General Electronics Thyristor Training
Training Agenda
1.
Thyristor Definition and General Electronics Power Applications
2.
Thyristor Characteristics and Device Physics
3.
Thyristor General Electronics Applications Examples
4.
Thyristor Product Selection
5.
Littelfuse Thyristor Product Road Map
6.
Thyristor Technology Challenges
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1
General Electronics Thyristor Training
Section 1 Thyristor Definition and General Electronics Power Applications
•
Thyristor Definition
–
A semiconductor switch whose bi-stable action depends upon P-N-P-N
regenerative action
•
Thyristor Technology for Power Applications in the General Electronics Segment
–
Thyristors used for phase control
–
Thyristors used as AC static switches and relays
–
Thyristors used for lighting systems
•
Standards Related to Thyristor
–
IEC 60092-304 {Ed.3.0}
–
IEC 60700-1 {Ed.1.1}
–
IEC 60747-6-3 {Ed.1.0}
–
IEC/TR 60919-1 {Ed.2.0}
–
IEC 61643-341 {Ed.1.0}
–
IEC 61803 {Ed.1.0}
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2
Thyristor Definition and General Electronics
Thyristor Definition
–
A semiconductor switch whose bi-stable action depends upon P-N-P-N regenerative action.
–
Littelfuse devices included in the Thyristor family:
Device Name
Description
Feature
Function
SCR
Rectifier with control gate
One Way Switch
Phase Control
Switching
Triac
Two inverse parallel SCRs
Two Way AC Switch
Phase Control
Switching
Sidac
Two way switch without
gate
Triggers from VBO turns-off
depletion of current
Switching
Diac
Two way triggering device
Low voltage VBO Trigger
Switching
Quadrac
Triac and Diac in one
package
Phase Control
Switching
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3
Thyristor Definition and General Electronics
Thyristor Technology in the General Electronics Segment
– Phase Control
• In these applications, thyristors are used to control the magnitude of average voltage or
energy being delivered to a load.
• Due to high-volume production techniques, thyristors are now priced so that almost any
electrical product can benefit from electronic control.
–
AC Static Switches and Relays
• In these applications, thyristors are used to open or close a circuit or isolate a load.
• Since SCRs and the triacs are bistable devices, one of their broad areas of application is in
the realm of signal and power switching.
–
Lighting Systems
• One of the many applications for thyristors is in fluorescent lighting ballasts.
• Standard conventional and circular fluorescent lamps with filaments can be ignited easily and
much more quickly by using thyristors instead of a mechanical starter switch.
• The Sidac device is also widely used in flash ignition circuits.
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4
Thyristor Definition and General Electronics
Thyristor Standards
IEC 60092-304 {Ed.3.0}
Electrical installations in ships. Part 304: Equipment - Semiconductor
convertors
IEC 60700-1 {Ed.1.1}
Thyristor valves for high voltage direct current (HVDC) power
transmission - Part 1: Electrical testing
IEC 60747-6-3 {Ed.1.0}
Semiconductor devices - Discrete devices - Part 6: Thyristors Section Three: Blank detail specification for reverse blocking triode
thyristors, ambient and case-rated, for currents greater than 100 A
IEC/TR 60919-1 {Ed.2.0}
Performance of high-voltage direct current (HVDC) systems with linecommutated converters - Part 1: Steady-state conditions
IEC 61643-341 {Ed.1.0}
Components for low-voltage surge protective devices - Part 341:
Specification for thyristor surge suppressors (TSS)
IEC 61803 {Ed.1.0}
Determination of power losses in high-voltage direct current (HVDC)
converter stations
IEC 61954 {Ed.1.1}
Power electronics for electrical transmission and distribution systems
- Testing of thyristor valves for static VAR compensators
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5
General Electronics Thyristor Training
Section 2
–
–
Thyristor Characteristics and Device Physics
Ratings, Specifications, and Characteristics
•
Electrical characteristics
–
Main terminal characteristics
–
Thyristor turn-on mechanisms
–
Gate characteristics
–
Current holding and latching
–
Turn-on and turn-off time
–
Dynamic characteristics (di/dt, dV/dt)
•
Maximum ratings
–
Peak surge (non-repetitive) on-state Current
•
Thermal characteristics
–
Junction temperature
Device Construction and Basic Operation
•
SCR PNPN operation
•
Triac PNPN operation
•
Sidac PNPN operation
•
Diac NPN operation
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Thyristor Characteristics and Device Physics
Electrical Thyristor Characteristics
Anode-to-Cathode Characteristics
– Forward characteristics:
• Blocking state
• Avalanche region
• Breakover point
• Negative resistance region
• Conducting state
• Holding current point
– Reverse characteristics:
• Blocking region
• Avalanche region
Critical parameters
– IT (On-state Current)
– VRRM (Repetitive Peak Reverse Voltage)
– VDRM (Repetitive Peak Off-state Voltage)
– IH (Holding current)
– IGT (Gate Trigger Current)
Caution About Gate Current and Voltage
– Gate current must be limited to the rated
value to avoid damage to device
– Reverse gate voltage must be limited to
the rated value to avoid damage to device
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Thyristor Characteristics and Device Physics
Electrical Thyristor Characteristics
Gate Characteristics
A Thyristor can be gated or triggered
to the ON state by applying a small
signal between the gate and the
cathode.
