Multi-Phase LLC Resonant Converter Neutral Line Harmonic Control
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Solution Overview
Problem
Conventional multi-phase LLC resonant converter circuits experience increased circuit loss, efficiency drop, and generation of third harmonic currents when the DC input voltage decreases, leading to inefficiencies and unwanted current spikes during boosting operations.
Innovation Solution
The proposed multi-phase LLC resonant converter circuit incorporates a neutral line reactor connected between the neutral line and the power supply, along with a control circuit that maintains a phase difference in resonant currents and adjusts switching frequencies to prevent harmonic current generation and resonance frequency changes during mode transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the switching frequency is decreased to perform boosting operation when DC input voltage decreases, then the output voltage can be maintained, but circuit loss increases and efficiency decreases
Solution Approach 1:
The patent changes the operating parameters by switching between multi-phase operation mode (for normal voltage) and single-phase operation mode (for low voltage boosting). This parameter change allows the system to adapt to different input voltage conditions while maintaining efficient operation by selecting the appropriate mode based on the input voltage level.
Solution Approach 2:
The patent implements dynamic operation mode switching between multi-phase and single-phase configurations based on input voltage detection. The control circuit dynamically adjusts the operating mode to optimize efficiency across different voltage conditions, preventing excessive circuit loss during boosting operations.
2Power
If the switching frequency is decreased for boosting operation, then output voltage can be maintained, but third harmonic current increases causing efficiency drop
Solution Approach 1:
The patent changes the operational parameters by switching between multi-phase and single-phase modes. When input voltage drops below a threshold, the system transitions to single-phase operation, which fundamentally alters the current waveform characteristics and eliminates the generation of third harmonic currents that occur during multi-phase boosting operation.
Solution Approach 2:
The patent converts the potential harm of operating in single-phase mode (which could cause current imbalance) into a benefit by deliberately using single-phase operation to eliminate third harmonic currents. The control circuit detects input voltage levels and switches to single-phase mode specifically to avoid the harmonic distortion problem that would otherwise occur during low-voltage multi-phase operation.
3Adaptability or versatility
If operation mode switches between multi-phase and single-phase, then adaptability improves, but resonance frequency changes causing instability
Solution Approach 1:
The patent deliberately changes the resonance frequency parameter when switching between operation modes. The control circuit detects input voltage levels and adjusts the resonant frequency accordingly - using a first resonant frequency in multi-phase mode and a second resonant frequency in single-phase mode. This parameter adaptation maintains optimal performance across different operating conditions.
Solution Approach 2:
The patent implements dynamic resonance frequency adjustment based on the detected input voltage level and current operation mode. The system transitions from a static resonance frequency design to a dynamic one where the resonant frequency is adaptively changed to match the operational requirements of each mode, ensuring stable and efficient operation across the full voltage range.
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 design effectively reduces neutral line harmonic currents and maintains resonance frequency stability, enhancing efficiency and reducing transient overshoots during mode switches, suitable for applications like DC current transformers.
Implementation Method 1
a resonant circuit including a resonant reactor connected between a connection point between the first switch and the second switch and one end of the primary-side winding, and a resonant capacitor in which one end is connected to the other end of the primary-side winding
Implementation Method 2
a high-frequency transformer including a primary-side winding and a secondary-side winding
Data Source
AI summary
A multi-phase LLC resonant converter circuit (10) includes: first to third LLC resonant converters each including a series circuit (S1 to S3) of a first switch and a second switch that are connected in parallel to a DC power supply, a high-frequency transformer (T1 to T3) including a primary-side winding and a secondary-side winding, a resonant circuit including a resonant reactor (Lr1 to Lr3) connected between a connection point of the first switch and the second switch and one end of the primary-side winding, a resonant capacitor (Cr1 to Cr3) in which one end is connected to the other end of the primary-side winding, and a divided resonant capacitor (Cn1 to Cn3) in which one end is connected to a connection point of the primary-side winding and the resonant capacitor; a first neutral line (N1) that connects the other end of the resonant capacitor; a neutral line reactor (Ln) connected between the first neutral line and a power supply line of the DC power supply; and a second neutral line (N2) that connects the other end of the divided resonant capacitor.