The four factors to consider when selecting components for an EV charging station’s auxiliary power supply with CUI Inc

A combination of changing consumer preferences and strong government action is producing astonishing growth in the number of electric vehicles (EVs) on the road. In Europe, 151,573 new EVs were sold in March 2023, 14% of the total of new car sales, up from 11% a year earlier.

This growth in EV numbers needs equally fast growth in the number of charging stations at home, at workplaces, and in public spaces such as on the kerbside and at highway service stations.

For drivers, charging stations are all about the power supplied to the car battery – in time, the most powerful will produce an output of as much as 400 kW.  But there is an important power system hidden from the user: an auxiliary power supply feeds the components that are peripheral to the battery charging power rail, such as a microcontroller, display, LED indicator lights, and power meter.

Unlike the battery charging rail operating at hundreds of volts ac or dc, this auxiliary power supply steps a mains ac input down to typically 12 V or 5 V. This is accomplished in two stages, as the block diagram shows: an ac-dc converter generates the 12 V power distribution bus, and dc-dc converters provide a point-of-load power supply.

So what factors does the power-system designer need to take into account when selecting power-converter modules for this auxiliary power supply?

CUI Inc, which has a richly stocked portfolio of ac-dc and dc-dc converter modules suitable for this application, has long experience of working with charging station manufacturers, and it suggests keeping a close eye on the following factors when evaluating power modules for the auxiliary power supply:

Surge capability – be aware of the Over-Voltage Class (OVC) rating required for the application. Most fast or rapid chargers will need the highest OVC III rating to handle the surges associated with the high-voltage power supplies to which the auxiliary power supply is exposed.

Input-voltage range – ac-dc power converters are commonly specified for use with ‘universal’ mains power supplies. Most charger applications will provide 120 V ac, 240 V ac, or 277 V ac, and thus a power supply rated for an 85~305 V ac input voltage range will be a good choice.

Operating temperature – charging stations are normally outdoors,  and exposed to sun and frost. A power supply with a wide operating-temperature range (-40°C to 85°C) helps ensure that the charging station works in all seasons.

Electromagnetic compliance – EMC circuitry tends to require large filter components. If built into the converter module, an EMC circuit makes design implementation easier, but the converter will be larger because of the filters. Converters without an EMC circuit are smaller, and CUI supplies reference circuits to help the engineer meet the desired level of EMC performance with minimal effort.

Fortunately, CUI’s product range provides the choice needed to meet the requirements of all types of EV charging stations with an integrated and easy-to-implement power solution.

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