Power Electronics_Unit-IV_DC-DC Converters_Day to Day Assessment

Choppers are used to control the DC voltage level.

• True

• False

Answer explanation

Choppers are used to control the DC voltage level. They can increase, decrease or both the input DC voltage.

Which one of the following device is uncontrolled?

• SCR

• MOSFET

• Diode

• TRIAC

Answer explanation

Diode is uncontrolled, unidirectional power electronic device. When the voltage across the diode becomes positive it starts conduction otherwise remains off.

What is the formula for output voltage for Buck converter?

• 8D*Vin

• 5D*Vin

• 2D*Vin

• D*Vin

Answer explanation

The output voltage of the buck converter is V_o = D×V_in. The value of the duty cycle is less than one which makes the V_o < V_in. The buck converter is used to step down voltage. V_in is a fixed voltage and V_o is a variable voltage.

What is the formula for output voltage for Buck-Boost converter?

• D*Vin

• Vin/(1-D)

• D*Vin/(1-D)

• D*Vin/(1+D)

Answer explanation

The output voltage of the buck-boost converter is V_o = D×V_in ÷ (1-D). It can step up and step down the voltage depending upon the value of the duty cycle. If the value of the duty cycle is less than .5 it will work as a buck converter and for duty cycle greater than .5 it will work as a boost converter.

What is the formula for output voltage for Boost converter?

• 8D*Vin

• 5D*Vin

• 2D*Vin

• D*Vin

Answer explanation

The output voltage of the boost converter is V_o = V_in ÷ (1-D). The value of the duty cycle is less than one which makes the V_o > V_in. The boost converter is used to step up the voltage. V_in is a fixed voltage and V_o is a variable voltage.

Buck-Boost acts as Buck converter for duty cycle is equal to _________

• 0.9

• 0.7

• 0.6

• 0.4

Answer explanation

The output voltage of the buck-boost converter is V_o = D×V_in ÷ (1-D). It can step up and step down the voltage depending upon the value of the duty cycle. If the value of the duty cycle is less than .5 it will work as a buck converter. The answer is .4.

Buck-Boost acts as Boost converter for duty cycle is equal to _________

• 0.8

• 0.1

• 0.2

• 0.4

Answer explanation

The output voltage of the buck-boost converter is V_o = D×V_in ÷ (1-D). It can step up and step down the voltage depending upon the value of the duty cycle. If the value of the duty cycle is more than .5 it will work as a boost converter. The answer is .8.

Inductor and Capacitor in Buck converter are used to ___________

• Increase the cost

• Decrease the cost

• Filter out the harmonics

• Increase the Harmonics

Answer explanation

Inductor and capacitor in Buck converter are used to filter out the harmonics. They remove the ripple from the output voltage.

In the ___________ type of chopper, two stage conversions takes place.

• AC-DC

• AC link

• DC Link

• None of the mentioned

Choppers converts

• AC to DC

• DC to AC

• DC to DC

• AC to AC