Boundary controls for switching power converters are well known to provide fast dynamics, immunity to circuit parameter variation, and simple operation. The basic principle of the boundary control builds on a state-space representation of a switching power converter and depends on the intra-cycle information of inductor current, capacitor current, or capacitor voltage. Thus, high resolution requirements for the intra-cycle information of state variables are vital to inherit the merits of boundary controls and avoid chattering. For the guidance of the boundary control design, this paper gives comparative evaluations on three high resolution sampling schemes. Following that, an 110Vac/60Hz inverter prototype with the digital boundary control with second-order switching surface has been built to validate the feasibility.