diff --git a/exercise/fig/ex04/FigTab_ForwardConverterWithAsymHalfBridge.tex b/exercise/fig/ex04/FigTab_ForwardConverterWithAsymHalfBridge.tex index 7e3b58a..e31bb29 100644 --- a/exercise/fig/ex04/FigTab_ForwardConverterWithAsymHalfBridge.tex +++ b/exercise/fig/ex04/FigTab_ForwardConverterWithAsymHalfBridge.tex @@ -8,7 +8,7 @@ \toprule Input voltage: & $U_{\mathrm{1}} = \SI{325}{\volt}$ & Output voltage: & $U_{\mathrm{2}} = \SI{15}{\volt}$ \\ Output power: & $P_{\mathrm{2}} = \SI{50}{\watt}$ & Switching frequency: & $f_{\mathrm{s}} = \SI{50}{\kilo\hertz}$ \\ - Turns ration: & $N_{\mathrm{1}}/N_{\mathrm{2}}=10$ & Magnetizing inductance: & $L_{\mathrm{m}}=\SI{2}{\milli\henry}$ \\ + Turns ratio: & $N_{\mathrm{1}}/N_{\mathrm{2}}=10$ & Magnetizing inductance: & $L_{\mathrm{m}}=\SI{2}{\milli\henry}$ \\ \bottomrule \end{tabular} \caption{Parameter overview of the circuit.} diff --git a/exercise/fig/ex04/FigTab_SingledEndedForwardConverter.tex b/exercise/fig/ex04/FigTab_SingledEndedForwardConverter.tex index 3066e37..6052127 100644 --- a/exercise/fig/ex04/FigTab_SingledEndedForwardConverter.tex +++ b/exercise/fig/ex04/FigTab_SingledEndedForwardConverter.tex @@ -6,7 +6,7 @@ \centering % Zentriert die Tabelle \begin{tabular}{llll} \toprule - Input voltage: & $U_{\mathrm{1}} = \SI{240}{\volt}$...$\SI{360}{\volt}$ & Switching frequency: & $f_{\mathrm{s}} = \SI{48}{\kilo\hertz}$\\ + Input voltage: & $U_{\mathrm{1}} = \SI{240}{\volt}\ldots\SI{360}{\volt}$ & Switching frequency: & $f_{\mathrm{s}} = \SI{48}{\kilo\hertz}$\\ Forward voltage of $D_{\mathrm{1}}$: & $U_{\mathrm{D1,f}} = \SI{0.4}{\volt}$ & & \\ \bottomrule \end{tabular} diff --git a/exercise/fig/ex04/Fig_SingledEndedForwardConverter.tex b/exercise/fig/ex04/Fig_SingledEndedForwardConverter.tex index 7a8ea9e..aaacf81 100644 --- a/exercise/fig/ex04/Fig_SingledEndedForwardConverter.tex +++ b/exercise/fig/ex04/Fig_SingledEndedForwardConverter.tex @@ -16,9 +16,7 @@ % Add junction for diode D3 (jLTv) ++ (0,-2) coordinate (jD3k) % Add inductor LTv - (jD3k) to [L,l=$L_\mathrm{3}$,n=L1,v_<=$U_\mathrm{3}$, voltage shift=0.5, voltage=straight] (jLTv) - % Add winding text - (jD3k) node[right] {$N_\mathrm{3}$}; + (jD3k) to [L,l=$N_\mathrm{3}$,n=L1,v_<=$U_\mathrm{3}$, voltage shift=0.5, voltage=straight] (jLTv); \path (L1.ul dot) node[circ]{}; \draw % Add arrow and Text @@ -52,9 +50,7 @@ % Assign Transistor drain junction to primary junction point (jTd) coordinate (jLtpg) % Add transformer primary inductor with voltage arrow - (jLtpv) to [L,l_=$L_\mathrm{1}$, n=Ltp, v_=$U_\mathrm{p}$,voltage shift=5, voltage=straight] ++(0,-2) coordinate (jLtpg) - % Add turn name of primary inductor - (jLtpg) node[left] {$N_\mathrm{1}$} + (jLtpv) to [L,l_=$N_\mathrm{1}$, n=Ltp, v_=$U_\mathrm{p}$,voltage shift=5, voltage=straight] ++(0,-2) coordinate (jLtpg) % Add junctions for secondary inductor (jLtpv) ++(0.8,0) coordinate (jLtsv) (jLtpg) ++(0.8,0) coordinate (jLtsg); @@ -83,7 +79,7 @@ % Add diode D2 (jD2a) to [D,l^=$D_\mathrm{2}$] (jD2k) % Add inductor L4 - (jD2k) to [L,l=$L_\mathrm{4}$,n=L1] ++(3,0) coordinate (jU2v) + (jD2k) to [L,l=$L$,n=L1] ++(3,0) coordinate (jU2v) % Add arrow and Text (jD2k) ++(0.5,0) node[currarrow](IL){} (IL) node[anchor=south,color=black]{$i_\mathrm{L}$} diff --git a/exercise/main.tex b/exercise/main.tex index 13e9136..8e193ed 100644 --- a/exercise/main.tex +++ b/exercise/main.tex @@ -1,4 +1,4 @@ -\documentclass[solution]{../course_template/exerciseClass} +\documentclass[]{../course_template/exerciseClass} \title{Power