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Doc/main.tex
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Doc/main.tex
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@ -83,7 +83,7 @@
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\begin{Figure}
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\centering
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\includegraphics[scale=0.38]{SCHEMATIC_FULL.png}
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\captionof{figure}{WIP}
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\captionof{figure}{Final version of the boost converter}
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\label{fig:schematic_full}
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\end{Figure}
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@ -103,7 +103,7 @@
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\subsection{Control}
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\label{control}
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The system is controlled by the STM32F407 on the HU development board. The board provides the required PWN signals to control the MOSFETs and the ADC to read the output voltage. The program provides a small interface in which the user can view and control the duty cycle and frequency of the switching and read the current output voltage. The program also implements a simple PI control loop to control the output voltage, however it is not yet fully functional and requires more tuning.
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The system is controlled by the STM32F407 on the HU development board. The board provides the required PWM signals to control the MOSFETs and the ADC to read the output voltage. The program provides a small interface in which the user can view and control the duty cycle and frequency of the switching and read the current output voltage. The program also implements a simple PI control loop to control the output voltage, however it is not yet fully functional and requires more tuning.
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\begin{Figure}
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\centering
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@ -136,12 +136,15 @@
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\item Start up
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\end{enumerate}
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In this section a test or measurement will be described for each of the above
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characteristics.
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characteristics.
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Each of the characteristics have been tested at two different output voltages
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and various load currents. The different voltages are $7V$ and $3.3V$. The
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chosen load currents are $10$, $20$, $30$, $40$ and $50 mA$. These values
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were chosen to characterize the circuit over a broad range of conditions.
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were chosen to characterize the circuit over a broad range of conditions.
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Lastly, the switching frequency (PWM frequency to the MOSFETs) of the STM
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was locked to $30kHz$. The switching frequency was found by testing the efficiency
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of the circuit.
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For all tests, the data was handled in a simular way. For test 2 through 4,
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an oscilloscope was set up on the output voltage. The probe was set to
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@ -158,7 +161,7 @@
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\begin{Figure}
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\centering
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\includegraphics[scale=0.34]{SCHEMATIC_EFFICIENCY.png}
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\captionof{figure}{WIP}
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\captionof{figure}{Circuit with multimeters}
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\label{fig:schematic_efficiency}
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\end{Figure}
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To measure the efficiency of the circuit, four measurements were taken.
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@ -235,7 +238,7 @@ def SD(all_data, ch):
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\begin{Figure}
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\centering
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\includegraphics[scale=0.5]{RIPPLE.png}
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\captionof{figure}{WIP}
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\captionof{figure}{Close up of a ripple}
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\label{fig:ripple}
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\end{Figure}
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A significant source of the noise was caused by a specific ripple, shown in
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@ -288,7 +291,7 @@ for data in all_data:
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dt = data[1][1] - data[1][0]
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x = np.fft.rfftfreq(len(data[ch+1]), dt)
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# find maximum, max() and np.argmax()
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# find the maximum, max() and np.argmax()
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# are not playing nice with
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# imaginary numbers
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maximum = 0
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@ -314,9 +317,9 @@ return output_freq
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defined as $63\%$ and $95\%$ respectively. Further more, 'rise time' was defined
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as $90\%$, a metric used often in control theory.
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One problem that occured during the measurements, is that the aforementioned
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A problem that occured during the measurements, is that the aforementioned
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ripples and noise would cause erroneous readings. As such, the signal was
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filtered using a low pass filter, reducing the high frequencies from the
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filtered using a low pass filter ($\tau = 0.2ms$), reducing the high frequencies from the
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signal.
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\begin{lstlisting}[language=python, caption={LPF snippet}]
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@ -342,7 +345,7 @@ for i in range(1, len(data[3])):
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\begin{Figure}
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\centering
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\includegraphics[scale=0.5]{EFFICIENCY_PERCENTAGE.jpg}
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\captionof{figure}{WIP}
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\captionof{figure}{Efficiency vs load}
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\label{fig:efficiency}
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\end{Figure}
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\noindent The results for the efficiency measurements, as described in section
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@ -355,7 +358,7 @@ for i in range(1, len(data[3])):
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\begin{Figure}
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\centering
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\includegraphics[scale=0.5]{SNR_LOADVSPKPK.jpg}
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\captionof{figure}{WIP}
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\captionof{figure}{Noise $V_{pp}$ vs load}
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\label{fig:noise_pkpk}
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\end{Figure}
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\noindent The results for the noise measurements, as described in section
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@ -368,7 +371,7 @@ for i in range(1, len(data[3])):
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\begin{Figure}
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\centering
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\includegraphics[scale=0.5]{SNR_LOADVSSD.jpg}
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\captionof{figure}{WIP}
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\captionof{figure}{Noise SD vs load}
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\label{fig:noise_sd}
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\end{Figure}
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\noindent The results for the noise measurements, as described in section
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@ -378,11 +381,11 @@ for i in range(1, len(data[3])):
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noise is continued in this graph.
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\subsection{Ripple}
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\subsection{Ripple} \label{section:ripple_result}
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\begin{Figure}
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\centering
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\includegraphics[scale=0.5]{RIPPLE_LOADVSPKPK.jpg}
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\captionof{figure}{WIP}
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\captionof{figure}{Ripple $V_{pp}$ vs load}
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\label{fig:ripple_pkpk}
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\end{Figure}
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\noindent The results for the ripple measurements, as described in section
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@ -393,7 +396,7 @@ for i in range(1, len(data[3])):
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\begin{Figure}
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\centering
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\includegraphics[scale=0.5]{RIPPLE_LOADVSFREQ.jpg}
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\captionof{figure}{WIP}
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\captionof{figure}{Frequency ripple vs load}
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\label{fig:ripple_freq}
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\end{Figure}
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\noindent The frequency of the ripple is roughly $38 MHz$ and independant of
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@ -403,24 +406,25 @@ for i in range(1, len(data[3])):
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f = \frac{1}{2 \pi \sqrt{LC}}
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\end{equation}
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Using the values from figure \ref{fig:schematic_full}, the resonating frequency
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of the circuit should be around $27KHz$. Thus, this cannot be the cause of
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of the circuit should be around $27kHz$. Thus, this cannot be the cause of
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the high frequency. As the frequency of the ripple is magnitudes higher
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than the LC-circuit's resonant frequency, what is seen is most likely the
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Self Resonating Frequency (SRF) of the inductor. Typically the SRF is
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$>10 MHz$, so that could be a probable source of the high frequencies.
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\subsection{Start Up}
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\begin{Figure}
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\centering
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\includegraphics[scale=0.5]{TRANSIENT_RISE_10_MA.jpg}
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\captionof{figure}{WIP}
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\captionof{figure}{Start up 10 mA}
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\label{fig:start_10}
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\end{Figure}
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\begin{Figure}
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\centering
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\includegraphics[scale=0.5]{TRANSIENT_RISE_50_MA.jpg}
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\captionof{figure}{WIP}
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\captionof{figure}{Start up 50 mA}
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\label{fig:start_50}
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\end{Figure}
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