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Digital controlled linear current source IC simple to use?

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tooki:

--- Quote from: smile on October 25, 2018, 02:29:10 pm ---Well PWM gets slow at low brightness, that is how it dims the light. At such conditions the camera detects flicker or image distortions at pixel level, especially if I would use R,G,B as separate photos then merge them together to make color image.
--- End quote ---
Please, I know how PWM works. Are you sure you do? You say that “PWM gets slow at low brightness”, but that’s not true. You choose a PWM frequency, and the duty cycle changes: in one period, the ratio of off to on. The speed is the same. The human eye is much more sensitive to changes in brightness at low illumination than high, which is why we notice any flicker more at the low end of PWM than the high end. (And persistence of vision comes into play, too.) A higher PWM frequency solves this.

Anyway, you didn’t understand me. I said two things:

1. PWM at very high speed will work fine on a camera. As long as the PWM period is much shorter than the shutter speed (and ideally a clean multiple), it’ll work without flicker or inconsistent exposure. (For example, if you’re using a shutter speed of 1/100sec, and you use a PWM frequency of 5KHz, then each exposure will have 50 complete PWM periods. So even if the timing is slightly off, and a picture gets 49 or 51 periods instead, that 1/50th variation is negligible.

2. Many constant-current LED drivers offer PWM or serial input to control the dimming. Meaning that you give it either serial (like serial commands over SPI or I2C) or PWM input (meaning that it takes the PWM signal from your dimmer) and converts that to an analog change in LED current. The output is not PWM.


--- Quote from: smile on October 25, 2018, 02:29:10 pm ---So if there is no RGBW chip with 95CRI white then this idea will not work. I need to have 2 chips one with RGB the other with 95CRI white at 3000K or 4000K, perhaps both. That complicates things, are you sure there is no RGBW chip with 95CRI white?

--- End quote ---
::shrug:: I dunno. You said they don’t exist, not me.


P.S. Maybe it’s just the language barrier, but you come off as kind of argumentative.

smile:
Thanks everyone for your input.

So is there any constant current linear not PWM LED drivers that can be controlled by say voltage 0V-3V or PWM from arduino for my task. Perhaps somebody has first hand experience and can recommend what I need?

mvs:

--- Quote from: smile on October 26, 2018, 06:32:28 pm ---So is there any constant current linear not PWM LED drivers that can be controlled by say voltage 0V-3V or PWM from arduino for my task.

--- End quote ---
Take a look at PT4115. It is CCM buck converter for LEDs with linear dimmig capability (0.5-2.5V levels at DIM input).

amlu:
I had good results driving 10watt leds using this boards,
they have pwm pin, easy to control  it from an arduino.

https://www.aliexpress.com/item/Free-Ship-3pcs-DC-DC-step-down-5A-constant-voltage-constant-current-module-LED-drive-solar/32811163878.html?spm=2114.search0104.3.317.36321483xbfH4h&ws_ab_test=searchweb0_0,searchweb201602_2_10152_10151_10065_10344_10130_10068_10324_10547_10342_10325_10343_10340_10548_10341_10696_10192_10190_10084_10083_10618_10307_10820_10301_10821_10303_10059_100031_10103_10624_10623_10622_10621_10620,searchweb201603_36,ppcSwitch_5&algo_expid=e06dbf02-9b40-4399-b07b-3bfdf2bef8cc-46&algo_pvid=e06dbf02-9b40-4399-b07b-3bfdf2bef8cc&priceBeautifyAB=0

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