Solution Finder Get Tech Support

TOP243 Snubber Design for Reducşng Radiated Immunity

Posted by: koksalocal on
Is there any practical method to design snubber circuits for reducing radiated emission ( capacitor and resistor values) to the primary side and secondary diodes.

Comments

Submitted by VCastrellon on 11/24/2008
Suppression of radiated emissions is very trekky because what works for some specific design may not work for another design. Some of the general rules are: 1._For the PCB layout try to minimize the length of the traces and the areas with high switching current and high switching voltages. 2._For the DRAIN snubber blocking diode. Try to use a fast rectifier instead of ultrafast diode. Then connect a resistor in series with the rectifier (about 20 ohms). This resistor minimize the ringing of the blocking diode. . Make sure you measure your Maximum DRAIN voltage under worst conditions to make sure this voltage is below 700V. 3._Use ferrite bead in series with the bias and output rectifiers. 4._Connect an RC network from DRAIN to SOURCE (about 30 pF 100 ohms), This network slows down the edge of the DRAIN voltage waveform and reduce radiations. 5._ For the snubber RC at the output rectifier. Try just to minimize the ringing of the diode. Keep in mind that the heavier the snubber, the lower your power supply efficiency. 6._ Add a snubber to bias rectifier. Even though this rectifier usually conducts low current, sometimes it is a source of noise.