Auxiliary Supply For EV Charger

Wall boxes/EV chargers mounted in a permanent installation must work reliably under some tough operating conditions like temperatures ranging from -40 to +65°C and susceptibility to overvoltages. In this use case, an overvoltage classifi cation III (OVC III, as defined by IEC 60664-1 and referenced by IEC/EN/UL 62368-1) is required to meet functional and system protection needs. In addition, they must be fault tolerant to avoid catastrophic damage due to wiring errors during installation or failures within the neutral system of the AC grid. Read how RECOM helped a customer design exceptionally-reliable and fault-tolerant EV Charger.

To meet the increasing demand for higher-power charging stations in e-mobility, more of these chargers (a.k.a. Wall Boxes) have to be installed in public areas and private homes. These installations not only face some demanding temperature and overvoltage conditions but must also be fault tolerant.

These devices face widely varying input voltages as they are installed in different configurations of AC mains inputs. Wiring errors and/or failures on the grid can cause catastrophic failures. The most common root cause for a failure scenario is when a 230/240VAC EV charger is accidentally connected to L1 and L2 (across two phases).

Another scenario for overvoltages is a broken neutral connection in a neighborhood transformer. This can cause the voltage on a phase to increase by over 400VAC.

To avoid any damage to the expensive charger, the customer needed to install a control circuit connecting the high-power electronics to the ac mains only when input voltages are within the specified values. This required an auxiliary supply working over an unusual range of 85VAC up to over 500VAC. When specifying this project, the customer could not find such a product on the market.

RECOM was able to offer a compact, standard AC/DC converter module with an input range of 85 – 528VAC and, therefore, able to work under all possible, previously described fault scenarios. In addition, this module was qualified for applications requiring overvoltage classification III.

This converter contains a control circuit measuring the voltages and correct wiring for the high-power stage. If values are within the specified range, the power stage is connected to the mains, and EV charging can commence. If the supply voltage is too high, a fault is reported on the charger (by an indicator), and charging is inhibited until the supply voltage returns to the specified range.

International safety approvals and an integrated EMI class B filter enable easy deployment. Its operation down to -40°C makes it ideal for unheated outdoor applications, such as carports and garages.