Electronics > Projects, Designs, and Technical Stuff
sg3525 gets mosfets heated
Mechatrommer:
--- Quote from: Zero999 on December 29, 2019, 12:00:29 pm ---
--- Quote from: Mechatrommer on December 29, 2019, 11:58:26 am ---i suspect Q2 and Q3 must be N channel mosfet. Q1 and Q4 must be P channel mosfet which is correct from your drawing.
--- End quote ---
No, they're clearly drawn as N-channel and if they were P-channel, the circuit wouldn't work at all, since they would be off, when the N-channel devices were on.
--- End quote ---
yeah i got it mixed up, earlier post corrected.
dave_j_fan:
--- Quote from: Mechatrommer on December 29, 2019, 11:58:26 am ---i suspect Q1 and Q4 must be P channel mosfet. Q2 and Q3 must be N channel mosfet which is correct from your drawing.
--- End quote ---
no the 4 mosfets are n channels as per design.
the diodes helping for boot straping.
but i have used 4007 in place FR107.may be slow diodes not ableto boost voltage
dave_j_fan:
after searching a bit i got a high side driver with 4148
and also just 547 npn transistors .
i am bit confused how do i use it
Zero999:
--- Quote from: dave_j_fan on December 29, 2019, 12:31:58 pm ---
--- Quote from: Mechatrommer on December 29, 2019, 11:58:26 am ---i suspect Q1 and Q4 must be P channel mosfet. Q2 and Q3 must be N channel mosfet which is correct from your drawing.
--- End quote ---
no the 4 mosfets are n channels as per design.
the diodes helping for boot straping.
but i have used 4007 in place FR107.may be slow diodes not ableto boost voltage
--- End quote ---
Oh, I missed the bootstrapping part. Still you've got the slow switching speed of the opto-couplers and the 2k2 pull-down resistors.
It's possible to make a bootstrapped high-side MOSFET driver from discrete parts. Two transistors need to be used: one to pull-up and another to pull-down.
LTSpice simulation
https://www.eevblog.com/forum/projects/high(ish)-frequency-bootstrap-circuit-for-high-side-switching/msg2678304/#msg2678304
My advice is not to bother. Use a centre tapped transformer. Or better, scrap the inverter and use a 12V fan in the first place. It's always best to avoid voltage conversion whenever possible,
dave_j_fan:
thank u .first of all, "issue is fixed "after adding high speed diode.
radically deviating from inverter is not intended.
the unit should be deliverable to poor via volutary organization.
ct transformers have lower efficiency.i got10 one coil transformers made here before putting the proto.So i willl use this with them.
dc fan no ways a solution.many households have Ac fans only can't force to buy dc.they must be able to use ac led bulbs.in my country dc led bulbs have very poor quality.
some changes i will do
-adding feed back,i have some circuits at hand
-will try with dual transistor highside and compare performance.
need to add overload shutoff ..low battery off and a smps charger
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