Paralleling Schottky Rectifiers
in [Design]
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From: Hammy on 24 Jul 2010 09:57 On 24 Jul 2010 13:01:27 GMT, Jay Ts <bitbucket(a)example.com> wrote: >Hammy wrote: >> Jay Ts <bitbucket(a)example.com> wrote: >>>dagmargoodboat wrote: >>>> I never parallel rectifiers -- that's asking for thermal runaway. But, >>>> here, OnSemi says it's cool, even necessary to get full rating: >>>> >>>> http://www.onsemi.com/PowerSolutions/product.do?id=MBR20200CTG >>>> >>>> I guess those are matched with matched drops, so runaway won't be a >>>> problem. Hmm. >>>> >>>> I need a >5A 40V diode (to carry 4A d.c.), preferably surface mount. >>> >>>Did you consider the new SiC Schottky diodes from Infineon? >>>[...] >>> >>>The IDT05S60CXK can handle 5A continuous (42 A surge) with a maximum PIV >>>of 600V and maximum power dissipation of 55 watts. [...] >>> >> Why would you spend almost $10.00 on a diode optimised for hard >> switching to use it in a DC application? > >The Infineon IDT05S60CXK I referred to is just $2.51 in >single quantities at Mouser, not $10. > >However, it was my mistake that I did not realize that there >were Si Schottky diodes that can handle 5 amps in a single >configuration, and cost much less. Oops. ;-) > >Jay Ts Price isn't the only reason why a SIC is a bad choice for a dc APP. They have Vf of 1.2 to 1.6v with a positive tempco.Which when compared to a 8-12A Si Shottkey running at 4Adc with a Vf of 0.395 to 0.45V at a working junction temp you would easily have three to four times the losses with a SIC. SIC's were made to reduce losses in the switching mosfet mainly by eliminating Reverse recovery which can cause ringing and the FET also has to eat the reverse recovery charge every switching transition.In high power app's this can contribute significantly to switching looses in the FET. They are really only beneficial when switching losses can be reduced enough to cancel out the higher conduction losses that a SIC has which is when you get up into higher power 1kW or so. They can also reduce ringing EMI/rfi which is another benefit which may justify there use at lower power levels. |