Questions tagged [constant-current]

Questions regarding Constant Current supplies, devices and applications. As opposed to Constant Voltage supplies. Voltage will vary while Current remains the same. Common in LED lighting applications.

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66 views

Constant current driver and undervoltage protection for lipos

I'm searching for a way to drive a couple LEDs with a single-cell LiPo battery, such that the LEDs will be cut off completely when the LiPo voltage drops below, say, 3.3V. PCB space, component count ...
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Is it possible to design a linear voltage regulator which delivers constant current but adjustable output voltage?

Is it possible to deliver a linear voltage regulator with the following specficiations: input reference voltage is from 0.8V to 1.4V output voltage has to follow the input reference voltage, it is ...
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65 views

Understanding Thermal Characteristics for Microchip CL2N3-G Constant Current LED Driver

I'm having trouble interpreting the thermal characteristics of the Microchip CL2N3-G Constant Current LED Driver chip. Here's the datasheet: CL2N3-G Constant Current LED Driver 1 What I want to do is ...
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32 views

Is there any CC Led Driver IC that has common GND between led cathode and VIN-?

I have a project that has as 3W (using 500mA) Led and an I2C sensor at the end of a cable, and I need 6 wires for it. (4 to the I2C sensor) and 2 for the led. I’m using the PT4115 CC led driver CI, ...
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Can you use LM5117 as a CC/CV LiPo charger for a 1mAh LiPo cell?

I am trying to build a LiPo charger for a custom 1mAh LiPo cell. The cell is rated for charging with 0.5C, so 0.5mA max charging current. I cannot find any off-the-shelf ICs that can charge with such ...
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2answers
23 views

Test load capacity of cable & clips with only constant current/constant voltage power supply?

I want to test a 20m wire and soldered alligator clips on each end to see if it can carry the needed current I want to use it for (eg 5A.) Can I just hook it up to the terminals on my bench top (lab ...
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60 views

Powering a PLC and transmitters during a power failure

I have 25 locations spread out over a large area we recently had another power outage lasting 48-72 hrs.depending on the location. all locations have UPS back ups with generators. Problem: The ups ...
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55 views

Can a DC CC power supply be used for current limiting in a circuit with a battery in series

In circuit #1 I showed typical adjustable power supply usage it can limit voltage and current, all good. It got me thinking. Let's say due to some reasons I can't replace battery with a power supply ...
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403 views

How to add CC/CV feature with single LM358 for variable linear power supply?

I have a few weeks with a problem in the design of my bench power supply. First of all I have this design from this guy on YouTube https://youtu.be/_CFIovMkRyg that made a variable power supply using ...
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81 views

Do constant current LED drivers consume significant current when all outputs are disabled?

I'm trying to understand the datasheets for several shift-register constant-current LED drivers, such as TLC59281, TLC5916, CAT4016, IS31FL3726. All of them have something similar to this in their ...
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3answers
95 views

Current mirror with mosfets

This is a current mirror circuit with 2 op amp stages. First stage on the left Voltage from a DAC gets fed into U1 which creates a reference current through Rmir (via the N channel MOSFET) by sensing ...
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1answer
79 views

Working of op-amp based current source

Can anyone please explain me the working of the circuit attached? I believe the op-amp U1 is connected to provide a stable DC voltage at the non inverting terminal of U3. Is my approach correct? The ...
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312 views

Help with a constant voltage led driver

Maybe the title could be better chosen. Hello, I have a 33V 0.8A constant voltage led driver (see picture below, the item no. is GL-1201C-8 if that can help) which no longer works. I searched online ...
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2answers
95 views

Current regulator using NOT gate

I think I have designed a current regulator. This is the circuit diagram: simulate this circuit – Schematic created using CircuitLab The operation is very simple. Let's say the transistor turns ...
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109 views

Constant current source with bypass option

I need a current limiter for a project that I am working on. I understand that I can use a device like the LM317 in constant current mode, but how would I add a bypass circuit so that my ...
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1answer
112 views

What is the purpose of this transistor in this schematic?

