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Registered Member #2063
Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352
just bought a BEEFY diode brick for 5 bucks. MUR10020CT seems to work when I tested it with a multimeter on the datasheet it says 40v RMS, does it mean it can only safely rectify 40 volts AC without self destruction? and what are fast recovery diodes for?
Fast refers to the recovery time, the time it takes the diode to switch from forward conduction to blocking. While in the recovery time the diode acts as a conductor. This usually means we have a short. When rectifying high frequency AC we need a fast diode or we will spend too much time (% of the cycle time) in the recovery zone. If we use slow diodes with a HF AC we get higher losses and possibly EMI noise because of the current spikes while the diode conducts in reverse.
To sum it up, the most common place to find them is in the rectifying stage after a transformer in switched mode power supplyes, since they work at high frequency.
Registered Member #1667
Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 374
This is what reverse recovery looks like: a schematic illustration looks like this
reverse recovery characteristics also degrade with increasing temperature.
The importance of * reverse recovery time trr * stored charge Qrr * temperature dependency
is for example reflected in the R (equilibrium) and C (transient symmetrization) values needed to symmetrize a series arrangement of power diodes
(where n is #diodes in series, Ur rated voltage, Um max. desired voltage across the network, dQrr is the max. deviation of Qrr for any two diodes over the full temperature range)
So fast diodes with soft recovery (no snapping) and ultra low Qrr are desirable. SiC Diodes are the most superior ones that currently begin to enter the market.
I hope that helps in comparing your diode to others and in getting an idea what your datasheet says.
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diode bricks and questions
