Laser diode drivers are current sources and can drive inductors. But, the driver may need to output a much higher voltage than expected if you want fast rise times.

Here's the formula to determine the voltage:

V = (L • di/dt) + (R • I)

The first term, (L • di/dt), calculates the voltage needed to force the given current through the inductor in the time allowed. The units are henrys (L) and amperes per second (di/dt).

The second term, (R • I), gives us the additional voltage needed to accommodate the drop across the inductor's DC resistance, cabling, connectors, etc.

For example, assume the inductor is 1 μH and the DC circuit resistance is 0.2 ohms. If we want 300 A to flow in 1 μs, then it takes:

V = (1 • 10^{-6}) (3 • 10^{2})
/ (1 • 10^{-6}) + (2 • 10^{-1}) (3 • 10^{2})
= 360 V

to do the job.

Updated:
19 Feb 2019 12:42 AM

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