This paper proposes a general approach to design a feedback control law for DC/DC power converters. These last ones can be modeled as switched port-Hamiltonian systems. Based on Lyapunov theory, a candidate Lyapunov function representing the energy of the system is proposed. Advantages of the resulting control law include ease of design and implementation in real time applications. The proposed control is applied in simulation for Buck, Buck-Boost, SEPIC and Ćuk converters. A comparison with a PWM state feedback control law is given for the last two converters.