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There is no such single IC, what you're describing is an entire power supply. Buy one; A 5 volt switch mode power supply should be extremely inexpensive and easily purchased in bulk if needed from a major electronics maker. I have two or three 5 volt 500+ ma switch mode supplies around the house that are smaller than a deck of cards, they're common in cell phone chargers as the 5 volts is more than enough overhead for charging a single Lipoly cell, and is quickly becoming a very solid standard voltage because of USB's widespread adoption. Building your own is probably a really bad idea, unless you think you can do better than the collective applied engineering skill of the cell phone and USB industry =)
There are very are no "common" switched mode power supplies, let alone an IC. And no IC exists for AC-DC converters since they require things that can't be built on an IC. BUt here is a module:
Mean Well has some really nicely priced 5W PCB mountable power supplies. You can find them for ~$13 in single quantities. I'm not sure you're going to find too much less than 5W.
Otherwise you could use a transformer, bridge rectifier (Two dirt cheap 1N400X rectifiers will work if your transformer has a center tap, otherwise go with 4.), two filter caps and a voltage regulator like an LM7805.
At 100mA, you probably wouldn't even need a heatsink for the LM7805. Switched Mode would require a slightly more expensive setup (You'd need an inductor, a switching regulator like an LM2575, and a flyback diode, totalling ~$4 extra). If your input is constrained to 120V, then the LM7805 may be the way to go. At 500mW, you wouldn't even need too big of a filter cap. You could get a 6.3VAC transformer, which would further reduce the size of it (And slightly increase the power wasted by the 7805, but at 100mA, it's not much.)
Texas Instruments UC3843 (used to be Unitrode) series of current mode controllers may work for you. you can use it to control an offline flyback regulator. A Topswitch may work as well.
There are very are no "common" switched mode power supplies, let alone an IC. And no IC exists for AC-DC converters since they require things that can't be built on an IC.
However, to my knowledge (And I just did a quick search) there are no switching regulators capable of taking in over 100V directly. Where it says "AC In", they likely mean the output from a transformer.
As I said, you have 3 choices:
A prefabbed power supply to do it all for you (A little over $10)
A linear regulator like the LM7805. But you'll still need a transformer and rectifier.
A switching regulator like the LM2575. But you'll still need a transformer and rectifier.
At 100mA, your best bet is probably the LM7805, if the efficiency isn't a big concern for you.
Actually a transformerless power supply would do exactly what he wants and very cheaply and efficiently as well. It's just three diodes, two caps and a resistor. There was a long thread talking about them recently. The only downside is no line isolation, so you have to figure out some method of isolating your circuit from your I/O stuff that you connect to the outside world with (optocouplers, etc).
It's not so much isolation from mains voltage that's the problem, it's that there no current limitation without an isolation transformer. If the primary capacitor fails short circuit you're going to have a ball of plasma on your hands.
@speakerguy: Can you give the schematic about your "just three diodes, two caps and a resistor.plus the fuse and optocouper" ??? n i don't want to have a ball of plasma in my hand... Thx
**broken link removed**
The optocouplers would only be used if you had metal connectors on the outside of the project box to connect to other devices. If the device is self-contained then it does not need them.
Bear in mind this leaves your entire circuit live to the mains, everything MUST be correctly insulated, with no sockets or connections to the outside world.
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