Absolutely. All of our lights are voltage regulated at this point. Also, the regulation is partial, not full.
Why? Pull up a chair...
If the LED is directly driven by the battery, you have a discharge curve that starts steep and gradually levels out and goes on at a dim level for a long time.
A regulator does not give you something for nothing of course, it simply manages what you have. Take the above discharge curve and chop off some of the top part and use it to beef up some of the bottom. Now the light is not as bright in the first part and not as dim in the second part.
Now for this to happen, the regulator must have a high enough input voltage to work. Typically, this is ~.5volts above where you want to be.
The way to do this is to increase the voltage of the battery by using more cells or to use a step-up converter to multiply the voltage at the price of current.
Typical efficiency for a converter is about 80%. Some are better some are worse, 80% is typical.
What some people miss is that you also have a voltage multiplier limit for a given input/output current and circuit. Several factors determine this, which I won't go into here. But remember that for a given converter, it can only multiply the input voltage so much before the output levels off. If that multiplication level is already reached and you drop the input level further, the output must drop too.
Don't forget there is this limit. There is a lot of hardworking converter designs out there. Usally, the battery is what whips the converter.
For example, you got this spanky converter that can provide a flat 3.2volt output even as the input drops to less than 1 volt. The catch is that at 1 volt input, the converter is asking for 2amps from the battery. This is not the converter's problem, this the law of physics (and supply/demand!). Whereas, batteries are used to providing less current as their voltage drops (or less voltage as the load current increases).
So you can have a great converter but if the battery poops out, the light is going to dim. How quickly is dims after it falls out of regulation is determined by many factors.
So, for a given converter efficiency, multiplier and battery, you will have a ideal maximum voltage for a given load. Without a regulator, this will create a discharge curve that looks just like an LED being directly driven. It dims steeply at first and then levels off for the long haul.
How do you get a flat output curve? Use a regulator. But just throwing in a regulator doesn't make the our drooping curve flat. We have to keep the regulator under the "ideal maximum voltage" mention above. At least .5volts below the above curve the whole time. If we track that curve, then our "regulated" output will match the unregulated output but just dimmer and slightly elongated because of the smaller load.
So I ask again! How do we get a flat discharge curve? Just like I said before, chop off the top and add it to the bottom. Essentially, make the light dimmer for the first hour (for example) and brighter for the second hour to blend them all together to make a flatter curve. Like a jogger pacing themselves. The sprinter will pass them initially, but while the sprinter walks the remaining distance, the jogger passes them going faster. Slow and steady wins the race, blah blah.
But we want our lights to be brighter right? You can't have it both ways all the time. Sometimes the battery is simply too small. Add to that an often overlooked fact: most flashlight usage occurs in bursts, not long protacted run times like you see on your favorite review site (no offense, we do learn somethine from those graphs). A partially regulated light delivers brighter usage each time compared to a completely regulated light. Consistancy is good, brighter is better. <img border="0" title="" alt="[Smile]" src="images/icons/smile.gif" />
Now, which is better over the different forms of regulation (either partial or full), voltage regulated or current regulated? Depends on the task, both have advantages. Voltage regulated is usally more compact and works with the batteries better to squeeze more light out of them. Current regulated is more consistant and compensates for the wide variations in Vf between LEDs. Current regulation is harder on a battery and will produce slightly less lumens per battery change, but it is more consistant. Another current regulation adds is thermal protection. This is essential in the higher power LEDs.
For the Arc-AAA, voltage regulation works best. It is the most compact way we could find to provide some regulation. Also, it is easy on the battery and ideal as a back up light. The thermal protection is not needed because of large die to housing ratio (read: less heat per in2).
For the LS, current regulation is ideal because of the heat management issues. Also, the light is intended to be a primary light which means it is used for longer durations and it is ok if it is less efficient. Especially if it means a more consistant output is provided since spares (lights and batteries) are by the nature of the mission, more likely to be had (compared to a key chain light which is usally an emergency type of light).
In both cases, partial regulation is preferred (and actually designed in by a novel means) to optomize for maximum light per typical task length. The light should actually throttle back for extended use to keep from overheating and to increase efficiency.
Currently <img border="0" title="" alt="[Smile]" src="images/icons/smile.gif" /> , the LS is voltage regulated. This was because we just had not found a small enough current regulator to fit in the light.
When some people look at a light with a very flat regulation, they see perfection. I see a package that is holding something back for the 5 minutes I need it to perform a task.
There is a happy medium though.
With our new circuits, we have much higher multiplier levels. This gives us the ability to drive the LED at full power consistantly for a decent amount of time. We could make them even brighter, but the task length would shorten and efficiency drop off rapidly. We actually have a formula for the target task length over a given percentage of the battery life. The trick is to meet the target first and then squeeze as much efficiency out as possible. Efficiency also includes the "Light Density" quotient, which I talked about earlier.
Basically, we makes lights for you that are brighter, smaller and more efficient for the target task.
Now, you have the Arc regulation philsophy 101.
Peter Gransee
