Capacitor Voltage Ripple Current Sensing in Hybrid Converters
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Solution Overview
Problem
Existing current measurement schemes for DC-to-DC converters, such as resistive sensing, DCR, and SenseFETs, are lossy, require numerous external components, and struggle to maintain accuracy over wide current and temperature ranges, making them inefficient for hybrid capacitor/inductor converters.
Innovation Solution
A DC-to-DC power converter design that includes a ripple magnitude detector to measure the voltage change across an energy transfer capacitor, determining the current through an inductor, and a current sharing controller to adjust the output current of each phase in a multi-phase converter, ensuring accurate and efficient current sharing among phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resistive sensing is used for current measurement, then current can be measured, but energy loss increases and efficiency decreases
Solution Approach 1:
The patent uses voltage ripple across the energy transfer capacitor as an intermediary signal to indirectly measure inductor current. Instead of directly measuring current through resistive sensing, the ripple magnitude detector measures the voltage ripple caused by capacitor charging/discharging cycles, which correlates to the inductor current. This intermediary measurement approach eliminates the need for power-dissipating sense resistors while maintaining measurement capability.
2Measurement precision
If DCR current sensing is used, then current measurement is achieved, but numerous external components and temperature compensation are required
Solution Approach 1:
The patent extracts the current measurement information from the voltage ripple signal already present in the hybrid capacitor/inductor converter circuit. By taking out and analyzing the ripple magnitude across the energy transfer capacitor, the system obtains inductor current information without requiring external sense resistors, DCR measurement circuits, or temperature compensation components. The measurement is derived from existing circuit operation.
3Device complexity
If SenseFETs are used for current sensing, then integrated current measurement is achieved, but accuracy deteriorates under process variation and extreme conditions
Solution Approach 1:
The patent implements a self-service measurement approach where the energy transfer capacitor's own voltage ripple serves as the measurement signal. The ripple magnitude detector uses the capacitor's inherent charging and discharging behavior during normal converter operation to generate measurement information. This self-service mechanism eliminates dependence on external sense components or integrated SenseFETs that are susceptible to process variation, providing robust and accurate measurements across wide operating conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides a robust, lossless, and efficient method for current measurement and sharing, reducing the need for external components and maintaining accuracy across varying conditions, enhancing the performance of hybrid capacitor/inductor converters.
Implementation Method 1
detects a magnitude of a change in voltage across the energy transfer capacitor and determines an amount of current though the inductor based on the magnitude of the change in voltage across the energy transfer capacitor
Data Source
AI summary
A DC-to-DC power converter includes a power stage, an output stage and a ripple magnitude detector. The power stage includes a plurality of transistors, an energy transfer capacitor coupled between at least two of the transistors, and a switch node. The output stage includes an inductor coupled between switch node and a voltage output. The ripple magnitude detector detects a magnitude of a change in voltage across the energy transfer capacitor and determines an amount of current though the inductor based on the magnitude of the change in voltage across the energy transfer capacitor.