Soft Recovery Diode Types M0437WC080 to M0437WC140

Data Sheet. Types M0437WC080 to M0437WC140 Issue 3

Page 4 of 11

October 2014





thJK

MAX

J

SINK

R

f

k

E

T

T











)

(

5.0 Reverse Recovery Loss

The following procedure is recommended for use where it is necessary to include reverse recovery loss.

From waveforms of recovery current obtained from a high frequency shunt (see Note 1) and reverse

voltage present during recovery, an instantaneous reverse recovery loss waveform must be constructed.

Let the area under this waveform be E joules per pulse. A new sink temperature can then be evaluated

from:

Where k = 0.2314 (°C/W)/s

E = Area under reverse loss waveform per pulse in joules (W.s.)

f = Rated frequency in Hz at the original sink temperature.

The total dissipation is now given by:

f

E

W

W

original

tot







)

(

)

(

NOTE 1 - Reverse Recovery Loss by Measurement

This device has a low reverse recovered charge and peak reverse recovery current. When measuring the

charge, care must be taken to ensure that:

(a) AC coupled devices such as current transformers are not affected by prior passage of high

amplitude forward current.

(b) A suitable, polarised, clipping circuit must be connected to the input of the measuring oscilloscope

to avoid overloading the internal amplifiers by the relatively high amplitude forward current signal.

(c) Measurement of reverse recovery waveform should be carried out with an appropriate critically

damped snubber, connected across diode anode to cathode. The formula used for the calculation of this

snubber is shown below:

dt

di

S

r

C

V

R





 4

2

Where:

R = Snubber resistance

6.0 Snubber Components

When selecting snubber components, care must be taken not to use excessively large values of snubber

capacitor or excessively small values of snubber resistor. Such excessive component values may lead to

device damage due to the large resultant values of snubber discharge current. If required, please consult

the factory for assistance.