creating laser diode driver circuit

Thread Starter

mahmut_kelesoglu

Joined Aug 12, 2022
58
hello dears,
ı have to design laser diode driver circuit. ı need to use transistor, regulator or opamp. also ı need to take feedback, and also show the set and read current values to a screen (it may be computer screen).

the frist two part is very important to me. how to create a driver with given components, and also how to take feedback?
thanks in advance.
 

ericgibbs

Joined Jan 29, 2010
16,448
hi mk,
What is the rating of the Laser diode, and what power level do you require, also is it a pulsed laser or continuous.?

E
 

Papabravo

Joined Feb 24, 2006
19,346
hello dears,
ı have to design laser diode driver circuit. ı need to use transistor, regulator or opamp. also ı need to take feedback, and also show the set and read current values to a screen (it may be computer screen).

the frist two part is very important to me. how to create a driver with given components, and also how to take feedback?
thanks in advance.
It is very hard to do a design when there is a complete lack of actual requirements. Also, your list of "given components" may be incomplete. It is generally unwise to specify the components before articulating the requirements.
 

Thread Starter

mahmut_kelesoglu

Joined Aug 12, 2022
58
hi mk,
What is the rating of the Laser diode, and what power level do you require, also is it a pulsed laser or continuous.?

E
it is a continuous laser diode.
actually, ı need to "design a circuit for a laser diode up to 250 mA, 2 A, and 5A."
these current values are steps of one project.
 

Thread Starter

mahmut_kelesoglu

Joined Aug 12, 2022
58
It is very hard to do a design when there is a complete lack of actual requirements. Also, your list of "given components" may be incomplete. It is generally unwise to specify the components before articulating the requirements.
ı have written main components. these are not all the components actulally.
 

DickCappels

Joined Aug 21, 2008
9,353
What is the voltage across the laser diodes at those currents?
Are there any restrictions on the power supply for this circuit?
Are there any restrictions in the circuit topology?

Might be very simple or it may be ...
 

Thread Starter

mahmut_kelesoglu

Joined Aug 12, 2022
58
What is the voltage across the laser diodes at those currents?
Are there any restrictions on the power supply for this circuit?
Are there any restrictions in the circuit topology?

Might be very simple or it may be ...
the voltage level is 5 V DC
there are no restrictions on the all circuit.
 

Thread Starter

mahmut_kelesoglu

Joined Aug 12, 2022
58
Yes, but picking the components first is the wrong approach to solving the problem. You might want to start by specifying an output power level or maximum current level.
actually ı did not pick the component. these are given.
also, the specified current and voltage levels are given.
 

DickCappels

Joined Aug 21, 2008
9,353
What is the voltage across the laser diodes at those currents?

Are there any restrictions on the power supply for this circuit? <== Is this the +5V supply?

You should consider an analog (non-switching) drivers along with switching versions. Could be as easy as rolling off a log. You can get some ideas by Googling transistor current source.
 

WBahn

Joined Mar 31, 2012
27,509
hello dears,
ı have to design laser diode driver circuit. ı need to use transistor, regulator or opamp. also ı need to take feedback, and also show the set and read current values to a screen (it may be computer screen).

the frist two part is very important to me. how to create a driver with given components, and also how to take feedback?
thanks in advance.
How do you plan to do the last part? Are you able to just use an off-the-shelf system to probe the circuit and display the result?

What are the "set" and the "read" currents? You mentioned three different current levels in one of your posts. How do those relate to these "set" and "read" values?
 
have to design laser diode driver circuit. ı need to use transistor, regulator or opamp.
for a laser diode up to 250 mA, 2 A, and 5A.
It would really help to know the part number of the laser diode you are working with. Looking at the specification of Osram V107C021A-940 for example, the forward voltage is listed as 2.15V and this is confirmed by the graph at 5A:
1664452265240.jpeg
The threshold current is 0.82A so this would not work at 250mA but maybe yours is different?

A constant current driver with an op into the base of a transistor with emitter via a resistor to ground with feedback from the emitter is a simple way of changing current according to voltage input but your range from 0.25A to 5A makes this more difficult. Suppose you use a 0.1 ohm resistor for 5A so the power in the resistor is 2.5W. You'd need a power supply of at least 3V able to deliver 5A. You'd need a power transistor able to dissipate power which is why it helps if the power supply voltage is not higher than 3V.

And for 250mA the feedback voltage would drop from 0.5V to 0.025V so you'd need a good rail to rail op amp - better to leave the reference voltage into the op amp fixed, and switch between emiiter to ground resistors.

So please let us know the part number of your laser diode and any power supply constraints!
 
Top