Multi-Level Converter Current Sampling Without Inductor DCR Drift
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Solution Overview
Problem
Current methods for sampling inductor current in multi-level converters suffer from inaccuracies due to variations in the DC resistance of the inductor, which are affected by temperature, manufacturing process, and frequency, leading to significant deviations and requiring additional passive devices.
Innovation Solution
A current sampling circuit that utilizes operational amplifiers and current mirrors to sample the inductor current by combining the signals from power switches Q1 and Q2, allowing for accurate characterization of inductor current through capacitors or resistors, independent of inductor resistance variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the DC resistance of the inductor is used to sample the inductor current, then the current sampling can be achieved, but the sampling accuracy deteriorates due to resistance variations caused by temperature, manufacturing process, and frequency changes
Solution Approach 1:
The patent introduces an operational amplifier as an intermediary device between the inductor and the sampling circuit. The operational amplifier buffers the inductor current sampling, eliminating the direct dependence on inductor DC resistance. This mediator isolates the measurement system from the variable resistance, maintaining sampling accuracy despite temperature and frequency variations.
Solution Approach 2:
The patent replaces the traditional passive resistor-based current sampling method with an active operational amplifier-based circuit. This substitution transforms the sampling mechanism from a purely passive resistance-dependent system to an active system that can compensate for resistance variations, thereby improving measurement precision.
2Measurement precision
If traditional current sampling methods are used, then the inductor current can be sampled, but additional passive devices are required which increases device complexity
Solution Approach 1:
The operational amplifier in the patent serves multiple functions simultaneously: it acts as a buffer for current sampling, provides impedance matching, and enables accurate current measurement without requiring additional passive components. This multi-functionality reduces the overall device complexity while maintaining or improving sampling accuracy.
Solution Approach 2:
The patent combines the current sampling function with the operational amplifier's inherent buffering and impedance transformation capabilities. By merging these functions into a single integrated circuit solution, the design eliminates the need for separate passive devices that would otherwise be required in traditional sampling circuits.
Data Source
AI summary
A current sampling circuit for a multi-level DC-DC converter having first and second power switches connected in series, and a first inductor having one terminal coupled to a common node of the first and second power switches, where the current sampling circuit is configured to: receive a first signal representing a current flowing through the first power switch; receive a second signal representing a current flowing through the second power switch; and generate a third signal representing an inductor current flowing through the first inductor according to the first signal and the second signal.