Vf is for?

What does the Vf (forward voltage) changes ? e.g an TXOJ vs TXOM, what differences is there using higher Vf luxdeon vs lower Vf one ? Thanks.

Generally a lower Vf is more efficient and so will drive at the specified current at a lower voltage.

When your input voltage drop below the forward voltage of the LED, your light will go into direct driven mode, the regulating circuit is no longer in use.

Forward voltage is the voltage at which the LED will run at its rated current.

The Vf indicates the range of voltage at which it will draw the amount of current (and indirectly power) that it was designed for. A lower VF is more efficient but may cause you to waste excess voltage in a converter or resistor.

An L may be well suited to 3 AA direct drive using alkalines, where an M may match up well to direct drive from a lithium. An H might work well using a single lithium 3 volt cell in direct drive.

A 'K' works well with two AA lithiums (~ 3.5 volts).

If you are going to use a constant current converter like a downboy, a lower Vf will give longer run times.

The Vf is NOT written in stone. It's a range of voltages. I recently got a LuxIII start marked J that tested out to be closer to an M. Very disapointing.

If you are not doing your own mods you probably will not care about any of this.

Daniel