Electronics} \includeonly{tex/exercise04} diff --git a/exercise/tex/exercise04.tex b/exercise/tex/exercise04.tex index d4d5d78..26cafdc 100644 --- a/exercise/tex/exercise04.tex +++ b/exercise/tex/exercise04.tex @@ -8,7 +8,7 @@ %% Task 1: Flyback converter %% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \task{Flyback converter} -A flyback converter with an input voltage range $U_\mathrm{1} = \SI{300}{\volt} \, \dots \, \SI{900}{\volt}$ is used to supply a control electronics unit. The converter delivers a rated output power of $P_\mathrm{2} = \SI{30}{\watt}$ at a regulated (constant) output voltage of $U_\mathrm{2} = \SI{15}{\volt}$. The flyback converter is operated in discontinuous current mode with a constant frequency of $f_\mathrm{s} = \SI{50}{\kilo\hertz}$. The turns ratio of the transformer is $N_\mathrm{1}/N_\mathrm{2}=60/12$, the magnetizing inductance on the primary side is $L_\mathrm{m} = \SI{760}{\micro\henry}$. The coupling between the primary and secondary windings is ideal and the converter operates in steady state. +A flyback converter with an input voltage range $U_\mathrm{1} = \SI{300}{\volt} \, \dots \, \SI{900}{\volt}$ is used to supply a control electronics unit. The converter delivers a rated output power of $P_\mathrm{2} = \SI{30}{\watt}$ at a regulated (constant) output voltage of $U_\mathrm{2} = \SI{15}{\volt}$. The flyback converter is operated in discontinuous conduction mode with a constant frequency of $f_\mathrm{s} = \SI{50}{\kilo\hertz}$. The turns ratio of the transformer is $N_\mathrm{1}/N_\mathrm{2}=60/12$, the magnetizing inductance on the primary side is $L_\mathrm{m} = \SI{760}{\micro\henry}$. The coupling between the primary and secondary windings is ideal and the converter operates in steady state. \input{./fig/ex04/Fig_FlybackConverter.tex} @@ -26,7 +26,7 @@ \label{table:ex04_Parameters of the circuit} \end{table} -\subtask{The input voltage is $U_\mathrm{1}=\SI{760}{\volt}$ at rated power at the output. What is the peak value $\hat i_\mathrm{1}$ of the primary current $i_\mathrm{1}$? What is the peak value $\hat i_\mathrm{2}$ of the secondary current $i_\mathrm{2}$? Calculate the duty cycle of the transistor for this operating case.} +\subtask{The input voltage is $U_\mathrm{1}=\SI{760}{\volt}$ at rated power at the output. What is the peak value $\hat i_\mathrm{1}$ of the primary current $i_\mathrm{1}$? What is the peak value $\hat i_\mathrm{2}$ of the secondary current $i_\mathrm{2}$? Calculate the duty cycle of the transistor for this operating point.} \begin{solutionblock}s To determine the current $\hat I_\mathrm{1}$, the equation for determining the output power \eqref{eq:output power ex04} is primarily used. The unknown energy of the inductance of the primary winding side \eqref{eq:energy primary inductance ex04} is inserted into this equation. @@ -65,14 +65,17 @@ \end{solutionblock} -\subtask{The input voltage is $U_\mathrm{1}=\SI{382}{\volt}$ at nominal load. Calculate and sketch the following voltage and current curves for this operating case over one cycle period: $u_\mathrm{T}(t), u_\mathrm{s}(t), i_\mathrm{2}(t), i_\mathrm{1}(t)$. $u_\mathrm{T}(t)$ is the voltage that drops across the transistor and $u_\mathrm{s}(t)$ is the voltage on the secondary side of the transformer.