The trigger source is a DC voltage and
the gate current must be limited by a
series resistor.
Typical gate trigger methods are as
following
1. DC trigger
2. Pulse trigger
3. AC phase control trigger
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Thyristor Characteristics and Device Physics
Thyristor Switching Methods
1. Applying proper gate signal
2. Exceeding thyristor static dv/dt characteristics
3. Exceeding voltage breakover point
Application of Gate Signal
Gate signal must exceed IGT and VGT requirements of the
thyristor used. For an SCR (unilateral device), this signal
must be positive with respect to the cathode polarity.
A triac can be turned on with a gate signal of either
polarity; different polarities have a different IGT and VGT.
Static dV/dt Turn-on
Static dv/dt turn-on comes from a fast rising voltage
applied across the anode and cathode terminals of an
SCR or the main terminals of a triac.
Due to the nature of thyristor construction, a small
junction capacitor is formed across each PN junction.
When a voltage is impressed suddenly across a PN
junction, a charging current flows, and when C (dv/dt)
becomes greater or equal to Igt, the thyristor switches
on.
Thyristor application circuits are designed with static
dv/dt “snubber” networks if fast rising voltages are
anticipated.
Voltage Breakover Turn-on
This method is used to switch on sidacs and diacs.
In the case of SCRs and triacs, leakage current
increases until it exceeds the gate current required to
turn on these gated thyristors in a small localized point.
When turn-on occurs, localized heating in a small area
may melt the silicon or damage the device if the di/dt is
not sufficiently limited.
Diacs used in typical phase control circuits are usually
protected against excessive current at breakover as
long as the firing capacitor is not excessively large.
When diacs are used in a zener function, current
limiting is necessary.
Sidacs are typically used in pulse-firing, high voltage
transformer applications and are current limited by the
transformer primary. The sidac should be operated so
its peak current amplitude, current duration, and di/dt
limits are not exceeded.
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9
Thyristor Characteristics and Device Physics
Electrical Thyristor Characteristics
Current Holding and Latching
Latching Current (IL) is the minimum principle
current required to maintain the thyristor in the
on state immediately after the switching from
off state to on state has occurred and the
triggering signal has been removed.
Holding Current (IH) is the minimum principle
current required to maintain the thyristor in the
on state. Holding current can best be
understood by relating to the "drop out" or
"must release" level of a mechanical relay.
Device switching sequence: gate, latching,
holding. Holding current will always be less
than latching.
The more sensitive the device, the closer the
holding current value approaches its latching
current value. Holding current is independent
of the gating and latching, but the device must
be fully latched on before a holding current limit
can be determined.
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Thyristor Characteristics and Device Physics
Electrical Thyristor Characteristics
Turn-on Time
tgt is the time interval between the
application of a gate pulse and the on-state
current reaching 90% of its steady-state
value. As would be expected, turn-on time
is a function of gate drive. Shorter turn-on
time is actually only valid for resistive
loading.
Turn-off Time
tq (the circuit commutated turn off time) is the
time during which the circuit provides reverse
bias to the device (negative anode) to
commutate it off. The turn-off time occurs
between the time when the anode current goes
negative and when the anode positive voltage
may be reapplied.
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Thyristor Characteristics and Device Physics
Electrical Thyristor Characteristics
di/dt (Rate of Rise of Current)
The di/dt rating specifies the maximum
rate-of-rise of current through a thyristor
device during turn-on. The value of
principal voltage prior to turn-on and the
magnitude and rise time of the gate
trigger waveform during turn-on are
among the conditions under which the
rating applies. If di/dt exceeds the
maximum value, the localized heating
may cause device degradation.
dv/dt (Rate of Rise of Voltage)
Static dV/dt is the minimum rate-of-rise
of off-state voltage that a device will hold
off, with gate open, without turning on.
Commutative dV/dt is the rate of rise of
voltage across the main terminals that a
triac can support when commutating
from the on state in one half cycle to the
off state in the opposite half cycle.
