AN1514
Application note
VIPower: double output buck or
buck-boost converter using VIPer12A-E/22A-E
Introduction
This paper introduces two double output off-line non isolated SMPS based on the
VIPerX2A-E family. The first SMPS is a Buck converter with two positive outputs and the
second one is a Buck-Boost converter with two negative outputs. The use of VIPer12A-E or
VIPer22A-E in both converters depends on the output power specifications. The power
supplies are operated in off-line mode with an extended wide range of the input voltage,
from 80 to 285 Vac. The target applications are small loads, such as microcontrollers,
motors, displays and peripherals in several industrial and home appliances.
Two converter topologies are introduced in this paper. The considered double output
converters are based on the VIPerX2A-E device family and are suitable for non isolated off-
line applications. VIPerX2A-E is a low cost monolithic smart power with a PWM controller,
start-up circuit and protection integrated on the same chip. The power stage consists of a
vertical Power MOSFET with 730 V breakdown voltage and 0.32 A for VIPer12A-E or 0.56 A
for VIPer22A-E maximum drain current with internal limitation.
The use of a VIPower device makes the design very simple and easy, since several features
are integrated in the smart power IC. The first SMPS is a Buck converter with two positive
outputs and the second one is a Buck-Boost converter with two negative outputs. The use of
VIPer12A-E or VIPer22A-E in both converters depends on the output power specifications.
The power supplies are operated in off-line mode with an extended wide range of the input
voltage, from 80 to 285 Vac.
The target applications are small loads, such as microcontrollers, motors, displays and
peripherals in several industrial and home appliances with power level up to 6-8 W.
September 2007
Rev 2
1/17
www.st.com
Contents
AN1514
Contents
1
2
Off-line double output converters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
VIPer application examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1
2.2
Double output buck converter using VIPer12A-E . . . . . . . . . . . . . . . . . . . . 6
2.1.1
Experimental results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Double output buck-boost converter using VIPer22A-E . . . . . . . . . . . . . . . 9
2.2.1
2.2.2
Experimental results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Thermal measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3
4
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2/17
AN1514
List of tables
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Table 9.
Table 10.
Buck converter specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Component list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Load regulation at V
in
=80V
acrms
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Load regulation at V
in
=285V
acrms
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Buck-boost converter specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Component list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Load regulation at V
in
=80V
acrms
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Load regulation at V
in
=285V
acrms
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Thermal characterization (package: DIP8; R
thj-lead
=45°C/W mounted by socket;
T
amb
=25°C). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3/17
List of figures
AN1514
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Double output buck topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Double output buck-boost topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Converter schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Board layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Board prototype . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Efficiency vs. output power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Converter schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Efficiency vs. output power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
V
in
=80V
acrms
, I
out2
=75 mA, CH1=V
out1
, CH2=I
out1
, CH3=I
Lp
, CH4=V
out2
. . . . . . . . . . . . . 13
V
in
=285V
acrms
, I
out2
=75 mA, CH1=V
out1
, CH2=I
out1
, CH3=I
Lp
, CH4=V
out2
. . . . . . . . . . . . 13
VIPer22A-E temperature at maximum load with parasitic capacitance . . . . . . . . . . . . . . . 13
V
DS
and I
D
at V
in
=230V
acrms
, I
out
=250 mA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Conducted emissions at full load with EN55014 limits: line emissions . . . . . . . . . . . . . . . . 15
Conducted emissions at full load with EN55014 limits: neutral emissions . . . . . . . . . . . . . 15
4/17
AN1514
Off-line double output converters
1
Off-line double output converters
In these circuits the first output is obtained using the standard buck or buck-boost topology,
while the second output is obtained by means of a second winding on the main inductor.
This output is directly coupled with the first one in flyback mode and its value is given by the
turns ratio n. The inductor is still low cost since a drum core can be used and the coupling
between the two windings is not as critical as in a flyback converter. The electrical
schematics of both configurations are shown in
Figure 1
and
Figure 2.
2
VIPer application examples
In this section two VIPerX2A-E application examples are introduced:
1.
2.
Double output buck converter 24 V at 30 mA, 5 V at 50 mA
Double output buck-boost converter (-24 V) at 250 mA, (-5 V) at 70 mA.
Double output buck topology
Figure 1.
Figure 2.
Double output buck-boost topology
5/17
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