I. Introduction
Power factor correction (PFC) is a widely-used technique [1] that allows an ac-dc converter to meet power quality standards, such as [2]. Low-power converters can benefit from a variety of converter topologies that automatically provide the PFC function, or controllers that exploit discontinuous conduction mode such as [3]. High power converters (e.g., more than 1 kW) are best served with methods that use current sensors, such as [4]–[6]. The present work targets the middle range, where the excessive losses of the low-power techniques are undesirable and the current sensor is too expensive.