reverse recovery time

Someone I know,(it wasn't me, honest!) , has built a quantity of PWM power units to drive solenoids, and has fitted 1n4001 diodes as flywheel diodes instead of the specified UF4001. He now knows why the performance is not as advertised, but I can't seem to find any data on the reverse recovery time of a 1N4001. Anyone have this data?

I don't have a scanner, other wise I would scan the chart from the Motorola data book. But here is a worded discription. On the vertical axis time is in usec and goes from 1 to 15. With 1 being the minimum at the juction of the horizontal and vertical axis.On the horizontal axis is IR/IF (drive current ratio). From left to right it is 0.1 to 10. A heavy line slopes down from 15usec to IR/IF of 10 on the right. The line is straight and at a
drive current ratio of 1 the Trr is equal to 4 usec.
Hope this helps.

spuffock said:

Someone I know,(it wasn't me, honest!) , has built a quantity of PWM power units to drive solenoids, and has fitted 1n4001 diodes as flywheel diodes instead of the specified UF4001. He now knows why the performance is not as advertised, but I can't seem to find any data on the reverse recovery time of a 1N4001. Anyone have this data?

Click to expand...

The IN4001 is a slow recovery rectifier, only suitable for mains or other low frequency use really. What frequency is the PWM running at?.

It runs at about 18 khz

spuffock said:

It runs at about 18 khz

Click to expand...

UK TV's line frequency is 15,625Hz (about 16KHz), you MUST use fast recovery diodes in line stages, or they just get red hot and die!.

So you certainly need to use a fast recovery diode for your PWM.

So I had to measure it myself. In case anyone's interested, the reverse transient in the 1N4001 lasts about 1.5us, and peaks at 8 amps. The diode runs a pale yellow on the ouch-to black finger test. The UF4001 peaks at 1amp reverse, and it's all over in 50ns.