17mm buck-boost driver (TPS63020 and LT6106)

[Hiemal]

Page 8 post # 193 it was scoped

That doesn't show startup. That's just showing ripple currents and stability testing...

Unless I'm missing something completely.

 

[Onryo]

Think this was addressed in post 45 by adding a 100uF cap across the diode. One thing to note is that an output cap is normally chosen by its effective series resistance (ESR), because this is what determines output ripple voltage. Get a cap that has a ESR that is from 0.025-0.2ohms. AVX caps are nice. A SMD solid tantalum type if you got the space. Anyway when I get hold of one of these drives Ill scope the crap out of it =)

That doesn't show startup. That's just showing ripple currents and stability testing...

Unless I'm missing something completely.

 

[Hiemal]

Scope the crap out of it, and check it for spikes, because like I said, I'm using one of these chip's sisters, and using an LT6106 as well, and it's giving me a terribad startup spike. :/

I wonder if I need to increase the input capacitance... Hm.

 

[Onryo]

If you are using a TI chip there is a good chance you do not need the zener diode across LT6106. Most TI chips are already voltage protected and a zener cause all sorts of problems. Then there is the cap across the laser diode. It acts as a buffer so to say. When a surge of current comes in and the cap is "empty" it will fill to capacity. When the cap is "loaded" it will act like a "mini battery" and dump that energy back to the LD if needed. This is why it helps smooth out the choppy output from the boost. You probably know all this already so Ill get to the point. When you first turn on your laser and the output cap is empty it will absorb some of that current spike. You want your cap to be able to absorb that current spike asap. Having a high ESR will make the cap less responsive speed wise to the train of noise and spikes.

 

[laserluke]

You can use Tina-TI to simulate the startup spikes with different batteries... the output overcurrent at startup is intrinsically limited by the battery internal impedance and the resistance of the power switch that you are using...
-Luke

 

[laserluke]

It's not so simple... driving a large capacitive load could produce control loop oscillations. The same if you use a series inductor too high
The zener diode question has been widely discussed.

If you are using a TI chip there is a good chance you do not need the zener diode across LT6106. Most TI chips are already voltage protected and a zener cause all sorts of problems. Then there is the cap across the laser diode. It acts as a buffer so to say. When a surge of current comes in and the cap is "empty" it will fill to capacity. When the cap is "loaded" it will act like a "mini battery" and dump that energy back to the LD if needed. This is why it helps smooth out the choppy output from the boost. You probably know all this already so Ill get to the point. When you first turn on your laser and the output cap is empty it will absorb some of that current spike. You want your cap to be able to absorb that current spike asap. Having a high ESR will make the cap less responsive speed wise to the train of noise and spikes.

 

[Kizdawg]

I am going to do a build with this I am just still unsure what I want to do.. I have all sorts of stuff here but I just dont seem to have something that will work.. round without contacts and euda's heatsinks.. I could do it in a b50 or a erm c6.. That would not do it justis.. the c2 would be kewl but the fit is tight to the driver sink.. So I duno what will work. Any suggestions would be appreciated.. I love the driver but other than sinking it to a diode heatsink or sticking it in a pill I duno..

 

[foulmist]

I have tested it and there are no current spikes on startup. I mentioned that although I didn't take a scope picture of it..

LeQuack - check your feedback compensation loop or the output capacitance might be low. Do not put zener diodes.

 

[trinh hong phuoc]

Open source laser driver. Final version
happy testing

gerber files FINAL VERSION

eagle v6 files FINAL VERSION

TINA-TI simulation file


TINA-TI is a free Texas Instruments Spice-based analog simulation program

Inductor XFL4020-152ME

DigiKey parts:
D1 - 568-6287-1-ND
C2, C3, C4, C5 - 445-8028-1-ND
R3 (Shunt, package 0805) - WSLA-.01CT-ND
R2 (current set trimmer) - 3214W-201ETR-ND

R1 (5 Kohm), R4 (10 ohm) - package 0603, use components with a good temperature coefficient (<100ppm/C)
C6 (100uF) - package 1206
C1 (0.1uF) - package 0603, any good decoupling capacitor
R5 (470 ohm) - package 0603
C7 (10 nF) - package 0603

R5-C7 form the loop frequency compensation network.
C8 is optional (secondary pole for testing purposes).
The values of R5 and C7 can be experimentally adjusted.
With the given trimmer R2 the output current range is 0.1 to 2.1 A

.

Is it used for all diodes?-I want to ask about their power input,1 or 2pcs 3,7 vont

 

[diachi]

Is it used for all diodes?-I want to ask about their power input,1 or 2pcs 3,7 vont

Check the date on threads before you post ... the last reply to this thread was in 2012.

 

[Encap]

Is it used for all diodes?-I want to ask about their power input,1 or 2pcs 3,7 vont

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