AU636793B2 - A circuit arrangement for control of a triac - Google Patents

A circuit arrangement for control of a triac Download PDF

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Publication number
AU636793B2
AU636793B2 AU83480/91A AU8348091A AU636793B2 AU 636793 B2 AU636793 B2 AU 636793B2 AU 83480/91 A AU83480/91 A AU 83480/91A AU 8348091 A AU8348091 A AU 8348091A AU 636793 B2 AU636793 B2 AU 636793B2
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AU
Australia
Prior art keywords
triac
control means
circuit arrangement
alternating voltage
supply source
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
AU83480/91A
Other versions
AU8348091A (en
Inventor
Philip Anthony Tracy
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Philips Electronics Australia Ltd
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Philips Industries Holdings Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Philips Industries Holdings Ltd filed Critical Philips Industries Holdings Ltd
Priority to AU83480/91A priority Critical patent/AU636793B2/en
Publication of AU8348091A publication Critical patent/AU8348091A/en
Application granted granted Critical
Publication of AU636793B2 publication Critical patent/AU636793B2/en
Assigned to PHILIPS ELECTRONICS AUSTRALIA LIMITED reassignment PHILIPS ELECTRONICS AUSTRALIA LIMITED Request to Amend Deed and Register Assignors: PHILIPS INDUSTRIES HOLDINGS LIMITED
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D23/00—Control of temperature
    • G05D23/19—Control of temperature characterised by the use of electric means
    • G05D23/20—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F3/00—Non-retroactive systems for regulating electric variables by using an uncontrolled element, or an uncontrolled combination of elements, such element or such combination having self-regulating properties
    • G05F3/02—Regulating voltage or current
    • G05F3/04—Regulating voltage or current wherein the variable is ac
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/08—Modifications for protecting switching circuit against overcurrent or overvoltage
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B1/00—Details of electric heating devices
    • H05B1/02—Automatic switching arrangements specially adapted to apparatus ; Control of heating devices
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B39/00—Circuit arrangements or apparatus for operating incandescent light sources
    • H05B39/04—Controlling
    • H05B39/08—Controlling by shifting phase of trigger voltage applied to gas-filled controlling tubes also in controlled semiconductor devices

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Power Engineering (AREA)
  • Electromagnetism (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Control Of Electrical Variables (AREA)

