Delta Electronics Series H48SA - Manual (Page 9)

DS_H48SA12025_05052008
9
Figure 21:
Circuit configuration for trim-down (decrease output
voltage)
If the external resistor is connected between the TRIM
and SENSE (-) the output voltage set point decreases
(Fig. 21). The external resistor value required to obtain a
percentage of output voltage change △% is defined as:
Rtrim_down
100
Δ
2
−
⎛⎜
⎝
⎞⎟
⎠
k
Ω
Ex. When trim down to 9.6V from 12V
Δ = 100*(12-9.6)/12 = 20
Rtrim_down =
) 2
20
100
(
−
kΩ
Rtrim_down = 3 kΩ
The typical resistor value can be seen in below figure22.
Output voltage
Resistor value (
Ω
k )
13.2V 95.8
12.6V 183.7
10.8V 8.0
9.6V 3.0
Figure 22:
Trim resistor value example for popular output
voltages
The output voltage can be increased by both the remote
sense and the trim, however the maximum increase is the
larger of either the remote sense or the trim, not the sum
of both.
When using remote sense and 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.
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
SENSE(+) or SENSE(-). The TRIM pin should be left
open if this feature is not used.
Figure 20:
Circuit configuration for trim-up (increase output
voltage)
If the external resistor is connected between the TRIM
and SENSE (+) pins, the output voltage set point
increases (Fig. 20). The external resistor value
required to obtain a percentage of output voltage
change △% is defined as:
Rtrim_up
12
1.225
2
−
⎛⎜
⎝
⎞⎟
⎠
100
Δ +
( )
⋅
100
+
Δ
⎡
⎢
⎢
⎣
⎤
⎥
⎥
⎦
k
Ω
Ex. When trim up to 13.2V from 12V
Δ = 100*(13.2-12)/12 = 10
Rtrim_up
12
1.225
2
−
⎛⎜
⎝
⎞⎟
⎠
100 10
+
( )
⋅
100
+
10
⎡
⎢
⎢
⎣
⎤
⎥
⎥
⎦
k
Ω
Rtrim_up = 95.755 kΩ
I