7
TDK-Lambda
PFE700SA Series
INSTRUCTION MANUAL
●Selection Method of External Bulk Capacitor for Boost Voltage
Boost voltage bulk capacitor is determined by boost voltage ripple voltage, ripple current and hold-up time.
Select capacitor value such that boost voltage ripple voltage does not exceed 15Vp-p.
Note)
When ambient temperature is -20
℃
or less, ripple voltage of boost voltage might increase due to
ESR characteristics. Therefore, verify above characteristics by actual evaluation.
For output hold-up time, refer to separate document “PFE700SA Evaluation Data" and use appropriate
capacitor up to 1200uF maximum. It is recommended that verification should be done through actual
evaluation.
For allowable ripple current value, refer to Fig.5-2 and select a capacitor with higher ripple current rating.
0
500
1000
1500
2000
2500
0
100
200
300
400
500
600
700
R
ip
pl
e
C
ur
re
nt
(
m
A
r
m
s)
Output Power (W)
100VAC
200VAC
Fig. 5-2
Allowable ripple current value
The recommended boost voltage bulk capacitance value range is 390uF-1200uF.
When using with reduced the bulk capacitance value, it is necessary to reduce output power as shown in
Fig. 5-3.
Fig. 5-3 shows recommended value at 25
℃
Base-plate Temperature (Tbp). Temperature variance might
have some effect on the characteristics. Therefore, verify characteristics by performing actual evaluation.
Refer to “Fig. 7-1 Base-plate Measuring Point”.
Note that reducing the bulk capacitance affects output hold-up time, dynamic line response and dynamic
load response characteristics. It is recommended that verification should be done through actual
evaluation.
0
100
200
300
400
500
600
700
300
600
900
1200
O
ut
pu
t P
ow
er
(
W
)
Bulk Cap. (uF)
390
Tbp:25
℃
Fig. 5-3 Output Power v.s. Boost Voltage Bulk Capacitance