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min corr to ex03
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wallscheid committed Nov 21, 2024
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2 changes: 1 addition & 1 deletion exercise/main.tex
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\documentclass[solution]{../course_template/exerciseClass}
\title{Power Electronics}

\includeonly{tex/exercise04}
\includeonly{tex/exercise03}

\begin{document}
\include{tex/exercise01}
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16 changes: 8 additions & 8 deletions exercise/tex/exercise03.tex
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As the output power is specified as a value range, the highest and lowest values can be used. The lowest and highest current should be determined from these two values, from which the value range of the frequency $f_\mathrm{s}$ can then be determined.
The average inductor current is calculated as:
\begin{equation}
\overline{i}_\mathrm{L}(P_\mathrm{2}=(\SI{2}{\watt}))= \frac{P_\mathrm{2}}{U_\mathrm{2}}\frac{1}{D}=\frac{\SI{2}{\watt}}{\SI{12}{\volt}}\frac{5}{3}=\SI{0.278}{\ampere},
\overline{i}_\mathrm{L}(P_\mathrm{2}=\SI{2}{\watt})= \frac{P_\mathrm{2}}{U_\mathrm{2}}\frac{1}{D}=\frac{\SI{2}{\watt}}{\SI{12}{\volt}}\frac{5}{3}=\SI{0.278}{\ampere},
\end{equation}
\begin{equation}
\overline{i}_\mathrm{L}(P_\mathrm{2}=(\SI{15}{\watt}))= \frac{P_\mathrm{2}}{U_\mathrm{2}}\frac{1}{D}=\frac{\SI{15}{\watt}}{\SI{12}{\volt}}\frac{5}{3}=\SI{2.0833}{\ampere}.
\overline{i}_\mathrm{L}(P_\mathrm{2}=\SI{15}{\watt})= \frac{P_\mathrm{2}}{U_\mathrm{2}}\frac{1}{D}=\frac{\SI{15}{\watt}}{\SI{12}{\volt}}\frac{5}{3}=\SI{2.0833}{\ampere}.
\end{equation}
With \eqref{eq:equation switching frequencies ex03} the resulting switching frequencies are:
\begin{equation}
f_\mathrm{s}(P_\mathrm{2}=(\SI{2}{\watt}))=\frac{0.4\cdot\SI{18}{\volt}}{\SI{86.4}{\micro\henry}\cdot 2\cdot \SI{0.278}{\ampere}}=\SI{150}{\kilo \hertz},
f_\mathrm{s}(P_\mathrm{2}=\SI{2}{\watt})=\frac{0.4\cdot\SI{18}{\volt}}{\SI{86.4}{\micro\henry}\cdot 2\cdot \SI{0.278}{\ampere}}=\SI{150}{\kilo \hertz},
\end{equation}
\begin{equation}
f_\mathrm{s}(P_\mathrm{2}=(\SI{15}{\watt}))=\frac{0.4\cdot\SI{18}{\volt}}{\SI{86.4}{\micro\henry}\cdot 2\cdot \SI{2.0833}{\ampere}}=\SI{20}{\kilo \hertz}.
f_\mathrm{s}(P_\mathrm{2}=\SI{15}{\watt})=\frac{0.4\cdot\SI{18}{\volt}}{\SI{86.4}{\micro\henry}\cdot 2\cdot \SI{2.0833}{\ampere}}=\SI{20}{\kilo \hertz}.
\end{equation}
The switching frequency $f_\mathrm{s}$ varies in the range from $\SI{20}{\kilo \hertz} \, \dots \, \SI{150}{\kilo \hertz}$ for the specified output power range in the task.
\end{solutionblock}
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T_\mathrm{s}(P_\mathrm{2}=\SI{2}{\watt}) =\frac{1}{f_{\mathrm{s,2W}}} = \frac{1}{\SI{150}{\kilo \hertz}}= \SI{6.67}{\micro \s},
\end{equation}
\begin{equation}
T_\mathrm{s}(P_\mathrm{2}=(\SI{15}{\watt})) =\frac{1}{f_{\mathrm{s,15W}}} = \frac{1}{\SI{20}{\kilo \hertz}}= \SI{50}{\micro \s}.
T_\mathrm{s}(P_\mathrm{2}=\SI{15}{\watt}) =\frac{1}{f_{\mathrm{s,15W}}} = \frac{1}{\SI{20}{\kilo \hertz}}= \SI{50}{\micro \s}.
\end{equation}
The transistor switch-on times can be determined using
\begin{equation}
T_\mathrm{on} = D T_\mathrm{s} \label{absolut value switch-on-times}
\end{equation}
leading to:
\begin{equation}
T_\mathrm{on}(P_\mathrm{2}=(\SI{2}{\watt})) = 0.4 \cdot \SI{6.67}{\micro \s} = \SI{2.67}{\micro \s},
T_\mathrm{on}(P_\mathrm{2}=\SI{2}{\watt}) = 0.4 \cdot \SI{6.67}{\micro \s} = \SI{2.67}{\micro \s},
\end{equation}
\begin{equation}
T_\mathrm{on}(P_\mathrm{2}=(\SI{15}{\watt})) = 0.4 \cdot \SI{50}{\micro \s}= \SI{20}{\micro \s}.
T_\mathrm{on}(P_\mathrm{2}=\SI{15}{\watt}) = 0.4 \cdot \SI{50}{\micro \s}= \SI{20}{\micro \s}.
\end{equation}
\end{solutionblock}

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\end{equation}
applying for the maximum power ($P = \SI{15}{\watt}$) results into:
\begin{equation}
C_2 = \frac{I_{\mathrm{2}}(P_\mathrm{2}=(\SI{15}{\watt})) D T_{\mathrm{s}}(P_\mathrm{2}=(\SI{15}{\watt}))}{\Delta u_{\mathrm{C}}}
C_2 = \frac{I_{\mathrm{2}}(P_\mathrm{2}=\SI{15}{\watt}) D T_{\mathrm{s}}(P_\mathrm{2}=\SI{15}{\watt})}{\Delta u_{\mathrm{C}}}
= \frac{\SI{1.25}{\ampere} \cdot 0.4 \cdot \SI{50}{\micro\second}}{\SI{0.24}{\volt}}
= \SI{104}{\micro\farad}.
\end{equation}
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