Non-Inverting Buck-Boost LLC Converter Voltage Ratio Control
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Solution Overview
Problem
Resonant power converters face efficiency and power density challenges due to sensitivity to input/output voltage ratios, particularly at low power levels and when supporting universal mains input and USB power delivery, making it difficult to achieve high efficiency and power density, especially with the addition of boost converters which are limited by producing output voltages above peak mains voltage.
Innovation Solution
Incorporating a non-inverting buckboost converter in front of an LLC resonant converter to regulate the output voltage and maintain a desired ratio between input and output voltages, allowing for optimal operation by adjusting parameters such as capacitor voltage and frequency, and using a low power mode at low loads to enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a boost converter is added to support universal mains input and USB power delivery, then the adaptability of the power converter system is improved, but the device complexity increases and efficiency decreases due to additional components and voltage ratio sensitivity
Solution Approach 1:
The patent combines the boost converter and LLC resonant converter into a single integrated power converter system. The boost converter stage is merged with the resonant converter stage, sharing common magnetic components and control circuitry. This integration reduces the overall device complexity while maintaining the ability to support universal mains input (85-265V AC) and USB power delivery protocols, thereby resolving the contradiction between adaptability and complexity.
2Adaptability or versatility
If a boost converter is added to support universal mains input and USB power delivery, then the adaptability of the power converter system is improved, but the efficiency deteriorates due to sensitivity to input/output voltage ratios
Solution Approach 1:
The patent implements dynamic control of the power converter system by continuously monitoring the input voltage and adjusting the operating parameters of both the boost converter and LLC resonant converter stages. The controller dynamically adjusts the duty cycle of the boost converter and the switching frequency of the resonant converter to maintain optimal efficiency across the full input voltage range (85-265V AC) and various output power levels. This dynamic adaptation eliminates the efficiency losses associated with fixed voltage ratio designs, resolving the contradiction between adaptability and efficiency.
3Use of energy by moving object
If the power converter operates at low power levels, then the energy consumption is reduced, but the efficiency deteriorates due to the minimum operating power threshold of resonant converters
Solution Approach 1:
The patent employs dynamic switching between different converter modes based on the load level. At low power levels (below the minimum efficient operating point of the resonant converter), the system dynamically switches to a discontinuous conduction mode or bypasses the resonant stage entirely, using only the boost converter stage. This dynamic mode switching allows the system to operate efficiently at low power levels while maintaining the ability to operate at high efficiency at full power, resolving the contradiction between energy consumption and efficiency at low loads.
4Loss of energy
If the output voltage is regulated to maintain a constant ratio between input and output voltages, then the efficiency is improved, but the adaptability to different USB power delivery protocols decreases
Solution Approach 1:
The patent implements a hierarchical control structure where the outer control loop maintains the constant voltage ratio for efficiency, while the inner control loop dynamically adjusts the output voltage to match USB Power Delivery protocol requirements. The controller monitors the negotiated USB PD protocol and adjusts the target output voltage accordingly, while the boost converter and resonant converter work together to maintain the optimal voltage ratio for efficient operation. This multi-layered dynamic control resolves the contradiction between efficiency and adaptability to different USB PD protocols.
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 configuration enables efficient power conversion up and down, supports USBPD and direct charging with universal mains input, and achieves high efficiency by maintaining a constant ratio between input and output voltages, improving power factor correction and reducing component size.
Implementation Method 1
LLC resonant converter
Implementation Method 2
non-inverting buckboost converter
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
Techniques for operating a power converter system that includes an LLC resonant converter and a non-inverting buckboost converter that is located in front of the LLC resonant converter are disclosed. In an embodiment, the output voltage of a non-inverting buckboost converter is regulated in response to the input voltage and the output voltage of an LLC resonant converter in order to maintain a desired ratio between the input voltage and the output voltage of the LLC resonant converter. For example, the ratio between the input voltage and the output voltage of the LLC resonant converter is controlled to a desired ratio that matches the turns ratio of the LLC resonant converter's transformer and that may also match (as a second order effect) the ratio of Lr to Lm.