How does regulation work?

[Supernam]

I don't have an EE degree or anything like that, so forgive me.

If I wanted to swap an emitter from a Lux V to a SSC, would I need to be concerned with the driver since they have different Vf? Do driver's PRODUCE a specific voltage while REGULATING current? Would the Seoul be seeing too much voltage and burn out? I think I'm having a tough time applying Ohm's Law to LED drivers. Explanations in lay terms would be appreciated!

 

[LedSled]

Regulation just means that your light is controlling something. It can be voltage, current, or power (voltage times current). Most diodes, including LED's, have their forward voltages get lower as they get hot. Battery voltages get lower as they discharge. Regulator circuits attempt to keep your light shining with the same brightness in spite of these changes. There are lots of specific circuit types to make this happen.

Most LED flashlight regulators keep constant current by dynamically adjusting the voltage to the emitter. You can successfully change emitters using the same regulator circuits. Lux III's and SSC P4's are very compatible, since their operating currents and voltages are quite similar. Not so Lux V's and SSC P4's.

 

[Lightingguy321]

You will have to modify your regulator as well to conform with the SSC-P4, since the Lux V can typically be driven at 1A and SSC's are from ~350 to ~700 and after that they tint shift if they are not heat sinked well.

 

[LukeA]

You will have to modify your regulator as well to conform with the SSC-P4, since the Lux V can typically be driven at 1A and SSC's are from ~350 to ~700 and after that they tint shift if they are not heat sinked well.

SSCs can be heatsinked perfectly well at 1A, especially newer ones.

 

[LedSled]

Check me if I'm wrong, but Lumiled's Lux V datasheet calls for a 6.84v Vf, depending slightly on bin code. The Lux III Vf is about 3.7v. An SSC P4 has about a 3.25v Vf.

Asking a current-regulator that works around a 3.7v nominal output to swing down to 3.25v isn't asking too much. Going from 6.84v down to 3.25v is asking a lot. I seriously doubt a Lux V to SSC P4 mod is feasible on a current-regulated light, but if someone has actually done it, I'm all ears.

 

[Supernam]

That's what I was wondering... because the Vf of a ssc is nearly half of the LuxV. This swap HAS been done by more experienced modders, I want to know what needs to be done to the regulators in order for this to work.

 

[LedSled]

Supernam, just FYI, there are 3 primary regulator types:
1) Buck - output voltage is always lower than the lowest battery voltage expected
2) Boost - output voltage is always higher than the highest battery voltage expected
3) Buck/Boost - output voltage can be higher or lower than the battery voltage

 

[half-watt]

Supernam, just FYI, there are 3 primary regulator types:
1) Buck - output voltage is always lower than the lowest battery voltage expected
2) Boost - output voltage is always higher than the highest battery voltage expected
3) Buck/Boost - output voltage can be higher or lower than the battery voltage

unless terminology has changed in the last few decades...

let's not confuse voltage regulators with voltage converters. the three named above in the quoted Post are types of voltage converters and not voltage regulators.

now, a voltage regulator may and usually does convert Vin to a diff. Vout, but it will also, within the limits of its design, attempt to maintain a fairly constant Vout, that is, it also (and primarily - hence, the term "regulator") acts as an output voltage stabilizer (often together with other components of the overall power supply design).

a voltage converter merely provides a diff Vout for a given Vin, but does not hold the Vout constant. for instance, a pure boost converter may boost the voltage up to some initially higher value, but then from t-zero that converted/boosted Vout will steadily decrease as Vin. this type of boost converter (without Vreg) design is seen in some low-end, single-cell lights that produce an unregulated steadily decreasing light output from the moment the light is turned on. QuickBeam's FLR website has many burntime plots of this type of unregulated converter output.

i've noticed that this distinction is sometimes overlooked and may be intentional. that is, sometimes "shortcuts" in terminology are employed by a Community of individuals who all have a clearer understanding of what is being said. i'm guessing that this is the case in this Thread.

the purpose of my Post is *NOT* to correct the Poster to whom i am replying (my guess is that LedSled already knows the info i'm conveying in this Post, but for the sake of brevity did not include the info i'm providing), but rather merely make this distinction clearer to any Newbie's or non-technical people reading LedSled's fine Post.

