LED Driver Questions

I was wondering what kind of components I would need to make a driver that switches the LED on and off at 30+ times per second. I figure that this will increase the efficiency by about 50%, since the LED would only be on half the time. I also think that I can overdrive the LED a little bit, because it would only be pulsing the power, not giving constant current. Lastly, what kind of batteries would be able to run a Luxeon K2, and could I make a driver to increase the current if I was just using small batteries.

What you're describing is a PWM driver.

For LEDs, PWM is less efficient than constant current for a given amount of light, not more. When you pulse a light source on and off, your eyes integrate the pulses so it appears constant, but the brightness is only the average, not the peak.

Math to prove it:

Take a given Luxeon. Say it produces 60 lumens at 700mA, Vf=3.6; and 36 lumens at 350mA, Vf=3.3

So we'll use a PWM setup, drive it at 50% (so it's off for 50% of the time). The pulses will be 700mA. So you have 700mA pulses at Vf=3.6V, or 2.5W per pulse. When you factor the 50% duty cycle, then it's 1.25W of power dissipation.
For that 1.25W, you get 30 lumens of light out. Your efficiency is 24 lumens per watt.

Now, lets simply drive the LED at 350mA with a constant current source (even a resistor will work). Now you get constant power dissipation of 1.15W, but you're producing 36 lumens. Your efficiency is 31 lumens per watt.

In this example, PWM is 24 lumens per watt, but constant current is 31 lumens per watt.

Don't think you can get away with pulsing at higher power to get more light either. Lets say you think you can get away with pulsing at 1A with a 35% duty cycle.
At 1A, the LED will have a Vf of 3.8V, and will produce about 75 lumens. So each pulse consumes 3.8W, and produces 75 lumens. Your average power consumption is 1.33W, and your average light output is about 26 lumens. You're using more power, and producing less light than the 700mA/50% example! The efficiency here is around 20 lumens per watt.

The lower the duty cycle, and higher each pulse current is (relative to constant current), the LESS efficient PWM becomes.

One of the few reasons to use PWM is to avoid color shifting in LEDs that can happen at lower current. However, I seriously doubt that you'd notice color shift, even running the LED at 1/10th its rated current. It's more complicated and less efficient than constant current. Your best bet is to forget about building a circuit, and just put the appropriate resistor in there to get the proper current.

Thanks for the information, that simplify the setup also.