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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78 views

Is it OK/Safe to use a parallel resistor to divide current driving an LED chip?

Still figuring out some fundamentals here, so forgive me if this is a newbie question, if I'm totally missing the mark, or if my math is incorrect (hoping to learn, even if this is all wrong). I have ...
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49 views

How to avoid sparks over the load at high voltages?

I built a constant current source: simulate this circuit – Schematic created using CircuitLab When connecting SW1 it use to spark over SW1 contacts because output of OA1 was always clipped to ...
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49 views

How do I make an integrator to always output LOW and output HIGH only when needed?

The circuit is a constant current source: simulate this circuit – Schematic created using CircuitLab When SW1 is open and no load is connected output of integrator is clipped to positive rail, ...
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29 views

How do LED drivers with current control work

I'm reading the datasheets of this two LED drivers: FL7760 STCS1A The main obvious difference is the first driver requires an external MOSFET, while the second one has the transistor built-in. But I'...
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1answer
146 views

Constant voltage charging phase of Li-ion batteries

I've read on batteryuniversity.com that the constant voltage (saturation) stage of Li-ion charging adds approximately 10% of SOC compared to charging with only the constant current (CC) charging phase....
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51 views

Multiple CC/CV charge controllers in parallel?

Can multiple cc/cv charge controllers (TS1052 for example, which is rated for 100mA drain current) in parallel configuration to achieve a higher drain current? (input signals also connected in ...
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41 views

Strange Behavior for a Dimming Circuit

I am hoping that some of you may be able to decipher some strange multimeter measurements (see table). I am trying to figure out how an already existing LED dimming circuit works (is it constant ...
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1answer
27 views

Understanding Meanwell CV+CC driver characteristics

I have an LED fixture that can take 2 to 2.5 amps. Vf is around 36 volts. I am planning to use Meanwell ELG series driver to power it up. [Datasheet here] This particular model can work in CV+CC mode ...
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3answers
333 views

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 ...
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243 views

Why is this digital output circuit non-linear to the load?

I'm simulating a DAC which puts out 0-20mA, but in practice, the output varies depending on the load of 300 ohm resistor. If I using a 1k ohm resistor, then I get a different output current. If you ...
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2answers
71 views

Will adding a pole in the loop gain make the system more unstable?

In the design above, the circuit designer added a low-pass filter in the feedback path of the op-amp for loop stability. Won't adding a pole to the feedback factor actually make the circuit more ...
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1answer
136 views

What does the collector resistor on this LED driver circuit do?

The resistor in question is R2. The below circuit provides roughly constant current above a certain Vcc. For R2, I arrived at the value by trial and error by checking simulation outputs. I would like ...
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1answer
106 views

MOSFET getting hot. Is it normal?

I am using a Diodes AL8871Q IC to power a XHP70 LED at 3.4 A. My thermal cam shows the MOSFET at 108 degees C after 60 seconds with PWM control running at 40% duty. Is this expected? MOSFET I am using ...
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68 views

Constant Current of an XL4016 Buck Power Module [duplicate]

Hi have this buck converter : Step Down Buck 9A 300W Converter 5-40V To 1.2-35V Power Module XL4016 I've done my research, read some posts and articles but I'm still quite confused, some say a ...
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41 views

DC Output current control [duplicate]

Can I use a 14v 2A dc adapter on 12v 1A dc rated device? Now what i did is by a buck controller i set the voltage to 12v but there is no variables to control the current in that buck control module. ...
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60 views

Calculating constant current buck converter ripple current

For building a constant current LED driver, I'm looking at the TI LM3407 datasheet: https://www.ti.com/lit/ds/symlink/lm3407.pdf For calculating the necessary inductor, there's several things I don't ...
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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 ...
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1answer
61 views

Night LED Lamp with PIR Sensor - Guide to calculation parameters

I would like to make some LED lamps for night use, therefore at low intensity, just enough to see where you are walking, but almost without waking up. ;-) It should only turn on when it detects ...
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1answer
35 views

Linear voltage regulator current source high side/low side regulation

My application requires a constant current source for driving LEDs across a large voltage range (60-300VDC), and also the possibility to do this on both the high side and low side of the LEDs. ...
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0answers
55 views

PWM Switching of 0-200mA Laser diode driver

My main goal is to create constant current source as laser diode driver between 0-200mA, controllable by 0-3.3V analog input from MCU, And can be modulated (ON/OFF only) by square 0/3.3V PWM signal (...
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1answer
77 views

LM317 - Why could I not get more than 200 mA from the output?

My task is to heat a coil, with a resistance of approximately 0.8 ohm. I need to make a constant current source to make it work correctly. I want to use LM317T as a constant current source, but I ...
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2answers
78 views

Bad on output of Constant-Current source

What I'm trying to do? I'm making a constant-current source based off an existing design. The specs of the existing design are: Existing Design The design is of a constant current source capable of ...
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2answers
98 views

Constant Current LED Driver using LM358

I have been working on a project for ACDC Constant LED driver with 1.2A, 36V specifications. While going through the internet, I found one of the circuit and couldn't understand the working the of the ...
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0answers
29 views

Is backfeeding BD9C601EFJ buck converter IC a problem?

So I've got a circuit like that [Values are completely random, I didn't set them yet, the question is only about topology]: The circuit is intended to charge a 2S battery through F3, however when the ...
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0answers
31 views

Charging 18v Ni-CD battery pack with DROK voltage regulator

I have an 18v 2000mAh black and decker drill battery that I want to charge and use in the mean time while I wait for a proper charger to arrive. I have a DROK Voltage Regulator/Buck converter (https://...
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1answer
28 views

Supernodes with Constant Current & Voltage Sources: Voltage = Current

I am a technologist trying to improve my understanding of electricity by reading a textbook. I am reading Fundamentals of Electric Circuits and something that keeps popping up when solving the ...
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2answers
89 views

Current limiting rectifier with capacitive reactance (isolated)

[UPDATE] I have answered my own question with links to experimental data and theory. Please expand on that answer if you can for the reference of future readers. Thanks for replies so far and ongoing....
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2answers
65 views

PV panel -a current source or voltage source?

I'm reading about PV behaviour and am confused on whether a PV panel/cell would be considered to be a voltage source or current source or both or neither (from the characteristic IV curve). The IV ...
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0answers
123 views

Adding an adjustable constant current option to a LM5175 circuit

Disclaimer: I'm no electronics engineer and I have no experience in this kind of circuit! I do occasionally design simple analog circuits and PCBs, barely messing with opamps. Context: I'm about to ...
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0answers
87 views

22V 2A current limiter circuit

I need to build a simple circuit to limit the current of a 22-25V input (from two car batteries) to 2 amperes - to avoid frying a battery charging circuit. I found this one - "General Purpose&...
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1answer
46 views

Current control for Li-ion charger

Can someone explain how this part of the circuit works? Why do they use PNP (Q5), NPN (Q2, Q3...
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0answers
57 views

How to reduce noise Buck converter at constant current mode ACT4088

Hello i am using a ACT4088US-T (datasheet here) Buck converter and i made it to run in constant current mode 500[mA] through a Diode (D5): Everything works fine. It draws 500mA no matter the load i ...
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2answers
53 views

MIC29712 in constant current mode

[EDITED] I ALSO ADDED THE LAMP TO MY DESIGN WHICH I FORGOT I am trying to use a MIC29712 in constant current mode to draw 4A for my lamp. The power supply is 15V and can give up to 8A. Here is the ...
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4answers
87 views

Simplest way to limit current from MCU pin

I'm trying to build a very simple flyback power supply capable of only about 1mA. The basis is to supply a PWM wave to a 1-1 sepic inductor (shielded coupled inductor). The problem is that it would ...
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3answers
121 views

