|26th May 2010, 04:11 PM||#31|
Join Date: Jan 2008
I think I solved my problem.
I had a wrong estimation of the primary mosfets Coss so that the shim inductance was too high.
Now I have reduced my shim inductance to 2.5uH (it was 10uH) and everything is fine.
With some work on RC and RCD snubbers my peak voltage on the output
mosfetss is clamped at around 90V with acceptable ringing. The power
dissipation in every RCD clamp resistor is around 2.5W which is something I can manage without problem with 2 parallel 3W resistors.
With the reduction of the shim inductance the A-B leg of the H-bridge will enter in ZVS at an higher output current: at around 40A out the A-B leg enters ZVS and the C-D leg enters ZVS at around 10A.
Even when it works in hard switching the efficiency does not suffer too much: it remains above 92.5% from 20A output and above.
"Do you have pics of the layout? "
Attached you will find the secondary side layout. It is a 4 layers pcb.
All the snubber components are not mounted on the pcb but mounted flying on the back side triying to keep the connections as short as possible
|1st May 2017, 04:02 PM||#33|
Join Date: May 2009
Location: Sprang-capelle Holland.
I did see this
I am busy with a fase shift welding inverter for MIG, this needs to be a voltage feedbacked one, a constant voltage source.
I ask myself there are different topologies and I did see that for welding she use the quasi resonant types with a UC1865 controller who do have a VCO and not a normal pcm as in the fase shift version. I read however that fase shift get used more, these do work better? or maybe someone on this thread do now what is the best way.
For the supply who I want to use for the hybrid amplifiers what do put put 65 + 65 v 20 amps 300 volts 300 mA, and 15 volts 5 amps, resonant type with the UC3865 because the transformer sees then a sinusoidal signal who is more friendly for capacitors, and I have soft switching, for welding this is also used.
Thanks for advise,
PS can I use a toiroidal transformer like this one?. keeps radiation small.
Last edited by kees52; 1st May 2017 at 04:06 PM.
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