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
Junyao Tang, Lei Zhao, Cheng Huang
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].