ISCET Power Supply Circuits and Voltage Regulation 3

Question 1

A boost (step-up) switching converter is required when:

Accepted Answer

The regulated output voltage must be higher than the unregulated input voltage

Answer

The regulated output voltage must be lower than the unregulated input voltage

Answer

Galvanic isolation between input and output is required

Answer

The load requires very low ripple current

Question 2

What effect does high ESR (Equivalent Series Resistance) in an output filter capacitor have on a power supply?

Accepted Answer

It adds to the output ripple voltage proportional to load current changes

Answer

It increases regulator efficiency by reducing switching losses

Answer

It reduces ripple voltage by providing additional damping

Answer

It improves transient response by slowing down the load step response

Question 3

In a flyback converter topology, energy is transferred from primary to secondary:

Accepted Answer

During the switch off-time when the primary switch opens

Answer

During the switch on-time when the primary is energized

Answer

Continuously regardless of the switch state

Answer

Only during resonant transitions at zero-crossing points

Question 4

Transformer voltage regulation (VR%) is calculated based on the change in secondary voltage between:

Accepted Answer

No-load and full-load conditions at rated input voltage

Answer

Full-load and maximum overload conditions

Answer

Minimum and maximum input voltage at constant load

Answer

Cold startup and steady-state thermal equilibrium

Question 5

In a three-terminal linear regulator circuit, what internal block compares the output sample voltage to the reference and drives the pass element?

Accepted Answer

The error amplifier

Answer

The pass transistor base driver

Answer

The internal zener reference diode alone

Answer

The thermal shutdown circuit

Question 6

Line regulation of a voltage regulator is a measure of:

Accepted Answer

How well output voltage is maintained as the input voltage varies

Answer

How well output voltage is maintained as the load current changes

Answer

The percentage ripple rejection at the switching frequency

Answer

The output impedance at DC versus AC frequencies

Question 7

When selecting a heat sink for a linear voltage regulator, the primary parameter used to size it correctly is:

Accepted Answer

The total power dissipated in the regulator package and the thermal resistance from junction to ambient

Answer

The regulator's output current rating only

Answer

The regulator's junction-to-case thermal resistance (θJC)

Answer

The switching frequency and duty cycle of the regulator