Im building an LED video camera light, but Im having trouble creating a flickerless dimmer to control it. Ive tried a PWM circuit that controlled a motor, but the flickering was apparent even when the camera shutter was at 1/100th.
http://www.mfacomodrills.com/speed_regulators/voltage_regulators.html
The circuit claimed to operate above 1Khz so I was confused as to why the flickering was so apparent at such a slow shutter speed.
Browsing various circuit forums, I came across this comment:-
As has been stated before, LEDs can be dimmed with a continuous
current. In this case there is no flicker from the LED. The trick is
to make a variable current source with high efficiency. This is done
all the time by using a PWM circuit inside the power converter and
then smoothing (filtering) the current before it is applied to the
load. You get a continuously variable, high efficiency current source
that has very little modulation on its output - and hence no flicker.
The circuits I have found on-line so far make no mention of placing the PWM within the power convertor, so Im wondering just how complex a circuit this could become, compared to say this one:-
http://www.reuk.co.uk/LED-Dimmer-Circuit.htm
Would it be possible to modify an existing off-the-shelf circuit to do this. If I have to begin from scratch, how would I incorporate PWM into the power convertor.
I'm using a 120 LED array, which are drawing approx 500mA and run off 12 VDC. Any pointers would be greatly appreciated.
http://www.mfacomodrills.com/speed_regulators/voltage_regulators.html
The circuit claimed to operate above 1Khz so I was confused as to why the flickering was so apparent at such a slow shutter speed.
Browsing various circuit forums, I came across this comment:-
As has been stated before, LEDs can be dimmed with a continuous
current. In this case there is no flicker from the LED. The trick is
to make a variable current source with high efficiency. This is done
all the time by using a PWM circuit inside the power converter and
then smoothing (filtering) the current before it is applied to the
load. You get a continuously variable, high efficiency current source
that has very little modulation on its output - and hence no flicker.
The circuits I have found on-line so far make no mention of placing the PWM within the power convertor, so Im wondering just how complex a circuit this could become, compared to say this one:-
http://www.reuk.co.uk/LED-Dimmer-Circuit.htm
Would it be possible to modify an existing off-the-shelf circuit to do this. If I have to begin from scratch, how would I incorporate PWM into the power convertor.
I'm using a 120 LED array, which are drawing approx 500mA and run off 12 VDC. Any pointers would be greatly appreciated.