AN4138 Datasheet, PDF (1/20 Pages) STMicroelectronics – This application note presents the HSP061-2

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Application Note AN4138
Design Considerations for Battery Charger Using
Green Mode Fairchild Power Switch (FPS^TM)
Abstract
This application note presents practical design consider-
ations for battery chargers employing Green Mode FPS
(Fairchild Power Switch). It includes designing the
transformer and output filter, selecting the components and
implementing constant current / constant voltage control.
The step-by-step design procedure described in this paper
will help engineers design battery chargers more easily. In
order to make the design process more efficient, a software
design tool, FPS design assistant that contains all the
equations described in this paper is also provided. The
design procedure is verified through an experimental
prototype converter.
Bridge
rectifier
diode
AC line
V_DC
+
C_DC
-
R_sn
FPS
Drain
GND
FB Vcc
H11A817A
C_B
-
C_sn ^V_sn
+
Np
D_sn
R_a
D_a
C_a
N_a
D_R
L_P
N_S
C_{O CP}
V_bias
R_d
H11A817A
Figure 1. Basic Battery charger Using FPS
V_O
I_O
I_Oref
Current
Controller
V_Oref
Voltage
Controller
1. Introduction
As penetration rates of portable electronics devices such as
cellular phones, digital cameras or PDAs have increased
significantly, the demands for low cost battery chargers are
rising these days. Fairchild Power Switch (FPS) reduces
total component count, design size, weight and, at the same
time increases efficiency, productivity, and system reliability
when compared to a discrete MOSFET and controller or
RCC switching converter solution. Table 1 shows the FPS
lineup for a battery charger application. Figure 1 shows the
schematic of the basic battery charger using FPS, which
also serves as the reference circuit for the design process
©2003 Fairchild Semiconductor Corporation
described in this paper. An experimental flyback converter
from the design example has been built and tested to show
the validity of the design procedure.
Device
Switching
frequency
FSDH0165 100 kHz
FSD311 67 kHz
FSD200 134 kHz
FSD210 134 kHz
Current
limit
0.35 A
0.55 A
0.32 A
0.32 A
Rdson (typ.)
15.6 Ω
14 Ω
28 Ω
28 Ω
Table 1. FPS lineup for a battery charger
Rev. 1.0.0