Skip to main content

Questions tagged [constant-current]

Questions regarding constant-current supplies, devices and applications, as opposed to constant-voltage supplies. The voltage can vary while the current remains the same. Common in LED lighting applications and battery charging.

Filter by
Sorted by
Tagged with
0 votes
0 answers
28 views

Find out safe current for led strip in series [closed]

I have some huge led stripes and I want to give them a second life by adapting a constant current driver. The data I have about the old driver it's the output voltage was around 150VDC per channel. ...
Broom Stick's user avatar
0 votes
1 answer
37 views

Can a voltage higher than LED maximum be used when using constant-current LED driver?

I am planning to use these components: TLC59283 CREE J Series 5630 LEDs Specifically, I want to create a setup like Figure 9-1 on pg. 22 of the TLC59283 datasheet. Currently, I am trying to choose a ...
JustHeavy's user avatar
  • 303
0 votes
1 answer
44 views

Constructing the voltage as a function of time for a circuit with a capacitor and resistor under a current source

I have a circuit as shown in the image. I want to derive the formula for the voltage V(t) as a function of time; when a constant current source is applied.
Hoài Nam Nguyễn's user avatar
0 votes
0 answers
27 views

DAC errors and voltage mapping (0.3-3v to 0-2.7v)

Using MSP0G1505 MCU. It has a inbuilt DAC. I thought it could give me 0 to vdd as output but it seems it can only give 0.3 to vdd-0.3 as output. This happens because of the offset and gain errors. ...
funtastic rdj's user avatar
0 votes
2 answers
43 views

Sinking and sourcing current from and to the output of the op-amp

I need to have a set-up to sink and source current from the output of an op-amp to measure the maximum output current of an op-amp. This is the test set-up I thought of: If the maximum output swing is ...
Fateme Mrbs's user avatar
0 votes
1 answer
34 views

What is the point of two enable signals in PT6957 LED driver?

I have a 48 x 16 matrix LED display E-MOTIVE Q-B-069B (no datasheet), and during reverse engineering I found 4 off PT6957 there. PT6957 is 16-bit shift register, latched with constant current drives. ...
smajli's user avatar
  • 940
0 votes
3 answers
75 views

How do constant-current drivers implement voltage limits?

Suppose I have a constant-current LED driver providing a stable 700mA between 8 and 10 volts. From my understanding, the current is kept the same (hence constant current) by increasing and decreasing ...
lemon's user avatar
  • 614
1 vote
6 answers
293 views

What happens if I feed a diode (in the forward direction) from a DC current source?

Can I forward bias the diode using a a DC current source? Is there a minimum forward bias current that switches on the diode? How would the voltage on the branch be impacted by the diode? Suppose the ...
Init_Eng's user avatar
-1 votes
2 answers
97 views

How can I maintain the current delivered by a power source constant if the load is variable?

Fig. 1 shows, in a simplified way, a DC power source that unfortunately can only work if the current drawn from it is constant and has a given value "I", otherwise this source will wear ...
Robert Werner's user avatar
2 votes
0 answers
95 views

Constant current feedback op-amp analysis

Above is the schematic for the convoy XHP35 flashlight driver. As you can see, the current control loop uses the op-amp as a comparator between a setpoint (low-pass filtered PWM output from a ...
roaibrain's user avatar
  • 407
1 vote
2 answers
104 views

Designing a DIY low level light therapy device (LLLT)

I am designing a low level light therapy (LLLT) device similar to the one in this video. Mine will be smaller using twenty each (for a total of 40) of two kinds of 3W LEDs: 2.4V 0.6A -- 660Nm red 1....
Bravo Foxtrot's user avatar
0 votes
3 answers
70 views

Constant current opto input circuit [closed]

I have implemented the below circuit in a small project I'm working on which is based on a suggestion in another post, Optocoupler circuit accept input between 3-50 volt It all works fine with a ...
pspeirs's user avatar
  • 75
5 votes
5 answers
1k views

How is a BJT in the active region able to vary collector current without depending on the collector and emitter resistances?

I'm currently struggling with the idea of Ic = β x Ib as applied to BJTs. I am not understanding how a relationship like this is possible without accounting for collector and emitter resistances. At a ...
Matteo B's user avatar
0 votes
1 answer
118 views

PWM LED Dimming Circuit Design Recommendations and comparison against linear dimming

I want to dim a 5 meters long LED strip reaching all across a room with a PWM signal from an Atmega328p. First the schematic and the specs: Specs: ...
CaveScientist's user avatar
0 votes
0 answers
36 views

Why is Duty cycle for CC LED driver voltage specific, when Output voltage has a compliant range?

Commercial CC drivers usually mention "x-yV output" range which means that the output voltage has a compliance range where CC operation will be maintained in constant current mode. But then ...
roaibrain's user avatar
  • 407
0 votes
2 answers
39 views

Does a current sense resistor not always mean a constant current output for dc-dc converter?

