A 1-MHz single-switch high-step-up converter with switched inductors is proposed, suitable for high-voltage applications. On the basis of a conventional single-ended primary inductor converter (SEPIC), a switched inductor cell with a pump capacitor and a voltage multiplier unit is added to achieve high voltage gain. The proposed converter works in discontinuous conduction mode (DCM) to realize soft switching. In addition, the switch adopts wide-bandgap semiconductor gallium nitride (GaN) to obtain better high-frequency performance. To further increase efficiency, magnetic integration technology is used to achieve structural integration of the three inductors. An optimized scheme based on a commercial core is determined according to simulation and calculation results. Operational principles and parameter design process are introduced in detail in this paper. A 1-MHz, 200-W prototype operating in DCM with a voltage gain exceeding 13 times has been designed to verify the theoretical analysis. Measured efficiency reaches up to 94.3% at full load.

LLC resonant converters are popular in high-frequency and high-power-density applications with the advantage of excellent soft switching characteristics. Nevertheless, voltage regulation capability is constrained, and additional power losses will be introduced in a wide operating range. A partial-power LLC resonant converter for a wide input range is presented in this article. Two LLC converters are both designed at the open-loop state, performing as a DC transformer (DCX) to realize a constant transformation ratio. System input power is divided into two parts by a series connection of the two DCXs, which is helpful to reduce component ratings. A synchronous Buck-Boost is cascaded with DCX2 to achieve system closed-loop control by pulse width modulation. Most system power is transmitted by DCX1, and a small portion is processed by DCX2, so less power loss will be generated by Buck-Boost. Working principle, parameters optimization, and integration design of magnetic components are introduced in detail in this paper. A 200W 280 V–400 V/48 V experimental prototype with 1-MHz is established to demonstrate the correctness of the theoretical analysis. Peak test efficiency is up to 95.8%, which is improved compared with the conventional two-stage scheme under the same working conditions.