I have these LEDs located in different rooms, and these the parameters:

Led 1: 6.4V - 7.2V @ 0.7A

Led 2: 2.9V - 5.6V @ 1.9A

Led 3: 8V - 12V @ 3.4A

Led 4: 50V - 56V @ 2.8A

I have a computer PSU that outputs 12v, 18A.

If I connect in parallel these drivers/bucks to the exit of the PSU, will it work or do i risk to burn them?

LED 1: this

LED 2: this

LED 3: this

LED 4: this

They are generic LED beads only.

 

You will burn them without current control
LED's are current regulated devices. Not voltage regulated.
U need appropriate current limiting resistors(Devices) for each LED

So the idea of using LED drivers is essential.
You can connect all the buck inputs to a common DC 12V if the buck can take 12VDC input

 

Thanks for your answer, but the driver I want to use, for example for the first Led has this specs:

• Input DC 5-35V
• Output: 700mA ± 20mA
• Drive 1-10 pcs 3W LED
• Supports PWM dimming
• High level turn off the output
• Low level Open the output
• LED buck mode to ensure the total total voltage difference is lower than the input supply voltage (2-3V)
• Constant output current, low ripple
• LED used to ensure the safety, stability, improving the LED light efficiency, reducing the lumen
• Overload, short circuit, overcurrent protection, to ensure the supply security.
• Wide input voltage, VIN + is positive electrode input, VIN-negative electrode power supply input.

This means that if I have a 12V dc from the PSU, the output of the driver should be less then 12V (ex. 9V), at 700mA. Right?

 

The first one is absolutely fine, it's intended for that purpose.

The second one does not appear to have a current limited output, so would not be appropriate.

The third seems to have a current limiting setting, so again, should work

The fourth implies that it might current limit, but it's not sure.

With high power LEDs, it will be important to heat sink, so be sure you take care of that.

Is there any reason why you would use 4 different types of LED? It would be easier to maintain if you just had one kind.

 

The 4th has a current adjust multi-turn trimmer, so it looks ok also. #2 is the only one that might be a problem,

NOTE - many LED array devices have current regulation built in, and are designed to run off of standard constant-voltage power supplies. If this is true for LED #2, you should be ok.

ak