Question:
The figure shows a straight-line approximation for the forward characteristics of a power diode. A continuous on-state current of 15 A is flowing through the diode.
What is the power loss in the diode?
The figure shows a straight-line approximation for the forward characteristics of a power diode. A continuous on-state current of 15 A is flowing through the diode.
What is the power loss in the diode?
What is the power loss in the diode?
Show Hint
Fit the straight line as V0 plus I times Ron using the two marked points on the graph, then multiply the voltage drop at 15 A by the current.
Updated On: Jul 20, 2026
- 32.8 W
- 21.2 W
- 18.6 W
- 23.1 W
Show Solution
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The Correct Option is C
Solution and Explanation
Step 1: Read the threshold voltage and slope from the graph.
The straight-line approximation crosses the voltage axis at \(V_0=1.0\) V, meaning the diode starts conducting only above this voltage, and it passes through the point where the on-state current is \(50\) A at an on-state voltage of \(1.8\) V.
Step 2: Find the slope of the line, which gives the inverse of the on-state resistance.
\[ \text{slope}=\frac{50-0}{1.8-1.0}=\frac{50}{0.8}=62.5\text{ A/V} \]
So the on-state resistance is
\[ R_{on}=\frac{1}{62.5}=0.016\ \Omega \]
Step 3: Write the diode's forward voltage as a function of its current.
\[ V_D=V_0+I\,R_{on} \]
Step 4: Substitute the given on-state current of 15 A.
\[ V_D=1.0+15\times0.016=1.0+0.24=1.24\text{ V} \]
Step 5: Compute the power loss.
Power loss is the product of the forward voltage drop and the current through the diode.
\[ P_{loss}=V_D\times I=1.24\times15=18.6\text{ W} \]
Step 6: Final conclusion.
\[ \boxed{18.6\text{ W}} \]
Hence the correct option is (C).
The straight-line approximation crosses the voltage axis at \(V_0=1.0\) V, meaning the diode starts conducting only above this voltage, and it passes through the point where the on-state current is \(50\) A at an on-state voltage of \(1.8\) V.
Step 2: Find the slope of the line, which gives the inverse of the on-state resistance.
\[ \text{slope}=\frac{50-0}{1.8-1.0}=\frac{50}{0.8}=62.5\text{ A/V} \]
So the on-state resistance is
\[ R_{on}=\frac{1}{62.5}=0.016\ \Omega \]
Step 3: Write the diode's forward voltage as a function of its current.
\[ V_D=V_0+I\,R_{on} \]
Step 4: Substitute the given on-state current of 15 A.
\[ V_D=1.0+15\times0.016=1.0+0.24=1.24\text{ V} \]
Step 5: Compute the power loss.
Power loss is the product of the forward voltage drop and the current through the diode.
\[ P_{loss}=V_D\times I=1.24\times15=18.6\text{ W} \]
Step 6: Final conclusion.
\[ \boxed{18.6\text{ W}} \]
Hence the correct option is (C).
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