Opt Lasers LPLDD-1A-16V-3CH User manual
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LPLDD-1A-16V-3CH
Operating Manual
Table of content
Product description ............................................................................................................................1
Technical data.....................................................................................................................................2
Connection and pinout .......................................................................................................................3
How to power supply LPLDD 1A 16V 3CH............................................................................................4
Measuring the current........................................................................................................................4
Adjusting the maximum current..........................................................................................................5
Current control...................................................................................................................................6
Protection...........................................................................................................................................7
Product description
LPLDD-1A-16V-3CH Laser Diode Driver is a low current version of a 3 channel RGB lite LPLDD laser
diode driver. The maximum output current is 1 A per channel. It was designed for lower power laser
diodes in order to assure smooth waveforms, fast-rising/falling time and low ripple.
This is the professional three-channel medium-power driver for laser diodes (e.g. RGB laser systems)
with a built-in soft-start feature. The current of each channel can be independently controlled via the
analog input of 0 - 5 V with a modulation bandwidth of up to 100 kHz. Each channel has
a potentiometer that can be used to set the maximum current.
Each of the controls is labeled on the PCB to make it more intuitive and easier to set.
The proper connector is attached to the driver for your use.
This laser controller is provided without a heat sink to allow customers to use their own heatsink. It
also reduces the price for those customers who wish to operate it at a low current where a heat sink
is not required. It is a fully functioning component ready to be mounted in laser devices.
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Technical data
Dimensions
55 x 23,5 mm
Input Voltage
7 - 16 V
Max. Current per Channel
1 A
Max. Modulation Frequency
100 kHz
Max. Power Dissipation
15W
Modulation Input Voltage Range
0 - 5 V
Number Of Channels
3
Pre-Set Current Setting
0 mA
Softstart Time
100 ms
Transistor Type Used
N-MOSFET
Rise Time
less than 1.5µs
Fall Time
less than 1.5µs
Noise and Ripple (RMS)
4.2 mA
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Connection and pinout
Inputs:
Pin No.
Label
Description
1, 2
Vcc 7-16V
Power supply (7-16V) input
3, 4
GND
GND of power supply
5
B
Control analog input (0-5V) for “blue” channel diode
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G
Control analog input (0-5V) for “green” channel diode
7
R
Control analog input (0-5V) for “red” channel diode
8
GND
GND of control analog input
Labels on the board showing "R", "G", "B" channels are only the suggestion of how to connect the
diodes. It is possible to use any channel to any laser diode.
Outputs:
Name
Description
BLUE+
“Blue” channel output to connect an anode of a laser diode
BLUE-
“Blue” channel output to connect a cathode of a laser diode
GREEN+
“Green” channel output to connect an anode of a laser diode
GREEN-
“Green” channel output to connect a cathode of a laser diode
RED+
“Red” channel output to connect an anode of a laser diode
RED-
“Red” channel output to connect a cathode of a laser diode
Diameter of the output holes is 1.27mm (50mils), what matches to wires with the cross section up to
1mm2(AWG 17).
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How to power supply LPLDD 1A 16V 3CH
All channels are powered by one common input.
The minimum power supply voltage Vcc should be equal or higher than value given by formula below
(but not lower than 7V and not higher than 16V).
where:
-the supply voltage,
-the diode working voltage (at ),
-the desired maximum current.
When 2 or 3 channels, with different laser diodes, are used, Vcc should be calculated for each
channel independently. The highest value should be treat as Vcc.
We recommend the use of power cables with a cross-section of at least 0,1 mm2.
Depending on the used laser diode and PSU, you should monitor and assure proper cooling for
MOSFETs.
Measuring the current
To measure the current of the laser diode or any other load (e.g. test load resistor) connected to one
of the outputs, the voltage of the shunt resistor has to be measured. There are 3 shunt resistors, one
for each channel. To measure voltage across them, clear pads on the bottom of the driver can be
used.
Blue, green and red colors corresponds to “blue”, “green” and “red” channels. GND is common and is
marked with black rectangles. GND is also connected with input pins: 3, 4 and 8.
When value of shunt voltage (Ushunt) was measured, current (ILD) can be calculated:
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Sometimes, an easier way is to check voltage between GND inputs: either GND of control analog
input (pin 8), or GND of power supply (pins 3 and 4), and one of the leg of the transistor that are
shown in the pictures below.
Current of the laser diode can be calculated in the same way.
Adjusting the maximum current
Three separate trimmers (one for each channel) are used to set the maximum currents that are
supplied to laser diodes connected to driver outputs: BLUE, GREEN and RED.
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To set the maximum current:
1. Connect a power supply unit (“+” to 1, 2 input pins and “-“ to 3, 4 input pins), but don’t turn
it on yet.
2. Connect control signal equals +5V to one of pins: 5, 6 or 7 (depending on which channel will
be setting) and GND of the control signal to pin 8.
3. Connect load to one of the output: BLUE, GREEN or RED (depending on which channel will be
setting). It is better to use test load e.g. a resistor, than laser diode (because it can be easily
damaged).
4. Connect a multimeter (set to measure voltage) as it is described in Measuring the current
section.
5. Calculate voltage value that a multimeter should show (Ushunt) when desired current value
(Imax) will be achieved.
6. Turn on PSU.
7. Turn the trimmer clockwise until the desired Ushunt, which corresponds to Imax, has been
reached.
Current control
The value of voltage which is connected to one of the inputs: B, G or R, specify the portion of
maximum current supplied to corresponding outputs (BLUE, GREEN or RED). Those inputs are analog
and limited to 5V.This means that any signal, which maximum amplitude (respect to the GND) is
equal or less than 5V, can be used (also TTL with its logic levels of 0 V and 5 V) .
Usually, current of a laser diode is proportional to its optical power. Hence, power will be
proportional to signal connected to B, G or R inputs.
Example:
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Let’s say that you set (see Adjusting the maximum current section) and your laser
diode gives 500mW at this current.
When you will connect 2,5V to control input, you will get 50% of the current (200mA) and 50%
of the output power (250mW). Analogically by using 4 V you get 80% of the current (320mA)
and 80% of the output power (400mW), etc.
When you will connect 5V PWM with 50% duty, you will get 50% of the output power (250mW).
Increasing duty to 80% will increase output power to 80% (400mW).
End of example.
Laser diode current will always be equal:
where:
-voltage (0-5V) on one of the control analog input (X means channel: B, R or G)
-maximum current (0-1A) set with trimmer (X means channel: B, R or G)
or:
Protection
The analog input is protected by a 5V1 Zener diode on occasion there appears of the voltage higher
than 5 V. While this additional protection is offered, the user is still advised not to exceed 5 V on each
analog input.
The power supply input is protected against a too high or reverse input voltage by a transil diode.
The output of each channel of the driver is protected by a Schottky diode that prevents a reverse
voltage.
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