All,
I burned up several Buck Converters (SZBK07-uses LM2511). They're rated for 300W, 20A. Input is 21V adj to 7.5V out. Running brushless motors with changind load, 15A peak current from measurements. With electronic load the converter puts out 22A @ 7.5V but gets HOT.
I think my problem is HEAT. First attempt to make them more reliable was to add cooling fans and so far that seems to be working but maybe I just got a good one. Looking for advice/suggestions as I really need these to be more reliable and can't find anything better in the same size or smaller. Here are my thoughts/research so far on what might help:
1. Add cooling fans to heatsinks
2. Change the NCE8290's to IRFB3077's
NCE8290's rated for 82V, 90A and have an Rds of 7.5mΩ while the IFRB3077 is rated for 75V, 120A and has a much lower Rds of 3.3mΩ.
3. Change the R004 current sense resistor to an R005 to reduce peak current by about 2A
I have not been able to determine exactly why they are failing but I'm sure I'm overloading/overheating them. One had a shorted FET, another loses output voltage once I get to 13.5A draw, One has a Low Side FET that gets really hot @ no load and that one won't put out any voltage, and One lost all regulation-with 21V in output is 18.5V but still puts out good current?
Any help/suggestions appreciated.
I burned up several Buck Converters (SZBK07-uses LM2511). They're rated for 300W, 20A. Input is 21V adj to 7.5V out. Running brushless motors with changind load, 15A peak current from measurements. With electronic load the converter puts out 22A @ 7.5V but gets HOT.
I think my problem is HEAT. First attempt to make them more reliable was to add cooling fans and so far that seems to be working but maybe I just got a good one. Looking for advice/suggestions as I really need these to be more reliable and can't find anything better in the same size or smaller. Here are my thoughts/research so far on what might help:
1. Add cooling fans to heatsinks
2. Change the NCE8290's to IRFB3077's
NCE8290's rated for 82V, 90A and have an Rds of 7.5mΩ while the IFRB3077 is rated for 75V, 120A and has a much lower Rds of 3.3mΩ.
3. Change the R004 current sense resistor to an R005 to reduce peak current by about 2A
I have not been able to determine exactly why they are failing but I'm sure I'm overloading/overheating them. One had a shorted FET, another loses output voltage once I get to 13.5A draw, One has a Low Side FET that gets really hot @ no load and that one won't put out any voltage, and One lost all regulation-with 21V in output is 18.5V but still puts out good current?
Any help/suggestions appreciated.