8-B-18: Power Supplies
8-18B1:
An advantage of resonant charging is that it:
Reduces the high-voltage power supply requirements.
Eliminates the need for a reverse current diode.
Guarantees perfectly square output pulses.
Maintains a constant magnetron output frequency.
8-18B2:
The characteristics of a field-effect transistor (FET) used in a modern RADAR switching power supply can be compared as follows:
“On” state compares to a pure resistor. “Off” state compares to a mechanical relay.
“On” state compares to a bipolar transistor. “Off” state compares to a 1-Megohm resistor.
“On” state compares to an low resistance inductor. “Off” state compares to a 10-Megohm resistor.
“On” state compares to a resistor. “Off” state compares to a capacitor.
8-18B3:
A pulse-width modulator in a switching power supply is used to:
Vary the duty cycle of the regulator switch to control the output voltage.
Provide the reference voltage for the regulator.
Vary the frequency of the switching regulator to control the output voltage.
Compare the reference voltage with the output voltage sample and produce an error voltage.
8-18B4:
In a fixed-frequency switching power supply, the pulse width of the switching circuit will increase when:
The load impedance decreases.
The load current decreases.
The output voltage increases.
The input voltage increases.
8-18B5:
A major consideration for the use of a switching regulator power supply over a linear regulator is:
The overall efficiency of a switching regulator is much higher than a linear power supply.
The switching regulator has better regulation.
The linear regulator does not require a transformer to step down AC line voltages to a usable level.
The switching regulator can be used in nearly all applications requiring regulated voltage.
8-18B6:
Which of the following characteristics are true of a power MOSFET used in a RADAR switching supply?
High input impedance; failure mode can be gate punch-through.
Low input impedance; failure mode can be gate punch-through.
High input impedance; failure mode can be thermal runaway.
Low input impedance; failure mode can be gate breakdown.
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