Description

I
636793
AUSTRALIA
PATENTS ACT 1990
COMP
L
ETE SPECIFICATION FOR A STANDARD PATENT 4*e% 4* 4; 44 O R I G I I A L Name of Applicant: Actual Inventor: Address for Service: Invention Title: Ic V. S (4 S 4 PHILIPS INDUSTRIES HOLDINGS LIMITED PHILIP ANTHONY TRACY PATENT ANP TRADE MARKS DIVISION, PHILIPS INDUSTRIES HOLDINGS LIMITED BLUE STREET, NORTH SYDNEY, NSW 2060 "A CIRCUIT ARRANGEMENT FOR CONTROL OF A TRIAC" 8441 4 *V44 44 01 0 4 The following statement is a full description of this invention including the best method of performing it known to us.
-1- PHC 35595 LA 23.8.91 The present invention relates to a circuit arrangement wherein a load is supplied via a triac with current -rom an alternating voltage supply source under the control of a triac control means in combination with a sensing element.
In circuit arrangements of the above type it is known in certain applications for the load and sensing element to be located remotely from the said triac and said triac control means. For example in heaters it is desirable to locate the load a heating element) and the sensing element (i.e.
10 a temperature sensing resistance), in close proximity to a So. mass being heated, whereas it may be desirable to locate the said triac and the said triac control means some distance from the mass being heated. It has been known to use in these circuit arrangements a three lead connection system with a common lead connecting the load and the sensing element to one side of the alternating voltage supply source, with a second lead coupling the sensing element to the. said triac control means and a third lead coupling the load via the said triac to the other side of the alternating voltage supply source.
2For triggering purposes the gate of the said triac is *connected to the alternating voltage source via a network comprising a gate current limiting resistance and an auxiliary triac which is triggered by the said triac control means, the o power for the said triac control means being supplied by a power supply path comprising a resistance and the said triac control means connected across the alternating voltage supply source. Apart from the expense of providing the auxiliary triac and it's associated circuitry, a disadvantage of such a circuit arrangemert is that there is the risk of excessive voltages being applied to the sensing element causing damage thereto if all three connections are not made simultaneously when the alternating supply voltage is present. In addition, with such a circuit arrangement so as to avoid excessive gate current damaging the triacs, the gate current limiting resistance should meet the strict requirement of having a i i ~minimum resistance value to reliably trigger the said triac I 1 t PHC 35595 2 23.8.91 but large enough to ensure a realistic heat dissipation since practically the whole of the alternating supply voltage is dropped across it when both the triacs are in the conducting state.
It is an object of the present invention to minimise -he above disadvantages and to this end the invention comprises a circuit arrangement wherein a load is supplied via a triac with current from an alternating voltage supply source under the control of a triac control means in combination with 1 0i a sensing element, said circuit arrangement comprising said triac, sensing element and load coupled to a common junction and a first and a second supply path for energising the triac control means, the f irst supply path comprising the serial combination of a first resistance, the triac control means and *1 5 the load across the alternating voltage supply source, the second supply path comprising the serial combination of a second resistance, the triac control means and the triac across the alternating voltage supply source, so that the triac control means is substantially energised by the alternating voltage supply source via the first supply path when the triac is non-conducting and is substantially g energised by the alternating voltage supply source via the second supply path when the triac is conducting. In this way, the load and the sensing element may be located remotely from the said triac and said triac control means utilising a three wire connection system, having the advantage that an auxiliary triac is no longer needed and the attendant problems associated with gate current limiting and those associated with excessive voltage by inadvertent connection of the sensing element when the alternating voltage is present are dispensed with.
A preferred embodiment in accordance with the invention comprises a circuit arrangement wherein the first resistance and the second resistance have such values with respect to each other that more power is supplied to the triac control means when the triac control means is triggering the triac PHC 35595 3 23.8.91 than when the triac control means is not triggering the triac.
This has the advantage that more power is supplied to the triac control means when it is needed for the triggering of the triac and power is not unnecessarily dissipated in the triac control means when it is not triggering the triac.
A further preferred embodiment in accordance with the invention comprises a circuit arrangement wherein the triac control means comprises synchronising means for synchronisation of the triggering of the triac with respect o.o100 to the phase of the alternating voltage supply which is o supplied to the synchronising means via one path when the triac is not conducting and via another path when the triac is conducting.
1 The invention will now be described with reference to the accompanying drawings in which: Figure 1 shows a known circuit arrangement of the kind to which the invention relates.
Figure 2 shows another known circuit arrangement of the kind to which the invention relates.
Figure 3 shows a circuit arrangement in accordance with ::the present invention.
Figure 4 shows a triac control unit suitable for use in the circuit arrangement of figure 3.
