KillingTime
Newly Enlightened
Hello all,
[PLEASE NOTE: I'm no longer suggesting people use this voltage regulator on its own, without some sort of external circuit to overcome the negative voltage drop on the SST-50 led as it heats up) . The negative temperature coefficient of the LED on extended runtimes causes increasing amounts of current to be drawn - resulting in LED damage. My advice - stick to current regulation. This regulator may be of interest to other projects, so I'm leaving the data up.]
[EDIT: (again!). See pepko's post further down, a solution to overcomming the negative temperature coefficient on the LED may have been found.]
Just thought I’d share my experiences with a regulator that I purchased for an SST-50 project.
For those that don’t know, a company called Phatlight have brought out two emitters that can be run at 5A and 10A (@3.6v). The SST-50 and SST-90.
Driving these emitters is not a problem. You can do direct drive from a single Li-Ion, or run 4 x Shark Buck regulators from the shoppe. The problem with direct drive, is that you don’t get full output from the emitter over the battery output range – but the flashlight build is simplified due to the lack of regulator. Using 4 x Shark Bucks @ 2.5A each is possible, but much more expensive, and there’s the space consideration. So, I decided to look for an ‘off the shelf’ regulator that could be bought cheaply, and would do the job of running an SST-90 at full power (10A).
I’ve found what I thought might do the job, and my experiences are detailed here.
The regulator I used is made by Artesyn Technologies, and is called the LD010C. Basic specs below (please note, I'm not selling these):
Cost: 11.50GBP (16.1USD) Single Quantity
DC-DC Buck Switching Voltage regulator. 50W max handling capacity.
Input Voltage: 3-18.8V (2 or 3 Li-Ion battery)
Output Voltage: 0.59 – 5.1V
Output current max: 10A
No input or output capacitors needed.
Small: 11 x 21mm (including pins).
Convection cooled – will need custom heat sink if no fan is used (see below).
You’ve probably noticed by now, that this is a voltage regulator (and not a current regulator like the Shark Buck). That’s the one drawback. Current regulators are better for this application (high power LED) because the power delivered to the LED is not affected as much by LED temperature. The SST-50 and 90 have a negative voltage temp coefficient, which means as they heat up, the Vf goes down. You can overcome the worst effects of the neg temp coeff by good LED heatsinking, and starting with a slightly lower regulator voltage. This is what I did, and it worked for me.
As this regulator was unknown (to me), I did some testing on the output regulation. The results can be found below. If you’re designing a LED flashlight around this regulator, then the data could come in handy because it details the output drift over input voltage and temperature. This regulator has a nasty habit of raising its output voltage as the input voltage drops (see graphs). If you’re driving the 50 or 90 at high power levels to start with, and the output rises, even a small rise can lead to huge increases in current. The trick to achieving good (spec. sheet) regulation (0.042 dV) over the input range, was to use short leads between the regulator and load (<9cm). I used 30cm lead initially, and the regulation was poor (0.27 dV rise).
The V/A curve for the SST-50 is shown below:
You can see at 3.5V, the current drawn is around 4.5A. If the voltage were to shift up by 0.27v, the current would disappear off the graph (8 – 9A ?). Clearly unacceptable. A shift of 0.042v from 3.5v takes us to 5A. While the dVout was acceptable for me, it might not be for you if your application is different. You will need to download the spec sheet for your LED.
As for the regulator, it only needs one external component to set the output voltage. I used a 22 turn miniature preset (10k). The standard one turn presets will not offer enough fine control. As the resistance drops, the output increases.
Some tips:
1. The regulator is designed to be cooled by air convection. I made an aluminium heat sink (pictured above) that did the job in the absence of air convection (using 2mm thick aluminium strip). The copper braid pictured is de-soldering wick. All stuck together with Arctic Alumina Epoxy. Both chips on top and the one chip underneath are cooled. You still have to attach this heat sink to something metal. For testing, I used a TO220 heatsink. The regulator pictured managed a 2 hour burn in test. 1 Hr at 5A and 1 Hr at 7A (see results).
2. I’ve noted dVout on the results. This is the maximum rise in output voltage over the whole input voltage range (worst case). If you’re using protected Li Ions, then they’ll give up way before you hit the minimum input voltage (4.5v). For example, 3 x Li Ions would give you (3 x 4.2v) 12.6v, but they’d cut out at (3 x 2.25) 6.75v. Likewise, 2 x Li Ions would start at 8.4v and end at 4.5V. This is why I’ve listed the dVout over 13v – 7v and 9v – 4.5v ranges.
3. I did manage 10A through a 0.35 Ohm load (3.5v). Only tried it for a few seconds though as my load heat sink could not remove all the heat generated.
4. The regulator seemed to function with greater accuracy when no input or output capacitors were used.
5. Even though I was using a Pentium 3 fan cooled heatsink (pictured), the heatsink was too hot to touch at 7A after 1 hour. People running the SST-90 for extended periods at 10A are going to need to think about thermal considerations....
Listed in order are:
1. 5A load test, using short load leads and no I/P or O/P capacitors.
2. 5A load test, using short load leads and 220uF I/P and O/P capacitors.
3. 5A load test, using long load leads and no I/P or O/P capacitors.
4. 1Hr run time test at 5A.
5. 1Hr run time test at 7A.
