Sensorless Current-Sharing Scheme for Multiphase DC-DC Boost Converters

Accurate current sharing is beneficial to realize uniform heat distribution and electrical stresses in multiphase converters. Most of the present current-sharing schemes need many current sensors which increase the cost and decrease the system reliability. To solve this problem, a sensorless current-sharing scheme is proposed to balance the phase currents of multiphase dc-dc boost converters in continuous conduction mode. By converting the inner resistances of inductors and switches to series resistances on the input side, the actual converter model is simplified. Regarding one duty cycle as reference, the relationship between duty cycle and series resistance ratio (SSR) is derived for equal current distribution. After that, two methods are provided to obtain the SSRs. One is based on duty disturbance and the other is based on current measurement. Actually, the phase with largest series resistance is chosen as reference to improve the transient response. Despite phase number, only output and input voltages are measured to achieve output voltage regulation and current balance in the overall control scheme. The validity of proposed scheme is verified on a three-phase dc-dc boost converter.