petrus bitbyter said:
Nice chip indeed, though it still requires a lot of external components
compared to the current discrate designs.
The transformer is almost always needed, and something to switch the current
(typ 2 for the tube, one for the PFC), so that leaves a bunch of cheap
passives (at a cost as low as 0.1 cent each + mounting) and a controller IC
(which is necessary if doing anything other then abusively making the tube
light up). This design is cheap in production, and very cheap considering
the potential performance. It is not designed as a low cost CFL driver
solution - note the wattage rating.
If I made ballasts for larger florescent tubes (eg 4 foot T12's, T8's etc),
I would have this design into consideration.
Something to consider - Industrial and commercial power is paid by the kWh
used, and by the demand, usually in kVA. The kVA demand meter is reset on a
monthly basis (it typically takes 15 minutes to register 90% of a kVA for a
1 kVA load), and each kVA is charged around $5 to $8 (sometimes more) per
kVA drawn, per month.
Now say you have 10 kW worth of lighting (a mere 60 to 70 x 4 foot 4 tube
ceiling lights). Perfect PF gives a kVA load of 10 kVA (neglecting a small
loss from electronic ballasts), which with active PFC is almost achievable.
Now say you have an older/cheaper ballast type that draws 12 kVA per 10 kW
of light output. that's 2 extra kVA's per month, totaling $120 to $192 per
year, not including the likely lower efficiency losses resulting in higher
kWh used. Assuming a cheap ballast is $1 or $2 cheaper (which is realistic),
I'd make my initial investment back in buying the better ballasts in the
first place in under a year. A pretty good return in my books. Another
factor is tube life - a well controlled ballast keeps the tube going much
longer then a cheap ballast, as it abuses the tube less. Add the cost of
labor to change a bunch of overhead tubes with lots of stuff on the floor,
and it can be demonstrated that the tube cost is not that significant
anymore. Don't forget the disposal fees from the hazardous material.
Cheaping out rarely wins.