A 68.3% Efficiency Reconfigurable 400-/800-mW Capacitive Isolated DC-DC Converter with Common-Mode Transient Immunity and Fast Dynamic Response by Through-Power-Link Hysteretic Control

Abstract

Galvanically isolated voltage regulators (GIVRs) are widely used in industrial automation, electric vehicles, and medical devices to deliver power to low-voltage circuits across isolated domains and ensure human safety and device reliability in hazardous environments. Traditional bulky transformer-based GIVRs can deliver 2W output power with 80% peak efficiency [1]. However, transformers are relatively expensive, and their size limits the overall physical size of the system from being further minimized. Inductive GIVRs using micro transformers have been introduced in [2]–[9] with a significantly reduced form factor; however, their efficiency is also significantly compromised to around 50% [2]–[4], or even lower in the 7-to-40% range [5]–[9]. This is mainly due to the much lower quality of the micro transformers compared to traditional ones, as well as the associated much higher switching frequency. In addition, the manufacturing/packaging may introduce extra cost due to the need for special processes [2], [3], [5], [6]. A capacitive GIVR has been introduced in [10]; however, the efficiency is also limited to 50.7%, with a maximum power capacity of only 62mW. Besides, common-mode transient (CMT) immunity (CMTI), which ensures the robustness of operation when fast and strong voltage transients happen between the isolated domains due to current/voltage spikes in motor drivers or other fast switching applications, is an important specification for galvanically isolated devices [2], [4], [8]. This is especially important for capacitive designs due to the direct capacitive links between the two domains. However, no discussions, mitigations, or measurements were provided in [10]. In addition, most state-of-the-art designs require an extra transformer [2], [3], [6] or a pair of capacitors [4], [10] to establish feedback links for voltage regulation, which also increase the cost and form factor, or they only work in open loop [5], [7], [9].