Inductor Current Reconstruction Circuit for Power Converter Protection
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Solution Overview
Problem
In power converters, direct detection of inductor current is often impractical due to space and integration limitations, leading to potential damage from excessive current flow during short-circuit conditions, necessitating real-time detection methods that can reconstruct inductor current from switching cycle information.
Innovation Solution
The inductor current reconstruction circuit employs a switching current sampling circuit and inductor current generation circuit to generate a reconstruction signal by tracking the current through main and rectifier transistors, using voltage-controlled voltage sources and error amplification to adjust and compensate for inductor current changes, allowing for indirect detection of inductor current across the complete switching cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct detection of inductor current is implemented, then real-time current monitoring is achieved, but space requirements and integration complexity increase
Solution Approach 1:
The patent creates a copy of the inductor current waveform through circuit simulation rather than direct measurement. The switching current sampling circuit captures representative current samples during switching transitions, and the generation circuit reconstructs the complete inductor current waveform by combining these samples with voltage information, effectively copying the original current profile without direct sensing
Solution Approach 2:
The patent introduces intermediary signals (switching current sampling signals and inductor voltage signals) that serve as mediators to indirectly obtain inductor current information. Instead of directly measuring the inductor current, the system uses these intermediary measurements combined with circuit relationships to derive the desired current waveform, reducing direct detection complexity
2Reliability
If inductor current is not monitored, then circuit simplicity is maintained, but transistor damage risk increases during short-circuit conditions
Solution Approach 1:
The patent performs preliminary action by detecting switching currents and storing sampling values before potential short-circuit damage can occur. The switching current sampling circuit continuously captures current information during normal operation, preparing the data needed for rapid fault detection and protection activation without waiting for actual fault conditions
Solution Approach 2:
The patent implements feedback by using the reconstructed inductor current waveform to provide real-time monitoring information to the control system. This feedback mechanism enables the system to detect abnormal current conditions and activate protection mechanisms, creating a closed-loop protection system that prevents transistor damage while maintaining reasonable circuit complexity
3Loss of information
If complete switching cycle current detection is implemented, then full current waveform information is obtained, but detection difficulty and circuit complexity increase
Solution Approach 1:
The patent applies segmentation by dividing the inductor current detection task into separate sampling phases corresponding to different switching intervals. The switching current sampling circuit captures current information during specific switching transitions (e.g., when main switch turns on or off), breaking down the continuous detection problem into discrete, manageable sampling events that are easier to implement
Solution Approach 2:
The patent uses periodic action by sampling the switching current at regular intervals corresponding to the switching cycle frequency. The sampling occurs periodically at key switching events, and the generation circuit reconstructs the complete waveform by interpolating between these periodic samples, obtaining full cycle information through periodic measurement rather than continuous detection
Data Source
AI summary
A method of inductor current reconstruction for a power converter can include: acquiring at least one of a current that represents a current flowing through a main power transistor, and a current that represents a current flowing through a rectifier transistor, in order to generate a switching current sampling signal in the power converter; and generating an inductor current reconstruction signal representing an inductor current in one complete switching cycle according to the switching current sampling signal and an inductor voltage signal representing a voltage across an inductor in the power converter.