coulomb
Posts: 168
Joined: Sun Jun 10, 2018 8:32 pm
Location: Brisbane, Australia

Re: Troubleshooting and repair for On-board Charger, DC-DC Converter

Tue Jul 31, 2018 10:32 pm

kiev wrote: i'm not sure why the DC is only reading 247--i would expect to see ~340vdc with 239vac mains.

Because it's pulsing DC with no significant smoothing capacitors to keep the voltage near the peaks. If that PFC diode was working, we'd see the ~340 VDC at the 3 large capacitors (but still ~247 VDC at the bridge output). The exact reading depends on whether the meter is true RMS reading or average reading, and how much smoothing is happening due to small capacitances here and there. Particularly the 105 (1 μF) between pins 5 and L1A.

Everything is pointing to an open circuit PFC diode at this point.

I like @skylogger's idea of bypassing open circuit components. It may even be possible to bypass some shorted components by judicious cutting of the headers coming off the waffle plate™.

[ Edit: bypass some shorted components. ]

skylogger
Posts: 76
Joined: Sun Dec 14, 2014 3:54 am

Re: Troubleshooting and repair for On-board Charger, DC-DC Converter

Wed Aug 01, 2018 4:05 am

I'm using a pretty cheap volt meter that is probably way out of calibration, so that would affect my measurements also.
I've soldered four wires to a terminal strip, 2 wires from across the 3x BIG electrolytics caps, and 2 wires going out to the
transformers. On the Ohm meter readings (in diode testing mode) when I go across the combinations of these 4 points,
I see readings of 0.8xx one way and Infinity the other which is what would be expected reading across two diodes in series
that are across the IGBT or MOSFET or what ever it is. So to me, I don't see any shorts or opens across the power devices.
When I first apply AC at the Input, The voltage across the Electrolytics measure 348vdc but then after a 10 seconds, I start
seeing this start counting slowly down. I don't leave the AC applied for more than a minute, as this might be a sign that
something is warming up. I've got an old 50 year old oscilloscope I might try and fire up, and see if I can see any oscillating
signals going to the pads around the 1k gate pull down resistors. I've got to rig up an isolation transformer to power the oscilloscope,
because its earth lead would flow back through hose wiring back to Neutral (back at the meter box) and cause problems.
I suspect that there are no gate signals to cause the power devices to switch. This might be due to drivers being damaged, or may just
be due to it not being in the car and not having the communications cable pluged in to enable running of the charger.

I did notice that when this Charger was fitted in the car, and I plugged in the AC Cord to the car, The charging light on the dash would
come on and blink a few seconds and then the yellow triangle with the ! would appear and charging would shut down.
To me this means the charger was at least telling the rest of the car that AC power was being applied to the charger.

coulomb
Posts: 168
Joined: Sun Jun 10, 2018 8:32 pm
Location: Brisbane, Australia

Re: Troubleshooting and repair for On-board Charger, DC-DC Converter

Wed Aug 01, 2018 6:51 am

skylogger wrote:I'm using a pretty cheap volt meter that is probably way out of calibration, so that would affect my measurements also.

I get nervous when people use cheap multimeters on gear with 400 VDC. Might I suggest at least a CAT II model from Jaycar or similar for maybe AU$50?

So to me, I don't see any shorts or opens across the power devices.

I'm not convinced yet that you have checked the PFC MOSFET/IGBT and diode. The back diode for the PFC MOSFET/IGBT should read around 0.4 V, not around 0.8 V.

When I first apply AC at the Input, The voltage across the Electrolytics measure 348vdc but then after a 10 seconds, I start
seeing this start counting slowly down. I don't leave the AC applied for more than a minute...

I can appreciate that. But how far does it sag in that minute? Only to say 340 V, or way under 300 V?

It's starting to sound like either the PFC diode or inductor are intermittently open circuit. Ah. Or the input relay is disconnecting, and the 4.7 Ω resistors across the input relay are open circuit. Is it possible to hear the relay operate, or is it too hard to get to, and/or too much other noise?

