[Solved] Switch Mode Power Supply MCQ [Free PDF] - Objective Question Answer for Switch Mode Power Supply Quiz - Download Now! (2024)

1. Simple mode power supply
2. Switch mode power supply
3. Surge mode power supply
4. None of these

The correct answer isSwitched Mode Power Supply.

Key Points

• SMPS:
  • The full form of SMPS isSwitched Mode Power Supplyalso known asSwitching Mode Power Supply.
  • SMPS is an electronic power supply system that makesuse of a switching regulator to transfer electrical power effectively.
  • It is a PSU (power supply unit) and is usually used in computers tochange the voltageto the appropriate range for the computer.
  • An SMPSadjusts output voltage and current between different electrical configurations by switching the basics of typically lossless storage such as capacitors and inductors.
  • Ideal switching concepts determined bytransistors controlled outside of their active state that have no resistance when ‘on’ and carry no current when ‘off.’
  • It is the idea whyswitches with an ideal function will operate with 100%output, that is, all input energy is provided to the load; no power is wasted as dissipated heating.
  • In fact, such ideal systemsdo not exist, which is why a switching power source can not be 100%proficient, but it is still a vital improvement in effectiveness over a linear regulator.

Additional Information

• Benefits of SMPS:
  • The switch-mode power source is small in scale.
  • The SMPS is very lightweight.
  • SMPS power consumption is typically 60 to 70%which is ideal for use.
  • SMPS is strongly anti-interference.
  • The SMPS production range is large.

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1. Fault in inverter circuit
2. Battery is short circuited.
3. Mains earthing is not proper
4. Ampere hour (A.H) capacity of battery is not sufficient

An uninterruptible power supply (UPS), also known as a battery backup, provides emergency power to a load when the input power source or mains power fails.

The UPS always works along with the battery.

The operating time of the UPS is determined by the battery.

The capacityof the battery is measured in Ampere-hour (Ah) rating.

Ah = I× t

\(t={Ah\over I}\)

where, Ah = Capacity of battery

I = Current

t = Time

The backup time is directly proportional to Ampere-hour.

Thebackup time in UPS is less as the Ampere hour (A.H) capacity of the battery is not sufficient.

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1. Increase the VA rating of UPS
2. Increase the AH capacity of battery
3. Decrease the AH capacity of battery
4. Maintain battery terminal voltage always 90% of rating

The UPS always works along with the battery.

The operating time of the UPS is determined by the battery.

The capacityof the battery is measured in Ampere-hour (Ah) rating.

Ah = I× t

\(t={Ah\over I}\)

where, Ah = Capacity of battery

I = Current

t = Time

Thebackup time of UPS can be increased by increasing theAH capacity of the battery.

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1. Output filter coil
2. MOSFET
3. Zener diode
4. FET

The correct answer is option 1.

Block diagram ofSwitched Mode Power Supply (SMPS)

1.)Input rectifier

• The AC input from mains is first rectified in the SMPS using a rectifier to convert it into DC.
• The rectifier consists of a full wave diode bridge or module that produces an unregulated DC voltage to the Smoothing capacitor.
• The input AC passing into the rectifier has AC voltage pulses that may reduce the power factor. So control techniques are used to force the average input current to follow the sine wave

2.)Inverter

• This stage converts the rectified DC into AC using a power oscillator.
• The power oscillator has a small output transformer with a few windings at 20-100 kHz. A MOSFET amplifier controls switching.

3.)Voltage converter

• This stage has a high-frequency transformer and the inverted AC drives its primary windings.
• This creates the up and down voltage at the output. If DC is required, the output AC is converted to DC using a rectifier circuit using Silicon diodes or Schottky diodes.
• The rectified output DC is then filtered using the filter section consisting of inductors and capacitors.

4.)Output regulator

• The output stage always monitors the output voltage by comparing it with a reference voltage using a feedback system.
• In some SMPS, Open loop regulation is used without a feedback circuit and constant voltage is fed to the transformer input.

