CVCC & LED Driver

Posted by: galaxyelect@gm… on 11/26/2011

I use PI Expert to design power supplies and I found it very easy to use. I now want to design a CV/CC battery chargers and LED drivers. I used a Wizard and I thought it would be easy to design CV/CC battery charger just by selecting Operation Mode to CV/CC because I saw a message saying that "Choose CV / CC mode for constant current output (battery charger.)". However after selecting a CV/CC mode, I did not find any difference in between normal CV Only power supply and CV/CC design. Does it really make a CV/CC design which can be directly used as a constant current supply?

Similarly When I clicked on LED Driver option while running the wizard, it automatically selected CV/CC and claimed that the design is suitable for LED Driving. Does it make a complete LED Driver? Again I did not see any much of a difference in between a normal CV Only power supply and the LED Driver designed by the PI Expert.

Regards,
Smita

hi smitha

for led drivers and battery chargers you need to have custom cc circuit ,

it can be build using transistor as a series pass or any comparator circuit should be used,
comparator circuits for constant current can be obtained form any comparators application notes

Thanks for the update. Can you please send me a simple schematics?

Regards,
Smita

Hi

For now PIExpert won't give you a schematic for battery charger applications (you can use the transformer though).

Depending on power level, accuracy you may be able to use the LNK-II. Assuming that you are at higher power level you may want to check the following examples:

1 - go to slide 49 - This example uses a 3 transistors to achieve low voltage drop on the sense resistor. The accuracy of the CC feedback is dependent on Vbe

2 - go to slide 34 - This circuit is able to work all the way down to short circuit, but the high voltage drop on the resistor may cause excessive dissipation for high current circuits

3 - DER-137 example - this design offers a very tight regulation, and high efficiency, but is more expensive.

I hope this helps you with your project!

your schematic examples have been attached,,,

Dear Vivek,

Thanks for the schematics. Can I use TL431 in place of the zener?

Regards,
Smita

pls make sure the voltage that you are applying.... since the tl431 may not be able to take more than 37v

CVCC & LED Driver

评论