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ST7LITE0xxx MICROCONTROLLED BALLAST

1.1 POWER SECTION

This application note focuses on the lamp control and therefore a DC voltage 400V has been

chosen to supply the application. To have a complete ballast connectable to the standard

mains, the EVAL6562-80 board can be chosen to serve as a PFC part, between AC-mains

and the 400V DC link.

In this application, voltage-fed series resonant half-bridge inverters are used to drive a fluores-

cent tube lamp in zero-voltage switching mode and the microcontroller handles the control of

the ballast. The microcontroller drives the L6384 high voltage half bridge driver. L6384 is a

small eight-pin device, with one input, selectable dead time and implemented bootstrap diode

(refer to the L6384 datasheet for more information). In Figure 2, the driver and resonant tank

topology are shown. Thanks to the microcontroller flexibility, existing resonant circuits can

also be used.

Figure 2. Power Section Circuit

400V

LAMP

LAMP

C4

100nF

63V

C4

100nF

63V

C7

10nF

1600V

C7

10nF

1600V

R10 22

R10 22

R9

22

R9

22

Q1

Q1

Q2

Q2

IN

1

Vcc

2

DT/SD

3

GND

4

Vboot

8

HVG

7

Vout

6

LVG

5

U2

L6384

U2

L6384

1

2

L1

2.3

EF25

L1

2. mH

EF25

R36

1

1W

R36

1

1W

C5

100nF

250V

C5

100nF

250V

STP5NK60ZFP

STP5NK60ZFP

2