FSAR001 AC to 5volt DC regulator
schazamp built an FSAR001 experimenter board:
This device, remember, takes 80-265Vrms wall power and puts out a (relatively) clean 5V DC. According to the datasheet, the way this thing works is by monitoring the voltage of the AC waveform and charging a big electrolytic capacitor during the low voltage segments on the leading and trailing edge of the (half-rectified) wave. The controller then discharges the capacitor to sustain the 5V DC. It claims it can handle a maximum load of 35mA
Be careful working with unisolated AC voltage, that stuff will kill you in an instant. We don’t do it.
Via the forum.
This entry was posted in power supply and tagged experimenter board, FSAR001.
Comments
The only way you’d ever want to use this on a project is if it is in an enclosed box of some sort whereby NOBODY and I mean NOBODY can get to it while it is live.
I’ve thought about using it on a project and found that it is cheaper to get a transformer than to get all the caps and parts required especially as the Amps required go up above the magical threshold of about 45 mA at which point the caps become so big it becomes insane to do it.
Here is some reading on the matter: http://www.zen22142.zen.co.uk/Circuits/Power/tps.htm
http://web.archive.org/web/20071117132256/http://uk.geocities.com/ronj_1217/tless.html
It is very interesting, and could be useful for some of you out there, just be extremely careful like Ian has stated!
Yikes. Dangerous Prototypes indeed :)
Still, I can think of a few legitimate uses for it. It could be used to provide startup power for an SMPS instead of a bootstrap resistor, and it could be used in gear that monitors/controls the line voltage like a kill-a-watt meter or a PWM dimmer circuit. Definitely it needs to be enclosed and isolated, and any signal in/outputs (like a serial port) need to be opto-isolated.
A bit more safely you could use it on the secondary side of a medium voltage power transformer. For instance if you have an amplifier that has a 50 VCT transformer you could hang this off the secondary to get some power for electronics rather than using a linear regulator on the +/- 35 volt DC rails.
These unisolated line to DC supplies are fairly common in consumer lighting to run microcontrolers. See the Atmel AVR ap note 465:
http://www.atmel.com/dyn/resources/prod_documents/doc2566.pdf
for some design guidelines for the classic cap/resistor/diode solution that this fairchild product replaces. Looks like a neat replacement for that, although I only see it in a DIP-8, not an SMT part. Might even be cost effective (and anyone doing this is doing it in production) since the capacitor you need for the classic solution is large and expensive since it needs regulatory cert.
Anyone designing these types of supplies should already know about, own and use an isolated variac.
Oh, if you use the design from the AVR465, you need to simulate it in something like LTSpice. There are a few different topologies for the circuit depending on where you put the zener diode and the simulation will tell you where the energy is going. It’s not obvious unless you were really paying attention when you took “Circuits and Electronics”.
Replacing this by a 0.7$ costing mobile charger’s internal board will be the safe and cheap solution. That outputs +5V power at 200mA.
Just use a mylar cap, an a few other small parts and you have the same thing. There are millions of little direct line-powered products sold World wide that use this approach. Or maybe this part provides some form of isolation?
I have no idea where you found this chip — I can’t find it *anywhere*.