Note that there is a mistake in the schematic diagram of the non-inverting buck-boost converter: Q4 is reversed.
The drain of Q4 must be attached to the output capacitor and the source of Q4 attached to the junction of the inductor and drain of Q3. Otherwise, when Q3 turns on the output capacitor will discharge through the body diode of Q4.
Side note: in this configuration the converter is symmetrical about the inductor and can transfer power in either direction. This is useful with a battery where the battery can be charged with a voltage source higher or lower than the battery voltage and then the converter can transfer power from the battery back to the source.
1 comment:
Indeed, there was a mistake in the diagram. Drain (not Source) of Q4 should be connected to the output. A corrected version of the problem has been posted on the HW4 page.
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