FA5502PM Fuji Electric holdings CO.,Ltd, FA5502PM Datasheet - Page 19

• Manufacturer Part Number: FA5502PM
• Description: Power Factor Correction
• Manufacturer: Fuji Electric holdings CO.,Ltd

(3) Designing a boost converter
(3-1) Output voltage
(3-2) Inductor
(3-3) Current detecting resistance Rs
FA5502P/M
Vin
as an PFC converter. The following describes how to
determine each values of the circuit.
10V higher than the peak value of maximum input
voltage to ensure a stable operation. When it is used
as PFC converter, the input voltage has a sinusoidal
waveform. Therefore, set the output voltage Vo by:
current mode, select an approximate inductance
considering the ratio of inductor ripple current to the
peak input current by:
current to control the line current into sinusoidal.
Because the threshold voltage for overcurrent limiting
circuit is -1.1V (typ.), peak inductor current limit Ip is
calculated by:
Fig.19 shows a basic circuit of boost converter used
Set the output voltage of boost converter at least
When PFC converter operates in the continuous
Where,
Rs is a resistor which allows to detect an inductor
Fig.20 Outline of inductor and AC line current
Vin: AC input voltage [Vrms]
fs: Switching frequency [Hz]
Pin: Maximum input power [W]
L
Ip
Vo
Vin
: Ratio of ripple content to peak input current.
(Set to approx. 0.2, see Fig.20)
(max)
Vin
R
1
Fig.19 Boost converter circuit
1 .
S
2
2
Inductor current
:
[
Vo
fs
Maximu
] A
Iac(peak)
Vin
Pin
• • • • • (14)
Rs
(max)
L
2
Vo
AC
Vin
10
input
[
• • • • • (13)
] V
Q
t
voltage
Ir
D
Ir
line current
/
Iac
[
Vrms
(
peak
Co
]
)
• • (12)
Vo
(3-4) Smoothing capacitor
19
So that the voltage inputted to IDET pin will not be
beyond -1V, whereby the overcurrent limiting circuit
will not operate at a normal operation, calculate Rs by:
switching ripple current contained in the inductor
current, circuit efficiency, etc. Definitely determine it by
evaluation on a actual circuit.
twice the line frequency as shown in Fig.21.
approximated by:
Therefore, output ripple voltage Vrp (p-p) is:
The overvoltage limiting circuit of FA5502 monitors the
instantaneous output voltage. Therefore, determine
the capacitance of smoothing capacitor Co so that the
instantaneous output voltage including the ripple at a
normal operation will not reach the overvoltage limit.
Instantaneous value Vo(t) of output voltage is
Where,
As a matter of fact, the peak current changes with
PFC converter output contains ripple voltage of
Where,
Using formula (17), determine the necessary value.
Vin (min): Minimum AC input voltage [Vrms]
Pin (max): Maximum input position [W]
Io: Output current [A]
ω
Co: Output smoothing capacitance [F]
R
Vo
Vrp
Vo
0
S
) t (
= 2 f
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V
2
Vo
0
Fig.21 Output ripple voltage
0
Vin
rp
Io
(f
Co
Pin
0
(min)
: AC line frequency [Hz])
2
(max)
0
• • • • • (17)
Io
Co
[
]
sin(
2xfac
• • • • • (15)
2
0
) t
• • • • • (16)