12.5 A 2MHz 12-to-100V 90%-efficiency self-balancing ZVS three-level DC-DC regulator with constant-frequency AOT V2 control and 5ns ZVS turn-on delay

Authors:
Publisher website
Google Scholar
Abstract
Wide input rails (12V to 100V) are common in today's automotive and industrial systems. Miniaturized DC-DC voltage regulators (VRs), which can provide a low-voltage regulated output from a wide input range and deliver a few Watts, are essential in these systems. Wide-input-range integrated VRs, however have difficulty to simultaneously achieve high frequency (HF) operation and high power efficiency. Previous hard-switching (HS) high-input-voltage (HV) buck regulators can only operate at a low frequency of 100s of kHz in order to limit the dominant switching power loss PSW, that occurs at the converter switching node [1,2]. Low-frequency operation however results in using bulky inductors of 100s of μH, significantly increasing the bill-of-material cost and the converter volume. Three-level converters (TLCs) are effective to reduce the required inductance by doubling the frequency at the switching node and allow using lower-voltage-rating power transistors in HV conditions. However, the concern of large PSW in HV conditions would still limit the HS TLC converter to operate in the MHz range. Moreover, the TLC needs the voltage across its flying capacitor to be balanced at half the input voltage; otherwise power transistors could be damaged during operation. In HF HV conditions, the capability of high-speed flying-capacitor self-balancing is even more crucial, but it is not addressed in prior 3-level DC-DC regulators [3,4]. This paper reports a ZVS-based 3-level voltage regulator (TL-VR) to remove PSW in HF and HV conditions, thereby improving the converter power efficiency. A constant-frequency adaptive-on-time (CF-AOT) V 2 control is developed to offer the flying-capacitor self-balancing in the MHz range, ensuring reliable regulator operation with a wide input range. A body-diode-based floating ZVS detection is also proposed to provide nanosecond-scale ZVS turn-on delay and thus enable full-ZVS operation in HF low-duty-ratio conditions.