Bridge rectifier capacitor filtering principle

GW MB10F 0.8A 1000V rectifier bridge

The following is the circuit diagram of [bridge rectifier capacitor filtering principle]

The capacitor filter circuit utilizes the charging and discharging functions of the capacitor to make the output voltage tend to be smooth.

When u2 is positive half cycle and the value is greater than the voltage uC across the capacitor, the diodes D1 and D3 are turned on, the D2 and D4 tubes are turned off, the current flows through the load resistor RL, and the other capacitor C is charged. When uC>u2, the D1 and D3 tubes are reverse biased and turned off, and the capacitor is discharged through the load resistor RL, and the uC slowly decreases exponentially.

When u2 is negative half-cycle amplitude changes just above uC, D2 and D4 become conductive due to the forward voltage, u2 charges C again, uC rises to the peak of u2 and then begins to fall; when it drops to a certain value D2 and D4 become cutoff, C discharges to RL, and uC decreases exponentially; when discharge reaches a certain value, D1 and D3 become conductive, and the above process is repeated.

The effect of RL and C on charge and discharge,

The charging time constant of the capacitor is rDC. Because the rD of the diode is small, the charging time constant is small and the charging speed is fast; RLC is the discharge time constant. Because the RL is large, the discharge time constant is much larger than the charging time constant. Therefore, the filtering effect depends on Discharge time constant.

The larger the capacitance C, the larger the load resistance RL, the smoother the output voltage after filtering, and the larger the average value.