This paper proposes a method to improve the efficiency of the P&O maximum power point tracker (MPPT) by reducing the steady state oscillation and eliminating the possibility of the algorithm to lose its tracking direction. A dynamic perturbation step-size is employed to reduce the oscillation, while boundary conditions are introduced to prevent it from diverging away from the MPP. To prove its effectiveness, the proposed P&O is compared with the conventional and adaptive P&O using the Ropp, sinusoidal and ramp irradiance tests. In addition, the performances are evaluated based on a one-day (10 h) irradiance and temperature profile. The algorithm is implemented on a buck-boost converter and benchmarked by the standard MPFT efficiency (eta(MPPT)) calculation. It was found that, for all the tests, the eta(MPPT) of the proposed P&O scheme is increased by approximately two percentage points. Besides, the proposed algorithm does not require any extra hardware components; only several lines of additional software codes are to be embedded into the conventional P&O MPPT control program. (C) 2015 Elsevier Ltd. All rights reserved.