SLiMDO: A Single-Link Multi-Domain-Output Isolated DC–DC Converter With Passive Magnetic Flux Sharing for Local Energy Distribution and Rx Behavior Sensing-Based Global Power Modulation

Abstract

This article introduces a small form-factor single- link multi-domain-output (SLiMDO) isolated dc–dc converter design. The proposed design provides two regulated outputs in separate domains in the receiver (Rx) side with a single micro-transformer. These isolated Rxes achieve local voltage regulation and automatic energy distribution across domains through passive magnetic flux sharing (PMFS) without any shared controllers or communication links for coordination. The transmitter (Tx) achieves global power modulation by sensing Rx behaviors through the reflected impedance without using dedicated digital isolators as data links, thus enables closed-loop control with a fast transient response. The SLiMDO converter prototype consists of one Tx chip and two identical Rx chips for two outputs, all fabricated in 0.18- µm CMOS using 3.3-V I/O devices. The micro-transformer is fabricated in standard flexible-printed-circuit (FPC) with 8 mm diameter and 0.13 mm thickness. The isolation level of the transformer is measured to be >5 kV between Tx and Rx and >3 kV between Rx and Rx. The SLiMDO operation is verified in measurements converting a 3.3-V input from the primary domain to two outputs from 1.8 to 3.3 V each located in separated isolated secondary domains, with a 62.6% peak e fficiency at ∼600 mW, a 1.13-W maximum power, and a decent load transient response.