Bridgeless Flyback Converter Switching Loss Reduction
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Solution Overview
Problem
High switching loss and electromagnetic interference (EMI) noise in AC-DC power supply devices due to the inefficiencies and increased costs associated with bridgeless boost PFC converters and two-stage configurations, particularly in high-capacity applications.
Innovation Solution
A power supply device with a transformer unit, main and auxiliary switch units, and auxiliary inductor units that allow for zero voltage switching by transferring surplus power to the ground before switching, reducing switching loss and EMI noise through a single-stage isolated flyback converter configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a bridgeless boost PFC converter is used to reduce costs and increase efficiency, then conduction loss is reduced, but conducted common mode EMI noise level increases due to high input ripple current and switching of PFC switch parasitic capacitance
Solution Approach 1:
The patent divides the single PFC switch into two separate switches (first and second main switches) operating in parallel with 180-degree phase difference. This segmentation reduces the current ripple and switching frequency of each individual switch, thereby reducing the conducted common mode EMI noise while maintaining the cost benefits of the bridgeless configuration.
2Reliability
If a two-stage configuration is used to implement isolated AC-DC power supply, then isolation is achieved, but costs and power loss increase due to the two-stage structure
Solution Approach 1:
The patent combines the PFC function and isolation function into a single integrated stage. The two parallel flyback converters perform both power factor correction and voltage isolation simultaneously, eliminating the need for a separate PFC stage and reducing overall power loss while maintaining isolation.
3Loss of energy
If auxiliary switches are turned on before main switches to transfer surplus power to ground, then switching loss of main switches is reduced, but additional switching operations increase overall complexity
Solution Approach 1:
The auxiliary switches are turned on before the main switches to pre-transfer surplus power to the ground, creating zero-voltage switching conditions for the main switches. This preliminary action reduces switching loss of the main switches while the control complexity is managed through coordinated timing of the auxiliary and main switch operations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Significantly reduces switching loss and EMI noise levels, enhancing efficiency and power density while minimizing costs by utilizing a single-stage structure with inductive coupling and shared magnetic cores.
Implementation Method 1
an auxiliary inductor unit including a first auxiliary inductor adjusting an amount of current flowing through the first auxiliary switch during a switching operation of the first auxiliary switch, and a second auxiliary inductor adjusting an amount of current flowing through the second auxiliary switch during a switching operation of the second auxiliary switch
Implementation Method 2
a transformer unit including a first transformer transforming the first primary current from the AC power supply unit into a first secondary current, and a second transformer transforming the second primary current from the AC power supply unit into a second secondary current
Data Source
AI summary
There is provided a power supply device including an alternating current (AC) power supply unit supplying a first primary current in a positive half cycle and supplying a second primary current in a negative half cycle; a transformer unit including a first transformer and a second transformer; a main switch unit including a first main switch and a second main switch; an auxiliary switch unit including a first auxiliary switch and a second auxiliary switch; an auxiliary inductor unit including a first auxiliary inductor and a second auxiliary inductor; and a path providing unit providing a conduction path based on power supplied from the AC power supply unit.