CA1273389A - Control circuit for a heating unit - Google Patents
Control circuit for a heating unitInfo
- Publication number
- CA1273389A CA1273389A CA000521962A CA521962A CA1273389A CA 1273389 A CA1273389 A CA 1273389A CA 000521962 A CA000521962 A CA 000521962A CA 521962 A CA521962 A CA 521962A CA 1273389 A CA1273389 A CA 1273389A
- Authority
- CA
- Canada
- Prior art keywords
- lamps
- control
- power
- circuit
- heating unit
- 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.)
- Expired - Lifetime
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Classifications
-
- 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
- H05B3/00—Ohmic-resistance heating
- H05B3/68—Heating arrangements specially adapted for cooking plates or analogous hot-plates
- H05B3/74—Non-metallic plates, e.g. vitroceramic, ceramic or glassceramic hobs, also including power or control circuits
- H05B3/744—Lamps as heat source, i.e. heating elements with protective gas envelope, e.g. halogen lamps
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24C—DOMESTIC STOVES OR RANGES ; DETAILS OF DOMESTIC STOVES OR RANGES, OF GENERAL APPLICATION
- F24C15/00—Details
- F24C15/10—Tops, e.g. hot plates; Rings
- F24C15/102—Tops, e.g. hot plates; Rings electrically heated
- F24C15/106—Tops, e.g. hot plates; Rings electrically heated electric circuits
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Ceramic Engineering (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Control Of Resistance Heating (AREA)
- Electric Stoves And Ranges (AREA)
- Yarns And Mechanical Finishing Of Yarns Or Ropes (AREA)
- Cookers (AREA)
- Sorption Type Refrigeration Machines (AREA)
- Oscillators With Electromechanical Resonators (AREA)
- Selective Calling Equipment (AREA)
Abstract
ABSTRACT
A CONTROL CIRCUIT FOR A HEATING UNIT
A control circuit, for a heating unit including two or three lamps emissive of infra-red radiation, includes a microprocessor for selectively effecting phase and burst-fire control of power supplied to the lamps to generate a desired heat output set by user-operable controls. The circuit also includes switching means to achieve series and/or parallel arrangements of the lamps to generate different power outputs.
The microprocessor is also arranged to provide phase control of power to the lamps intermediate periods of energisation of the lamps during burst-fire control or to alternate between two different power outputs generated by series and/or parallel arrangements of the lamps to achieve an average output.
A CONTROL CIRCUIT FOR A HEATING UNIT
A control circuit, for a heating unit including two or three lamps emissive of infra-red radiation, includes a microprocessor for selectively effecting phase and burst-fire control of power supplied to the lamps to generate a desired heat output set by user-operable controls. The circuit also includes switching means to achieve series and/or parallel arrangements of the lamps to generate different power outputs.
The microprocessor is also arranged to provide phase control of power to the lamps intermediate periods of energisation of the lamps during burst-fire control or to alternate between two different power outputs generated by series and/or parallel arrangements of the lamps to achieve an average output.
Description
~73~
A CONTROL CIRCUIT FOR A HEATING UNIT
Thi~ invention relate~ a control circuit for a heatin8 unit and particular, though not exclusively, to a unit arranged to be mounted in a oooking hob to fonm a hotplate area of a glass oe ramic cook top of the hob.
Heating units of thi~ type are disolo~ed in our corresponding U.K. Patent Application No. 2132060A, wherein, in a preferred embodi~ent, ea2h unit includes four tungstsn-halogen lamps supported above a shallow metallic tray containing a layer of non-metallic, thermally-ir~ulative material. A temperature control arrangement is capable of switching the lamp filament3 into a number of series and/or parallsl c binations providing a corresponding number of d1screte power outputs of the lamps to achieve an optimi3ed characteristic heat output curve. Other temperature control3 may also be used~ 3uch a3 phase control of the lamp filaments below a power level of 200~ and/or bur~t-fire or mark-3pace control above this power level, because it has been found that the use of bur3t-fire control at lower power levels causes visual flickering effects of the lamps, which can be disturbing to a user of the cooking hob.
However, the above-mentioned temperature control of the lamp filaments may be disadvantageous if les~ than four lamps are required, because the pos~ible number of ~eries and/or parallel combinations of the lamp filaments i~ reduced, thereby reducing undesirably the number of pos3ible temperature settines on the cooking hob.
