Low common mode noise transformers and switch-mode DC-DC power converters
A switch-mode DC-DC power converter includes one or more input terminals and output terminals, and a transformer coupled between the input and output terminals. The transformer includes a plurality of winding sets. Each winding set includes a primary winding and a secondary winding magnetically coupled with one another. The primary winding and the secondary winding include the same number of turns. The primary windings of the plurality of winding sets are connected in series and the secondary windings of the plurality of winding sets are connected in parallel. The power converter also includes at least one spacer positioned to separate an adjacent pair of the plurality of winding sets. A magnetic coupling between the adjacent pair of the plurality of winding sets is less than the magnetic coupling between the primary winding and the secondary winding within each winding set.
1. An interleaved LLC power converter, comprising:
one or more input terminals for receiving an input voltage from a voltage source;
one or more output terminals for supplying an output voltage to a load;
a first LLC converter including a first transformer and a first spacer, the first transformer coupled between the input and output terminals, the first transformer including a first plurality of winding sets each including a primary winding and a secondary winding magnetically coupled with one another, the first spacer positioned to separate an adjacent pair of the first plurality of winding sets, the primary windings of the first plurality of winding sets connected in series and the secondary windings of the first plurality of winding sets connected in parallel; and
a second LLC converter interleaved with the first LLC converter, the second LLC converter including a second transformer and a second spacer, the second transformer coupled between the input and output terminals, the second transformer including a second plurality of winding sets each including a primary winding and a secondary winding magnetically coupled with one another, the second spacer positioned to separate an adjacent pair of the second plurality of winding sets, the primary windings of the second plurality of winding sets connected in series and the secondary windings of the second plurality of winding sets connected in parallel.
2. The power converter of claim 1 , wherein each LLC converter includes at least two switches, a capacitor and an inductor, and the switches, capacitor and inductor are coupled between the one or more input terminals and the transformer of said LLC converter.
3. The power converter of claim 2 , further comprising a controller for controlling switching operation of the switches of the first and second LLC converters to operate the first and second LLC converters with one of a forty-five degree phase shift, a sixty degree phase shift, and a ninety degree phase shift, relative to one another.
4. The power converter of claim 1 , wherein the first and second pluralities of winding sets each comprise exactly two winding sets, and a turns ratio of each LLC converter is two to one.
5. The power converter of claim 1 , wherein the first and second pluralities of winding sets each comprise exactly four winding sets, and a turns ratio of each LLC converter is four to one.
6. The power converter of claim 1 , wherein each winding comprises a planar winding including one turn per layer.