Datasheet

DataSheet
60W, Single Output
VER:00 Page 24 of 31 Issued Date：2009/03/02
EMC considerations (Continued)
To meet conducted emissions EN55022 CLASS B neededthe following components：
PXF60-24Sxx
Component Value Voltage Reference
C1,C3 4.7uF 50V 1812 MLCC
C5,C6 1000pF 2KV 1808 MLCC
L1 450uH ----
PXF60-48Sxx
Component Value Voltage Reference
C1,C2,C3 2.2uF 100V 1812 MLCC
C5,C6 1000pF 2KV 1808MLCC
L1 830uH ----
This Common ChokeL1 has been defined as follow:
■
L: 450μH±35% / DCR: 25mΩ, max
Aheight: 9.8 mm, Max
■
L: 830μH±35% / DCR: 31mΩ, max
Aheight: 8.8 mm, Max
■ Test condition: 100KHz/ 100mV
■ Recommended through hole: Φ0.8mm
■ All dimensions in millimeters
Input Source Impedance
The converter should be connected to a lowimpedanceinput source.Ahighly inductive source impedance can
affect the stability of the converter.An inputexternal L-C filter is recommended to minimize input reflected ripple
current.The inductorhas a simulated source impedanceof 12μH and the capacitoris Nippon chemi-con KZE series
47μF/100V. The capacitor must belocated as close as possibleto the input terminals of the converter forthe lowest
impedance.
Output Over Current Protection
When excessive output currents occur in the system, circuit protection is required on all converters
. Normally,
overload current is maintained at approximately 150 percent of rated current for PXF60 single output series.
Hiccup-mode is a method of operation to protect the converter from being damaged during an over-
current fault
condition. It also enables the converter to restart when the faultis removed.
One of the problems resulting from over current is that excessive heat may be generated in power devices;
especially MOSFET and Schottky diodes and the temperature of the
se devices may exceed their specified limits. A
protectionmechanism has to be employed to prevent those power devicesfrom being damaged.
Output Over Voltage Protection
The output over-voltage protectionconsists of a Zener diode that monitors the output voltage on the feedbackloop.
If the voltage on the output terminals exceeds the over-voltage protection threshold, then the Zener diode will send a
signal to the control IC to limit the output voltage.