Abstract
Resonant converter topologies have the ability to eliminate switching losses through zero-voltage switching (ZVS), making them well-suited for switching operation in the MHz frequency range. However, these types of converters are traditionally very sensitive to changes in input voltage and power level, making them unsuitable as power factor correcting ac–dc converters. This article presents a thorough analysis of the operation of a class DE converter in order to derive a set of conditions under which it can achieve a constant input impedance over a wide input-voltage range (60–325 Vdc) with a constant output voltage (450 Vdc) and, thus, be operated as a power factor correctional (PFC) converter, while maintaining ZVS across the full range. The operation is experimentally verified under dc–dc operation for different power levels at a series of input voltages within the specified range. The implemented prototype achieves conversion efficiencies of up to 94% and handles up to 105-W power at a switching frequency of 2 MHz and above, while achieving constant input impedance over the full input-voltage range, enabling its use as a power factor correcting converter.
Highlights
The recent years have seen many advances in the field of power converters operating at switching frequencies in the high frequency (HF, 3-30 MHz), or very high frequency (VHF, 30-300 Mhz) ranges [1]–[4]
This paper present a throughout analysis of the operation of a class DE converter in order to derive a set of conditions, under which it can achieve constant input impedance over a wide input voltage range (60-325 V DC) with constant output voltage (450 V DC) and be operated as a power factor correctional (PFC) converter, while maintaining zero voltage switching across the full range
While resonant converter topologies have enabled increased switching frequencies compared to traditional hard-switched topologies, their control is complicated. Through their ability to operate with zero-voltage switching (ZVS), they can achieve high efficiency under the right operating conditions, but they are very sensitive to changes in loading conditions [21]
Summary
The recent years have seen many advances in the field of power converters operating at switching frequencies in the high frequency (HF, 3-30 MHz), or very high frequency (VHF, 30-300 Mhz) ranges [1]–[4]. As the diode-based rectifiers used in resonant converter topologies are inherently non-linear in their input impedance, this means that these topologies are very sensitive to changes in voltage and power levels, giving them a low dynamic range and making them a less obvious choice for AC/DC applications as power factor correctional (PFC) converters. Methods compensating for these non-linearities in order to achieve zero-voltage switching over a wider voltage range has previously been described for the class E converter [23]–[26]. The specifications of the lab prototype is shown in table I and the relation between input voltage and power for three different values of input resistance is shown in fig. 2
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