New AC–DC Power Factor Correction Architecture Suitable for High-Frequency Operation

Abstract

Abstract-This paper presents a novel ac-dc power factor correction (PFC) power conversion architecture for single-phase grid interface. The proposed architecture has significant advantages for achieving high efficiency, good power factor, and converter miniaturization, especially in low-to-medium power applications. The architecture enables twice-line-frequency energy to be buffered at high voltage with a large voltage swing, enabling reduction in the energy buffer capacitor size, and elimination of electrolytic capacitors. While this architecture can be beneficial with a variety of converter topologies, it is especially suited for system miniaturization by enabling designs that operate at high frequency (HF, 3 -30 MHz). Moreover, we introduce circuit implementations that provide efficient operation in this range. The proposed approach is demonstrated for an LED driver converter operating at a (variable) HF switching frequency (3 -10 MHz) from 120 Vac, and supplying a 35 V dc output at up to 30 W. The prototype converter achieves high efficiency (92 %) and power factor (0.89), and maintains good performance over a wide load range. Owing to architecture and HF operation, the prototype achieves a high 'box' power density of 50 W / in 3 ('displacement' power density of 130 W / in 3 ), with miniaturized inductors, ceramic energy buffer capacitors, and a small-volume EMI filter.

Measurements and Performance Factor Comparisons of Magnetic Materials at High Frequency

“…This is equal to 1.5δ at 28 MHz at room temperature in copper, indicating in this case that magnetic materials could be evaluated using F 1 2 for frequencies up to 28 MHz. The lower power of f ( 1 ⁄2 instead of 3 ⁄4) in the performance factor for this case indicates the diminishing value of litz wire over the HF frequency range, and in practice, litz wire is not usually worthwhile above the low end of the HF range (though it has been used effectively in the 5-10 MHz range, e.g., [23], [24]). …”

High-frequency isolated ac-dc converter with stacked architecture

“…1 along with the feedback approach used to provide output voltage control [15]. The system architecture comprises a linefrequency rectifier, a stack of capacitors across the rectifier output, a set of regulating converters having inputs connected to capacitors on the capacitor stack, and a multi-input isolated bus converter that combines the power from the outputs of the regulating converters to provide a single output.…”

“…5. The regulating converter is designed with single switch, diode, and small inductor, and operates around 3 -10 MHz frequency similar to the regulation-stage design illustrated in [12], [13], [15]. It is an "inverted" circuit in the sense that it is designed with "common positives" (i.e., the positive node of the converter's input voltage is common Capacitively-aided Fig.…”

“…5. This figure shows the implementation of the ac-dc isolated converter using a stacked grid interface architecture [15]. The regulating converters are designed as resonant-transition inverted buck converters operating at high frequency, and a multi-input capacitively-aided bus converter is utilized as a dc transformer [16].…”

“…Here we present an isolated ac-dc converter with a stacked architecture [14], [15] and utilizing a inverted resonant transition buck converter and a capacitively-aided isolated bus converter [16] to provide galvanic isolation and voltage transformation. The proposed ac-dc converter addresses converter miniaturization through high-frequency operation while main- taining good efficiency, and achieves reasonably high power factor consistent with line harmonic requirements [5], while dynamically buffering twice-line frequency energy at moderate voltages with large voltage swings [17]- [23].…”