1 MHz 48–12 V Regulated DCX With Single Transformer

Abstract

In this article, a 1-MHz-regulated DCX (RDCX) with single transformer is proposed for high-power-density high-efficiency 48–12 V dc–dc conversion. In the proposed converter, a dc transformer (DCX) works at fixed switching frequency to realize isolation and output power conversion and an auxiliary pulsewidth modulation (PWM) converter is applied to realize voltage regulation. The auxiliary dc–dc is fed from the auxiliary winding of the transformer and its output is in series with the input dc source. The output regulation is achieved by regulating the output voltage of auxiliary dc–dc converter. Furthermore, only a small portion of power is dealt by the auxiliary PWM dc–dc converter. Thus, the total efficiency is a little bit lower than the DCX and higher than that of conventional two-stage solution. The operation principle and the design guidelines of the proposed RDCX are presented in this article. A 360 W 40–60 V/12 V dc–dc prototype is built to verify the theoretical analysis and design guidelines. In the prototype, 9.1% of load power is dealt by the auxiliary dc–dc at nominal 55 V input voltage and, at worst case, which happens rarely and the duration is short, 50% of load power is dealt by the auxiliary dc–dc stage. Finally, 97.3% peak efficiency is achieved.