KAIST Power Electronics Lab.

LDC (Low DC-DC Converter)


In environmentally friendly vehicle, the low voltage auxiliary battery is employed to supply power for the electronics such as headlamps, air conditioner, power windows, and so on. Therefore, low DC-DC converter(LDC) is necessary in HEV to charge the low voltage auxiliary battery from the main high voltage battery. Compared to general industrial DC-DC converters, it should satisfy the performance of vibration and temperature. Moreover, LDC is required to have high efficiency and low cost. In general, phase-shift full-bridge converter is used as LDC because of its zero-voltage switching capability and high efficiency. However, from the point of view of cost, converters without output inductor can be also considered such as two transformer forward-flyback converter.


OBC (On Board Charger)


Environmentally Friendly Vehicles (EFV) essentially have rechargeable batteries that can be restored to full charge by connecting the vehicle plug to an external electric power source. Thus, battery charger is one of the key components of EFV. In general, on board chargers have two-stage structure that consists of a boost power factor correction (PFC) stage and a dc/dc stage. The boost PFC stage controls the shape of the input current to achieve a high power quality with constant current mode (CCM) control or critical current mode (CRM) control. The dc/dc stage, following the boost PFC stage, offers galvanic isolation and precisely charge the rechargeable battries.