Adaptive Nonlinear Observer for Boost PFC Inductor Current
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Solution Overview
Problem
Current methods for estimating inductor current in power factor correction converters, such as Hall effect sensors, resistive current sensors, and Current Transformers, face challenges like high cost, complexity, noise introduction, and stability issues, particularly in high-power applications and when multiple converters are interleaved.
Innovation Solution
An adaptive nonlinear observer circuit that estimates inductor current and output voltage using input and output voltages, with an adaptive updater that adjusts estimates based on output voltage error, effectively eliminating the need for current sensors and addressing non-observability at certain operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Hall effect sensors are used to measure inductor current, then current measurement is achieved, but the system complexity increases due to DC-bias correction algorithms and time delays affect stability
Solution Approach 1:
The patent extracts the current measurement function from physical sensors and implements it through a virtual sensor using an adaptive observer algorithm. The observer estimates inductor current by processing voltage measurements and system model information, eliminating the need for Hall effect sensors and their associated DC-bias correction algorithms, thus reducing control system complexity while maintaining measurement capability
Solution Approach 2:
The patent replaces the mechanical/electromagnetic Hall effect sensor with a computational approach using an adaptive observer. The observer uses voltage measurements and system dynamics models to estimate current, substituting physical sensing with mathematical modeling and signal processing, thereby eliminating hardware complexity and associated correction algorithms
2Measurement precision
If Current Transformers are used to sense inductor current, then current measurement is achieved, but voltage spikes increase across power semiconductors during switching transitions
Solution Approach 1:
The patent removes the Current Transformer from the circuit topology and replaces it with a virtual current sensor implemented through software algorithms. The adaptive observer estimates current by processing voltage measurements and system model information, eliminating the CT and its associated magnetizing inductance that causes voltage spikes during switching transitions
Solution Approach 2:
The patent creates a virtual copy of the current measurement function through the adaptive observer algorithm. Instead of using a physical CT to sense current, the observer computes an estimate of the inductor current by copying the electrical behavior through mathematical modeling, thereby achieving measurement without the harmful side effects of physical CTs
3Productivity
If multiple boost converters are interleaved to reduce input current ripple, then current sharing is achieved, but switching noise from one phase affects sampling of the next phase
Solution Approach 1:
The patent replaces physical current sensors with virtual sensors in the interleaved converter configuration. The adaptive observer algorithm processes voltage measurements to estimate current, eliminating the need for physical sensor isolation between phases. This computational approach avoids switching noise interference while maintaining accurate current estimation for proper phase current sharing and ripple reduction
Data Source
AI summary
Systems, methods, and devices which estimate the inductor current in a power factor correction (PFC) converter for use with AC/DC converters. A control system for use with the PFC takes as input the input voltage and the output voltage of the PFC. Control signals for power semiconductor subcircuits in the PFC are then output from the control system. The control system uses an adaptive observer sub-circuit that estimates the inductor current and the bus voltage. The adaptive observer uses an adaptive updater which uses both the estimates and the estimate error to update the adaptive observer's estimates.