DC-DC Converter

Q.1

A boost converter is also a step down converter because the output voltage is less than the input.

True
False

Q.2

A buck converter produces an output voltage that is ______than or equal to the input.

less
greater

Q.3

In a boost converter, inductor current (iL, dc) is ________ to output current (io).

equal
not equal

Q.4

For a buck converter, the circuit operation when switch is off are the following except:

(You are advised to draw out a circuit of buck converter to analyse the circuit operation.)

source current = inductor current
diode current = 0
diode voltage = source voltage
diode voltage = 0

Q.5

For a boost converter, the circuit operation when switch is on are the following except:

(You are advised to draw out a circuit of boost converter to analyse the circuit operation.)

source current = inductor current
capacitor current = load current
diode current = 0
inductor voltage = source voltage

Q.6

How is an inductor current defined as continuous current?

It returns to zero during each period.
It remains positive throughout the switching period.

Q.7

A buck converter has source voltage = 24 V, duty ratio = 0.65, Inductor = 25 micro henry, capacitor = 15 micro farad, switching frequency = 100k Hz and load resistance = 10 ohm. Determine the output voltage.

15.6 V
14.4 V
68.57 V

Q.8

From situation in question 7, determine the maximum and minimum inductor currents.

4.584 A, 0.617 A
13.097 A, 0.216 A
13.097 A, 0.617 A
4.584 A, 0.216 A

Q.9

From situation in question 7, determine the output voltage ripple.

0.04333 = 4.33 %
0.01667 = 1.167 %

Q.10

A boost converter has an output of 30V from a 12-V source. The output ripple voltage is to be less than one percent.the load resistance is 50 ohm and switching frequency is 25 kHz. Assuming that components are ideal. Determine the minimum capacitance required to limit the output ripple voltage to 1 percent in micro farad.

32
30
48
38