Voltage/Current Regulator

[hawkeye]

This didn't get much love in the LED forum, so I'll drop it here:
I found this device searching the net, and I'm wondering if anyone has used it before.

http://www.st.com/stonline/books/pdf/docs/1318.pdf

I'm going to try and use some Li-Poly batteries to run Luxeons or 5mm with the flip of a switch, and I thought this might allow me to switch in different current/voltage limits by switching the resistors connected to the L200. Who can tell me why this won't work? /ubbthreads/images/graemlins/smile.gif

 

[MrAl]

Hi there hawkeye,

Looks good to me!

You'll have to watch the overhead voltage which is typical
with these kinds of regulators. With this one, it's about
2 to 2.5 volts depending on load current.
Nice thing, it has presettable current limit -- which the
LM317 type regulator doesnt have (voltage mode).
This means you can use it as a Li-ion battery charger
a bit easier than with the LM317.

Looks like it will run a Luxeon too, but you'll need
around 5.5 volts or higher for the input. If the input
falls too low, the output current will drop in spite of
the current regulation set point.

Let us know if you try one out ok?

Take care,
Al

 

[hawkeye]

I'm looking at using a DPDT relay to switch batteries from parallel to series. Series will be 7.2V, parallel will be 3.6V I understand how important current regulation is for the Luxeons, but can I use a series resistor for the 5mm? Or can I use a JFET and diode to make a current regulator for that circuit. If you're right about the overhead, then I don't think the Li-Poly will generate enough Vf for the 5mm set. Where can I find out the Vf for the L200?