Adaptive Synchronous Rectifier Deglitching for Power Converter Efficiency
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Solution Overview
Problem
Flyback switching power converters face efficiency losses due to noise-induced glitches from electrostatic discharge, which conventional deglitch filtering attempts to mitigate but at the cost of delayed switching times, risking system damage and inefficiency.
Innovation Solution
An adaptive SR controller with a deglitch control circuit that disables deglitch filtering during specific periods to allow unfiltered drain-to-source voltage comparisons, enabling faster switching while re-enabling filtering to prevent noise-induced glitches, thus balancing efficiency and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deglitch filtering is applied to the VD-S voltage, then the system is protected from noise-induced glitches, but the switching time of the SR switch transistor is delayed, reducing efficiency
Solution Approach 1:
The patent applies dynamics by making the deglitch filter adaptive rather than static. The filter's delay parameter is dynamically adjusted based on the operating state of the power converter. During normal operation, the filter uses a longer delay to protect against glitches. During detected glitch conditions or specific operational phases, the filter reduces its delay or is temporarily bypassed, allowing faster switching response. This dynamic adaptation resolves the contradiction by providing both protection and speed at different times as needed.
Solution Approach 2:
The patent changes the parameter of the deglitch filter's delay time based on operating conditions. The filter circuit includes controllable elements that adjust the RC time constant or equivalent delay parameter. When a glitch is detected or during specific phases of the switching cycle, the delay parameter is reduced or disabled, allowing the SR switch to respond quickly. During normal stable operation, the full delay is applied to filter noise. This parameter change strategy resolves the contradiction between protection and speed.
2Productivity
If the deglitch filter delay is reduced to improve switching speed, then efficiency increases, but the system becomes vulnerable to noise-induced premature switching
Solution Approach 1:
The system dynamically adjusts the deglitch filter characteristics based on real-time monitoring of the VD-S voltage and switching state. When the system detects conditions indicative of potential noise interference or during critical switching transitions, it increases the filter delay to prevent premature switching. During stable operation phases where speed is critical, the filter delay is reduced or bypassed. This dynamic adjustment maintains high efficiency while providing protection when needed.
Solution Approach 2:
The patent implements feedback by monitoring the VD-S voltage waveform and the output of the turn-on comparator to detect glitch conditions. When a glitch is detected (such as abnormal voltage spikes or unexpected comparator transitions), the system adjusts the deglitch filter parameters in response. This feedback mechanism allows the system to maintain aggressive, fast switching during normal operation while automatically increasing protection when noise or anomalies are detected, thus resolving the contradiction between speed and protection.
Data Source
AI summary
A synchronous rectifier controller method is provided for controlling the on and off periods of a synchronous rectifier (SR) switch transistor in a switching power converter. The method includes a first step of monitoring an unfiltered to control whether the SR switch transistor is turned on during a first part of a power switch cycle. The method also includes a second step of monitoring a filtered SR switch signal to control whether the SR switch is turned on during a remaining second part of the power switch cycle.