Demonstration of Low DV/DT Class-Ф2 DC-DC Converter With 50% Duty Cycle

This article presents the frequency-domain-based modified impedance tuning analysis (ITA) method and its demonstration in designing a class-Ф
₂
dc–dc converter with load-independent zero voltage switching (ZVS) characteristics
.
By adjusting the second-order harmonic voltage, a near trapezial drain-to-source voltage (
V
_DS
) is achieved with beneficially reduced voltage stresses across the main power devices. A complete non-iteration design procedure is established. Comparing to traditional ITA design theory, this modified ITA method leads to low
dv/dt
and low
V
_DS
stress, even at 50% switching duty cycles. In addition, thanks to the finite input resistance of the rectifier, the output resonant network and rectifier designed following this frequency-domain method feature the extensive load-independent ZVS characteristic. The 5 MHz prototype aiming for a true short-circuit to open-circuit load-independent ZVS is designed using modified ITA method, assembled, and measured. Under 16 V input, the measured conversion efficiency maintains 76.8%–89.5% in the testable load range from 7.4 to 16.8 W.