Some other pictures:
[PLEASE NOTE: I'm no longer suggesting people use this voltage regulator on its own, without some sort of external circuit to overcome the negative voltage drop on the SST-50 led as it heats up) . The negative temperature coefficient of the LED on extended runtimes causes increasing amounts of current to be drawn - resulting in LED damage. My advice - stick to current regulation. This regulator may be of interest to other projects, so I'm leaving the data up.]
[EDIT: (again!). See pepko's post further down, a solution to overcomming the negative temperature coefficient on the LED may have been found.]
Just thought I’d share my experiences with a regulator that I purchased for an SST-50 project.
For those that don’t know, a company called Phatlight have brought out two emitters that can be run at 5A and 10A (@3.6v). The SST-50 and SST-90.
Driving these emitters is not a problem. You can do direct drive from a single Li-Ion, or run 4 x Shark Buck regulators from the shoppe. The problem with direct drive, is that you don’t get full output from the emitter over the battery output range – but the flashlight build is simplified due to the lack of regulator. Using 4 x Shark Bucks @ 2.5A each is possible, but much more expensive, and there’s the space consideration. So, I decided to look for an ‘off the shelf’ regulator that could be bought cheaply, and would do the job of running an SST-90 at full power (10A).
I’ve found what I thought might do the job, and my experiences are detailed here.
The regulator I used is made by Artesyn Technologies, and is called the LD010C. Basic specs below (please note, I'm not selling these):
Cost: 11.50GBP (16.1USD) Single Quantity
DC-DC Buck Switching Voltage regulator. 50W max handling capacity.
Input Voltage: 3-18.8V (2 or 3 Li-Ion battery)
Output Voltage: 0.59 – 5.1V
Output current max: 10A
No input or output capacitors needed.
Small: 11 x 21mm (including pins).
Convection cooled – will need custom heat sink if no fan is used (see below).
You’ve probably noticed by now, that this is a voltage regulator (and not a current regulator like the Shark Buck). That’s the one drawback. Current regulators are better for this application (high power LED) because the power delivered to the LED is not affected as much by LED temperature. The SST-50 and 90 have a negative voltage temp coefficient, which means as they heat up, the Vf goes down. You can overcome the worst effects of the neg temp coeff by good LED heatsinking, and starting with a slightly lower regulator voltage. This is what I did, and it worked for me.
As this regulator was unknown (to me), I did some testing on the output regulation. The results can be found below. If you’re designing a LED flashlight around this regulator, then the data could come in handy because it details the output drift over input voltage and temperature. This regulator has a nasty habit of raising its output voltage as the input voltage drops (see graphs). If you’re driving the 50 or 90 at high power levels to start with, and the output rises, even a small rise can lead to huge increases in current. The trick to achieving good (spec. sheet) regulation (0.042 dV) over the input range, was to use short leads between the regulator and load (<9cm). I used 30cm lead initially, and the regulation was poor (0.27 dV rise).
The V/A curve for the SST-50 is shown below:
You can see at 3.5V, the current drawn is around 4.5A. If the voltage were to shift up by 0.27v, the current would disappear off the graph (8 – 9A ?). Clearly unacceptable. A shift of 0.042v from 3.5v takes us to 5A. While the dVout was acceptable for me, it might not be for you if your application is different. You will need to download the spec sheet for your LED.
As for the regulator, it only needs one external component to set the output voltage. I used a 22 turn miniature preset (10k). The standard one turn presets will not offer enough fine control. As the resistance drops, the output increases.
Some tips:
1. The regulator is designed to be cooled by air convection. I made an aluminium heat sink (pictured above) that did the job in the absence of air convection (using 2mm thick aluminium strip). The copper braid pictured is de-soldering wick. All stuck together with Arctic Alumina Epoxy. Both chips on top and the one chip underneath are cooled. You still have to attach this heat sink to something metal. For testing, I used a TO220 heatsink. The regulator pictured managed a 2 hour burn in test. 1 Hr at 5A and 1 Hr at 7A (see results).
2. I’ve noted dVout on the results. This is the maximum rise in output voltage over the whole input voltage range (worst case). If you’re using protected Li Ions, then they’ll give up way before you hit the minimum input voltage (4.5v). For example, 3 x Li Ions would give you (3 x 4.2v) 12.6v, but they’d cut out at (3 x 2.25) 6.75v. Likewise, 2 x Li Ions would start at 8.4v and end at 4.5V. This is why I’ve listed the dVout over 13v – 7v and 9v – 4.5v ranges.
3. I did manage 10A through a 0.35 Ohm load (3.5v). Only tried it for a few seconds though as my load heat sink could not remove all the heat generated.
4. The regulator seemed to function with greater accuracy when no input or output capacitors were used.
5. Even though I was using a Pentium 3 fan cooled heatsink (pictured), the heatsink was too hot to touch at 7A after 1 hour. People running the SST-90 for extended periods at 10A are going to need to think about thermal considerations....
Listed in order are:
1. 5A load test, using short load leads and no I/P or O/P capacitors.
2. 5A load test, using short load leads and 220uF I/P and O/P capacitors.
3. 5A load test, using long load leads and no I/P or O/P capacitors.
4. 1Hr run time test at 5A.
5. 1Hr run time test at 7A.
Some other pictures:
Last edited:
