ALQ07 Datasheet, PDF (22/28 Pages) Astec America, Inc – Technical Reference Notes

22
Input Reverse Voltage Protection
Under installation and cabling conditions where reverse polarity across the input
may occur, reverse polarity protection is recommended. Protection can easily be
provided as shown in Figure ‘Reverse Polarity Protection Circuit’. In both cases the
diode used is rated for 3A/100V. Placing the diode across the inputs rather than
in-line with the input offers an advantage in that the diode only conducts in a reverse
polarity condition, this increases circuit efficiency and thermal performance.
EMC
Reverse Polarity Protection Circuit
Input filters are included in the converters to help achieve standard system
emissions certifications. Some users however, may find that additional input filtering
is necessary. The ALQ07 series has an internal switching frequency of 360kHz so a
high frequency capacitor mounted close to the input terminals produces the best
results. To reduce reflected noise, a capacitor can be added across the input as
shown in Figure ‘Ripple Rejection Input Filter’, forming a 　 filter. A 47uF/100V
electrolytic capacitor is recommended for C_in.
Ripple Rejection Input Filter
For conditions where EMI is a concern, a different input filter can be used. The
following figure ‘EMI Reduction Filter’ shows a filter designed to reduce EMI effects.
ALQ07 series can meet EN55022 CLASS A with the following figure.
ALQ07 DC-DC Converter Technical Reference Notes
DATE: Aug., 9, 2003