This switchmode driver will run three 1 watt LEDs in series at 320mA from a 12 volt DC source or 6 LEDs from a 24 volt source. The driver uses the common and very efficient '350' LED driver and a 35 volt input capacitor, so it should handle higher voltages and more LEDs, providing the LED string voltage is less than the input voltage by a volt or two.
Driver measures 25mm x 20mm x 12mm.