Multi-Phase LLC Resonant Converter With Neutral Line Harmonic Blocking
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Solution Overview
Problem
Conventional multi-phase LLC resonant converter circuits experience increased circuit loss and efficiency drop due to the generation of third harmonic currents when the DC input voltage decreases, leading to inefficiencies during load reduction and boosting operations.
Innovation Solution
A multi-phase LLC resonant converter circuit with a neutral line reactor connected between the neutral line and the power supply line, along with a control circuit that switches between multi-phase and single-phase operation modes, to manage resonant currents and reduce harmonic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the DC input voltage decreases and boosting operation is performed by decreasing the switching frequency, then the output voltage can be maintained, but the circuit loss increases and efficiency decreases due to increased third harmonic current
Solution Approach 1:
The patent extracts and eliminates the harmful third harmonic current from the system by introducing a neutral line reactor that specifically targets and blocks third harmonic currents flowing through the neutral line, while allowing fundamental frequency currents to pass through normally. This resolves the contradiction by removing the harmful harmonic component that causes increased circuit loss during boosting operation.
Solution Approach 2:
The neutral line reactor acts as an intermediary element inserted into the neutral line to selectively block third harmonic currents. This mediator component allows the system to maintain boosting capability while preventing the harmful harmonic currents from increasing circuit loss, thus resolving the efficiency problem during voltage boosting.
2Power
If the DC input voltage decreases and boosting operation is performed, then the output voltage can be maintained, but the effective value of resonant current increases more than the increase in DC input current
Solution Approach 1:
The patent extracts and removes the harmful third harmonic current component from the resonant current by using the neutral line reactor to block third harmonic currents in the neutral line. This reduces the effective value of the total resonant current while maintaining the necessary fundamental frequency current for power transfer during boosting operation.
3Adaptability or versatility
If one end of each resonant circuit and power supply line are connected by the neutral line, then switching from multi-phase to single-phase operation mode is possible, but third harmonic current flows through the neutral line during boosting operation
Solution Approach 1:
The neutral line reactor serves as an intermediary component in the neutral line that selectively blocks third harmonic currents while allowing the neutral line to remain connected for operation mode switching. This resolves the contradiction by maintaining the structural configuration needed for multi-phase to single-phase switching capability while eliminating the harmful third harmonic current flow during boosting operation.
4Power
If the switching frequency is decreased for boosting operation, then the output voltage can be maintained when DC input voltage drops, but the resonant current peak value increases significantly
Solution Approach 1:
The patent extracts and eliminates the harmful third harmonic current component that causes excessive resonant current peak values during boosting operation. By blocking third harmonic currents through the neutral line reactor, the system can perform voltage boosting without experiencing excessive current peaks that would compromise reliability.
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 effectively reduces the effective value of resonant and neutral line currents, maintaining efficiency by minimizing third harmonic currents and allowing seamless switching between operation modes.
Implementation Method 1
a neutral line reactor that is connected between the neutral line and a power supply line of one of a positive electrode and a negative electrode of the DC power supply
Implementation Method 2
a resonant circuit that includes a resonant reactor and a resonant capacitor
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) in which a first switch and a second switch are connected in series, the series circuit being connected in parallel to a DC power supply (30), a high-frequency transformer (T1 to T3) including a primary-side winding and a secondary-side winding, a resonant circuit (41 to 43) that includes a resonant reactor (Lr1 to Lr3) and a resonant capacitor (Cr1 to Cr3), the resonant reactor being connected between a connection point between the first switch and the second switch and one end of the primary-side winding, the resonant capacitor having one end connected to the other end of the primary-side winding, and a rectifier circuit (51 to 53) that rectifies output of the secondary-side winding; a neutral line (N1) connecting the other ends of resonant capacitors of the first to third LLC resonant converters; and a neutral line reactor (Ln) that is connected between the neutral line and a power supply line of the DC power supply.