25
votes
Accepted
Will this circuit work ? 100 Leds project
No, that's a really bad circuit. You have 100 LEDs, all in parallel. Bad idea.
Since this is a assignment, I'm not going to give you a better circuit outright. However, consider that LEDs want to ...
- 314k
25
votes
Accepted
Why do most flyback converters / LED drivers operate under 100 kHz?
There are many reasons:
- Cost: This is probably the biggest reason. The lighting market is quite competitive. There are lots of Chinese players offering aggressively cheap prices. This forces the ...
- 38.1k
20
votes
LED current driver
Lose the series resistors. It's not clear what you think they do for you, but they won't do anything useful. You have the LEDs connected to constant current drivers. Series resistors only get in ...
- 314k
19
votes
LM2586 - Inductor Heats Then Burns
I'd suggest your B340A diode is avalanching since you are far exceeding its reverse voltage rating.
The diode must standoff the voltage you generate, so you need a voltage rating above your capacitor ...
- 21.9k
19
votes
Accepted
Can I send PWM through 1 meter cable?
The PWM frequency is not so important, what matters is the rise times of the switch controlling the PWM. Assuming it is some sort of MOSFET, one can assume very fast rise times of 100ns to 10ns or ...
- 29.1k
17
votes
Accepted
Full Spectrum LED(400nm~840nm) vs Grow Light LED (RED+BLUE)
None of the above.
All you want is Deep Red (650nm) and Deep (Royal) Blue (450nm).
You do NOT want Full Spectrum, UV, IR, Far Red, Only White or anything besides Deep Red and Deep Blue. Red White ...
- 7,467
16
votes
Parallel resistor in series with LEDs
Because doubling the current paths halves the power dissipation in each path, allowing use of cheaper resistors.
- 48.6k
15
votes
The mysterious case of the random leakage current
Here is the summary of my investigations and my findings on the mysterious case of the random leakage current.
When I began dismantling the units, I also got curious and wanted to research a rational ...
15
votes
Accepted
The mysterious case of the random leakage current
I suspect something to do with the strong magnet (I wouldn't have suspected it, except that it must be an interesting answer or you wouldn't have posed the question). Perhaps having the magnetic ...
- 5,984
15
votes
Accepted
How to drive 700mA LED cheaply?
XY problem.
Your best efficiency solution from a power and cost point of view to drive a 1A LED load is to use a LED driver IC. There are many to choose from; the Diodes Inc PAM2804 seems likely to ...
- 56k
14
votes
How can I efficiently drive an LED?
Here is a collection of Linear LED driver options you can play with.
simulate this circuit – Schematic created using CircuitLab
- 1,037
14
votes
Why did my LED drivers blow up?
IC Datasheet:
"EP Exposed pad/TAB connects to GND and thermal mass for enhanced thermal impedance."
It doesn't say that omitting this will certainly damage the device, but in general, EP's ...
- 16.3k
13
votes
Accepted
LM2586 - Inductor Heats Then Burns
I believe you are exceeding the peak inverse voltage (PRV) rating of D4, the 40 V Schottky diode. During your switching cycle when the SW pin on the 2586 goes to 0 V, D4 becomes reverse ...
- 1,769
12
votes
Why do LEDs require a constant current source and not a constant voltage source as power supplies?
Oh, you can drive an LED with a constant voltage. It's only that this voltage has to be in a very narrow band, depends on chip temperature, and is difficult to regulate.
Look at the I/U chart of a ...
- 14.4k
11
votes
How to reduce LED flash rate (frequency)
The fact that there's multiple operating modes indicates that HH5K1 is not in fact a simple device, but most probably a cheap microcontroller¹ or dedicated ASIC that does the blinking.
I'm afraid ...
- 98.3k
11
votes
Why did my LED drivers blow up?
In addition to the answer from @rdtsc, your trace leads are far too narrow, and that, in turn, leads me to suspect your PCB layout.
You don't say what current you're running. You should analyze the ...
- 46.7k
11
votes
Is an LED driver IC just a boost conv with voltage across Rsense fed into FB?
No they're not just a marketing thing. The market for LED drivers for illumination, LCD backlights and such like is enormous so the chips are optimized for the purpose. Both buck and boost are made. ...
10
votes
Accepted
How can a DC18V ~ 36V LED driver work with DC3.6V LEDs without burning them out?
Your driver will output a fixed current through a string of LEDs.
Since your LEDs are rated at 700mA @ 3.6V, this driver will indeed supply adequate current for the LEDs without burning them out.
...
- 46.9k
10
votes
Parallel resistor in series with LEDs
You mean instead of single resistor?
It depends on the use case.
Assume a power of 600 mW has to be dissipated across the resistor. Instead of choosing one single resistor of standard wattage, say 1 ...
- 9,331
10
votes
Accepted
Do output LEDs here need resistors?
As always, READ THE DATASHEET!
The chip you use has programmable constant current outputs, so you don't need external resistors to determine the current, the chip does this for you.
The current sunk ...
- 48.8k
10
votes
How to drive 700mA LED cheaply?
I read about a method of limiting current using 2 transistors (schematic attached below).
All linear solutions, resistor or whatever, will have the same efficiency.
If you run the LED at 1A, it will ...
- 80.3k
10
votes
Accepted
Understanding the characteristics of a LED driver
This is a constant-current output off-line switching power supply. In normal operation the output voltage is limited by the LEDs to between 10 and 21VDC. You should not connect it to an LED array with ...
10
votes
Will a current mirror prevent thermal runaway of these LEDs in parallel
A current mirror can only servo the output current if it has the voltage headroom (compliance) to do so.
If D2 is lower voltage drop and tries to hog the current, then Q2 will reduce its current by ...
- 171k
10
votes
Accepted
Best way to drive multiple LED strips at distinct times with one LED driver
Your boost LED driver circuit has high side current sensing, its output is ground referenced, so you can switch your LEDs with low side MOSFETs, which is convenient.
All you have to do is duplicate Q2 ...
- 80.3k
9
votes
DIY LED lamp is less powerful than expected
Your connecting wires are too thin, you are dropping voltage in your leads.
You need to select the right size of wire and potentially use a star connection to drive the strings.
If your strip is ...
- 21.9k
9
votes
Accepted
Is my LED driver fundamentally incorrect, or can I compensate it somehow?
That is a pretty weird way of "driving" LEDs.
OP's schematic:
A few issues:
essentially you have an "equivalent" resistor, shared by the LEDs (if the LEDs have any imbalance - ...
- 7,974
9
votes
Accepted
RGB digital to analog converter
WS2812 protocol is based on different high/low times to encode bits, it's non standard, and pretty fast (~1-2µs/bit).
You could use a microcontroller but it will have to run code in a tight loop to ...
- 80.3k
8
votes
What does voltage range mean in this LED driver?
LEDs work best if you drive them with a current.
When you would apply a voltage to a LED or a string of LEDs in series, the current can vary a lot over production lots and temperature. It is very ...
- 81.1k
8
votes
Making an efficient constant current source
I suspect you're overthinking your problem. Maybe not, but probably.
There are two questions you need to ask:
1) How stable is your 24 volt supply?
2) How precisely do you need to control your LED ...
- 60.8k
8
votes
MOSFET Heating in LED Driver Circuit
There is no way for your MOSFET to turn off.
Figure 1. Move R39.
The problem is that when the opto turns on Q1's gate capacitance is charged up. When the opto turns off there is no discharge path. ...
- 178k
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