Vf is for?

[gtwace]

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.

 

[unnerv]

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

 

[albert]

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.

 

[LEDependent]

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

 

[gadget_lover]

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