New Industry Products

Reference Designs Power 2- and 3-Wheel EV Chargers

December 23, 2023 by Mike Falter

Battery charger reference designs from Transphorm offer high power density at a competitive cost for two- and three-wheel electric vehicles using the latest SuperGaN FET technology.

Transphorm Inc. has released two power supply reference platforms ideal for charging the two- and three-wheel electric vehicles (EVs) widely used in China, India, and other rapidly growing international markets.

 

Electric scooter.

Electric scooter. Image used courtesy of NIU

 

The reference designs use Transphorm’s latest gallium nitride (GaN) SuperGaN technology to deliver high levels of power density at a competitive price point for high-volume, emerging market applications like electric motorcycles and scooters.

 

300 W EV charging reference platform.

300 W EV charging reference platform. Image used courtesy of Transphorm

 

To achieve performance, the reference designs use a lithium-ion battery charging method with constant current/constant voltage (CC/CV) to deliver 300 W and 600 W of charge power, respectively, at a bus voltage suitable to smaller e-mobility platforms.     

 

International e-Mobility Markets

The market for two- and three-wheel EVs in China and India is large and growing, with nearly 60 million vehicles sold yearly across the two markets.

 

Three-wheel taxi in India.

Three-wheel taxi in India. Image used courtesy of Unsplash

 

According to Tushar Dhayagude, Vice President of Worldwide Sales at Transphorm, the company’s SuperGaN solutions have gained traction in two- and three-wheeler EV markets due to GaN’s high power density and relative affordability compared with silicon carbide and silicon solutions.  

 

Constant Current/Constant Voltage (CC/CV) Charging

With constant current/constant voltage (CC/CV) lithium-ion battery charging, the platform delivers a constant current during the initial stages of the battery charge, transitioning to constant voltage regulation toward the end of the charge cycle to allow for a full battery charge without exceeding any limits.

Following the power factor correction (PFC) stage, the reference designs use a resonant LLC topology designed to accommodate the wide output voltage ranges that can occur when charging a battery with a constant current.       

 

LLC resonant converter topology.

LLC resonant converter topology. Image used courtesy of TI

 

While the math defining the gain characteristics of a resonant converter can be complex, using a resonant LLC circuit at the input of the DC-DC converter offers many design advantages over traditional approaches, including fewer component counts and higher conversion efficiencies.

 

Simplifying Charger Design

To simplify charger design and reduce development time and resources, the reference designs use an MPS (monolithic power systems) PFC and LLC combo analog controller (HR1211) without firmware. Eliminating firmware has the added benefit of reducing the platform cost of ownership by scaling back software maintenance costs.

 

PFC and LLC resonant converter combo circuit.

PFC and LLC resonant converter combo circuit. Image used courtesy of MPS

 

Off-the-shelf FET drivers (from onsemi), well-matched through circuit design techniques, are used to drive the SuperGaN FETs. This eases a major design challenge for engineers working with high-performance GaN circuits that typically require more sophisticated drive circuits.

 

Performance and Specifications

Developed from repeated customer requests, the charger reference platform accommodates AC line inputs up to 264 V and can deliver up to 11.4 A (600 W platform) of constant charge current across a voltage output ranging from 34 to 58 VDC.  

 

EV charger reference design specifications.

EV charger reference design specifications. Image used courtesy of Transphorm

 

Each reference design is constructed using three SuperGaN FETs operating at switching frequencies up to 150 kHz and delivering power conversion efficiencies as high as 95%.

 

Other Applications

In addition to EV chargers, the AC-DC supply reference designs can be used for other applications, including LED dimmable drivers, gaming consoles, and high-performance laptops.