March 2006 REVISION 09

SH 21 of 31

Technical Reference Note

AIF - PFC Power Factor

Correction Series

Connections to enable Astec DC-DC converters.

The output from the PFC’s LD ENABLE (pin 13) can directly drive an opto-coupler to provide an isolated signal to enable

the power output of one or more Astec DC-DC converter modules.

-O/P

9

8

1

16

+O/P

to ENABLE pin of DC-DC

converter module

to -SENSE PIN / S COM pin

of DC - DC converter module

Load Enable Connection for Astec DC-DC Converters

AIF04ZPFC

General Connections to enable a load

For enabling loads other than Astec DC-DC converters the following circuit can be used. The LD ENABLE pin can directly

drive a MOSFET with a 15V zener clamping the gate voltage.

-O/P

9

8

1

16

+O/P

RESISTIVE

LOAD

IRFP450

AIF04ZPFC

D

S

G

Conducted EMI

The PFC modules will require additional EMI filtering to enable the system to meet relevant EMI standards.

PFC modules have an effective input to ground (baseplate) capacitance of 1600pF. This should be accounted for when

calculating the maximum EMI ‘Y’ capacitance to meet ground leakage current specifications. An example filter circuit is

shown below.