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Decrement ballast frequency by ramp step
frequency
Is preheat frequency reached?
Has 1ms gone?
no
yes
Calculate PI PFC stage regulator
for reference sine gain
phase 3 - Go to preheat
frequency
3
Has preheat time gone?
no
phase 4 - Keep for
preheat time
yes
Calculate PI PFC stage regulator
for reference sine gain
Test DC-BUS voltage on limits
Test DC-BUS voltage on limits
no
Decrement ballast frequency by ramp step
frequency
Has 1ms gone?
yes
Calculate PI PFC stage regulator
for reference sine gain
Set ballast frequency
faultISR()
Is min. ignition frequency reached?
yes
no
Are lamps ignited?
Are lamps ignited?
yes
Are currents through lamps >
minimum tube current ?
Is attemp to ignite > 0 ?
no
Set maximum ballast frequency
yes
Measure lamp currents
Reset auxiliary variable aux
yes
no
Test DC-BUS voltage on limits
no
yes
phase 5 - Go to ignition
frequency
yes4
no
1no
Detailed Software Description
Dimmable Light Ballast with Power Factor Correction, Rev. 1
Freescale Semiconductor 49
Figure 5-9. Flow Chart — Main Flow, Part 3