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Old 27th April 2010, 08:46 PM   #1
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Default Using a synchronous buck converter driver for class D?

Okay here's a quick one. I just pulled a bunch of those from a motherboard. I noticed that they have low and high-side drivers with cross conduction protection. So, my question is, can they be possibly used for gate drivers in a class D design?

I can't get IR series drivers around here so don't ask. If those things i pointed above won't work, i'll have to go discrete.
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Old 27th April 2010, 09:19 PM   #2
Eva is offline Eva  Spain
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This driver IC can only whitstand 35V from BST to PGND. This limits class D supply voltage to 25V with 10V gate supply. It's ok for experimentation, but power output isn't going to be high. Logic level MOSFET may allow for 30V main supply and 5V gate supply.
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Old 27th April 2010, 09:28 PM   #3
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25 volts you say. Bummer, i was thinking more of +/-30 volts. But 25v is still 300 watts on a 2 ohm load (edit: it's 150 watts, i tend to forget that in dc peak=rms while in ac it's not), it wouldn't make a bad woofer amp. I can get logic level mosfets, i'll see if there are any available with a decent rdson, choices are somewhat limited. Oh wait... those 'fets on the motherboard can take 30 volts and are logic level. Guess my next topic title will be "how to turn a junked motherboard into an amplifier".

Anyway this will be my first class D project so if it reaches anywhere near 100W it's fine.

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Old 28th April 2010, 10:52 AM   #4
AP2 is offline AP2  Italy
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Originally Posted by Th3 uN1Qu3 View Post
25 volts you say. Bummer, i was thinking more of +/-30 volts. But 25v is still 300 watts on a 2 ohm load (edit: it's 150 watts, i tend to forget that in dc peak=rms while in ac it's not), it wouldn't make a bad woofer amp. I can get logic level mosfets, i'll see if there are any available with a decent rdson, choices are somewhat limited. Oh wait... those 'fets on the motherboard can take 30 volts and are logic level. Guess my next topic title will be "how to turn a junked motherboard into an amplifier".

Anyway this will be my first class D project so if it reaches anywhere near 100W it's fine.
Hi,
Also not suitable for audio because DT-on / DT-off (see fig.3) is a fixed digital DT. Can not adj from external R/D gate. this produce thd, especially with very low load.
This DT mode is usefull and good for power supply only.
Regards
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Old 28th April 2010, 02:45 PM   #5
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Well, the fixed dead time would help in keeping the smoke inside of the FETs. But since my power supply is 30-0-30v i might as well do something more interesting.

Could you please tell me the basic building blocks of a discrete class D design? I can figure out how to assemble them by myself. I already have a PWM controller with feedback and everything. But what eludes me is how to actually convince the PWM to drive only one fet at a time. I saw something about inverting schmitt triggers and a NAND gate... I happen to have such chips on hand but i can't figure out what to do with them.
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Old 28th April 2010, 03:45 PM   #6
AP2 is offline AP2  Italy
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Hi,
What is "PWM" with feedback? Let me see.
you have IR2110? it is simple way to realize first scheme.
or want to do with discrete drivers?
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Old 28th April 2010, 04:07 PM   #7
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Hi,
You can get info from input to out HFE4070, from this scheme.

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Old 28th April 2010, 09:02 PM   #8
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The PWM controller being a TL494, i read here that someone used it class D and it ended up okay. He used an IR driver however and i can't get one. So i would like to do it with discrete drivers.

I'm not that convinced on class D anyway, but i'd like to try to make a class D amp just for fun. In the long run, i want to find out whether the efficiency of class D is worth the design effort. I'm looking for 300-500W power and be it class D or class AB the amp will be powered by a switchmode supply, so is the size/weight reduction worth it? Maybe i should first build more class AB amps then make my decision.

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Old 29th April 2010, 07:29 PM   #9
savu is offline savu  Romania
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Quote:
Originally Posted by Th3 uN1Qu3 View Post
Okay here's a quick one. I just pulled a bunch of those from a motherboard. I noticed that they have low and high-side drivers with cross conduction protection. So, my question is, can they be possibly used for gate drivers in a class D design?

I can't get IR series drivers around here so don't ask. If those things i pointed above won't work, i'll have to go discrete.
try www.tme.eu\ro or ro.farnell.com/ and you will find almost anithing you want. especialy goodies from IR.

best regards,

Savu Silviu
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Old 4th May 2010, 08:20 PM   #10
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20 roni transportul? In cat timp vine? Mi se pare destul de ok. (Cheap shipping, looks good, how long does it take to arrive?)
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