} +\subtask{The input voltage is $U_\mathrm{1}=\SI{382}{\volt}$ at nominal load. Calculate and sketch the following voltage and current curves for this operating case over one cycle period: $u_\mathrm{T}(t), u_\mathrm{s}(t), i_\mathrm{2}(t), i_\mathrm{1}(t)$. Here, $u_\mathrm{T}(t)$ is the transistor voltage and $u_\mathrm{s}(t)$ is the voltage on the secondary side of the transformer.} + +\begin{solutionblock} + \input{./fig/ex04/Fig_voltageTransistorPeriodTask1.tex} + \input{./fig/ex04/Fig_voltageUsPeriodTask1.tex} + \input{./fig/ex04/Fig_currentI2PeriodTask1.tex} + \input{./fig/ex04/Fig_currentI1PeriodTask1.tex} +\end{solutionblock} -\input{./fig/ex04/Fig_voltageTransistorPeriodTask1.tex} -\input{./fig/ex04/Fig_voltageUsPeriodTask1.tex} -\input{./fig/ex04/Fig_currentI2PeriodTask1.tex} -\input{./fig/ex04/Fig_currentI1PeriodTask1.tex} -\subtask{The input voltage is $U_\mathrm{1}=\SI{382}{\volt}$ at nominal load. Determine the mean value $\overline i_\mathrm{T}$ and the RMS current $I_\mathrm{T}$ through the transistor. Also, determine the mean value $\overline i_\mathrm{D}$ and the RMS current $I_\mathrm{D}$ through the diode. What is the maximum reverse voltage load $u_\mathrm{T, max}$ of the transistorans $u_\mathrm{D, max}$ of the diode?} +\subtask{Determine the mean value $\overline i_\mathrm{T}$ and the RMS current $I_\mathrm{T}$ through the transistor. Also, determine the mean value $\overline i_\mathrm{D}$ and the RMS current $I_\mathrm{D}$ through the diode. What is the maximum reverse voltage load $u_\mathrm{T, max}$ of the transistor and $u_\mathrm{D, max}$ of the diode? Consider the same operation conditions as in the previous subtask.} \begin{solutionblock} \begin{equation} \overline{i}_\mathrm{T} = \frac{1}{T_\mathrm{S}}\frac{1}{2}\hat I_\mathrm{1}T_\mathrm{on}=\frac{1}{\SI{20}{\micro\s}}\cdot\frac{1}{2}\SI{1.257}{\ampere}\cdot\SI{2.5}{\micro\s}=\SI{78.53}{\milli\ampere} @@ -102,7 +105,7 @@ \end{solutionblock} -\subtask{The input voltage is $U_\mathrm{1}=\SI{382}{\volt}$ at nominal load. How much energy is transferred from the input to the output per switching period $\Delta E$ and what is the resulting average power $P$ considering the duty cycle value from subtask 1.2? What happens if there is no ideal voltage source on the output side but an unloaded capacitor and the circuit is operated with $D>0$?} +\subtask{How much energy is transferred from the input to the output per switching period $\Delta E$ and what is the resulting average power $P$ (consider the same operation conditions as in the previous subtask)? What happens if there is no ideal voltage source on the output side but an unloaded capacitor and the circuit is operated with $D>0$?} \begin{solutionblock} @@ -128,14 +131,13 @@ The converter operates in steady-state conditions. Both transistors are controlled by the same signal. \subtask{At what duty cycle $D$ does the circuit operate?} -\subtask{Calculate the average value of $\overline{i_\mathrm{2}}$ and $\overline{i_\mathrm{1}}$ over a switching cycle, - assuming ideal filtering of $i_\mathrm{2}$.} -\subtask{Calculate the peak value of $\hat{i}_\mathrm{m}$ the magnetizing current $i_\mathrm{m}$.} -\subtask{Sketch the waveforms of $u_\mathrm{p}$, $i_\mathrm{m}$, $i_\mathrm{p}$ and $i_\mathrm{1}$ - considering switching-induced ripples.} -\subtask{Calculate the minimal necessary input voltage $U_\mathrm{1}$, if the output voltage $U_\mathrm{2}$ = \SI{20}{\volt} shall being constant.} -\subtask{Calculate the inductance of $L$,such that the ripple current $\Delta i_\mathrm{2}$ is to be $\SI{10}{\percent}$ of the - average output current $\overline{I_\mathrm{2}}$?