## 1 Introduction  
The simplified study of allegedly ideal (no losses) DC/DC converters is enough for multiple applications. However, the current need for greater efficiency in generators and power conditioners demands precise models that take non-idealities and, therefore, efficiency losses into account. Bearing this aim in mind, the present work is focused on the search for a general static model of DC/DC power converters (applicable to the three basic configurations: buck, boost and buck-boost). This model is to be analytic (demanding no measurements), intuitive, easy-to-use and realistic, so that the theoretical and experimental results match. The popularity of DC/DC power converters is growing quickly. One of the causes behind this growth may be that these converters are an essential part of renewable energy-based electric generator systems, which are a topical issue [1; 2; 3; 4; 5]. For instance, photovoltaic generators and fuel cells generate unregulated electric power at its output. However, they must be connected to loads with strict voltage requirements or be part of hybrid systems that share buses with necessarily-regulated voltages [6; 7; 8; 9]. DC/DC converters are the power conditioners that enable the aforementioned generators and others to provide regulated power output. Therefore, in most facilities, DC/DC converters are a post-generator mandatory stage. The foregoing means that the overall efficiency of the system up to the regulated-voltage output is the product of the generator and converter efficiencies [10; 11; 12]. Thus, it is of great interest to know the DC/DC converter losses and, from them, its efficiency. Moreover, new power system topologies to improve the energy efficiency are being developed [13; 14; 15]. DC/DC modeling methods have been traditionally divided into two main groups [16]: analytical and numerical. The former are a consequence of the application of physic-mathematical relationships to circuits. They are usually easy to interpret; however, they often lead to such mathematical complexity that renders them impractical. This is the reason for their usual simplification, which makes them inaccurate for many applications. Numerical methods, mainly based on measurements, provide precision; however they may require long running time and provide poor physical interpretation, thus hindering designers' work. The low frequency characterization of DC/DC converters was carried out in 1972. The works [17; 18] can be considered the earliest references to DC/DC converter modeling by means of average continuous time analytical techniques. The result was an equivalent circuit obtained by two circuits averaging in each commutation interval. In this decade, some other works studied the modeling of DC/DC converters from an analytic viewpoint, yet now from a discrete perspective [19; 20]. DC/DC converters modeling in discontinuous conduction mode also arises in the 1970s [21]. In the 1980s, with the aim of increasing commutation frequency, the topologies of resonant and quasi-resonant converters, as well as their models, became relevant [22; 23]. It is in the 1990s when the search for a circuit-oriented modeling methodology led to the suggestion of the use of PWM-Switch [24], a three-terminal structure that contains the active and passive switch (diode) of most converters. However, this methodology has no detection criteria in the model regarding its change of conduction, which makes it difficult to use. Later, a general average state model based on state-variable representation by means of Fourier series was proposed [25]. This method enables natural inclusion of resonant converters. Reference [26] proposes the application of this method to both resonant and PWM converters, substituting switches by dependent sources. Although a generic method, it is not applicable to the converter discontinuous conduction mode, as they include no conduction-mode detection mechanism.