Sub Nav Vehicle Electrification

Display portlet menu

Rising EV Demand Drives Onboard Charger Discussion

As the number of electric vehicles (EVs) on our roads increases, the pressure to expand the existing charging infrastructure will also increase. Ideally, this expansion should exceed the current ratio of EVs to charging points and achieve a maximum of no more than 10 EVs per charging point (PCP). Range anxiety is still seen as an obstacle, preventing potential EV owners from transitioning to e-mobility. Increased proliferation of charging points will be a crucial reassurance in the future EV landscape. In this article, we will outline the various charging systems and focus on the principal semiconductor solutions that help control and distribute the power needed within them. We will outline the role that onboard chargers (OBCs) have to play, and discuss how future trends and advancements in EV charging are facilitating the wider worldwide adoption of the EV.

Currently, the principal ways of charging an EV involve a physical connection.

 

Charging Level Description
Level 1 Charging The vehicle is plugged in overnight, with power sourced from a regular single-phase household plug socket; charging takes place at a low rate of 2.3kW , via the vehicle’s onboard charger, which equates to approximately 11 kilometres of e-mobility per hour of charge. This assumes a HV battery capacity of 50kWh with a range of 250km on a full charge. A one-hour charge at 2.3kW represents 4.5 % of the vehicle’s total charge capacity and will therefore cover 4.5% of its range i.e.11.25 kilometres. An enhancement to this method uses a 32A , dedicated outlet; this charging method can be at a more respectable 7.4kW , again via the vehicle’s onboard charger, which equates to 35 kilometres of e-mobility per hour of charge . Home charging suits people who use their car for the daily commute, as they can ensure it is adequately charged for the next day, or even, with a 32A supply, complete an entire recharge cycle. Additionally, intelligent products feature bi-directional charging and use the stored energy in the car’s main battery to supplement the grid in peak demand. They are facilitating a greener grid.
Level 2 Charging Charging stations can be wall mounted in a residence, in a public or workplace car park. They charge, via the car’s onboard charger, at a rate between 7.4-22kW, which equates to 106 kilometres per hour of charge.
Level 3 Charging Alternatively, the vehicle is charged on an ad-hoc basis, using a dedicated DC charging station situated at a garage forecourt-style charging area, usually in a busy traffic corridor. DC charging stations can provide much faster charge rates, as their source is usually a 3-phase industrial AC supply. They feature an in-built off-board charger and directly interface with the vehicle’s battery management system. Depending on the state of charge and the make of the car, they can deliver 50-350kW of power, which means they are likely to complete a charge cycle in an hour or less, which, in our example, equates to 250 km per charge.

Components

Considering the charging current required at Levels 2 and 3, excellent connectivity and low electronic resistance are critical factors in its delivery. The selection of power semiconductors with low “On state” resistance limit heating effects and maximise efficiency. Silicon carbide (SiC) MOSFETs are ideal for this application; they feature an ultra-low “ON state” resistance, high voltage ratings and high-speed switching. 

Avnet Silica’s extensive portfolio of automotive-qualified components includes SiC devices from STMicroelectronics, Onsemi, Navitas and Rohm. Also, next-generation power ICs from Navitas. These ICs combine several power electronic functions built into one gallium nitride (GaN) chip.

Onboard chargers

Onboard chargers are a vital feature of the EV ecosystem. In use, the vehicle could charge at Levels 1, 2, or 3 in any state of charge. The EV uses a single multi-way charging port for all charging scenarios. The first two charging scenarios (Levels 1 and 2) employ the vehicle’s onboard charger to safely convert the incoming AC voltage into a suitable DC charging voltage for its batteries.

