AN829 Datasheet, PDF (1/9 Pages) STMicroelectronics – SEMICONDUCTOR KIT FOR

AN829
APPLICATION NOTE
SEMICONDUCTOR KIT FOR
POWER FACTOR CORRECTOR
by J.M. Borgeous
This paper present a new line of P.F.C. dedicated products. Both silicon and packaging have been op-
timized to reduce system cost, including filtering. The products shown here are offered as a kit for power
factor correction.
BOOST CIRCUIT OPTIMIZATION PARAMETERS
Among the available topologies, a boost circuit operating in continuous current mode is the only topology which
enables the RFI noise across the input capacitor to be limited, and consequently a lower cost filter is required.
Also, the boost inductor stores only a part of the transferred energy, because the mains still supplies energy
during the demagnetization phase of the boost inductor - so the magnetic part required is smaller than needed
with any other topology. Therefore the boost topology leads to the cheapest solution. Figure 1 shows the general
topology of a boost PFC. Its optimization requires careful adjustment of the following parameters:
– the value of the input capacitor C_i
– the current ripple in the boost inductor L_b
– the parasitic capacitances of the boost inductor and power semiconductors, including those associ-
ated with the heatsink
– the operating frequency and also the frequency modulation technique.
Figure 1. Semiconductor Kit for PFC Schematic.
Lp3
Lp4
Lb
Lp1
A
C1
+ STE30NA50-DK
Lp2
STH80N05
Lp5
4
7
1/KY
any
6
X
compensation ₁₃
VREF 14
8
9
-
+
ONE CHIP
L4981A/B
CONTROLLER
10
FREQ. MODUL.(B)
SYNCHRON. (A)
+
+
-
20
1
FULL
PROTECTION
5
D95IN252A
November 2003
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