AN2459 datasheet(25/35 Pages) STMICROELECTRONICS

Part #	AN2459

Description	Digital Power Factor Correction for Tube Lamp Ballasts

PDF	35 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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25 / 35 page

AN2459 - Application note

Signals measurement, processing & control

25/35

In addition to the aforementioned hardware protections, another safety feature (Maximum

TON increase protection) is implemented in the software and outlined in Figure 18. During

normal operation, the PFC routine counts the number of times the pre-set MOSFET's on-

time maximum (TONMAX) is reached. If the maximum count( NMAX) is exceeded an error is

introduced and the application is stopped. This condition indicates that the boost converter

is unable to reach the required output voltage.

Figure 19.

Overcurrent reaction demonstration

Note:

Brown = sense resistor voltage, Green = digital signal for driving MOSFET's

gate.

Microcontroller stops

all PWM outputs

Overcurrent

introduced

Reaction time

< 500ns

AN2459 Datasheet(PDF) 25 Page - STMicroelectronics