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1. High efficiency
2. AF gain
3. Power buck
4. RF gain

The correct answer is option 1.

Switched Mode Power Supply (SMPS)

• A switched-mode power supply (SMPS) is an electronic circuit that converts power using switching devices that are turned on and off at high frequencies, and storage components such as inductors or capacitors to supply power when the switching device is in its non-conduction state.
• SMPS takes AC mains input and provides DC output (3.3V to 12V).
• Switching power supplies have high efficiency and are widely used in a variety of electronic equipment, including computers and other sensitive equipment requiring stable and efficient power supply.
• The input DC supply from a rectifier or battery is fed to the inverter where it is turned on and off at high frequencies of between 20 KHz and 200 KHz by switching MOSFET or power transistors.
• The high-frequency voltage pulses from the inverter are fed to the transformer's primary winding, and the secondary AC output is rectified and smoothed to produce the required DC voltages.
• A feedback circuit monitors the output voltage and instructs the control circuit to adjust the duty cycle to maintain the output at the desired level.

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Switch Mode Power Supply Question 6

1. Relay
2. clutch
3. bimetallic-strip
4. diode

Switch Mode Power Supply Question 6 Detailed Solution

Miniature circuit breaker (MCB)

1. A miniature circuit breaker (MCB) automatically switches off the power supply during overload and faults.

2. This function of automatic switching is accomplished by a bimetallic strip.

3. Whenever continuous overcurrent flows through MCB, the bimetallic strip is heated and deflects by bending.

4. This deflection of the bimetallic strip releases a mechanical latch.

5. As this mechanical latch is attached to the operating mechanism, it causes to open the miniature circuit breaker contacts, and the MCB turns off thereby stopping the current to flow in the circuit.

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Switch Mode Power Supply Question 7

1. BJT
2. IGBT
3. MOSFET
4. GTO

Switch Mode Power Supply Question 7 Detailed Solution

Switch Mode Power Supply or SMPS is an electronic power supply that converts power using switching devices that are turned on and off at high frequencies, and storage components such as inductors or capacitors to supply power when the switching device is in its non-conduction state.

MOSFET is a most suitable device as high-frequency switch cause of low switching loss in it.

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Switch Mode Power Supply Question 8

1. Obtaining controlled DC supply
2. Switching over from one supply to another
3. Obtaining AC voltage of low frequencies
4. Obtaining AC voltage of high frequencies

Switch Mode Power Supply Question 8 Detailed Solution

Switched Mode Power Supply:

Itis an electronic power supply that incorporates a switching regulator to convert electrical power efficiently. It is used for obtaining a controlled DC supply.

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.

It uses a dc to dc switching converter switched at high frequency. The following devices can be used as switching mode DC power supplies:

• Flyback converter
• Push-pull converter
• Half-bridge converter
• Full-bridge converter

Advantages:

• Lower Weight
• Smaller Size
• Higher Efficiency
• Lower power dissipation
• Wide AC input voltage range

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Switch Mode Power Supply Question 9

1. No transformer is required
2. Higher efficiency
3. No filter required
4. Only one stage of conversion

Switch Mode Power Supply Question 9 Detailed Solution

Key differences between Linear Power Supply and Switch Mode Power Supply:

1. The main difference between the linear power supply and SMPS is that linear power supply converts the high voltage of AC into low voltage AC first then the rectification procedure takes place.

On the contrary, the SMPS converts the AC signal into DC signal first then the stepping down of voltage signal takes place.

2. The linear power supply uses a voltage regulator for voltage regulation of the output voltage while SMPS uses a feedback circuit for voltage regulation.
3. Power dissipation also plays a key role in differentiating linear power supply and SMPS.

The linear power supply also dissipates power and thus requires a heat sink, but SMPS does not require heat sink as there is no power dissipation.

4. The step-down transformer used in linear supply is bulky while in SMPS the step-down transformer is light in weight.
5. The noise disturbance is more in SMPS due to switching action; this makes SMPS inappropriate for audio and radiofrequency applications.

