A low voltage high current EV drive using inverter low side switches as current sensors

In this paper, first, an equivalent scalar dynamic model for the three-phase brushless dc (BLDC) motor is derived to simplify the control of the electric vehicle (EV) drive. Then, an equivalent armature current sensing technique is proposed for synthesizing the three-phase line current by using the low-side switches of the inverter as current sensors. No additional current sensors are required and no extra power loss is generated. Third, the proposed equivalent current sensing technique is dedicatedly integrated with the PWM control for convenient closed-loop torque control implementation. Finally, a prototype EV drive system is constructed by using a 36 V, 100 A, 8-poles BLDC motor and a CPLD. Experimental results show that the proposed EV drive can indeed achieve the desired performance. Moreover, it is seen that with the above simplification and integration, the proposed EV drive controller circuit can be easily integrated into a single chip.