Predictive Synchronous Rectifier Control Using Air Core Toroid
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Solution Overview
Problem
Conventional synchronous rectifier (SR) sensing and control techniques face challenges in high-frequency power converters, including limited bandwidth, high response time, and propagation delay, leading to efficiency losses and sub-optimal performance due to issues with current sensing resistors, current transformers, and voltage drain sensing.
Innovation Solution
The use of a Rogowski coil with an air core toroid surrounding the current path of a transformer, coupled with control logic that generates a voltage signal with a 90-degree phase difference from the SR current, allowing for predictive SR sensing and control through integrator and amplifier logic to adjust the phase and amplify the signal for optimal SR conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional current sensing resistors or current transformers are used for synchronous rectifier sensing, then the sensing function is provided, but the bandwidth is limited and response time is high causing efficiency losses
Solution Approach 1:
The patent replaces conventional current sensing methods (resistors and current transformers) with voltage sensing at the drain terminal. This substitution eliminates the bandwidth limitations and propagation delays inherent in current sensing components, achieving lossless SR control with high-speed response suitable for high-frequency power converters operating above 300 kHz.
Solution Approach 2:
The patent introduces an intermediary sensing approach by measuring the voltage at the drain terminal of the synchronous rectifier FET as a proxy for detecting the SR current state. This intermediary voltage measurement provides indirect but accurate information about the current flow without requiring direct current measurement, thereby avoiding the limitations of current sensing components.
2Loss of time
If conventional voltage drain sensing is used, then the response time is reduced, but propagation delay and bandwidth limitations remain causing sub-optimal performance
Solution Approach 1:
The patent implements a feedback mechanism where the sensed drain voltage is continuously monitored and used to control the SR FET switching. The control logic adjusts the SR conduction based on real-time voltage feedback, ensuring optimal performance by maintaining accurate synchronization between the SR operation and the main switching cycle, thereby eliminating propagation delay issues.
3Productivity
If high-frequency operation is implemented to improve power conversion efficiency, then the efficiency increases, but conventional sensing techniques cannot keep up causing performance degradation
Solution Approach 1:
The patent replaces bandwidth-limited current sensing components with high-speed voltage sensing capability that can operate at frequencies above 300 kHz. This substitution enables the sensing system to keep up with high-frequency power conversion operations, maintaining accurate SR control and preserving power conversion efficiency at high operating 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
This approach enables high-bandwidth SR control with reduced response time and propagation delay, improving the efficiency of high-frequency power converters by providing lossless SR sensing and optimized power conversion.
Implementation Method 1
an air core toroid to surround a current path associated with a transformer having a first winding and a second winding
Data Source
AI summary
For predictive synchronous rectifier sensing and control, an example apparatus includes an air core toroid having a voltage output, the air core toroid adapted to surround a portion of a current path and adapted to be coupled through the current path to a transformer, and a control logic circuit having a voltage input and a control output, the voltage input coupled to the voltage output, and the control output adapted to be coupled to a switch.