00 In the circuit arrangement of figure 1 a load 1, which 5 for instance may be the heating element of an electrical S* appliance is connected in series with the main current path of a triac device 2 between the output terminals 3 and 4 of a mains alternating voltage supply source (not shown), the terminals of the triac 2 for it's main current path being denoted respectively as T1 and T2. A triac control unit 5 in the form of an integrated circuit device is energised by supply current derived from the mains alternating voltage supply source by way of a current supply path connected across the terminals 3 and 4 and extending via a supply resistance 6, a power supply terminal 7 and a common terminal 8 of the i control unit 5. Triggering pulses are generated by a trigger PHC 35595 4 23.8.91 Pulse generator (not shown) provided within the control unit in a manner which is responsive to the voltage developed across a sensing element 9 in the form of a temperature dependent resistance connected between a terminal 10 and the terminal 8 of the triac control unit 5, the triggering pulses so generated being supplied from a trigger output terminal 11 of the triac control unit 5 to a gating electrode 12 of the triac 2. The triggering pulses applied to the gate electrode 12 causes the triac 2 to conduct and substantially all of the 0 alternating voltage appears across the load 1 which is ,**dissipated as heat to the mass required to be heated. Once the triggering pulses are no longer applied, the triac 2 stops conducting and no alternating voltage is present across the load 1 and heating of the mass ceases. The sensing element 9 is located in proximity to the mass being heated by the load 1 so that a temperature control system is formed by the triac control unit 5 in combination with the sensing element 9. The control system being such that generation of triggering pulses is determined by whether or not the voltage developed across the sensing resistance element 9 is above or below a given *:~::*reference level.
It is necessary for the triac control unit 5 to be voltanueusply surled ih ordrrtene ris e a encurren continuusl supplired ith cudrrtoeneroms thdiec altert supply source not shown forming part of the control unit 5, which is needed to provide direct current for the trigger pulse generated within the control unit 5 and for circuitry associated therewith, inter alia for the synchronisation of operation as the triac control unit 5 are already known, one such unit is the integrated circuit device type TDA1024 published in the Philips Data HnboIn'tegrated circuits, Part 6, March 1983.
In the circuit arrangement depicted by figure 1, the connections respectively between the terminal 3 and the load 1, between the terminal T2 and the load 1, between the PHC 35595 5 23.8.91 terminal 10 and the sensing element 9, and between the common terminal 8 and the sensing resistance element 9 are partially shown in the form of dotted lines so as to signify that the load 1 and the sensing resistance element 9 are located remotely from the triac 2 and the triac control unit 5. It will be appreciated that a four wire connection system is in use and that a four terminal plug and socket assembly is employed in a practical version of the circuit arrangement.
It is evident that cost savings can be achieved if a three to wire connection system and associated three terminal plug and socket assembly is able to be employed in lieu thereof.
The circuit arrangement of Figure 2 shows a circuit -j arrangement of the kind to which the invention relates in which a three wire connection system is utilised for providing suitable connections between a triac and it'Is associated triac control unit and a remotely located load and it's sensing element. In the circuit arrangement of figure 2, like parts to those of figure 1 are denoted by like references and 0 symbols.
N i the circuit arrangement of f igure 2, a common lead 4.,connecting the load 1 and also the sensing element 9 to the terminal 4 of the alternating voltage supply source is provided and in this way a three wire connection system is achieved with the end of the load 1 remote f rom the common lead being connected to the terminal T2 of the triac device 2 and the end of the sensing element 9 remote from the common lead being connected to the terminal 10 of the triac control unit 5. However, in such a circuit arrangement it is necessary to employ an auxiliary triac in order to satisfactorily supply gating current to the triac 2, this being accomplished by means of the triac 13. In f igure 2, the trigger output terminal 11 of the control unit 5 is connected to the gate electrode 14 of the auxiliary triac 13 with the main current path terminal Ti of the auxiliary triac 13 being connected to the terminal 4 and the terminal T2 of the triac 13 being connected via a gate current limiting resistance 15 to the gating electrode 12 of the triac 2.
PHC 35595 5 23.8.91 With the circuit arrangement of figure 2, it will be readily be understood that the common junction of the load 1 and the sensing resistance element 9 must also be connected to the common terminal 8 of the triac control unit 5. The resultant circuit configuration is for the triac 2 to be arranged with it's terminal T1 connected to terminal 3 of the alternating voltage supply source and for the common terminal 8 of the triac control unit 5 to be connected to terminal 4 of the alternating voltage supply source. As a consequence, O the trigger output 11 of the triac control unit 5 is no longer *able to be directly connected to the gate electrode 12 of the triac 2 since excessive voltages between the trigger output 11 and the terminal 3 of the alternating voltage supply source 6 would be applied directly to the gate electrode 12 thereof.
1*15 For this reason, the auxiliary triac 13 is provided intermediate the trigger output 11 of the triac control unit and the gate electrode 12 of the triac 2.
As previously indicated, the resistive value of the gate current limiting resistance 15 should be chosen so that the 260 gating current is of sufficient magnitude to reliably trigger the triac 2 but should be sufficiently high that excessive heat is not dissipated therein.
Aside from the provision of the auxiliary triac 13 and it's associated circuitry, the circuit arrangement of figure 2 is fundamentally similar to that of figure 1 and the operation thereof is likewise similar.