I've had a understanding that having a current sense resistor feeding into sense pins or a feedback pin meant that the inductor current was changing wrt the variations across sense resistor, hence ...
roaibrain's user avatar
  • 407
0 votes
1 answer
61 views

Constant current driver issue or misunderstanding

I want to learn how to use a constant current driver. After some research I ordered an NSI45030AT1G driver which delivers 30mA from 10V to 40V according to the datasheet. After a real testing, I am ...
SkePsis's user avatar
  • 67
8 votes
2 answers
1k views

Is an LED driver IC just a boost conv with voltage across Rsense fed into FB?

There's these really cool things called power modules, but they are all marketed as normal dc-dc converters. Not many as "led drivers" for currents more than 1 A. The basis behind this ...
roaibrain's user avatar
  • 407
0 votes
1 answer
48 views

Relay to read only pulse signal not constant signal

I am trying to find or create a relay that provides power when there is a 12v pulse signal that last less than 1-2 seconds but if it receives signal longer than 1-2 seconds then it should stop or not ...
BonezMedia's user avatar
0 votes
1 answer
394 views

What is the basic idea behind the so-called "improved Howland current source"?

I dedicate my question and answer to Gordon Deboo - the inventor in the shadow of Howland. The motive The idea for this Q&A came about yesterday after a related question was closed. Original ...
Circuit fantasist's user avatar
1 vote
2 answers
163 views

Howland circuit gain factor [closed]

I do not understand how the gain of the Howland circuit can be derived on an operational amplifier. I am attaching a photo of the circuit
niobium04's user avatar
0 votes
0 answers
32 views

Does current mode control for dc/dc conv imply a constant current output?

I am getting very confused, I have read articles about current mode and voltage mode control, and it seems that most converters use current mode control - which seems has two nested control loops. The ...
roaibrain's user avatar
  • 407
1 vote
1 answer
86 views

Rds(on) value of MOSFET constant current LED driver IC

I am testing a non-isolated APFC buck constant-current LED driver IC (model no.: BP2362XH) in my LED driver circuit. It operates in critical conduction mode (according to the datasheet). There are a ...
Sanjaya Wijewardana's user avatar
0 votes
1 answer
101 views

Understanding lead-acid battery charge

I´m trying to understand how lead-acid batteries charging work. So far what I tested: If a 14 Vdc supply is connected in a 12 Vdc battery, the voltage will drop to the battery level, and start going ...
samuel mattio's user avatar
1 vote
1 answer
52 views

0V with Electronic Load and CC Buck

Why would an electronic load show 0 V and a big current when connected to a constant current source? The load is in constant current mode. Is that the culprit? Probably a constant impedance would be ...
TobiasPSP's user avatar
1 vote
1 answer
67 views

RGB LEDs indvidual brightness control [closed]

i want to make RGB LEDs panel using https://www.lcsc.com/product-detail/Light-Emitting-Diodes-LED_TCWIN-TC5050RGBF08-3CJH-P35C_C784539.html RGB LEDs. I will put 100 LEDs in tha panel and want to ...
Zunuran Nasrullah's user avatar
1 vote
4 answers
206 views

Collector current vs. collector-emitter voltage

Why is the collector current in an NPN transistor in CE mode almost independent of the collector-emitter voltage? Doesn't increasing the reverse bias voltage (Vce) decrease the width of the base (due ...
Vinay5101's user avatar
0 votes
0 answers
59 views

How can I sum the output of the two opamps and multiply the voltage swing to +2vcc and -vcc

I have a VtoI circuit that you can see in the figure below. According to this circuit, I can receive a maximum sin current of 4 mA with a maximum load of 5 kΩ. Considering that the supply voltage for ...
raha's user avatar
  • 1
0 votes
0 answers
24 views

Can I use BP2857 constant current LED driver IC with a PWM-controlled MOSFET for dimming and turning the lights on or off with an ESP8266/Arduino?

I am trying to build a remotely controllable aquarium LED light. I live in a country where DigiKey and Mouser are not a thing. Electronic components are hard or impossible to find in this country. So ...
ISHRAQ's user avatar
  • 23
1 vote
1 answer
50 views

Connecting multiple loads in self-balancing parallel [closed]

I have three (or 'n', where n=3 at the moment) large LED panels that I want to run in parallel. As we know (or should have known before the 'royal we' actually tried it!), just wiring them together in ...
jackisquizzical's user avatar
0 votes
1 answer
93 views

I don't have constant current in this circuit

I have problem with this circuit, which purpouse is to give constant circuit on R7 resistor. Why i can't get constant circuit? Is it problem with simulator?
Византија Исток's user avatar
0 votes
1 answer
50 views

Using E3640A as current source

There is a E3640A power supply need it to function as a current source. In regular power supplies we set the maximum limit current and the regular voltage we want to output. In the manual shown in the ...
Josh23's user avatar
  • 1
0 votes
1 answer
55 views

Output voltage not changing with a constant current driver

If I attach a voltmeter to the output of this constant current driver and lower or raise the input voltage (100-230V,) the output voltage remains constant at 56V. Should it not fluctuate between 40-...
Guit4eva's user avatar
  • 115
1 vote
2 answers
85 views

