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Old 13th September 2012, 02:14 PM   #2531
Pafi is offline Pafi  Hungary
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Quote:
Originally Posted by manojtm View Post
Hi Pafi

how you say that 400/200 ns . picture shows 12.14ns (1st picture at the mosfet gate)

Hi paskal9,

did you use NE5534 instead of TLO71

Regards
Manoj
I don't know what is Z2, but I doubt it was the dead time.

The high side gate voltage is added to the output voltage! I indicated actual turn on and off transitions on this picture.
irs90010.jpg

...

Measurements shoud have been made referenced to negative supply, as close to lower mosfet source (or IR2110 GND) as possible. With NOT grounded oscilloscope, of course! Probe grounding lead should be as short as possible.

Last edited by Pafi; 13th September 2012 at 02:17 PM.
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Old 13th September 2012, 02:21 PM   #2532
CPX is offline CPX  Romania
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Quote:
Originally Posted by paskal9 View Post
i don't. though i could try and ask around for it. issit important to have one?
Yes,because you have connected oscilloscope ground to switching bus..Upper mosfet waveforms are not valid without isolated probes.
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Old 13th September 2012, 02:49 PM   #2533
paskal9 is offline paskal9  Malaysia
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Quote:
Originally Posted by manojtm View Post
Hi Pafi

how you say that 400/200 ns . picture shows 12.14ns (1st picture at the mosfet gate)

Hi paskal9,

did you use NE5534 instead of TLO71

Regards
Manoj
no i didn't try any NE5534. don't even have any in my parts bin.

Quote:
Originally Posted by Pafi View Post
I don't know what is Z2, but I doubt it was the dead time.

The high side gate voltage is added to the output voltage! I indicated actual turn on and off transitions on this picture.
Attachment 301148
...

Measurements shoud have been made referenced to negative supply, as close to lower mosfet source (or IR2110 GND) as possible. With NOT grounded oscilloscope, of course! Probe grounding lead should be as short as possible.
tq for the clarification. i was wondering why the high side signal is higher than the low side all this while. Z2 is a previous function that i've since removed.

i'll try and scout around for any isolated probes. but slim chances that i'll be able to borrow one.

Quote:
Originally Posted by CPX View Post
Yes,because you have connected oscilloscope ground to switching bus..Upper mosfet waveforms are not valid without isolated probes.
but from the measurement done i think it's apparent that the dead time could be reduced. any idea on how to optimize the dead time for the design?
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Old 13th September 2012, 03:18 PM   #2534
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Originally Posted by paskal9 View Post
From the measurement done i think it's apparent that the dead time could be reduced. any idea on how to optimize the dead time for the design?
Show point B with 25 us time div to see deadtime before ir2110.
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Old 13th September 2012, 03:41 PM   #2535
paskal9 is offline paskal9  Malaysia
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Quote:
Originally Posted by CPX View Post
Show point B with 25 us time div to see deadtime before ir2110.
i was afraid someone would say that. i guess that means the dead time are directly affected by the propagation delay time and transition time of the inverter, right?

Click the image to open in full size.
so there's no easy way to change the dead time other than playing around with the VDD and VIN, right?
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Old 13th September 2012, 04:11 PM   #2536
Pafi is offline Pafi  Hungary
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Quote:
Originally Posted by paskal9 View Post
i was afraid someone would say that. i guess that means the dead time are directly affected by the propagation delay time and transition time of the inverter, right?

Click the image to open in full size.
so there's no easy way to change the dead time other than playing around with the VDD and VIN, right?
Unfortunately CD4049 is not an ideal comparator, it has a quite low gain (transfer characteristic is not square), this means when it is fed by a slew rate limited signal, then the delay is more, and depends on the slew rate. Measure A also at low time/div! (2 us/div, during normal operation!)

2 more stages of inverter can fasten the transition, and then you have to set a dead time somehow else. CD4049 output current is very asymmetrical, this is a chance to make asymmetric delay = dead time. But first you have to make a correct square!
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Old 14th September 2012, 05:51 AM   #2537
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Hi paskal9,

For any MOSFET switching(conduct) min. volt is 2.5v/3v.below this MOSFET will not conduct. IR2110(logic 5v & VCC 12V supply) high side point it should be 5v with respect to GND and LOW side 5V with respect to -HV supply.The junction point @10V-14V pp signal with respect to GND.For UCD design you need propagation delay @100ns otherwise
the system will not oscillate.

Regards
MANOJ
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Old 14th September 2012, 02:32 PM   #2538
Pafi is offline Pafi  Hungary
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A way to achieve faster transition is to provide more gain at level shifter. Use lower emitter resistance + z-diode to maintain operation point! A current generator (with j-FET) can be useful to limit max current.
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Old 17th September 2012, 09:39 AM   #2539
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TC4420,3 pairs 90n20 please review all diyer's for correction,thank's.
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Old 17th September 2012, 10:05 AM   #2540
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Hi Don2007ksa
Greetings. Is amplifier working with TC4420? Have you tried?
it out
warm regards
andrew lebon
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[image][/image]"It's Better to try and fail than to never know and always wonder"
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