I'm still not understanding. The two phases reverse polarity even now. Half the time the voltage input (top pin) goes up to +169V and the other half of the time it goes down to -169V relative to GNDA. That's when diode D1 prevents reverse breakdown in the LED.
I'm afraid I still don't understand how a delta connection would be any different from the point of view of voltage magnitude and polarity reversal. Looks like I'll have to go off and do some more reading....
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The Quick Shield: breakout all 28 pins to quick-connect terminals