Which one of the following circuits allows control of the SMPS output?

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ALP CBT 2 Electronic Mechanic Previous Paper: Held on 21 Jan 2019 Shift 2

Answer 1

Switched Mode Power Supply:

SMPS is based on the chopper principle, the output dc voltage is controlled by varying the duty cycle of chopper by PWM (Pulse Width Modulation) or FM (Frequency Modulation) techniques.
In SMPS, PWM technique is used for the inverter. The output of the inverter then converted to dc by a diode rectifier.
As the inverter is made to operate at a very high frequency, the ripples on the dc output voltage can be filtered out easily by using small filter components.
If the switching devices are power transistors, the chopping frequency is limited to 40 kHz.
For power MOSFETs, the chopping frequency is of the order of 200 kHz; as a result, the size of the filter circuit and transformer decreases leading to considerable savings.
At such frequency, ferrite core is used in transformers.
Like other power supplies, an SMPS transfers power from a DC or AC source (often mains power), to DC loads, such as a personal computer, while converting voltage and current characteristics. Switched-mode power supplies may also be substantially smaller and lighter than a linear supply due to the smaller transformer size and weight.