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Thyristor Characteristics and Device Physics
Maximum Ratings
Peak Surge On-state Current
The Peak Surge current (ITSM)is
the maximum peak current that
may be applied to the device for
one full cycle of conduction
without device degradation.
The maximum peak current is
usually specified as sinusoidal at
50Hz or 60Hz. This rating
applies when the device is
conduction current rated before
the surge and the junction
temperature is at rated values
before the surge. The junction
temperature will surpass the
rated operating temperature
during the surge, and the
blocking capacity may be
decreased until the device
reverts to thermal equilibrium.
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13
Thyristor Characteristics and Device Physics
Thermal Characteristic
Thermal Resistance
VGT, IGT, IH and other key parameters of Thyristors are
a function of temperature.
The heat generated within the semi-conducting
material must be dissipated into a heat sink.
The thermal resistance defines the steady state
temperature difference between two points at a given
rate of heat energy transfer between the points.
Thermal resistance, junction to ambient
RөJA = (TJPK - TA) / PTOT C / W
Junction to case RөJC = (TJPK - TC) / PTOT C / W
Junction to lead RөJD = (TJPK - TL) / PTOT C / W
Where TA = ambient temperature
TC = case temperature
TL = lead temperature
TJPK = peak junction temperature
PTOT = power pulse amplitude
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Thyristor Characteristics and Device Physics
SCR Construction
Cross section of the SCR chip and
illustrations of current flow and junction
biasing in both the blocking and triggered
(forward biased or on-state) modes
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15
Thyristor Characteristics and Device Physics
Triac Construction
Simplified cross-sectional
views of a triac chip in
various gating quadrants
and blocking modes
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16
Thyristor Characteristics and Device Physics
Sidac Construction
The Sidac is a multi-layer silicon semiconductor switch.
The Sidac operates as a bidirectional switch activated by voltage. In the off state, the Sidac exhibits leakage
currents (IDRM) less than 5 µA. As applied voltage exceeds the sidac VBO, the device begins to enter a negative
resistance switching mode with characteristics similar to an avalanche diode. When supplied with enough current
(IS), the sidac switches to an on state, the voltage across the device drops to les than 5 V, depending on magnitude
of the current flow. The switching current (IS) is very near the holding current Ih value.
When the sidac switches, currents of 10A to 100A are easily developed by discharging a small capacitor into a
primary or small, very high voltage transformers for 10us to 20 us.
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Thyristor Characteristics and Device Physics
Diac Construction
The construction of a diac is similar to an open base transistor .
The bidirectional transistor like structure exhibits a high impedance blocking state up to a voltage breakover point
VBO) above which the device enters a negative resistance region. These basic diac characteristics produce a
bidirectional pulsing oscillator in a resistor-capacitor AC circuit.
Since the diac is a bidirectional device, it makes a good economical trigger for firing triacs in phase control circuits
such as light dimmers and moor speed controls.
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General Electronics Thyristor Training
Section 3
Thyristor General Elec Power Applications Examples
–
SCR Application Example
–
TRIAC Application Example
–
Diac Application Example
–
Sidac Application Example
–
Littelfuse Global Lab Application Testing
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19
Thyristor General Electronics Applications Examples
Basic Thyristor Phase Control Unit
SCR Applications
- GFCI
- Smoke detector
- Security alarm
- Drill motor speed control (180
degrees)
- Air freshener control
- Battery charger
- Electrified fence control
- Voltage regulator
- Small gas engine ignition
SCR/Rectifier Applications
- Motor control (full wave DC)
- Drill motor speed control
(360 degrees)
- Treadmill controller
- Power supply
Diac Applications
- Inexpensive timing
switch for phase control
- Variable light output
dimmer
- variable voltage output
MSC (motor speed
control)
Sidac Applications
- High efficiency/high voltage
light ignition
- Appliance (gas) ignition
- Strobe light control
- Visual aids control
- Stage/theater lighting
- Medical HV equipment
- Fluorescent lamp starter
- Air purifier
- Bug killer HV supply
Triac Applications
- Variable level lighting
control
- On/Off solid state
switch/relay
- Speed control (fan, tools)
- Instant (tankless) water
heater
- Food mixer control
- Traffic light control
- Bed control
- Vending machine control
- Washing machine control
- Electronic display control
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20
Thyristor General Electronics Applications Examples
SCR Example
Flywheel,
Rotating magnet
HV Xfmr
D1
R1
N
Charging
Winding
S
C1
S-SCR
Trigger
Winding
Spark
Plug
R2
Small Gas Engine Circuit
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21
Thyristor General Electronics Applications Examples
SCR and Rectifier Combination Controls
Motor Control
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22
Thyristor General Electronics Applications Examples