First thing first, I am not native speaker and I am new here. This schematic is reverse engineered from searchlight PCB traces (which is broken) by me. D+ and D- terminals connect to the rechargeable ...
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99 views

Limiting the current without limiting the voltage

I want to design a current limiter, for both negative and positive voltages, for my thesis project. My design consists of a voltage source (+/-10V)(X5) and a transimpedance amplifier(X1.) Using the ...
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71 views

Create specific resistances across a constant current source

I'd like to emulate the controls on a garage door circuit programmatically. As far as I can tell the circuit acts like a constant current source and sends out 10mA to the wall console. I'd like the ...
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1answer
74 views

Question on LED usage for constant current LED driver

I am a beginning electronics hobbyist interested in robotics, who started about ~1,5 year ago, and with much to learn. I've got a question on using a constant current PMIC on a PCB project that I am ...
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75 views

Designing a PID control with plant controlled using relays

I am working on a project to design a Controlled (Constant Current) DC Battery Charger. The charger has a variable transformer (Plant). The output of which is fed to the batteries to charge them via a ...
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0answers
59 views

(ARC WELDING) Why does voltage DROP with increasing current?

I hope I'm asking in the right place! I worked with automated TIG (GTAW) welding equipment. I'm confused about how the welding power supply controls the current applied through the work piece. If the ...
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2answers
256 views

Is it better to use discrete components or voltage regulators for a variable power supply? [duplicate]

I'm a recent graduate EE student and this is my attempt to gain experience and strengthen my resume so I'm eager to figure this out. I'm designing a dual channel floating output bench power supply ...
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245 views

Calculate voltage drop across Linear MOSFET in saturation region

Considering the below schematic, how is the voltage drop across the MOSFET calculated when it is operated in the saturation region? I am trying to calculate the power dissipated by the MOSFET so that ...
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2answers
173 views

Chrome plating current control

I am an electronics hobbyist and this is my first attempt at an analog circuit of this type. Mostly I stick to arduino and LED stuff or just wiring up kits, etc. This is my first attempt at designing ...
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1answer
56 views

Want to understand the led series/parallel and parallel/Series combination circuit

I'm Working on LED load design circuit which is up-to 64V@1.2A. I thought of giving LED's in series and parallel combination with switches to control the voltage but while searching I found one ...
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36 views

Effect of op-amp's input offset voltage on stability of constant current load

I'm designing a simple circuit to have a constant current load with good short term stability. The exact current value is not important, as long as it's stable short-term (10 seconds). R1 is the load -...
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1answer
123 views

Inductor as current source

In this schematic for an induction heater, there are two inductors used for current sources. My question is what happens if I increase/decrease the inductance? For example, what would happen if I ...
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1answer
94 views

Can I parallel two constant-current power supplies to drive 1 bulb?

I have a piece of historic equipment that HAS to have an incandescent bulb.* The preferred-voltage bulb (64V) is no longer available, so I'm forced to use 32V bulbs. This one wants 8.4 amps at full ...
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108 views

Circuit for OpAmp-MOSFET based constant current source for 0.2 - 1.5A

I'm a beginner in electronic circuit design and have designed my first Voltage based constant current source using OpAmp driven MOSFET (based on this). The intended current output needs to be ...
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3answers
108 views

Can the voltage drop of an LED driven at a constant current be higher than the supply voltage?

So I've been working on a constant current LED driver project, and I've run into a weird situation. I'm driving 3 parallel rows of 8 LEDs in series (Luxeon 2835 color, green) using a Sparkfun picobuck ...
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65 views

Fixed current source

Thank you for reading this question and forgive me if I sound naive. I am working with a device that uses 4-20mA as set-point, I need 3 fixed values to work with this device: (4mA, 12mA, 20mA) The ...
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1answer
82 views

What's the best way to control DC current in a circuit from 1mA-20mA at 15-30V input with a microcontroller?

I’m trying to create a circuit for iontophoresis that I can control the current of with a raspberry pi or eventually a microcontroller. What would be the best way to control the current? ...
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1answer
66 views

LM317 adjustable constant current source - Why is the voltage between Output and Adj pins is not always 1.25V?

