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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384 views

Constant current source with shunt fet

I'm want to create a project with a LED strobe with IR LEDs. As LEDs the Osram SFH 4249-UV will be used in strings of 15 LEDs and 32 strings parallel. This results in a Vf of 34.5 - 45 V and a If of ...
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62 views

Constant Current Regulator position in a series circuit

I'm designing a circuit with 3 LEDs, a CCR (NSI50350), and a power supply in series. My question is: Does it matter where I place the CCR? Can I design my circuit this way: +V--LED1--LED2--CCR--LED3-...
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424 views

in zener diode current source, to provide constant current, what resistor, etc do I have to use?

I have a load that has varying resistance and want to know the change of resistance by measuring the voltage with constant current. The figure below is known to provide constant current. But I have no ...
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3answers
154 views

LED driver high current and voltage

For a project I have to design a led beacon that will consist of +400 LEDs. These LEDs will be driven only a short amount of time maximum of 3% duty cycle (frequency: 100Hz, pulse: 300us). The LEDs ...
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2answers
869 views

Digital Current limiting with MCU

All current limiting circuits I've found until now use some sort of analog Logic with Op-Amps to limit/control the current. (Why) is no digital current limiting used? I would imagine a shunt resistor ...
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0answers
44 views

SMPS topology for combination of current controlled rail and fixed voltage rail

I'm looking at designing a LED driving power supply that can interface with a universal AC main input (~90VAC-260VAC) and produce 2 rails at the output; one a current controlled rail, and the other a ...
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2answers
3k views

Constant current led dimming

I have a few panel lights which come with normal non-dimmable constant current drivers. I want to add a dimming feature to them, please suggest me a circuit that I can use with Arduino/ESP8266 to ...
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0answers
610 views

Constant Current LED Driver Output Control using PWM

I want to control the brightness of a led which is powered by a constant current driver. On utilizing a MOSFET and pwm signal from an arduino uno the led starts to fade in as the duty cycle ...
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1answer
62 views

Driving 8 x 117W COB LEDs [closed]

I am currently attempting to design a LED grow light using the following LEDs but I am having a very hard time finding a sufficient power supply. 8 x Lumileds - SunPlus CoBs DataSheet 51.7 V, ...
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4answers
197 views

Capacitor bank as a constant current source?

Can a capacitor bank of high power density, be integrated to a circuit such that it acts as a constant current source to a load? Even for a short duration of time.
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4answers
491 views

Constant current source gets heated

I am trying to control some power LEDs using a microcontroller. For this I plan to use a transistor based constant current source to protect the LEDs from getting damaged and PWM on the base of the ...
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2answers
1k views

Why constant current led driver is not used in parallel led strip? [closed]

I know that the constant current led driver is not used in the parallel led strip. and constant voltage led driver is not used in the series led strip. can anyone explain me with the example that why ...
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1answer
289 views

AL8860 LED driver does not output required constant current

The LED driver circuit i've made here does not output a constant 1A current. With an input voltage of 12V and 9V total Vf on the three LEDs (CREE LED star), the current is only 0.65A. Am I ...
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4answers
2k views

Inductor with constant current source

Hii can anyone explain how to do this. Its Given Answer as 6A. What exactly happens when a constant current source in series with inductor? TIA
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3answers
129 views

Constant Current Load fails to recover after setting load to zero

I'm trying to design a Constant Current load for testing battery cells using the TLC070 Op Amp (what I happen to have on hand) and a low pass filtered (150Ohm + 470uF cap) PWM input from an Ardiuno. ...
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2answers
177 views

Trying to split the current output of an LED driver

I am currently using an 8 channel LED driver wher I have set the outputs to produce 20mA of constant current. Problem is I have 11 LEDs to drive. So I have decided to connect two LEDs in paralelled to ...
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1answer
98 views

Constant current circuit load and without load for voltage measurement?

How can I control the constant current block? What I need? I need to calculate voltage with constant current load (I = 100ma and after some time I need to calculate voltage without load (I = 0), for ...
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2answers
87 views

Zener Shunt Regulator Question

I want an alternative low component, transformerless power supply for low power DC projects, I have used Shunt Regulators in the past but never with AC. Below I have proposed a AC to DC shunt type ...
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3answers
2k views

Making an efficient constant current source

I need help making an efficient constant current driver. I want to power my home with LED light strips for lighting and decorative purposes. I need to be able to turn each strip on and off ...
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0answers
120 views

Designing a constant current pulse circuit

I'm looking for help designing a constant current pulse through a variable load impedance of 10-100k (R4). The ideal response is shown below. This waveform was measured from an off the shelf ...
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1answer
187 views

Analyzing a constant current source

I'm looking at some old chemistry education literature where a constant current source was proposed (J. Chem. Ed. 1969, 46(9) p613, link). I am trying to better understand the circuit and could use ...
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1answer
163 views

Internal constant current driver for LED short circuits and blows when connected to AC main (120 V) without DC load

I have AC 85-265V to 0.3A 8-12W DC 22-40V Internal constant current power supply for LED spot lights. This is the exact model https://www.lightinthebox.com/en/p/0-3a-8-12w-dc-22-40v-to-ac-85-265v-...
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2answers
151 views

Connect VGA cooling fan (12vdc - 0.1A) to constant current driver (120Vac to 12- 22vdc @ 0.3A)

I have an AC driven COB LED which can be connected directly to the AC main in house (120v). I would like to attach a cooling fan to the COB which requires 12vdc @ 0.1A. I have a constant current ...
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1answer
1k views

Analysis of a modified Howland Current Pump

I am trying to do an analysis of the following modified howland current pump based on the circuit description in the datasheet of the LMP7701. This is a voltage controlled current pump that is driven ...
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1answer
325 views

Laser pointer circuit

I've got a small red laser pointer from a chinese ultrasonic distance meter, which has a small regulator circuit (6mm x 7mm) with SMD components. I guess that is a constant current to drive the laser,...
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1answer
2k views

Constant Current Led Driver (non dimmable) to work with PWM

I have 18W lamps that came with non dimmable led drivers. Ive found datasheet for the main chip (ws3441), which included schematics: and internal block scheme of the chip: I'd like to add dimming ...
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3answers
2k views

Understanding constant current LED drivers (ac to DC)

I am trying to understand the way constant current LED drivers work. Lets say I have a driver with these specs: Description: Power: 18W Output Voltage: DC 36-63V Output Current; 300mA Input ...
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2answers
365 views

Driver selection for high power LEDs

I'm currently working in a project where I need to control the intensity of 24 high power LEDs in 5 levels. I'm planning to use LumiLeds L1CU-BLU1000000000 (https://www.lumileds.com/uploads/705/PB198-...
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2answers
160 views

Voltage doesn't add up in LED circuit

The circuit consists of following: simulate this circuit – Schematic created using CircuitLab And video on this link. Summary: When there is no current flow on the circuit, supply voltage is ...
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2answers
107 views

Over-voltage on a current regulator

Let's say I have a current regulator, or a LED driver, set at 4V that can sink 20mA. If I connect a white LED rated 20mA at 4V to it, then everything is fine. But what happens if I replace, in the ...
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2answers
185 views

High power LED array

I’m designing SLA 3D printer and I need to design UV LED array for LCD screen backlight. Preliminary design is 5x3 (5 parallel lines with three LEDs in each). All LEDs will be soldered on PCB. The ...
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1answer
135 views

Help Powering 2x10W LED using a 15v 1A power supply

Beginner here, trying to build a lighting using two 10W SMD LED'S. Please advise me for a better and efficient setup. Here are my specs. Power Supply DC 15v 1A LED specs: Input voltage 9-12v ...
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2answers
115 views

LEDs + Constant Current Driver - Discharging the Circuit

I have a project where I made a series of high power Osram OSLON blue leds using custom boards on aluminium PCB. I just put 16 LEDs in series and joined them to an appropriate constant current supply. ...
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2answers
256 views

Current-limiting for LED when Vf = Vdd [duplicate]

I need to drive several indicator LEDs at <2mA. Each LED has a nominal Vf between 3.2V and 3.3V (Vf max up to 4V). In the past I've had the luxury of (a) current-limiting resistors or (b) ...
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2answers
842 views

NPN transistor as variable resistor for cc LED operation

I want to build a simple circuit, to control a chain of LEDs via an external PWM signal but limit their current. Unfortunatly I'm not aware of all the effects that the transistor would introduce to ...
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5answers
1k views

BJT Constant Current, Resistor Equations

I am looking to design a simple constant current circuit to draw a precise load from a variable voltage rail. The voltage rail (V+) should be 10V-20V in normal conditions, but it is possible for V+ ...
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4answers
772 views

Driving 10W RGB LED Red Channel Issue

Been a while since I have been on here but I do not know where else to turn for help! This is more of a hardware issue than anything so i do hope that I am in the correct forums to be asking, if ...
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3answers
567 views

Converting appliance LEDs from constant current to constant voltage to allow for dimming

I'm trying to implement dimming control for the lights in my kitchen hob extractor. The lights are 4x LED spotlights which are each 3v 700mA (2.1W). They are currently wired in series to a 700mA 10W ...
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2answers
2k views

How to calculate this two transistors Constant Current Source circuit?

I came across a constant current source calculator at Electronic Product website:enter link description here For example, for a 13.5V input, 300mA output, it comes out the following parameters: <...
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1answer
319 views

~40 uA current sink… what current mirror topology to use?

I need to sink a constant 20-60 microamps from the inverting input terminal of an op-amp in order to shift the output voltage upwards a bit. This is a pretty low-speed circuit, with little spectral ...
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2answers
785 views

Add constant current to an XL6019 module

I need to add a circuit to an XL6019 module to get a constant current (adjustable) source to drive some SMD LEDs. I'm no expert in complex circuits and my level of knowledge in electronics is basic. ...
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1answer
562 views

Building a VCCS with AD8220 Instrumentation Amplifier

This question is to help me with my work in building a VCCS for the excitation signal of an Electrical Impedance Tomography measurement set-up to use with EIDORS. I have only basic knowledge in ...
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0answers
79 views

20 mA current loop speed/distance trade offs?

By 20 mA current loop, I'm referring to digital current loop communications, e.g. the standard used by old Model 33 teletypes. (Image credit: By Rama & Musée Bolo - Own work, CC BY-SA 2.0 fr, ...
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1answer
294 views

LM317 intermittent current source

I need a 50 mA current source despite the load value (resistor LOAD), and I need the current flowing just when the microcontroller says so. It works fine with LOAD = 0 ohm and IL = 50 mA, but when I ...
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4answers
1k views

RTD sensor circuit design

Design Criteria For a project I'm making I want to measure temperature using a 10 bit ADC on a MCU. I don't care for absolute accuracy but I would like precision down to around 1/10th of a degree C. ...
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1answer
78 views

Wiring a voltage specific device onto a constant current circuit?

I've got a bunch of LEDs wired in series to a constant current driver. The driver runs the circuit at 500mA to 700mA (I can vary it up or down a little) and can supply 50 to 100 volts, maximum 60 ...
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1answer
276 views

What is the operating principle of this single-transistor constant current source?

Sorry if this has been asked before; I'm still learning about electronics and probably don't have the right vocabulary to describe this part's functionality. I came across an interesting part made by ...
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1answer
701 views

Constant Current Load op-amp ref voltage limit

I am trying to build a constant current load circuit described in DIY-Constant-Current-load I wanted a 20mA CC load, so I chose 4V at R2-pin2 and 200ohm for R1. After constructing the circuit, i ...
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1answer
374 views

How do i get this constant current circuit stable?

Im making a battery tester / discharger. For this i'm using a constant current circuit made with an opamp and a mosfet. I built and tested the circuit by itself with around 3-4A and it was stable. I ...
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0answers
33 views

Help me set constant current to 1.5mA output and LED to 20mA [duplicate]

I don't understand enough to accomplish this, constant current output to 1.5mA LED current to 20mA its simply been too long since I learned these things. Im only modifying an existing (likely popular) ...

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