Interesting Facts (1) Diode Reverse Recovery

PowerAnts

Interesting Facts (1) Diode Reverse Recovery [Copy link]

I have had some time recently and saw some interesting anecdotes. Let me first talk about the reverse recovery of diodes in power frequency rectifier and filter circuits. A group of nerds quoted from classics but had absolutely no research thinking or solution-predicting ability to solve problems.

In order to make the explanation more illustrative, all conditions are listed according to the worst case:
1. The voltage drop of silicon diode is 0.6V at 100 degrees junction temperature. The smaller the junction voltage drop, the shorter the transition time, and the more serious the problem;
2. In the rectifier filter circuit, the diode cut-off voltage is between 0-1.414*Vin. In order to make the conditions the worst, the dv/dt at zero crossing is the largest;
3. Carefully select the worst antique silicon diode with a reverse recovery time of 3uS

I used a calculator to find that the maximum AC input is 450V, and the diode PN junction current can drop to zero safely and naturally, without reverse recovery problems.

PowerAnts

Teach people to fish, why not teach them to fish?

The calculator types:

The first step, 360*0.000003/0.02=0.054 (degrees)

Step 2, 0.6/SIN(0.054)/1.414=450.226 (Vrms)

Precise locking safety limit

PowerAnts

Some people may wonder, in the specification of silicon diodes, the forward voltage drop is 0.8-1.2V, why is this voltage not used when considering reverse recovery?

Answer: The measured voltage drop is composed of the junction voltage drop, the body resistance of the semiconductor material and the package resistance voltage drop. The reverse recovery characteristics are determined by the PN junction and have nothing to do with the body resistance and package resistance, so they are not considered!