} +\subtask{Calculate the average currents $\overline{i}_\mathrm{2}$ and $\overline{i}_\mathrm{1}$ over a switching cycle assuming ideal filtering of $i_\mathrm{2}$.} +\subtask{Calculate the peak value $\hat{i}_\mathrm{m}$ of the magnetizing current $i_\mathrm{m}$.} +\subtask{Sketch the signals $u_\mathrm{p}$, $i_\mathrm{m}$, $i_\mathrm{p}$ and $i_\mathrm{1}$ + considering the switching-induced ripples.} +\subtask{Calculate the minimal necessary input voltage $U_\mathrm{1}$, if $U_\mathrm{2}$ = \SI{20}{\volt} shall being constant.} +\subtask{Determine $L$ such that the ripple current $\Delta i_\mathrm{2}$ is $\SI{10}{\percent}$ of the + average output current $\overline{i}_\mathrm{2}$.} @@ -145,30 +147,28 @@ \task{Singled-ended forward converter (demagnetization winding)} -The power supply of a data processing system shall be realized by a singled-ended forward converter as shown in \autoref{fig:ex04_SingledEndedForwardConverter}. +The power supply of a data processing system shall be realized by a singled-ended forward converter. \input{./fig/ex04/Fig_SingledEndedForwardConverter} The parameters are listed in \autoref{table:Ex04_Parameters of the singled ended forward converter.}. -The output inductance $L_\mathrm{4}$ is dimensioned so that the current $i_\mathrm{L4}$ exhibits a continuous waveform. +The output inductance $L$ is dimensioned so that the current $i_\mathrm{L}$ exhibits a continuous waveform. The transformer's leakage inductance can be neglected. \input{./fig/ex04/FigTab_SingledEndedForwardConverter} -\subtask{Calculate the turns ratio $N_\mathrm{3}$/$N_\mathrm{1}$ so that the maximum blocking voltage - across the transistor during demagnetization is $\SI{600}{\volt}$.} +\subtask{Calculate the turns ratio $N_\mathrm{3}$/$N_\mathrm{1}$ limiting the maximum transistor blocking voltage + to $\SI{600}{\volt}$.} \subtask{What is the maximum permissible duty cycle of the power transistor in this case?} \subtask{What turns ratio $N_\mathrm{1}$/$N_\mathrm{2}$ should be chosen to achieve the required secondary voltage?} -\subtask{Does the steady-state duty cycle of the transistor need to be adjusted when the output power changes? - Over what range must the transistor's duty cycle be adjustable, considering the input voltage range?} +\subtask{Does the duty cycle need to be adjusted when the output power changes? + Over what range must the duty cycle be adjustable, considering the input voltage range?} \subtask{What are the resulting maximum blocking voltages of the diodes $D_\mathrm{1}$ and $D_\mathrm{2}$?} -\subtask{What should be the value of the primary inductance $L_\mathrm{1}$ to ensure - that the peak value of the magnetizing current remains below $\SI{10}{\percent}$ of the current $\overline{i_\mathrm{L4'}}$. - The current $\overline{i_\mathrm{L4'}}$ corresponds to the average current $\overline{i_\mathrm{L4}}$ through the output inductance - at a nominal load of $P_2=\SI{125}{\watt}$, which is translated to the primary side.} -\subtask{Sketch the waveform of the voltage across the power transistor, the current through the demagnetization +\subtask{Determine the magnetizing inductance $L_\mathrm{m}$ to ensure + that the peak value of the magnetizing current remains below $\SI{10}{\percent}$ of the $\overline{i}'_\mathrm{L}$, which corresponds to the average current $\overline{i}_\mathrm{L}$ through the output inductance translated to the primary side + at a nominal load of $P_2=\SI{125}{\watt}$.