Will this mosfetdriver work?

jelle2462 · 11th June 2010, 05:55 PM

Hi,

I am building a class D amplifier as a school project, next monday we should demonstrate our results.
Yesterday I got my amp working for a minute. But then... well, lets say I will be more carefull with my screwdriver in the future

Unfortunatly my IR2011 mosfetdriver died, but luckily my mosfets and Pwm-circuit still worked.
So I needed a new driver-IC. But the delivery will not be for next week

So as a quick solution I tried to design my own driver.
Now, my question is: will this work? Or does someone have an other solution?

Thanks.

81bas · 08:16 PM

No, unfortunately this will not work

You need to implement some level shifter for high side driver, and increase VIN amplitude to 0-10V (instead of 0-5V) to make low side driver working... How do you produce the PWM signal? is it referenced to the ground or to the -VCC (-40V) ?

EDIT: did not seen, that the low side driver is not a totem pole follower... So you need to increase VIN even to 0-12V and you will get huge shot-through currents in the low side driver with such configuration...

Pafi · 11th June 2010, 11:19 PM

Quote:

you will get huge shot-through currents

And smoke in a second.

Baldin · 12th June 2010, 06:41 AM

Take a look at the original UcD circuit, to get an idea of how to make a discrete driver circuit .... I'm afraid it will take much more time than you have available

See here at my home page Micro class-d amplifiers UcD / Hysteresis where you'll find both references and an implementation ...

Go find that IR2011 at some other place with faster delivery ... that is a better option

Workhorse · 12th June 2010, 07:20 AM

Jelle you can use MIC4420 chip as your class-d output stage if your power output is less than 20W and suffices well for your project. Though its a gate driver but it can be used to demonstrate class-d working concept.

jelle2462 · 12th June 2010, 08:24 AM

Thank you for the replies,

I am now searching for a way to just get the PWM amplified with discrete components or a standard chip, just to demonstrate the working principle.
A complicated circuit like the UcD will take to much time to build and test.
The MIC4420 would have been a good solution, when I had a little more time.

Thanks.

Pafi · 12th June 2010, 06:41 PM

If I were you, I would replace upper FET to p-channel, this way it's easier to drive.

jelle2462 · 12th June 2010, 07:06 PM

Thank you Pafi, I didn't think of that

I got something working now (in simulation).
What do you guys think of this?

jelle2462 · 12th June 2010, 07:55 PM

It looks like the pictures don't work?

Imageshack - screenhunterjun12210203.jpg
Imageshack - screenhunterjun12210204.jpg

Pafi · 12th June 2010, 08:34 PM

Just attach your pictures!

Working? What output voltage do you expect from the power stage?

11th June 2010, 08:07 PM	#2
81bas diyAudio Member Join Date: Jan 2006 Location: Kiel	No, unfortunately this will not work You need to implement some level shifter for high side driver, and increase VIN amplitude to 0-10V (instead of 0-5V) to make low side driver working... How do you produce the PWM signal? is it referenced to the ground or to the -VCC (-40V) ? EDIT: did not seen, that the low side driver is not a totem pole follower... So you need to increase VIN even to 0-12V and you will get huge shot-through currents in the low side driver with such configuration... Last edited by 81bas; 11th June 2010 at 08:16 PM.

12th June 2010, 06:41 AM	#4
Baldin diyAudio Member Join Date: Jan 2005 Location: Copenhagen	Take a look at the original UcD circuit, to get an idea of how to make a discrete driver circuit .... I'm afraid it will take much more time than you have available See here at my home page Micro class-d amplifiers UcD / Hysteresis where you'll find both references and an implementation ... Go find that IR2011 at some other place with faster delivery ... that is a better option __________________ Visit www.sensibleaudio.dk or read latest news on Baldin's Blog

12th June 2010, 07:20 AM	#5
Workhorse diyAudio Member Join Date: Dec 2004	Jelle you can use MIC4420 chip as your class-d output stage if your power output is less than 20W and suffices well for your project. Though its a gate driver but it can be used to demonstrate class-d working concept. __________________ It's a fruitless endeavor to try and educate a fool that rejoices in ignorance

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12th June 2010, 08:24 AM	#6
jelle2462 diyAudio Member Join Date: Jun 2009 Location: Belgium	Thank you for the replies, I am now searching for a way to just get the PWM amplified with discrete components or a standard chip, just to demonstrate the working principle. A complicated circuit like the UcD will take to much time to build and test. The MIC4420 would have been a good solution, when I had a little more time. Thanks.

12th June 2010, 06:41 PM	#7
Pafi diyAudio Member Join Date: May 2004 Location: Budapest	If I were you, I would replace upper FET to p-channel, this way it's easier to drive.

12th June 2010, 07:06 PM	#8
jelle2462 diyAudio Member Join Date: Jun 2009 Location: Belgium	Thank you Pafi, I didn't think of that I got something working now (in simulation). What do you guys think of this?

12th June 2010, 07:55 PM	#9
jelle2462 diyAudio Member Join Date: Jun 2009 Location: Belgium	It looks like the pictures don't work? Imageshack - screenhunterjun12210203.jpg Imageshack - screenhunterjun12210204.jpg

12th June 2010, 08:34 PM	#10
Pafi diyAudio Member Join Date: May 2004 Location: Budapest	Just attach your pictures! Working? What output voltage do you expect from the power stage?

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