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I'm trying to replicate this circuit for a 2W laser diode engraver. I could understand most of the other components except the current source schematic (Pg. 5, Fig 4). I understand that the TLC271 is being operated in high-bias mode (cause the datasheet says that when the bias select pin is...
I intend to use this to cut stencils made from either Mylar or plastic transparency sheets. I first thought of getting a Silhouette Cameo for this but that does not seem to cut below 0.5mm pitch. Hence the laser. I think I need to do more research on this. Thanks again Brian.
Thanks Brian. Yeah 300mW does sound rather weak to me as well. Hence the 1W IR laser. Why does the current have to be less than 1A? Would I be able to drive **broken link removed** with this IC?
I'm trying to build a small laser cutter for making SMD stencils (among other things). Though I'm told that a 300mW laser should work fine here, I thought of experimenting with a 1W IR laser and I was hoping someone can suggest a suitable driver chip for this. Would something like this work? -...
Great thanks! I cannot seem to find a variable resistor in LTSpice though. Is that a custom component?
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Actually dont bother. I found one on the LTSpice yahoo group! Thanks again!
Thanks crutschow! This certainly helps.
I'm also evaluating a design based on the LM3150 by TI. It seems more simple and pretty much has the same set of specs as this one.
OK! Now if I design this SMPS for a 6A consistent load (where the peak current supplied is 6A), then it'll still be able to start the motor? Does that reduce the life of the transformer?
Right! This means that my transformer would have to be around 24V, 8A to give me a power output of 120W which is what is needed at the output (at 100% efficiency). In this case, I'm designing for a current draw of 10A. However, only about 5.5A of this will be actually used when the motor is in...
Oh! So if I were to reduce the switching speed, I'd have to go for an expensive inductor and if I were to keep it the same, I'd have to go for a bigger transformer which is again very expensive! :( Any ideas on how I can resolve this conundrum?
Also, the lowest Rds P-MOSFET I could find in a...
Got it crutschow! Thanks for that. I had never thought of it.
FvM - How do I calculate the value of the pull up? Should it be the standard pullups of around 47K? Also the Z-diode should be less than the Vgs rated in the FET's datasheet (which in this particular case is +/- 20V)? Also, if I use...
OK! Let me change that and come back with a modified design for the gate driver.
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Here is a modified schematic with a totem pole driver for the P-MOSFET. Have I got this right?
So if my DC voltage is 32V as in this case, the Vgs of the MOSFET needs to be 32+10=42V? Also this is a P-MOSFET. I did a basic search and found that P-MOSFETs should be driven by a non-inverting driver (which this chip is). Would I need some sort of TTL-CMOS level converter between the TL494...
Thanks Brad! Even those are expensive too! :(
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Attached here is a first-cut schematic.
Following crutschow's advice I changed the operating frequency to 120KHz to reduce the inductor sizeand following FvM's advice I replaced the BJT's with a MOSFET (IRFHM9331). Also I've...
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