However, with the low speed of the BLDC motor, the winding back EMF cannot reach the voltage across the battery.Moreover, the recovery of energy also cannot be achieved. Due to the presence of inductances in motor windings, these inductances in the motor can constitute the boost circuit. In order to achieve the recovery of energy, we have to raise the voltage on the dc bus through the inductor accumulator. We turn off all MOSFET on the high arms of H-bridge and control the low arms of H-bridge with PWM. Fig. 5 shows the phase relation among the back EMF, the armature current of the BLDC motor, and the switching signals for the bidirectional dc/ac converter, in which there is only one power switch operated within each commutation state. By controlling MOSFET, the whole circuit constitutes a boost circuit. The equivalent circuit of each commutation state [7], [17] is shown in Fig. 6. According to the principle of the volt-second balance, one can conclude that the net change in the equivalent inductor voltage vL is zero over one electric cycle, i.e.,