Power Diodes

What is the main function of a power diode? -

A diode allows current to flow in only one direction-from anode to cathode-while blocking current in the reverse direction.

What happens to current when a diode is forward biased? -

It conducts a large current with a small forward voltage drop.

What happens when a diode is reverse biased? -

Only a tiny leakage current flows until breakdown occurs.

What is the peak-inverse voltage (PIV) rating of a diode? -

The maximum reverse voltage the diode can withstand without breaking down.

How is power dissipation in a diode calculated? -

Power = forward voltage drop * forward current.

Why is switching time important for diodes? -

It determines how fast the diode can change from conducting to blocking; slower diodes are fine for 50-60 Hz, fast-recovery ones are used for high-frequency circuits.

What is a fast-recovery or high-speed diode? -

A diode designed with short reverse-recovery time so it can switch quickly in high-frequency applications such as PWM circuits.

Name three key diode ratings. -

(1) Power dissipation (2) Peak inverse voltage (3) Switching time.

What is a flyback or snubber diode used for? -

It provides a path for inductive current when a switch turns off, protecting components from voltage spikes.

Give examples of diode applications in power electronics. -

Rectifiers, clamping circuits, voltage multipliers, reverse-polarity protection, spike suppression, and solar-panel bypass diodes.

How does a Schottky diode differ from a normal silicon diode? -

It uses a metal-semiconductor junction, has lower forward voltage (approximately 0.3 V), and switches faster but handles lower reverse voltage.

Why are diodes used in rectifier circuits? -

They convert alternating current (AC) into pulsating direct current (DC) by conducting only during one half of each cycle.

Describe the I-V characteristic curve of a diode. -

The curve has three regions: (1) In forward bias, current rises sharply once the forward voltage exceeds about 0.7 V for silicon; (2) In reverse bias, only a small leakage current flows; (3) Beyond breakdown voltage, current rises rapidly in reverse direction.

What happens at the knee of the diode I-V curve? -

It's the point where the forward voltage is high enough that the diode begins to conduct heavily, marking the transition from non-conduction to conduction.

Describe how a diode behaves in forward and reverse bias on a graph. -

On a graph with voltage on the x-axis and current on the y-axis, the forward-bias region shows an exponential rise in current after the threshold; the reverse-bias region is nearly flat until breakdown.