Electrical Engineering Stack Exchange
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Questions tagged [constant-current]

Questions regarding constant-current supplies, devices and applications, as opposed to constant-voltage supplies. The voltage can vary while the current remains the same. Common in LED lighting applications and battery charging.

Questions regarding constant-current supplies, devices and applications. As opposed to constant-voltage supplies, constant-current circuits adjust the voltage such that the current matches the setpoint value.

Constant-current circuits are common in a plethora of applications such as:

  • LED driving
  • some regimes of battery charging
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What's the intuition for reading transistor/resistor circuits?

The below circuit supposedly provides constant current to an LED. I tested using everycircuit.com and that seems correct (used R = 70 ohm for example). What's a step by step way of thinking about the flow of electrons in such a circuit? How can we…
JC123
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What is the dual of a diode?

A diode has an exponential I-V curve. To a first approximation, it will pass whatever amount of current is required to keep the voltage across it constant. Is there a passive component that will (approximately) drop any amount of voltage to maintain…
user253751
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How do constant current constant voltage devices work?

First of all can a device that is constant current also be at the same time constant voltage? In my head I just could not grasp how this device can work. Individually I understand how it works, constant current supplies adjust the voltage to sustain…
Jake quin
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What are some practical examples of a constant current source?

Please don't state the obvious that nothing is a perfect constant current source. And please do not give examples of how to create them from components. I looked at this SE Q/A which stated the obvious - that you can not have a perfect current…
jennifer
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How to calculate the tolerance of this constant current circuit?

I am using the circuit below to provide constant current to th LEDs. I request your suggestion on how to calculate the tolerance of current (minimum and maximum variation of set current) due to temperature alone. How to consider changes in Vbe…
Sonder
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Usefulness of constant current limiting in bench power supply

I'm building a bench power supply as my introductory project to electronics. When it comes to adjustable voltage it's easy to see the usefulness of such feature but I can't figure out what is the usefulness of having adjustable contant current…
Nicu Surdu
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How does this constant current sink actually work?

I have implemented a constant current source and it works wonderfully, but I was just hoping to try and understand it a little bit more! Here is the circuit in question: I have tried doing some searching on the web and have found it quite difficult…
MrPhooky
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Need for Temperature Compensation of Current Mirror

I am currently learning about current mirror configurations. I have made two of them so far. Both of them worked as desired but, when heated or cooled, the current through the right side (the side where the output is taken from) decreased or…
Keno
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How to reach ~50nA p-p current noise in ~200mA current source?

Target application is driving single-frequency laser diodes (@2.5V) which are sensitive to current noise. Current is constant, with no modulation. Strightforward solutions that first comes to mind is low-noise LDO (for example LT1963) that can reach…
BarsMonster
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Constant current circuit with transistors/MOSFETs design comparison

There are a few designs out there for constant current devices, but most of them use a certain chip. I was looking for a way to build my own constant current supply from parts that I have available. The aim is to control a RGB LED with 10W…
Martin H
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can leds take varying voltage > listed voltage, with constant current?

My confusion stems from a an led that shows: Input(DC): 600mA-700mA / 3V-3.4V. the product suggests a constant current led driver (same brand as LED) that shows: Output: Current 600mA (Constant) ; Voltage 18-34V In researching I have read that…
Jordan Klaers
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Precision circuit that is CC and CV circuit or power supply

I want to design a CC/CV (constant current/constant voltage) circuit in which I can set the voltage limit or current limit with DAC's 0 to 5V range. I know how to design variable CC circuits and CV: simulate this circuit – Schematic created using…
Voltage Spike
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Explanation of LED driver circuit

I've been reading up on LED drivers and found some common connection schemes. Yet, I recently came across the following LED driver circuit at this URL: I tried to find out what exactely was going on here but I do not understand why the LEDs are fed…
Tom L.
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Efficient constant-current regulator for 700ma LEDs

I'm building a lamp with twelve 3x700ma RGB LEDs in it, that need to be individually PWM controlled (100-200Hz), so they can display different colours from each LED. To do this then, I think I need a separate 700ma constant-current regulator…
Derek Lewis
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Adjustable linear led driver? Linear, not PWM

I'm working on a product that requires an led to output currents varrying from 0mA to 350mA and as many possible levels in between (~1000 would be sufficient I suppose). I CANT output a PWM signal to the led because that would defeat the purpose of…
Peter Clyde
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