Product Overview

V I S H AY I N T E R T E C H N O L O G Y, I N C .
RECTIFIERS
TMBS ® Guide to Switchmode
Power Supply Applications
TABLE OF CONTENTS
Introduction................................................................................................................................................. 2
Package Summary Details.......................................................................................................................... 2
Applications................................................................................................................................................. 2
Output Rectifiers in SMPS.......................................................................................................................... 3
Notebook Adaptors..................................................................................................................................... 3
Printer +32 V Adaptors................................................................................................................................ 3
Desktop SMPS............................................................................................................................................ 3
Telecom AC/DC Power Supplies................................................................................................................. 4
Telecom DC Systems Isolation.................................................................................................................... 4
Distributed Telecom Power Systems.......................................................................................................... 4
Notebook Polarity Protection...................................................................................................................... 5
OR-ing Diode Applications.......................................................................................................................... 5
Conclusion.................................................................................................................................................. 5
A WORLD OF
SOLUTIONS
Application Guide
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TMBS ® Guide to Switchmode
Power Supply Applications
Introduction
Vishay Semiconductors is the world´s leading supplier of TMBS® Trench MOS Barrier
Schottky rectifiers, offering a number of low-VF, high-speed devices from 45 V to 200 V.
These TMBS rectifiers are backed by a vertically integrated company with over 50 years of
experience in rectifier die fabrication and packaging. This guide serves to provide product
recommendations for device selection in key applications.
Packaging Summary Table
The majority of applications we will cover use the packages shown in the table below.
As demonstrated, there are a wide variety of leaded and surface-mount devices available.
Power Packages
Surface Mount
45 V
TO-220, ITO-220,TO-262 SMPC, SlimSMA, TO-263
60 V
TO-220, ITO-220,TO-262 SMP, SMA, SMB, TO-263
80 V
TO-220, ITO-220,TO-262
100 V
TO-220, ITO-220,
TO-262, TO-3PW
SMPC,SMA, SMB,
TO-263
120 V
TO-220, ITO-220,TO-262
SMPC, TO-263
150 V
TO-220, ITO-220,TO-262
TO-263
170 V
TO-220, TO-3PW
TO-263
200 V
TO-220, ITO-220,TO-262,
TO-3PW
SMB, SMC, TO-263
Axial
P600, DO-201AD
DO-201AD, DO-15,DO-41
Applications
There are literally thousands of applications that use rectifiers. This application note will cover eight key switchmode
power supply (SMPS) applications for TMBS devices, including:
•
Output rectifiers in tablet PC chargers, notebook and printer adaptors, desktop power supplies, LCD TVs, and
telecom DC/DC converters and AC/DC power supplies
•
Telecom DC input/output OR-ing diodes and blocking diodes
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V I S H AY I N T E R T E C H N O L O G Y, I N C .
RECTIFIERS
TMBS ® Guide to Switchmode
Power Supply Applications
Output Rectifiers in SMPS
Vishay Semiconductors is the leader in using Trench MOS technology to improve Schottky rectifier
performance, thereby increasing SMPS efficiency to meet power saving requirements. The company’s
TMBS rectifiers can shorten the design cycle, and improve reliability and lower costs over synchronous
rectifiers by reducing the need for extra control circuitry. Optimizing SMPS designs, TMBS devices
provide lower VF with a good reverse leakage current (IR) trade-off to meet the requirements of different
application conditions.
Notebook Adaptors
Most notebook adaptors use fly-back topology, as shown in the
circuit to the right. In the diagram, D2 is the output rectifier of the
adaptor. An R-type 100 V or 120 V TMBS rectifier with excellent VF
can provide a fly-back converter for higher performance. An M-type
120 V TMBS device can improve the VF of a conventional planar
Schottky rectifier and maintain a low leakage current for the hightemperature requirements in notebook adaptors.
The TO-220 and ITO-220 packages are most often utilized in
notebook applications. A 120 V TMBS rectifier in an SMPC package
is a good solution in applications requiring a slim adaptor, such as
tablet and smart phone chargers, which also use fly-back topology.
