Active Snubber Circuit for LLC Converter Ringing Suppression

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Solution Overview

Problem

Conventional power converters experience high frequency oscillations due to parasitic elements, leading to inefficient operation, increased component costs, and electromagnetic interference, which are not effectively addressed by existing snubber circuits that dissipate ringing energy as heat.

Innovation Solution

An active snubber circuit is introduced, utilizing a series-coupled capacitor and diode with an active switch that redirects ringing energy to the output of the converter, employing at least one active component to reroute energy and increase efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If conventional passive snubber circuits are used to damp ringing oscillations, then electromagnetic interference is reduced, but converter efficiency decreases due to energy dissipation as heat

Engineering Contradiction:

Improveelectromagnetic interferenceVSAvoidconverter efficiency

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The patent converts the harmful ringing energy into beneficial output energy by using an active snubber circuit that redirects the oscillation energy through a controlled switch to the output capacitor, transforming what would be wasted energy into useful output energy, thereby improving overall converter efficiency while still suppressing EMI

Inventive Principle:

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

Solution Approach 2:

The patent changes the operational state of the snubber circuit from passive energy dissipation to active energy redirection by controlling the switch timing and state, dynamically adjusting circuit parameters to redirect energy flow based on the switching cycle phase

Inventive Principle:

Principle #35Parameter changes

2Reliability

If higher rated circuit components are used to operate in the ringing environment, then reliability is improved, but cost increases

Engineering Contradiction:

Improvecomponent reliabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies prior cushioning by introducing the active snubber circuit before the ringing oscillations can damage components, actively suppressing the oscillations through controlled energy redirection, thereby protecting components from stress and allowing the use of lower-rated, more cost-effective components

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Volume of moving object

If higher switching frequencies are used to allow smaller components, then converter size is reduced, but ringing oscillations increase due to parasitic elements

Engineering Contradiction:

Improveconverter sizeVSAvoidringing oscillations

Core Design Contradiction:

Volume of moving objectVSObject-generated harmful factors

Solution Approach 1:

The patent introduces an intermediary active snubber circuit between the parasitic elements and the main power components, which mediates the harmful effects of ringing oscillations by actively controlling energy flow, thereby enabling high-frequency operation with smaller components without suffering from excessive ringing

Inventive Principle:

Principle #24Intermediary (Mediator)

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 active snubber circuit reduces ringing waveforms, allowing for the use of lower-rated components, enhances converter reliability, and increases efficiency by redirecting energy that would otherwise be dissipated, particularly under moderate load conditions.

Implementation Method 1

a series-coupled first capacitor and diode associated with a secondary-side switch in the power converter and coupled to an output thereof

Methodology Applied

Scientific EffectEnergy redirection through capacitor-diode circuit: Capacitance

Implementation Method 2

an active snubber circuit switch coupled in parallel with the diode and configured to receive a control signal that closes the active snubber circuit switch during at least a portion of a time during which the secondary-side switch is open

Methodology Applied

Scientific EffectSwitching control: Conduction (electrical)

Data Source

PatentUS8547711B2LLC converter active snubber circuit and method of operation thereof

Publication Date: 2013.10.01 ACLEAP POWER INC

AI summary

An active snubber circuit for a power converter, a method of operating the same and an inductor inductor capacitor converter incorporating the circuit or the method. In one embodiment, the circuit includes: (1) a series-coupled first capacitor and diode associated with a secondary-side switch in the power converter and coupled to an output thereof and (2) an active snubber circuit switch coupled in parallel with the diode and configured to receive a control signal that closes the active snubber circuit switch during at least a portion of a time during which the secondary-side switch is open.