What Does A Capacitor Do In A Bridge Rectifier

- February 26, 2019

To smooth the output of the rectifier a reservoir capacitor is used placed across the output of the reciter and in parallel with the load. For a transformer with an output voltage of voac your capacitor should charge to somewhere around voacsqrt2 14 where the 14 is the voltage lost across the two conducting diodes in your bridge rectifier.

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The main advantage of this bridge circuit configuration is that we do not require an expensive center.

What does a capacitor do in a bridge rectifier. The bridge rectifier is made up of four diodes namely d 1 d 2 d 3 d 4 and load resistor r l. The capacitor follows the rectifier to smooth the dc output. The four diodes are connected in a closed loop bridge configuration to efficiently convert the alternating current ac into direct current dc.

A bridge rectifier provides full wave rectification from a two wire ac input resulting in lower cost and weight as compared to a rectifier with a 3 wire input from a transformer with a center tapped secondary winding. This is how a full bridge rectifier works. The main advantages of a full wave bridge rectifier is that it has a smaller ac ripple value for a given load and a smaller reservoir or smoothing capacitor than an equivalent half wave rectifier.

This capacitor charges up when the voltage from the rectifier rises above that of the capacitor and then as the rectifier voltage falls the capacitor provides the required current from its stored charge. An additional smoothing capacitor is highly recommended for smoothing the voltage. Therefore the fundamental frequency of the ripple voltage is twice that of the ac supply frequency 100hz where for the half wave rectifier it is exactly equal to the supply frequency 50hz.

Your capacitor will charge to the peak bridge rectifiers output voltage minus the drop through the diodes. One of the advantages is that it can be used with regular transformers no need for center tapped ct transformers though full bridge rectifier can also be used with center tapped transformers without any problem. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input.

It has a safety resistor in parallel to discharge it safely when it is turned off.