Current Sensing Apparatus for LLC Resonant Converter
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Solution Overview
Problem
LLC resonant converters face challenges in achieving high power density and efficiency due to limitations in current sensing and control, particularly in detecting currents through the resonant tank, which affects zero voltage and zero current switching performance.
Innovation Solution
A current sensing apparatus is integrated into the LLC resonant converter, comprising a switch network, a resonant tank, a transformer, and an ac current sensing circuit, which detects the current flowing through the series resonant inductor and converts it into an average signal with a magnitude greater than the reference voltage source, enabling improved current sensing and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current sensing apparatus is integrated into the LLC resonant converter to detect current through the resonant tank, then current sensing precision and control performance are improved, but device complexity increases
Solution Approach 1:
The patent introduces a magnetic device as an intermediary component that couples to the series resonant inductor. The magnetic device converts the current information into a detectable signal through magnetic coupling, enabling indirect current measurement without direct electrical contact with the high-current path. This intermediary approach improves measurement precision while isolating the sensing circuit from the harsh electrical environment.
Solution Approach 2:
The patent replaces direct electrical current measurement with a magnetic field-based detection system. By using magnetic coupling between the series resonant inductor and the magnetic device, the system substitutes electrical measurement with magnetic field interaction, which reduces electrical interference and improves measurement accuracy while simplifying the electrical isolation requirements.
2Reliability
If the average current signal magnitude is increased to be greater than the reference voltage source, then control loop performance and detection reliability are improved, but signal processing complexity increases
Solution Approach 1:
The patent modifies the signal parameters by designing the magnetic device and associated circuitry to output an average current signal with magnitude deliberately set greater than the reference voltage source. This parameter change ensures the signal exceeds the reference level under all operating conditions, improving detection reliability and simplifying comparator design by eliminating the need for additional signal amplification stages.
3Loss of energy
If zero voltage switching and zero current switching are achieved through improved current sensing, then switching losses are reduced and efficiency is improved, but control system complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where the average current signal from the magnetic device is continuously fed back to the control circuit. This feedback enables the controller to adjust the switching timing and duration to achieve zero voltage switching (ZVS) and zero current switching (ZCS) conditions, minimizing switching losses. The feedback loop automatically maintains optimal switching conditions without requiring complex manual intervention.
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 enhances the performance of LLC resonant converters by enabling accurate current detection and control, leading to improved efficiency, current limiting, short-circuit protection, and achieving zero voltage and zero current switching, thereby increasing power density and efficiency.
Implementation Method 1
a current sensing apparatus coupled to the series resonant inductor through a magnetic coupling, wherein the current sensing apparatus is configured to generate a detected signal proportional to a current flowing through the series resonant inductor
Data Source
AI summary
An apparatus comprises a magnetic device coupled to an inductor-inductor-capacitor (LLC) resonant converter, an ac current sensing circuit coupled to the magnetic device, an average current sensing circuit coupled to the ac current sensing circuit and a reference voltage source coupled to the average current sensing circuit, wherein the reference voltage source is configured such that a magnitude of an average signal from the average current sensing circuit is greater than a voltage level of the reference voltage source.