The linear power supply is immune to noise disturbance and thus used in audio and radiofrequency applications.

6. There is a major difference between the efficiency of the linear power supply and SMPS.

The efficiency of the linear power supply is low about 20-25% due to ohmic losses while that of SMPS is high, i.e. about 65-75%.

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Switch Mode Power Supply Question 10

1. Integral control principle
2. Frequency control principle
3. Chopper principle
4. Phase control principle

Switch Mode Power Supply Question 10 Detailed Solution

• SMPS regulator converts unregulated DC input voltage to a regulated and smooth DC output voltage at different voltage levels.
• So that the working of SMPS is based on the Chopper principle.
• A switched-mode power supply (switching-mode power supply, switch-mode power supply, switched power supply, SMPS, or switcher) is an electronic power supply that incorporates a switching regulator to convert electrical power efficiently.
• 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.
• In the SMPS regulator is accompanied by duty cycle control.
• By varying the duty cycle, the output voltage can be controlled.

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Switch Mode Power Supply Question 11

1. Duty cycle control
2. Regulator IC
3. Zener
4. Stabilizer

Switch Mode Power Supply Question 11 Detailed Solution

SMPS regulator converts unregulated DC input voltage to a regulated and smooth DC output voltage at different voltage levels.

In the SMPS regulator is accompanied by duty cycle control.

By varying the duty cycle, the output voltage can be controlled.

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Switch Mode Power Supply Question 12

1. Switch Mode Power Supply
2. Simple Mode Power Supply
3. Storage Mode Power Supply
4. Storage Mode Power Shortage

Switch Mode Power Supply Question 12 Detailed Solution

SMPS stands for Switched-Mode Power Supply. It is an electronic power supply that uses a switching regulator to convert electrical power efficiently

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Switch Mode Power Supply Question 13

1. Low efficiency
2. Bulky components
3. Generates strong electomagnetic interference field
4. Low cost

Switch Mode Power Supply Question 13 Detailed Solution

In SMPS the effect of noise and electromagnetic interference is quite significant, thus EMI filters are required.The conventional linear power supplyis immune to noise and electromagnetic interference. Hence option 3 is correct.

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Switch Mode Power Supply Question 14

1. Load resistance
2. Rectifier
3. Filter
4. Regulator

Switch Mode Power Supply Question 14 Detailed Solution

The Correct Option is A

• A DC power supplyis a type of power supply that gives direct current(DC) voltage to power a device.
• The basic DC power supply is constituted by four element - Transformer, Rectifier, Filter and Regulator.
• Hence, Load resistanceis NOT a part of DC power supply.

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Switch Mode Power Supply Question 15

1. Higher efficiency
2. Low noise at output
3. Light weight
4. Smaller size of transformer

Switch Mode Power Supply Question 15 Detailed Solution

Key differences between Linear Power Supply and Switch Mode Power Supply:

1. The main difference between the linear power supply and SMPS is that the linear power supply converts the high voltage of AC into low voltage AC first then the rectification procedure takes place. On the contrary, the SMPS converts the AC signal into a DC signal first then the stepping down of the voltage signal takes place.
2. The linear power supply uses a voltage regulator for voltage regulation of the output voltage while SMPS uses a feedback circuit for voltage regulation.
3. Power dissipation also plays a key role in differentiating linear power supply and SMPS. The linear power supply also dissipates power and thus requires a heat sink, but SMPS does not require a heat sink as there is no power dissipation.
4. The step-down transformer used in linear supply is bulky while in SMPS the step-down transformer is light in weight.
5. The noise disturbance is more in SMPS due to switching action; this makes SMPS inappropriate for audio and radiofrequency applications.The linear power supply is immune to noise disturbance and is thus used in audio and radiofrequency applications.
6. There is a major difference between the efficiency of the linear power supply and SMPS. The efficiency of the linear power supply is low about 20-25% due to ohmic losses while that of SMPS is high, i.e. about 65-75%.

Additional Information

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