I missed the description of the LED backlight, if any, but if there is a=20
dc/dc involved (say a boost to run several white LEDs in series=20
constant-current), then that dc/dc is being PWMed to control dimming,=20
and it very well could have a low max PWM frequency.

J

Brent Brown wrote:
> On 21 Jun 2011 at 18:02, Barry Gershenfeld wrote:
>> I have, what was to be a simple controller, that suddenly got an additio=
nal
>> job of controlling an LED backlight.  Dimming is done via PWM, and the s=
pec
>> states a max frequency around 250 Hz.
>
> Wondering what factor(s) dictate the max spec of 250Hz? A minimum spec wo=
uld
> be important to minimise flicker. Even so LED flicker can be noticeable w=
ell above
> 250Hz in some conditions. If there is no good reason why not then higher =
freq
> would be better and your problem goes away.
>
--=20
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