I am sure many of you are familiar with the newer higher-power SMT LED's that are out. They generally require larger copper pads on the PCB to dissipate heat.
I am working on an application where I need a lot of brightness, and very small size. I also need to have my design be dual color (for example red and green). My solution was to put the LEDs in strings of three, side by side but oppositely biased to one another. So that if V
- is on the left and GND on the right, its red, if V+ is on the right and GND on the left, its green. Since red and green would never be on together, this allows me to use the same copper for power dissipation on both strings.
I was originally using an H-bridge to swap the polarity. But the design has turned into 6 strings of 3 for red and 6 stings of 3 for green. Six h-bridges... I am trying to keep the board as small as possible and I am running out of room doing this with discrete components.
Of course they make motor drivers that are H-bridges built in, but they are expensive and overkill for what I need. If I had my wish come true, it would be for a small chip with 5 or so pins... power and ground in, a control line, and to outputs. If control is low, output
1 is V+ and output 2 is ground, and if control is high, output 1 is ground and output 2 is V+. Does such a beast exist?If not, is there any other suggestions on how to tackle this? I could do away with the h-bridge idea and just parallel the strings of LEDs, mass the cathodes (since that's where heat dissipation is needed) and seperate the anodes and control via transistors switched from the microcontroller, but I am not sure if that is the best way.
As a non-professional designer, does anyone have alternate suggestions or something I am missing or perhaps a more elegant solution?
Thank you!