The RD's on the gates are pretty standard. The "Xtra" deadtime is a lot easy'ere to trim to get very short deadtime.
Totem-pole? Please explain?
In the sim the freq is approx 250kz, but that is a function of the delay in the inverters and therefore the freq in the real-world sch could be a lot different.
I´m using PSpice.
TroelsM
Totem-pole? Please explain?
In the sim the freq is approx 250kz, but that is a function of the delay in the inverters and therefore the freq in the real-world sch could be a lot different.
I´m using PSpice.
TroelsM
Hi,
The totem pole i'm referring to is Q1/Q3 and Q4/Q5. They are arranged in a configuration known as 'totem-pole'. It is a standard way of driving at low frequencys and works well but i've never seen one working above 100KHz, the low switching times and crow bar current will cause havock. Talking of speed if you want more you will find changing the gates for TTL instead of Cmos will speed things up, the waveform of TTL gates are much sharper as well. Unfortunatly you must use them at a max of 5V, this complicates things a little.
Have fun,
Mad.P
Years ago everybody thought that even the tiniest bit of ripple had to be "ironed out" in order to reach audio nirvana.
Only within the last 10 years there was a paradigm change in that reasonable amaounts of ripple aren't regarded as disturbing as a filter of high order itself.
Regards
Charles
Greet's
I don't know if anyone has ever written a paper about the pro's and con's of totem pole drivers, I'm sure somewere somebody has LOL. I'm just going off my own experience in trying to use them in these kinds of amps. Alos i have not seen any practical designs that use them, pity really as they are so simple
Mad.P
I don't know if anyone has ever written a paper about the pro's and con's of totem pole drivers, I'm sure somewere somebody has LOL. I'm just going off my own experience in trying to use them in these kinds of amps. Alos i have not seen any practical designs that use them, pity really as they are so simple
Mad.P
Nitrate: What kind of problems are you referring to? If you could explain which transistors you have used and what the problems were maybe we could find and/or solve some of the problems?
I'm guessing that a lot of discrete drivers have failed because of very poor PCB-layouts with dozen of nH trace-inductance and slow transistors.
Kenshin: No, you're absolutely right. I´m going to use a separate 40106 for the highside. The Sch is only a sim-model. Some of the inverters might not be used and I hav'nt figured out how many 40106 I'll need in total.
I would like some more input on the post-filter-feedback but maybe I'll build the powerstage and examine the switching of the driver and Mosfet. If those parts are working well then I guess that a LOT of people will be very interested in the design.
TroelsM
I'm guessing that a lot of discrete drivers have failed because of very poor PCB-layouts with dozen of nH trace-inductance and slow transistors.
Kenshin: No, you're absolutely right. I´m going to use a separate 40106 for the highside. The Sch is only a sim-model. Some of the inverters might not be used and I hav'nt figured out how many 40106 I'll need in total.
I would like some more input on the post-filter-feedback but maybe I'll build the powerstage and examine the switching of the driver and Mosfet. If those parts are working well then I guess that a LOT of people will be very interested in the design.
TroelsM
Better driver-curcuit
I Have siulated the performance of the totempole-driver but i cant find any serious faults with it. I tried to ad a lot of parasitic inductance but it only made things a wee bit worse.
-But anyhow i decided to try another driver-curcuit in the simulator. Two different schematics are added to this post. The top-schem is a little faster at turn-on because off the "kick/boost" from the C1, R2-connection around Q2. The timeconstant is so small that C1/R2 are only conducting the first 100nS of the switching action but the give a good kick to turn Q1 on faster.
C1/R2 does the "AC" switching and Q2 does the DC-switching...?
Both Curcuits seems to work fine, but they will be harder to implement with leaded components as there are more componets in the critical loop driving the gate.
Comments? Ideas?
Sim-results will be in the next post.
TroelsM
I Have siulated the performance of the totempole-driver but i cant find any serious faults with it. I tried to ad a lot of parasitic inductance but it only made things a wee bit worse.
-But anyhow i decided to try another driver-curcuit in the simulator. Two different schematics are added to this post. The top-schem is a little faster at turn-on because off the "kick/boost" from the C1, R2-connection around Q2. The timeconstant is so small that C1/R2 are only conducting the first 100nS of the switching action but the give a good kick to turn Q1 on faster.
C1/R2 does the "AC" switching and Q2 does the DC-switching...?
Both Curcuits seems to work fine, but they will be harder to implement with leaded components as there are more componets in the critical loop driving the gate.
Comments? Ideas?
Sim-results will be in the next post.
TroelsM
Attachments
Sim-Res.
Here's the sim-results. The sim's are done without any parasitic/PCB-inductance.
M1 are clearly turned on faster and the loss (area under curve) is therefore smaller. Not a big difference but it's there.
The inverters in the sch might have to be made up off 2-4 inverters in parralel.
TroelsM
EDIT: just tried the totempole-driver from my original-schematic. It gives the same switch-times and losses as the best of the two "new ones". The Totem-pole is, as i mentioned before, a lot simpler to implement though.
I would like to try both in the real world, but I´m not shure when I'll get near a scope' again..
TroelsM
Here's the sim-results. The sim's are done without any parasitic/PCB-inductance.
M1 are clearly turned on faster and the loss (area under curve) is therefore smaller. Not a big difference but it's there.
The inverters in the sch might have to be made up off 2-4 inverters in parralel.
TroelsM
EDIT: just tried the totempole-driver from my original-schematic. It gives the same switch-times and losses as the best of the two "new ones". The Totem-pole is, as i mentioned before, a lot simpler to implement though.
I would like to try both in the real world, but I´m not shure when I'll get near a scope' again..
TroelsM
Attachments
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