Emulated Current-Mode Control for Resonant Converter Phase Tracking

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Resonant dc-dc converters, particularly those based on LLC series circuits, are difficult to control effectively over a wide operating range due to their non-linear nature, leading to limited bandwidth and undetectable signals at low loads in existing control techniques such as average current-mode, peak current-mode, and charge control.

Innovation Solution

An apparatus and method for emulated current-mode control that uses inputs for determining the phase of resonant current and target phase difference between resonant current and driving voltage to generate control signals, allowing the phase difference to track the target, thereby enhancing bandwidth and avoiding hard switching.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If average current-mode control is used, then the control is stable, but the bandwidth is limited due to the averaging process

Engineering Contradiction:

Improvecontrol stabilityVSAvoidbandwidth

Core Design Contradiction:

Stability of the object's compositionVSSpeed

Solution Approach 1:

The patent replaces the mechanical averaging process with an emulated current-mode control system that uses phase detection and comparison. Instead of averaging current signals over a period, the system detects the phase of resonant current relative to driving voltage and uses phase difference comparison to generate control signals, thereby achieving higher bandwidth without sacrificing stability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the control parameter from averaged current to phase difference. By measuring the phase angle between resonant current and driving voltage, and comparing it with a target phase difference, the system achieves faster response and higher bandwidth while maintaining stable control through the inherent stability of phase-based control in resonant converters.

Inventive Principle:

Principle #35Parameter changes

2Speed

If peak current-mode control or charge control is used, then the bandwidth is improved, but the control signals become undetectable at low loads

Engineering Contradiction:

ImprovebandwidthVSAvoidsignal detectability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent introduces phase detection as an intermediary mechanism that converts the resonant current signal into a phase angle measurement. This phase information remains detectable even at low loads where peak current signals become undetectable, thereby maintaining reliable control across the full operating range while preserving the bandwidth benefits of current-mode control.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent substitutes peak current detection with phase detection. By measuring the phase angle between resonant current and driving voltage instead of detecting peak current amplitude, the system maintains signal detectability at low loads while preserving the high bandwidth characteristics of current-mode control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If conventional control techniques are used, then the implementation is simple, but hard switching occurs leading to increased losses

Engineering Contradiction:

Improvecontrol implementation complexityVSAvoidswitching losses

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent implements feedback by continuously comparing the detected phase difference with a target phase difference and adjusting the switching control signals accordingly. This feedback mechanism ensures that the phase difference is maintained within optimal ranges, preventing hard switching and reducing energy losses while keeping the implementation relatively simple through the use of standard phase detection and comparison circuits.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS11264913B2Apparatus and methods for use in a resonant converter

Publication Date: 2022.03.01 TDK LAMBDA UK

AI summary

An apparatus (21) is described for facilitating emulated current-mode control of a resonant converter (1). The apparatus (21) comprises: an input (21) a for a first signal suitable for use in determining a phase of a resonant current, wherein the resonant current corresponds to a current in a resonant network (3) of the converter (1); an input (21b) for a second signal suitable for use in determining a target phase difference between the resonant current and a driving voltage, wherein the driving voltage corresponds to a voltage provided by a switch network (2) of the converter (1) to the resonant network (3); one or more outputs (21c, 21d) for one or more control signals for controlling operation of the switch network (2); and circuitry (21e-i). The circuitry (21e-i) is configured to: use the first signal in determining a first value, wherein the first value is related to a phase difference between the resonant current and the driving voltage; use the second signal in determining a second value, wherein the second value is related to the target phase difference; and set the one or more control signals based at least in part on a comparison of the first and second values, wherein the one or more control signals are for causing the phase difference to track the target phase difference.