The batteries used in an EV are valuable assets. The charging and management systems to which they are connected must ensure they retain their capacity for as long as possible and aren’t pushed to early failure by overcharging. Different charging regimes are employed, depending on the cells’ state of charge (SOC); the battery management system (BMS) provides the control signals. Constant current charging is very efficient and fast; however, it will likely overcharge the batteries at the end of the charging cycle. Conversely, constant voltage charging can overcharge the cells at the start of the charging cycle. Therefore, the onboard charger can alter its charging regime accordingly. The onboard charger is part of the vehicle. Its size and weight influence the vehicle’s range, while its current dissipation capabilities influence the potential charging speed (Levels 1 and 2).

Ready to get started on your next Automotive project?

With decades of experience in working with a plethora of clients across EMEA, our Automotive experts are on hand to support you every step of the way, or whenever you need us.

Get started

Design Hub

The Avnet Silica Design Hub is the one-stop destination for your design and engineering needs. Design Hub information and solutions improve your time to market and help solve time-in-market challenges. Browse the hundreds of proven reference designs.

Learn More

OBC advancements

The use of advanced semiconductor technology, SiC MOSFETs, and GaN wide band gap (WBG) FETs and ICs has increased the capacity of OBCs from 3-5kW to 6-11kW, whilst retaining their current size and weight. Several automakers have adopted these more efficient OBCs in their designs.

There is likely to be an increase in the number of vehicles based on platforms employing 800V DC architecture, as opposed to the 400V used currently, to increase power density and reduce charging times further. The high voltage within these platforms reduces internal current flow, resulting in lighter motor windings, wiring and interconnections, increasing the vehicle’s range capability - the reduced current flow and heating effects during charging decrease charge times considerably. The demand for SiC MOSFETs has increased, as they provide the high voltage tolerance and isolation that such voltages need. GaN FET components, covering different voltage ranges, complement SiC MOSFETs in automotive designs. GaN devices are suitable for lower voltage ranges but have a lower switching loss when compared to SiC devices. Research into gallium oxide (Ga203) and other ultra-wide band gap semiconductor materials is ongoing.

Wireless charging technology, which would significantly enhance the experience of owning an EV, is in development and currently out of reach of the consumer. However, it will likely come into operation for luxury vehicles, taxis and “for hire” autonomous vehicles as early as 2024. Once the technology finds its feet and is produced in sufficient numbers, it could find its way into our homes.

Conclusions

As the number of EVs on our roads increases, improved charging times and expanded charging infrastructure are critical elements of the future EV landscape. Available charging points must exceed the current provision to allay range anxiety fears and encourage the broader adoption of EVs. The pace at which new technologies are being developed and employed is unprecedented. Carmakers face many challenges in incorporating these new technologies into their designs. Conversely, there are new opportunities for external partnerships and start-ups. The advent of high-voltage platforms (800V) will reduce charging times considerably. However, facilitating these higher voltages will require further modifications to the charging infrastructure. Wide-scale deployment of SiC MOSFETs and GaN FET semiconductors will permeate the off-board chargers featured in the electric vehicle supply equipment (EVSE) charging points and the OBCs on the EV. A unified charging infrastructure standardised within a country and harmonised across its borders will significantly enhance the e-mobility landscape.

Featured Supplier

STMicroelectronics

French-Italian multinational STMicroelectronics manufactures a broad portfolio of semiconductor and discrete technologies. Their portfolio includes analog, discrete, digital logic, memory, ARM based microcontrollers, power management ICs and more.

See Solutions

Featured Supplier

onsemi

onsemi is a preferred supplier of high performance silicon solutions to customers in the computing, communications, consumer, automotive, medical, industrial, and military/aerospace markets.

See Solutions

Featured Supplier

Navitas

Navitas is the only pure-play, next-generation power-semiconductor company, founded in 2014. GaNFast™ power ICs integrate gallium nitride (GaN) power and drive, with control, sensing, and protection to enable faster charging, higher power density.

See Solutions

Featured Supplier

ROHM

ROHM Semiconductor designs and manufactures integrated circuits, semiconductors and other electronic components for the consumer electronics, mobile phones and networks market, as well as for automotive electronics and other applications.

See Solutions