} +\subtask{Sketch the signals of the voltage across the power transistor, the current through the demagnetization winding, and the current through the freewheeling diode $D_\mathrm{2}$ for $U_\mathrm{1}=\SI{240}{\volt}$ and $U_\mathrm{1}=\SI{360}{\volt}$.} -\subtask{Calculate the peak value of the magnetizing current for each case. Consider the current in the output - inductor as ideally filtered.} +\subtask{Calculate the peak magnetizing current for each case assuming a constant output current.} \subtask{Could a higher power be transferred by doubling the switching frequency of the converter?} \ No newline at end of file diff --git a/lecture/main.ist b/lecture/main.ist index 9594f6a..05ab55c 100644 --- a/lecture/main.ist +++ b/lecture/main.ist @@ -1,5 +1,5 @@ % makeindex style file created by the glossaries package -% for document 'main' on 2024-11-25 +% for document 'main' on 2024-11-26 actual '?' encap '|' level '!' diff --git a/lecture/main.nom b/lecture/main.nom index 39669d6..e69de29 100644 --- a/lecture/main.nom +++ b/lecture/main.nom @@ -1,16 +0,0 @@ -\glossarysection[\glossarytoctitle]{\glossarytitle}\glossarypreamble -\begin{theglossary}\glossaryheader -\glsgroupheading{glsnumbers}\relax \glsresetentrylist % -\glossentry{scalar_signal}{\glossaryentrynumbers{\relax - \setentrycounter[]{page}\glsignore{209}}}% -\glossentry{vectorial_signal}{\glossaryentrynumbers{\relax - \setentrycounter[]{page}\glsignore{209}}}% -\glossentry{const_signal}{\glossaryentrynumbers{\relax - \setentrycounter[]{page}\glsignore{209}}}% -\glossentry{matrix}{\glossaryentrynumbers{\relax - \setentrycounter[]{page}\glsignore{209}}}% -\glossentry{average_signal}{\glossaryentrynumbers{\relax - \setentrycounter[]{page}\glsignore{209}}}% -\glossentry{derivative_signal}{\glossaryentrynumbers{\relax - \setentrycounter[]{page}\glsignore{209}}}% -\end{theglossary}\glossarypostamble diff --git a/lecture/main.tex b/lecture/main.tex index 0222e41..0cf015f 100644 --- a/lecture/main.tex +++ b/lecture/main.tex @@ -5,7 +5,7 @@ \author{Oliver Wallscheid} \date{} -%\includeonly{tex/Lecture04} % build only selected sections +\includeonly{tex/Lecture03} % build only selected sections \begin{document} diff --git a/lecture/tex/Lecture03.tex b/lecture/tex/Lecture03.tex index e968397..c476d35 100644 --- a/lecture/tex/Lecture03.tex +++ b/lecture/tex/Lecture03.tex @@ -1115,13 +1115,13 @@ \subsection{Forward converter} Assumption: \begin{itemize} \item The transformer is ideal and does not exhibit a magnetizing inductance. - \end{itemize} + \end{itemize}\pause Consequence: \begin{itemize} - \item The transformer's secondary output voltage $u_\mathrm{s}(t)$ is a $\nicefrac{N_2}{N_1}$ scaled version of the standard buck converter's switch voltage (compare \figref{fig:step-down-converter-realization-1Q}). + \item The transformer's secondary output voltage $u_\mathrm{s}(t)$ is a $\nicefrac{N_2}{N_1}$ scaled version of the standard buck converter's switch voltage (compare \figref{fig:step-down-converter-realization-1Q}). \pause \item The (idealized) forward converter characteristics are analogous to the buck converter. - \end{itemize} - Hence, the voltage input-to-output voltage ratios for the (idealized) forward converter are: + \end{itemize} \pause + Hence, the \hl{voltage input-to-output voltage ratios for the (idealized) forward converter} are: \begin{equation} \mbox{CCM:}\quad \frac{U_2}{U_1} = \frac{N_2}{N_1}D, \qquad \mbox{DCM:}\quad U_2 = \frac{N_2^2}{N_1^2}\frac{D^2T_\mathrm{s}U_1^2}{D^2T_\mathrm{s}\frac{N_2}{N_1}U_1+2L\overline{i}_2}. \end{equation} @@ -1272,14 +1272,14 @@ \subsection{Forward converter} \edef\AddPlot{\noexpand\addplot[signalblue, thick] coordinates {({0 + #1},0) ({0 + #1},1) ({\D + #1},1) ({\D + #1},0) ({1 + #1},0) ({1 + #1},1)};} \AddPlot } - \draw[signalblue, thick, dashed, visible on=<2->] (axis cs:0, \D) -- (axis cs:4, \D); % dashed line at U_2 (average) - \node[above, inner sep = 2pt, anchor = south, visible on=<2->] at (axis cs:1.5+\D/2, \D) {$U_2$}; % label U_2 + \draw[signalblue, thick, dashed] (axis cs:0, \D) -- (axis cs:4, \D); % dashed line at U_2 (average) + \node[above, inner sep = 2pt, anchor = south] at (axis cs:1.5+\D/2, \D) {$U_2$}; % label U_2 \draw [thick,<->] (0.0,-0.2) -- node[below]{$T_\mathrm{on}$}(\D, -0.2); \draw [thick,<->] (\D,-0.2) -- node[below]{$T_\mathrm{off}$}(1, -0.2); % Bottom plot: magnetizing current - \nextgroupplot[ylabel = {$i_\mathrm{m}(t)$}, xlabel={$t/T_\mathrm{s}$}, ytick = {0, 0.5, 1}, yticklabels = {0, ,}, visible on=<7->] + \nextgroupplot[ylabel = {$i_\mathrm{m}(t)$}, xlabel={$t/T_\mathrm{s}$}, ytick = {0, 0.5, 1}, yticklabels = {0, ,}] \pgfplotsinvokeforeach{0,...,3}{ \edef\AddPlot{\noexpand\addplot[signalred, thick] coordinates {({0 + #1},0) ({\D + #1},0.6) ({2*\D + #1},0) ({1 + #1},0)};} \AddPlot @@ -1301,13 +1301,13 @@ \subsection{Forward converter} -U_1, & t\in[kT_\mathrm{s}+D T_\mathrm{s}, kT_\mathrm{s}+2D T_\mathrm{s}], \quad T_1=T_2=\mathrm{off},\\ 0, & t\in[kT_\mathrm{s}+2D T_\mathrm{s}, kT_\mathrm{s}+T_\mathrm{s}], \quad T_1=\mathrm{on},\, T_2=\mathrm{off}. \end{cases} - \end{equation} + \end{equation}\pause Consequently, we have \begin{equation} \overline{u}_\mathrm{L_\mathrm{m}} = \frac{1}{T_\mathrm{s}}\int_{0}^{T_\mathrm{s}}u_\mathrm{p}(t)\mathrm{d}t = 0 \label{eq:average_magnetizing_voltage_asym_half-bridge_forward_converter} \end{equation} - and, therefore, the transformer's magnetizing current $i_\mathrm{m}(t)$ does not increase during a pulse period. However, this also limits the applicable duty cycle to + and, therefore, the transformer's magnetizing current $i_\mathrm{m}(t)$ does not increase during a pulse period.\pause However, this also \hl{limits the applicable duty cycle} to $$ D\leq\frac{1}{2} $$ @@ -1364,7 +1364,7 @@ \subsection{Forward converter} (l2.midtap) node[right]{$N_2$}; \draw[double, double distance=3pt, thick] let \p1=(l1.core west), \p2=(l2.core east) in (\x1/2+\x2/2, \y1) -- (\x1/2+\x2/2, \y2); \end{circuitikz} - \caption{Forward converter topology with an full-bridge} + \caption{Forward converter topology with a full-bridge} \label{fig:forward_converter_topology_asymmetrical_full_bridge} \end{figure} \end{frame} @@ -1397,14 +1397,14 @@ \subsection{Forward converter} \edef\AddPlot{\noexpand\addplot[signalblue, thick] coordinates {({0 + #1},0) ({0 + #1},1) ({\D + #1},1) ({\D + #1},0) ({1 + #1},0) ({1 + #1},1)};} \AddPlot } - \draw[signalblue, thick, dashed, visible on=<2->] (axis cs:0, \D) -- (axis cs:4, \D); % dashed line at U_2 (average) - \node[above, inner sep = 2pt, anchor = south, visible on=<2->] at (axis cs:1.5+\D/2, \D) {$U_2$}; % label U_2 + \draw[signalblue, thick, dashed] (axis cs:0, \D) -- (axis cs:4, \D); % dashed line at U_2 (average) + \node[above, inner sep = 2pt, anchor = south] at (axis cs:1.5+\D/2, \D) {$U_2$}; % label U_2 \draw [thick,<->] (0.0,-0.2) -- node[below]{$T_\mathrm{on}$}(\D, -0.2); \draw [thick,<->] (\D,-0.2) -- node[below]{$T_\mathrm{off}$}(1, -0.2); % Bottom