Parallel Resonant Converter Current Equalization
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Solution Overview
Problem
In a parallel connection of resonant converters, output currents are not evenly distributed under variable loads, leading to inefficiencies and increased costs due to the need for additional components and space.
Innovation Solution
The method involves measuring the differential current and adjusting the switching frequency of one or both resonant converters to equalize output currents, using a voltage-controlled oscillator and controllers connected to switches like MOSFETs or IGBTs, eliminating the need for expensive magnetic components by using a simple regulation instead of a current-controlled choke.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If resonant converters are connected in parallel with fixed duty cycle control, then modular design is achieved with smaller transformers and lower weight, but output currents are not evenly distributed under variable loads leading to inefficiencies
Solution Approach 1:
The patent applies dynamics by transitioning from fixed duty cycle control to variable duty cycle control based on differential current feedback. The control system dynamically adjusts the duty cycle of each converter's switches according to real-time current measurements, enabling adaptive load sharing that maintains efficiency under varying load conditions while preserving the modular parallel architecture benefits
Solution Approach 2:
The patent implements feedback control by measuring the differential current between parallel-connected converters and using this information to adjust the duty cycle of individual converters. This closed-loop control ensures that each converter contributes appropriately to the total load, preventing one converter from being overloaded while another is underutilized, thus maintaining high efficiency across all operating conditions
2Productivity
If a current-controlled choke is used to equalize output currents, then even distribution of output currents is achieved, but additional space and weight are required for the choke
Solution Approach 1:
The patent replaces the mechanical/magnetic solution (current-controlled choke) with an electronic control solution. Instead of using a physical choke to equalize currents, the system uses differential current measurement combined with duty cycle adjustment of electronic switches. This substitution eliminates the need for additional magnetic components, reducing both space requirements and weight while achieving the same current equalization objective
Solution Approach 2:
The patent changes the control parameter from current-controlled (choke) to duty-cycle-controlled. By measuring differential current and adjusting the duty cycle parameter of each converter's switching signal, the system achieves current equalization without requiring additional magnetic components. This parameter change transforms the control approach from a passive magnetic equalization method to an active electronic control method
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 approach ensures even distribution of output currents and voltages across resonant converters, reducing weight, space, and costs while maintaining high efficiency, as the resonant converters operate with equal loads without the need for additional space or expensive magnetic components.
Implementation Method 1
The resonant converter converts a DC voltage into a single-phase or multi-phase AC voltage, with it typically being operated with an approximately constant load for optimum operation. A resonant circuit usually ensures that the transistors, for example bipolar transistors, MOSFETs, IGBTs and the like, of a resonant converter are switched off when the current and/or voltage crosses zero
Implementation Method 2
a switching frequency is changed in such a way that an output current of one resonant converter under a changing load is equal to the output current of the other resonant converter
Data Source
Figure 1
AI summary
The invention relates to a method for controlling a parallel circuit of at least two resonant converters (1, 2), wherein input currents (ie1,1; ie2,1) of the resonant converters (1, 2) are tapped on the input side and their differential current (Δie) is determined. To generate equal output currents (ia1,1, ia1,2; ia2,1, ia2,2) of both resonant converters (1, 2) under a variable load (6), the differential current (Δie) is supplied to the controller (R1, R2) of a resonant converter (1 or 2) and a switching frequency is changed.