Delta Electronics Q48DC manual Features Descriptions CON, Output Voltage Adjustment Trim

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.

Vo(+)

Rtrim-down

Trim

Rtn

Vo(-)

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:

⎡ 749		− 9.46	⎤	(KΩ )
Rtrim − down = ⎢	Δ		⎥
⎣			⎦

Ex. When Trim-down -25%(12.1V×0.75=9.08V)

⎡ 749			⎤	(KΩ ) = 20 .5(KΩ )
Rtrim − down = ⎢		− 9.46	⎥
	25
⎣			⎦

Vo(+)

Trim

Rtrim-up

Rtn

Vo(-)

Figure 18: Circuit configuration for trim-up (increase output voltage)

DS_Q48DC12003_03112008

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:

Rtrim − up = 197Δ (KΩ)

Ex. When Trim-up +5%(12 .1V×1.05=12.71V)

Rtrim − up = 1975 = 39.4(KΩ)

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.

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