A Review of Megahertz Current Sensors for Megahertz Power Converters
Zhen Xin, He Li, Qing Liu, Poh Chiang Loh
Abstract
Within a power converter, multiple currents are usually measured for control, protection, and/or monitoring. They are therefore important sources of information, which must unquestionably be measured accurately to maintain continuous and reliable operation of the power converter. Accurate current measurement has however become tougher with the introduction of wide band-gap (WBG) devices with switching frequency tending toward the megahertz (MHz) range. Because of that, the installed current sensors must have a significantly widened bandwidth. Moreover, they must be nonintrusive and compact, in order not to degrade fast switching characteristics and high power density of the WBG converter. Presently, these features are not collectively obtainable from existing commercial current sensors. Consequently, many new current sensing techniques have surfaced in the literature for usage with the more demanding MHz power converter. These new techniques, some classical techniques, and their hybrid integrations are now reviewed, after overviewing functionalities made possible by current sensors in a power converter. Last but importantly, some future developmental trends aimed at matching MHz current sensors with MHz power converters are described, before concluding the article.