Multiphase power converter topology has been widely adopted for Point-of-Load (PoL) converter application. To achieve a high-performance multiphase converter design, several design considerations must be taken into account during the design phase. These factors include but are not limited to high power density (smaller size), fast transient response and equal current sharing which are introduced in Chapter 1. Current sharing, as a key design consideration to ensure reliable operation of multiphase DC-DC converter, is further explored in this work. Equal current sharing control loop is typically required for multiphase converter in order to prevent inductor current saturation and overstressing the devices in certain phases. Several conventional current sharing control schemes are first reviewed in Chapter 2. The major drawback of these schemes is the need for accurate current sensing for each phase, which causes the performance of the current sharing to be highly sensitive to the accuracy of current sensing in addition to increased cost and complexity. To address the need for accurate current sensing, a new digital sensorless current sharing control scheme is proposed and developed in this work. It is based on auto-tuning the duty cycle value for each phase while observing the input capacitor voltage of the multiphase converter. The theoretical basis/observation of the proposed concept is presented and mathematically verified in Chapter 2 followed by an introduction of the operation of the proposed controller. In addition to eliminating all of the current sensors, the proposed controller eliminates the impact of voltage sensing inaccuracies on the performance of current sharing. The simulation verification of the theoretical basis and operation of the proposed controller is performed by using MATLAB®/SIMULINK® software package. The simulation model is introduced and the simulation results are presented in Chapter 3. A proof-of-concept experimental prototype set-up is first introduced in Chapter 4. The design and implementation of the proposed controller are then covered in details. The periodic and continuous auto-tuning operations are demonstrated under both steady-state and load transient conditions. The experimental results are presented and discussed to further validate the proposed controller. Finally, some directions for future work are given.