LLC Resonant Converter Light Load Power Reduction
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Solution Overview
Problem
LLC resonant converters face challenges in reducing power consumption under no- or light-load conditions due to parasitic effects and noise introduction in existing burst mode operations, especially when accurate feedback is not available.
Innovation Solution
A series resonant LLC converter with a standby drive section and sensing mechanism that monitors current or voltage thresholds to switch between load and standby states, using a second switching section with lower voltage input to reduce power delivery during no- or light-load conditions, allowing for efficient power management without the need for accurate output feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the switching frequency is increased significantly above the resonant frequency to turn off the converter under no-load conditions, then the output power drops, but parasitic effects become significant causing high output voltages and high input power consumption
Solution Approach 1:
The patent implements dynamic switching between two operating modes: a first switching section operates during normal load conditions, while a second switching section operates during no- or light-load conditions. This dynamic reconfiguration allows the system to adapt its power delivery characteristics to match the actual load requirements, preventing the parasitic effects that occur when the first switching section operates significantly above resonant frequency.
Solution Approach 2:
The patent changes the operating parameters by switching between different switching sections with different voltage inputs. The second switching section is configured to receive power at a lower voltage than the high voltage input of the first switching section, fundamentally changing the power delivery parameters to reduce losses under no-load conditions.
2Loss of energy
If burst mode is implemented to reduce power consumption under no-load conditions, then power consumption decreases, but noise is introduced into the voltage signal and accurate output sensing is required
Solution Approach 1:
The patent extracts the sensing function from the output side and relocates it to the input side by monitoring current in the LLC resonant tank. This eliminates the need for opto-couplers and accurate output sensing that are required in burst mode operation, thereby removing the source of noise introduction while still enabling power consumption reduction under no-load conditions.
3Device complexity
If burst mode is implemented without opto-coupler feedback, then device complexity is reduced, but implementation becomes difficult or impossible due to lack of accurate feedback information
Solution Approach 1:
The patent introduces an intermediary sensing mechanism that monitors current in the LLC resonant tank to provide feedback information about load conditions. This intermediary approach enables the system to determine when to switch between operating modes without requiring complex opto-coupler-based output feedback, thereby simplifying the overall device while maintaining implementability.
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 reduces power consumption during no- or light-load conditions by switching to a standby state, minimizing noise and eliminating the need for precise output feedback, thereby enhancing efficiency and operational stability.
Implementation Method 1
The LLC tank filters the input square wave and generates a sinusoidal output current... The circuitry is most efficient when the switching frequency is at or near the resonant frequency of the LLC tank.
Implementation Method 2
The LLC tank filters the input square wave and generates a sinusoidal output current, which is in turn provided to the primary windings of one or more transformers. The transformers may be used for voltage scaling and signal isolation, and may produce an output signal that is provided as a power supply to a load.
Implementation Method 3
it may not be possible to completely turn off the LLC resonant converter by increasing the switching frequency because as the switching frequency gets significantly higher than the resonant frequency, parasitic effects become important.
Data Source
AI summary
This disclosure provides a resonant LLC power converter unit to provide a plurality of power outputs. The power converter unit includes multiple transformers arranged such that at least one primary winding of each transformer is connected in parallel and configured to provide a power output to a secondary that powers one of the plurality of outputs. One of these transformers, or a parallel choke across an output bus, can be used to provide lower power to the output bus during a standby state (i.e., during a light- or no-load condition). The power converter unit includes a first switching section for providing a first power input during normal operation and a second switching section for providing a second power input during no- or light-load conditions.