AN2852 datasheet(12/35 Pages) STMICROELECTRONICS

Part #	AN2852

Description	This document describes the characteristics and performance of a 90 W wide range input

PDF	35 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

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12 / 35 page

Operating waveforms

AN2852

12/35

2.3

Short-circuit protection

A short-circuit at the output activates the overload protection (OLP). Figure 10 shows the

pins involved in this function. When the short-circuit is applied, the COMP pin saturates

high. The IC detects this condition and starts charging the SS capacitor. When the SS

voltage reaches 5 V, the system shuts down. Diode D29 allows the SS voltage to be

clamped at about 5.4 V and the protection has an auto-restart behavior. If the short circuit is

not removed, the IC enters the HICCUP mode (Figure 11). When the IC is stopped by the

OLP, the high-voltage startup generator is invoked only when Vcc falls to 5 V (VCCrestart).

Thanks to this approach, the period between two restart trials is quite long which reduces

the stress on power components.

Figure 10.

Detailed short-circuit behavior

AM01825v1

Ch1: SS pin voltage (yellow)

Ch2: COMP pin voltage (blue)

Ch3: FGND pin voltage (purple)

Ch4: PFC_STOP pin voltage (green)

AN2852 Datasheet(PDF) 12 Page - STMicroelectronics