Synchronous Rectifier Turn-On Control Using Drain Voltage Differentiation

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Solution Overview

Problem

In power conversion apparatuses using synchronous rectification, the increasing operating frequency of current power supply systems makes it challenging to accurately determine the turn-on timing of synchronous rectification transistors, leading to potential current reflux and damage due to the close similarity between the slope of the drain voltage during inductor-current discharge and inductor-capacitor oscillation periods.

Innovation Solution

A synchronous rectification controller is introduced, featuring a turn-on control circuit that performs differentiation or integration operations on the drain voltage signal to determine whether to turn on the synchronous rectification transistor based on threshold voltages and signal values, distinguishing between inductor-current discharge and inductor-capacitor oscillation periods, thereby improving the accuracy of switching control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the operating frequency of power supply systems is increased, then the power conversion efficiency is improved, but the accuracy in determining turn-on timing of synchronous rectification transistor deteriorates

Engineering Contradiction:

Improvepower conversion efficiencyVSAvoidturn-on timing determination accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent introduces an intermediary signal processing mechanism that detects the drain voltage signal characteristics and generates a control signal to accurately determine turn-on timing. This intermediary detection system resolves the timing determination problem by analyzing voltage signal features rather than relying on fixed frequency-based timing, thus maintaining accuracy even as operating frequency increases.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If the slope of drain voltage during inductor-current discharge becomes closer to the slope during inductor-capacitor oscillation period, then the operating frequency is improved, but the reliability of current reflux prevention deteriorates

Engineering Contradiction:

Improveoperating frequencyVSAvoidcurrent reflux prevention

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent employs feedback mechanisms that continuously monitor the drain voltage signal characteristics and adjust the turn-on control accordingly. By detecting the actual voltage signal features in real-time and feeding this information back to the control logic, the system can reliably distinguish between discharge and oscillation periods even when their slopes become similar, preventing current reflux while maintaining high operating frequency.

Inventive Principle:

Principle #23Feedback

3Device complexity

If conventional turn-on determination method is used, then the device complexity is reduced, but the measurement precision of turn-on timing deteriorates

Engineering Contradiction:

Improvecontrol circuit complexityVSAvoidturn-on timing accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent replaces conventional mechanical or simple timing-based turn-on determination methods with an electronic signal processing approach. By substituting the traditional timing mechanism with electronic detection and processing of drain voltage signal characteristics, the system achieves higher measurement precision while maintaining relatively simple device complexity through integrated circuit implementation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 solution enhances the accuracy of synchronous rectification transistor switching, preventing current reflux and ensuring the safety and reliability of power conversion apparatuses by accurately distinguishing between discharge and oscillation periods.

Implementation Method 1

performs at least one of a differentiation operation and an integration operation on a drain voltage signal of the synchronous rectification transistor

Methodology Applied

Scientific EffectDifferentiation operation:

Implementation Method 2

performs at least one of a differentiation operation and an integration operation on a drain voltage signal of the synchronous rectification transistor

Methodology Applied

Scientific EffectIntegration operation:

Data Source

PatentUS11742769B2Power conversion apparatus and synchronous rectification controller thereof

Publication Date: 2023.08.29 POWER FOREST TECH

AI summary

A power conversion apparatus and a synchronous rectification controller thereof are provided. At least one of a differentiation operation and an integration operation is performed on a drain voltage signal of a synchronous rectification transistor. According to at least one of a differential signal obtained by performing the differential operation and an integral signal obtained by performing the integral operation, it is determined whether to turn on the synchronous rectification transistor at the next time when the drain voltage signal is less than or equal to a turn-on threshold voltage.