Driver for laser diode

Projects General Guidance
1

Hi dears.

I own 850nm laser diode.

Wavelength: 850nm (±5nm)
Output power: 2.3W
Threshold current: 0.2A
Operating current: 2.5A-3.6A
Operating voltage: 1.7V-2.2V

I have a question about laser diode driver.

  1. Is this something complicated? - i mean is signal should have some PWM or something to power laser?
  2. Why laser driver called constant current, if voltage should be adjested too? for example,
    i found laser driver
    image
    image800×800 31.5 KB

    which called 650nm 780nm 808nm 850nm 980nm Red IR Laser Diode Module Driver
    all of this wavelengths have diodes with different required voltage, 650nm - 2.4~3V, 850nm - 1.7~2.2V. How i can use this one for both of them, if this module allow adjust only current.
  3. Why i can't use regular DC-DC CC CV step down converter? - price for XL4015 module is around 1$, while price for laser driver with 2A output current is around 10$. WIth XL4015 module i can adjust current & voltage to match exact required values.

Thank you for your help and time.

2

Please post links to the datasheets for both the diode and the driver.

3

How do you adjust the current?

4

A constant current driver will automatically adjust the voltage so that the set current is reached.

5

This is laser diode datasheet: 2 3wto56diodelaser-ds-cl-ae - 2.3 W 8xx nm Pulsed TO-56 Packaged Diode Laser (en) -
This is drivers:
One
Two

6

This is regular step down dc dc with current and voltage adjust potentiometers

7

Constant current is safe, voltage does not vary much with current, meaning constant LED power.

Constant voltage is unsafe because the LED current can vary much over temperature change.

8

How driver will know that me laserdiode needs 1.7v if i can adjust only maximum current?

9

A laser diode does not "need" voltage, it needs current and the forward voltage results from that current.

10

It measures the current then automatically adjusts the voltage so that the current is constant.

11

You could try using the buck converter but more that likely you will burn out the laser while making the adjustments.

12

The lazer diode emits invisible light. At full power it will damage eyes.
What is the project intended to do?

The driver links are not accepted due to demands for cookies...

13

Try this please 1, 2
I want bild some kind of range measurement device, i have laser photodiode which can be used with that laser diode, and IR with that power is choosen, cause i want to do it event at day time.

If i will adjust current and voltage to 1.7v max, and 2A max, before i connect laser, why it will burn laser diode?

So in result regular laser diode driver, gives lets say 1A of current, and for laser diode no matter how much voltage it takes? then why in datasheets we see max voltage value?

Also i see 2 types of hight power drivers, lower than 450nm and higher that 800nm, they looks similar, but price is 2x for 800+, is they have some difference?

Why i can't take LM317 for example and do like in this video? https://www.youtube.com/watch?v=2Rjlf7gnXms

14

The data sheet says the the typical operating voltage is 1.7V and the maximum operating voltage is 2.2V, they do not specify a minimum.

What that means is that if you buy 1000 lasers and measure the operation voltage, the average value will be 1.7V but none of them will be more than 2.2V.
Some will be less than 1.7V but since a minimum isn't specified we just don't know what it could be but it probably won't be less than 1.2V.
So when you buy the laser, the working voltage will be somewhere between 1.2V and 2.2V.
So if you did set the voltage on you DC-DC to 1.7V and the operating voltage is really 1.62V, then you just burned out your first laser.

LASERs almost work the same way LEDs do. If you understand how an LED works then you basically know how a LASER works, with some exceptions

15

I thought that 1.7-2.2V is a range in which laser diode can work

How then drivers know which voltage is required for laser diode?

16

You (user) must know and supply enough voltage to the driver.

17

Here, input voltage is 7.5-12V, its much more than 2.2V, but descriptions says that its for 850nm. Also there is 2 potentiometers, i believe thay are for current and voltage based on desciption, how i can know exact required voltage? based on @jim-p latest comment?

18

How then drivers know which voltage is required for laser diode?

They don't know and they don't need to know.

In simple terms, the driver sets the voltage to 0V and it measure the current through the laser. Then it slowly raises the voltage until the current through the laser matches the current you set with the little trim pot. It will constantly measure the current and adjust the voltage in order to keep the current constant.

If you measure the voltage across the laser with a voltmeter , you will find that it will be at the operating voltage for that specified current.

19

Exakt voltage is not required to know. You can adjust the driver to the maximum allowed voltage of the diode. Or even more, if you like.

Your PSU sets the output voltage not higher than you set it, and the current not higher than you set it. The rest depends on the load. Easy to calculate for a resistor (Ohm's law), a bit more complicated for a non-linear diode.

20

So, driver will adjust voltage and current and voltage can be lower than i set it? but driver will adjust everything untill it reach current that i set? right?

What is the difference then between this and this
Second one has 1A more power, but cost 2x less

And why on video where used LM317 laser not burned out, cause of not adjusted voltage?