogonal signal multiplication and integration to inherently eliminate phase errors. This substitution of mathematical processing for mechanical control simplifies the overall system architecture.
3Measurement precision
If feedback control is implemented to correct phase errors, then measurement accuracy improves, but consumption current increases
Solution Approach 1:
The patent implements a self-service measurement system where the orthogonal reference signals automatically compensate for phase errors without requiring external feedback control. The sine and cosine multiplication process inherently corrects phase shifts, and the integration over complete cycles self-averages out errors. This eliminates the need for additional active control circuits that would consume extra current.
Data Source
AI summary
A battery management circuit includes: a reference signal generator that generates a first reference frequency signal and a second reference frequency signal having a phase different from a phase of the first reference frequency signal; an alternating-current superimposer that superimposes an alternating current on the secondary battery, the alternating current having a frequency component of the first reference frequency signal; a voltage measurer that measures a voltage of the secondary battery by performing sampling using a frequency; a current measurer that measures a current of the secondary battery by performing sampling using a frequency; and a converter that converts each of results of measurements by the voltage measurer and the current measurer into a complex voltage and a complex current, by multiplying the result of the measurement by the first reference frequency signal and the second reference frequency signal.