Triac Example
Isolated Solid State Switch or Relay
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Thyristor General Electronics Applications Examples
Diac Example
Full Wave DC Motor Control
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24
Thyristor General Electronics Applications Examples
Sidac Example
Gas Ignition Circuit
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25
Thyristor General Electronics Applications Examples
Global Lab Capabilities
•
•
•
•
Qualification of all LF products
UL-Approved Customer Testing in ISO 17025 Lab (Des Plaines)
– High power (AC/DC up to 1KV/50KA) UL approvals available in DP
– Telcordia approvals in DP planned (2008)
Verification of Telcordia, ITU, IEC, FCC, and other industry, regulatory, and safety standards
– Verification to various OC and OV standards
• Insure application meets standards before submitting for approval
Customer Application testing
– Assistance with design-in and performance verification
• Help with selection of appropriate technology and rating
– Application troubleshooting
• Assistance insuring proper OV/OC and primary/secondary protection coordination
– Competitive evaluations
• Competitive or technology performance comparisons
– Reliability & Tin Whisker data/testing
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26
General Electronics Thyristor Training
Section 4
–
–
Thyristor General Elec Product Selection
Basic Power Circuit Theory
•
Phase Control
Selection Guide
•
SCR Notes
•
Triac Notes
•
Sidac Notes
•
Diac Notes
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27
Thyristor General Electronics Product Selection
Phase Control Application
Operation Method
1. The thyristor is held in the off condition
2. The thyristor is triggered into an "on" condition by the control circuitry
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28
Thyristor General Electronics Product Selection
SCR Gating: Static Switching
Use a constant or varying DC signal to turn on the SCR
Gate signal can be derived from power source or an independent source
• A small gate current can be used to control a large load current
•SCR used as solid state relay
•Used in electrical control applications
Operation Method
Operation Method
1. The closure of S4 or S5 will fire the SCR
1. The open of S2 or S3 will fire the SCR
2. S3 is to re-set the circuit
2. S1 is to re-set the circuit
3. Used for industrial and control applications
3. Ideal for security alarm systems
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Thyristor General Electronics Product Selection
SCR Gating: AC Static Switching
Operation Method (normally open)
Operation Method
1. Permits low current switching
1. Allow SCR conduction angle less that 90°
2. SCR firing angle from 0 to 90°
2. SCR firing angle anywhere from 0 – 180°
3. R2 eliminated for 360° operation
3. Power applied to the load adjustable from zero to
one-half of maximum full wave load power
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Thyristor General Electronics Product Selection
SCR Gating: Zero Crossing Switching
Operation Method
1. SCR only fires at 0° of the half cycle, the SCR
remains conducting.
2. Special zero crossing detector circuits are used
to determine the instant when the ac line voltage
is zero
3. Used primarily for power control to heating
loads.
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Thyristor General Electronics Product Selection
SCR Gating Requirement
SCR vs. Sensitive SCR
RGK Value Considerations
Sensitive Gate SCR
requires an RGK of about 1K ohms
(typical), triggers with microAmps of
IGT, and is limited to 10Amps max IT
(RMS)
Lower values of RGK further improves
blocking and leakage, improves dV/dt,
increases holding current requirements,
and increases required gate drive
current
Non-sensitive (regular) SCRs have a
shorted emitter (built-in resistor
between gate and cathode) and require
milliAmps of IGT
Higher values of RGK decreases
blocking capability, decreases dv/dt
capability, decreases holding current
requirements, and decreases gate
current requirements
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Thyristor General Electronics Product Selection
Triac Snubber Circuits Considerations
Definition: A snubber is a simple electrical circuit used to
suppress ("snub") electrical transients.
Operation Method
1. A series resistor and capacitor connected across main terminals of the triac
2. Resistor dissipating the energy from transient surge
3. Snubber can be formed by RC network, diode, varistor, zener, and other semiconductor protectors
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Thyristor General Electronics Product Selection
Triac Commutation Considerations
Operation Method
1. For each AC cycle, the triac turns on twice, it must turned off before it can be turned on in the opposite
direction.
2. For turn off, the load current must drop below the holding current (IH).
3. For Inductive loads, the current lags voltage which forces a sudden increase in voltage across the triac; this
may prematurely trigger conduction during the next half cycle.
4. dV/dt (commutating) is the minimum value of the dV/dt that will cause switching form an off state to on state
immediately following on state current conduction in the opposite direction.
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Thyristor General Electronics Product Selection
Triac Phase Control
Operation Method
1. A Sensitive Gate Triac can be
phase controlled from pulsed DC
unidirectional inputs as shown.
