13
Cooling
The maximum thermal dissipation of the LDP-QCW depends on the configured pulse length,
repetition rate and capacitor bank voltage. The driver is cooled by a heat sink and two fans for
continuous high-power operation. The maximal thermal dissipation can be estimated by:
S
LD
LD
LD
cap
L
P
d
I
d
I
V
V
P
1
.
0
)
)
((
where
L
P
Thermal dissipation loss in W
cap
V
Capacitor voltage in V
LD
V
Compliance voltage of the LD in V
d
Duty cycle in percent
LD
I
Laser diode current
S
P
Static operation losses ~ 7 W
This is only an approximation and achieved values can differ. Carefully monitor the
temperature of the driver and the heat sink for new operational conditions.
Test Load
A common method to test the driver is to connect a regular silicon rectifier diode to the driver
output. Please pay attention to the junction capacitance of the diode. Only fast recovery
diodes (or similar) have a low parasitic capacitance comparable to laser diodes. To achieve
reasonable test results, the parasitic elements of the test diode and the connection must be
very similar to a laser diode approach. Regular silicon rectifier diodes have a junction
capacitance of several microfarads and are not a suitable test load! The use of these diodes
will yield in incorrect current measurement at the pulse edges!
It is also possible to test the driver using a shortcut. This will not damage it, but result in an
incorrect measurement for the rise and fall time of the current pulse.
