SEPIC.tex

Rational Point — Fri, 24 Apr 2026 14:13:47 GMT

Source code for File:SEPIC.pdf

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	$$		$$

	Increasing the duty cycle $\tau/T$ will increase the potential $V_{P_\textrm{off}}$ which is available at the output less the forward drop through the diode $D_1$, but it will correspondingly decrease the clock-cycle-averaged current available at the increased potential. A Pulse Width Modulator with a feedback loop will assist in maintaining a stable output potential from a variable input potential from solar panels.		Increasing the duty cycle $D=\tau/T$ will increase the potential $V_{P_\textrm{off}}$ which is available at the output less the forward drop through the diode $D_1$, but it will correspondingly decrease the clock-cycle-averaged current available at the increased potential. A Pulse Width Modulator with a feedback loop will assist in maintaining a stable output potential from a variable input potential from solar panels.

	\section{Energy transfer per clock cycle}		\section{Energy transfer per clock cycle}
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	Zhang \cite{zhang} suggests choosing inductors of a value that will allow a 40\% ripple in current at the switching frequency. In effect, that causes perhaps 64\% of the total energy stored in an inductor to be transferred each clock cycle, which appears to be a good practical limit of tolerable ``ripple'' under conditions of light load or open circuit among other considerations.		Zhang \cite{zhang} suggests choosing inductors of a value that will allow a 40\% ripple in current at the switching frequency. In effect, that causes perhaps 64\% of the total energy stored in an inductor to be transferred each clock cycle, which appears to be a good practical limit of tolerable ``ripple'' under conditions of light load or open circuit among other considerations.

	We suggest using heavy gauge wire on a heavy iron core to carry large currents to avoid overheating and/or saturating the core. This only permits relatively few turns of wire and will not result in any excessively large inductance.		We suggest using heavy gauge wire on a heavy iron core to carry large currents to avoid overheating and/or saturating the core. This only permits relatively few turns of wire and will not result in any excessively large inductance. However this approach limits the system to low frequencies.

	The capacitors in a coupled SEPIC system are movable~~, and~~ their exact values do not seem to be critical.		The capacitors in a coupled SEPIC system are movable: their exact values and placements do not seem to be critical, and may need to be determined experimentally.

	\section{Size and scale of systems proposed}		\section{Size and scale of systems proposed}
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	The selection of components is based on how much ``ripple voltage'' and possible overheating of components we are willing to tolerate versus how much money we can afford and are willing to spend on bigger and better components for reliability and smoothness of the power supply system.		The selection of components is based on how much ``ripple voltage'' and possible overheating of components we are willing to tolerate versus how much money we can afford and are willing to spend on bigger and better components for reliability and smoothness of the power supply system.

			It is particularly important to pay attention to officially published datasheets on electronic component parts and ICs. Those are the legal contracts of technical specifications on which the chips are sold, and they contain all the information you need to know from the manufacturer on the particular product you are using. Other comments or opinions from engineers or salesmen, personal or otherwise, are ultimately irrelevant, as they have presumably already stated all of the information to which they can be held accountable on the datasheet.

			Once you ``make'' or ``build,'' you are no longer a consumer but a potential competitor and arch-rival making a possibly hostile use of the firm's component parts which you are effectively taking over and re-purposing as parts of your own final product. So if you are in direct competition with that firm, you would be well advised to avoid any ``vendor lock-in'' and be prepared to find alternatives or substitutes for their component parts.

			\begin{quote}
			``We sell electronic component parts and chips, and we have engineers who would love to talk to you about the technical details, but (obviously) our goals and objectives are merely to protect and defend our intellectual property and if at all possible to prevent you from making or building anything in direct competition with any of our own products.''
			\end{quote}

			\noindent To view the published datasheet with such a jaundiced eye and jaded opinions, the Amish farmer's honesty won't permit it at all.

