External MOSFET Blown in StackFET configuartion

Posted by: vignesh_viki on 09/19/2015

HI......

I design a smps working on 85AC to 300VAC...

I extend input range into 85AC to 500AC using stackFET...

It working fine on gradually inceasing the input voltage upto 500VAC.

But suddenly applying 500VAC the External MOSFET(IRFBC40), 3X P6KE180A, 10 ohms resistor,15V Zener burned.

Please answer as early as possible..........

Comments

Hi,

Could you please send the schematic, PCB Layout and and transformer document?

Regards,

PI-NANO

i attatch the sch and transformer constrcution file for your refference... please reply as early as possible

Attachment	Size
TOP268_2 transformer.pdf (76.13 KB)	76.13 KB
stack fet 2.JPG (50.26 KB)	50.26 KB

Hi,

What is output power that the power supply is designed for?

Can you probe Vgs and Vds at turn on and in steady state?

How did you choose resistors R6, R8, R16 and zeners D9, D10, D11?

Regards,

PI-NANO

Based on DI-124 I choose resistors R6, R8, R16 and zeners D9, D10, D11 values.

Hi,

What is output power that the power supply is designed for?

Can you probe Vgs and Vds at turn on and in steady state?

Regards,

PI-NANO

This is 50W design.

I dont have a high voltage probe to measure VDS

Hi,

StackFET designs are recommended only for very low power applications. DI-124 was designed for a 3W application.

Regards,

PI-NANO

but in DER stackFET designed for 19.3W

Hi,

Still this design is very high power. However you can try the following things on your design and see if the problem gets resolved.

1. Please try ultrafast diode on D6 (You could use UF4007)

2. Short R7 or replace with 0 Ohms.

3. Move R16 in series with D9 and connect D12 cathde and M1 gate between R8 and R16

Regards,

PI-NANO