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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40 views

Handle fast signal using OpAmps: ADA4891 - 2

Relating to "Handle fast signal using OpAmps: ADA4891". I added a high-side switch and a constant-current circuit. However, the hold voltage immediately drops when switching the high-side ...
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1answer
77 views

Can a constant-current LED driver with a reference resistor be dimmed?

I have a scenario similar to Tuning a constant-current LED driver, per channel: also considering use of two TLC5928 but with If <= 20 mA per channel 28 channels have Vf ~ 8V < 9.6V 4 channels ...
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2answers
65 views

How can the NSI45020T1G claim to "turn on immediately"?

The On Semi NSI45020T1G, a simple two-terminal inline current regulator, claims in at least two places that it "turns on immediately". However, it cites a capacitance between 2.5 and 2.7 pF....
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80 views

Balancing current with resistors when driving parallel strings of series LEDs with constant current

I'm designing a light source that will employ a grid of LED emitters powered by constant current drivers. The LEDs will be laid out in a parallel/series combination, in rows of 8 emitters in series, ...
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1answer
166 views

UC3843 PWM Duty Cycle Variation With Temperature

I'm trying to implement a constant current solenoid driver (it's more of a constant wattage pwm driver, current changes with supply voltage which is fine) using UC3843 PWM driver. I'm using the ...
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2answers
59 views

How to regulate battery voltage

I am using a LiFePo4 battery 26.5 V, 18 Ah in my project where I am using three DC motors I need a constant voltage for my motors but as the load on one of the motors increases it affects the speed of ...
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2answers
107 views

Controlling High Current LEDs with an ATmega328

I am trying to build a circuit design that has 4 LEDs that will need more current than the ATmega328 can give out. I will want the LEDs in parallel so I can control them all individually. Because they ...
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1answer
58 views

LED Dimmer circuit accidentally damaged

I am currently working on a prototype system that uses these 3w LED drivers (I am using the one with the picture at the right). It uses the XL4001E1 CC DC-DC converter capable of outputting 700mA to ...
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461 views

LM317 as current regulator - problem

I'm driving an LM317T from a variable PSU and using it to run 6 x 1W 300mA LEDs in series, approx 3.5v each. The Output pin goes to a 4.7R resistor then to the LEDs, and the Adjust pin is connected to ...
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1answer
30 views

High-power LED Shunt Protection using Zener diodes with constant-current LED Driver

I'm about to build a custom high-power lamp. The lamp will operate a total of 60 high-power LEDs (operating point: 2800mA @3.1V per led) connected in series. The original plan was to have the LEDs ...
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2answers
262 views

Super-capacitors to heat resistive wire

I am looking for help/insight into the feasibility of using the stored energy in supercaps to heat a short length of nichrome wire, or a vape coil. I have nichrome wire that is 0.040 size, at 0.408 ...
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1answer
47 views

Knowledge requested for WS2811 Based RGB LED driver Module

Design of LED Module based on WS2811 LED driver IC (Only Red-channel is shown). To the right of the schematic you will find a simple, cheap and robust constant current LED driver. The current for the ...
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3answers
85 views

Use LM2596 as constant current source

I am trying to make a constant current of about 0.8A to control a 13W LED using the LM2596 buck regulator. My idea is to use a variable resistor to connect as 2 pictures following to get that ...
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68 views

Using constant current and constant voltage power supply with LED strips

I have a Meanwell 12V power supply (ELG-200-12) which is constant voltage and constant current. Note 2: I want to power t one 5 meter 12V LED strip that consume 11.52W/m with it. The specifications ...
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47 views

Modifying a CC converter to act like a CV converter?

I bought 3 DC/DC buck constant current converters instead of constant voltage converters (my intent was to power multiple servos with each one, and these were the only buck converters that fit the ...
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3answers
159 views

Current mismatch in digital constant current source

For an electrochemical etching process I am trying to put together a battery powered, somewhat accurate current source able to provide 1mA to 5mA to a load with a varying resistance. (to be specific, ...
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113 views

Connecting LEDs in parallel using constant current driver

I need to drive 4 high power LEDs. Because of their high power, they cannot be connected series as the voltage required by 4 in series would be too high. Their high current requirement (500mA) also ...
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2answers
122 views

Zener diode based voltage regulation with transistor for current boosting

I took this circuit from the book Diode,Transistor & FET Circuits Manual by R.M. MARSTON. It is for wide range voltage regulation. I tested this circuit and it works very well. The main problem ...
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193 views

High voltage adjustable constant current source controlled by MCU

Background: I need a microcontroller adjustable high voltage (300V) constant current. Source: High voltage boost converter. Load: Gas discharge lamp (20mA max). Can only be switch from high side. ...
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58 views

Driving LED downlights in series fails

Problem I'm having trouble understanding why driving two or more of my generic Chinese brand 18 W LED downlights in series results in the LED driver shutting down due to overload, while the driver ...
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1answer
81 views

Saw tooth current source instead of constant current source

I saw this circuit and wondered how the capacitor would charge when the constant current source is replaced by, say, a saw tooth current source. In order to find the voltage across the capacitor from ...
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1answer
55 views

How to drive dozens of LEDs with the same current without a constant current LED drive IC?