	\subsection{Power MOSFETs or IGBTs}		\subsection{Power MOSFETs or IGBTs}
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	The ``Arduino'' also has a rudimentary pulse width modulation ``analog output'' running at about 0.5~kHz \cite{arduino-pwm}, which is adequate for our purposes as long as we design and plan for the very low frequency.		The ``Arduino'' also has a rudimentary pulse width modulation ``analog output'' running at about 0.5~kHz \cite{arduino-pwm}, which is adequate for our purposes as long as we design and plan for the very low frequency.
	~~\subsection{Logic level power supply}~~

	\begin{figure}		\begin{figure}
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	\draw (2,6) node[circ]{} to[resistor, label=$R_2$] ++(0,-3) node[circ, name=qb0]{}		\draw (2,6) node[circ]{} to[resistor, label=$R_2$] ++(0,-3) node[circ, name=qb0]{}
	to[zzDo, invert, label=$D_2$] ++(0,-3) node[circ]{};		to[zzDo, invert, label=$D_2$] ++(0,-3) node[circ]{};
	\draw (4,3) node[~~pnp~~, name=q1]{$Q_2$};		\draw (4,3) node[npn, name=q1]{$Q_2$};
	\draw (qb0) -- (q1.base);		\draw (qb0) -- (q1.base);
	\draw (2,6) -- ++(2,0) -- (q1.~~emitter~~);		\draw (2,6) -- ++(2,0) -- (q1.collector);
	\draw (2,0) -- ++(3,0) node[circ, name=j3]{} -- ++(2,0) node[circ, name=j4]{} -- ++(1,0) node[ocirc, label=$GND$]{};		\draw (2,0) -- ++(3,0) node[circ, name=j3]{} -- ++(2,0) node[circ, name=j4]{} -- ++(1,0) node[ocirc, label=$GND$]{};
	\draw (q1.~~collector~~) -- ++(1,0) node[circ, name=j1]{} to[cute inductor, inductors/coils=3, label=$L_4$]		\draw (q1.emitter) -- ++(1,0) node[circ, name=j1]{} to[cute inductor, inductors/coils=3, label=$L_4$]
	++(2,0) node[circ, name=j2]{} -- ++(1,0) node[ocirc, label=$V_{CC}$]{};		++(2,0) node[circ, name=j2]{} -- ++(1,0) node[ocirc, label=$V_{CC}$]{};
	\node[~~below~~ right, font=\scriptsize] at (q1.emitter){$E$};		\node[above right, font=\scriptsize] at (q1.emitter){$E$};
	\node[~~below~~, font=\scriptsize] at (q1.base){$B$};		\node[above, font=\scriptsize] at (q1.base){$B$};
	\node[~~above~~ right, font=\scriptsize] at (q1.collector){$C$};		\node[below right, font=\scriptsize] at (q1.collector){$C$};
	\draw (j1) to[curved capacitor, label=$C_5$] (j3);		\draw (j1) to[curved capacitor, label=$C_5$] (j3);
	\draw (j2) to[curved capacitor, label=$C_6$] (j4);		\draw (j2) to[curved capacitor, label=$C_6$] (j4);
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	\end{figure}		\end{figure}

			\subsection{Logic level power supply}
	A simple Zener diode voltage regulator with a transistor current buffer \cite{zd-tr} as depicted in Figure~\ref{f2} should be used to power logic level circuits directly from highly variable power supplies if possible. This simple circuit also has the effect of an undervoltage lockout or UVLO \cite{uvlo-se}. Some hysteresis \cite{uvlo-h} would be desirable in order to avoid an amplified chattering effect from transistor $Q_2$ when the voltage supply is barely adequate and teetering at the edge of the lockout level.		A simple Zener diode voltage regulator with a transistor current buffer \cite{zd-tr} as depicted in Figure~\ref{f2} should be used to power logic level circuits directly from highly variable power supplies if possible. This simple circuit also has the effect of an undervoltage lockout or UVLO \cite{uvlo-se}. Some hysteresis \cite{uvlo-h} would be desirable in order to avoid an amplified chattering effect from transistor $Q_2$ when the voltage supply is barely adequate and teetering at the edge of the lockout level.

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