We propose an efficient time-optimal trajectory planning algorithm for an environment with multiple static circular obstacles, which is based on dynamics for differential-wheeled mobile robots (DWMRs) including actuators. This problem is known to be complex particularly if obstacles are present and if full dynamics including actuators is considered. Given a geometric corridor, the proposed technique defines a portion of trajectory between obstacles as a section which is constituted of an arc, out-curve, and in-curve, each with constant control input satisfying bang-bang principle for time-optimization. Then, it designs time-optimal trajectory composed of multiple sections using common tangent between two tangent circles, in which it handles multiple consecutive obstacles without arcs. This method helps to treat complex environment considering dynamics with DWMR's actuators. Simulation results are shown to validate the efficiency of the proposed algorithm.