Hi all,
I'm designing a 12VDC 3.5A power supply around a LM2679 switching regulator (datasheet: http://www.ti.com/lit/ds/symlink/lm2679.pdf). I was feeling great about things until I got to the bridge rectifier diodes/reservoir cap.
Everything I've designed thus far has been easy in regards to picking diodes: figure out the DC load current, pick a diode with an Iavg rating of considerably more and things will be fine. However, now with higher currents involved, that low Vf we could usually ignore will make the diode dissipate significant power and therefore heat.
Now I realize the above "shorthand" method is wrong because the diode in a bridge remains off most of the time until the rectified voltage exceeds the voltage of the reservoir cap, at which point the diodes turn on and deliver current. In my sims, this current with a 11,700uF cap is 27A (!!) although this is brief, but seems to average out to be around 1.7A.
So my question is, how do we ensure we are picking diodes that are up for the job at higher currents like this? I'm looking at the 80SQ045N which is rated for 8A with a very low Vf, but it says it is optimized for hf switching. Can a DO-201 really handle a linear application like this, especially at 5-12A?
Thank you in advance!
I'm designing a 12VDC 3.5A power supply around a LM2679 switching regulator (datasheet: http://www.ti.com/lit/ds/symlink/lm2679.pdf). I was feeling great about things until I got to the bridge rectifier diodes/reservoir cap.
Everything I've designed thus far has been easy in regards to picking diodes: figure out the DC load current, pick a diode with an Iavg rating of considerably more and things will be fine. However, now with higher currents involved, that low Vf we could usually ignore will make the diode dissipate significant power and therefore heat.
Now I realize the above "shorthand" method is wrong because the diode in a bridge remains off most of the time until the rectified voltage exceeds the voltage of the reservoir cap, at which point the diodes turn on and deliver current. In my sims, this current with a 11,700uF cap is 27A (!!) although this is brief, but seems to average out to be around 1.7A.
So my question is, how do we ensure we are picking diodes that are up for the job at higher currents like this? I'm looking at the 80SQ045N which is rated for 8A with a very low Vf, but it says it is optimized for hf switching. Can a DO-201 really handle a linear application like this, especially at 5-12A?
Thank you in advance!