Other Parts Discussed in Thread: TPS92074
Answer to why LM3444 V buck minimum calculation utilizes sin(θ), page 20, equation 28:
Currently in non-LED load, buck PFC applications, a commonly accepted output voltage that maintains acceptable THD and PFC
levels is one that maintains a 50% conduction angle each line cycle. See the TI Application Report Power Factor
Correction Using the Buck Topology(SLUP264) In practical terms this equates to 90 VDC for a 90 VAC minimum
input. For LED driver solutions this rule can be followed if the goal is simply a power factor ≥0.9. If the goal is
also THD less than 20% then stricter requirements must be followed. In general, designs with an LED stack
voltage beyond 45 V have difficulty achieving < 20% THD. For these solutions, a buck-boost topology should be
used so that the circuit has the capability to draw current from the line below the LED stack voltage.
From TPS92074 datasheet page 13, second paragraph
