Talking about the filter capacitor of the rectifier bridge

The rectifier bridge circuit is a diode rectifier bridge. When the input voltage is in the positive half cycle of the AC voltage, the diode and the load resistor form a loop. The output of the rectifier bridge circuit is also a pulsating voltage that does not change in direction, but the pulsating frequency is twice that of the half-wave rectification.

The basic characteristics of the rectifier bridge circuit are as follows:

1. The output of the rectifier bridge is a pulsating DC voltage.

2. The AC utilization of the rectifier bridge circuit is 100%.

3. Capacitor output rectifier bridge circuit, the large reverse voltage borne by the diode is twice the AC peak voltage.

4. The load current of the rectifier bridge circuit diode is only half of the half-wave rectification.

In the rectifier bridge, a suitable filter capacitor should be selected, so how to select a filter capacitor? Usually, the filter capacitor is calculated according to the formula of the power supply filter output ripple coefficient, which requires two values of the large output voltage and current of the bridge rectifier. C >> 0.289 / {f × (U / I) × ACv}. C is the filter capacitor, 0.289 is a constant derived from the ripple coefficient of the half-wave resistive load rectifier circuit, f is the pulse frequency of the rectifier circuit, U is the large output voltage of the rectifier circuit, I is the large output current of the rectifier circuit, and ACv is the ripple coefficient.

So is it not necessary to install a filter capacitor after the rectifier bridge? What are the consequences? After the rectification, the pulsating direct current is added without the filtering capacitor. The value is measured with a multimeter, and its peak value still reaches about 22V. If the load is a power tool, electric heating equipment, etc., no filter capacitor is required. However, it cannot be used for electronic equipment and audio equipment. If the electric equipment belongs to the latter, the rectified voltage can be filtered after being reduced in series through 7-9 rectifier diodes. Each diode steps down by about 0.7V. The rated current of the diode is more than twice the load current.

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