zetafunction
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Sun Sep 13, 2020 8:47 am

When turning on the power, FB looks like this:

Image


And the output like this:

Image
Image

kiev
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Sun Sep 13, 2020 9:50 am

Interesting linear slope of the FB signal rising while waiting for something to happen. Coulomb is probably correct in that if gets no FB during the CS capacitor charge up time, then it latches off--after about 0.2 seconds.

The output signal is being driven at the ~75kHz PWM frequency, but the voltage looks to be limited by some sort of capacitive loading. The output typically going to 4V according to datasheet. The duty cycle is at the max of about 65%.

The output is going thru a 330 Ohm to the gate of the FET, which has a 100k to ground.

What does the output look like after you get the chip to start and run?

[edit] the FET datasheet indicates the cutoff voltage is about 2V, so it may not even be turning on the FET. rating is for 4.5V Gate to Source voltage. hmm? the rollover begins around 1.5V and it never reaches 2.3V--not turning ON.
Last edited by kiev on Mon Sep 14, 2020 6:27 am, edited 2 times in total.
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zetafunction
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Sun Sep 13, 2020 10:26 am

That is the output pin, when it is running:

Image
Image

And thats the output directly after shorting pin 1 and 2 with a resistor:

Image

When it is running it is definitely switching the FET.

zetafunction
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Sun Sep 13, 2020 10:47 am

Also here are some measurements between Drain and Source of the FET when turning on the power:

Image
Image

kiev
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Sun Sep 13, 2020 11:11 am

Those are some great scope captures, thanks for doing all the work to share those here.

For some reason at startup the Output of the regulator is not able to drive the voltage high enough to turn the FET ON. With a little jump start you are able to get it working, which seems to indicate that all the peripherals are okay, i.e. the TL431, the PC314, all the passives, the FET. To me this points to a semi-defective Flyback Regulator IC702; semi-defective because it seems to work after the jump start, but won't start on its own.

Is there anything external to the regulator that could cause this?

Examine the components and solder joints from the output to the FET, 330R, 100kR, solder connections at both ends.

Have you tried resoldering the pins of IC702.

[edit] add the capacitor C841 and the transformer T302, to the list of external components.
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zetafunction
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Sun Sep 13, 2020 12:12 pm

I have to thank you for your time and patience!

I think I desoldered all external components and tested them one by one at this time, including IC702 and I renewed the solder joints of T302. I also desoldered C841 and measured 150uF across all frequencies.

For further reference, desoldering C841 works best with hot air, but it is absolutely neccesary to cover up the area around with small copper plates to not melt the connector. And even then it is really hard to desolder, since there are a lot of copper traces around the cap. I also preheated the area to shorten the time high temperatures are applied.

I think I will order a new IC702 IC, are there any other things I should consider ordering?

kiev
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Sun Sep 13, 2020 1:20 pm

Well i thought of some more external stuff to consider--the PFC chip and the connection to the waffle plate on the secondary side. Is there any possibility that one of the components down stream on the secondary power supply could affect the switching? i don't really think so but i want to throw it out there for consideration.

i think you said that you did the diode check on the waffle plate and it all rang good, so hopefully no issue there.

Here is a drawing for the flyback regulator circuit primary and secondary sides.
Image

Image


If i were to order parts for a repair, i would consider replacing all the actives in this circuit TL431, TLP127, NJM2369, and the TR310. Also possibly all the ceramic capacitors.

And the blue snubber caps--replace them with higher voltage rating caps.
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zetafunction
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Sun Sep 13, 2020 7:18 pm

I just ordered some parts and will update you as soon as they arrive. The NJM2369 is actually pretty hard to buy and the delivery time is about 14 days.

The waffle plate measured out fine. Also after removing the plate the current draw stayed exactly the same, so I do not think that the plate is involved in this issue at all.

Thank you for your awesome drawing, I did a drawing of this circuit myself but yours looks so much better! :-)

coulomb
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Mon Sep 14, 2020 2:28 am

kiev wrote:Interesting linear slope of the FB signal rising while waiting for something to happen.

Looks like the op-amp is open drain with a current source as the pull-up. Constant current into a capacitor gives constant dV/dt.

That gives some hope that pulling pin 2 low is at least anticipated, if not designed for.

bezzeb
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Thu Sep 17, 2020 6:12 am

Good day
Please help me, my car not charging
No 14v on the battery, the yellow car icon is on and there is no icon "READY"
After checking Lexia I got errors
Charger
06 AC input voltage abnormal
ev-cu
u1113
P1AF4
U1900
U1901
P0560
P0562

Image
After opening the charge, I saw an exploded large black capacitor and two small ones with a crack
Fuses in charge and MCU are normal
Resistors checked and readings are normal 10Ohm
The relay works well too (10-0 Ohm)

3 capacitors have been replaced, but the error persists
What could be the problem?

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