asdf44
Advanced Member level 4
What are the tradoffs to consider when deciding whether to use coupled differential mode, coupled common mode or discrete inductors for filtering in AC applications.
For example below is the diagram of the winning google little box challenge (DC to AC inverter). All inductors are coupled. On the inverter output why chose to have a common mode followed by a differential mode inductor instead of two discrete uncoupled inductors (which will also block both differential mode and common mode).
Ok I can give an obvious answer: It allows independent tuning and optimizing of the common-mode versus differential mode properties. That makes sense but as I survey parts I see discrete single inductors in more highly optimized packages (like molded). In a case I'm studying now its smaller to have two single molded inductors than a wound common mode choke of similar value and rating. Why not go that way and get another differential stage for free?
For example below is the diagram of the winning google little box challenge (DC to AC inverter). All inductors are coupled. On the inverter output why chose to have a common mode followed by a differential mode inductor instead of two discrete uncoupled inductors (which will also block both differential mode and common mode).
Ok I can give an obvious answer: It allows independent tuning and optimizing of the common-mode versus differential mode properties. That makes sense but as I survey parts I see discrete single inductors in more highly optimized packages (like molded). In a case I'm studying now its smaller to have two single molded inductors than a wound common mode choke of similar value and rating. Why not go that way and get another differential stage for free?