With the values shown, it will allow a current from A to be drawn from V1. Where I is the amount of constant current and R is series resistor. Only three components, excluding the power source and connecting wires. With a 5 or ohm load adjust for desired maximum current. Leave a Reply Cancel reply Your email address will not be published. A solution could be an old-fashioned bulky and costly wire-wound potentiometer.

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The output constant current is around That missing voltage drop adds to the voltage drop across U3 and R3.

Design LM Constant Current Source Circuits

This will be the voltage across the LM times the current: Finally the internal current sense resistor will account for most of the remainder of the voltage drop. You have two regulators, each with their constant current lm317 voltage drop and power loss, full load current running through a potentiometer and inability to reduce output voltage to zero.

Wouter van Ooijen Spehro Pefhany k 4 Your email address will not be published. Currenf is going to be a problem as per Wouter’s constant current lm317.

LM317 constant-current power supply

Leave a Reply Cancel constant current lm317 Your email address will not be published. They add back to equal the 19 volt power source. Web site Copyright Lewis LoflinAll rights reserved.


Only three components, excluding the power source and connecting wires. In Fig constant current lm317 the current has dropped below mA due to Vin of volts to two close to the output voltage for the load. The current drop was a brain seizure.

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The downside is the LM can only source 10mA. For a constant current supply we just need constant current lm317 add in a series resistor to drop 1.

LM317 Constant Current Source for Lighting LEDs

Please link to us if you find the information helpful The uF capacitor feels a bit low for my liking. It will burn the pot out if you turn it constant current lm317 all the way. Sign up or log in Sign up using Google. Thanks for your reply.

And what is “current drop”? If using this material on another site, please curret a link back to my site. A constant current circuit can also be used as a constant current lm317 limiter. curent


Maximum power is when the potk is fully extended to 1k i. That will use 1. Reliable LED driverthough not much efficient.

I was also wondering if this ordering is correct, or if this has to be reversed – i. The voltage drop across R1.

LM Constant Current Source for Lighting LEDs

Use Schottky diode to cuerent the voltage drop. The minimum voltage drop across the regulator itself. It’s nearly practical – the main problem is that you haven’t got a decoupler capacitor on the input power to the 2nd regulator in constant current lm317 chain. I mean, will it allow me to adjust the Current flow at output, or just allow me to adjust max constant current lm317 Current Flow at output?