How do you guys handle the LED backlight on typical LCDs ? For example, one project I have here uses a nice Optrex DMC16202 display, 16x2. Not too big, just right.
The backlight takes 150mA at 5V, no resistor ... That's a chunk. I have it controlled right now via a 2n3904 to turn it on and off as needed, but it really sucks the power through the regulator, heating it up. A lot.
This particular project is in vehicles, so there's about 12-13V powering it. I think it's possible to switch the LCD backlight power from the direct 12V instead of the regulated 5V, cutting the power through the regulator down to around 70mA or so instead of 220mA. Much better.
Except that it needs a honking big resistor. 150mA at 5V is less than 1W, which is bad enough. Pulling that from 12V is almost 2W. Have to drop 7V through the resistor at that 150mA, and it really heats it up. Even going to larger resistors (220 ohms) it still gets way hot, besides which the backlight is too dim. Forget 100ohms, fingertip sizzle-city ...
Any ideas ?