extra transistor in level shifter

Tekko · 27th October 2007, 10:14 AM

What does this NPN transistor do in th level shifter ?

In simulation it doesent do a thing.

Pabo · 27th October 2007, 11:26 AM

I think it keeps the LIN input on the driver high during startup which charges the bootstrap capacitor. Will give a large pop noise though so I recommend a relay to the speaker with a few seconds delay.

I am not sure how IRS2011 works but you can try to charge the bootstrap capacitor directly from the positive rail instead with something like 20k or so. Remember to check if the boot strap supply has built in zener protection across it.

Eva · 27th October 2007, 11:30 AM

It forces comparator output low for a brief period of time at power up.

Tekko · 27th October 2007, 11:32 AM

Ah ok.

I´m not gonna use it so i hope the amp starts anyways.

Btw 1N4148 is not usable to charge the bootstrap eh ? I figure BYV26-150 is atleast whats needed, right or wrong ?

27th October 2007, 10:14 AM	#1
Tekko diyAudio Member Join Date: Jan 2005	extra transistor in level shifter What does this NPN transistor do in th level shifter ? In simulation it doesent do a thing. schematic

27th October 2007, 11:26 AM	#2
Pabo diyAudio Member Join Date: Feb 2003 Location: Helsingborg, southern sweden	I think it keeps the LIN input on the driver high during startup which charges the bootstrap capacitor. Will give a large pop noise though so I recommend a relay to the speaker with a few seconds delay. I am not sure how IRS2011 works but you can try to charge the bootstrap capacitor directly from the positive rail instead with something like 20k or so. Remember to check if the boot strap supply has built in zener protection across it. __________________ If something that measures good doesn´t sound good, measure again!

27th October 2007, 11:30 AM	#3
Eva diyAudio Member Join Date: Oct 2003 Location: Near the sea	It forces comparator output low for a brief period of time at power up. __________________ I use to feel like the small child in The Emperor's New Clothes tale

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27th October 2007, 11:32 AM	#4
Tekko diyAudio Member Join Date: Jan 2005	Ah ok. I´m not gonna use it so i hope the amp starts anyways. Btw 1N4148 is not usable to charge the bootstrap eh ? I figure BYV26-150 is atleast whats needed, right or wrong ?

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