Capacitor type in AC/DC converter

[ShmuelGlick]

Hi. I am trying to design the proper input circuit for the LS01-K3B05SS AC/DC converter.
link to datasheet is HERE

Question. The datasheet specifies what looks like a POLAR capacitor on the AC input.

This does not compute. Am I getting something wrong? Aren't polar caps only okay for DC?

Thanks.
Shmuel

[Paul_KD7HB]

Historically, the + on AC caps refers to the metal foil making the capacitor that is closest to the outside of the capacitor.
Paul

[Paul_B]

OK, first let me point out that you cannot use this component for powering any Arduino project that we can imagine since the output is directly connected to the power mains.

Now this capacitor is used as the DC reservoir capacitor for the switchmode converter since obviously the module is far too small to contain such a capacitor itself. The term "Polar" is not meaningful, the capacitor is a standard polarised electrolytic and the positive side is indicated on the diagram. The datasheet gives ratings according to what range of AC (or in fact, DC) input voltages you anticipate operating the device over, so that part of the specification appears a trifle confusing to start with.

If you were to use it with a DC supply, the upper terminal in the illustration must be positive; there is a single rectifier diode between that input terminal and the capacitor terminal included on the module so the capacitor sees only half-wave rectified DC.