CS1500_1 Datasheet, PDF (12/22 Pages) Cirrus Logic – Digital Power Factor Correction IC

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CONFIDENTIAL
CS1500
4. APPLICATION EXAMPLE
The following sections describe an example application. The
example is based upon the typical connection diagram
illustrated in Figure 21.
Equations are provided to demonstrate how a user would
calculate the values for the components shown in the diagram.
AC
Mains
BR 1
R AC
R 1a
R1 b
C1
VD D
C2
D1
LB
1
NC
8
NC
3
IA C
4
FB
7
VD D
2
ST B Y
5
GND
C S 1500
6 R3
GD
D2
RFB
R 2a
R 2b
Regulated
C3 _{DC Output}
Q1
Figure 21. CS1500 Basic Application Circuit
4.1 PFC for Power Supply Application
The following design example is for a universal main input,
front-end PFC converter with the following parameters:
V_in(min)
V_in(max)
V_link
P_o
90 VAC
265 VAC
400 V
90 W
4.1.1 I_AC and I_FB Sensing Inputs
The rectified AC input voltage (V_rect) and boosted PFC output
voltage (V_link) are sensed as currents into the IC. The sensing
currents are set by resistors R_AC and R_FB, respectively:
R_FB
=
V_{-----l-i--n--k----–-----}V_----d---d-
I_ref
R_FB
=
---⁴----⁰---⁰-----–----¹----²----
129 × 10^–6
R_FB = 3.0MΩ
[Eq.6]
R_AC = R_FB
R_AC = 3.0MΩ
[Eq.7]
Maximum power dissipation in each sense resistor is
calculated as follows (the equation ignores the voltage drop
across R_IAC & R_IFB):
P(R_FB)
=
-^V----^l-ⁱ--ⁿ--^k---²-
R_FB
[Eq.8]
P(R_FB)
=
---⁴----⁰---⁰----²----
3 × 10⁶
P(R_FB) = 53.3mW
P(R_AC)max
=
[_---V_{----i--n---(-m-----a---x--)--}]_--²_-
R_AC
P(R_AC)max
=
----²---⁶---⁵----²----
3 × 10⁶
P(R_AC)max = 23.4mW
[Eq.9]
12
DS849A7