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d20180

Tue Dec 23 2008, 05:36PM

Registered Member #1828 Joined: Sat Nov 29 2008, 03:00PM
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Posts: 55

I have gotten to the point of checking for the square wave on pin 2 of U4 and U5, and nothing. Can someone walk me through this?

StevenCaton

Tue Dec 23 2008, 08:18PM

Registered Member #1845 Joined: Fri Dec 05 2008, 05:38AM
Location: California
Posts: 211

Verify that the signal youre injecting is in fact 5V at 100KHz

If youre detecting nothing, try reversing the two wires that go to the current feedback terminal.

You are connecting one scope probe to the circuits ground and one to pin 2 right?

d20180

Tue Dec 23 2008, 09:06PM

Registered Member #1828 Joined: Sat Nov 29 2008, 03:00PM
Location:
Posts: 55

I am now grounding on the ground term for t61. I show the signal on 1,2,3 on U1 but not 4. My electronic experience stops at about 1969 chevy.

StevenCaton

Wed Dec 24 2008, 02:48AM

Registered Member #1845 Joined: Fri Dec 05 2008, 05:38AM
Location: California
Posts: 211

You do have your transformer plugged in right.... which provides 5v for the logic chips such as the U1 (which has six not gates in it I believe)

I really don't think U2 or U3 should affect what you are testing for at this point, so if you still don't see a signal, you might have a damaged U1 chip. I ran into similar problems like the ones your having now with that system and the cause was often a bad chip. Try putting in a new U1 if nothing else seems to work.

d20180

Wed Dec 24 2008, 11:49AM

Registered Member #1828 Joined: Sat Nov 29 2008, 03:00PM
Location:
Posts: 55

Thank you, That was the info I needed. (Googled NOT gate, saw how it worked, looked at the data sheet for U1. 5V@pin 14, ground at pin 7, signal at 1,2,3 none at 4= bad chip.) Replaced and I now have the signal at p2 U4&5. And most importantly I now have a clue where to look for the path of the magic smoke in the IC's!

THANKS!

d20180

Wed Dec 24 2008, 01:46PM

Registered Member #1828 Joined: Sat Nov 29 2008, 03:00PM
Location:
Posts: 55

Oh well, no usefull help from google. On the differential measurement on e1,e2. (Pg 88 fig 5-3) I don't have a clue. Are e1&2 on the same igbt, between them? How should I set up the probes/scope, ground leads together? On the other hand the Mechanical part is coming along fine, I made the plug with a lip.

Thanks

StevenCaton

Wed Dec 24 2008, 07:55PM

Registered Member #1845 Joined: Fri Dec 05 2008, 05:38AM
Location: California
Posts: 211

Ok.... so your 5v square wave comes in on pin 2 of each gate driver. (the gate driver IC's are U4 and U5) If you can see the signal on pin 2 of each then that's good. Each gate driver has an "enable" which is pin 3. In order for you to take the differential measurements you will have to enable each gate driver to allow them to function. Apply 5v at 100% duty cycle into the external modulator. Then you gate drivers should be enabled because pin 3 of each drivers will be high with 5v. In case you haven't noticed already, the external modulator terminal is where you will later connect the interruptor. All the interruptor does is enable and disable your gate driver IC's at a given frequency and pulsewidth (for example.... 100Hz at 150us)so the IGBT's dont explode from too much power.

Ok, so now that you are receiving 5v at 100KHz on pin 2 of each and your chips are enabled, you can take the differential measurements. If you take a differential measurement across the two terminal on the circuit board, you will see +15v high and -15v low, +15 high -15 low, etc. If you measure the same signal on an IGBT it should now be +30v high -30v low. This is because, of course, the Gate driver transformer stepped it up to 30v high and low instead of 15v.

To take a differential measurement with an oscilloscope do the following. (It requires two separate probes)
1. connect the ground leads of each probe together
2. set channel one to ADD
3. set channel two to INVERT. (just find the add and invert buttons and push them)
Since your probes's ground leads are tied together, you have two left to connect to a circuit. So connect one lead on one probe to the IGBT's collector, and connect the other lead on the other probe to the IGBT's emitter.

Also note that you are not taking a measurement across both IGBT's. Take the differential measurement I described from Collector to emitter on each IGBT separately.

d20180

Wed Dec 24 2008, 10:49PM

Registered Member #1828 Joined: Sat Nov 29 2008, 03:00PM
Location:
Posts: 55

Oh well, that is enough for tonight. But I got a good start on the secondary.

Austin

Thu Dec 25 2008, 11:45AM

Registered Member #1169 Joined: Wed Dec 12 2007, 09:16AM
Location: Portland OR
Posts: 251

your secondary is looking very nice

d20180

Thu Dec 25 2008, 12:33PM

Registered Member #1828 Joined: Sat Nov 29 2008, 03:00PM
Location:
Posts: 55

Thanks,

U62 is only putting out 1.7v both U62&U61 are hot (finger on heatsink ~ 3sec)
replacing r3&U62. U62 was good, everything passed on the first check.

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