IMPROVEMENT TRIAC COMMUTATION RAULT last years, triacs spread are

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IMPROVEMENT TRIAC COMMUTATION RAULT last years, triacs spread are

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IMPROVEMENT TRIAC COMMUTATION
RAULT last years, triacs spread areas electronics, including domestic appliances industrial applications. triacs been traditionally limited their switching behavior applications where there risk spontaneous firing after conduction. order obtain required reliability today's equipment, designer must take certain number precautions: over dimensioning device, switching networks (snubber), significant margin security junction temperature,etc. This generally involves additional costs. After brief discussion commutation problem when triac turned off, this article will describe progress made this area newest possibilities offered triac user thanks series Logic Level SNUBBERLESStriac. commutation problem triac electrical representation triac compared thyristors mounted anti-parallel coupled with control device which allows activation this switch with only gate (fig. 1a). considering structure triac (fig. 1b), notices that conduction zones, corresponding these thyristors which control current direction then other, narrowly overlap each other control zone. Figure During conduction time, certain quantity charges injected into structure. biggest part these charges disappears recombining during fall current circuit, while another part extracted moment blocking inverse recovery current. Nonetheless excess charge remains, particularly neighboring regions gate, which provoke certain cases firing other conduction zone moment when supply voltage circuit reapplied across triac. This problem commutation. given structure determined junction temperature, switching behavior depends quantity charges which remains moment when current drops zero. this number charges linked value current which circulating triac approximately microseconds before cut-off. (This time corresponds three times life time minority carriers). Thus, parameter consider here will slope decreasing current which called commutating di/dt, (di/dt)c. (fig. speed which reapplied voltage increases moment when triac turns off, which called commutating dv/dt, (dv/dt)c. (fig. capacitive current, proportional (dv/dt)c, flows into structure, therefore injected charges added those coming from previous conduction.
Simplified equivalent schematic triac circuit. Example triac structure.
AN439/0592
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Figure Triac voltage current commutation. Characterization order characterize switching behavior triac when turns off, consider circuit which vary slope decrease current (di/dt)c. addition, control slope reapplied voltage using, example, circuit resistors capacitors connected across triac measured. determined (dv/dt)c, progressively increase (di/dt)c until certain level which provokes spontaneous firing triac. This critical (di/dt)c value. Therefore, different (dv/dt)c values, note critical (di/dt)c value each sample. This makes possible trace curve commutation behavior triac under consideration. Figure represents results obtained with standard triac (IGT 50mA) sensitive gate, triac (IGT 10mA). standard triacs critical (di/dt)c sightly modified when vary (dv/dt)c. sensitive gate triacs, this parameter noticeably decreases when slope reapplied voltage increased.
Figure Critical (di/dt)c versus (dv/dt)c (below curve triac turns spontaneously.) rate re-application off-state voltage these points corresponds mains (sinusoidal wave form) zero crossing. (dv/dt)c limited snubber values generally specified data sheets (5V/µs 10V/µs). These points obtained without snubber.
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practice, current wave form, thus (di/dt)c, imposed circuit. Generally cannot change triacs applications always necessary know (di/dt)c circuit order choose triac with suitable critical (di/dt)c. This most important parameter. Suppose circuit which (di/dt)c reaches A/ms. triac characterized upper curve figure suitable such circuit even (dv/dt)c reduced nearly zero connecting huge snubber network across Figure Applications basic circuits When considering constraints commutation turn triac, distinguish cases:
triac resistive load (fig. this case current voltage phase. When triac switches (i.e. when current drops zero), supply voltage nullified this instant will increase across triac according sinusoidal sint
Current voltage ware forms resistive loads Case switching Case phase control
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Example European mains Vrms volts 50Hz, slope will (dv/dt)c Vrms 0.1V/µS This relatively (dv/dt)c corresponds points curves figure (di/dt)c concerned circuit, depends load. resistance loads under Vrms voltage, will have: (di/dt)c Vrms triac inductive load this case there phase between current supply voltage (fig. When currents drops zero triac turns voltage abruptly pushed terminals. limit speed increasing voltage, generally resistive/capacitive network mounted parallel with triac. This "snubber" calculated limit (dv/dt)c volts/µS according specified value data sheet. This case corresponds points figure 3.The (di/dt)c also determined this case load impedance supply voltage.
Figure
Current voltage ware forms inductance loads Case switching Case phase control
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triac without snubber network triac thus considered switch which turns moment when current dampened oscillating circuit constituted loads internal capacity triac (fig. case pure inductive load, maximum reapplied (dv/dt) (dv/dt)c Vrms Irms Figure Triac commutation inductance load without snubber network example, internal capacitance triac about 70pF. Therefore, inductive load, maximum (dv/dt)c without snubber will limited according characteristics load. interesting know behavior triac, particular critical (di/dt)c value, these conditions. This characterization corresponds points curve
progress: TECHNOLOGY make significant progress triac area essentially improve commutating behavior turn triac. other words critical (di/dt)c improved. order reach this goal, structure been developed. this structure, different active zones have been de-coupled Figure maximum such separate elementary thyristors gate area. This made possible sacrificing gate triggering fourth quadrant. practice this does pose problem because gate drive circuits triac generally third first quadrants. (fig.
Basic gale drive circuits (the fourth quadrant used)
