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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17 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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27 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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40 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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101 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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82 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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44 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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48 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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50 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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84 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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100 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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59 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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100 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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81 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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73 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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50 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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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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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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78 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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92 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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82 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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46 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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43 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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74 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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87 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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2answers
69 views

Constant current LED driver using transistors

I have this circuit: I understood the operation: On power-up Q1 and Q2 are off. There is no collector current so L1 is off. If the digital control input on the left is brought high (5 V) Q1 will ...
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107 views

Working of the below Op-amp circuit

I have seen this circuit at my workplace and I'm trying to understand the working and the purpose of each component in the below schematic. I also happen to note that this was a constant current ...
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87 views

Choosing an appropriate constant current LED driver

I am trying to replace a (suspected) constant current LED driver in a plant lamp as it has a terrible plastics smell. I am searching for a more high quality driver. I do not know then forward voltage ...
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49 views

2 N-MOSFETs in series

I'm trying to design a circuit to charge a capacitor bank with constant (limited) current and then discharge the capacitors through an LED. I've come up with the circuit in the schematic below, ...
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85 views

Driving RGB LED with Constant Current Driver - Only Blue Working

I am driving a common anode RGB LED using a 15mA constant current LED driver. What really confuses me, is that only the blue light works when plugged in. The red and green ones seem to be dead. ...
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138 views

Driving 36V LED from 12V Supply

I have a chip-on-board LED that requires 36V max, 300 mA, but I have a power supply designed for a 12V max, 900 mA LED. The power supply is a pretty standard constant current power supply that ...
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51 views

Constant current MOSFET circuit oscillating, how to get it to stop? [duplicate]

simulate this circuit – Schematic created using CircuitLab I have a constant current load circuit using a sense resistor and discrete quad op-amp set up as a 3 op-amp instrumentation amplifier ...
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32 views

Step up in series with step down DC DC and led driving

I'm having an issue that I can't seem to resolve. I have 100 watts rgb leds that I'm driving with constant current drivers (https://www.amazon.com/gp/product/B019W4C5IE/ref=...
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73 views

Lead acid battery charging @ 0.2C

I am charging a 26 Ah battery with a solar charge controller. The battery's manufacturer recommends charging with 0.1C. Which charges the battery at 2.6A during bulk mode. That is what I was going to ...
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53 views

How to make a constant current-pulse current charger for lithium ion?

I've been doing some research about battery charging system with the CC-PC-CV (constant current-pulse current-constant voltage) method. However I have some questions and need some guidelines for ...
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59 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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87 views

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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22 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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50 views

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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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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59 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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52 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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300 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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78 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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93 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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77 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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222 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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94 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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95 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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111 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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