PICOLAS LDP-V 03-100 V4.0, User Manual

Page: 9 / 12

9
Internal Structure of the LDP-V
The LDP-V series generates the pulses by a simple but efficient principle. First, the
storage capacitors (C
S
) are charged, whether through the internal HV-DC supply or an
external high voltage source. When a pulse is applied at the trigger input, the high speed
mosfet opens and the current flows from the capacitor through the laser diode, mosfet and
current sense resistors. At the end of the pulse the mosfet closes again and the current
stops. The generated current depends on the applied high voltage, the laser diode
compliance voltage and its differential resistance.
The following formula gives a good estimation of the laser diode current depending on the
pulser’s high voltage supply U
HV
, the laser diode compliance voltage U
comp
and its
differential resistance R
diff
:
diff
comp HV
LD
R
U U
I
+
−
≈
6 . 23
The laser diode current is measured with current sensing resistors (current monitor output)
and with the galvanically isolated Rogowski coil. The trigger input provides full control of
the driver’s pulsing capability to the user. The required DC high voltage can either be
applied through an external voltage source or it can be generated with the integrated HV-
DC supply. The internal supply is controlled by the HV setpoint poti. A voltage monitor
(pin 8) provides feedback of the high DC voltage.
The Diode D
RP
prevents the laser diode from reverse currents; a 10kR NTC provides the
possibility to monitor the pulser temperature. An overtemperature protection is NOT
integrated on the driver.
Rogowski-Coil
Rogowski-Coil
Current-Monitor
Trigger SMC
Pin 2: + HV
Pin 4: +15 V
Pin 9: NTC
Pin 6: Trigger
Pin 1,3: GND
15 V
18 .. 90 V
50 R
10K
+HV-Adjust-Poti
Driver
++++
- - - -
LD
Pin 5: Disable Poti
Pin 10: Ext. HV setpoint
Pin 7: Disable
Pin 8: U-Monitor
R
CS
C
S
R
CL
D
RP
50 R