THORLABS DC4104, Руководство по эксплуатации

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DC4104
Compliance Voltage
Compliance voltage is typical parameter of a current source. A ideal (theoretical) current source
has an infinite source impedance, so it can deliver the current into any load. In the real life, an
infinite source impedance is impossible.
A real current source is based on a voltage source followed by a current control circuit. The out-
put current creates a voltage across the connected load. As soon as this voltage is getting
close to the voltage, delivered by the internal voltage source, the current control circuit be-
comes unable to control the current anymore - the current drops.
The "Compliance Voltage" is that max. voltage across the load, at which the current driver
device can still deliver the max. current.
The DC41xx series has a compliance voltage of 5V, that means, that the voltage across the
LED at max. current (1A) must not exceed 5V. Depending on the type (wavelength, max.
power) an LED can have a "forward voltage" from 1.5 up to > 7 volts. When selecting an LED
and a driver, please make sure that the compliance voltage of the driver is not lower than the
LED forward voltage.
LED Forward Voltage
The graphics shows a typical IV characteristic (cur-
rent I vs. voltage V) of a white LED.
Up to certain threshold forward voltage the current
is close to zero. As soon as the threshold is
reached, the current increases non-linearly.
A suitable driver for such an LED should have a
compliance voltage ≥ 4.0V in order to ensure, that
the max. current can be delivered into this LED.