Rectifier and filter:- It converts the ac supply voltage to a pulsating dc, which is then filtered out to reduce the amount of ripple content. It uses the power diodes in a bridge configuration to obtain the pulsating dc and the capacitor is used as a filter element.
High-frequency switching:- It uses either MOSFETs or BJTs to convert the dc voltage to high frequency ac square wave. This high-frequency ac square wave ranges from 20 kHz to 100 kHz. Since the power transistors are not operated in their active region, their operation results in low power dissipation. Thus, it is a two stage conversion. i.e. the input ac supply voltage is first rectified to dc and then the high frequency switching section changes it back to ac.
High frequency power transformer:-It isolates the circuit and steps-up or steps-down the voltage to the desired voltage level. The output of the transformer is the input of the second rectifier section, called the output rectifier section.
Output rectifier: - This rectifier section is different from the first block of the rectifier in that the frequency of the voltage is very high. Therefore, the bridge configuration of this rectifier uses a high frequency diode such as a Schottky diode and the output ripple is naturally filtered because of the number of overlaps between each individual output pulse. Since the ripple is very small in the output voltage of the rectifier, a small capacitance value is required in the filter section.
Control and feedback:- It provides a pulse width modulation(PWM) output signal. The PWM controller provides a duty-cycle that varies pulse by pulse to provide an accurate dc output voltage.