BARACUDA-Legend-1

[Deghbar613]

hello everyone
what makes lf9540 so so so hot
please any idea

[GeoMax]

Hi,

the TX-pulse width is probably not correkt or you have a fake IRF MosFet from China.

[kt315]

you do not have a signal (impulse) on the Gate of mos-fet. why you write LF9540?

[Deghbar613]

you do not have a signal (impulse) on the Gate of mos-fet. why you write LF9540?

sorry kt315 tired mistake irf9540

[Deghbar613]

Hi,

the TX-pulse width is probably not correkt or you have a fake IRF MosFet from China.

how it look like TX-pulse width?

[Deghbar613]

sorry kt315 tired mistake irf9540

This some info from oscilloscope
this irf9540 gate

This coil

[kt315]

ok. you changed IRF9640, that is clear noted in the schematic, on IRF9540. while 9540 is 100V max, 9640 is 200V.
and you sure get the zener effect this heat out on the cutoff above 100V pp.

[Carl-NC]

Your waveforms look normal. The PMOS is supposed to get fairly hot because it avalanches during turn-off. Many PI designs even add a heat sink. It looks like your TX pulse width is 150us; one thing you can try is reducing it to 100us or even 50us and see if it runs cooler. If it does, then everything is probably OK.

[Deghbar613]

Your waveforms look normal. The PMOS is supposed to get fairly hot because it avalanches during turn-off. Many PI designs even add a heat sink. It looks like your TX pulse width is 150us; one thing you can try is reducing it to 100us or even 50us and see if it runs cooler. If it does, then everything is probably OK.

How can i reducing TX pulse with ?

[Deghbar613]

Thx kt315 AND carl-NC and everyone who help

[Carl-NC]

How can i reducing TX pulse with ?

I'm not familiar with how the circuit works, but it looks l to me that U4a and U4b create the TX pulse so I would alter the R & C values around them to see what happens. In particular, I would start with R10 & R11.

[Deghbar613]

thx carl it works now irf9540 just worm