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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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39 views

How to select the best opamp for a constant current MOSFET driver

I'm trying to create a constant current LED driver. I have found and read information about the miller effect and came up with the schematic below. What are the most important parameters for choosing ...
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0answers
33 views

Solar charger for lithium batteries

I am trying to build a 2s 7.4V solar charged lithium battery pack to power an arduino UNO and SIM900 GSM shield. I have a 12V, 10W solar panel, BMS protection board and a DC-DC CC CV buck converter ...
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1answer
54 views

Variable Constant Current Supply

I've been looking around for a good CCS schematic, and decided to try making a simpler one even if it means it'll behave worse. I need a 12V (would come from an ATX power supply, more than enough ...
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0answers
45 views

Calculate the junction temperature of a MOSFET during pulse

Hi all I have a question regarding using a MOSFET for a constant current source. I have found this question with some answers but it wasn't clear to me yet. I want to create a constant current LED ...
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0answers
27 views

How to add external power source to the adjustable constant current load to do the job with the input voltages less than 4V in the spec? [closed]

So I'm thinking of to power this unit with the external 5V so that I could test the current loading even under 4V in a stable condition. On which points do I have to inject the external power supply?
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2answers
71 views

Figuring out the principal working of constant current source

I've the following circuit: simulate this circuit – Schematic created using CircuitLab I was told that this is a constant current source. I think that the resistors \$\text{R}_1\$ and \$\text{...
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2answers
40 views

Adding push button to CC DC to DC converter to adjust CC

I have a CC/CV DC to DC converter I bought on aliexpress. I does not come with a screen so I attached to it an LED voltmeter ammeter. Anyway everything works fine. One thing though, I don't know at ...
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0answers
37 views

Adding Current limit for DIY DC-DC converter (CC/CV battery charging)

I was following the circuitry by great Scott for the DIY buck converter here: https://www.youtube.com/watch?v=m8rK9gU30v4 . Created a converter that gives 0-23V on 24V supply. After this i wanted to ...
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1answer
120 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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1answer
51 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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1answer
113 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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2answers
75 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
574 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
29 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
194 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
61 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
49 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
110 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
217 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
131 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
75 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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0answers
73 views

Calculating value of a current limiting resistor in a constant current circuit?

I am using 12 leds in series with 3.0-3.4 v forward voltage and 400-500mA forward current (these values are from the datasheet). I am using a constant current led driver(24-40v and 580mA). My problem ...
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4answers
103 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
58 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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1answer
61 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
47 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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0answers
61 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
129 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
116 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 ...
0
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1answer
72 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
356 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 ...
2
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3answers
621 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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0answers
113 views

Laser Diode Driver and Cooling

I am a newbie at analog design, and trying to design a laser diode driving circuit and TEC cooling circuit for a 14 pin laser diode, such as P1550-ADF-B: 1550NM ADF LASER DIODE which has forward ...
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1answer
94 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
98 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
69 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
72 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 ...
0
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1answer
49 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
75 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. ...
4
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2answers
123 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
270 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 ...
2
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5answers
231 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
282 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
301 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
545 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: <...
2
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1answer
140 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
207 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
185 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
64 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, ...
3
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1answer
236 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 ...