Laser Diode Driver


The LDRV-VC is a current driver and temperature controller for 14 pins butterfly mount diode lasers. The laser current is proportional to the sum of three voltage signals: one build-in reference, one low frequency input and one high frequency input. (LDRV-RF module also provide a >100Mhz RF signal injection port). This allows flexible light modulation for a wide range of applications.

The laser and its fiber are installed inside the instrument so there will be no external wiring. All parameters can be accessed through USB2.0 port.. 


Product model



Name Model Price
Laser Diode Driver   [PDF]  [RFQ]

LDRV-VC
Stock NO.: B80020085
USD 1200.00 
 


Parameter



Specifications

Item #

Min

Max

Unit

Comments

Power supply

100

230

VAC

50/60Hz

Power

5

20

Watts


LD current

0

128/

266/

590

mA

Selected   through jumpers on PCB

Compliance Voltage

0

3.1

V


Frequency response

0

20

MHz

-3db

Temperature control range

0

50

oC


Supported Temperature Sensors

10K   NTC Thermistors


TEC output current

-1.5

1.5

A


TEC output voltage

-4.4

+4.4

V


Analog input (low freq)

-2.5

2.5

V

500 ohms termination.

Analog input (high freq)

-2.5

2.5

V

50   ohms termination. Capacitor coupled. 10Khz high pass.

Photocurrent Measurement Ranges

0

2.0

mA



Panel

dr1.jpg

①Power switch;②Power indicator;③Laser indicator;④Low freq input;⑤High freq input;

⑥Key switch;⑦Fiber/wire channel;⑧Light out (FC/APC fiber adaptor)


Installation

Remove 6 screws at the side and open the upper cover. The mounting board is seen as below:

First, remove the M2.5 screw at the mounting position. Open the (10) pin connector. Install the LD with fiber pigtail pointing upwards. Make sure all pins are clamped by the connectors. Use M2.5 screws to fix the LD.

Carefully arrange the fiber. Make multiple turns above the mounting board. Use the (13) screws holes to gently fix the fiber if necessary. Finally connect the terminal to (8) adaptor, or outside the instrument through (7).

dr2.png

⑨Mounting position;⑩Pin connector;⑪Wire connector;⑫Screws(insulation); ⑬Screw holes for fiber fix; 

6093dd4b25157.jpgRefer to the pin definition of the laser diode, and definition of (11) wire connector. Make sure the connection is compatible。Remove the mounting board to adjust the connection on the PCB if necessary. Pay special attention when one or more pins on the LD is connected to its shield. If not sure, insulate the LD shield from any other parts of the instrument. 

6093dd4b25157.jpgStarting the LD under incorrect pin connection may damage LD and instrument. 


Setup

Make neccessay setup on the PCB to match the specifications of LD. Remove the mouting board first. Please operate when the instrument is disconnected from the power supply. 


Current

Set the max driving current to be equal or slightly larger than the desired working point of LD. Large current setting will increase the risk of damaging LD. Setting is done through P15 and P16 jumpers. Their location on PCB is shown as below. 


6093dd4b25157.jpgP15 and P16 jumpers MUST be set consistently. That is both left, both right or both open. 

dr4.png

dr5.png

TEC

TEC current, voltage and PID constants can be set through the switchs on PCB. Their locations are shown as below.

dr6.png

⑭PID constants;⑮Max TEC current;⑯Max TEC voltage

Refer to the specifications of LD. Both current and voltage should be lower than the absolute max rating of LD. 

The PID control time constant is initially set to the shortest value, which is suitable for many low current laser diode. If temperaure oscillation is observed, time constant shall increase. This can be done by decreasing KP (propotional constant) and KI (integral constant). Please change the switches when the instrument is shutdown. 

dr7.png

dr8.png

Changing wires

The functions of wires are marked on the PCB. Checking the wiring with the pin definition of LD. Notices that only NTC- is connect to the system ground and none of the other pins are connected. They will not work properly if connected to ground /VCC or with each other.

