stube40 Posted April 1, 2010 Report Share Posted April 1, 2010 I am pulling my hair out since I keep destroying the Murata NMC1215SC DC/DC converters in my CPU controlled H-Bridge design. There is no obvious signs of damage such as heat or smell, they simply stop outputting +/- 15V. Testing out of circuit against a reference device shows they truly are dead.The H-bridge design uses the 4x Murata device to provide an 4x isolated power rails for the 4x Fairchild IGBTs and the Vishay VO3120 opto-isolated MOSFET drivers.I have attached a pictures that shows the general idea of the schematic, as well as a detailed schematic with every component. The design is for switching a 150V / 40A high-voltage power source, but so far I've only been bench testing with 12V into a 27 Ohm resistor.I suppose I must be damaging the Murata's though inadequate protection, although so far I haven't been able to catch any suspicious spikes on the oscilloscope. At $20 a pop though from Farnell, these parts aint cheap and it's proving to be an expensive detective project.My only other thought is that I'm over-loading the output of the Muratas which are only rated to 1W.I'm beginning to run out of ideas - can anyone suggest something to try? Quote Link to comment Share on other sites More sharing options...
indulis Posted April 1, 2010 Report Share Posted April 1, 2010 Are you sure about that part #??? NMC series??? Quote Link to comment Share on other sites More sharing options...
stube40 Posted April 5, 2010 Author Report Share Posted April 5, 2010 Are you sure about that part #??? NMC series???DOH - my bad. Its the NMA1215SC, data sheet attached.Murata_DC_DC.pdf Quote Link to comment Share on other sites More sharing options...
indulis Posted April 6, 2010 Report Share Posted April 6, 2010 These are dual supplies... are you using only one side, 15V, or are you running it as a 30V supply? There is a data sheet warning not to exceed 1W Quote Link to comment Share on other sites More sharing options...
stube40 Posted April 6, 2010 Author Report Share Posted April 6, 2010 As shown in the attached schematic, I have a resistor/LED load across the +/- 15V terminals of the DC/DC to meet the minimum load requirements of the device, however it is the 0V/+15V terminals that I am using to power the VO3120 MOSFET driver.Schematic.pdf Quote Link to comment Share on other sites More sharing options...
indulis Posted April 7, 2010 Report Share Posted April 7, 2010 That might relate to your problem... more often than not, the regulation (if any) on bipolar supplies is done across both outputs Quote Link to comment Share on other sites More sharing options...
stube40 Posted April 8, 2010 Author Report Share Posted April 8, 2010 OK, thanks - I will adjust the circuit so the load is no longer inbalanced Quote Link to comment Share on other sites More sharing options...
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