ISCET Power Supply Circuits and Voltage Regulation 2

Question 1

What is the primary advantage of a switching regulator over a linear regulator?

Accepted Answer

Higher power conversion efficiency

Answer

Simpler circuit design with fewer components

Answer

Lower output ripple voltage

Answer

Better noise and EMI performance

Question 2

In a center-tap full-wave rectifier, what minimum PIV rating must each diode have if the transformer secondary is 50V RMS (each half)?

Accepted Answer

70.7V

Answer

35.35V

Answer

50V

Answer

100V

Question 3

The output voltage of an LM317 adjustable positive voltage regulator is set by:

Accepted Answer

An external resistor divider network connected to the ADJ pin

Answer

An internal fixed bandgap reference with no external components

Answer

The magnitude of the unregulated input voltage

Answer

A single potentiometer connected between output and ground

Question 4

What does 'crowbar' overvoltage protection in a power supply do when it activates?

Accepted Answer

Triggers an SCR to short the output and blow a fuse

Answer

Opens the load circuit with a relay to protect connected equipment

Answer

Increases the switching frequency to reduce output voltage

Answer

Disconnects the input rectifier diodes

Question 5

Power dissipation in a linear series pass regulator is primarily determined by:

Accepted Answer

The voltage difference between input and output multiplied by load current

Answer

The transformer core loss and copper winding resistance

Answer

Forward voltage drop across the output filter diodes

Answer

ESR of the output filter capacitors

Question 6

Load regulation of a power supply is best defined as:

Accepted Answer

The change in output voltage from no-load to full-load conditions

Answer

The ripple voltage divided by the DC output voltage

Answer

The efficiency at rated full-load current

Answer

The output current capability at minimum input voltage

Question 7

In a switching power supply, the inductor's primary function during the switch off-time in a buck converter is to:

Accepted Answer

Act as an energy storage element that continues supplying current to the load

Answer

Block high-frequency switching noise from reaching the output

Answer

Step down the input voltage through transformer action

Answer

Provide a current path for the catch diode only