I have built a circuit which contains an integrated power supply stepping down mains voltage to 5v through a transformer, rectifier circuit and a voltage regulator. With a couple of smoothing caps the ripple is (virtually) non existent. I'm using this power supply to power an ATMega168 and a 16x2 LCD display, with a minimal amount of other small components, mainly a voltage divider with 2 x equal value resistors. All works fine, but when I connect the LCD backlight to my power supply, a large amount (1.3v) of ripple appears all over my DC supply which is obviously upsetting my voltage divider. I have searched on StackExchange and also other places to see if there is an easy solution to what I imagine is a common problem, but haven't found anything, so was wondering if you guys could help? What's the simplest way to get rid of this ripple?