Question

In the circuit shown below,

If the switching frequency is 25 kHz, then the critical values of L and C are

• A. 5.12 mH and 120 $\mu F$
• B. 4.66 mH and 72 nF
• C. 5.83 mH and 10 nF
• D. 4.12 mH and 60 $\mu F$

Answer 1

The correct option is C 5.83 mH and 10 nF

This is buck converter circuit
The critical value of inductor $L_C$ is

$L_C=\frac{(1-\alpha )R}{2f}$

Where, $\alpha =\frac{V_o}{V_s}=\frac{5}{12}=0.4166$

Critical value of capacitance
$L_C=\frac{(1-0.4166)500}{2\times 25\times {10}^3}=5.83mH$

$C_c=\frac{1-\alpha }{16L_c{f}^2}=\frac{1-0.4166}{16\times 5.83\times {10}^{-3}\times {(25\times {10}^3)}^2}=10nF$