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given technology, commutating behavior triacs depends sensitivity gate. correlation between critical (di/dt)c gate current triacs represented figure same chart, results obtained with conventional triacs versus technology triacs. seen, progress that been made this level significant.
performances specifications Figure Correlation between commutating behavior sensitivity. (Measurements performed several lots triacs)
technology been into place with manufacturing series, Logic Level SNUBBERLESS Triacs. data sheets these triacs critical (di/dt)c limit specified maximum junction temperature max). Logic Level triacs this category consider sensitive triacs which maximum gate current (IGT) type 10mA one.
Symbol (dI/dt)c Test conditions VDRM dIG/dt A/ms dV/dt V/µs
data sheets Logic Level triacs minimum (di/dt)c specified following cases: Resistive load with (dv/dt)c 01.V/µs. Inductive load with (dv/dt)c V/µs
example triac specified follows:
Quadrant 25°C 110°C
Suffix
Unit A/ms
dV/dt V/µs either polarity electrode voltage with reference electrode
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SNUBBERLESS TRIACS
This series triacs presently covers range Amps with gate currents 35mA type) 50mA type) according type required.This series been specially designed that triacs switches from state state without external snubber circuit. Whatever nature load, there absolutely risk spurious firing turn triac long functioning under specified (di/dt)c value.
SNUBBERLESS triacs specified critical (di/dt)c values which greater than decreasing slope nominal current sinusoidal configuration. example, slope current triac conducting when current drops zero (di/dt)c Irms 7A/mS 50Hz BTA/BTB16-600BW specified (di/dt)c 14A/ms. following table summarizes characteristics SNUBBERLESS triacs which presently available:
WITHOUT SNUBBER
TYPE
CURRENT VOLTAGE
SUFFIX
(mA)
STATIC dV/dt (V/µs)
(dI/dt)c (A/ms)
800V
800V
800V
800V
800V
800V
800V
800V
advantages Applications Logic Level goal these triacs controlled directly logic circuits microcontrolers like series: Outputs sink currents 20mA line, therefore drive These triacs ideal interface power components supplied volts, such valves, heating resistances, small motors.
specification critical (di/dt)c value both resistive inductive loads allows know margin security circuit relation risk spurious firing, which results improved reliability, optimize performance triac used, which results cost reduction.
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Figure
Light dimmer circuit with ST6210.
LINE FUSE MODE 100k
4.7M
RESET
TOUCH SENSOR
ST6210
PUSH BUTTON
08-400SW
TEST
220k 100k
OSCOUT OSCIN
220k
220k 8MHz POTENTIOMETER
resistors
BZW55C5V6 100u 6.3V
1/4W unless otherwise specified
06PHR385
220n 400V 1N4148
NEUTRAL
1/2W
SNUBBERLESS Triacs commutation SNUBBERLESS triacs specified without limitation (dv/dt)c. With suppression snubber circuit, there noticeable cost reduction. Each SNUBBERLESS triac series specified with critical (di/dt)c value static (dv/dt) highest possible level, taking into consideration gate sensitivity (Igt). minimum specified levels these parameters allows these products circuits where there need high safety factor, such Static relays which load well defined. With conventional triacs difficult
adapt snubber possible cases. SNUBBERLESS triacs resolve this problem. (fig. 10). Figure Solid state relay diagram
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Figure Motor control circuit using SNUBBERLESS triacs network series protection) Figure Example circuit with high (di/dt)c
Motor drive circuits. Figure shows inversion circuit asynchronous motor where spurious firing triac, normally assumed off- state, must absolutely avoided. critical (di/dt)c SNUBBERLESS triacs greater than slope nominal current specific type under consideration. This important several applications, including Circuits which (di/dt)c transient state greater than steady state. This case universal motors controlled phase control circuit. table figure shows SNUBBERLESS triac optimize efficiency circuit.
Circuits which generate wave forms with very high (di/dt)c, such inductive load supplied diode bridge (fig. 13). only limited parasitic inductance circuit.
Figure Universal motor control Triac choise must comply with maximum (dI/dt)c example, SNUBBERLESS triac sufficient control moytor
POWER SUPPLY NOMINAL CURRENT VOLTAGE CURRENT CONTROL 220V/50Hz 110V/60Hz 220V/50Hz 110V/60Hz ARMS ARMS ARMS ARMS TRIAC RANGE (dI/dt)c A/ms A/ms A/ms A/ms STANDARDS TRIAC BTA10-600B BTA16-400B BTA16-600B BTB24-400B SNUBBERLESS TRIAC BTA06-600BW BTA10-400BW BTA10-600BW BTA20-600BW
1200
Maximum transient (dI/dt)c. This parameter depends very much type motor. This type specified A/ms munumum small certain applications could need standard triac.
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CONCLUSION Thanks recent progress made triac technology, designer disposal devices with commutating behavior which compatible with applications 60Hz range. This includes phase control static commutation loads going from watts several kilowatts. capability this generation triacs allows increase reliability circuits, particularly where there risk spontaneous firing even most difficult configurations. reduce cost using sensitive gate, LOGIC LEVEL triacs without need interface between gate logic circuit, utilizing SNUBBERLESS triacs which specified without resistive/capacitive network. Additionally, limit (di/dt)c parameter listed SGS-Thomson Microelectronics data sheets. This permits optimization circuit specifying stricter guidelines choice component.
Information furnished believed accurate reliable. However, SGS-THOMSON Microelectronics assumes responsability consequences such information infringement patents other rights third parties which result from use. license granted implication otherwise under patent patent rights SGS-THOMSON Microelectronics. Specifications mentioned this publication subject change without notice. This publication supersedes replaces information previously supplied. SGS-THO MSON Microelectronics products authorized critical components life support devices systems without express written approval SGS-THOMSON Microelectronics.
1995 SGS-THOMSON Microelectronics Printed Italy rights reserved. SGS-THOMSON Microelectronics GROUP COMPANIES Australia Brazil France Germany Hong Kong Italy Japan Korea Malaysia Malta Morocco Netherlands Singapore Spain Sweden Switzerland Taiwan Thailand United Kingdom U.S.A.
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IMPROVEMENT TRIAC COMMUTATION RAULT last years, triacs spread are

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