I have see on several audio projects that people will bypass the diodes in a bridge rectifier (discrete diodes or monolithic part) with small .1-.01uF parts. Is this for RF shunting or what purpose do they serve? Thanks!
They reduce HF noise caused by the reverse recovery current being switched off when the current carriers in the diodes are depleted.
The fast switching times of this current edge produces HF noise, the capacitor acts as short to the HF noise and prevents it from causing interference with the powered system.
What's an appropriate size? Just any .1 or .01uF cap, or should I size it based on the speed of the diode? This is for the main power supply bridge rectifier. Thanks guys
What's an appropriate size? Just any .1 or .01uF cap, or should I size it based on the speed of the diode? This is for the main power supply bridge rectifier. Thanks guys
Hi,
It would depend upon the psu's usage, eg: if it was powering an audio system I would use 100nF.
For a bog standard application I would either use 10nF or none at all.!
hi,
The reason for asking, is that in some DIY psu projects, the builder uses a huge value capacitor just after the bridge,
thinking it will kill any noise.
The problem is the very high recharge current that flows for a very short time thru the transformer and rectifiers,
this can cause interference in the powered application.
I have see on several audio projects that people will bypass the diodes in a bridge rectifier (discrete diodes or monolithic part) with small .1-.01uF parts. Is this for RF shunting or what purpose do they serve? Thanks!
I've always been told that they are to prevent mains spikes killing the rectifier diodes - I must admit I've never fitted them in anything I've ever made, but I always use well over rated diodes.