plot: magnetizing current - \nextgroupplot[ylabel = {$i_\mathrm{m}(t)$}, xlabel={$t/T_\mathrm{s}$}, ytick = {-0.5, 0, 0.5}, yticklabels = {, 0,}, ymin = -0.6, ymax =0.6, visible on=<7->] + \nextgroupplot[ylabel = {$i_\mathrm{m}(t)$}, xlabel={$t/T_\mathrm{s}$}, ytick = {-0.5, 0, 0.5}, yticklabels = {, 0,}, ymin = -0.6, ymax =0.6] \pgfplotsinvokeforeach{0,...,3}{ \edef\AddPlot{\noexpand\addplot[signalred, thick] coordinates {({0 + #1},-0.3) ({\D + #1},0.3) ({1/2 + #1},0.3) ({1/2+\D + #1},-0.3) ({1 + #1},-0.3)};} \AddPlot @@ -1513,11 +1513,11 @@ \subsection{Forward converter} the duty cycle also remains limited to $$ D\leq\frac{1}{2} . - $$ + $$\pause However, the full-bridge realization comes with distinct differences compared to the asym. half-bridge: \begin{itemize} - \item Utilizes magnetic core more efficiently, i.e., core can be made smaller or less winding turns are required. - \item Effective switching frequency is doubled allowing for smaller filter components. + \item Utilizes magnetic core more efficiently, i.e., core can be made smaller or less winding turns are required. \pause + \item Effective switching frequency is doubled allowing for smaller filter components. \pause \item Obvious disadvantage: more complex input stage (costs). \end{itemize} \end{frame} @@ -1527,7 +1527,7 @@ \subsection{Forward converter} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \begin{frame}[b] \frametitle{Forward converter with additional demagnetization winding} - Alternative: transfer the idea of the flyback converter and add another winding $N_3$ to the transformer with reversed polarity. When $T$ blocks, the energy stored in the transformer's magnetic field is inherited by $N_3$ and transferred back to the input. + Alternative: \hl{transfer the idea of the flyback converter} and add another winding $N_3$ to the transformer with reversed polarity. When $T$ blocks, the energy stored in the transformer's magnetic field is inherited by $N_3$ and transferred back to the input. \begin{figure} \begin{circuitikz}[] %primary side @@ -1597,8 +1597,8 @@ \subsection{Forward converter} \edef\AddPlot{\noexpand\addplot[signalblue, thick] coordinates {({0 + #1},0) ({0 + #1},1) ({\D + #1},1) ({\D + #1},0) ({1 + #1},0) ({1 + #1},1)};} \AddPlot } - \draw[signalblue, thick, dashed, visible on=<2->] (axis cs:0, \D) -- (axis cs:4, \D); % dashed line at U_2 (average) - \node[above, inner sep = 2pt, anchor = south, visible on=<2->] at (axis cs:1.5+\D/2, \D) {$U_2$}; % label U_2 + \draw[signalblue, thick, dashed] (axis cs:0, \D) -- (axis cs:4, \D); % dashed line at U_2 (average) + \node[above, inner sep = 2pt, anchor = south] at (axis cs:1.5+\D/2, \D) {$U_2$}; % label U_2 \draw [thick,<->] (0.0,-0.2) -- node[below]{$T_\mathrm{on}$}(\D, -0.2); \draw [thick,<->] (\D,-0.2) -- node[below]{$T_\mathrm{off}$}(1, -0.2); @@ -1634,15 +1634,15 @@ \subsection{Forward converter} \begin{equation} \max\{i_\mathrm{m}(t)\} = i_\mathrm{m}(t=(k+D)T_\mathrm{s}) = \frac{U_1}{L_\mathrm{m}}DT_\mathrm{s} \end{equation} - which is reached at the end of the turn-on time $T_\mathrm{on}$. After switching off the transistor, the winding $N_3$ takes over the magnetizing current leading to + which is reached at the end of the turn-on time $T_\mathrm{on}$.