Alternative method of high power constant current drive for LEDs

The only high power, constant current method I am aware of involves using a MOS switch in conjunction with an inductor to alternately power and disconnect the LED, achieving an average current flow. ...
Antron Mack's user avatar
0 votes
2 answers
290 views

How to understand current limiter circuit

Here the MOSFET IRF9530 works in linear mode of operation and transistor works in forward active. Load resistance is 5 Ω and up to 15 Ω I can keep this MOSFET is linear mode and on increasing further ...
Praveen Kumar's user avatar
1 vote
1 answer
63 views

Boost Current and Limit Voltage

I have a radar gun which has a serial interface. The gun reports the velocity out to the serial port. I want to attach a microcontroller (ESP8266/ESP32) to the serial interface and forward the ...
namarino41's user avatar
1 vote
1 answer
40 views

Using VOUT to Power Up a DC-DC Switching Regulator

I am trying to use LM5117 to convert 36V (VIN) to 32V (VOUT) for constant current constant voltage application. It seems the datasheet is saying if the VIN > 14.5V I can use VOUT with a Zener diode ...
nmr's user avatar
  • 133
0 votes
1 answer
128 views

Building a constant current circuit [closed]

The constant current output should be able to be set from 0.2 mA to 20 mA with a load of 3500 ohms ±50% from a 5V battery source and a PWM signal set by a microprocessor. Do I need a transformer or ...
Marc's user avatar
  • 1
0 votes
1 answer
126 views

Need cheap variable positive/negative switching bench power supply with CC

Just for fun I want to make a lightweight, cheap, adjustable positive/negative bench power supply. "Lightweight" means that using an old PC ATX power supply isn't suitable as a basis. ...
Mike S's user avatar
  • 153
3 votes
1 answer
192 views

Simplest voltage-controlled constant current source outputting 500 mA

I'm trying to design a very simple, beginner-friendly voltage controlled current source that will output 0.5 A through a load resistor. The load (some current-activated nitinol wire) will be about 10 ...
Bee's user avatar
  • 597
0 votes
0 answers
50 views

Calculating JFET stats for a constant current source [duplicate]

I need to find a constant current source for a variable LM317 current regulator (schematic below), and I would like to know which JFETs to use. Can somebody let me know how much current I need and ...
Klumpy7's user avatar
  • 392
2 votes
1 answer
451 views

Airport runway lighting: What is constant current in relation to alternating and direct current?

I’m an apprentice electrician currently replacing runway lights and pulling new wire at a small international airport. When I asked I was told they are 5kV direct current. Okay… simple enough. What ...
Incompetent Jim 's user avatar
0 votes
1 answer
117 views

Instructables DIY current limiter circuit [duplicate]

I found this inline and was hoping if that circuit is okay. Instead of a battery though, I want to use a dynamo (plenty of juice-wise). Output of dynamo is 18 V 200 mA. I wish I could adjust the ...
imran muhd's user avatar
0 votes
0 answers
42 views

1S Li-Ion BMS Design

I want to use AP6633 Protection IC along with MCP73833 Charging IC for 1S Lithium-Ion Battery. The issue is pinout of AP6633. I really dont have any idea how to connect AP6633 Pins to MCP73833, More ...
Zunuran Nasrullah's user avatar
1 vote
1 answer
129 views

Isolate current flow in Ltspice using switch

I am trying to control the flow of current by the switch SW, I have used an independent current source I. However the switch is ineffective to isolate the resistor R1, because the switch is basically ...
Avijit Das's user avatar
0 votes
4 answers
194 views

How will two parallel LEDs behave on a constant current source?

Another user made the following claim: You cannot [LEDs] in parallel and expect the current to magically divide in half. Of course, this is exactly what someone just starting in EE would expect to ...
Matthew's user avatar
  • 572
0 votes
2 answers
133 views

How to wire mixed-count groups of LEDs?

I have a bunch of LEDs (all the same part number / specification) that I want to light up using a shift register. The trouble is, each output bit should control a different number of LEDs (depending ...
Matthew's user avatar
  • 572
1 vote
0 answers
131 views

Constant current LED driver temperature issue

I am using a DC-DC step-down constant current LED driver to power up four high power LEDs in a series connection. The LEDs are drawing a 2 A current at 100% power and they have forward voltage about ...
Lime7's user avatar
  • 33
0 votes
1 answer
130 views

Buck converter not behaving as anticipated with new trim pot resistors

I recently purchased a 300W buck converter from amazon 1 which has two 3296W 100K trim pots to control the constant current and constant voltage output. My plan was to use them as bench power supply ...
Prashant's user avatar
  • 131
12 votes
5 answers
4k views

Is it recommended to set the current limit on a bench power supply by shorting it?

I have a Rapid 85-1901 switching mode 0-20V 0-5A bench power supply: Without a load attached the current shows 0A no matter how you turn the dial. After searching how to set the current limit online, ...
Danny Beckett's user avatar

1
2 3 4 5
14