Do you have some recommendations about MOSFET?

[ailee]

I hope you can help me out: I'm going to use 12V supply to power an Arduino. I need to switch several high power laser diodes (2 V, 3.5 A) on and off and I have to be able to modulate the power from the laser diodes. If I want to control the MOSFET with PWM, can I still use that driver and MOSFET to control de current in the diode? If not, what driver and MOSFET do you recommend? I assume I will use 12 V to power the driver and the MOSFET gate, but I need 2 V for the laser diodes.

[Vivek Garg]

Hi,

Yes, you may regulate the current in the laser diodes using a MOSFET and PWM. The following strategy is suggested to do this:

1. Choose an appropriate MOSFET: The MOSFET you choose must be able to manage the current your laser diodes demand. A MOSFET with a low on-resistance (RDS(on)) and a high current rating is what you want to find. Make sure it is capable of handling 3.5 A or less continually.

2. Use a gate driver: Given that the Arduino's PWM output voltage is 5V, a gate driver might be necessary to provide the MOSFET with enough power and current to turn it on completely. Select a gate driver with a logic-level input (compatible with 5V) and 12V input capability.

3. Circuit connection Connect the PWM pin on the Arduino to the input of the gate driver. Connect the gate pin of the MOSFET to the output of the gate driver. Connect the 12V supply's ground to the MOSFET's source pin. Connect the common cathode of the laser diodes to the drain pin of the MOSFET. The anode of the laser diodes should then be connected to a 2V power source, with the other end going to the drain pin of a MOSFET.

4. Control the current: The duty cycle of the PWM signal from the Arduino may be changed to regulate the current flowing through the laser diodes. The duty cycle shows how frequently the PWM signal is strong in relation to the entire period. You may regulate the average current passing through the laser diodes by adjusting the duty cycle.

5. Current-limiting resistor: You might need to connect a current-limiting resistor in series with the laser diodes in order to limit the current to the required value. Using Ohm's Law, R = V/I, where V is the voltage across the resistor (12V - 2V = 10V) and I is the required current (3.5A), it is possible to determine the resistor's value. Please be aware that a resistor's power dissipation can be fairly considerable, so pick a resistor with a suitable power rating.

By adjusting the PWM duty cycle with this source, you can control the current through the laser diodes while the MOSFET acts as a switch to turn them on and off. Examine the datasheets of the components you select to make sure they are compliant with your requirements and have detailed specs.

 

Have a nice day!