Thanks a lot for the suggestions. I want to be able to control the=20 intensity with a PIC so I can't use a typical power supply with constant=20 current setting and yes the high voltage of approx. 144 volts DC makes=20 that a limiting factor. When it comes down to it ideally I need a=20 constant current supply that outputs at least 144 volts at 3.6 A. This=20 supply then needs to be controllable via at least 20 kHz PWM. I guess=20 alternatively I could use 4 36 Volt constant current drivers . Still=20 wondering however if anyone knows if I could put a FET in series with=20 the LEDs using a driver such as this one.=20 http://www.meanwell.com/webapp/product/search.aspx?prod=3Dhvgc-320 Also someone asked if I could sync the the PWM to the camera but=20 unfortunately it could be used with different cameras so that would be=20 difficult. Thanks, Jim On 2016-09-20 02:56 AM, rubenjonsson@bredband.net wrote: > 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): > > 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" > 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 i= n >>> the right direction. --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .