# 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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45 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 ...
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. ...
0answers
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 ...
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 ...
1answer
51 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 ...
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. ...
0answers
50 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 (...
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 ...
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 ...
2answers
77 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 ...
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 ...
0answers
19 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://...
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 ...
2answers
85 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....
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 ...
0answers
109 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 ...
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&...
1answer
45 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...
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 ...
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 ...
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 ...
3answers
109 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, ...
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 ...
4answers
159 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
3answers
84 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 ) ...
4answers
77 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 ...
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 ...
2answers
58 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 ...
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 ...
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 ...
1answer
94 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 ...
2answers
97 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 ...
1answer
83 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 ...
0answers
47 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 ...
1answer
47 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) ...
1answer
77 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 ...
1answer
96 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 ...
2answers
71 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 ...
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 ...
1answer
111 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 ...
2answers
112 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 ...
0answers
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, ...
1answer
87 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. ...
1answer
152 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 ...
0answers
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 ...
0answers
35 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=...
1answer
78 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 ...
1answer
57 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 ...
1answer
65 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 ...
3answers
89 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 ...