OPEN SOURCE: "CC-Boost" - 2.4 Amp boost driver - RC1

[The Lightning Stalker]

Where's the inductor?

vvvvvvvv

This board is complete except for the coil
and RSENSE2

^^^^^^

 

[ARG]

Oh, missed that part. Would be best to get pictures of the specific one you're testing.

 

[The Lightning Stalker]

Oh, missed that part. Would be best to get pictures of the specific one you're testing.

The two being tested both look like this.
As you can see, they are identical except for
the coil and RSENSE2.

 

[rhd]

I can't see any obvious fault, but as a general comment, if it's getting burning hot to the touch as soon as you turn in on, something is wrong. It shouldn't get that hot that quickly.

EDIT: It might be a good idea at this stage to give one of the drivers to ARG to test under the same circumstances as to ones he tested.

 

[The Lightning Stalker]

Yeah. It doesn't happen right away, but
after maybe 5-10 seconds it is too hot to
keep my finger on it.
:thanks:

 

[ARG]

Yeah, I don't see any problems. Are all of the ones you assembled doing that TLS?

 

[rhd]

A couple things are confusing me here:

- It looks to me like the driver is only outputting 2V on your scope results. That wouldn't be boosting.
- Double check my math, but it looks to me like the ripple is 7 khz, which is nowhere near the frequency this driver switches at.

Can you please provide details about your test load? (number and type of diodes, resistor value and type)

 

[The Lightning Stalker]

Yes, the the two complete ones are both
behaving the exact same way.

The diodes are 1N5408 and the reisistor is
an Ohmite WNE1R0FE. I'll post more details
in the morning when I'm not so tired and
can think more clearly. :tired:

 

[djQUAN]

- It looks to me like the driver is only outputting 2V on your scope results. That wouldn't be boosting.
- Double check my math, but it looks to me like the ripple is 7 khz, which is nowhere near the frequency this driver switches at.

I believe he is measuring the voltage across the dummy load resistor hence it is 1A per 1V.

The oscillation is 6250Hz. (1/(0.8div*200us)) it is pretty low to be the switching frequency but rather high to be due to voltage drop of the battery which led me to believe it was something to do with the current feedback loop stability but I may be wrong.

 

[rhd]

Yes, the the two complete ones are both
behaving the exact same way.

The diodes are 1N5408 and the reisistor is
an Ohmite WNE1R0FE. I'll post more details
in the morning when I'm not so tired and
can think more clearly. :tired:

Ahhhh, there's the problem

You can't use wirewound resistors on testloads with switching regulators. Read here:

http://laserpointerforums.com/f65/trying-adjust-output-help-80908.html#post1162736

EDIT, a bit more discussion of the problem with your test load in this and the post after it:

http://laserpointerforums.com/f67/my-new-baby-6a-dummy-load-64160.html#post919388

 

[The Lightning Stalker]

Hmm, it was specified as being non-
inductive, <1nH, but I'll try swapping it out
just in case.

 

[djQUAN]

A few inches of wiring can easily add several nH of inductance too.

 

[rhd]

A few inches of wiring can easily add several nH of inductance too.

Also, for consistency and comparability, when you re-scope the driver using a non-wirewound resistor, can you scope the driver's output voltage, the same way ARG did, rather than just scoping across the resistor?

Ideally, if possible, using similar scope parameters, so that the results are directly comparable.

 

[ARG]

can you scope the driver's output voltage, the same way ARG did, rather than just scoping across the resistor?

Ideally, if possible, using similar scope parameters, so that the results are directly comparable.

I did mine without a resistor as well, just diodes creating the load.

 

[The Lightning Stalker]

Well, I clipped the test load directly to
the wire coming off the driver and the
battery on the negative, and used a Rideon
PF1262-0R01J1 10mΩ thin film resistor and
both drivers appear to have failed. They
are stuck at around 2A. Turning the pot
appears to do nothing now except change the
amount of ripple, and the ripple is never
below +/-500mA throughout the entire range.

Also there are bad transients at power up
and power down. I'm starting to think I
was either sold fake or bad chips or they
overheated in the oven during reflow.
Both are definite possibilities because
another board I flowed at the same time
also appears to be malfunctioning.

 

[crazyspaz]

@TLS: I have 40 ic's that I bought off rifter who didnt need all the ones he ordered. I could send you a few if you want to pay for shipping, of that would help you figure out the problem.