The circuit arrangement of Figure 3 shows a circuit arrangement of the kind to which the invention relates in which a three wire connection system is utilised for providing suitable connections between a triac and it's associated triac control unit and a remotely located load and it's sensing element. In the circuit arrangement of figure 3, like parts i to those of figures 1 and 2 are denoted by like references and symbols PH 359 72.89 In the cici ragmn'fFiue3 omnla o the ci1rcuite arranm entoie3 common lead bigcnetdt cnnetn thooafndas the sensing element 9 toot thmtecmmnla en comnetdth terminal 0 of the triac control unit ispovdden 5::1 ina this wyatrwr connection is achieve with the endcurntptho ofe telad 1 reweote fomtu thermonal leaeng onnted toin triaoftealternating voltage supply source andtrinlT2o the tic2bigconnected to the temial1topte t coteroil nt3. The loadgerisg conetelssres wignrthdb the mai crntrpathnof thiera 2upu betwee the otput tenrminls 3und 4 tof the atins btentetria3oftealternating voltage supply suctetria 2o h torce 2n be conecte topl theuput terminal 3. teThe ctrern ulses beiang generted byutheytreicacnro unit c5nnece a bmanne ashpeviul describe4ad ae ppied froml ipt trge7ut1 of the triac control unit 5t h gtn eeToe 12ia conhetrli 2. Therisne 6vis connetead between the terminal 3 ofd th altrnaing volrstae supl 'Isuc dtepower supply inputl7 te omo terminal 7 of the triac A aocontrol unit 5, and elad furThesc supply e osistane1 s rsconnece bewentetemln the power supply iemnl7 h on 7emn of the triac control unit 5adtemi urn pthohe triac conro niert5isn wenrgied ia fist ndh sencondsupplyg patsntdll across the mains lteratin votg peetacross the termnal 2 and cmrsn the pwrsstanc 6,r eria8o the triac control unit 5 andrie fo the mapy iscurre 6 via the aforementioned first supply path. Once the triac 2 PHC 35595 8 23.8.91 has been gated by the triggering pulses to the conducting state, the voltage drop across the triac 2 falls to only 1 or 2 volts, and the remainder of the mains supply voltage is dropped across the load 1. Thus when the triac 2 is conducting there is insignificant voltage across the resistance 6 to supply power to the triac control unit 5, and the power required for the triac control unit 5 is derived from the resist.nce 16 via the aforementioned second supply path.
In figure 3, the power supply arrangements for the triac 4.10control unit in accordance with the invention permit the common terminal 8 of the triac control unit 5 and also the terminal Ti of the triac 2 to be connected to the common :junction of the load 1 with the sensing element 9.
Accordingly, i contrast with the circuit arrangement of "145 figure 2, no auxiliary triac is required. Since the terminal Ti of the triac 2 is connected to -the common terminal 8, the danger of excessive high voltages being applied to the electrode 12 of the triac 2 f rom the trigger output 11 is eliminated.
.0 In the circuit arrangement of figure 3, the resistive .**values of 6 and 16 may be chosen relative to each other in such a manner that more power is supplied to the triac control unit 5 when it is triggering the triac 2 than when it is not, whereby the triac control unit 5 consumes less power when not triggering the triac 2 and avoids unnecessary heat dissipation.
Figure 4 is a schematic diagram partly in block f orm showing, in greater detail than hitherto depicted, the important elements within the triac control unit 5 of f igures 1, 2 and 3. In figure 4, like parts to those of figures 1,2, and 3 are depicted by like references and symbols.
I
In figure 4, a trigger pulse generator 17, when in it's operational state, supplies trigger pulses to the output terminal 11. The operational state or otherwise of the trigger pulse generator 17 is determined by the state of the output 23 of the level sensing circuit 18 having two inputs PHC 35595 9 23.8.91 respectively denoted as 10 and 19. A fixed reference voltage is applied to the input 19 whereas the voltage developed across the sensing resistance element 9 when a source of substantially constant current is supplied thereto is applied to the input 10. The output state of the level sensing circuit and hence the operational state of the trigger pulse generator 17 is dictated at a given instant by whether or not the voltage applied to the terminal 10 is greater or less than the voltage applied to the terminal 19. Synchronisation of the o 00 0.001:0trigger pulses generated by the trigger pulse generator 17 relative to the phase of the alternating supply voltage is controlled by the output 22 of the synchronisation control o circuit 20, which circuit 20 monitors the phase of the alternating supply voltage by detection of the crossover points between consecutive half cycles of the alternating supply voltage, which is derived f rom the supply voltage source and applied to the input terminal 21 of the synchronisation control circuit 20. The input terminal 21 may a be connected via a f irst synchronisation resistance (not 2. 0 shown) to the terminal 3 of the alternating voltage supply source and via a second synchronisation resistance (not shown) to the terminal 4 of the alternating voltage supply source whereby an alternating supply voltage is present at all times o on the input terminal 21 f or purposes of phase monitoring irrespective of whether the tria 2 is conducting or not conducting. In a variant of the triac control unit 5, the input of the synchronisation control circuit 20 may be connected within the triac control unit 5 to the p ower input terminal 7 instead of being connected to the terminal 21, whereby the alternating voltage supply required by the synchronisation control circuit 20 for phase monitoring is supplied via the aforementioned first and second supply paths.
The alternating current supplied via the said first and second supply paths referred to in relation to the previously described circuit arrangement of f igure 3 is completed via the zener diode 24 which conducts fully in the forward directicn ii ~c~~*~u~cunrp~lm~~~ PHC 35595 10 23.8.91 but, in the reverse direction conducts only when the applied voltage present between the power s'apply terminal 7 and the common terminal 8 is in excess of the zener voltage of the zener diode 24.
The zener diode 24 is shunted by the series combination cf the rectifier diode 25 and a large smoothing capacitance 26. Accordingly the capacitance 26 is charged to a fixed level the magnitude of which is determiaed by the zener voltage of the zener diode 24 and serves as a D.C. supply source which 00 is available across the terminals C and E and is also supplied to respectively the trigger pulse generator 17, the level sensing circuit 18 and the synchronisation control circuit for energisation thereof by supply lines not shown.
It will be appreciated that the invention is not limited f ',d5 to the embodiments described herein, but many further variations are possible for those skilled in the art without departing from the scope of the invention. For example the sensing element may be in form of humidity dependent capacitance, whereby the circuit arrangement may have applications in humidity control.