Furthermore, it is also desirable to maintain a balanced '~
t 7~
: 2 output from the lamp arrarlgement oYer thc whole hotplat~ area, which becomes increasingly dlffioult as the nu~ber of la~p~ ls reduced .
It is therefore an ob~ect of the pr sent invention to provide a heating unit including a more fle~ible control arrargement, which enable~ an increased number of heat output~
to be achieved from a reduced number of lamps.
It is a further ob~ect of the invention to provide a heating unit including a control arrangement, which all2viates the problem of di~turbing flickering of the lamps when burst-fire control i9 used at relatively low power levels.
According to one aqpect Or the present invention there iY
provided a control circuit for a heating unit including a plurality of lamps emissive of infra-red radiation, said circuit inoluding switchine mean~ for selectively ~witching said lamps into a plurality of series andJor parallel arrangements, each having a respective power output, u~er-operable means for ~etting a desired heat output from said lamps, and proce~or mean3 to effeot switohing between at least two of said arrangements for predetermined proportions of a burst-fire cycle to achieve ~aid de~ired heat output.
According to a second aspect of the invention there is provided a oontrol circuit for a heating unit including at least one lamp emiQsive of infra-red radiation, ~aid circuit including processor means for effecting burst-fire control of power supplied to said at least one lamp and for effecting phase control of 3aid at least one lamp intermediate periods of continuous energi ation of 3aid at lea3t one lamp during burst-fire control.
The present invention will now be further described by way of example only with reference to the accompanying drawing~, wherein:-Figure 1 shows a plan view of a heating unit including three irfra-red lamps, ~7~
3:
Fieure 2 shows a oircuit for controlling the heat output of the lamps shown in Fl~ure 1, Figure 3 ~ho~s a table illustrating the various configurat~on~ of the lampY in Figures 1 and 2, Figure 4 shows an ~lternative circuit to that 3hown in Figure 2 for controlllng the heat output from a heating unit in¢orporating two lamps, and Figure 5 show3 another oircuit for controlling the heat output from a heating unit incorporating two lamps.
Referring to Figure 1, a heating unit includes a generally circular shallow tray 1, preferably made of metal~ having a layer 2 of t~ermally-insulative materialt such a~ a microporou3 material known a~ Microtherm, di~posed therewithin. Three infra-red lamps 3 to 5 are supported above the layer 2 by two ~uitably-shaped piece~ 6, 7 of thermally-insulative material located re~pectively ad~acent the ends of the lamps 3 to 5.
Each infra-red lamp 3 to 5 consists of a halogenated, quartzS tubular er~velope 8 to 10 respectively, within which a single coil or coiled coil tungsten filament, 11 to 13 respectively, is ~upported. Each end of each lamp 3 to 5 consist~ of a pinch seal (not shown), having electrical connections to the respective end of the lamp filament sealed therein, and each pinch seal is enclosed by a ceramic end cap, such as at 14, to protect the pinch seals.
Th~ heating unit, preferably together with three other heating units, is preferably mounted adjacent the underside of a gla~ ceramic cook-top (not ~hown) of a cooking hob (also not shown), ~o as to form a number of hotplate area~ of the cook-top.
The heating unit also includes a thermal limiting device 15, which is arranged to monitor the operating temperature of the glas~ ceramic cook-top, to ensure that it is not damaged by overheating. The device 15 is arranged to activate a microswitch 16, which di3connects the power supply to the lamps 3 to 5, if the operating temperature of the glas~ ceramic exceed~ a predetermined temperature.
73~
Figure 2 shows a oircuit for providing at least fifteen temperature ~ettings of the heating unit, a~ shown in the table in Figure 3, from only the three la~nps 3 to 5, shawn in Figure 1~ To this end, the circuit enable~ th~ hsat output of the 5 lamp3 to be varied by selecti~rely using either phase control, wherein power is 3upplied to one or more of the lamp~ for variable proportions of each positive half cycle of the 3upply waveform or burst-f~re control, wherein power is supplied intermittently to the lamp or lan~ps for a predetermined number 10 of cycles o~ the ~upply waveform.
The circuit shown in Figure 2 includes the three lamp ~ilaments 11 to 13, the power supplied to which is controlled by three triacs 17 to 19, re pe¢tively.
