BR1000G vs. SL300
This is the strangest, least-square waveform I can remember seeing from a stepped approximation direct AC inverter feeding my SL300 PSU and LED string. It has soft rising and falling edges with sloped flats. Where power analysis is concerned, I get 117 VRMS with a voltage THD+N of 26% under an 84.9 W load, which actually sounds good. The large current spike at the tip of the slope though? Not so good.
Why does it look so weird? My guess is high stray inductance limiting the current and voltage change rates. The stray inductance interacting with X-class capacitors across the transformer’s outputs would also explain the slight ringing at the FETs’ turn-off.
BR1000G vs. EA-650
With reasonably square voltage waveforms, both my APFC and non-APFC supplies produce similarly square current waveforms. Upon seeing the oddly shaped voltage waveform and unexpected current waveform from my SL300, I had to find out how an APFC power supply would respond, so I threw my PC at it.
Curious gets even more so as the UPS’ output becomes a half-sinusoid closely following the 60 Hz fundamental for the first half of each alternance. The Delta-made EA-650’s APFC circuitry handles the odd waveform like a champ, producing a current waveform that still follows the voltage’s waveform as expected if you ignore the APFC noise.
With my PC pulling 108.6 W and 119.4 VA from the UPS, the UPS put out 118 VRMS with a voltage THD of only 22%.
In person, the buttons look much dimmer with the cover on than they do on the left. Without the cover, they are uncomfortable to look at.
I went into this tear-down to see how much APC's build quality may have changed over the past 10 years. While the old BX1000 was a Chemi-Con wonderland, this newer model is a Chinese capacitor convention. I was particularly disappointed by the Chemi-Con capacitor on the power supply’s input paired with Jamicon and Chang capacitors on the TOP285’s outputs, as they are critical components in flyback power supplies.
While the output voltage waveforms may be odd square-sinusoid hybrids, neither of my test power supplies had any issues with them, so I’ll shrug them off as acceptable. Otherwise, build quality is par for APC, and kudos is earned for coming up with a cable-free battery hook-up solution.