Resonant Converter Control Circuit for Fast Response at Light Load

Solution Overview

Problem

Resonant converters face poor dynamic response due to limited bandwidth when using frequency control, and burst mode operation causes transformer noise and flickering issues in LED applications, especially at light loads.

Innovation Solution

The implementation of a control circuit with a feedforward compensation mechanism that transitions from charge control to frequency control by adjusting the switching frequency, incorporating a feedforward current to enhance dynamic response and reduce output power fluctuations, thereby minimizing noise and flickering.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If frequency control is used in resonant converters, then the control structure is simple, but the dynamic response is poor due to limited bandwidth

Engineering Contradiction:

Improvecontrol structureVSAvoiddynamic response

Core Design Contradiction:

Device complexityVSSpeed

Solution Approach 1:

The patent implements a dynamic control mode switching mechanism that transitions between frequency control and charge control modes based on operating conditions. The control circuit dynamically adjusts the control parameter (frequency or charge) according to the resonant converter's operating state, thereby optimizing both the simplicity of control structure and the speed of dynamic response across different load conditions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the control parameter from fixed frequency to variable charge in certain operating conditions. By switching the control parameter based on operating mode, the system achieves improved dynamic response while maintaining structural simplicity. The control circuit monitors operating conditions and adjusts the control parameter accordingly.

Inventive Principle:

Principle #35Parameter changes

2Speed

If charge control is used in resonant converters, then the dynamic response is improved, but output power fluctuations increase causing noise and flickering

Engineering Contradiction:

Improvedynamic responseVSAvoidoutput power stability

Core Design Contradiction:

SpeedVSStability of the object's composition

Solution Approach 1:

The patent implements a dynamic control mode switching mechanism that transitions between frequency control and charge control modes based on operating conditions. The control circuit dynamically adjusts the control parameter (frequency or charge) according to the resonant converter's operating state, thereby optimizing both the simplicity of control structure and the speed of dynamic response across different load conditions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control circuit incorporates feedback mechanisms to monitor operating conditions and adjust control parameters accordingly. By using feedback to detect load conditions and switching between control modes, the system maintains output power stability while achieving fast dynamic response. The feedback loop ensures that charge control is used only when appropriate, preventing excessive power fluctuations.

Inventive Principle:

Principle #23Feedback

3Loss of energy

If burst mode operation is used at light loads, then efficiency is improved, but transformer noise and flickering occur

Engineering Contradiction:

ImproveefficiencyVSAvoidtransformer noise and flickering

Core Design Contradiction:

Loss of energyVSObject-generated harmful factors

Solution Approach 1:

The patent implements a dynamic control mode switching mechanism that transitions between frequency control and charge control modes based on operating conditions. The control circuit dynamically adjusts the control parameter (frequency or charge) according to the resonant converter's operating state, thereby optimizing both the simplicity of control structure and the speed of dynamic response across different load conditions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the control parameter from fixed frequency to variable charge in certain operating conditions. By switching the control parameter based on operating mode, the system achieves improved dynamic response while maintaining structural simplicity. The control circuit monitors operating conditions and adjusts the control parameter accordingly.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12132385B2Control circuit, resonant converter and integrated circuit control chip

Publication Date: 2024.10.29 SILERGY SEMICON TECH (HANGZHOU) CO LTD

AI summary

A control circuit for a resonant converter, can include: a feedforward circuit configured to generate a feedforward current; a charge feedback circuit configured to receive a resonant current sampling signal representing a resonant current of the resonant converter in a first mode to generate a charge feedback signal, and to receive the resonant current sampling signal and the feedforward current together to generate the charge feedback signal in a second mode; and a driving control circuit configured to generate driving signals according to the charge feedback signal and a first threshold signal, in order to control switching states of power transistors of the resonant converter, where the first threshold signal is generated according to an error compensation signal representing an error information between a feedback signal of an output signal of the resonant converter and a reference signal.