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SMPS are based on the ________ principle.
Phase control
Integral control
Chopper
MOSFET
Chopper
Switched-Mode Power Supplies (SMPS) are based on the chopper principle, where DC input voltage is rapidly switched on and off at high frequencies to regulate output voltage. By controlling the duty cycle of this high-frequency switching, the average voltage delivered to the load is efficiently controlled. This high-frequency operation allows the use of significantly smaller and lighter transformers and inductors compared to linear power supplies.
Switched-Mode Power Supplies (SMPS) are based on the chopper principle, where DC input voltage is rapidly switched on and off at high frequencies to regulate output voltage. By controlling the duty cycle of this high-frequency switching, the average voltage delivered to the load is efficiently controlled. This high-frequency operation allows the use of significantly smaller and lighter transformers and inductors compared to linear power supplies.
VoтАЛ=DтЛЕVinтАЛ тАФ Output voltage of a basic buck chopper, where D is duty cycle
D=TsтАЛTonтАЛтАЛ=TonтАЛтЛЕfsтАЛ тАФ Duty cycle formula in PWM switching control
In an SMPS, an unregulated DC voltage (often obtained by rectifying AC mains) is applied to a high-speed semiconductor switch (like a MOSFET or IGBT). The switch operates at high frequencies (typically 20 kHz to several hundred kHz) in ON/OFF modes, functioning as a chopper. The chopped square wave is then stepped up or down using a high-frequency transformer, rectified, and filtered using passive L-C elements to obtain a smooth, regulated DC output. Regulation is maintained using Pulse Width Modulation (PWM) feedback.
SMPS switches power semiconductor devices fully ON or fully OFF, minimizing power dissipation.
Operating at high switching frequencies (20 kHz to 1 MHz) significantly reduces the size and weight of magnetic components (transformers/inductors) and capacitors.
The basic power conversion mechanism in SMPS is DC-to-DC conversion, which is the core definition of a chopper.
High efficiency (typically 80% to 95%) due to low switching dissipation
Compact size and lightweight compared to linear regulated power supplies
Flexible output voltage control via Duty Cycle (PWM) adjustment
Generates high-frequency electromagnetic interference (EMI) and switching noise
Higher circuit complexity requiring control ICs and feedback circuitry
Personal computer and server power supply units (PSUs)
Battery chargers for mobile devices and electric vehicles
Consumer electronics, TVs, and industrial automation control systems
Option A (Phase control) refers to controlling power by varying the firing/triggering angle of thyristors (SCRs) in AC circuits.
Option B (Integral control) is a control system mechanism or a technique where power is delivered in complete cycles (Integral Cycle Control).
Option D (MOSFET) is a switching device used inside an SMPS circuit, but it is a component rather than the governing operating principle.
C is correct тАФ SMPS operates on the chopper principle by rapidly turning a semiconductor switch ON and OFF to convert and regulate DC power efficiently.
Remember for competitive exams: Linear Power Supplies operate semiconductors in the active/linear region (low efficiency ~40-50%), while SMPS/Choppers operate switches in saturation and cut-off regions (high efficiency >80%).