2. A microprocessor can be
interfaced to an AC load by using
a sensitive gate triac to control a
lamp's intensity or a motor's
speed.
Operation Method
1. A standard (non-sensitive) triac
or alternistor can also be used,
interfaced through an
optocoupler, also providing
isolation to the microprocessor.
2. The connection between DC
ground and AC neutral is not
required.
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35
Thyristor General Electronics Product Selection
Triac Device Gating Requirement
Device Type
Key Advantages/Disadvantages
Snubber Network
Sensitive Triac
Can be triggered in any two of
four modes and has IGT max spec
for each mode
Normally should have snubbing
due to lowest gate current
requirements
Standard Triac
Is specified for only three of four
triggering modes
Can require snubber network for
certain applications
Alternistor Triac
Is designed with only three
triggering modes in order to
provide best commutating for
inductive loads
Does not necessarily require
snubber network with its
superior dV/dt characteristics
Quadrac
Is triggered by built- in Diac
Can require snubber network
depending on application if it is
not an Alternistor version
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Thyristor General Electronics Product Selection
Diac Device Application Requirement
–Voltage range of diacs is 30 to 70V
–Normally 32 to 35V is used for phase control for wider
control output
–Tighter voltage ranges used to minimize tolerances on
output voltage of control
–Higher voltage diacs are used in conjunction with a
low voltage diac to produce regulated output in phase
controls at lower output levels as AC line input
fluctuates
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Thyristor General Electronics Product Selection
Sidac Device Application Requirement
–Use a low voltage Sidac for 120VAC line or less
–Use a high voltage Sidac for 240VAC line or higher
–Use single pulse Sidacs for High Pressure Sodium lamp
ignition where one pulse per half cycle of 50/60Hz, a 1500V
pulse (10 – 15usec) must be produced to fire HPS lamp
–Use single pulse high voltage Sidacs to ignite gas for stove
tops with a 4 to 10Hz DC pulse of 6 to 10KV
–Use a Multi-pulse Sidac for Metal Halide lamp ignition where
minimum of three pulses per half cycle of 50/60Hz, 4000V
must be produced to fire MH lamp
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38
General Electronics Thyristor Training
Section 5 Littelfuse Thyristor Product Road Map
Power Thyristor Roadmap
Triac Product Family
800V Wire Bond 0.8Amp & 1Amp Triac
8Amp Triac Benchmark Redesign
4Amp Triac Benchmark Redesign
12Amp Triac Benchmark Redesign
16Amp Triac Benchmark Redesign
25Amp Triac Benchmark Redesign
40Amp Triac Benchmark Redesign
High Tj (150C) triac
Low power dissipation triac
TriACtor Family
Integrated triac / optocoupler
SCR Product Family
800V Wire Bond 0.8Amp & 1.5Amp SCR
25Amp SCR Benchmark Redesign
20Amp SCR Benchmark Redesign
4Amp SCR Benchmark Redesign
10Amp SCR Benchmark Redesign
Fast switching SCR
QFN Package SCR
SIDAC Product Family
Multi-Pulse SIDAC
Unidirectional High Current SIDAC
DO-41 Axial Package
DIAC Product Family
Low voltage & tight tolerance DIAC
Minimelf package
Q1 2006
Q2 2006
Q3 2006
Q4 2006
Phase 1
Phase 1
Phase 2
Phase 3
Phase 2
Phase 3
Phase 2
Phase 3
Phase 1
Phase 2
Phase 3
Phase 1
Phase 2
Phase 1
Phase 2
Phase 1
Phase 1
Phase 2
Phase 1
Q1 2007
Q2 2007
Q3 2007
Q4 2007
Phase 3
Phase 3
Phase 2
Phase 1
Phase 1
Phase 1
Phase 1
Phase 3
Phase 1
Phase 1
Phase 1
Phase 1
Phase 2
Phase
Phase
Phase
Phase
Phase 3
Phase 3
Phase 2
Phase 2
Phase 3
Phase 1
Phase 1
Phase 2
Phase 2
Phase 3
Phase 3
Phase 1
Phase 2
2
2
1
1
Phase 2
Phase 3
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39
General Electronics Thyristor Training
Section 6 General Electronics Thyristor Technology Challenges
–
Higher Current/Surge Ratings in Smaller Packages
–
Multiple Elements in One Package
–
Thyristor Isolation from Gate (Opto-Thyristor)
–
UL Recognition of Thyristors
–
Thyristor technology Packaged in Combination With other Technologies
–
Improved De-rating Characteristics & Higher Operating Temperatures
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40