Flyback Converter Switch Timing to Prevent Body Diode Cross Conduction
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Solution Overview
Problem
Conventional flyback converters are prone to cross conduction, which can damage switches by forcing them to operate when there is current flowing through their body diodes.
Innovation Solution
A controller is used to monitor signals from nodes coupling switches in a resonant power converter, delaying the activation of switches until conditions are safe to prevent cross conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If switches are activated to regulate energy conveyance in a flyback converter, then power conversion efficiency is improved, but cross conduction occurs causing switch damage
Solution Approach 1:
The controller monitors the voltage at the coupling node before activating the first switch. By detecting when the voltage reaches a threshold level indicating the second switch's body diode current has ceased, the controller preliminarily ensures safe switching conditions before energizing the first switch, preventing cross conduction damage while maintaining efficient power conversion
2Speed
If switches are operated at high frequency to improve response time, then control precision is improved, but cross conduction risk increases
Solution Approach 1:
The controller continuously monitors the voltage signal at the coupling node between the first and second switches. This feedback mechanism provides real-time information about the second switch's body diode conduction state, enabling the controller to make informed decisions about when to activate the first switch, thus preventing cross conduction even at high switching frequencies
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
The solution effectively prevents cross conduction, reducing stress on switches and improving the reliability of the power converter.
Implementation Method 1
The primary winding and a resonant capacitor are disposed in a resonant circuit path of the resonant power converter
Implementation Method 2
conveyance of energy from a primary winding of a transformer to a secondary winding of the transformer
Data Source
AI summary
A power supply includes a controller. The controller controls switching of a first switch and a second switch in a power supply to regulate conveyance of energy from a primary winding of a transformer to a secondary winding of the transformer to generate an output voltage. To control generation of the output voltage, the controller receives a first signal generated at a first node coupling the first switch and the second switch. As discussed herein, the controller controls activation of the first switch to an ON state depending on a magnitude of the first signal. This disclosure provides improved reliability of power supply components (such as one or more switches) because such components are no longer stressed (or overstressed) due to body diode cross conduction.