Interleaved Power Stage PWM Control for Rail Current Balancing
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Solution Overview
Problem
Multi-rail power supplies face challenges in achieving current balance between rails due to external component mismatches, leading to unequal power dissipation and reduced efficiency, despite phase-shifted PWM control signals.
Innovation Solution
A control driver circuit generates distinct PWM control signals for each power converter based on the average of the rail currents, using a compensator control signal and a modified compensator control signal to adjust the duty cycle and balance rail currents, eliminating the need for prior identification of imbalanced rails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common control signal is delivered to multiple phase-shifted PWM drivers, then the control scheme is simple and easy to implement, but current imbalance between rails occurs due to component mismatches
Solution Approach 1:
The patent divides the control system into separate PWM drivers for each rail, with each driver having its own oscillator and control logic. This segmentation allows independent adjustment of each rail's duty cycle to compensate for component mismatches, thereby achieving current balance while maintaining relatively simple individual driver designs
Solution Approach 2:
The patent applies local quality by allowing each PWM driver to have customized duty cycle adjustments based on its specific rail's component characteristics. Each driver can independently modify its pulse width to compensate for local variations in switch driver propagation delays, DC resistances, and forward voltage drops, achieving precise current balance for each rail
2Ease of operation
If equal duty cycles are used for all rails, then the control signals are uniform and simple, but current imbalance persists due to external component variations
Solution Approach 1:
The patent changes the duty cycle parameter for each PWM driver based on measured or calculated compensation values. Each driver adjusts its specific duty cycle parameter to account for component mismatches, transforming the uniform duty cycle approach into a customized parameter set that achieves current balance while maintaining operational simplicity
3Loss of energy
If current imbalance occurs between rails, then unequal power dissipation results, but thermal management becomes more difficult and efficiency reduces
Solution Approach 1:
The patent implements feedback mechanisms where each PWM driver monitors its rail's current or power dissipation and adjusts its duty cycle accordingly. This feedback loop ensures that power dissipation is balanced across all rails, preventing overheating in any single rail and maintaining optimal efficiency by continuously adapting to component variations and load conditions
Data Source
AI summary
A multi-rail power converter assembly includes first and second interleaved power converters configured to output first and second rail currents. A control driver circuit includes first and second control outputs configured to output first and second control signals configured to control power conversion in the first and second power converters to generate the first and second rail currents. A first PWM generator receives a compensator control signal and generates the first control signal based on the compensator control signal. A second PWM generator receives a first modified compensator control signal and generates the second control signal based on the first modified compensator control signal. The control driver circuit is configured to generate the first modified compensator control signal based on an average of the first rail current and the second rail current.