Inductor Current Sensing With Tunable DCR Tracking in Power Converters
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Solution Overview
Problem
Power converter circuits, such as switch mode power supplies, face challenges in optimizing performance due to varying inductor properties, which can change with temperature and age, and often lack prior knowledge of these properties.
Innovation Solution
The implementation of a circuit with a current sensor, a tunable time constant circuit, and a DCR control circuit allows for the determination of inductor properties, such as time constant and DC resistance, enabling adaptive gain adjustments to maintain optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If inductor properties are assumed fixed based on specifications, then device complexity is reduced, but performance consistency deteriorates due to temperature and age variations
Solution Approach 1:
The patent implements feedback mechanisms where the controller continuously monitors inductor current and compares it with expected values based on commanded operations. When deviations are detected (indicating property changes due to temperature or age), the controller automatically adjusts operating parameters to compensate, maintaining performance consistency without requiring complex manual recalibration
Solution Approach 2:
The system performs self-characterization by autonomously determining inductor properties through controlled current application and measurement during normal operation. The controller applies test currents, measures the resulting voltage and current relationships, and automatically updates its internal model of the inductor properties without external intervention, enabling the system to adapt to aging and temperature effects
2Productivity
If inductor properties are measured continuously, then performance optimization is improved, but device complexity and measurement requirements worsen
Solution Approach 1:
Instead of continuous full-characterization measurements, the system performs partial measurements at strategic moments (during startup, mode transitions, or when performance degradation is detected). The controller applies simplified test sequences that measure only the critical parameters needed for current operating conditions, reducing measurement complexity while maintaining performance optimization
Solution Approach 2:
The existing current sense circuitry and control signals are used for multiple purposes: normal current control, inductor property measurement, and performance monitoring. The same voltage and current paths serve both operational and characterization functions, eliminating the need for separate dedicated measurement circuits and reducing overall device complexity
3Ease of operation
If inductor properties are characterized at startup only, then ease of operation is improved, but adaptability to temperature and age changes worsens
Solution Approach 1:
The system transitions from static initial characterization to dynamic continuous adaptation. The controller periodically updates inductor property estimates during operation based on real-time measurements and operational feedback. This dynamic approach allows the system to adapt to temperature drift and aging effects while maintaining ease of operation, as the adaptation occurs automatically without user intervention
Data Source
AI summary
A circuit includes a current sensor circuit having inputs and an output. The current sensor inputs are adapted to be coupled to inductor terminals a power converter. The current sensor circuit includes a tunable time constant circuit coupled between the current sensor inputs and the current sensor output. A time constant control circuit is coupled to a tunable time constant circuit, and is configured to tune the time constant circuit responsive to the current sensor output and another signal representative of inductor current. An adjustable gain circuit has a first input coupled to the current sensor output. A direct current resistance (DCR) control circuit has an output coupled to a second input of the adjustable gain circuit, and the DCR control circuit is configured to provide a gain adjust signal at the output thereof responsive to an average current of the inductor and a current command signal for the power converter.