Claims (1)

  1. 23.8.91 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:- 1. A circuit arrangement wherein a load is supplied via a triac with current from an alternating voltage supply source under the control of a triac control means in combination with a sensing element, said circuit arrangement comprising said triac, sensing element and load coupled to a common junction and a first and a second supply path for energising the triac control means, the first supply path comprising the serial combination of a first resistance, the triac control means and the load across the alternating voltage supply source, the second supply path comprising the serial combination of a Ssecond resistance, the triac control means and the triac across the alternating voltage supply source, so that the triac control means is substantially energised by the ,5 alternating voltage supply source via the first supply path when the triac is non-conducting and is substantially energised by the alternating voltage supply source via the second supply path when the triac is conductinq. 2. A circuit arrangement as claimed in claim 1, wherein the first resistance and the second resistance have such values with respect to each other that more power is supplied "to the triac control means when the triac control means is triggering the triac than when the triac control means is not triggering the triac. 3. A circuit ar:angement as claimed in claims 1 or 2, *wherein the triac control means comprises synchronising means for synchronisation of the triggering of the triac with respect to the phase of the alternating voltage supply which is supplied to the synchronising means via one path when the triac is not conducting and via another path when the triac is conducting. 4. A circuit arrangement as claimed in any one of the preceding claims wherein the energy supplied to the said triac i control means from the said alternating voltage supply source I is utilised to energise a direct current supply source Ii therein. PHC 35595 23 91 A circuit arrangement substantially as described herein with ref erence to f igures 3 and 4 of the accompanying drawings. PHILIPS INDUSTRIES HOLDINGS LIMITED 23RD AUGUST 1991 I f I I t Abstract A Circuit Arrangement for Control of a Triac The invention relates to a circuit arrangement wherein a load 1 is supplied via a triac 2 witi current from an alternating voltage supply source under the control of a triac control means 5 in a combination with a sensing e-ement. In the prior art the triac 5 is triggered by an auxiliary triac 13 which in turn is triggered by the triac control means In the present invention the dual power supply paths to the triac control unit 5 permit the common terminal 8 of the triac 44 control unit 5 and also the terminal T1 of the triac 2 to be connected to the common junction of the load 1 with the sensing element 9, thus avoiding the need for the auxiliary triac 13. The circuit arrangement has its principal application in heaters. Fi Fig. 3 i I
AU83480/91A 1990-09-26 1991-08-30 A circuit arrangement for control of a triac Ceased AU636793B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU83480/91A AU636793B2 (en) 1990-09-26 1991-08-30 A circuit arrangement for control of a triac

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
AUPK2501 1990-09-26
AUPK250190 1990-09-26
AU83480/91A AU636793B2 (en) 1990-09-26 1991-08-30 A circuit arrangement for control of a triac

Publications (2)

Publication Number Publication Date
AU8348091A AU8348091A (en) 1992-04-02
AU636793B2 true AU636793B2 (en) 1993-05-06

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Application Number Title Priority Date Filing Date
AU83480/91A Ceased AU636793B2 (en) 1990-09-26 1991-08-30 A circuit arrangement for control of a triac

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU528462B2 (en) * 1978-12-28 1983-04-28 P.I.H.L. Firing circuit for a triac
AU5219190A (en) * 1989-12-12 1991-06-20 Rinnai Corporation A heater control circuit
AU8703791A (en) * 1990-12-03 1992-06-11 Philips Electronics Australia Limited Improved system for triac trigger control in combination with a sensing element

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU528462B2 (en) * 1978-12-28 1983-04-28 P.I.H.L. Firing circuit for a triac
AU5219190A (en) * 1989-12-12 1991-06-20 Rinnai Corporation A heater control circuit
AU8703791A (en) * 1990-12-03 1992-06-11 Philips Electronics Australia Limited Improved system for triac trigger control in combination with a sensing element

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