The article studies the behavior of a mixed parallel-series connection of piezoelectric oscillators attached to the standard interface for wideband energy harvesting. The estimate of power output is obtained analytically considering the formulations of balance of charge, energy and system dynamics. It can be presented based on the generalized matrix formulation of charging on capacitance in terms of equivalent load impedance. The proposed model is subsequently validated numerically through circuit simulations. Finally, a design with a careful choice of parallel-series mixed connection of oscillators is proposed for illustration. With a proper circuit layout triggering the switching of connection, the result shows that the peak power of each array configuration is roughly uniform within the frequency range of interest. Hence, the bandwidth is enlarged without the loss of peak power.