Boost Converter Current Limiting with Zero-Integral Average Control
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Solution Overview
Problem
Existing peak-current controlled boost converters face challenges in accurately controlling the average current due to errors from slope compensation, leading to sub-harmonic behavior and difficulties in determining proper peak current limitation, especially with inductor variation.
Innovation Solution
A method is introduced to monitor the current through a power inductor, control switching based on a comparison with a peak current signal, and determine when the mathematical integral of the difference between the monitored current and the desired average current is zero, allowing for precise average current limiting by modifying the peak current signal accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If slope compensation is applied in analog circuitry to avoid sub-harmonic behavior, then stability is improved, but measurement precision deteriorates due to unknown error introduced by the compensation
Solution Approach 1:
The patent separates the current control into two independent comparison circuits: one for peak current control with slope compensation and another for average current control without slope compensation. This segmentation allows each circuit to operate independently with its own compensation strategy, resolving the contradiction by enabling precise measurement in the average current circuit while maintaining stability in the peak current circuit.
Solution Approach 2:
The patent introduces an intermediary average current signal that is derived from the peak current signal but processed separately. This intermediary signal serves as a mediator that provides accurate average current information without being contaminated by slope compensation errors, allowing the system to maintain both stability and measurement precision.
2Stability of the object's composition
If peak current is controlled using slope-compensated target peak current signal, then sub-harmonic behavior is avoided, but average current control accuracy deteriorates due to error from slope compensation
Solution Approach 1:
The patent divides the control system into two separate control loops: a peak current control loop that uses slope-compensated target peak current signal for stability, and an average current control loop that uses an independently derived average current signal for accuracy. This segmentation allows each loop to optimize for its specific function without compromising the other.
Solution Approach 2:
The patent implements feedback mechanisms where the actual average current is continuously monitored and compared with the target average current. The error signal is used to adjust the control parameters, ensuring that the average current control accuracy is maintained despite the presence of slope compensation in the peak current control path.
3Reliability
If inductor current is limited below maximum threshold using separate comparator circuits, then current protection is improved, but device complexity increases due to additional control loops
Solution Approach 1:
The patent merges the functions of peak current control and average current control into a unified control architecture where both control loops share common components such as the current sensor, control processor, and output stage. This merging reduces device complexity while maintaining the reliability benefits of separate comparator circuits for current protection.
Solution Approach 2:
The patent designs the control system with multi-functional components that can serve multiple purposes. For example, the same current sensor is used by both the peak current comparator and the average current comparator, and the control processor handles both control loops. This universality reduces the overall device complexity while maintaining comprehensive current protection.
Data Source
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AI summary
A method may include monitoring a current through a power inductor of a boost converter and detecting when a mathematical integral of a difference between the current as monitored and a desired average current for the power inductor is equal to zero. Another method may include in a first mode of operation of a boost converter, controlling switching behavior of switches of the boost converter to regulate an output voltage generated by the boost converter and in a second mode of operation of the boost converter, controlling switching behavior of switches of the boost converter to regulate an input current received by the boost converter. Another method may include monitoring a current through a power inductor of a boost converter and detecting when the current as monitored exceeds a maximum current for the power inductor.