 

[chris_m]

You will have to modify your regulator as well to conform with the SSC-P4, since the Lux V can typically be driven at 1A and SSC's are from ~350 to ~700 and after that they tint shift if they are not heat sinked well.

Strangely you've got that totally backwards - SSCs are happy at 1A (which is a common drive current for them) whilst Lux Vs tend not to be driven above 700mA, since that is their specified max.

As mentioned before, the problem is in the voltage difference, and that typically with a Lux V light you get a boost regulator (I'm ignoring half-watt's post, as I don't think getting pedantic about the detail is at all helpful here), bu that the battery voltage is such that you'd need a buck/boost to run the SSC. The only realistic way of modding the regulator in these circumstances is to replace it with a new one!

 

[Lightingguy321]

oops... read the post backwards, but still Seouls have the temperature sensitive LED die phosphor coating.

 

[TorchBoy]

Supernam, just FYI, there are 3 primary regulator types:
1) Buck - output voltage is always lower than the lowest battery voltage expected
2) Boost - output voltage is always higher than the highest battery voltage expected
3) Buck/Boost - output voltage can be higher or lower than the battery voltage

I would have said that the third type is linear regulators, perhaps with an extra note that you can have a single supply which can operate in either of the first two modes (it's either going to be doing one or the other).

 

[2xTrinity]

I would have said that the third type is linear regulators

Yeah, easiest way to describe linear regulators is current-in is is the same as current-out, vin is always higher than vout, and the difference between vin and vout is dropped through resistance.

Of course, if you're contemplating swapping a LuxV for a SSC on a light controlled by a linear regulator, don't bother unless you also switch the battery being used to one with a lower voltage. The lower Vf of the SSC will mean the regulator has to waste that much more power, negating the efficiency improvements in the emitter.

As mentioned before, the problem is in the voltage difference, and that typically with a Lux V light you get a boost regulator (I'm ignoring half-watt's post, as I don't think getting pedantic about the detail is at all helpful here), bu that the battery voltage is such that you'd need a buck/boost to run the SSC. The only realistic way of modding the regulator in these circumstances is to replace it with a new one!

That depends. If the battery input is, for example, 2x LiIon, Vin will be 7.2 or higher, so the light will have to be using a buck driver. Assuming the light is current-regulated, NOT voltage-regulated, the switch should be possible.

 

[VidPro]

Explanations in lay terms would be appreciated!

it would depend on the driver used to drive the Lux 5, and the battery your using with that driver. there exists drivers that could work both ways (lux5 or lux3) , but more often the higher voltage of the lux5 used a different method/driver.
driving a lux5 was like driving 2 leds in series (higher voltage). it was also conservativly driven to insure it lasted time (lower current).

if you purchaced it from a modder here, just PM them, they could tell you in a second.
or at least provide the details of which light it is, what battery source it uses, then people might know what driver type it used.

 

[chris_m]

That depends. If the battery input is, for example, 2x LiIon, Vin will be 7.2 or higher, so the light will have to be using a buck driver. Assuming the light is current-regulated, NOT voltage-regulated, the switch should be possible.

Don't know where you get 7.2 or higher - min voltage for 2xLiIon is 6V, with a battery voltage range of 8.4 to 6. With this range a buck wouldn't work, and the regulator would need to be a buck-boost, hence nobody actually makes a single Lux V light with 2xLiIon AFAIK. More likely is a light with a single LiIon and a boost driver (or 2 Lux Vs with 2xLiIon and a boost), in which case you have exactly the problem i describe and will blow the LED due to the boost regulator going direct drive and delivering full battery voltage.