Hello Hendry :)

A SPMS isnt only one method of get 12V/100mA from 230 VAC.

Another method is main supply without any inductor.
Its work with serial capacitor 1uF/400V, any bridge of diodes , and stabilizer on 12V. To prevent from shock or use without any load you can use a Zener Power Diode on out before stabilizer.

A realy important is hazard od electrical shock, because this type of supply is short connected to main.
For prevent is useed any fuse or specjal mass resistor1 conected trought to
Simply Scheme :)
[pre]
-resistor1--capacitor1--Bridge-Zener diode-stabilizer--
***********|_resitor2_|*************|*****************|
************************************|***************load
______________________________________________________|
[/pre]
Capacitor1 - mainly for 100mA/ 12V = 0,68-1uF/400V AC;
Resistor1 - 180 OHM/ 5W;
Resistor2 - 470 kOHM / 1W;
Bridge - 4x1N4003/400V;
Zener Diode - 15V/1W
Stabilizer - LM7812;
Load - 12V/100mA max.;

When you do some short on load you kill a Resitor1 and it is all, when you unplaged main plug from main a Resistor2 will discharge Capacitor1, so you will be secure from connecting plug.

When you connect plug main to main without any load Zener diode will get current on themselves.

This supply is used in charger of camp lamps, simply charger of batteries, somethiems to supply a small power appliances.

[b]
Remember this appliance have a mains every on metal and you should close a cover you before you connect this stuff to main.
Dont work with open cover !!!
[/b]

It main supply is non comercial, because it is critical for live, but some closed apliances used it for example camp lamp with biulded main plugs to connect to main.