Salvador12
Full Member level 4
Hi folks, I have been building and learning about smps , now I made a half bridge off line smps and it has worked with various different switching mosfets, at first I started with lower power ones then with higher.
for those who havent seen my idea and schematic I will attach one on thsi thread.
the last devices I used are some vishay power mosfets Sihg47n60e.they are rated for 600 volts dc and 47 amps max at room temp.
now at first i connected only one transformer anbd the resulting rectifier and smoothing caps at the secondary of that transformer and it worked , previously i have pushed up to 1.2kW through this transformer even with such old and comparably low power mosfets as the IRFP460.
although I once blew these too when i connected a load which had a cold starting resistance of about 10 ohms. the maximum load at which I got the 1.2kw running at 160v DC was about 20 ohms and 15 ohms cold.
this last time I had these 47 amp rated mosfets and as I said i started the first transformer and they worked with a moderate output load, then I connected a second transformer which is almoust identical to the first one also has a rectifier and smoothing and the secondary and had a small load attached , as I attempted to start this configuration the mosfets went short and dead.
so heres my question (not good at heavy maths) how powerful the devices should be for me to choose , since the inrush startup current of any transformer is if i remeber correctly atleast 7 times the normal idle current and especially if the secondary has a load attached to it.
maybe i should go for IGBT ?I have seen the IR2110 being used to drive thme too.before i plugged in my setup i checked the rive signal with a scope and it was ok.also given that the single transformer action was working i think it was overcurrent at the startup which caused the device failure.
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the schematic
for those who havent seen my idea and schematic I will attach one on thsi thread.
the last devices I used are some vishay power mosfets Sihg47n60e.they are rated for 600 volts dc and 47 amps max at room temp.
now at first i connected only one transformer anbd the resulting rectifier and smoothing caps at the secondary of that transformer and it worked , previously i have pushed up to 1.2kW through this transformer even with such old and comparably low power mosfets as the IRFP460.
although I once blew these too when i connected a load which had a cold starting resistance of about 10 ohms. the maximum load at which I got the 1.2kw running at 160v DC was about 20 ohms and 15 ohms cold.
this last time I had these 47 amp rated mosfets and as I said i started the first transformer and they worked with a moderate output load, then I connected a second transformer which is almoust identical to the first one also has a rectifier and smoothing and the secondary and had a small load attached , as I attempted to start this configuration the mosfets went short and dead.
so heres my question (not good at heavy maths) how powerful the devices should be for me to choose , since the inrush startup current of any transformer is if i remeber correctly atleast 7 times the normal idle current and especially if the secondary has a load attached to it.
maybe i should go for IGBT ?I have seen the IR2110 being used to drive thme too.before i plugged in my setup i checked the rive signal with a scope and it was ok.also given that the single transformer action was working i think it was overcurrent at the startup which caused the device failure.
- - - Updated - - -
the schematic