A Resonant Dual Extended LC-tank Dickson Converter with 50% Two-Phase Operation at Odd Conversion Ratios

Abstract

This paper describes a resonant Dickson-based topology that achieves complete soft-charging with two-phase operation and a convenient 50% duty cycle at all odd conversion ratios. A brief analysis is presented that shows how the resonant switching frequency can be calculated as a function of inductor and capacitor values. One solution sets all capacitors and both inductors equal, and results in switching devices experiencing a constant blocking voltage that is largely independent of load and fly capacitor voltage ripple. The requirement for capacitor matching and subsequent low capacitance density C0G dielectrics is compensated by a weakly bounded voltage swing: no switching devices are present on intermediary nodes connecting L and C elements allowing for very large voltage ripple and highly effective utilization of each fly capacitor's energy density. A discrete 1:5 prototype validates the proposed topology with measured waveforms illustrating 50% two-phase operation and a load-independent maximum blocking voltage across switching devices. An output power of 129 W with a 94% peak efficiency was measured for an input voltage of 20 V. Measuring 11.45 mm × 12.95 mm × 2.8 mm, this prototype achieves a very high power density of 311 kW/liter (5,096 W/inch 3 ) despite the use of diodes for simplicity and 66% of the converter's volume being comprised of PCB and free space.

Large Signal Analysis on Variations of the Hybridized Dickson Switched-Capacitor Converter

“…As an indirect tank structure, voltage ripple is largely hidden from adjacent switches, allowing for large flying capacitor ripple and very high energy density utilization in practice. As noted in [7], high dv/dt ringing may occur during one of the phases due to the absence of a low impedance path to ground. If component mismatch or unwanted parasitics inhibit complete SSL mitigation, an increased switching frequency and phaseshifted operation similar to [4], [8] may achieve complete soft-charging in addition to ZVS, at the expense of increased circulating currents and reverse conduction losses.…”

“…1(b)-(e)) have also shown promise, with flying capacitor voltage ripple largely hidden from adjacent switches, leading to reduced switch size in practice [31]. As a result, these structures allow for very large ripple, with [7] demonstrating flying capacitors being exercised over almost their entire dielectric range. In addition, the dielectric barrier of resonant tanks may find a two-fold use in capacitively isolated designs [41], [42].…”

“…(b) S-2L-tank. Recently introduced in [7], this variant is the reduced form of the MMSCRC [44]. Two-phase switching is achievable only at odd conversion ratios, however, the second inductor provides an additional degree of freedom that allows all flying capacitors to be equal in value while also enabling a convenient 50 % duty cycle.…”

“…Equations ( 15)-( 19) are underdetermined and one further constraint must be obtained relating to the inductor and V L . How this is achieved is different for fixed-ratio versus chopped PWM topologies, but for fixed-ratio 2-phase converters it can be shown that the inductor must experience zero volt-seconds within each phase 7 . Therefore, inspecting Phase 1 (Fig.…”

“…Eight fundamental variations of the HSC Dickson converter using either one or two inductors to achieve complete SSL mitigation. (a), (b), (c), (g) and (h) are discussed in [6], [7], [8], { [9], [10]} and [11] respectively, while (d), (e), and (f) are proposed here. Red and blue coloring indicates switches active during the primary two phases.…”