Power Electronics

Question 1

What are DC/DC Converters useful for?

Answer 1

• Voltage Supply in Automotive Power Nets or Server Farms

Question 2

What are inverters useful for?

Answer 2

For Supply of Multi Phase Machines

Question 3

What are the two sides of Power Electronics?

Answer 3

Control Engineering and High Power Side

Question 4

What is a half-bridge?

Answer 4

Two semi-conductor elements connected in Series

Question 5

What components does an Electrical Drive train consist of?

Answer 5

1. Grid
2. Filters
3. Converter
4. Load
5. Control Electronics
6. Signal Electronics

Question 6

What is the voltage and current in and ideal voltage source?

Answer 6

Voltage is fixed, current is arbtitrary

Question 7

What is line regulation?

Answer 7

{dV_out}/{dVi_in}

Question 8

What is the load regulation?

Answer 8

Change in output voltage for change in output current

Question 9

What effect does a voltage divider have on line regulation?

Answer 9

Reduces line regulation

Question 10

How can you decrease losses of a zener voltage regulator?

Answer 10

Add a transistor

Question 11

When are losses of MOSFET in a unipolar power output stage the maxiumum?

Answer 11

1/2 of short circuit current

Question 12

What are the top and bottom switch in a half bridge?

Answer 12

Top bridge series with load, bottom parallel

Question 13

What are two configurations for a half bridge and what are the voltage levels in each?

Answer 13

Top open and bottom closed: V = 0

Top closed and bottom open: V = V_in

Question 14

What happens if both transistors in a half bridge are open?

Answer 14

Short circuit

Question 15

What is line regulation for ideal voltage source?

Answer 15

0

Question 16

What is Load regulation for Ideal source?

Answer 16

0 ohms

Question 17

What is Line regulation for unloaded voltage source with resistance?

Answer 17

1

Question 18

What is load regulation for unloaded voltage source with resistance?

Answer 18

-R

Question 19

How can you tell that a MOSFET is in short circuit condition?

Answer 19

V_DS = 0 (Drain source voltage)

Question 20

How can be a MOSFET modelled as a swtich?

Answer 20

• Assume allowed voltage range
• Assume voltage drop can be neglected when conducting current

Question 21

What is an advantage of using half bridge?

Answer 21

Low losses

Question 22

What does 0 and 1 mean for switches?

Answer 22

0 is open 1 is closed

Question 23

What is an F bridge?

Answer 23

Half bridge with inductor and load

Question 24

What is PWM?

Answer 24

A method for providing input voltage to half bridge

Question 25

What is duty cycle?

Answer 25

Ratio of time where switch is closed to time where switch is open

Question 26

What are some modulation schemes?

Answer 26

• Time-Average model
• Pulse wave modulation
• Closed loop modulation

Question 27

What is an advantage of Closed loop modulation?

Answer 27

Is stable without knowing system dynamics

Question 28

What is a syncronous buck converter?

Answer 28

• Syncronous implies two active elements
• Initially lossless
• Low damping

Question 29

What is a boost converter?

Answer 29

A system that provides higher voltage than input

Question 30

What is an easy way to tell a system is syncronous?

Answer 30

Half-bridge with two switches present