AN3372 datasheet(25/37 Pages) STMICROELECTRONICS

Part #	AN3372

Description	This note describes digital ballast for 70 W HID lamps

PDF	37 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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25 / 37 page

AN3372

ST7 microcontroller application pin use

Doc ID 018625 Rev 1

25/37

Figure 18.

PFC ZCD circuitry

The boost converter of the PFC works in transition mode. To obtain this feature an auxiliary

winding is wound in the main inductor of the half bridge and when the current reaches the

zero value the variation of voltage used by the LTIC pin of the microcontroller starts the

conduction of the switch.

●

Pin 27: general purpose input-output pin. This pin is used to switch on a red LED

indicating fault condition.

●

Pin 28: PFC OC, this pin is used to perform overcurrent on the PFC section avoiding

saturation of the inductor. In Figure 18 it is possible to see that an RC filter composed

of R3 and C5 is inserted to avoid unexpected switch-off due to the noise in the circuit.

This protection is not implemented.

AN3372 Datasheet(PDF) 25 Page - STMicroelectronics