DEAD TIME CALCULATION FOR RECTIFIER SWITCH IN BUCK CONVERTER HAVING SYNCHRONAS RECTIFICATION

Thread Starter

mohtishamali

Joined Jul 9, 2021
18
Hello all,

i am working on 48v to 12v dc dc converter /buck and i want to ask how can we find delay time for rectification switch while generating PWM with respect to control switch in simple buck topology using GAN HEMTS.
Thanks
 

ronsimpson

Joined Oct 7, 2019
1,996
A GaN is fast. If the transistor switches in 5 to 10nS then you need to turn on the "diode" 10nS after the transistor turns off.
Then 10nS before you turn the transistor on the diode needs to be off.
Have you seen synchronas rectification using HEMT?
 

Thread Starter

mohtishamali

Joined Jul 9, 2021
18
A GaN is fast. If the transistor switches in 5 to 10nS then you need to turn on the "diode" 10nS after the transistor turns off.
Then 10nS before you turn the transistor on the diode needs to be off.
Have you seen synchronas rectification using HEMT?
I am not using diode as rectifying switch. I am using a GAN HEMT for main Control switch as well as a GAN HEMT for synchronous rectification in a simple buck converter. while generating PWM for Synchronas Rectifier Switch i am unable to understand what would be the best possible dead time for smooth transition
 

ronsimpson

Joined Oct 7, 2019
1,996
I understand what you are doing.
The dead time must be longer than the switching time. (the time to turn on or off)
If you do not know what the switching time, make the dead time long and see what happens. Measure the time for the voltage to go from 48V to 0V. (small load and heavy load) Then add 1.5 more time.
 
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