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1.2. Rectifier and filter

The rectifier converts ac voltage into dc voltage. The basic operation of this component can be understood by observing the voltage and currents in figure 2. In these graphs, it can be seen that the voltage at the VC1 filter capacitor is not purely direct current, but rather that it contains a ripple that cannot be discarded. This is due to the fact that the capacitor is charged and discharged at each ac voltage period. Also, you should notice that the Is current waveform is a pulse current. The pulse is produced by the charge of the filter capacitor . When the secondary voltage drops below the capacitor voltage, current flow through the secondary is stopped and then the load current is supplied by the capacitor. The fact that the transformer current is a pulse current causes its rms value to be higher than a sinusoidal wave value and, therefore, the apparent power at the power supply input is considerably higher than the rms power.