Another thought: maybe the 4.7 Ω resistors are OK or at least conducting to a degree, and the input relay isn't coming on. Then the PFC MOSFET/IGBT might be coming on, and possibly staying on, thus killing the mains voltage, so the three large capacitors slowly discharge through their bleed resistor and other leakage.

I've got an old 50 year old oscilloscope I might try and fire up, and see if I can see any oscillating
signals going to the pads around the 1k gate pull down resistors. I've got to rig up an isolation transformer to power the oscilloscope,
because its earth lead would flow back through hose wiring back to Neutral (back at the meter box) and cause problems.

I guess it's OK to use the isolating transformer for the lower main gate resistors, but I would not use it for the upper ones. This is because the reference point, to which you'd be connecting earth of the scope, would have high amplitude, high frequency square waves on it, which could cause all sorts of problems with the added capacitance to ground/earth. But perhaps you were only thinking about the PFC switch, not the full-bridge switches.

Be very careful doing any of these measurements, as the chassis of the scope, and possibly its knobs or their grub screws (if any), would be live. The negative end of the bridge rectifier, which you might be thinking of as earth, actually has negative half-sine waves of about 340 V peak amplitude with respect to earth. I would prefer to use a dual trace scope, and use the subtract function to display the difference between channels 1 and 2. Leave the earth leads floating, and don't use an isolating transformer. Assuming of course that the old scope has this capability.

But I don't expect to see any full bridge switching signals without at least a CAN packet to turn the charger on. You might see switching for the PFC MOSFET/IGBT, however. These might appear on pin 6/J8, with respect to pin 5/J10 (which could go to the gate and emitter of the PFC MOSFET/IGBT respectively).

I did notice that when this Charger was fitted in the car, and I plugged in the AC Cord to the car, The charging light on the dash would
come on and blink a few seconds and then the yellow triangle with the ! would appear and charging would shut down.
To me this means the charger was at least telling the rest of the car that AC power was being applied to the charger.

Yes, that's encouraging. I think it means that the control board has power and is able to transmit CAN packets.

skylogger
Posts: 76
Joined: Sun Dec 14, 2014 3:54 am

Re: Troubleshooting and repair for On-board Charger, DC-DC Converter

Wed Aug 01, 2018 1:44 pm

JRAY3:
Can you PM me the VIN number of your car, or post it here? I need to use a USA VIN number when contacting 2nd hand parts places in USA.
I want to see what is available as a backup if I can't get my original charger fixed.
All of your previous PMs have disappeard out of my Inbox for some reason. Maybe send me one more PM to see if its working again?
Great that you posted the charger part numbers here that you have come across. When I try using my VIN number and contact USA sources, they can't use it, and the chargers here in Australia have different part numbers. The guts of the chargers look identical though. And the USA models cater for 240vac Input. There are lots of parts different because of Left Hand Drive and Right hand Drive, but the hose and connector mounting all look same between USA Chargers and Aus(japan) chargers, so i'm still not sure why they have to use different charger part numbers.

kiev
Posts: 930
Joined: Sun May 03, 2015 7:15 am
Location: The Heart o' Dixie
Contact: Website

waffle plate™ circuits

Wed Aug 01, 2018 9:02 pm

While searching the intertube i found this collage of X-ray images for the waffle plate™ showing components and traces below the epoxy coating.

Image
kiev = kenny's innovative electric vehicle

coulomb
Posts: 168
Joined: Sun Jun 10, 2018 8:32 pm
Location: Brisbane, Australia

Re: Troubleshooting and repair for On-board Charger, DC-DC Converter

Wed Aug 01, 2018 10:25 pm

Brilliant! Thanks for sharing.

Now I need a 130 kV source for my home-made X-ray machine for my home reverse engineering lab :evil:

coulomb
Posts: 168
Joined: Sun Jun 10, 2018 8:32 pm
Location: Brisbane, Australia

Re: Troubleshooting and repair for On-board Charger, DC-DC Converter

Wed Aug 01, 2018 11:01 pm

It certainly looks like two separate full-bridges after all, and 8 separate gate drives from the lower right corner. My guess is IGBTs, hence the four back diodes that don't even project above the epoxy level and so aren't visible without the X-ray or X-cavating scalpel. There seem to be some gate pull-down resistors in there as well, though I'm going to say no gate series resistors, unless they're a lot smaller than the pull-down resistors.

