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Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Eric, if you look at the simulation, the amount of phase lead is always the same. It's just that the comparator doesn't switch exactly at the zero crossings of the phase-lead waveform. It needs a small positive voltage before it trips.
At low currents, that small voltage corresponds to a long time delay, because the rate of change of the current is proportional to the amplitude of it.
The offset in the switching voltage might be caused by some sort of initial DC voltage on a coupling capacitor, that builds up during the off-time between bursts.
Registered Member #7267
Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407
C5 - 100nF not on the BOM lol (okay seriously I swear this is the last time I'll bug you haha). steve's original BOM shows C5 under the .1uF 50V category with quantity of 13. Also noticed from the get-go that SV1 was not on the BOM but I had just assumed to use the headers for that, figured that was intentional in case you wanted to add that in there too
Edit: any reason why I can't change C10 to better match the frequency of my system, or does it have to be the resistor? is it necessary to change the time constant at all? My design frequency is going to be somewhere around 50-60kHz
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
Steve:
I agree with your logic, this makes sense why switching to the lower voltage drop diodes improved the first cycle ringing. If I was to eliminate it completely I may have to implement some circuit that changes the chopper reference voltage on the first cycle only. However not sure if it's worth the extra complexity when it's not really doing any harm.
Physics Junkie: As you may have gathered I didn't spend much time on the BOM hehe! I should have just redone the BOM from scratch, oh well...
Also should be no need to change C10, it's not a PW limiter and that RC is good from 30Khz up to 500Khz as tested during my bench test.
I updated the schematic and BOM, I recommend using the new diodes for D1 and D2. Same diodes used for the OCD rectifier, they seem to work much better due to their lower voltage drop. They help to reduce the first cycle ringing.
Registered Member #7267
Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407
I'm not sure if this is an issue or not since this is my first time using the UD. I'm getting a constant 5V through D13. By the way, im only using the Optek 2412T. I dont even have the Inudstrial Fiber Optic installed. So the 5V makes its way from the regulator to R11 and then through the inverter twice, and out of pin 5 of the inverter I get 5V which makes it way through D13. I'm wondering if this is an issue or not because now I have 5V continuous imposed on my interrupter signal whenever I turn it on. So when the interrupter is on it just looks like 5V DC with very tiny square waves of like 100mv or less. signal LED is also always lit bright because of this (whereas on my other controllers its always off or really dim until a signal is present). I'm checking the components now but I thought I'd ask about it. It makes me think that this would cause CW operation. You mention on your website to always leave R11 installed for noise immunity but Could I just leave out D13 since i'm not using the Industrial Fiber Optic style and eliminate that 5V that's making it's way through from the inverter?
Edit: I checked the diodes and resistors and they are all good.
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
Yes you would need to remove D13 if you don't have the Industrial fiber optics RX unit installed. By leaving R11 in place you prevent the 74HC14 from switching on noise and such. However you are correct in that D13 needs to be removed if you don't plan to have the fiber unit installed.
That was tricky design decision to make for me because by having R11 as a pull up it allows the use of the open collector type units (IFD95C) and the push-pull units (IFD95T), but because they are active high if you don't have it installed it won't pull the interrupter line low.
Registered Member #7267
Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407
Cool, thanks! Do you experience any heating on the 9V regulator? I heatsink all three regardless but without heatsink the 9V tends to get hot. Might just be a solder short somewhere on my part...
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
Yes the 9V reg gets warm. Originally the 5V got hotter than hell because it was dropping 30V down to 5V now I have the 5V series with the 9V so the 5V stays cool however the 9V still has to drop 30V down to 9V and as a result can a bit warm. Granted it's not as hot as the 5V used to be. I may on the next rev series the 9V with the 24V.
However if they are heatsinked none of them should get above ambient. That's partly why I rotated the Vregs 90 degrees so they can be sinked to the metal box you install the UD in.
Registered Member #205
Joined: Sat Feb 18 2006, 11:59AM
Location: Skørping, Denmark
Posts: 741
Goodchild wrote ...
In simulation it looks to me like the voltage out of the phase lead network has significantly less phase lead than then when it's at a higher input current. Consequently it doesn't even look like you get any lead until the second half cycle. After the first half cycle the amount of lead doesn't seem to change much with input current, it stays rather constant.
I'm not supper worried about the first cycle ringing, I have lived with it sense I started using phase lead. I'm just a little OCD about electronics, and if I can make it perfect I must try!
Eric,
That simulation is consistent with what I saw when I initially pioneered the phase lead circuit, and it does indeed seem as if the current monitor doesn´t produce any lead before the first reversal. All my Predictors did this.
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Universal DRSSTC Driver V2.5 (Sold Out)