Overall control of the circuit is governed by a 15 microprocessor 20, pre~erably of type TMS 1000, which has inputs at 21 to user-operable temperature setting controls and may also include temperature feedback controls for ~onitoring the temparature of cooking utensils on the hotplate area of the cooking hob.
Outputs from the microprocessor 20 control a number of gates 22 to 25, and gates 22 to 24 control respectively activation of the triacs 17 to 19. The microproce3sor 20 i~
also connected to a zero cross-over detecting circuit 26, a phase control generating circuit 27, and a triac inhibit circuit 25 28. The three gates 22 to 24, and thu~ triacs 17 to 19, are arranged to effect burst-fire control of the power 3upplied to each of the lamp filaments 11 to 13, in dependence on the setting of the user-operable control and corre~ponding output of the microprocessor 20.
The circuit also includes a relay consisting of switches 29 and 30. With ~witch 29 in position A, a9 ~hown, triac 19 will effect burst-fire control of power supp].ied to filament 13.
However, if ~witch 29 is changed to position B, triac 19 will be connected to the phase control generating circuit 27, 90 that 35 power supplied to filament 13 will be pha~e controlled.
33~3 : 5 Switch 29 therefore snable3 the output of ~llament 13 to be selectively controlled by eithar pha~e control or bur.~t-~ire control. Switch 30 i~ arranged to connect filaments 11 and 13 in ~erie when pha~e control i8 u~ed, a~ de3cribed hereinafter.
A voltage divider circuit 31 provides the appropriate voltage for operation of the relay, from output 32, and of the logic component~, from output 33.
Figure 3 ~how~ lamp filament configuration~, provlded by the circuit in Figure 2, to achieve fifteen heat output~ of the heating unit, with the maximum power o~ each lamp preferably being 600W.
Setting no. 15 generate~ the highe~t power output of 1800W
by having all three filaments 11 to 13 connected in parallel at maximu~ power level, i.eO continuou~ly energi~ed.
Setting no~. 14 to 12 eaoh have filaments 11 and 13 at maximum power and triac 18 is arranged to control power to filament 12 by bur~t-firing. Setting no~. 14 and 13 generate power o~tputs of 1600W and 1400W, re~pectively, by filament 12 being energi~ed for 66~ and 33~ re~pectively, of each bur~t fire cycle, and ~etting no. 12 generate~ an output of 120oW with filament 12 continuou~ly de-energi~ed.
Setting no. 11 generates an output of 1000W by controlling all three filament~ 11 to 13 by bur~t-firing, ~ith filament~ 11 and 13 energi~ed for 58.3~ of the cycle and filament 12 energised for 50% of the cycle. It may be preferable to ~tagger the energisation periods of one or more of the filament~ 11 to 13, to even out the load di~tribution on the main~ ~upply and enqure that at lea~t one lamp is on at any given time.
Setting nos. 10 to 6 provide pha~e control of power ~upplied to filament~ 11 and 13 and bur3t-fire control of power ~upplied to filament 12. The pha~e control i~ aohieved by ~witching 3witch 29 to po~ition B and al~o ~witch 30 from po~ition C a3 ~hown, wherein filament~ 11 and 13 are in parallel, to po~ition D, to connect filament~ 11 and 13 in ~erie~. Triac 17 i~ then inhibited by triac inhibit circuit 28, ~73 : 6:
~hioh i~ connected to an input of ~ate 24, 90 that the output~
of bs~th f`ilaments 11 and 13~ in series 7 are controlled by activation OI triac 19. Triac 18 i9 activated, a~ before, to achieve bur~t-fire control of the output of filament 12.
Fllaments 11 and 13 are phase controlled for ea¢h ~etting 10 to 6 ac 20W, and settings 10 to 6 generate outputs of 800'd, 600W, 450W, 35a~1 and 250~ re~psctively by burst-firing filament 12 for 100~, 70%, 45~, 30% and 12~ of the cycle, respectively.
Setting no~. 5 to 1 generate outputs of 180W, 14~W, 100~3 10 80W and 60W, re~pectively by appropriate pha~e controlling of the power supplied to filaments 11 to 13, connected in series, and having filament 12 continuou~3ly de-energi3ed.
