Delta Electronics DEP-008 A, Дополнительное руководство, Страница: 13 / 20

For Ratio-Metric applications that need the PS1 and PS2 outputs arrive regulation set point at
same time, use equation 1 to calculate R1, set
△
V=Vo
set,PS1
–Vo
set,PS2
and
△
V will be
negative. The waveforms of power up and down are showed in Figures 7 and 8.
K
Vref
Vref V Vo
R
PS set
20 *
] ) [(
1
2 ,
− ∆ +
= Ω
------------------------------------------------------(1)
Note:
1. Vref =0.4×Vo
set,PS2
, please refer to Table 5 for Vref set value.
2.
△
V is the maximum difference of voltage between PS1 and PS2 supply voltage.
For example, the PS1 Vo
set,PS1
=5V, the PS2 Vo
set,PS2
=3.3V, R1 is calculated as follows:
K K R 75 . 55 20 *
32 . 1
] 32 . 1 ) 7 . 1 3 . 3 [(
1
=
− +
= Ω
Figure 7. Ratio–metric tracking Power up Figure 8. Ratio–metric tracking Power down
For Ratio-Metric applications that need the PS2 supply voltage rises first at power up and falls
second at power down, use equation 2 to calculate R1, set
△
V
≦
0.4×Vo
set,PS2
and
△
V will be
negative. The waveforms of power up and down are showed in Figures 9 and 10.
K
Vref
Vref V Vo
R
ps set
20 *
] ) [(
1
2 ,
− ∆ −
=
-----------------------------------------------------------------(2)
Note:
1. Vref =0.4×Vo
set,PS2
, please refer to Table 5 for Vref set value.
2.
△
V is defined as the voltage difference between Vo
PS1
and Vo
PS2
when Vo
PS2
reaches
its rated voltage.
13
PS1=5V
PS2=3.3V
PS1
PS2
+
△
V=1.7V