I am trying to create an adjustable constant current circuit using LM317 to drive LEDs of different colors. More specifically, I want the brightness of the LEDs to be the same, therefore, the ...
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1answer
38 views

Current decreasing while measuring the current through a constant current source resistor

My Circuit : The above is my circuit. The Forward drop of LEDs is typically 2.8V and a maximum of 3.15V. I designed the current through the string to be around 21mA, so the emitter resistor is ...
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58 views

Yet another constant current LED driver design, almost

I am about to design a constant current LED driver, with the following requirements: The LED string is fed with 24 V The FPGA interface is 3.3 V The system consist of 8 LEDs in a row, with ...
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45 views

Problem with wide voltage range CC sinking

I want to sink ~10 mA of constant current at wide range of voltages even lower voltages like 10 mV, below circuit suggested to me in one of my older questions: simulate this circuit – Schematic ...
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2answers
156 views

Constant-current driving with LED Driver and Boost DC/DC converter

Novice here, sorry if I'm missing something obvious. I'm trying to drive 4 strips of 6 low-power RGB LEDs each (APF3236LSEEZGKQBKC) on a 3.3V battery. I have a 12-channel LED Driver (TLC6C5912) which ...
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1answer
58 views

Understanding the application of a switching regulator as a constant current LED driver

There is an application note from ON-semiconductors which provides a few diagrams to use a well known MC34063 switching regulator as LED driver. it's around the idea of setting the 1.25v feedback ...
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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 ...
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44 views

first order circuits

I solved this circuit for the current in the 3 ohm resistor and I thought that the current would be continuous but it's not. The circuit is first at stable state, then we turn the switch off and the ...
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2answers
2k views

Building a DeWalt Charging Circuit - Getting out of my depth - Help?

Problem: I'm working on a project that will require a 60V DC (mobile) power source. I'd like to use DeWalt 20V 5Ah batteries to supply this power, 3 in series x 3 in parallel (9 total). Part of ...
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1answer
45 views

Circuit Analysis with constant current and voltage sources

This is a homework question of sorts. I am supposed to find the voltage across AB. I know that the answer is 24 volts by traversing from B to D to C to A adding up voltages of resistors, but should I ...
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1answer
93 views

BJT Constant Current LED Driver - Inverted behavior?

I'm trying to use build a constant current Led driver, using two BJTs (BC338 and BC547). The idea is to be controlled by Arduino's PWM, for dimming. I'm using the circuit bellow. The led is a white ...
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1answer
85 views

Limiting the Current of a Constant Current LED Driver which is Driving a Halogen Bulb

I am powering a 12V, 35W halogen bulb with a MeanWell HLG-100H-20B constant current power supply. The "B" version of this power supply has a really neat dimming control system which lets one control ...
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1answer
497 views

LM317 VS AMS1117 as Constant Current Limiter for LED SMD Boards

i need to design some board like this: each led is SMD 5730 type with current max 150mA in three line and input voltage almost 3.2×7~23V, to create some SMD led board like this: so i have seen this ...
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2answers
58 views

Constant current density

I am reading an article that says ... constant current density of \$−1.0\,\mathrm{A \cdot cm^{-2}}\$ Let's say that I have material that's \$2\,\mathrm{cm^{2}}\$, how would I calculate what's the ...
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673 views

Constant current sink circuit for battery load simulating, microamp current draw

I need to create a constant current sink circuit such that I can simulate current draws from a battery, and analyze the battery behavior. I'll be testing a battery that is 3.1V with 12mAh capacity. I ...
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4answers
66 views

AL8860 Led Driver: inductor placement

I have two questions concerning the placement of the inductor in an led driver circuit using the AL8860 by Diodes Inc.. I'm refering to the typical application circuit below: In their layout ...
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1answer
64 views

L5973 (step down) used in constant current oscillates

For a couple of days i'am playing with a L5973 dc - dc converter whith I want to convert to a constant current driver for 5 or 10W LED's. It kind of works but I get some oscillations in audible range. ...
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173 views

SMPS Constant Current Source only works with low resistance loads

I'm looking for any advice that can be given to solve this issue. I followed the design idea from here: buck regulator to CC source and it appears to work pretty well until I started raising the load ...

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