AN1320 APPLICATION NOTE

8/20

5.2 SOFTWARE CHOICES

We have already done some software choose choosing the microcontroller. When we chose a microcontroller

with only one PWM output we have already decided to devote a certain amount of microcontroller resources to

build the PWM software (see appendix for software details).

A logic sequence of actions could be:

1) to check that everything is ok - i.e. all the ICs are supplied in the right way;

2) check the presence of the load

3) do the preheat sequence

4) check lamp ignition

5) set the current in the load according to the user input

This is a basic set of functions typical of nearly any ballast application (see fig. 7)

Figure 7. Flow Chart

ST6 start up

L6574 OK?

open load?

set Fpre

t>Tpre?

set IGN freq.

profile

lamp on?

set working

freq.

(freq.&loop

ref.)

dimming?

fault cd.?

#fail<MAX?

L6574 and

L6561 disable

wait for reset

and/or power

off

N

Y

Y

N

Y

Y

N

N

Y

N

Y

Y

N

N