Single-Stage Interleaved Soft Switching Converter for EV Charging
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Solution Overview
Problem
Conventional battery charging devices for electric vehicles face challenges in minimizing component count, reducing electromagnetic radiation, and achieving high-power charging efficiency due to the use of two-stage methods and electrolytic capacitors, which increase volume and cost.
Innovation Solution
A single-stage interleaved soft switching converter with an interleaving PFC circuit, film-type capacitors, and a totem-pole structure for the switching unit, which integrates power factor correction and DC-DC conversion, reduces components, minimizes low-frequency transformer components, and uses FET switching elements for efficient charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a two-stage method consisting of PFC circuit and DC-DC converter is used, then power factor correction is achieved, but the number of components increases and volume increases
Solution Approach 1:
The patent combines the PFC circuit and DC-DC converter into a single integrated converter stage. The interleaved structure merges multiple switching units with shared components (transformer, capacitors, inductors) to perform both power factor correction and voltage conversion simultaneously, eliminating the need for separate PFC and DC-DC stages while maintaining both functions.
2Power
If a CCM full-bridge converter is used for large capacity charging, then soft switching is achieved, but transformer volume increases due to low-frequency component
Solution Approach 1:
The patent employs interleaved periodic switching of multiple switching units where each unit operates at a higher frequency. The periodic switching actions of multiple units are staggered in time, achieving effective power factor correction and voltage conversion at elevated frequencies that reduce transformer size while maintaining large capacity charging capability through soft switching.
Solution Approach 2:
The patent divides the single-stage converter into multiple interleaved switching units (first, second, third, and fourth switching units) that operate in parallel with staggered switching phases. This segmentation allows each unit to handle a portion of the total power, enabling soft switching at higher frequencies that reduce transformer volume while achieving large capacity charging.
3Ease of manufacture
If electrolytic capacitors are used in conventional chargers, then cost is reduced, but durability decreases and volume increases
Solution Approach 1:
The patent changes the capacitor type parameter from electrolytic to film-type capacitors. This parameter change improves durability and reduces volume while the integrated design and component sharing mitigate the cost increase, achieving a better overall balance between reliability, size, and manufacturability.
4Device complexity
If a single-stage method integrating PFC and DC-DC converter is used, then component count is reduced, but achieving high power density and efficiency becomes more difficult
Solution Approach 1:
The patent uses periodic interleaved switching of multiple units to achieve high-frequency operation in the integrated single-stage converter. This periodic high-frequency switching enables compact magnetic components and high power density while maintaining efficiency through soft switching, overcoming the typical trade-off between integration and power density.
Solution Approach 2:
The patent implements dynamic control of multiple interleaved switching units with adjustable switching phases and duty cycles. This dynamic operation allows the converter to optimize power distribution, maintain soft switching conditions, and achieve high power density and efficiency despite the integrated single-stage architecture.
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 solution enhances power density, durability, and charging efficiency, reduces switching losses, and allows for high-power charging while minimizing the number of components and electromagnetic radiation, enabling expandability and cost reduction.
Implementation Method 1
a link unit outputting a DC link voltage and providing the output link voltage to a battery by charging and discharging the output power of the shaping unit through a capacitor
Implementation Method 2
an interleaving power factor correction (PFC) circuit provided to an output side of the rectifying unit, to control power factor and battery charging and current by single-stage soft switching
Implementation Method 3
a transformer provided between an input side and an output side of the fourth coil of the filter unit, to increase an output voltage of the filter unit according to a turns ratio thereof
Implementation Method 4
through a soft switching technique of a switching unit of an interleaving PFC circuit, a large-capacity charger is possible, and simultaneously, it is possible to cancel a low-frequency component of a transformer
Data Source
AI summary
According to a single-stage interleaved software switching converter, power factor is controlled and battery charging and current are integrally controlled on the basis of a PFC circuit of a single-stage interleaving type so that efficiency of a charging device is enhanced and the cost is reduced. Further, it is possible to remove harmful electromagnetic radiation; enhance power density and durability by using a film-type capacitor instead of the conventional electrolytic capacitor; reduce switching loss by soft switching operation and to reduce the volume of a filter unit; design magnetizing current to be small by removing a low-frequency component of a transformer and to reduce the volume; and perform high-power charging according to the number of windings of the transformer.