Edit: I'll go with IGBTs for the PFC stage; again one external back-diode per pair of IGBTs. Again, separate gate drive for the two PFC IGBTs.

The PFC diode is also two devices in parallel.

skylogger
Posts: 76
Joined: Sun Dec 14, 2014 3:54 am

Re: Troubleshooting and repair for On-board Charger, DC-DC Converter

Thu Aug 02, 2018 12:49 am

Hi Coulomb:
The DMM I'm using is a UNI-T CAT III I bought from Altronics rated to 1000V When I said cheap, that refers to price and accuracy of calibration, It's just not a Fluke if you know what I mean.

The 0.8 on the DIODE test that I am measuring is when the + of the meter is connected to the - if the Electrolytics, and the - of the meter is connected to the + of the BIG 3X Electrolytics. This would be showing the reverse of normal with a path going through both blocking diodes in series, and also these 2 are parallel to the 2 in the high side also. When I swap the meter leads to + to + of Electrolytic and - to - of Electrolytic, it says infenity.

In trying to check the 2 x 4.7 resistors in the doghouse, I can do a ohms check from the Neutral Input ring terminal and the other lead on pad 1 of the white strips, which would be measuring across just the 2x 4.7 resistors and the EMI Filter. I am getting a reading of 9.7R so the EMI Filter is probably adding the 0.3R If I apply MAINs AC Input, and check the voltage at these same points, I see a voltage drop of 1.57vac
At this same time, I have a clamp AMP meter on the LIVE AC line in, and it is only measuring 0.09amps Since it's not drawing much current,
This would make me think the 1.57vac is mainly being droped across the 2x 4.7R Resistors and the relay is still open?

The situation on the voltage across the 3x electrolytics being 348vdc and then gradually dropping, may be due to my MAINS source. My house is powered by Solar power only, so my Mains is actually from an inverter. This may result in some weird readings when there is a surge trying to charge the electrolytics, and they charge up to 348vdc but now that I've been brave enough to let it run a few minutes, it only drops to 345.5vdc and stays constantly there for the rest of the testing session. Depending on if its cloudy weather or batteries fully charged, I can see a few volts difference in output of the power inverter feeding my house, so that will vary results a bit. Some days I might see 239vac other days 241vac etc.

I like your idea of using the oscilloscope in dual trace diff mode. Saves me hastle of setting up the isolation transformer and less likely of getting BBQ'd. So if I'm probing around the 1K gate pull down resistors, what other point would I use as the reference point. would this be the + or - of the 3x electrolytics depending on if I was checking the high side or low side? These would connect to the emitter/drain of the power devices. Would the signals for the gate switching come in on pads 22 and pads 23?

Would it be worth unplugging the transformers, and in place of their primaries, temporarily put a 10w 10k dummy resistor.
This would give a 30mA current x 10k ohms = around 9 watts load, just to see if anything in the power devices work with a small load.

I might have to put the charger back in the car and connect the communications cable to it so that the controller PCB is happy before it will generate the gate drive signals. It might run for a few seconds before the error is detected and shuts down.

coulomb
Posts: 168
Joined: Sun Jun 10, 2018 8:32 pm
Location: Brisbane, Australia

Re: Troubleshooting and repair for On-board Charger, DC-DC Converter

Thu Aug 02, 2018 2:59 am

skylogger wrote: The DMM I'm using is a UNI-T CAT III I bought from Altronics rated to 1000V

That's reassuring.

The 0.8 on the DIODE test that I am measuring is when the + of the meter is connected to the - if the Electrolytics, and the - of the meter is connected to the + of the BIG 3X Electrolytics.

Yes, that's what is expected. These are the two back diodes across the main IGBTs. I was still trying to work out why there was nothing on the 3 large electros. But you say there is 345-348 V there now, so that's fine.

