Current Limiting Circuit

An electronic card is designed that limits the current delivered by the adjustable current source (laser driver) for 2 reasons.

1.- Limit laser optical power to 300 mW corresponding to class 3B according to ANSI Z136.1 international standard. "Safe Use Of Lasers", such that the risks of manipulation with lasers of higher optical power are reduced.

2.- Avoid damaging lasers whose maximum operating current is less than that delivered by the adjustable current source (laser driver).

The topology used is the following:

• Vin corresponds to pin + of the LD output that powers the laser from the adjustable current source (laser driver)
• Iout connects to the laser cathode
• The ground of the laser driver (pin - LD) connects directly to the laser anode
• R1 is calculated according to the current to be limited.