Interleaved PFC Control Device Phase Offset Stability
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Solution Overview
Problem
Existing power-factor-correction (PFC) regulators with interleaved converter stages face challenges in maintaining a desired phase offset and transition mode operation, leading to inefficiencies and electromagnetic interference, particularly due to variable switching frequencies and transients.
Innovation Solution
A control device that synchronizes all converter stages using a common synchronism signal based on the estimate of the switching period, ensuring a constant ON interval and generating PWM command signals to maintain a desired phase offset, thereby operating all stages in transition mode with minimal interleaving errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If variable switching frequency is used to adapt to changing operating conditions, then adaptability is improved, but phase offset stability deteriorates
Solution Approach 1:
The patent applies periodic action by using a phase-locked loop to generate synchronism signals at a fixed frequency that is a multiple of the line frequency. This periodic signaling structure ensures that despite variable switching frequencies caused by changing operating conditions, the converter stages maintain stable phase relationships through synchronized PWM command signals generated at regular intervals.
2Device complexity
If converter stages operate in discontinuous conduction mode, then device complexity is reduced, but electromagnetic interference increases
Solution Approach 1:
The patent employs feedback control through a phase-locked loop that continuously monitors the switching frequency and adjusts the PWM command signals accordingly. This feedback mechanism ensures that converter stages operate in transition mode (at the boundary between continuous and discontinuous conduction), thereby reducing electromagnetic interference while maintaining relatively simple control architecture.
3Adaptability or versatility
If natural-interleaving technique is used with both stages as master, then adaptability is improved, but transition mode operation cannot be guaranteed
Solution Approach 1:
The patent introduces a phase-locked loop as an intermediary control mechanism that mediates between the converter stages. This intermediary generates synchronized PWM command signals that ensure both stages operate in transition mode while maintaining adaptability to changing operating conditions, thus guaranteeing reliable operation without sacrificing flexibility.
4Stability of the object's composition
If cross-coupled master-slave relationship is used, then phase offset stability is improved, but adaptability to transients deteriorates
Solution Approach 1:
The patent applies dynamics by implementing a phase-locked loop with proportional-integral control that can dynamically adjust to changing operating conditions. The control system transitions between different operational states smoothly, maintaining phase offset stability through the locked-loop mechanism while simultaneously adapting to transients through the dynamic response characteristics of the proportional-integral controller.
Data Source
AI summary
A control device for a switching regulator having two or more converter stages operating with interleaved operation, each converter stage including an inductive element and a switch element, generates command signals having a switching period for controlling switching of the switch elements, and determining alternation of a storage phase of energy in the respective inductive element and a transfer phase of the stored energy onto an output element. The control device generates the command signals phase-offset by an appropriate fraction of the switching period to obtain interleaved operation. In particular, a synchronism stage generates a synchronism signal and a control stage generates the command signals for the converter stages timed by the same synchronism signal.