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Old 3rd May 2009, 11:51 AM   #11
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To thread starter,


Go and learn some basics first, you need to learn alot to get the things done in right manner.
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Old 3rd May 2009, 12:37 PM   #12
7ormore is offline 7ormore  United States
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Quote:
Originally posted by Pafi


This doesn't tell anyting. OK, by the cadet board, but how? COM (and VSS) of the IR2113 should be connected directly to the source of the lower MOSFET!

I repeat: What do you expect from this circuit? What is this supposed to be? It's usable for testing the functionality of the IR chip, but nothing else.

Try to think it over what signal do you want on the load, and for that what is the appropriate switching topology (yours is good for nothing), and for that what are the neccessary gate-signals!

For this circuit i am trying to build a class-D amplifier, right now though i am just trying to make sure i have the IR working properly, what i want to show by the end of the semester is a half H-bridge amplifying the input sine wave. I realize i need to design a filter for it too. I would do a full H bridge but i'm running out of time.

Thanks
Brian
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Old 3rd May 2009, 12:55 PM   #13
7ormore is offline 7ormore  United States
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Quote:
Originally posted by Workhorse
To thread starter,


Go and learn some basics first, you need to learn alot to get the things done in right manner.

Sorry i have been researching this quite a bit and i also built a scematic of the class-d which worked very well in P-sim, however i'm running out of time and have to present something soon.
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Old 3rd May 2009, 02:13 PM   #14
7ormore is offline 7ormore  United States
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That was the problem i didn't tie vss and com to the source on the low mosfet now it works great.

Thanks for the help
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Old 3rd May 2009, 02:36 PM   #15
7ormore is offline 7ormore  United States
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I guess i spoke to soon the problem i'm having is with the high output the amplitude is correct but the frequency is only at 44kHz when it should be a 298KHz. The good news is that the low is correct and the mosfets are amplifying the signal. I will be working all day on this to try and figure it out.

Thanks
Brian
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Old 3rd May 2009, 10:34 PM   #16
7ormore is offline 7ormore  United States
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http://i607.photobucket.com/albums/t...d/class-d4.jpg

This is an update of what has changed in my design. I now have good outputs for HO and LO for IR2113. LO outputs from 0-20V and the HO output is from 0-20 of the inverted signal. I'm worried about gate delay and if my LC filter will work.

Thanks to everyone for the help
Brian
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Old 4th May 2009, 07:05 AM   #17
Eva is offline Eva  Spain
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All people who have replied to you in this thread have our own working amplifier designs.

If you continue ignoring our advice you are not going anywhere.

The schematic contains almost the same mistakes: No level shifting, not caring about timing on HIN/LIN splitting, +/-15V fed to HIN and LIN, etc.. Not even related to class D, just to basic electronics...
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Old 4th May 2009, 12:45 PM   #18
7ormore is offline 7ormore  United States
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I'm sorry if i came off as not caring about level shifting and delay caused by the op amps i deffinitly do care about that. I was debating on replacing the two op-amps with the IC TL494CN it seems to do the job of both the op-amps with out the problem of level shifting and the gates delay. The only reason i'm currently using this design is because this is the layout my advisor suggested to use.

I do appeaciate all the help

Thanks
Brian
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Old 4th May 2009, 06:01 PM   #19
Eva is offline Eva  Spain
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You will find that TL494 does not suit your needs well.

LM311 is ok as a comparator. Note that there are other common comparator ICs with faster response like LM319 or TL3016 (to name two that I have used).

For level shifting, which means to change the ground referenced logic output from the comparator to the negative rail referenced logic signals needed by the IR2113, the simplest solution is to use a PNP transistor in common-base configuration (fed an emitter current and you will get an almost equal collector current with very fast response). You can use a fast optocoupler like 6N136 too.

Then you must use 74HC fast logic gates (or a fast transistor circuit, but this is not recommended) to generate the complimentary HIN and LIN signals so that the delay between them is only a few nanoseconds and they don't overlap in the high state (otherwise the circuit would self destruct). An op-amp may take several microseconds to respond when used as a logic inverter, which is absolutely not acceptable.

If you advisor told you to use an op-amp as a logic inverter, you should not trust him much... This is a really big mistake.
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Old 4th May 2009, 06:01 PM   #20
Eva is offline Eva  Spain
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You will find that TL494 does not suit your needs well.

LM311 is ok as a comparator. Note that there are other common comparator ICs with faster response like LM319 or TL3016 (to name two that I have used).

For level shifting, which means to change the ground referenced logic output from the comparator to the negative rail referenced logic signals needed by the IR2113, the simplest solution is to use a PNP transistor in common-base configuration (fed an emitter current and you will get an almost equal collector current with very fast response). You can use a fast logic optocoupler like 6N137 too.

Then you must use 74HC (or similar) fast logic gates (or a fast transistor circuit, but this is not recommended) to generate the complimentary HIN and LIN signals so that the delay between them is only a few nanoseconds and they don't overlap in the high state (otherwise the circuit would self destruct). An op-amp may take several microseconds to respond when used as a logic inverter, which is absolutely not acceptable.

If you advisor told you to use an op-amp as a logic inverter, you should not trust him much... This is a really big mistake.
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