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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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Which among the following act as a switch in switching regulator?
Rectifiers
Diode
Transistors
Relays
Transistors
In a switching regulator, power transistors such as MOSFETs or BJTs act as the primary switching element. They rapidly switch ON and OFF at high frequencies to regulate the output voltage efficiently.
In a switching regulator, power transistors such as MOSFETs or BJTs act as the primary switching element. They rapidly switch ON and OFF at high frequencies to regulate the output voltage efficiently.
Vout=D⋅Vin — Output voltage of a Buck Converter, where D is the duty cycle
D=Ton+ToffTon — Duty cycle of the switching transistor
The switching regulator operates by rapidly toggling a transistor between its fully ON (saturation) and fully OFF (cutoff) states. When the transistor is ON, energy is stored in reactive components like inductors and capacitors; when it turns OFF, that energy is released to the load, minimizing power dissipation across the switch.
Transistors operate only in saturation (ON) and cutoff (OFF) states in switching regulators.
Power dissipation in switching regulators is very low compared to linear regulators, yielding high efficiency (80%-95%).
High power efficiency due to minimal switching losses
Can step up (boost), step down (buck), or invert output voltages
Requires high-frequency filtering to suppress Switching EMI noise
More complex circuit design compared to linear regulators
DC-DC Converters (Buck, Boost, Buck-Boost)
Switched-Mode Power Supplies (SMPS) for computers and mobile chargers
Option A (Rectifiers) are used to convert AC to DC, not to switch control in regulators.
Option B (Diode) serves as a freewheeling/catch diode to provide a current path during transistor turn-off.
Option D (Relays) are electromechanical switches that are too slow for fast PWM control (kHz to MHz range).
C is correct — Power transistors (such as MOSFETs or BJTs) operate as high-frequency switches to control power transfer efficiently in switching regulators.
Remember that in linear regulators the transistor operates in the active region (acting as a variable resistor), whereas in switching regulators it operates strictly as an ON/OFF switch.