> I was wondering if anyone knows of a high PWM frequency LED driver I
> could use. I would like to drive 4  Cree CXB3590 COB LEDs in series (36
> Vx4 3.6A)  .  I would like to be able to have a PWM frequency of at
> least 20 KHz if possible. It would be used with high speed video so the
> high frequency would be used to avoid strobing. Also I am hoping for an
> off the shelf driver like the Mean Well drivers , not one that I would
> design and build. Seems like most of the commercially available drivers
> have a PWM frequency topping out around 3 Khz. Would it be possible to
> use one of these drivers, run it full out with a FET in series or
> shunting the LED string to do the PWMing rather than use the built in
> PWM function. Curious if anyone has any experience that would send me in
> the right direction.

> Hi Jim,
>
> I don't know what's available in off the shelf PWM drivers. But to avoid strobing
> altogether you may need to consider filtering the PWM to supply the LED's with
> smooth DC current. You don't say what frame rate the high speed video is, but it's
> possible you'd see various undesirable effects at almost any PWM frequency if the
> LED's & camera are not synchronised.
>
> Brent
>
> On 20 Sep 2016 at 1:55, Jim Ruxton wrote:
>
>> I was wondering if anyone knows of a high PWM frequency LED driver I
>> could use. I would like to drive 4  Cree CXB3590 COB LEDs in series (36
>> Vx4 3.6A)  .  I would like to be able to have a PWM frequency of at
>> least 20 KHz if possible. It would be used with high speed video so the
>> high frequency would be used to avoid strobing. Also I am hoping for an
>> off the shelf driver like the Mean Well drivers , not one that I would
>> design and build. Seems like most of the commercially available drivers
>> have a PWM frequency topping out around 3 Khz. Would it be possible to
>> use one of these drivers, run it full out with a FET in series or
>> shunting the LED string to do the PWMing rather than use the built in
>> PWM function. Curious if anyone has any experience that would send me in
>> the right direction.
>  
>
>

> Hi Jim,
>
> I don't know what's available in off the shelf PWM drivers. But to
> avoid strobing
> altogether you may need to consider filtering the PWM to supply the
> LED's with
> smooth DC current. You don't say what frame rate the high speed video
> is, but it's
> possible you'd see various undesirable effects at almost any PWM
> frequency if the
> LED's & camera are not synchronised.
>
> Brent
>
> On 20 Sep 2016 at 1:55, Jim Ruxton wrote:
>
>> I was wondering if anyone knows of a high PWM frequency LED driver I
>> could use. I would like to drive 4  Cree CXB3590 COB LEDs in series (36
>> Vx4 3.6A)  .  I would like to be able to have a PWM frequency of at
>> least 20 KHz if possible. It would be used with high speed video so the
>> high frequency would be used to avoid strobing. Also I am hoping for an
>> off the shelf driver like the Mean Well drivers , not one that I would
>> design and build. Seems like most of the commercially available drivers
>> have a PWM frequency topping out around 3 Khz. Would it be possible to
>> use one of these drivers, run it full out with a FET in series or
>> shunting the LED string to do the PWMing rather than use the built in
>> PWM function. Curious if anyone has any experience that would send me in
>> the right direction.

> it's possible you'd see various undesirable effects at almost any PWM
> frequency if the LED's & camera are not synchronised.
>
> Brent
>
> On 20 Sep 2016 at 1:55, Jim Ruxton wrote:
>
> > I was wondering if anyone knows of a high PWM frequency LED driver I
> > could use. I would like to drive 4  Cree CXB3590 COB LEDs in series
> > (36
> > Vx4 3.6A)  .  I would like to be able to have a PWM frequency of at
> > least 20 KHz if possible. It would be used with high speed video so
> > the high frequency would be used to avoid strobing. Also I am hoping
> > for an off the shelf driver like the Mean Well drivers , not one that
> > I would design and build. Seems like most of the commercially
> > available drivers have a PWM frequency topping out around 3 Khz. Would
> > it be possible to use one of these drivers, run it full out with a FET
> > in series or shunting the LED string to do the PWMing rather than use
> > the built in PWM function. Curious if anyone has any experience that
> > would send me in the right direction.
>
>
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive

