Fig.2.5
Ripple current
values
C30
※
Ripple current value is total of 2 paralleled capacitors.
2.8 Inrush current limiting resistor: TFR1
■
The TUNS300/500/700 must connect TFR1.
■
If TFR1 is not connected, the power supply will not operate.
■
Connect TFR1 between R and +BC.
Recommended resistance of TFR1 is shown in Table 2.5.
■
The surge capacity is required for TFR1.
■
Wirewound resistor with thermal cut-offs type is required.
■
Therefore, we don’t recommend connecting a large resistance as TFR1.
■
The inrush current changes by PCB pattern, parts characteristic etc.
Check the actual inrush current value flowing through the AC line.
Table 2.5
Recommended
resistor
TFR1
■
The selection method of TFR1 is shown below.
・
Calculation of resistance
Resistance can be calculated using the following formula.
TFR1
:
Inrush current limiting resistor
RL
:
Line impedance
Vin
:
Input voltage (rms)
Ip
:
Primary Inrush current (peak)
・
Calculation of required surge capacity
Required surge capacity can be calculated using the following formula.
Please contact to the component manufacturer regarding the surge current withstanding capability.
I2t
:
Current squared times
TFR1
:
Inrush current limiting resistor
Cbc
:
Smoothing capacitor for boost voltage
Vin
:
Input voltage (rms)
A-6
TUNS300F
4.7
Ω
~ 22
Ω
TUNS500F
4.7
Ω
~ 22
Ω
TUNS700F
4.7
Ω
~ 22
Ω
Model
Recommended resistance
Inrush current limiting resistor can be used to limit the primary inrush current. However, the
secondary inrush current can’t be limited by increasing the resistor value of inrush current
limiting resistor. The secondary inrush current is approx. 25 ~ 30A.
]
[
1
2
2
2
s
A
TFR
Vin
Cbc
t
I
×
=
]
[
2
1
Ω
−
×
=
L
R
Ip
Vin
TFR
0
500
1000
1500
2000
2500
3000
3500
0
20
40
60
80
100
120
Ri
pp
le
cu
rre
nt
[m
Ar
ms
]
Output current [%]
TUNS300F(100VAC)
TUNS300F(200VAC)
TUNS500F(100VAC)
TUNS500F(200VAC)
TUNS700F(100VAC)
TUNS700F(200VAC)
Applications Manual
TUNS300/500/700
