Gate Drive Transformer Secondary parameters Design

Thread Starter

picstudent

Joined Feb 3, 2009
82
I am trying to do a half bridge like this
HalfBridge3525.jpg
I got a fairly good idea about how to design the primary side of T1. Calculating N minimum for primary and then inductance, magnetizing current and then peak current etc. I got sufficient literature to understand the concept. The secondary I need is 1:1, so obviously I think same number of turns and many articles also describing that ratio, But noting else.
I am curious, how we can make sure that the secondaries can provide enough drive to charge the MOSFET gates and maintain safe voltages there to keep MOSFETs on.
Thanks
 

Thread Starter

picstudent

Joined Feb 3, 2009
82
coilcraft ... More coilcraft
A transformer is not good if the duty cycle is very high or very low. It works well if the design runs 20 to 80%.
Put a scope across R2 and look at the drive.
Watch that the voltage does not get out of range +/-20V. Keep above the gate turn on voltage.
Thank you very much for the information.
My duty cycle is average, so should not be a problem. Being half bridge SG3525 in this mode can only go up-to 50%. Correct?
I was looking for almost the same circuit for Generating high voltage.
R2 I cannot Find in the schematic, I think you are suggesting to measure Gate to Source voltage.
Thanks again
 
R2 I cannot Find in the schematic, I think you are suggesting to measure Gate to Source voltage.
In post #1. G-S voltage.

A transformer can not pass DC. (unless some games are played)
Watch out for what happens at min and max duty cycle. I am not talking about the duty cycle of the IC but of the signal on the transformer. The middle picture if of 50:50.
1596394186291.png
 
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