Flyback Converter Pre-Magnetization for Fixed Frequency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Flyback converters operating in discontinuous conduction mode (DCM) face challenges in maintaining a fixed switching frequency while minimizing switching losses, as the quasi-resonant operation mode leads to varying switching frequencies and increased losses due to parasitic oscillations.
Innovation Solution
The method involves pre-magnetizing the transformer for a specific period before switching on the primary electronic switch, introducing a delay time to ensure the switch operates at a predefined frequency, thereby reducing switching losses by controlling the pre-magnetizing and demagnetizing periods to stabilize the voltage across the switch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the flyback converter is operated in quasi-resonant mode to minimize switching losses, then switching losses are reduced, but the switching frequency varies and cannot be maintained at a fixed frequency
Solution Approach 1:
The transformer is pre-magnetized before the main switching cycle begins. This preliminary action sets up specific initial conditions (magnetic flux state) that allow the converter to operate at a fixed frequency while minimizing switching losses by controlling when the switch turns on relative to the resonant oscillation cycle
2Ease of operation
If the electronic switch is operated at a fixed frequency, then the switching frequency is stable, but switching losses increase due to parasitic oscillations during the delay time
Solution Approach 1:
The parasitic oscillations that cause losses are converted into a beneficial resource. The resonant oscillation that was previously harmful is now used to determine the optimal switching moment. By switching on when the voltage reaches its minimum during the oscillation, the harmful oscillation energy is utilized to reduce switching losses while maintaining fixed frequency operation
3Reliability
If the transformer is completely demagnetized before switching on the electronic switch, then parasitic oscillations occur during the delay time, but switching losses increase when switching on at voltage minimum in quasi-resonant mode
Solution Approach 1:
The magnetic flux parameter is controlled and adjusted to specific values before switching. By pre-magnetizing the transformer to a predetermined flux state, the system changes the operating parameters to allow fixed frequency switching at optimal points in the resonant cycle, minimizing losses while maintaining reliable operation
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
This approach allows for stable, low-switching-loss operation at a fixed frequency, reducing energy transfer inefficiencies and maintaining consistent performance independent of load power consumption.
Implementation Method 1
Magnetizing the transformer includes storing energy in the transformer
Implementation Method 2
During this delay time, parasitic oscillations of a voltage across the electronic switch may occur
Data Source
AI summary
In accordance with an embodiment, a method in a voltage converter includes, in each of successive drive cycles, switching on for an on-period a first electronic switch connected in series with a primary winding of a transformer. Before first electronic switch is switched on, the transformer is pre-magnetized for a pre-magnetizing period, where there is a first delay time between an end of the pre-magnetizing period and a beginning of the on-period.