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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1answer
121 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
99 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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1answer
49 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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1answer
40 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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3answers
19k views

Why N-channel MOSFETs are better than P-channel MOSFETs?

Besides the reason that electron mobility is higher than hole mobility, what are the other reasons of preferring an N-channel over a P-channel MOSFET?
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54 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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6answers
3k views

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
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
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
87 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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1answer
164 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
152 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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2answers
80 views

How to make a current source that supply constant current independent of a voltage power supply?

I want to design the simplest possible circuit that drives an LED. The LED must load the same amount of current whatever the voltage is at the input, between 5 and 9 V. The current could be 10 mA. I ...
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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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2answers
1k views

unstable PWM constant current

I am building a four channel constant current LED driver with PWM control. I have used the following circuit (replicated four times off a quad op amp). The circuit functions OK but as I wind the set ...
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1answer
234 views

PWMing the output of a constant current driver

I have a set of LED panels that come with AC-DC constant current drivers. Is it acceptable to use a MOSFET to PWM the LED (MOSFET goes between the driver and the LED)? Also the microcontroller that ...
2
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1answer
844 views

What is the formula for the dependence between modulating input voltage - output current for two transistor constant current sink

In a constant current sink from the two NPN transistors, load and sensing resistor, application of increasing voltage on the base of the transistor produces practically linear increase in output ...
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1answer
3k views

DAC controlled constant current source

Was given the task of creating the simplest constant current source that can supply up to 50 mA with an ~700 ohm load. I can use any IC's out there. I stumbled across the chip here from linear tech: ...
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3answers
214 views

Understanding constant current circuit

I've been learning about different constant current circuit designs and just recently stumbled upon this one. All I know is that the highlighted resistor is the load resistor and when varied, like a ...
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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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2answers
2k views

Low Overhead Constant Current LED Driver

I have a 3V3 rail and want to run an LED with a Vf=3.1V at 10mA with a constant current source. I'm used to circuits like the one below but the problem is that I only have 200mV of overhead and ...
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2answers
88 views

Constant Current Source BJT

I am stuck trying to determine the applicable formula for the load current. I have used $$I_b = \frac{V_{\text{in}}-V_{\text{be}}}{(\beta+1)R_{\text{e}}}$$ and then $$I_{\text{L}}= \beta I_\text{b}$$ ...
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1answer
52 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
29 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
52 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
73 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
78 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
28 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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2answers
239 views

Reducing heat dissipation in linear current source used for driving a LED

I'm currently using a linear current source to drive a single LED as in here. In my case (following the notation in the link), VDD is directly connected to a single cell lithium polymer battery, i.e. ...
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0answers
20 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
284 views

Is it OK to drive a LED matrix with constant current?

I bought one of these LED matrix modules as described in this Adafruit PDF: https://cdn-learn.adafruit.com/downloads/pdf/32x16-32x32-rgb-led-matrix.pdf The PDF says "they do not have built in PWM ...
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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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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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0answers
110 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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2answers
43 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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2answers
787 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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0answers
84 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
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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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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2answers
59 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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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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0answers
53 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
52 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
85 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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2answers
366 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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3answers
112 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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1answer
209 views

High Power LED Circuit Design & Constant Current Source Question/Feedback

I'm trying to design a dimmable LED circuit board. It's controlled by Arduino with its PWM signals. I'm new to electronics so I have some question regarding my design and knowledge on it. I've ...
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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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3answers
119 views

Meanwell LDH-45 LEDs Glowing When Controller is Off

I'm using a Meanwell LDH-45B-350 Dali driver for currently 4 Bridgelux BXRE-30G0800-D-73 LEDs with forward voltage of 18v at 350mA. The problem is when I switch off the driver, the LEDs still glow a ...

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