To increase the energy efficiency of modern LSIs, supply voltage control techniques (power gating and dynamic voltage frequency scaling) have been widely used and the energy efficiency of fine grain temporal controls in both cases have been discussed. In this paper, we applied dead time constraint, compared the energy efficiencies and formulated the boundary condition that power gating is more energy efficient than DVFS. The formulation is applied to discuss the future trend of energy efficiency using ITRS roadmap and it was found that DVFS would be still effective with high-performance technology, however, it will not be effective with low-operating-power technology.