EVLB001 Datasheet, PDF (14/35 Pages) ATMEL Corporation – Automatic microcontroller dimmable ballast

4.5.4
Power Control
Description
Ballast Demonstrator Operation
Calculate input power for both lamps = PB4 (lamp current) * (lamp voltage). Use this
data for DALI feedback verification if required. Set programmable gain of AMP0 to 10.
78 watts will be 0.195 VDC at the input of AMP0+ or 1.95V internal A/D input.
Adjust frequency up (lower power) or down (higher power) at 30KHz/sec rate. Limit fre-
quency to 100% (PB4 = 0.195V and 32KHz) to 80KHz dimming range. The dimming
must be logarithmic for the best resolution. The largest lumen change will be at the low-
est power setting. A small high frequency change 70 to 80kHz will give a large perceived
dimmed range.
If PB4 > 0.220V for two lamps or > 0.110V for one lamp, set half bridge drive off to avoid
an over current. Start re-ignition sequence. Repeat 6 times and if still out of the limit, set
TX DALI fail signal & shutdown PFC and half bridge drive.
ATAVRFBKIT / EVLB001 User Guide
4-12
7597B–AVR–10/07