Datasheet

DataSheet
40W, Dual Output
VER:00 Page 16 of 22 Issued Date：2009/03/02
Input Source Impedance
The converter shouldbe connected to a low impedance input source. Highly inductive source impedance can
affectthe stability ofthe converter. Input external L-C filter is recommended to minimize inputreflectedripple current.
The inductor has a simulated source impedanceof 12μHand the capacitor is Nippon chemi-con KZE series
47μF/100V.The capacitor must located as close as possible to the input terminalsof the converter for lower
impedance.
Output Over Current Protection
When excessive output currents occur in the system, circuit protection is required on all converters
. Normally,
overload current is maintainedat approximately150 percent of rated currentfor PXF40-xxWDxx series.
Hiccup-mode is a method of operation in the converter whose purpose is to protect the converter
from being
damaged during anover-current fault condition. It also enables the converter to restart when thefault is removed.
One of the problems resulting f
rom over current is that excessive heat may be generated in power devices;
especially MOSFET and Schottky diodes and the temperature of those devices may exceed their specified limits. A
protection mechanism has to be used to prevent those power devices from being damaged.
Output Over Voltage Protection
The output over-voltage protection consists of an output Zenerdiode that monitors the voltage on the output
terminals. If the voltage onthe output terminals exceeds the over-voltage protection threshold, thenthe Zener diode
clamps the output voltage.
Thermal Consideration
The converter operates in a varietyof thermal environments. However, sufficient cooling should be provided tohelp
ensure reliableoperation of theunit. Heat is removed by conduction, convection, and radiation to thesurrounding
environment. Proper cooling can be verified by measuringthe point as shown inthe figure below. The temperature at
this location should not exceed 105°C.When operating, adequate cooling must beprovided tomaintainthe testpoint
temperature at or below 105°C .Although the maximum point temperature of the converteris 105°C, limiting this
temperature to a lowervalue will increase the reliability of the unit.