Primary Side Feedback Control for LLC Resonant Converters

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing LLC resonant power converters require high-voltage isolation elements for signal feedback, increasing costs and complexity due to the need for secondary side output voltage sampling and primary side control, particularly in wide-range input voltage and large power output applications like solar PV systems.

Innovation Solution

A power converter design that includes a primary-side switching circuit, resonant circuit, transformer, voltage sensing circuit, current sensing circuit, and processing circuit, where the processing circuit adjusts the switching frequency based on voltage and current sensing signals directly detected at the primary side, eliminating the need for high-voltage isolation by using a transformer model to relate primary-side voltage to output voltage, thereby controlling the output voltage without secondary side feedback.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If secondary side output voltage sampling and feedback is implemented, then control accuracy is improved, but high-voltage isolation elements are required which increases cost and circuit complexity

Engineering Contradiction:

Improvecontrol accuracyVSAvoidcircuit complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent introduces a transformer model as an intermediary that relates primary-side voltage to output voltage. Instead of directly sampling the secondary side voltage, the system uses the transformer model to infer output voltage characteristics from primary-side measurements, eliminating the need for high-voltage isolation elements while maintaining control accuracy

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent creates a mathematical model (transformer model) that copies the relationship between primary voltage and output voltage. This model allows the system to obtain output voltage information indirectly through primary-side measurements, avoiding the need for direct secondary-side sampling and the associated high-voltage isolation requirements

Inventive Principle:

Principle #26Copying

2Measurement precision

If secondary side output voltage sampling and feedback is implemented, then control accuracy is improved, but high-voltage isolation elements are required which increases cost

Engineering Contradiction:

Improvecontrol accuracyVSAvoidcircuit cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The transformer model serves as an intermediary that eliminates the need for expensive high-voltage isolation elements. By inferring output voltage from primary-side measurements through the model, the system achieves control accuracy without requiring costly isolation components

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces expensive high-voltage isolation elements with a mathematical model implementation in the processing circuit. This approach uses low-cost electronic components and software algorithms instead of expensive hardware isolation elements, significantly reducing circuit cost while maintaining functionality

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 reduces circuit costs and enhances feedback control accuracy and speed by eliminating the need for high-voltage isolation elements and directly controlling the output voltage at the primary side, while maintaining stable output voltage across varying loads.

Implementation Method 1

The transformer includes a primary winding electrically coupled to the primary-side circuit and configured to receive a primary-side square wave signal, and a secondary winding configured to output a secondary ac signal in response to the primary-side square wave signal

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

The resonant circuit is electrically coupled to the primary-side switching circuit and configured to receive the square wave signal to provide a primary-side current

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS10224825B2Primary side feedback control for a resonant converter with a transformer model

Publication Date: 2019.03.05 DELTA ELECTRONICS INC(CN)

AI summary

A power converter includes a primary-side switching circuit, a resonant circuit, a transformer including primary and secondary windings, a secondary-side rectifying circuit, voltage and current sensing circuits, and a processing circuit. The primary-side switching circuit controls switches to be on or off based on a pulse signal to convert an input voltage to a square wave signal. The resonant circuit is coupled to the primary-side switching circuit and receives the square wave signal to provide a primary-side current. The primary winding is coupled to the resonant circuit. The secondary-side rectifying circuit is coupled to the secondary winding and rectifies the secondary ac signal output by the secondary winding and outputs an output voltage. The voltage and current sensing circuits detect the voltage and current of the primary winding and output voltage and current sensing signals. The processing circuit outputs the pulse signal according to the voltage and current sensing signals.