Full-Bridge AC-DC Converter Switching to Reduce Current Spikes
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Solution Overview
Problem
Current AC/DC converters with Bridgeless Totem-Pole PFC (BTP-PFC) configurations experience current spikes due to zero-voltage transitions, which introduce noise, electromagnetic interference, and reduce efficiency.
Innovation Solution
Implement a switched-mode AC-DC converter with a controller that alternates between different switching schemes, where pairs of switches operate at both line frequency and higher frequency, distributing switching roles evenly to minimize current spikes and heat loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If diodes and active switches are used separately optimized for different frequencies, then switching efficiency is improved, but current spikes occur at zero-voltage transitions
Solution Approach 1:
The patent merges the functions of diodes and active switches into a unified full-bridge configuration where all four switches are controlled by a single controller. This integration allows coordinated switching that eliminates current spikes while maintaining high-frequency switching efficiency, resolving the contradiction between switching efficiency and current spike generation.
Solution Approach 2:
The patent implements dynamic switching control where the controller alternates between different switching schemes based on operating conditions. The switching frequencies and patterns are dynamically adjusted to prevent current spikes at zero-voltage transitions while maintaining optimal efficiency, transforming static separate optimizations into dynamic coordinated control.
2Productivity
If one pair of switches operates at higher frequency while the other remains fixed, then power factor correction is improved, but heat and wear are concentrated on specific switches
Solution Approach 1:
The patent implements periodic alternation between different switching schemes where the roles of switch pairs are exchanged. During one half-cycle, the first pair switches at high frequency while the second pair is fixed; during the next half-cycle, this is reversed. This periodic role exchange distributes heat and wear evenly across all switches while maintaining continuous power factor correction performance.
Solution Approach 2:
The patent allows switches to temporarily assume fixed states while other switches perform high-frequency switching, then reverses this arrangement in subsequent cycles. This temporal distribution of switching stress allows each switch to recover during periods when it is in a fixed state, extending overall system reliability while maintaining productivity.
3Object-generated harmful factors
If switches are alternated between fixed and switched states at line frequency, then current spikes are reduced, but control complexity increases
Solution Approach 1:
The patent employs a single controller that performs multiple functions: generating high-frequency switching signals, coordinating alternating switching schemes, and managing the temporal distribution of switching roles. This multi-functional controller consolidates what would otherwise require separate control circuits, reducing overall system complexity while achieving current spike reduction through coordinated switching.
Data Source
AI summary
A switched-mode AC-DC converter includes (i) first and second pairs of switches connected in a full bridge configuration between AC terminals and DC terminals and (ii) a controller configured to control the switches according to a first switching scheme in which the controller alternates between: a first period in which the first pair of switches is in a first fixed state and the second pair of switches is switched on and off at a higher frequency fHIGH; and a second period in which the first pair of switches is switched on and off at the higher frequency and the second pair of switches is in a second fixed state, where the controller alternates between the first and second period at a line frequency fAC of an AC signal at the AC terminals.