Fig. 2. "Average power models" of step-up, step down and "indirect" (or buck-boost) converters The "direct average current" (is the maximum possible common current, that would transfer the maximum possible "direct power" in a loop including the source and the load. That is, the minimum value of input and output currents, as illustrated in 0.b. Then, the "direct power" is the product of this current by the minimum of input and output voltages, as illustrated in (1). Consequently, P diff may be expressed as (2). The internal power (P int) processed by all the components of a power converter is in general higher than P diff (3), especially in isolated converters and most hybrid and SC converters. In general, the internal power is processed by inductors and capacitors, though the power processed by transformers need to be included in any design and optimization process, and in some cases, the power processed by capacitors is transferred in a resonan fashion, so it may be accounted for separately, as illustrated in (4).