Soft-Switching LLC Converter With Selectable Voltage-Doubling Stage
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Solution Overview
Problem
Conventional LLC resonant converters face challenges in achieving high power density and efficiency over a wide output voltage range for electric vehicle charging, leading to oversizing and increased costs due to restricted operating conditions and component sizing requirements.
Innovation Solution
A soft switching power converter with an isolated DC-DC converter featuring a second stage capable of selectively converting high frequency AC voltage into DC voltage, allowing for adjustable gain and doubling the overall converter gain, thereby accommodating a wide range of output voltages without increasing component size or cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If LLC resonant converter is operated at high switching frequencies to reduce component size, then power density is improved, but switching losses increase and efficiency deteriorates
Solution Approach 1:
The patent changes the operating mode from hard switching to soft switching, fundamentally altering the switching parameters to achieve zero voltage switching (ZVS). This allows operation at high frequencies with minimal switching losses, resolving the contradiction between compact size and energy efficiency
Solution Approach 2:
The patent employs resonant oscillation at the switching frequency to create voltage and current waveforms that naturally zero-cross at switching instants. This resonant vibration mechanism enables lossless switching at high frequencies, simultaneously achieving small component size and high efficiency
2Adaptability or versatility
If LLC resonant converter is designed for wide output voltage range, then adaptability is improved, but component sizing requirements increase leading to oversizing
Solution Approach 1:
The patent introduces a dynamically adjustable second stage that can be selectively enabled or disabled to change the overall converter gain. This dynamic reconfiguration allows the same physical components to serve multiple voltage ranges, achieving wide adaptability without increasing component size
Solution Approach 2:
The second stage is designed to serve dual purposes: it can operate as a voltage-doubling stage for high-voltage applications or be bypassed for standard voltage applications. This multi-functionality allows a single converter design to cover a wide output voltage range without requiring separate component sets
3Device complexity
If conventional LLC resonant converter topology is used, then simplicity is maintained, but gain adjustment capability is restricted
Solution Approach 1:
The patent merges a conventional LLC resonant converter with an additional voltage-doubling stage, combining the simplicity and efficiency of resonant conversion with the flexibility of adjustable gain. The merged topology maintains the benefits of both approaches while overcoming their individual limitations
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 enables a wide range of DC output voltages with high power density and efficiency, effectively addressing the limitations of conventional LLC resonant converters by allowing operation beyond traditional constraints, thus providing a cost-effective and compact charging solution for electric vehicles.
Implementation Method 1
a resonant tank comprising a resonant inductor Lr, a resonant capacitor Cr and a transformer magnetizing inductor Lm connected to each other
Implementation Method 2
an intermediary stage between the first stage and the second stage, wherein the first stage converts the DC voltage into a high frequency AC voltage
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A power converter (102), a control unit (104), a charging device (200) and a method (400) for transferring power to an EV (106) from a power grid are provided. The power converter (102) includes an isolated DC-DC converter (102C) having a first stage (201) converting a DC voltage (Vin) into a high frequency AC voltage (V1ac) having an amplitude V1, an intermediary stage (203) having a high frequency transformer (203A), a resonant tank (204) which outputs a resonant sinusoidal current scaled by the high frequency transformer (203A), and a second stage (202), connected to a secondary winding of the high frequency transformer (203A), including a power conversion switch (S5), four diodes (D1-D4), and two or more capacitors (C1, C2), that selectively converts the high frequency AC voltage (V2ac) of amplitude V2 into a DC voltage (Vo) of amplitude V2 or 2V2.