Application Note AN-1150 - International Rectifier

3.2 Power Circuit Design
AC Line
Bridge
- +
AC Neutral
L BST
D BST
V OUT
C IN
R VFB1
R BOP1
IR1152
IR1145
R R G
VFB2
R BOP2
1
C
COM GATE 8
OUT
2
M COMP VCC 7
V BST
CC
3
ISNS
VFB 6
4
BOP
OVP/EN 5
R BOP3
R gm C VCC
R C C VFB3
BOP P
R OVP1
R OVP2
R OVP3
R SF
C SF
C Z
COM
R SNS
GND
Fig.3: IR1152 based PFC Boost Converter
Peak Input Current
It is necessary to determine the maximum input currents (RMS & peak) from the
specifications in Table 1 before proceeding with detailed design of the PFC boost
converter. The maximum input current is typically encountered at highest load &
lowest input line situation (350W, 85VAC). Assuming a nominal efficiency of 92%
at this situation, the maximum input power can be calculated:
PO
( MAX ) 350W
PIN ( MAX )
= = = 380W
η 0.92
From this, the maximum RMS AC line current is then calculated:
I
I
IN ( RMS ) MAX
IN ( RMS ) MAX
MIN
= η
MIN
( V
P
O ( MAX )
IN ( RMS ) MIN
) PF
350W
=
= 4.5A
0.92(85V
)0.998
The selection of the semiconductor components (bridge rectifier, boost switch &
boost diode) is based on I IN(RMS)MAX =4.5A.
Assuming a pure sinusoidal input, the maximum peak AC line current can then
be calculated:
I
I
IN ( PK ) MAX
IN ( PK ) MAX
=
2( P
V
IN ( MAX )
IN ( RMS ) MIN
1.414(380W
)
=
= 6.3A
85V
)
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