LC Resonant Converter Control Switching Feedback to Open-Loop
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Solution Overview
Problem
Conventional control methods for LC resonant converters, such as LLC and LCC converters, result in significant changes in output voltage during load changes due to non-linear gain characteristics, leading to instability.
Innovation Solution
A control apparatus that switches from feedback control to open-loop control, determining a suitable switching frequency based on input voltage, output current, and target voltage to maintain a stable output voltage, using equations to calculate the optimal switching frequency and drive the switching elements accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedback control is performed on switching frequency using output voltage, then output voltage regulation is achieved, but large changes in output voltage occur during load changes due to non-linear gain characteristic
Solution Approach 1:
The patent applies parameter changes by switching between two control modes (feedback control and open-loop control) based on operating conditions. The control apparatus determines whether to use feedback control or open-loop control with predetermined switching frequency based on input voltage and load conditions, thereby adapting the control parameter to maintain stable output voltage across different operating states
Solution Approach 2:
The patent implements dynamics by making the control method adaptive rather than static. The control apparatus dynamically selects between feedback control and open-loop control based on real-time operating conditions (input voltage level, load change state), allowing the system to optimize performance for each specific operating state rather than using a single fixed control approach
2Device complexity
If conventional feedback control is used, then control simplicity is maintained, but output voltage changes significantly with operation state (input voltage, output current)
Solution Approach 1:
The patent applies segmentation by dividing the control range into multiple segments or regions based on input voltage levels and load conditions. The control apparatus determines which control mode (feedback or open-loop) to use based on the current operating segment, allowing different control strategies to be applied to different operating conditions to maintain consistent output voltage
Solution Approach 2:
The patent uses feedback control in certain operating conditions where it is effective, while switching to open-loop control in other conditions. The control apparatus continuously monitors operating parameters and adjusts the control mode accordingly, utilizing feedback when it provides stable regulation while avoiding it when non-linear effects cause instability
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 effectively suppresses large changes in output voltage during load changes, improving stability and reducing voltage fluctuations compared to conventional feedback control methods.
Implementation Method 1
an LC resonant converter (10) including an LC resonant circuit (12) that transforms electrical energy at a different frequency into electrical energy at a desired output frequency
Data Source
Figure 1
Figure 2A~2B
Figure 2C
AI summary
Provided is a technique that makes it possible to suppress occurrence of a large change in an output voltage of an LC resonant converter (LLC converter, LCC converter, etc.,) when the operation state of the LC resonant converter changes. A power supply apparatus includes an LC resonant converter (10) and a control unit (20), and when a change extent of an output current and the like exceed a change extent threshold value, the control unit (20) suspends output voltage feedback control, and start open-loop control for obtaining, from an input voltage and the like of the LC resonant converter (10), a switching frequency at which an output voltage of the LC resonant converter (10) reaches a target voltage, and driving each switching element in a generation circuit (11) of the LC resonant converter (10) at the obtained switching frequency.