Let's say I have an array of many indicator LEDs that I need to turn on/off independently; the LED current is about 1 mA. In the past I used constant sink LED driver ICs such as the TLC5916 as shown ...
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2answers
267 views

Tuning a constant-current LED driver, per channel

So, I am using a constant-current LED driver from the TLC592x series. This driver allows you to tune the current for all of its channels with a resistor RIREF. The outputs are used to drive a LED bar ...
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2answers
70 views

Constant ramp not behaving as expected in SPICE simulation [closed]

Looking for some advice on creating a constant (linear) ramp which meets a certain specification, I've designed this example which works well in ideal simulation but I cannot get it to work in SPICE. ...
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2answers
348 views

What capacitor voltage rating should I use?

I am designing a PCB layout using the SIC438AED-T1-GE3 buck converter. I am trying to understand what voltage the 'PHASE' pin will have, as it needs a capacitor like this: I need to know the voltage ...
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1answer
62 views

Buck-boost LED driver returning to Vin

I am working on a design involving driving a string of 22 LEDs in series using a constant current. The relatively high voltage required (~66V) has lead me to look into buck-boost LED drivers. I have ...
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1answer
50 views

What is "SW current limit" on Led Driver?

I am trying to understand the maximum current capability of this LED driver IC. I am pretty sure its on page 4 labeled as "SW current limit": But I want to be sure, as I cannot find and ...
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1answer
69 views

Switching buck/step down converters with resistive lamps

I need to power a halogen lamp with a constant power (5 V 900 mA) using a constant current switching driver IC. I will not use an LDO IC, since my power supply is 24 V and it will generate too much ...
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3answers
100 views

Voltage Controlled (w/ op amp) Wilson Current Mirror Can't Actually Mirror (Missing something)

I'm working on a current mirror circuit and I'm in a little bit of a problem. I have a current mirror circuit, which is supposed to, well, mirror the current, except that the current in the "copy&...
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3answers
109 views

1uA-step CC circuit / DAC with 1mV output and sub-mV offset

I'm creating a circuit that is supposed to output constant current between 1uA and 2mA with 1uA steps. It took me a while to come up with the circuit that does just that (I think). Of course, there ...
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3answers
83 views

TIP122 constant current problem

I am driving a TIP122 via the DAC of an ESP32 which only reaches 3.16V The solenoid is rated at 2.4A at 12V. Irrespective of what I put the supply voltage up to I can't obtain more than about 2.1 ...
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30 views

Driving LCD backlight using boost converter (Feedback loop & Constant Current)

I've been researching LCD backlight circuits (for my STM32-based project), asked questions before, but there is another question I have about the matter. I have noticed that some boost converters (I ...
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1answer
81 views

Korad Power Supply Flashing and Clicking: Both CC and CV

I'm testing a stepper motor (NEMA 34, variable 30-100v, 6 amp stall current). I'm using a variable DC power supply (Korad KD3005D, up to 30v, 5A) to power it. When I supply power to the motor (...
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1answer
104 views

How to identify CC and CV mode for given readings of load resistance, voltage and corresponding load current?

I want know which is the correct way to approach problems where we have to identify CC and CV mode. Let us consider a question - For various load resistors, connected across \$Channel-1\$ of the DC ...
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52 views

LED driver/analog adjustable constant current source with constant output without PWM switching?

I am using 3 halogen lights with 5V/0.5A each controlled by a constant current source (or basically "LED driver") because of light accuracy. Right now I am using the PT4115 (step down led ...
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4answers
379 views

Will a current mirror prevent thermal runaway of these LEDs in parallel

The source is a constant current LED driver. I found that connecting the LEDs in parallel caused thermal runaway with one LED consuming nearly all of the current with its temperature constantly ...
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1answer
34 views

Help understanding current sense application note to inject feedback into buck converter

I am trying to understand this application note using MAX4173H to inject feedback into a MAX1692 step-down converter. How to they determine the precise point at which the current limit will kick in, ...
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91 views

I need to design 182 RGB LED array circuit

I looked for designs for PWM dimming RGB LED arrays on the internet, and I found this circuit with a current mirror: As the title says, I am designing an LED panel with 182 RGB LEDs. I think the ...
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98 views

LM317 digitally-controlled constant current power supply

I'm designing and simulating (with the intention of building) a lab power supply. I like a challenge so I'm trying to make it digitally controlled (also because I'm a programmer). I'm doing this for ...
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3answers
168 views

Selecting base resistor on op-amp controlled constant current LED driver

How do I calculate the appropriate value for R1 and R8 so I don't get extra current flowing through my transistor bases at low voltage? simulate this circuit – Schematic created using ...
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1answer
135 views

How does amplitude dimming (CCR) work?

When a LED driver dims using constant current reduction (CCR), what voltage and current is sent to the LED chip at the various dimming levels? Say I have a CCR-compatible LED chip which takes 500mA ...
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1answer
90 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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1answer
54 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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1answer
52 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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0answers
40 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
328 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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2answers
63 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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1answer
35 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
566 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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3answers
394 views

Constant current source drop

I need some help understanding a little (I guess) thing here. I was trying to understand a constant current source but something happened that I can't understand. When I did a simulation in LTspice ...

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