Flyback Converter Auxiliary Switch Control for ZVS
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Solution Overview
Problem
Conventional flyback converter control schemes are inadequate for applications with variable output voltages, as they require constant turn-on time and dead time for the auxiliary switch, leading to increased complexity and obstacles in controlling variable dead time, especially at higher switch frequencies.
Innovation Solution
A method and apparatus for controlling a flyback converter that adjusts the turn-on time of the auxiliary switch based on input and output voltage signals, ensuring zero-voltage switching of the main switch by determining the turn-on time period and dead time dynamically, allowing for efficient operation across varying voltage conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If constant turn-on time and dead time are used for the auxiliary switch, then the control scheme is simple, but it is not suitable for applications with variable output voltages
Solution Approach 1:
The patent applies dynamics by making the turn-on time of the auxiliary switch variable rather than constant. The controller dynamically adjusts the turn-on time based on detected output voltage levels, allowing the flyback converter to adapt to different voltage requirements (such as USB PD standards) while maintaining a relatively simple control architecture.
2Loss of energy
If variable turn-on time and dead time are used to optimize efficiency, then efficiency is improved, but the complexity of the controller increases
Solution Approach 1:
The patent applies parameter changes by varying the turn-on time parameter of the auxiliary switch based on output voltage conditions. The controller detects the output voltage level and adjusts the turn-on time parameter accordingly, enabling efficient operation across different voltage ranges without requiring complex control algorithms.
3Productivity
If switch frequency is increased, then productivity is improved, but transmission delay and parameter tolerance become larger obstacles
Solution Approach 1:
The patent applies preliminary action by turning on the auxiliary switch before the main switch turns off. This creates a dead time interval during which the auxiliary switch conducts, allowing the main switch voltage to rise to the input voltage level before the next switching cycle begins. This preliminary action ensures reliable ZVS operation even at higher switching frequencies where timing margins are reduced.
Data Source
AI summary
The present invention discloses a method and an apparatus for controlling a flyback converter, the flyback converter including a main switch, a transformer, and an auxiliary switch. The method includes: obtaining a first voltage signal and a second voltage signal, the first voltage signal representing an input voltage of the flyback converter, and the second voltage signal representing an output voltage of the flyback converter; controlling turn-on of the auxiliary switch, wherein the turn-on time period of the auxiliary switch is determined according to the first voltage signal and the second voltage signal; and turning on the main switch at ZVS condition, wherein the main switch is turned on at the time delayed for a duration of a dead time after turning off of the auxiliary switch.