Synchronous Rectifier Control Logic for Low Voltage Efficiency

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Solution Overview

Problem

Existing switched-mode power supplies for field devices in automation technology face inefficiencies, particularly at low input voltages, and require complex control loops for galvanic isolation, leading to reduced efficiency and increased technical complexity.

Innovation Solution

A synchronous rectifier with a controllable switching element, smoothing unit, and control logic that adapts to input signals, eliminating the need for a control loop between the primary and secondary sides, and includes an overvoltage protection unit to prevent damage to the smoothing unit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a primary clocked switched-mode power supply with high-frequency transformer is used, then efficiency is improved, but device complexity increases due to control loops and optocouplers

Engineering Contradiction:
ImproveefficiencyVSAvoidtechnical complexity
Core Design Contradiction:
Loss of energyVSDevice complexity

Solution Approach 1:

The patent extracts and removes the control loop and optocoupler from the primary clocked switched-mode power supply circuit. By using a synchronous rectifier with integrated control logic that directly controls the rectifier switching elements, the system eliminates the complex feedback control infrastructure while maintaining high efficiency operation.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The synchronous rectifier incorporates self-contained control logic that autonomously controls the rectifier switching elements based on local signal processing. This self-service capability eliminates the need for external control loops and optocouplers, reducing device complexity while maintaining efficient operation.

Inventive Principle:
Principle #25Self-service

2Device complexity

If a synchronous rectifier with control logic is used, then device complexity is reduced, but reliability may worsen due to potential overvoltage damage to the smoothing unit

Engineering Contradiction:
Improvetechnical effortVSAvoidoperational reliability
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The patent implements an overvoltage protection unit positioned between the rectifier unit and smoothing unit. This protection mechanism proactively limits excessive voltages before they can reach and damage the smoothing unit, providing beforehand cushioning against potential failures and ensuring operational reliability.

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

3Adaptability or versatility

If rectifier switching elements are controlled based on input and output signals, then adaptability is improved, but device complexity increases due to control logic requirements

Engineering Contradiction:
ImproveflexibilityVSAvoidcontrol logic
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent merges the control logic functionality directly into the synchronous rectifier unit. By integrating the control logic that processes input and output signals within the rectifier itself, the system achieves flexible adaptability while avoiding the additional complexity of separate control circuits, as the control functions are unified within the existing rectifier structure.

Inventive Principle:
Principle #5Merging (Combining)

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 synchronous rectifier achieves high efficiency at low input voltages, reduces technical complexity, and ensures reliable operation by adapting to input signals and preventing overvoltage damage, thereby enhancing the performance of switched-mode power supplies.

Implementation Method 1

a rectifier unit (5) consisting of at least one controllable switching element (12)

Methodology Applied
Scientific EffectRectification: Diode

Implementation Method 2

a smoothing unit (7), which is connected downstream of the rectifying unit (5) and smoothes the signal (23)

Methodology Applied
Scientific EffectCapacitance: Capacitance

Data Source

PatentEP2997653B1Synchronous rectifier, use of such a synchronous rectifier in a switched-mode power supply, and switch mode power supply
Publication Date: 2019.08.07 ENDRESS & HAUSER GMBH & CO KG
  • EP2997653B1 patent drawingFigure 1~2
  • EP2997653B1 patent drawingFigure 3a~3b
  • EP2997653B1 patent drawingFigure 4

AI summary

The invention relates to a synchronous rectifier (1), which rectifies an alternating voltage signal as an input signal and/or forwards a direct voltage signal as an input signal for use as an output signal, comprising at least: a rectification unit (5) consisting of at least one controllable switching element (12); a smoothing unit (7), which is connected downstream of the rectification unit (5) and smoothens the signal rectified or forwarded by the rectification unit (5) and provides said signal for use as an output signal (Ua); a control logic system (2, 3, 4), which actuates the rectification unit (5) using the input signal and the output signal (Ua) coming from the smoothing unit (7).