LLC Resonant Converter Dynamic Frequency Control for LED Efficiency
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Solution Overview
Problem
LLC resonant converters face efficiency impairment when used in constant-current LED power supply devices due to their inability to operate at high-effective resonant frequencies across a wide output voltage range, leading to increased resonant current and reduced efficiency.
Innovation Solution
A control method and circuit structure for LLC resonant converters that dynamically adjust operation modes based on output voltage and current detection, switching between first and second modulation modes to maintain efficient operation across a wide output voltage range, ensuring the converter operates at high-effective resonant frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the LLC resonant converter is designed with a fixed resonant frequency set for lower output voltage, then it can operate effectively at low voltage, but it generates large resonant current and reduced efficiency when output voltage is increased
Solution Approach 1:
The patent applies dynamics by making the resonant frequency adjustable rather than fixed. The control circuit dynamically changes the resonant frequency based on the detected output voltage level, allowing the converter to operate at optimal frequency across different voltage conditions. This resolves the contradiction by enabling the system to adapt its resonant frequency: using a lower frequency for low voltage output and a higher frequency for high voltage output, thereby maintaining efficiency across the entire operating range.
Solution Approach 2:
The patent implements parameter changes by varying the resonant frequency parameter according to the output voltage. The control circuit detects the output voltage and adjusts the resonant frequency accordingly - when output voltage is low, the resonant frequency is set lower; when output voltage is high, the resonant frequency is increased. This parameter adaptation eliminates the large resonant current problem at high voltage while maintaining effective operation at low voltage.
2Adaptability or versatility
If the LLC resonant converter operates in constant current mode with fixed resonant frequency, then it can drive LED loads, but it cannot maintain high efficiency across a wide output voltage range (2-4 times variation)
Solution Approach 1:
The patent employs feedback by using a control circuit that continuously detects the output voltage and uses this information to adjust the resonant frequency. The feedback mechanism ensures that the resonant frequency is optimally matched to the current operating conditions, allowing the converter to maintain high efficiency across the wide 2-4 times voltage variation range while continuing to drive LED loads in constant current mode.
Solution Approach 2:
The system transitions from static fixed-frequency operation to dynamic frequency adjustment. The control circuit actively modifies the resonant frequency in real-time based on output voltage conditions, enabling the converter to adapt to the wide voltage range (2-4 times variation) while maintaining both LED driving capability and high efficiency throughout the entire operating range.
3Reliability
If the resonant frequency is set for lower output voltage to ensure operation at low voltage, then low voltage operation is effective, but the converter cannot operate at high-effective resonant frequency when output voltage increases
Solution Approach 1:
The patent applies parameter changes by making the resonant frequency a variable parameter that changes with output voltage. The control circuit detects the output voltage level and adjusts the resonant frequency parameter accordingly - maintaining a lower frequency for low voltage operation to ensure reliability, and increasing the frequency to a high-effective level when output voltage rises, thereby optimizing productivity and efficiency at high voltage without sacrificing low voltage operation effectiveness.
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
Enhances efficiency of LLC resonant converters by dynamically adjusting operation modes in response to output voltage and current, allowing for effective frequency operation across a wide voltage range, thereby improving LED power supply device performance.
Implementation Method 1
The isolation transformer includes a primary winding and a secondary winding, wherein the primary winding of the isolation transformer is electrically connected with the primary side circuit
Implementation Method 2
LLC resonant converters with zero voltage switching (ZVS) capabilities and zero current switching (ZCS) capabilities have been widely used
Data Source
AI summary
A control method for an LLC resonant converter includes the following steps. Firstly, the LLC resonant converter is enabled. Then, the sonant converter is operated in a first modulation mode, so that the magnitude of the output voltage is greater than or equal to an intermediate voltage value. When the magnitude of the output current is greater than zero, a determining step is performed to determine whether the magnitude of the output voltage is greater than a reference voltage value. When the determining result is satisfied, the LLC resonant converter is operated in the first modulation mode. When the determining result is not satisfied, the LLC resonant converter is operated in a second modulation mode, so that the magnitude of the output voltage is lower than the intermediate voltage value.