kiev
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Comparators and Op Amps, Starting and Running Notes

Sun Nov 08, 2020 10:11 am

i've changed my mind on the identification of IC102 and IC203, from dual op amps to dual comparators. i see a common hysteresis design used on these circuits as on IC202 which seems to be a quad comparator. The only dual op amp seems to be IC208, etched and barely marked "1251".

Modified the IC202 comparator drawing to add a common via path that was found linking several transistors and CN201 pin 6 which is the +12V switched input signal.

This common via seems to have a latching feature. If any of the transistor paths are true, then the drain path for the diodes is completed. After it starts then the diode path will be latched as long as the key switched 12V is applied.

What this means:
The DCDC can start and turn ON without a key-switched 12V (for example during EVVSE charging of the pack), but a key will keep it ON (such as while driving). This is the section of control logic that makes this possible.
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eldenh
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Location: Port Angeles, WA

Re: Gen1 DCDC Converter Troubleshooting and Repair

Mon Nov 09, 2020 8:37 am

So the switched 12v supplies several functions when the key turns it on, but can be powered from another source when charging with an EVSE. How is that commanded when there is no connection from CN201 and the EVSE connector?
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kiev
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Location: The Heart o' Dixie
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Re: Gen1 DCDC Converter Troubleshooting and Repair

Mon Nov 09, 2020 11:46 am

eldenh wrote:So the switched 12v supplies several functions when the key turns it on, but can be powered from another source when charging with an EVSE. How is that commanded when there is no connection from CN201 and the EVSE connector?


The 12V on pin 6 is the Switched supply from a relay circuit [A-08X] that gets energized by the EV-ECU when it detects the key switch; the EV-ECU can energize that relay at anytime, for example whenever it detects EVVSE also.

But the DCDC will function without that signal altogether as long as there is sufficient HV to create Vsub, TP201 within range, and that there is a 12V on the Output side.

The switched 12V in the DCDC provides a latching action on the third transistor path of the common via. It is also somehow tied in to a signal for the PWM, still under investigation.

Image

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Last edited by kiev on Wed Nov 11, 2020 8:46 am, edited 1 time in total.
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kiev
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Re: Gen1 DCDC Converter Troubleshooting and Repair

Mon Nov 09, 2020 10:56 pm

Added to page 1 schematics post: temperature and current sensor signal conditioning.
Image


My crude little test data is not very useful to determine the cutoff temperature, but the reference voltage set point is at about 3V (3.042) with the Low Threshold at 2.6 and the High at 3.3V. This corresponds to a sensor resistance ranging from about 5k to 10kΩ, but i did not measure an intermediate temperature point to correspond to that range.

At room temperature i measured about 100 to 120kΩ, and you would not want the heatsink to get so hot as to boil coolant in the chill plate, so i would need to measure the slope somewhere between ambient and boiling water temperature. Maybe there is a standard curve for 100kΩ ambient thermistors.

The current sensor is an LEM hall-effect type. The gain of the current sense amplifier is about 1.7 and that signal is summed with some transistor logic that i will put all together on another sheet.
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eldenh
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Location: Port Angeles, WA

Re: Gen1 DCDC Converter Troubleshooting and Repair

Wed Nov 11, 2020 11:40 am

I found a chart for 100K thermistor at https://mikroelectron.com/ProImg/X4/186 ... 1f0c80.png. It looks like 10K corresponds to 180 F.

I've been puzzled that I had been reading 5v at the gate of Q203 and only 0.28v at the vias feeding 5v to IC202. Checking Q229, all I find is an open circuit. So I think I have damaged the 5v supply circuit. It seems to me that it should be possible to test the LV section by supplying about 15v to TP201. My ohmmeter shows 3.65K from there to LV ground. Is that likely to be damaging?
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kiev
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Re: Gen1 DCDC Converter Troubleshooting and Repair

Wed Nov 11, 2020 1:44 pm

That temperature seems reasonable to shut off the DCDC to me. So a reading at 308F makes no sense for this device, and my laser IR thermometer didn't read my cold drink temperature very well. i dipped the thermistor into a glass of tequila on ice, so my reading was more likely at 27F rather than 36F.

i use the continuity beeper on my meter and sharply pointed probe tips (sewing needle sharp) to check traces. The fat-holed double vias are either +5, +15 (TP201) or Gnd, and the tiny-holed double vias are signal lines. i use colored sharpie pens to mark vias after i check them so i can quickly find one that i need during a trace.

The closest double via with the fat holes to the source of the +5V is just to the end of IC201 under some silk screen "C225". Once you find that you can trace down toward the LV section, there is a rectangular section near Q215 that has 4 vias at each end and is a big 5V pad. Then over by IC202 at the end near pin 8 is a double fat via near silk "C236" that should also show continuity to the 5V double via near IC201. If it doesn't then i suspect that a shorting event may have blown the 5V trace on one of the embedded layers between the PWM area and the LV section.

The only way i could recommend to connect a 15V source to back-drive the TP201 supply would be if you used a current-limited adjustable power supply that would protect against a short circuit condition. If all you wanted to do was verify the presence or absence of the 5V supply created from the 15V, that might be feasible with even a 12V supply, but it should still be severely current limited. And that assumes that Q229 on the bottom layer is a good part. A better option might be to just remove the IC209 from the bottom layer and test it separately on the bench.

i measured 3.5k from TP201 to ground also. Q229 is NPN and i measure ~0.6V diode drop from base to emitter and base to collector.
Last edited by kiev on Wed Nov 11, 2020 10:30 pm, edited 1 time in total.
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eldenh
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Re: Gen1 DCDC Converter Troubleshooting and Repair

Wed Nov 11, 2020 5:44 pm

When I got past the coating Q229 checked out OK. The vias showed continuity also. So I don't understand why I was reading 0.28v when I checked the vias when the board was powered up.
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kiev
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Re: Gen1 DCDC Converter Troubleshooting and Repair

Thu Nov 12, 2020 8:43 am

That may have been due to the insulation of the clear coat; one probe was not connected and acted as an antenna to pick up the HV electric field radiation?
Last edited by kiev on Thu Nov 12, 2020 12:31 pm, edited 1 time in total.
kiev = kenny's innovative electric vehicle

eldenh
Posts: 65
Joined: Sat Oct 03, 2015 7:18 pm
Location: Port Angeles, WA

Re: Gen1 DCDC Converter Troubleshooting and Repair

Thu Nov 12, 2020 9:05 am

That seems to be unlikely to me. As I recall, the negative probe was in one of the screw holes of the chassis where it was for other checks and there was no reading until I twisted the positive probe in the vias to make contact on each leg.
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kiev
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Location: The Heart o' Dixie
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Re: Gen1 DCDC Converter Troubleshooting and Repair

Thu Nov 12, 2020 12:49 pm

Maybe check the volt meter function with a known voltage to make sure it wasn't damaged or has a fuse blown. i hope the 5V supply is not damaged.

There are 3 resistor networks on the bottom layer with a 10k, 10k and 12k [R258, 245, 241A] connected directly to that via but if ceramic capacitors C242 or C249 were shorted to ground then either could pull down that pad.
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