I'd still like to see the 0.4 V from the PFC IGBTs. You should see this on the other side of the PFC diode, e.g. J21 to J19.

In trying to check the 2 x 4.7 resistors in the doghouse, ... I am getting a reading of 9.7R so the EMI Filter is probably adding the 0.3R

More likely your multimeter leads add 0.3 Ω to the reading. At 14 ARMS, the I²R loss would be 59 W.

If I apply MAINs AC Input, and check the voltage at these same points, I see a voltage drop of 1.57vac

Interesting. I think it could be out-of-phase inductive drop, but it might indicate resistance. There would be a spike of current when the capacitors charge up near the peak of each mains half-cycle.

At this same time, I have a clamp AMP meter on the LIVE AC line in, and it is only measuring 0.09amps Since it's not drawing much current,
This would make me think the 1.57vac is mainly being droped across the 2x 4.7R Resistors and the relay is still open?

As above, I just don't know. It depends on the leakage inductance of the EMI filter inductors.

The situation on the voltage across the 3x electrolytics being 348vdc and then gradually dropping, may be due to my MAINS source. My house is powered by Solar power only, so my Mains is actually from an inverter. This may result in some weird readings when there is a surge trying to charge the electrolytics, and they charge up to 348vdc but now that I've been brave enough to let it run a few minutes, it only drops to 345.5vdc and stays constantly there for the rest of the testing session.

Well sleuthed. I think that explains it exactly. So the front end seems to be working as expected, except that there is no PFC boost.

So if I'm probing around the 1K gate pull down resistors, what other point would I use as the reference point. would this be the + or - of the 3x electrolytics depending on if I was checking the high side or low side?

Use the negative side of the big electros, and measure only the gates for what you think are the lower IGBTs. It won't hurt to measure the upper IGBT gates, but if they are switching, then they will have the ~340 VDC square wave superimposed on them. The reference for the upper IGBTs will be their outputs; the IGBTs act on the base to emitter voltage, and the upper IGBTs are emitter followers. It might make sense to measure the outputs with respect to big electro minus first, to see if there is any activity. As mentioned earlier, I don't expect to see switching pulses without a CAN message to start charging, and that likely requires either the charger in the car, or some service aid that we haven't discovered yet. In the Elcon/TC chargers, you could insert a jumper and get artificial switching pulses for testing. I think we need a fair bit of Kenny-work before we get to that stage :mrgreen:

In short, there probably isn't much more that you can do till then.

Would it be worth unplugging the transformers, and in place of their primaries, temporarily put a 10w 10k dummy resistor.

I don't think so. Also, 9 watts in a 10 W resistor with no heatsink will get extremely hot.

I might have to put the charger back in the car and connect the communications cable to it so that the controller PCB is happy before it will generate the gate drive signals. It might run for a few seconds before the error is detected and shuts down.

Yeah. A slow test cycle, to be sure. It will be great to figure out some bench testing techniques.

skylogger
Posts: 76
Joined: Sun Dec 14, 2014 3:54 am

Re: Troubleshooting and repair for On-board Charger, DC-DC Converter

Thu Aug 02, 2018 2:55 pm

Hi Coulomb / KIEV:
Would connecting a transformer with diodes as a test circuit like this drawing, allow to generate signals for the gates to allow testing of the IGBT's, or would this end up as a fireball of High side and Lows side switching on at same time? I figure connecting the test transformer primary to the active and neutral at the point it's already had EMI Filtering might work. I know centre tapped 3v +3v transformers are a bit hard to find. There are common audio transformers quoted as 1K PRI to 8R SEC ratio but they probably don't have the 350-400v rating. I'd also have to work out how to temporarily cut the true signals from the controller section so there is no chance of interference.
What do you think the original Gate signals look like? They probably would be around 3v but amplitude would vary according to charging current / voltage requirement. I've also heard that they normally use a higher frequency like 400hz or something to get more efficiency out of the smaller transformers. So just for testing, this should generate two 3v half wave 50hz signals 180 deg apart.

Image

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