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Raj08
Level 2
Level 2
First like received 5 replies posted First solution authored

Hello, 

I am trying to study the 1k6W PSU Link .
I am unable to understand the connections of Oring MOSFET gate driver (secondary side), specifically  "VCC2" and "GND2"

The VCC2 pin is connected to 12V flyback auxiliary net "Oring VDD2" and the net "Oring VDD" of LLC transformer through a Schottky diode and the GND2 pin is connected to net "12Voring".

First of all, I want to know, what is the need for diodes "D8" and "D17"? Please clarify.

Also, kindly specify why an isolated gate driver 1EDI20N12AF is required for Oring MOSFETs, whereas a non-isolated gate-driver 2EDN7524F is used for Synchronous MOSFETs.

Please find the reference image attached.

Regards,

 

 

 

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1 Solution
Abhilash_P
Moderator
Moderator
Moderator
50 likes received 500 replies posted 250 solutions authored

Hi,

  Thank you for posting on the Infineon community.

1. First of all, I want to know, what is the need for diodes "D8" and "D17"? Please clarify.

Soln: D17 and D8 allow you to generate the required floating voltage once the LLC has started to switch using the transformer voltage. Before that, the voltage comes from the flyback transformer, via the top 9 turns. 
Before the LLC gets pulses, the supply of the driver (OringVDD2 - 12Voring) comes from the flyback (9 turns). After the LLC starts switching and there is voltage in the main transformer, the supply comes from D17 instead of D19 (flyback diode)

2.  Also, kindly specify why an isolated gate driver 1EDI20N12AF is required for Oring MOSFETs, whereas a non-isolated gate-driver 2EDN7524F is used for Synchronous MOSFETs.

Soln: Since the gate driver 1EDI20N12AF  has its input from the primary side of the transformer, (3V3, which is stepped down using a buck converter IC6), an isolated gate driver is required. 

Please let me know if you have any further questions.

Regards,
Abhilash P

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2 Replies
Abhilash_P
Moderator
Moderator
Moderator
50 likes received 500 replies posted 250 solutions authored

Hi,

  Thank you for posting on the Infineon community.

1. First of all, I want to know, what is the need for diodes "D8" and "D17"? Please clarify.

Soln: D17 and D8 allow you to generate the required floating voltage once the LLC has started to switch using the transformer voltage. Before that, the voltage comes from the flyback transformer, via the top 9 turns. 
Before the LLC gets pulses, the supply of the driver (OringVDD2 - 12Voring) comes from the flyback (9 turns). After the LLC starts switching and there is voltage in the main transformer, the supply comes from D17 instead of D19 (flyback diode)

2.  Also, kindly specify why an isolated gate driver 1EDI20N12AF is required for Oring MOSFETs, whereas a non-isolated gate-driver 2EDN7524F is used for Synchronous MOSFETs.

Soln: Since the gate driver 1EDI20N12AF  has its input from the primary side of the transformer, (3V3, which is stepped down using a buck converter IC6), an isolated gate driver is required. 

Please let me know if you have any further questions.

Regards,
Abhilash P

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Raj08
Level 2
Level 2
First like received 5 replies posted First solution authored

Hello, 

Thanks for the explanation.

Regards,

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