> Instead of PWM dimming you can use linear dimming. It is basically a
> switching regulator at around 300kHz to 1MHz that regulates the current
> linearly. You can normally dim linearly down to a couple of hundred mA,
> below that you need to PWM dim.
>
> You can see the difference between linear and PWM dimming in a
> datasheet for a led driver. For example TPS92640/1 (which has both
> linear and PWM dimming): <http://www.ti.com/lit/ds/symlink/tps92640.pdf>
>
> An alternative is to use a power supply with constant current setting
> and just set the current that you want. But 150V might be a limiting
> factor here.
>
> /Ruben
>
> On Tue, 20 Sep 2016 18:34:58 +1200, "Brent Brown"
> <brent.brownspam_OUTclear.net.nz> wrote:
>> Hi Jim,
>>
>> I don't know what's available in off the shelf PWM drivers. But to
>> avoid strobing
>> altogether you may need to consider filtering the PWM to supply the
>> LED's with
>> smooth DC current. You don't say what frame rate the high speed video
>> is, but it's
>> possible you'd see various undesirable effects at almost any PWM
>> frequency if the
>> LED's & camera are not synchronised.
>>
>> Brent
>>
>> On 20 Sep 2016 at 1:55, Jim Ruxton wrote:
>>
>>> I was wondering if anyone knows of a high PWM frequency LED driver I
>>> could use. I would like to drive 4  Cree CXB3590 COB LEDs in series (36
>>> Vx4 3.6A)  .  I would like to be able to have a PWM frequency of at
>>> least 20 KHz if possible. It would be used with high speed video so the
>>> high frequency would be used to avoid strobing. Also I am hoping for an
>>> off the shelf driver like the Mean Well drivers , not one that I would
>>> design and build. Seems like most of the commercially available drivers
>>> have a PWM frequency topping out around 3 Khz. Would it be possible to
>>> use one of these drivers, run it full out with a FET in series or
>>> shunting the LED string to do the PWMing rather than use the built in
>>> PWM function. Curious if anyone has any experience that would send me in
>>> the right direction.

> Instead of PWM dimming you can use linear dimming. It is basically a
> switching regulator at around 300kHz to 1MHz that regulates the
> current linearly. You can normally dim linearly down to a couple of
> hundred mA, below that you need to PWM dim.
>
> You can see the difference between linear and PWM dimming in a
> datasheet for a led driver. For example TPS92640/1 (which has both
> linear and PWM dimming):
> <http://www.ti.com/lit/ds/symlink/tps92640.pdf>
>
> An alternative is to use a power supply with constant current setting
> and just set the current that you want. But 150V might be a limiting
> factor here.
>
> /Ruben
>
> On Tue, 20 Sep 2016 18:34:58 +1200, "Brent Brown"
> <TakeThisOuTbrent.brownEraseMEspam_OUTclear.net.nz> wrote:
>> Hi Jim,
>>
>> I don't know what's available in off the shelf PWM drivers. But to
>> avoid strobing altogether you may need to consider filtering the PWM
>> to supply the LED's with smooth DC current. You don't say what frame
>> rate the high speed video is, but it's possible you'd see various
>> undesirable effects at almost any PWM frequency if the LED's & camera
>> are not synchronised.
>>
>> Brent
>>
>> On 20 Sep 2016 at 1:55, Jim Ruxton wrote:
>>
>>> I was wondering if anyone knows of a high PWM frequency LED driver I
>>> could use. I would like to drive 4  Cree CXB3590 COB LEDs in series
>>> (36
>>> Vx4 3.6A)  .  I would like to be able to have a PWM frequency of at
>>> least 20 KHz if possible. It would be used with high speed video so
>>> the high frequency would be used to avoid strobing. Also I am hoping
>>> for an off the shelf driver like the Mean Well drivers , not one
>>> that I would design and build. Seems like most of the commercially
>>> available drivers have a PWM frequency topping out around 3 Khz.
>>> Would it be possible to use one of these drivers, run it full out
>>> with a FET in series or shunting the LED string to do the PWMing
>>> rather than use the built in PWM function. Curious if anyone has any
>>> experience that would send me in the right direction.