SMPS Dead Time Control via Peak Voltage Sampling
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Solution Overview
Problem
In switch mode power supply (SMPS) converters, the use of a fixed dead time between the primary and secondary switches in continuous conduction mode leads to inefficiencies due to prolonged rectification via the body diode of the secondary switch, increasing component temperature and casing temperature.
Innovation Solution
A controller-based system that continuously monitors the peak voltage of the synchronous rectification switch to dynamically adjust the dead time for each switching cycle, optimizing the timing between the turning-off of the synchronous rectification switch and the turning-on of the primary switch based on real-time operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a fixed dead time is used between primary and secondary switches in continuous conduction mode, then the switching timing is simple to control, but the rectification duration via the body diode is prolonged leading to increased energy losses and component temperature
Solution Approach 1:
The dead time is made dynamic rather than fixed. The controller adjusts the dead time duration based on real-time detection of peak voltage conditions at the drain of the synchronous rectification switch. This dynamic adjustment optimizes the rectification duration to minimize energy losses while adapting to varying operating conditions, thereby resolving the contradiction between energy efficiency and control simplicity.
Solution Approach 2:
A feedback mechanism is implemented where the controller detects the peak voltage at the drain of the synchronous rectification switch and uses this information to adjust the dead time. This closed-loop control enables the system to automatically optimize the rectification duration, reducing energy losses while maintaining manageable controller complexity through systematic feedback processing.
2Temperature
If a fixed dead time is used between primary and secondary switches, then the control implementation is straightforward, but the component temperature and casing temperature increase due to prolonged body diode rectification
Solution Approach 1:
The dead time is dynamically adjusted based on detected peak voltage conditions rather than being fixed. This dynamic control reduces the rectification duration through the body diode, thereby reducing heat generation and component temperature. The complexity increase is managed through systematic detection and adjustment mechanisms that adapt to varying operating conditions.
Solution Approach 2:
The controller implements feedback by detecting peak voltage at the drain of the synchronous rectification switch and using this information to adjust dead time. This feedback loop enables automatic optimization of rectification duration, reducing thermal losses and component temperature while maintaining controlled complexity through structured feedback processing.
3Productivity
If the dead time is reduced to minimize body diode rectification, then efficiency improves, but the risk of switch overlap or improper timing increases
Solution Approach 1:
The controller uses feedback from peak voltage detection at the drain of the synchronous rectification switch to determine the optimal dead time. This feedback mechanism ensures that the dead time is reduced enough to improve efficiency but not so much that switching reliability is compromised. The systematic adjustment based on real-time conditions maintains both efficiency and reliability.
Solution Approach 2:
The dead time parameter is dynamically changed based on detected operating conditions rather than being fixed. By adjusting this critical timing parameter according to peak voltage detection, the system optimizes conversion efficiency while maintaining switching reliability through condition-based parameter adaptation.
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 enhances efficiency by minimizing the duration of rectification via the body diode, reducing energy losses and maintaining low component and casing temperatures, even under varying input and output conditions.
Implementation Method 1
The controller is configured to operate in several operation modes including the operation in continuous conduction mode. In continuous conduction mode the controller determines and sets a time between turning-off of the synchronous rectification switch and turning-on of the primary switch based on a sampling of peak voltage of drain of the synchronous rectification switch.
Implementation Method 2
A power supply having a primary side and a secondary side is disclosed. The power supply includes a main transformer having a first side and a second side. The first side is coupled to the primary side and the second side coupled to the secondary side.
Data Source
AI summary
A power supply having a primary side and a secondary side is disclosed. The power supply includes a main transformer having a first side and a second side. The first side is coupled to the primary side and the second side coupled to the secondary side. The power supply further includes a primary switch coupled to the first side and a synchronous rectification switch coupled to the second side. A controller is included for driving the primary switch and the synchronous rectification switch in several operation modes including the operation in continuous conduction mode. The controller is configured to determine and set a time between turning-off of the synchronous rectification switch and turning-on of the primary switch based on sampling of the peak voltage at the drain of the synchronous rectification switch and selecting the time that corresponds with the lowest peak voltage on the drain of the synchronous rectification switch.