RobG 1,892 Posted March 13, 2011 Share Posted March 13, 2011 Most of 3.3V LCD displays come with 5V back-light and one way of powering it in such displays is using step up converter. There are many available, like LT1300 from LT or MAX756/856 from Maxim. For my display, I am using LT1300 which requires 4 additional parts only: L1 - 22uH inductor (10uH-22uH will work) C1,C2 - 47uF (47uF-100uF) D1 - 1N5817 Schottky diode JMLB, GeekDoc, zeke and 2 others 5 Quote Link to post Share on other sites
bluehash 1,581 Posted March 13, 2011 Share Posted March 13, 2011 Nice tip! Quote Link to post Share on other sites
cde 334 Posted March 17, 2011 Share Posted March 17, 2011 Current Draw? Quote Link to post Share on other sites
Mac 67 Posted March 17, 2011 Share Posted March 17, 2011 Current Draw? Wouldn't that be the backlight current divided by the smps regulator efficiency? For example, divide a 40-ma backlight current by an smps regulator efficiency of 89% and you get 45-ma. Just plug in the correct values for your particular backlight current and regulator efficiency. Quote Link to post Share on other sites
RobG 1,892 Posted March 17, 2011 Author Share Posted March 17, 2011 From what I can see, quiescent current is 150uA, and then ~300mA under ~75mA load. My meter must be introducing pretty large error, because that would mean efficiency <50%. Also, I will try to increase caps to 100uF and see if I get better results. Quote Link to post Share on other sites
crysthane 0 Posted March 27, 2011 Share Posted March 27, 2011 What should the input voltage of an AC-DC SMPS be? I have built an smps in a simulation programme (Multisim) but when trying to measure the input voltage (which should be the mains 240V AC) i can only get a DC volts reading on the multimeter, when on AC it reads 0V. ______________________ yahoo keyword tool ~ overture ~ traffic estimator ~ adwords traffic estimator Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.