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Voltage or PWM controlled resitor

T

Teten

Hello

How can I realize a voltage or PWM controlled resistor to change
current into a LED based system ?

Current = 10mA to 350mA

DC voltage controlled resirtor or PWM (duty cycle) controlled resitor

Thank you a lot for your help.

Best regards,
Teten
 
M

Mook Johnson

A current mode PWM controller will effectively drive the LED with a current
instead of a voltage. Play some games with the voltage refereance and you
should be able to get the range of currents you seek.
 
W

Winfield

How can I realize a voltage or PWM controlled resistor to change
current into a LED based system? Current = 10mA to 350mA

DC voltage controlled resirtor or PWM (duty cycle) controlled resistor

I'll see if I can answer your question. First, voltage-controlled
current source circuits are often considered, and are a good way to
make programmable currents. A simple current source can be created
if the load is floating, rather than grounded.

A true or "pure" current source, "sources" current into a grounded
load, and this needs a power current mirror as part of its design.
ASCII circuit diagrams for both of these have been posted here on
s.e.d. multiple times, and are available with a Goggle search.

Finally, let's address your question about a PWM resistor. While
I wouldn't use a PWM resistor, per se, for your LED-current source,
a PWM programming-signal makes plenty of sense. This can be used to
create a PWM current (full on or off with a PWM ratio) into the
mirror
mentioned above, and if the mirror has a smoothing filter capacitor,
then the PWM signal will create a steady programmable current out of
the mirror into the LEDs.
 
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