Active Clamp DC/DC Converter Peak Current Control via Clamp Sensing

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Solution Overview

Problem

Active clamp DC/DC converters introduce higher circulating currents, which alter current waveforms and hinder the implementation of peak current mode control schemes, while passive snubbers suffer from high power dissipation and inefficiency.

Innovation Solution

An isolated DC/DC converter design incorporating a primary and secondary stage with active clamps, along with first and second current sense nodes, utilizes current differential modules to measure and subtract clamp currents from source currents, recreating the rising slope current signal necessary for peak current mode control, thereby avoiding the need for lossy shunt resistors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If active clamp snubber circuits are used to limit voltage transients, then efficiency is improved and reliability is increased, but circulating currents increase and current waveforms are altered

Engineering Contradiction:

Improveswitching device reliabilityVSAvoidcirculating currents

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent extracts the harmful circulating current component from the total current waveform by using a current sense transformer to sense the clamp current and a differential amplifier to subtract it from the primary current, thereby recovering the original current waveform shape needed for peak current mode control

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces intermediary components including a current sense transformer and differential amplifier circuit that act as mediators to process the current signals, separating the useful current information from the harmful circulating current component

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of energy

If active clamp snubber circuits are used to limit voltage transients, then efficiency is improved, but current waveforms become different from traditional forms needed for peak current mode control

Engineering Contradiction:

Improvepower lossVSAvoidcontrol implementation

Core Design Contradiction:

Loss of energyVSEase of operation

Solution Approach 1:

The patent implements feedback by sensing the clamp current through a current sense transformer and using a differential amplifier to subtract this feedback signal from the primary current signal, thereby restoring the original current waveform characteristics needed for peak current mode control

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-generated harmful factors

If passive RC snubbers are used instead of active clamps, then circulating currents are reduced, but power dissipation increases and efficiency decreases

Engineering Contradiction:

Improvecirculating currentsVSAvoidpower dissipation

Core Design Contradiction:

Object-generated harmful factorsVSLoss of energy

Solution Approach 1:

The patent converts the harmful effect of circulating currents into a beneficial measurement signal by using the current sense transformer to sense the clamp current and the differential amplifier to subtract it, thereby recovering the original current waveform and enabling peak current mode control while maintaining active clamp efficiency

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 accurate peak current mode control, enhancing voltage regulation, input line rejection, short circuit protection, and transformer balancing while maintaining the efficiency benefits of active clamps.

Implementation Method 1

The transformer circuit adjusts an AC voltage level of the high-frequency AC voltage and outputs an adjusted AC voltage

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

the first current sense node includes a first current sense transformer configured to sense the source current flowing through the primary side of the DC/DC converter and the second current sense node is implemented with a second current sense transformer configured to sense the clamp current flowing through the active clamp

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11979084B2Active clamp DC/DC converter including current sense peak control mode control

Publication Date: 2024.05.07 RAYTHEON CO

AI summary

An isolated DC/DC converter includes a primary stage, a transformer circuit, a secondary stage, an active clamp, a first current sense node, and a second current sense node. The primary stage includes a primary switching inverter configured to invert the source DC voltage into a high-frequency alternating current (AC) voltage. The transformer circuit adjusts an AC voltage level of the high-frequency AC voltage and outputs an adjusted AC voltage. The secondary stage includes a secondary switching converter to convert the adjusted AC voltage into a secondary voltage, and the active clamp is configured to clamp the secondary voltage to provide an output DC voltage. The first current sense node is included in the primary stage conducts a source current having a first current level, and the second current sense node is included in the secondary stage and conducts a clamp current having a second current level.