NTC- can be used for grounding. It will provide more stability in some cases. If anode of LD is connected with the laser shield. Please insulate the shield from the mounting board.

dr9.jpg


Usage

software

Install the controller software (LD-PD) on PC. Restore the mounting board, upper cover. Connect the instrument to power supply. Connect the USB wire to the PC. 

Turn on the instrument. The (2) power indicator shall turn green. The PC may prompt for new hardware installation. In most cases, the installation can be done automatically. If not, download the driver from the following website and install: http://www.ftdichip.com/Drivers/VCP.htm 

6.jpg


Open the LD-PD software. A virtual COM port appears in the lists. (if not, click the “Refresh” button). If there are multiple COM ports on the computer, you should select the right port in the list. Click the “Connect” button. The instrument model and bios version will appear at the up-right corner.

Input the desired LD working temperature at the “LD Temp Setpoint” input box. Click “Set temperature” to send the value. Set the constant current and protection limits with the sliders. Click “Set Parameters” button to make changes. Click “Save All settings” to store these values to the instrument. The saved values will be automatically loaded at next time.

Start the laser with “Run: DC” button. The laser indicator on the panel will turn red. 

6093dd4b25157.jpgCheck all parameters in the permitted range of LD.


Modulation input

Use (4) and (5) ports for the external signal modulation. The equivalent input circuit are shown as below: 

dr11.png

The current on LD is calculated as follow:

dr12.png

The max modulation frequency is 20MHz. 

6093dd4b25157.jpgWhen the driver is in IDLE state, the protection circuit will clamp the LD current to a very low level. Thus the modulation input will no work. This will protect the LD from unwanted inputs signals. When the driver is in RUN state, the saved limits take effect.


Manual operation

When all parameters are previously set through software (“save” button clicked), the instrument can run without a PC.

Press the (6) Run/Stop button for 1 seconds will start the laser. All saved parameters (temperature, constant current, protection limits) will be loaded. Press the button again to stop.


USB communication

The instrument communicates with PC through USB wire, in a virtual COM port manner. User can control the instrument using their own software. 

The chip used for virtual COM is FT232R. Drivers can be found from the manufacture: http://www.ftdichip.com/Drivers/VCP.htm . Default settings: baud rate 115200bps, 1 stop bit, no parity check. Communications are in ASCII mode. 

dr14.png

dr15.png

Commands from the host (PC) shall start with a colon “:”, end with \r\n

Commands as follow: (End of line(\r\n) are omitted)

Send

Return

Function

:auto on

(1)Auto run started.[[OK]]\r\n

go   into RUN state

:auto off

(0)Auto run stopped.[[OK]]\r\n

go into IDLE state

:about

(%f)   TEC.\r\n

(%d,%d,%d)   PGA,freq,amp.\r\n

(%d,%d,%d)   bias.\r\n

(%d,%d)   dm,phase.\r\n

return   the current parameters.

:version

RYMLASER\r\n

return the version

:tec x

(%.2f)TEC   temperature set to %.2f.[[OK]]\r\n

set   the target laser temperature

:tecslow

(1)TEC Slow Mode.[[OK]]\r\n

TEC slow response mode.

Integral constant divided by eight.   KI/8

:tecfast

(0)TEC   Fast Mode.[[OK]]\r\n

TEC   fast response mode.

:tecp   KP,KI,KD

(%d,%d,%d)tecp(K,I,D) set to   %d,%d,%d.[[OK]]\r\n

set the temperature control PID   constants.

Only work when all three PID switches   on PCB are ON.

:temp

%.1f,%.1f,%d\r\n

return   ambient temperature, laser temperature and photocurrent reading.

:pdc

%d \r\n

photocurrent reading.

:bias a,b,c

(%d,%d,%d)Bias set to %d to %d,   increment %d/256.[[OK]]\r\n

set current (a) and limit (b).

a = (Iset/Imax)*65536

b = (Iprotect/Imax)*65536

c = 1

:save

(1)Parameters   saved.[[OK]]\r\n

save   the current parameters into the build-in RAM



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