AN2950 Datasheet, PDF (1/37 Pages) STMicroelectronics – This document describes

AN2950
Application note
EVLVIPER28L-10W: 5 V/10 W, 60 kHz isolated flyback
with extra power management
Introduction
This document describes a 5 V, 2 A application with 3.3 A peak current capability of 1.9 sec,
using VIPer28, a new offline high-voltage converter from STMicroelectronics.
In some applications, an SMPS sometimes undergoes load peaks that can be two or more
times as much as the power it is supposed to deliver, though only for a short time interval
compared to the thermal time constants of the power components. Typical examples of such
loads are printers and audio systems.
In such cases, it is more cost-effective to thermally design the system for the maximum
continuous power and not for the peak power demand, which is sustained only for a limited
time window.
Such a design is possible thanks to the EPT function of the VIPer28, which allows the
designer to fix the maximum time window during which the converter is able to manage the
peak power and still maintain output voltage regulation. If the overload lasts for longer than
this time window, the converter is automatically shut down and enters auto-restart mode
until the overload is removed, so as to prevent damage to the power components.
The device has many other features such as an 800 V avalanche rugged power section,
PWM operation at 60 kHz with frequency jittering for lower EMI, a limiting current with
adjustable setpoint, an on-board soft-start, a safe auto-restart after a fault condition, and a
low standby power (< 50 mW at 265 V_AC).
The available protections include adjustable and accurate overvoltage protection, thermal
shutdown with hysteresis and delayed overload protection.
Figure 1. Demonstration board
April 2010
Doc ID 15494 Rev 1
1/37
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