Application Note

VISHAY GENERAL SEMICONDUCTOR
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Rectifiers
Application Note
Fundamentals of Rectifiers
Within the diode family rectifiers are the largest class. One
talks about rectifiers, if the specified current is above 0.5 A.
Below 0.5 A one normally talks about diodes.
Rectifiers are primarily used, as their name already
indicates, for conducting in one direction and blocking in the
other.
Within rectifiers there are several groups depending on the reverse recovery characteristic (reverse recovery time trr):
• Standard rectifiers with a trr > 500 ns
• Fast rectifiers with a 100 ns < trr < 500 ns
• Ultrafast rectifiers with a trr < 100 ns
• Schottky rectifiers with majority carrier effect
Except Schottky rectifiers all these are of p-n junction
technology with different processes to optimize the
characteristics for different applications. They are placed in
different packages, leaded like the Sinterglass, SMD like
DO214AC (SMA) or TO-220 to fullfill different mounting and
power requirements.
Because of their predominant rectifying qualities, rectifiers
are primarily used for power or signal conditioning in a
variety of applications. This can range from high power
output rectifier applications (e.g. power plants, railways,...)
to low power switching rectifier requirements (e.g. mobile
phone chargers, energy saving lamps,...). They are also
used in several other specialized ways like clamping
networks for SMPS (e.g. BYT42), damper and modulator
diodes for the deflection circuits in CRTs (e.g. BY228),
freewheeling diodes for inductive loads etc.
Current I
For specialized rectifying applications, silicon controlled
rectifiers (SCRs) are used. But these are not simply diodes
they have a third terminal, the gate.
The other special group of rectifiers, the Schottky rectifiers,
are not use the conventional p-n junction, they have a barrier
metal design. These are also non controlled rectifiers with
two terminals only. Their big advantage is the excellent
switching characteristic compared to even the fastest p-n
junction diode. For more details about Schottky rectifiers,
please refere to Application Note “Fundamentals of
Schottky Rectifiers”
Figure 1. below shows the basic rectifier characteristics with
the two regions, the forward conducting region, in which the
forward current IF flows and the reverse blocking region, in
which the reverse leakage current IR flows.
Forward Surge
Current Region
VF at IF
Voltage V
VF ≈ 1 V
IR at VR
Reverse
Blocking
Region
Avalance
Breakdown
Region
Fig. 1 - Basic Rectifier Characteristics
Revision: 06-Aug-15
Document Number: 88867
1
For technical questions within your region: [email protected], [email protected], [email protected]
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000
APPLICATION NOTE
Typically
VR = 100 V to 2500 V
Forward
Conducting
Region
Application Note
www.vishay.com
Vishay General Semiconductor
Fundamentals of Rectifiers
The major parameters for the selection of the appropriate
rectifier are the maximum reverse voltage (VRRM), the
average forward current (IF(AV)) and for switching application
the reverse recovery characteristic (trr) too. Additional
parameters may be, for example forward, surge capability
(IFSM) etc.
BASIC RECTIFIER PARAMETERS
VR
Reverse voltage
VRRM Repetitive peak reverse voltage, including all repeated reverse transient voltages
VBR
Reverse breakdown voltage
IR
Reverse (leakage) current, at a specified reverse voltage VR and temperature TJ
IF
Forward current
VF
Forward voltage drop, at a specified forward current IF and temperature TJ
IF(AV)
Average forward output current, at a specified current waveform (normally 10 ms/50 Hz half sine wave, sometimes
8.3 ms/60 Hz half sine wave), a specified reverse voltage and a specified mounting condition (e.g. lead-length = 10 mm
or PCB mounted with certain pads and distance)
IFSM
Peak forward surge current, with a specified current waveform (normally 10 ms/50 Hz half sine wave, sometimes
8.3 ms/60 Hz half sine wave)
trr
Reverse recovery time, at a specified forward current (normally 0.5 A), a specified reverse current (normally 1.0 A) and
specified measurement conditions (normally from 0 to 0.25 A)
APPLICATION NOTE
Revision: 06-Aug-15
Document Number: 88867
2
For technical questions within your region: [email protected], [email protected], [email protected]
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000
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