Digital Stress Share Auto-Zero Scheme for Power Converters
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Master-less switch mode power converter systems face challenges in achieving stable control system performance and load regulation due to undesirable oscillatory interactions between outer current balancing and inner voltage loops, leading to poor static control system performance and load dependency.
Innovation Solution
Implementing a digital stress share (DSS) controller with an Auto-Zero integrator scheme that enables or disables the integral term based on a signal, allowing the majority of controllers to have the integral term enabled and the minority to have it disabled, which helps in achieving superior static stress share performance and preventing control system instabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a master-less stress share scheme is used to eliminate single points of failure, then system reliability is improved, but control system stability and static performance deteriorate due to oscillatory interactions between control loops
Solution Approach 1:
The patent applies local quality by differentiating the integral term behavior among controllers based on their stress share status. Specifically, the integrator is disabled in controllers that are not currently sharing stress, while enabled in controllers that are actively sharing stress. This localized control approach prevents oscillatory interactions while maintaining the master-less architecture's reliability benefits.
Solution Approach 2:
The patent implements dynamics by making the integrator state configurable and changeable based on real-time operational conditions. The integrator can be dynamically enabled or disabled depending on whether the controller is actively participating in stress sharing, allowing the system to adapt its control characteristics to current operating conditions and eliminate instabilities.
2Manufacturing precision
If the integrator is enabled in all controllers to maintain stress balance, then stress sharing performance is improved, but control system instabilities and oscillatory interactions increase
Solution Approach 1:
The patent resolves this contradiction by applying local quality to the integrator function - it is enabled only in controllers that are actively sharing stress rather than being uniformly enabled in all controllers. This selective approach maintains precise stress sharing where needed while preventing instabilities in controllers that would otherwise create oscillatory interactions.
3Reliability
If digital controllers share stress information in discrete fashion over a bus, then system reliability is improved by eliminating master-slave dependencies, but static control performance and load regulation deteriorate
Solution Approach 1:
The patent applies dynamics by making the integrator state configurable based on operational conditions rather than fixed. This allows the system to dynamically adjust its control characteristics to achieve both the reliability benefits of master-less operation and the static performance required for precise load regulation.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present application relates to power converters, particularly switch mode power converters sharing a load in which the converters are operated to share stresses between them. The application provides a controller (108) in which a stress share control loop (108a, 108b) is provided to ensure the associated converter is operating at an average stress. The stress share control loop has a proportional and an integral term in its feedback path. The integral term may be enabled or disabled. In use, the integral term is enabled in all but one controller.