LLC Resonant Converter Current Balancing With Adjustment Inductors
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Solution Overview
Problem
Existing resonant converters face challenges in achieving large power and high integration due to unbalanced currents among multiple conversion circuits caused by varying transformer excitation inductance.
Innovation Solution
The resonant converter employs adjustment inductors connected in parallel with the primary windings of lower and upper conversion circuits, balancing currents through m+n LLC resonant converters, and using gapless transformers to reduce excitation inductance variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the number of conversion circuits is increased to achieve large power or high integration, then power capacity and integration level are improved, but current balance among conversion circuits deteriorates due to varying transformer excitation inductance
Solution Approach 1:
Multiple conversion circuits (both lower and upper conversion circuits) share a common resonant inductor, merging the resonant tank components across parallel circuits. This sharing of the resonant inductor ensures that all conversion circuits operate with the same resonant frequency and impedance characteristics, thereby maintaining current balance even when multiple circuits are operated in parallel to achieve large power capacity or high integration
Solution Approach 2:
The patent introduces adjustment inductors connected in parallel with the primary windings of transformation circuits to modify the overall inductance parameters. By changing the inductance parameters through these adjustment inductors, the excitation inductance variations among different transformation circuits are compensated, ensuring current balance is maintained across all parallel-operated conversion circuits
2Device complexity
If traditional resonant converters are used, then circuit simplicity is maintained, but achieving large power or high integration is difficult due to current imbalance
Solution Approach 1:
The patent merges multiple conversion circuits in parallel while they share common resonant inductors and switching elements, allowing the system to achieve large power capacity without proportionally increasing the number of independent resonant tanks. This merging approach maintains relative circuit simplicity while scaling up power capacity
Solution Approach 2:
The common resonant inductor serves multiple conversion circuits simultaneously, making it a universal component that performs the resonant function for all parallel-operated circuits. This multi-functionality allows the system to achieve high integration and large power capacity without requiring separate resonant tanks for each conversion circuit, thereby maintaining circuit simplicity
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 allows for easy achievement of large power and high integration while maintaining current balance, reducing the size of the resonant inductor and enabling flexible circuit specifications without rewinding, and supporting multiple output configurations.
Implementation Method 1
a resonant converter that includes a conversion circuit including a resonant circuit, a transformer, and a rectifier
Implementation Method 2
an LLC resonant converter in which the primary winding and the resonant capacitor are connected between the other end of the resonant inductor and the negative electrode of the DC power supply
Data Source
AI summary
m lower conversion circuits (101 to m) configuring an LLC resonant converter that operates by on and off operations of an upper switch element (QH) and a lower switch element (QL) together with a resonant inductor (Lr) is included. n upper conversion circuits (10m+1 to m+n) configuring an LLC resonant converter in which a primary winding (T1) and a resonant capacitor (Cr) operate together with a resonant inductor (Lr) by the on and off operations of the upper switch element (QH) and the lower switch element (QL) is included. A lower adjustment inductor (Lpd) connected in parallel with the primary windings (T1) of the m lower conversion circuits (101 to m) and an upper adjustment inductor (Lpu) connected in parallel with the primary windings (T1) of n lower conversion circuits (101 to m).