LLC Resonant Converter Duty Control for Linear Gain and Low Ripple
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Solution Overview
Problem
LLC resonance converters exhibit nonlinear input/output voltage gain characteristics, making it difficult to control and resulting in output current ripples, which can affect the durability of converter elements and lead to improper output voltage/current control.
Innovation Solution
A method and device for controlling LLC resonance converters by detecting parameter values such as input voltage, output voltage, or switching frequency, and determining a switching duty using scaling and offset values to correct the gain value, allowing for variable duty control to linearize the gain curve and reduce output current ripples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If switching frequency control is used to determine input/output relation of LLC resonance converter, then the converter can operate with resonance current, but the input/output voltage gain characteristic curve becomes nonlinear and control becomes difficult
Solution Approach 1:
The patent applies dynamics by transitioning from static switching frequency control to dynamic duty cycle control. The controller dynamically adjusts the duty cycle of switching elements based on real-time operating conditions, enabling linear control characteristics while maintaining resonance operation. This dynamic control approach allows the system to adapt switching parameters continuously, resolving the nonlinearity issue inherent in fixed-frequency control.
Solution Approach 2:
The patent changes the control parameter from switching frequency to duty cycle. By controlling the duty cycle of switching elements rather than adjusting switching frequency, the system achieves linear input/output voltage gain characteristics. This parameter transformation maintains the benefits of resonance current while eliminating the nonlinearity problem, as the duty cycle directly controls the voltage transfer ratio in a linear manner.
2Reliability
If switching frequency is controlled to manage LLC resonance converter, then resonance operation is maintained, but output current ripples increase affecting durability
Solution Approach 1:
The patent uses dynamic duty cycle adjustment to maintain resonance operation while minimizing output current ripples. By continuously optimizing the duty cycle based on load conditions and resonance characteristics, the system maintains stable resonance operation and reduces current ripple amplitude. This dynamic control prevents the ripple generation that occurs with fixed-frequency switching.
Solution Approach 2:
The patent implements feedback control by monitoring output current and adjusting the duty cycle accordingly. The controller uses feedback signals to detect resonance conditions and optimize switching duty, thereby maintaining stable resonance operation while actively suppressing output current ripples. This closed-loop control ensures that resonance operation stability is maintained while minimizing harmful current variations.
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 solution improves the linearity of the gain curve, reduces output current ripples, and enables low-gain output and low-load control by adjusting switching duty and frequency, enhancing the operational stability and efficiency of the converter.
Implementation Method 1
an LLC resonance converter using LC resonance may be employed as a DC-DC converter
Data Source
AI summary
A method for controlling an LLC resonance converter controls a converter through the steps of detecting parameter values related to operation of the converter, determining a switching duty of the converter on the basis of the detected parameter values, and controlling the converter with the determined switching duty to improve nonlinearity of a gain curve of the converter, thereby reducing output current ripples and achieving low-gain output.