A MAXIMUM POWER TRANSFER BATTERY CHARGER FOR ELECTRIC VEHICLES

A battery charger is described that uses an on-line microcontroller to maximize its output power. This is done by always operating at either the maximum allowable input current or the thermal limit imposed by t he charger itself. In this case the thermal limit is determined by the junction temperatures of the two main insulated gate bipolar transist ors (IGBTs). Since direct measurement of these temperatures is impract ical, they must be calculated by a computer algorithm that uses variou s on-line measurements. Experimental results for an 8 kW charger indic ate a reduction in the bulk charging time of about 26% when used with a set of NiFe batteries.