1. Buck converter LM2596
Find the datasheet for the LM2596 switch and controller IC. Scroll through the following versions from two major manufacturers and notice that both have rather nice (and practical) theory of operation and design procedure sections. It is as if they want you to easily design the part into one of your systems (and therefore buy more of them).
1.1. hw05 tasks
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Inspect your buck converter module and draw the schematic of the device. Include values for as many parts as you can.
Add a resistor across the output terminals of your module and power your module from the AD2. Adjust the output voltage to the maximum value possible until just before one of the following conditions happen, whichever happens first:
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The AD2’s power supply outputs disconnect to protect against over current conditions.
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The load resistor becomes hot enough to smoke
How much power is your load absorbing under this condition?
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Use an oscilloscope (your Analog Discovery 2) to capture the waveform at node X. Display about 3 periods horizontally and set your vertical voltage scale so the waveform covers more than half the height of the scope window.
Turn in a PDF-format document containing:
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Schematic drawing
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Waveform capture at node X
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Documentation of the converter’s operating conditions. (input voltage, output voltage, load resistance, etc.)
If you are graphically-inclined, place a photo of the module next to the schematic and draw arrows matching up the various parts.
2. Boost converter MT3608
Find the datasheet for the MT3608 switch and controller IC.
2.1. hw06 tasks
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Inspect your buck converter module and draw the schematic of the device. Include values for as many parts as you can.
Add a resistor across the output terminals of your module and power your module from the AD2. Adjust the output voltage to the maximum value possible until just before one of the following conditions happen, whichever happens first:
-
The AD2’s power supply outputs disconnect to protect against over current conditions.
-
The load resistor becomes hot enough to smoke
How much power is your load absorbing under this condition?
-
Use an oscilloscope (your Analog Discovery 2) to capture the waveform at node X. Display about 3 periods horizontally and set your vertical voltage scale so the waveform covers more than half the height of the scope window.
Turn in a PDF-format document containing:
-
Schematic drawing
-
Waveform capture at node X
-
Documentation of the converter’s operating conditions. (input voltage, output voltage, load resistance, etc.)
If you are graphically-inclined, place a photo of the module next to the schematic and draw arrows matching up the various parts.
3. Future homework tasks
3.1. Output limits
The maximum current through the MT3608’s internal switch is limited to 4{A}, according to the datasheet. Because this is a boost converter, this current is also the maximum inductor current allowed by the chip and limits the maximum current supplied by the input source.
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Given an input voltage of 5{V}, find the maximum output voltage and current combinations that are possible under this switch current limitation.
Report this finding as both an inequality that is true when the combination is possible and as a two-dimensional plot. Use output voltage for the x-axis, load current for the y-axis, and shade the region that represents feasible combinations for this part.
The converter will reach the limit as the inductor becomes large and you ignore the forward voltage (set to zero) of the diode. In other words as \(\frac{\Delta i_L}{I_L} \rightarrow 0\)