Converters for the self-sufficiency of EV charging stations

In a world that has to reduce its carbon footprint, electronic vehicles are the future of traffic. They need charging stations whose power levels are in the region of several kW. They are equipped with the latest semiconductor technologies and they are being improved continuously. At the same time, the AC/DC accessories supplies need to be adapted and developed further so that they reach the same requirements for quality and deliver appropriate efficiency. In addition to that, there are high expectations with regard to insulation strength against overvoltage and to robustness during voltage dips on the network. Charging poles are often freestanding and therefore, when lightning hits nearby, this can cause transients. These supporting power-supply units need to withstand them.

The RECOM delivery program contains AC/DC provision as power supply, as well as DC/DC converters with galvanic or increased potential isolation and also very high insulation strength.

The 5W range RAC05-K/480 is an OVC III classified AC/DC converter with a very wide 85VAC to 528VAC input voltage range, which allows 100VAC to 277VAC for a phase-to-neutral connection in the single phase system or a 208/480VAC phase-to-phase connection in the three-phase system without a neutral conductor. The 5V, 12V or 15V outputs are specified with an insulation strength of 4kVAC for one minute. The RAC05-SK/480 has an operating temperature of -40 to +80°C and is therefore ideal for use in exposed environments such as charging stations.

For a better performance, the RAC10-SK/277 series can be used as an auxiliary supply. The input voltage range spans from 85VAC to 305VAC, which is suitable for single phase connections from 100VAC to 277VAC. Just like the RAC05-05SK/480, the RAC10-05SK/277 is also OVC III compliant. These cost-effective components, which are certified for industry and household (IEC 60335) are available with output voltages from 3.3VDC to 2VDC and ±12VDC or ±15VDC, and therefore cover nearly all applications. A special feature is the momentary overload capacity of 140%, which makes them ideally suited to accessory supplies in battery-charging and monitoring systems with higher inrush currents.

Both of these series comply with EMV-standards (class B) without external filters, have a low idle-running and standby consumption, and have a space-saving 2“ x 1“ footprint for board mounting.

Another series are the DC/DC converters with a potential separation. The RxxCTxxS is a 5kVAC insulated DC/DC converter (1kVAC,rms working voltage) with reinforced insulation, but in a very low overall height SOIC case. Thus, the converter can be treated like any other IC and can be soldered in. The regulated output voltage is short-circuit-proof and can be chosen with 3.3VDC or 5VDC. The 500mW performance is more than sufficient for sensor or communication interfaces. The operating temperature range is very wide and ranges from -40°C to +110°C with 400mW load and 5VDC input voltage.

The RKE series is constructed more conventionally (SIP7, THT), but it has a higher 1W output voltage and the lower price adapts well to cost-sensitive appliances. 5V, 12V or 24VDC input voltages are available. The 5 VDC output voltage has a high insulation strength of 4kVDC. It can be used for the supply of electrically isolated interfaces, or for the supply of controller or sensor electronics, for example for charging current monitoring or battery voltage. The RHE converter covers an efficiency of up to 81%. In case the circuit board which it is attached to has not been interference suppressed, a small EMC filter has to be added (LC).

Both DC/DC converter types can be used advantageously in battery chargers and in chargers for vehicles or in the so-called “wallbox”. They can also be used as a charger for everyone at home and in many industrial applications where a stronger electric isolation is necessary.

There are also EV charging stations for 48V batteries. They are used for smaller electronic vehicles, like driverless transportation systems (AGVs – Automated Guided Vehicles), material handling, compact cars like golf cars, or as charging stations for plug-in-mild-hybrid (PHEV) cars. The DC voltage stays below 60 VDC, therefore a security electric isolation is not required and a non-insulated converter can be used, which is more compact, more efficient and more cost-effective than an insulated converter. The RBBA3000 is one of these converters. Input voltage can lie between 9V and 60VDC, but the programmed 0-60VDC output voltage stays stable with a load of 0 – 50A. This corresponds with a performance of up to 3kW in a compact half brick format (63.2 x 60.6 x 13mm). Another advantage is the Imon pin, which makes a monitoring of the load current possible without the need for a shunt resistor (current shunt). Other areas of application are 48V to 24V or 12V to 24V battery power conversion, battery voltage stabilisers or high capacity power lab DC power supplies. With appropriate cooling, the full performance spans operating temperatures of -40°C to + 85°C. Like all the aforementioned products, the converter is produced with a two-year warranty which is always granted by RECOM.