I'm guessing that the triangle in the circle represents the Trinity, but I wondered if this type of symbol is common in Lutheran churches, or is something new.
The symbol you are describing sounds like a conflation of the “cross of victory” (Cross above a globe) with a symbol of the Trinity.
If I recall correctly this is something sold through the ELCA church supply & publishing house Augsburg-Fortress.
Traditionally the globe had bands of equal length, like a pair of lines of latitude plus a band of equal length running vertically. The three points of the bands were to represent the Trinity; but I suppose someone felt the symbol could be improved by replacing the bands with the triangle.