Accelerating EV Charging System Development: New PFC Reference Design Proves Invaluable Tool
The number of electric vehicles (EVs) on our roads is set to increase dramatically in the years ahead, with 323 million of them being in use by 2040 (according to a study compiled by analyst firm Wood Mackenzie). Alongside this ramped up EV production, there will need to be major investments in charging infrastructure. Amongst the places where demand will be at its most acute is within emerging economies, but here the level of technical expertise needed to develop charging stations that exhibit high degrees of efficiency within short the time frames mandated will be very limited.
In response to these dynamics, Toshiba has developed a 3-phase 400VAC input power system reference design which is well suited to the demands of EV charging infrastructure implementations. The RD044-DGUIDE-01 leverages the latest innovations in widebandgap discretes. Requiring only minimal engineering resources, it will help to enable next generation charging station designs to be undertaken in a shorter timeframe.
Featuring power factor correction (PFC) functionality, the RD044-DGUIDE-01 reference design has a power factor greater than 0.99. Using this hardware, initial prototypes can be quickly constructed and their operational parameters examined prior to moving into the production stage. It is able to deliver a 4kW, 750VDC output - with support for switching frequencies of up to 50kHz and conversion efficiencies reaching 97%. As a totem pole configuration is employed in this reference design, each phase is switched directly. This dispenses with the need for a diode bridge rectifier - which would present large losses given the high power figures involved, thereby impacting on the conversion efficiencies that could be derived.
Pivotal to this reference design’s operation is the TW070J120B N-channel silicon carbide (SiC) MOSFET that has been incorporated. The three-phase 400VAC input means that the totem pole configuration needs an elevated withstand voltage for its switching elements (with the capacity to cope with voltages of at least 1000V). Under such circumstances, IGBTs would normally be sourced. However, IGBTs possess slower switching speeds than MOSFETs and have greater switching losses associated with them. By using MOSFETs that are based on SiC, it is possible to benefit from a combination of accelerated switching speeds and elevated withstand voltages. Featuring a built-in SiC Schottky barrier diode, the TW070J120B has a 1200V withstand voltage and a threshold (Vth) of 4.2V to 5.8V. Its on-state resistance is just 70mΩ, which helps to mitigate power losses.
Via the TLP5214A gate driver IC that the reference design also includes, it is possible to alter the switching speed of the MOSFET. This means that the engineer can make adjustments to the switching drive conditions while monitoring the electro-magnetic interference (EMI) effects, so that an optimal balance can be decided upon.
Toshiba has published a white paper describing the RD044-DGUIDE-01 reference design in detail, and showing how it can facilitate the development of advanced EV charging systems. To download it click here:
