I. Introduction
Ultraflat power converters are increasingly needed for specific future applications, such as, e.g., ultra-flat OLED lamp drivers [1]–[4] or flat screen power supplies [5]. The respective power converters are single-phase power factor correction (PFC) rectifiers, which provide an output power between 20 and 200 W at a constant dc voltage (typically 10–20 V); the total converter height limit is typically 1–2 cm [6].