\pause After switching off the transistor, the winding $N_3$ takes over the magnetizing current leading to \begin{equation} \max\{|i_\mathrm{3}(t)|\} = |i_3(t=(k+D)T_\mathrm{s})| = \frac{N_1}{N_3}\max\{i_\mathrm{m}(t)\} = \frac{N_1}{N_3}\frac{U_1}{L_\mathrm{m}}DT_\mathrm{s}. - \end{equation} + \end{equation}\pause To ensure that $i_\mathrm{m}(t=kT_\mathrm{s})=0$ holds at the next switch-on event, the voltage balance regarding the magnetizing inductance must be zero: \begin{equation} - \overline{u}_\mathrm{L_\mathrm{m}} = \frac{1}{T_\mathrm{s}}\int_{0}^{T_\mathrm{s}}u_\mathrm{p}(t)\mathrm{d}t = U_1 D T_\mathrm{s} - \frac{N_1}{N_3} U_1 T_\mathrm{m} =0 - \end{equation} - Here, $T_\mathrm{m}$ denotes the demagnetization time interval which results in + \overline{u}_\mathrm{L_\mathrm{m}} = \frac{1}{T_\mathrm{s}}\int_{0}^{T_\mathrm{s}}u_\mathrm{p}(t)\mathrm{d}t = U_1 D T_\mathrm{s} - \frac{N_1}{N_3} U_1 T_\mathrm{m} =0 . + \end{equation}\pause + Here, $T_\mathrm{m}$ denotes the \hl{demagnetization time interval} which results in \begin{equation} T_\mathrm{m} = \frac{N_3}{N_1}DT_\mathrm{s}. \label{eq:forward_converter_demagnetization_time_interval} @@ -1658,16 +1658,16 @@ \subsection{Forward converter} \begin{equation} T_\mathrm{m} \leq (1-D)T_\mathrm{s}. \label{eq:forward_converter_demagnetization_time_interval_threshold} - \end{equation} + \end{equation}\pause Combining \eqref{eq:forward_converter_demagnetization_time_interval} and \eqref{eq:forward_converter_demagnetization_time_interval_threshold} yields \begin{equation} \frac{N_3}{N_1} \leq \frac{1-D}{D} \quad \Leftrightarrow \quad D \leq \frac{N_1}{N_1+N_3} \label{eq:forward_converter_demagnetization_turns_ratio_threshold} \end{equation} - as a threshold for the turns ratio to enable certain switch-on times. Also, it should be noted that the turns ratio directly influences the maximum blocking voltage of the transistor: + as a \hl{threshold for the turns ratio} to enable certain switch-on times.\pause Also, it should be noted that the turns ratio directly influences the \hl{maximum blocking voltage of the transistor}: \begin{equation} \max\{u_\mathrm{T}(t)\} = U_1 + U_1 \frac{N_1}{N_3} = U_1 \left(1 + \frac{N_1}{N_3}\right). - \end{equation} + \end{equation}\pause Hence, to allow relatively high duty cycles by a high $N_1$ to $N_3$ ratio, cf. \eqref{eq:forward_converter_demagnetization_turns_ratio_threshold}, the blocking voltage of the transistor increases. \end{frame} @@ -1676,12 +1676,12 @@ \subsection{Forward converter} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \begin{frame} \frametitle{Section summary} - This section provided a first introduction to isolated DC-DC converters with the forward and flyback converters as examples. The key takeaways are: + This section provided a first introduction to isolated DC-DC converters with the forward and flyback converters as examples.\pause The key takeaways are: \begin{itemize} - \item The forward converter is a buck-derived topology while the flyback converter is a buck-boost-derived topology. - \item A transformer is used to provide galvanic isolation between input and output. + \item The forward converter is a buck-derived topology while the flyback converter is a buck-boost-derived topology.\pause + \item A transformer is used to provide galvanic isolation between input and output.\pause \item Limiting the magnetiziation of the transformer is a key aspect in the operation of these converters to prevent saturation (nonlinear behavior, extra losses). - \end{itemize} + \end{itemize}\pause In addition, there are many other isolated topologies that are used in practice, e.g., \begin{itemize} \item Push-pull converter,