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Which of the following is NOT a valid characteristics of switched mode power supply as compared to linear power supply?

Which of the following is NOT a valid characteristics of switched mode power supply as compared to linear power supply? Correct Answer Low noise at output

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

PARAMETERS

LINEAR POWER SUPPLY

SWITCH MODE POWER SUPPLY (SMPS)

Definition

It completes the stepping down of AC voltage first then it converts it into DC.

It converts the AC input signal into DC first then it steps down the voltage up to the desired level.

Efficiency

Low efficiency i.e. about 20-25%

High Efficiency i.e. about 60-65%

Voltage Regulation

Voltage regulation is done by the voltage regulator.

Voltage regulation is done by the feedback circuit.

Magnetic material used

CRGO core is used

The ferrite core is used

Weight

It is bulky.

It is less bulky in comparison to the linear power supply.

Reliability

More reliable in comparison to SMPS.

Its reliability depends on the transistors used for switching

Complexity

Less complex than SMPS.

More complex than the Linear power supply.

Transient response

It possesses a faster response.

It possesses a slower response.

RF interference

No RF interference

RF shielding is required as switching produces more RF interference.

Noise and Electromagnetic interference

It is immune to noise and electromagnetic interference.

The effect of noise and electromagnetic interference is quite significant, thus EMI filters are required.

Applications

Used in Audio frequency applications and RF applications.

Used in chargers of mobile phones, DC motors, etc.

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