On 11/20/05, Wouter van Ooijen <wouter@voti.nl> wrote:
> In circuits I sometimes see capacitors over each of the fout diodes in a
> diode bridge. What is the prurpose and effect of these capacitors?

There are two explanation and both could fit to your conclusions:

1. the noise from the AC line (which are passing through the
transformer, which shows you have used a poor low cost transformer
without having a shield connected to ground... or directly mains
without LC filters) is killed on the filtering capacitor using the
current path created by the capacitors connected in parallel with the
bridge diodes

2.the rectifier diodes are poors (they can't switch enough fast the
current you're sourcing from the transformer, ie if you're driving
motors with PWM technique) and are inducing a noise which can't be
killed only with capacitors mounted in parallel with diodes

cheers,
Vasile

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