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Semiconductor Components Industries, LLC, 2002
January, 2002 – Rev. 0
1 Publication Order Number:
AND8078/D
AND8078/D
A Simple Low-Cost
Non-Isolated Universal
Input Off-Line Converter
Prepared by: Roland Saint–Pierre
Field Applications Engineer
INTRODUCTION
Switch–mode off–line power conversion typically entails
a means of galvanic isolation from primary to secondary. In
most instances it includes a step–down high frequency
transformer, which aids in the voltage conversion necessary
from the high DC bulk voltage generated from the bridge
rectifier to the lower output DC voltage required by the end
application. If isolation is not a requirement of the
application, in which safety can be insured by mechanical
means, the additional cost of the transformer and
opto–coupler can be saved. The circuit describe herein is
proposed as a simple and low cost means to convert the AC
mains voltage to a lower DC voltage which may be used in
a variety different applications which include a
pre–regulator for a linear voltage regulator.
Circuit Description
The circuit shown below is a very low cost, universal AC
input, non–isolated converter employing a buck–boost
topology. The simple half–wave rectified AC input provides
a DC voltage to the bulk capacitor (C1), which is then
converted, to the semi–regulated DC voltage required on the
output. For this power level an LC –filter was chosen to
meet conducted EMI requirements. This example describes
the design and analysis of a converter providing 8.0 VDC
at 0.4 A.
Figure 1. Non–Isolated Universal Input Buck–Boost Converter Employing the 60 kHz–NCP1200
D1
1N4006
R1 2.2
L1
2.2 H
100–250 VAC
50/60 Hz
C1
10 F
400 V
R2 2.2
C2
10 F
400 V
L2
2.2 H
Q2
2N3904
C3
470 pF
NCP1200P60
HV
GATE IS GND
VCC
C4
0.01 F
8
2
U1
Q1
STD2NB60
C5
220 pF
1 kV
5 3 4
1
C6
22 F
L3
120 H
C7
100 F
10 V
8 VDC
@ 0.4 A
+
–
C6 680 pF
R3
220
D2
1N5924B
9.1 V
D3
1N4937
R4
6
http://onsemi.com
APPLICATION NOTE
Verzeichnis
- ・ Teilenummerierungssystem on Seite 12
- ・ Blockdiagramm on Seite 6
- ・ Anwendungsbereich on Seite 1
