Delta Electronics Q48DC - Manual (Page 10)

DS_Q48DC12003_03112008 10
FEATURES DESCRIPTIONS (CON.)
Output Voltage Adjustment (TRIM)
To increase or decrease the output voltage set point,
the modules may be connected with an external
resistor between the TRIM pin and either the Vo(+) or
Vo(-). The TRIM pin should be left open if this feature
is not used.
R
trim-down
Vo(+)
Trim
Vo(-)
Rtn
Figure 17:
Circuit configuration for trim-down (decrease
output voltage)
If the external resistor is connected between the TRIM
and Vo(+) pins, the output voltage set point decreases
(Fig.17). The external resistor value required to obtain
a percentage of output voltage change △% is defined
as:
( )
Ω
⎥⎦
⎤
⎢⎣
⎡
−
Δ
= −
K down Rtrim 46 . 9
749
Ex. When Trim-down -25%(12.1V×0.75=9.08V)
( ) ( )
Ω = Ω
⎥⎦
⎤
⎢⎣
⎡
− = −
K K down Rtrim 5 . 20 46 . 9
25
749
Vo(+)
Trim
Vo(-)
Rtn
R
trim-up
Figure 18: Circuit configuration for trim-up (increase output
voltage)
If the external resistor is connected between the TRIM and
Rtn the output voltage set point increases (Fig.18). The
external resistor value required to obtain a percentage
output voltage change △% is defined as:
( )
Ω
Δ
= −
K up Rtrim
197
Ex. When Trim-up +5%(12 .1V×1.05=12.71V)
( )
Ω = = −
K up Rtrim 4 . 39
5
197
When using trim, the output voltage of the module is usually
increased, which increases the power output of the module
with the same output current.
Care should be taken to ensure that the maximum output
power of the module remains at or below the maximum rated
power.