Power supply design

Question 1

Name two methods of protecting circuits from excessive power supply voltages.

Answer 1

clamp diodes

crow-bar circuit

Question 2

What do transformer-based power supplies usually consist of?

Answer 2

A step-down transformer, a full-wave bridge rectifier and a smoothing capacitor

Question 3

What specs are usually given for a transformer?

Answer 3

windings ratio and a power rating in VA. To find max current do power rating VA / output voltage

Question 4

What are typical PWM switching frequencies?

Answer 4

10-500kHz

Question 5

What are some Pros and cons of switching power supplies?

Answer 5

For higher powers they are preferred choice. They can adapt easily and are very flexible. Disadvantages are that the quality is generally worse and reliability is worse

Question 6

What is the internal resistance of a typical PP3 battery?

Answer 6

2 ohms

Question 7

What is power dissipation in power supply?

Answer 7

Preg = (Vin - Vout) x I load

Question 8

What is the equation for a heatsink?

Answer 8

Thermal resistance between sink and ambient = ((Tj-Ta)/P)-Rjc