LLC Resonant Converter Full Voltage Range Control
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Solution Overview
Problem
LLC resonant converters face reliability issues due to hard-switching states and inability to respond in real-time to bus voltage and load changes, leading to low reliability and challenges in large-scale production.
Innovation Solution
A full voltage range LLC resonant converter design that instantly detects remaining resonant energy and uses a return-to-zero pulse generator to ensure zero-current and zero-voltage switching, eliminating energy storage in capacitors and freewheeling inductors, allowing for real-time control and improved reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase-locked loop control technology is used to control LLC resonant converter, then synchronization between main resonant loop current and control signal can be achieved, but the converter cannot respond in real-time to bus voltage or load changes due to filtering network delay
Solution Approach 1:
The patent extracts and removes the filtering network from the control signal path. By directly sampling the resonant current and feeding it back to the phase detector without passing through a filtering network, the system eliminates the 5-10 cycle delay inherent in traditional phase-locked loop control. This allows real-time detection and response to bus voltage or load changes while maintaining synchronization, thus resolving the contradiction between reliability and response time.
2Stability of the object's composition
If energy storage capacitor and freewheeling inductor are added to the output port of rectifier, then voltage stabilization is improved, but the probability of capacitor failure increases and reliability decreases
Solution Approach 1:
The patent removes the energy storage capacitor and freewheeling inductor from the output port of the rectifier. By directly connecting the rectified voltage to the LLC resonant converter bus without these passive components, the system eliminates the failure points associated with capacitor degradation and inductor saturation. The LLC resonant converter's inherent soft-switching characteristics and energy management capabilities compensate for the removed components, maintaining voltage stability while significantly improving reliability.
Solution Approach 2:
The patent replaces the passive mechanical/electrical energy storage system (capacitor and inductor) with an active control system based on LLC resonant conversion. The active switches and control circuitry dynamically manage energy transfer and voltage regulation, substituting the static energy storage approach with a more reliable active management system that responds in real-time to load and input variations.
3Loss of energy
If turning-on pulse signal is shut down to ensure zero-current and zero-voltage switching, then switching losses are reduced, but natural ZVS or ZCS states are lost when current passes zero due to insufficient resonant energy
Solution Approach 1:
The patent implements direct feedback of the resonant current to the phase detector, enabling real-time monitoring of the current waveform and phase relationship. This feedback mechanism allows the control system to dynamically adjust the turning-on pulse timing based on the actual resonant state, ensuring that soft-switching conditions are maintained even when resonant energy varies. The system can detect when natural ZVS or ZCS would be lost and proactively adjust control signals to prevent hard-switching, thus maintaining both low switching losses and reliable switching states.
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 enables the LLC resonant converter to operate reliably across a full input voltage range, ensuring zero-current and zero-voltage switching states, enhancing reliability and extending the converter's lifetime, making it suitable for applications like electric vehicle charging and electromagnetic induction heating.
Implementation Method 1
the main loop current has passed zero (a resonant capacitor will pick up a voltage signal)
Implementation Method 2
LLC resonant converter has some virtues such as high efficiency, low electromagnetic interference, and simple control in circuitry
Data Source
AI summary
This invention relates to a LLC resonant converter for full input voltage range and its control method. The full voltage range LLC resonant converter comprises a LLC resonant converter circuit, a current type main loop current sampler, a rectifier, a main loop energy quantifier, an energy comparator, a return-to-zero pulse generator, an oscillator, and a split phase controller. The LLC resonant converter is configured to turn on electronic switches with ZVS state in full input voltage range. This invention realizes the full voltage working range of LLC resonant converter, guarantees its reliability, and enables designing a LLC converter to be a solid state converter. The LLC resonant converter can be widely used in applications such as non-contact charging stations for electric vehicle, electromagnetic inductance heating and switch power.