Arlo1 said:
HighHopes said:
most caps for digital or analog application, including low voltage bulk storage = X7R
timing circuits = C0G
Power = MKP, metalized film, poly etc.
Thank you.
It was my misunderstanding. I read what you said as not to use the X7R Caps. But you were pointing out for the High voltage rails which I have the 1 big cap from the leaf which I believe is a multi cap in one housing.
Thanks again for all your help.
Wouldn't say "just the ACPL-333J" with 2A be consider a power stage, then the booster with 8A .... so you could say MKP would be better suited for this rail support role. But for less than 25V rating they aren't stabilizing much power.
Just to highlight HighHopes comments..
Digital and Analogue need stable capacitance ....
Timing need accurate capacitance over voltage range and temp range ...
power rails needs bulky capacitance at RAIL set to say 70% of max voltage over 25V with low esr over temp range
thanks Zombies for pointing out the phase to phase issue Arlin was getting at.
I was thinking just about the Driver Power requirement.
Center-Aligned PWM (CAPwm) is very handy ...
The CAPwm helps the big HV Cap as well spreading the Switching points across the Period instead of the one edge.
As their is continuous currents flowing in each phase wire at all times, there will be more gradual changes to the current curves dI/dt shapes.
With all three phases with CAPwm, the Ripple will have a "Spread Spectrum" as the intervals between edges (Rise or Fall) will be varying all the time.
So putting the phase current through the FFT on the Scope and won't show a definite 40kHz it will result in a time averaged hump starting at 20kHz peaking above 40kHz perhaps above 60kHz.
With the three interacting you can't say 60kHz either.
.... I'm just guessing ... trying to think it through .... real tests would be golden.
Zombies your test of your Booster stage D45VH10/D44VH10 TO-220's is a bit hard to relate.
I wonder what you had as the Gate resistor ON and OFF, was it 20 on and 20//20 = 10 for OFF
Plus a bit extra current from the 40ohm to the driver chip.
With no pcb circuit inductance peak current for 20ohm is 15/20 = 0.75A
With circuit inductance considered it would be peak lower later.
Where you just using the 0.104ohm current sense resistor. And no Larger Gate Resistor for the test into the 1uF Cap.
Also
C = q/V so your 1uF at 15V holds ... q = C. V = 15 * 1u = 15 uC or 15 000 nC
your 3 x IRFP4568 are just 3 x 170 nC = 510 nC at 12V so around 600 nC for 0V to 15V.
and the FUJI big block is around 5000 nC for -9V to 15V
So the 1uF is massive ... and the ESR would look very different.
So the On/OFF times will be quite long... for a known resistance etc
I did do a bit of a hunt through your thread a few days ago to see tests on the driver board but missed these pic's ... are they in your thread zombies??
Then you posted the goodies ...
I think I'll post to your thread as this a bit off topic as the test confuses what Arlin needs.
See >>>
http://endless-sphere.com/forums/viewtopic.php?p=960867#p960867
On the Zener issue ..
The Vz for the I_ZT needs to have I_ZT less than 250uA but the specs sheet only shows graphs like HighHopes points out.
From the Zeners you have linked COMCHIP, ON-SEMI and DIODES INC.
The COMCHIP has a nice range shown in figure 7. with more stable looking Vz near 0.250 mA.
All the brands of zeners have negative mV/degC for zeners with Vz less than 5V which would be good to compensate a MOSFET but IGBT needs positve to compensate for its negative Vce change for temp.
Also MOSFETs need a larger zener like 5V6 if the DESAT point is lower... but not always... for some the Rds may push Vds over 3V.
ON-SEMI figure 9 only shows small selection of the devices (without naming them), so with some missing it's shows how hard it is to pick a device from the spec sheet.
Same with DIODES INC. many missing from Fig 4 (and Fig 3) but they identify them.
But from the curves to get 2.5V at 250uA you may need to select a 2V7 COMCHIP zener CZRU52C2V7
Maybe 3 series diodes would be more accurate for 250uA and have a positive temp co-efficient.
Have you picked the blocking diode?
Regarding the Pull-Down Resistors shown in the 333J SPEC may be there to divert leakage current from the Booster Stage Transistors.
- So they placed it straight after them.
- If the 333J Vout failed and the coomon base point was floating their circuit with only one ON/OFF Rg may float high.
so you want the Gate to turn off under all failures. So pull it to Neg Rail AND/OR/BOTH the Emitter.
And end up with two forming a Divider to the neg rail.
It gets crazy thinking about too many options.... my heads in seven circles ... :lol:
Do you plan to fit the IGBT block to the chill-plate soon. Or at least make sure it will all fit okay with out holes passing through to the liquid layer if it is too thin. or have to add intermediate base-plate???
