GE Industrial Solutions FNW500R Series - Manual (Page 8)

Data Sheet
October 5, 2009
FNW500R Power Modules; DC-DC Converters
36 – 75 Vdc Input; 28Vdc Output; 500W Output
LINEAGE POWER 8
Feature Description (continued)
With an external resistor between the TRIM and
SENSE(-) pins (Radj-down), the output voltage set
point (Vo,adj) decreases (see Figure 11). The following
equation determines the required external-resistor
value to obtain a percentage output voltage change of
Δ%.
For output voltages: 28V
Ω ⎟
⎠
⎞
⎜
⎝
⎛
−
Δ
× =
− K R
down adj
1
%
100
97 . 5
Where,
100 %
,
, ×
−
= Δ
nom o
desired nom o
V
V V
V
desired
= Desired output voltage set point (V).
F
Figure 11. Circuit Configuration to Decrease Output
Voltage.
Trim Up – Increase Output Voltage
With an external resistor connected between the Vo(+)
and SENSE(+) pins
(
Radj-up
), the output voltage set
point ( Vo,
ad
j ) increases (see Figure 12).
The following equation determines the required
external-resistor value to obtain a percentage output
voltage change of
Δ%.
For output voltages: 28V
Ω
Δ ×
=
− K
nom Vo
R
up adj
100
% ,
Where,
100 %
,
, ×
−
= Δ
nom o
nom o desired
V
V V
V
desired
= Desired output voltage set point (V).
Figure 12. Circuit Configuration to Increase Output
Voltage.
The voltage between the Vo(+) and Vo(-) terminals
must not exceed the minimum output overvoltage shut-
down value indicated in the Feature Specifications
table. This limit includes any increase in voltage due to
remote- sense compensation and output voltage set-
point adjustment (trim). See Figure 13.
Although the output voltage can be increased by both
the remote sense and by the trim, the maximum
increase for the output voltage is not the sum of both.
The maximum increase is the larger of either the
remote sense or the trim.
The amount of power delivered by the module is
defined as the voltage at the output terminals multiplied
by the output current. When using remote sense and
trim, the output voltage of the module can be
increased, which the same output current would
increase the power output of the module. Care should
be taken to ensure that the maximum output power of
the module remains at or below the maximum rated
power.
Examples:
To trim down the output of a nominal 28V module to
16.8V
100
28
8 . 16 28
%
×
−
= Δ
V
V V
∆% = 40
Ω ⎟
⎠
⎞
⎜
⎝
⎛
− × =
− K R
down adj
1
40
100
97 . 5
R
adj-down
= 8.96 k Ω
To trim up the output of a nominal 28V module to 30.8V
100
28
28 8 . 30
%
×
−
= Δ
V
V V
Δ% = 10
Ω
×
= −
K up Radj
100
10 28
R
tadj-up
= 2.8 KΩ