SMPS Flyback question / High Voltage / Forums

Forums

4hv.org :: Forums :: High Voltage

« Previous topic | Next topic »

SMPS Flyback question

first previous 5 6 7 8 next

Move Thread

LAN_403

brandon3055

Sun Jul 01 2012, 10:52PM

Registered Member #4548 Joined: Mon Apr 23 2012, 03:52AM
Location: tasmania
Posts: 271

In not shore about the cap but I had another thought on the topic of using a halogen transformer to run a flyback would it be possible to remove the transformer from the halogen transformer (in my experience usually a toroydal transformer) and use the inverter to run the flyback directly? That way your not dropping 240 or whatever your mains is to 12 andthen back up if you want isolation you could still rewind the halogen transformer secondary to put out higher voltage maby 20v-30v

zippotix

Wed Jul 04 2012, 04:56PM

Registered Member #5208 Joined: Thu Jun 07 2012, 06:12PM
Location:
Posts: 86

Thanks for suggestion. I'll try to disassemble it and see what can I do. This might work :). But my ZVS failed, or rather the MOSFET failed. I switched it on and off, with 2 car batteries powering it, and suddenly irfp250 white arced to the other fet, killing it too, as if batteries created some voltage spike. What the hell? Looks like I'm gonna rebuild it again, this time i'll use this schematic

. What do you think Destroyer? This schematic looks different from others, wold it work?

brandon3055

Wed Jul 04 2012, 09:45PM

Registered Member #4548 Joined: Mon Apr 23 2012, 03:52AM
Location: tasmania
Posts: 271

Looks exactly the same to me

zippotix

Thu Jul 05 2012, 05:19PM

Registered Member #5208 Joined: Thu Jun 07 2012, 06:12PM
Location:
Posts: 86

But resistors and zeners are placed directly on MOSFET's teeth. I thought that wouldn't work? Also, I know that resistors are bipolar, non directional or whatever :P, but are zeners and fast diodes bipolar?

TwirlyWhirly555

Thu Jul 05 2012, 07:40PM

Registered Member #4104 Joined: Fri Sept 23 2011, 06:54PM
Location: Uk .
Posts: 122

zippotix wrote ...

But resistors and zeners are placed directly on MOSFET's teeth. I thought that wouldn't work? Also, I know that resistors are bipolar, non directional or whatever :P, but are zeners and fast diodes bipolar?

Nothing Wrong placing The Zeners / resisters on the mosfets pins . thats what i do and have never had any issues .

The fast dioes will only conduct in one direction under normal conditions .

As for the Zener under normal operation it will conducit in on direction as normal . But if the zeners break down voltage is reached in the other direction then it will condcut aswell

So in the ZVS circuit the anode of the Zener is connected to mosfet source pin ( At 0 V ) then the cathode is connected to Gate . under normal operation the zener will not conduct . But say the Zener was a 15 Volt Rated one if the potential between gate and source excedded this valve then the zener would conduct and clamp the voltage to 15 protecting the mosfet gate from damage .

Think Thats how it goes anyway :P

zippotix

Tue Jul 10 2012, 10:32PM

Registered Member #5208 Joined: Thu Jun 07 2012, 06:12PM
Location:
Posts: 86

About the schematic I posted a 2 posts ago, are you sure it would work? On every other schematic the ground is connected to + through the 10k resistors and zeners but not on this one. Also the author of this schematic wrote "If you did that then you should take a look on the diodes that use your negative
peaks to switch of the opposite mosfet.It must be soldered from the one mosfets drain
to the other mosfets gate to switch it off at the zero voltage moment and vice versa
for the other mosfet. Take a look on the real picture it looks like a X shape." but on his schematic both UF diodes go to MOSFETs drains. A bit confusing to me.

brandon3055

Tue Jul 10 2012, 10:43PM

Registered Member #4548 Joined: Mon Apr 23 2012, 03:52AM
Location: tasmania
Posts: 271

No it all looks fine its the same as any other zvs just remember the diodes on the mosfets are zeners

zippotix

Tue Jul 10 2012, 10:55PM

Registered Member #5208 Joined: Thu Jun 07 2012, 06:12PM
Location:
Posts: 86

Sure, ill remember. Im gonna build it tomorrow, or rather solder it together. Destroyer, you seem to have destroyed many mosfets ;P. What do you think, what caused mosfet fail? Too much current? It even gave a bang. You had something like that happen to you?

brandon3055

Wed Jul 11 2012, 12:42AM

Registered Member #4548 Joined: Mon Apr 23 2012, 03:52AM
Location: tasmania
Posts: 271

I killed most of my mosfets in my sstc and a couple in my zvs induction heater (ok more then a couple

) but I have never blown any in my flyback driver possibly because it in controlled by a zvs

Edit: this is the PWM I used to controle my zvs

it did need a few modifications one irfp250 with large heat sink, replaced the input resister to around 200 ohm can't remember exactly and a small cap on the output about 1000uf the max input voltage under load is about 40v this is using the higher voltage version of the zvs with 15v zeners and 1k gat resistors

zippotix

Thu Jul 12 2012, 06:18PM

Registered Member #5208 Joined: Thu Jun 07 2012, 06:12PM
Location:
Posts: 86

Oh, looks a bit too complicated for me, for now at least :P. I've rebuilt zvs today, using the schematic I posted few posts ago, and well, it works much better, the arc is more stable. I'm little worried about heatsinks, I got them from old PC, they don't look like typical heatsinks, but are 3mm thick, and have thicker "heat dissipators", 16 of them.

first previous 5 6 7 8 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob