Calculation of output capacitor value in bridge rectifier circuit

We have mentioned before that the selection of capacitors is related to the application scenarios of capacitors in different circuits. This article mainly uses the bridge full-wave rectifier circuit as an example to evaluate the required capacitor selection.

Minimum capacitor value: C = load current I / (ripple voltage V * frequency)

Where C-- is the minimum required capacitance

Load current I--is the load current of the rectifier circuit

Ripple voltage V--is the voltage fluctuation range measured at the output end of the rectifier

Frequency - For a bridge full-wave rectifier circuit, this is twice the frequency of the input signal.

Example analysis:

To make it easier to understand, let's explain a practical example. The circuit below is a bridge rectifier circuit. The input voltage is 120V at 60Hz, the load current is 2A, and the ripple voltage requirement is 43V (peak-to-peak). What we need to do is to evaluate the minimum capacitance value of C1 required.

According to this formula: Minimum capacitance: C = load current I / (ripple voltage V * frequency), it can be concluded that:

Cmin = 2A / (43V X 2 X 60Hz) = 387uF;

To verify whether our calculation is accurate, we can use simulation software to simulate. When the output capacitor uses 387uF, the peak-to-peak value of the ripple voltage is 35.5V. It is close to the calculated result of 43V. Of course, the result we calculated is the minimum capacitance, so by selecting a higher value capacitor, the ripple voltage will be further reduced.