14
VCap
VCap
VCap
VCap
The VCap value defines the voltage of the capacitor bank (see chapter functional description). This
value is a bit tricky to determine as it depends on the chosen pulse width, repetition rate and
compliance voltage.
If his value is too low the current will drop during the pulse or not even reach the set point, if it is too
high the output stage will heat up fast and lead to an over temperature shutdown.
The following equation can be used to calculate the capacitor voltage in dependence of the output
current, compliance voltage and pulse width:
))
112
.
0
011
.
0
(
(
5
pulse
LD
LD
cap
T
I
U
V
+
+
+
=
where
LD
U
= compliance voltage
LD
I
= current setpoint
pulse
T
= pulse width
This equation does not use the repetition rate. Hence this value must be increased if a current drop is
measured during operation.
For first tests or low pulse width and repetition rate it can safely be set to maximum, but the higher
this value the greater the power losses are in the output stage.
LED codes
The LDP-QCW is equipped with a red and a green status LED.
The red LED is connected to the Pulser_ok pin of the BOB connector and will lit if the signal goes low.
The green LED the following codes:
Permanent on: The LDP-QCW operates normally and the current output is enabled
Blink 1x:
Master Enable is given, but Enable not
Blink 2x:
Master Enable is not given