Error in constant current sink circuit and current regulator

I have found a circuit online, which is supposed to be a steady current sink: simulate this circuit – Schematic created using CircuitLab and every time I simulate in LTSpice, if I change Vc, ...
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0answers
61 views

OpAmp current source does not work as expected

I'm trying to build a constant current source for 2mA (IEPE accelerometer). The simulation works as expected: But the real circuit is sourcing only about 240µA. Vgs is around 2V; I thought this will ...
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4answers
357 views

PNP transistor constant current source

I would like to know if it is necessary to add a base resistor to the Q1 transistor in the below schematic? The complete schematic: https://ibb.co/kc5QkSC
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3answers
92 views

BJT Constant Current Driver

I'm currently working on this circuit and I ran into 2 questions that I'm not sure I understood them correctly ( I have U1 = 15V , URE = 2 V , β = 180 , UCE = 5V and a constant current I = 2mA ) ...
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4answers
88 views

Powering 12V 35W halogen bulbs with a constant current supply

I'm revisiting an old project, and I want to see if there is anything I could have done differently, or if I missed any important details or considerations. Basically, I used a constant current driver ...
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1answer
45 views

Constant current regulator enable when current and voltage reached

I have constant current regulator which consists of one transistor, two diodes, enable transistor (1.5k ohm) and resistor connected from emitter to GND (~15-20ohm) as visible in schematic. It limits ...
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2answers
64 views

What voltage to charge a single NiCd cell?

Ok. I have researched and not found any results abt this question. What is the voltage range for charging a single NiCd cell? I also have another question: what is the recommended constant current ...
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2answers
70 views

Small footprint constant current source / voltage regulator [closed]

I'm making an edge-lit snowflake out of acrylic. It's lit from the center; the LEDs are mounted straddling a circular (40 mm diameter) PCB. I'm using 24 white LEDs, and since I don't want to work with ...
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1answer
36 views

LM317LZ LED driver circuit - wrong output current

I built a minimal LED driver circuit using a LM317LZ and a 12 Ohm resistor between OUT and ADJ (identical to e.g. Understanding this LM317 LED Driver circuit). According to the datasheet this should ...
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1answer
115 views

LM338 is getting hot and stop working when we try to flow current more then 1A

I try to make a 30 V, 5 A power supply using LM338 (without heatsink) voltage regulator IC. In my case the value of R1 is 100 Ω and R2 is 2.2 kΩ. then it gives 29.6 V as output. when we connect a 10 ...
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2answers
103 views

LM317/338 constant current open circuit

Suddenly I am baffled, as a hobbyist I made a variable constant current power supply based on LM338. But I never thought what could happen if I accidentally turn it on without load, will the voltage ...
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1answer
84 views

Powering a constant current strip with a constant voltage supply

I have an application where I have the following components installed. 277 Vac to 48 Vdc Constant Voltage Driver (MeanWell) -> 48 Vdc CV PWM dimming interface controlled by 0-10 V -> constant ...
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52 views

How to strobe high power led while maintaining constant current

I am trying to make a high power tv-be-gone. For those who don't know, it uses arduino or attiny to run through every IR power code for most tv brands. I have made regular ones that use several 5mm IR ...
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1answer
52 views

Achieving long term stability of a MOSFET current sink

I've got 176 infrared LEDs embedded in CNY70 optical reflectance sensors, which I would like to power, and I'd like to ensure that the current supplied to any given LED is +/-1% stable (or better) ...
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1answer
80 views

Understanding constant current source in amplifier stage

I am teaching myself electronics in my spare time and I am trying to look at circuits and understand how they work. I am currently studying amplification and transistor basics, and I have started ...
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100 views

Constant current limiting circuit

Can someone help me understand the working of this circuit: My questions : Please explain me how this circuit will work in its entire operation range. I am not able to understand the purpose of the ...

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