Demonstration of Low DV/DT Class-Φ2 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-Phi(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 16V input, the measured conversion efficiency maintains 76.8%-89.5% in the testable load range from 7.4 to 16.8W.

Automated summary

This article presents the frequency-domain-based modified impedance tuning analysis method and its application in the design of a class-Phi(2) dc-dc converter. By adjusting the second-order harmonic voltage, the goal of reducing voltage stresses across the main power devices is achieved. This method enables load-independent zero voltage switching characteristics.