L- and R-type 45 V TMBS devices in SMPC packages can provide
the low profile and high performance required in these applications.
Printer +32 V Adaptors
+32 V is the DC output voltage for multifunction inkjet printers. Since the output current
is small, 200 V TO-220, ITO-220, or axial TMBS
rectifiers provide simple, low-cost solutions for
this application.
Desktop SMPS
Desktop SMPS often use 60 V to 100 V
Schottky rectifiers as +12 V output rectifiers.
60 V to 100 V TMBS rectifiers can provide low
VF to reduce power loss and increase efficiency.
45 V Schottky devices are ideal for +5 V
and +3.3 V output rectifiers. With their low VF,
R- and L-type 45 V TMBS provide good desktop SMPS solutions to
meet the 80+ iron and bronze standards of installed cooling fans.
To lower costs and shorten the design cycle, it is helpful for SMPS
designers to use the most popular forward converter topologies. To
the right is a basic two-switch forward converter topology circuit,
where D1 to D6 are the output rectifiers. TMBS devices can be used
to easily achieve the 80+ bronze standard.
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TMBS ® Guide to Switchmode
Power Supply Applications
Telecom AC/DC
Power Supplies
Since telecom AC/DC power
supplies feature outputs from
24 VDC to 72 VDC, 150 V, 170 V,
and 200 V TMBS rectifiers are
suitable solutions for these high-power, high-reliability
applications that often utilize full-bridge softswitching technology. In the diagram, D1 and D2 are
the output rectifiers of a telecom AC/DC SMPS, for
which TMBS rectifiers are ideal solutions for meeting
high-performance and high-reliability requirements.
Telecom DC
Systems Isolation
Blocking diodes are used in telecom systems
to isolate DC power input by AC/DC power
supplies or battery banks. With their low VF
characteristic, 80 V to 200 V TMBS rectifiers
provide good blocking for DC power input
systems.
Distributed Telecom
Power System Isolation
Distributed telecom power systems often
use point-of-load (POL) converters to
provide the specified DC power to the POL,
as shown in the illustration. Due to system
space limitations, converters with higher switching frequencies
must be used to increase the power density and reduce the
converter volume. For this application, TMBS rectifiers provide
excellent switching performance and lower conduction losses
than conventional Schottky or ultrafast rectifiers. A comparison
of the VF and Trr of the three device types is shown below. As
demonstrated, TMBS rectifiers are the best solution for this highperformance and high-reliability application.
Switching of 200 V Schottky (IF = 6 A, di/dt = -200 A/µS, VR = 200 V, 10 %, TA = 100 °C
Planar Schottky
SBR Schottky
200 V TMBS
JF (A/cm2)
TMBS VF
is the best
VF (V)
TMBS
Application Guide
Planar Schottky
Ultrafast 1
TA = 125 °C
Ultrafast 2
Ultrafast 3
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V I S H AY I N T E R T E C H N O L O G Y, I N C .
RECTIFIERS
TMBS ® Guide to Switchmode
Power Supply Applications
Notebook Polarity Protection
Power adaptors for notebook computers
use blocking diodes for DC input polarity
protection. In the illustration, D1 is the polarity
protection rectifier. A 45 V SMPC TMBS rectifier
provides the low VF, low profile, and good heat
dissipation required in notebook designs.
OR-ing Diode Applications
OR-ing diodes are simple solutions for multiinput or redundant power system in some
high-end or high-reliability applications, as
demonstrated in the illustration to the right.
TMBS rectifiers can provide low-power-loss
solutions for OR-ing diode applications.
Conclusion
TMBS rectifiers improve on the weak points in the designs of conventional planar devices to provide better voltage
drop and switching performance. They also provide better VF than ultrafast rectifiers in 200 V applications. TMBS
rectifiers are ideal solutions for meeting power saving requirements in a variety of applications across the world
market.
Application Guide
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