Prius Gen 3 DC-BUS1 voltage measurement

[bexander]

After doing tests with the charger software for the Prius Gen3 buck-boost I relized that the dc-bus1 voltage measurement doesn't move, it is solid at 375V. This ain't right. After some reverse math from the SW voltage per bit and the voltage division on the logic board, thats in the range of 4,5V output from the dc-bus1 voltage sens signal from the gate-driver board. This signal, using the same math, is 0,5V when the voltage is 0V so not completely unreasonable that max voltage is 4,5V.
Since the Prius uses nominal battery voltage of 202V and a fully charged voltage in the range of 252V, it does seem reasonable that the max measurable voltage is in the range of 350V or so.
In some Lexus:es the voltage is nominal 277V and fully charged 345V so, again, resonable with a measuring max voltage of 350V.

I'm using a 96S Li battery pack so I want to measure up to 405V.

I have started to reverse engineer Toyota:s voltage measurement, using my Yaris inverter. After alot of measurements, this is my best guess.
NOTE: I can't find any solid prof for the use of an quad op-amp but the components and connections to it seem resonable. Also, some of the resistor values are measured with all components in place, so could be wrong.

Values in parantesis is for the dc-bus2 measurement

The circuit seem to be the same for both dc-bus1 and dc-bus2 measurement with adjustments to resistor values. Looks resonable to me.

[bexander]

The matrh further supports my guess...
If the dc-bus1 (battery) voltage is 360V, the input to each half of the input is 180V.
The gain for a inverting op-amp is -Rf/Rin => 180V * -15k / 8,2M = -0,33V and -180V * -15k / 8,2M = 0,33V
The output voltage for a differentail amplifier is Rf/R1(V2-V1) => 82k / 12k * (0,33V - -0,33V) = 4,5V

One question is why the output voltage is limited to 4,5V? The supply voltage to the IC is +12V and -5V.
Why is the output voltage 0,5V when the dc-bus1 voltage is 0V? The dc-bus2 measurement does not seem to have this?
And the last op-amp, is that only a filter? I have not yet found any reasonble explanation for this. Maybe some elegant LP-filter?
Any ideas?

[mjc506]

The +0.5/+4.5V might be an open/closed circuit detection?

[bexander]

Ok, so the Yaris and the Prius Gen3 look alot different when it comes to the voltage measurement.
Pulled my Prius inverter of the car, to find out that many of the components are on the underside of the IGBT-driver board, specially the dc-bus1 measurement.

Does anyone have detailed pictures on the underside of the Prius Gen3 IGBT-driver board??
I'm not very happy to desolder all 90 joints to the IGBT:s just to have a look...

[Bigpie]

This is a Gen 3 board, happy to send it to you if it's of any use.

[bexander]

Excellent, thank you Bigpie!
If it is possible, the area I marked in red in these two pictures, could you take one picture of it? Please, use more light making the picture clearer so I can read the component values more easily.

I appreciate your offer about sending the board! Hopefully the pictures will suffice.

[Bigpie]

Hopefully I've got the area you're interested in.

[bexander]

Great!! Thank you very much Bigpie!!

[bexander]

Thanks to the pictures from Bigpie I could find out that the input side is very similar to the Yaris one.
8Mohm in series and 15kohm in the feedback. So I decided to test and reduce the feedback to 12kohm for a bit lower signal, hence larger measuring range. This could be done adding a few resistors.

Will share more details about this when tested and verified.

[bexander]

Realized that the components needed to be changed are all on the top side of the board so I removed the paralleling resistors and replaced the resistors I wanted to have new values.

The resistors in red circles are now 12kohm, was 15kohm, and the resistor in blue circle are now 6,2kohm, was 7,5kohm.
I also have removed R90 (10kohm) from the logic board. The 328p can handle 5V input to the ADC so no need to dampen the signal with a voltage division.

After a new voltage measurement calibration in the SW I now have a voltage measurement capable of measuring up to 450V.
At this point not much tested but will report back if I find any errors.

[arber333]

I remember i wrestled with Auris inverter some time ago. Here are results on the voltage functions for both sides. Might help you some...
viewtopic.php?p=2933#p2933