DC-DC Inductor Current Estimation Without High-Speed ADCs
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Solution Overview
Problem
Existing methods for measuring inductor current in DC-DC switching power supplies are not suitable for integration with digital controllers due to size, cost, and efficiency issues, and observer-based methods have limited accuracy and require high-speed ADCs, which are impractical for high-frequency applications.
Innovation Solution
An inductor current estimation method using a voltage sampling module, data conversion, switching signal counting, inductor voltage calculation, and digital filtering to estimate inductor current based on input and output voltages without additional analog circuits or high-speed ADCs, employing a digital filter to calculate average and ripple values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage drop-based measurement method is used, then inductor current can be measured, but converter efficiency is reduced or high-bandwidth amplifier is required
Solution Approach 1:
The patent uses the inductor voltage as an intermediary to indirectly obtain inductor current information through digital calculation, rather than directly measuring current through voltage drop. This mediator approach allows current estimation without inserting sensing components that cause energy loss.
Solution Approach 2:
The patent replaces the traditional analog voltage drop measurement method with a digital calculation method. Instead of using physical sensing components and analog circuits, the system uses digital processing of inductor voltage to estimate current, eliminating the energy loss associated with physical current sensing.
2Extent of automation
If observer-based measurement method is used, then inductor current can be estimated, but accuracy is limited and high-speed ADC is required
Solution Approach 1:
The patent implements a feedback mechanism where the estimated inductor current is continuously calculated and fed back to the control system. This feedback loop uses the relationship between inductor voltage and current, combined with duty cycle information, to provide accurate real-time current estimation without requiring external high-speed ADCs.
3Measurement precision
If high-speed ADC and high-bandwidth sensor are used, then inductor current can be sampled accurately, but circuit size and cost increase
Solution Approach 1:
The patent creates a digital copy or model of the inductor current by calculating it from measured inductor voltage and duty cycle parameters. Instead of directly copying the actual current signal through physical sensors and high-speed ADCs, the system generates an equivalent digital representation through mathematical relationships, significantly reducing hardware requirements.
4Loss of information
If voltage drop-based measurement is used, then inductor current information can be obtained, but additional sensing circuit and controller implementation becomes complex
Solution Approach 1:
The patent makes the inductor voltage measurement serve multiple functions: it is used both for normal operation monitoring and for estimating inductor current. This multi-functional approach eliminates the need for separate current sensing circuits and simplifies the controller implementation, as the same voltage measurement infrastructure serves dual purposes.
Data Source
AI summary
An inductor current estimation method for a DC-DC switching power supply using a voltage sampling module, a data conversion module, a switching signal counting module, an inductor voltage calculation module and a digital filter module, comprising: processing an input voltage and an output voltage by the voltage sampling module and the data conversion module to obtain a converted input voltage and a converted output voltage which have a same number of bits; comparing a node voltage with a reference voltage, and then obtaining a duty cycle by the switching signal counting module; and then, outputting an average voltage of two terminals of an inductor and a parasitic resistor by the inductor voltage calculation module, and finally, obtaining an estimated inductor current by the digital filter module.