Introduction to Rectifiers

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Introduction to Rectifiers Powered By Docstoc
					                                                                                                                   MicroNote
                                                                                                                   Series 301
                                                      by Kent Walters, Microsemi Scottsdale




Introduction                               parameters of greatest interest for a
                                           simple rectifier are the rated values
                                                                                                  well as Standard and General
                                                                                                  Purpose Rectifiers.


to Rectifiers
                                           of average forward current Io and the
                                           working peak reverse voltage VRWM.                     Another class of Schottky Rectifiers
                                           This latter feature can also be                        using a barrier metal design rather
                                           referred to as peak inverse voltage                    than a p-n junction technology is
                                           (PIV) or VPK. and sometimes as                         described separately in the 400
                                           repetitive peak reverse voltage VRRM                   series of MicroNotes. Rectifier
Rectifiers are the largest class of
                                           when including all repeated reverse                    Bridges, Arrays, Power Modules,
products in the diode family. They are
                                           transient voltages. The rectifier                      Hybrids, or Assemblies will be in the
primarily used for blocking in one
                                           avalanche breakdown voltage V(BR) is                   500 series. Silicon Controlled
direction and conducting in the other.
                                           not always specified, but is typically                 Rectifiers (SCRs) will be described in
These include General Purpose,
                                           20% or more greater than the rated                     the 600 series. Another class of PIN
Standard, Fast, UltraFast, Signal/
                                           VRWM or VRRM.                                          diodes now being used in a variety of
Switching, High-voltage and Schottky
Rectifiers. Except for Schottky                                                                   RF switching applications will also
                                              Additional parameters may include                   be described in the 700 series of
rectifiers, all are of p-n junction
                                           forward surge current ratings IFSM or                  MicroNotes.
technology with different processing
                                           other provided characteristics such
features to optimize parametric
                                           as forward voltage V at various                                     Kent Walters
requirements for the variety of                                  F
                                           currents I . Other parametric features                            Manager of Corporate
applications implied by their titles. In             F
                                           will be further described in this 300                            Application Engineering
addition, these diode products can
                                           series of MicroNotes for various                                Telephone: (602) 941-6524
be further placed into more useful
                                           specialized applications requiring                                 Fax: (602) 947-1503
packaged configurations of bridges,
                                           Fast, UltraFast, Signal/Switching, as
half bridges, doublers, center taps,
arrays, or power modules
Sometimes these are also referred to
as packaged assemblies or hybrids.           *VRWM    = Working Peak Reverse Voltage
                                             IR       = Reverse Current                                          Current
Because of their predominant                 VF       = Forward Voltage at I F
                                                                                                       IFSM
rectifying qualities, they are primarily     IF       = Forward Current
used for power or signal conditioning        *IO      = Average Forward Output Current
                                                        with 180° conduction in 60 HZ
in a variety of applications. This can
                                                        sine wave                                                                  Forward
range from high power output rectifier       *IFSM    = Forward Surge Current Peak with                                           Conducting
applications to very low power signal                   a specified pulse waveform
                                                                                                                                   Region

or switching rectifier diode                 V(BR)    = Breakdown Voltage
requirements. They can also be
used in a variety of other specialized       *        Rated Value
                                                                                                                             VF @ IF
ways including “catch diodes”,
“freewheeling diodes”, or simply                             Typically 50 to 1600 Volt ratings        IO
“clamp diodes” to act as safety valves
for voltage protection.                              V(BR)    VRWM

In specialized “controlled” rectifying                                                                                                Voltage
applications, Silicon Controlled
Rectifiers (SCRs) are applicable.                                                          Reverse
                                                                                                                    1.0 V 2.0 V

However these are not simply                                                               Blocking
                                                                IR                          Region
diodes, since they are “gated” three
terminal structures.
                                                               Avalanche
                                                               Breakdown
The basic rectifier diode parameters                             Region
are shown in Figure 1. The
                                           Figure 1: Basic Rectifier Characteristics and Parameters