It can be seen that, in each of the configurations, fllaments 11 and 13 are arranged to generate the same outputA
15 and filament 12 generates a lower output than filaments 11 and 13, thereby en uring that a balanced vi~ual effect of the three lamps i~ maintained and also enabling more uniform cooking of certain food~, ~uch as pancakes, which tend to require more intense heat around the periphery of the hotplate area Figure 4 ~hows an alternative circuit, which can be u~ed to control the heat output of` a heating unit accommodating only two lamps having filaments 34, 35. The circuit includes a microprocessor 36, which ha~ input~ 37 from user-operable temperature setting controls and possibly also temperature 25 feedback controls, and also an input from zero cross-over detector circuit 38. The ~icroproces~or 36 has outputs 39, 40 to control operation of triacs 41, 42, re~pectively, which are connected re~pectively to t~e lamp filament3 34, 35. It may also be necessary to include RFI components 43, 44 to reduce 30 unde~irable disturbances in the power ~upply to the filaments 34, 35.
The microprocessor 36 is arranged to select either phase control or burst-fire control of the power supplied to the filaments 34, 35, thereby reducing the number of circuit 35 components required and al~o ~implifying the circuit lay-out.
~733~39 The oircuit ~hown in Figure 4 could, of ¢ourse, be modlfied so as to ¢ontrol a heating unit including more than two lamps 3imply by providing additional triac~ and corre~pondlng outputq from the microprooessor 36.
From the two de~cribed circuits, it can thuq be seen that the pre~ent invention provides aelectable bur3t fire and pha~e control~ of the outputs of the lamp filament~, thereby providing a flexible arrangement that i~ capable of generating a ~ub~tantial number of different heat output~ from the heating unit.
It is also pos~ible with the preRent invention to alternate the~e ~electable control~ by pha3e controllin~ power to a filament~ preferably at 20 W , intermediate period~ of energiQat10n of the filament during bur t-f~re control. In thi3 way~ however law the power output, the lamp remain3 vi~ibly energi~ed, thereby alleviating flickering problem~ o~ the lamps at 1QW power ~etting~, whioh can be di~turbing to a user of the heating unit. Furthermore, by varylng the proportion of bur~t-fire control to pha~e ¢ontrol, a large number of different heat outputs ¢an be obtained.
When a number o~ heating unit~ are mounted in a cooking hob, the microprocessor of the c1rcuits could be u~ed to control the output~ of more than one of the unit~ a~ ~hown in Figure 4 by additional outputs 45 from microproces~or 36 to the lamp filaments of another heating unit.
Figure 5 sho~ a control circuit for controlling the power output~ of two heating unitq, each including two tung~ten-ha'ogen la~p~ and each forming a hotplate area of a cooking hob (not ~hown).
In the circuit, the four lamp filament~ 50 to 53 are each connected in ~erie~ with a triac 54 to 57, respectively.
Filament~ 50 and 51 are provided to heat hotplate A and filamentY 52 and 53 are to heat hotplate B. Triac~ 55 and 57 are connected in 3erie~ with RFI components 58, 59, reYpectively, as ~hown in the circuit in Figure 4.
~7.;~
A microproces~or 60 oontrols conduction Or ths triac3 51~ to 579 and thus energisation of tha filament~ 50 to 53, ln accordance with user-oparable switches SA and SB, which ~et the required heat output~ from hotplate~ A and B, respectively.
5 Switches SA and SB preferably each con~i~t of a Gray Code slider or rotary switch, which generate~ a binary output directly readable by the microproce~or 60 and is advantageous in that only one digit change~ on ar,y transition from one setting to another.
S~itche3 SA and SB have inputs I1 to Ill into the microproce3~0r 60 and, if both ~witche3 SA and S}~ are on ~imultaneously, ie. heat output i9 required fro~ both hotplate3 A and B, the microproce~or 60 ~electively sample~, via output~
1 and 2~ the re3pective inputl from ~witches SA and SB.
The microprocessor 60 i3 also connected to a zero-cros~oYer detector circuit 61, via output 03 and input I1, and to a triac ~iring circuit, via output3 04 to 07, which re~pectively operate~ triacs 54 to 57.
Relays RA~ and R.q2 are inoluded in the circuit for 20 hotplate A and relays RB1 and RB2 for hotplate B, 80 as to 3witch the filament~ 50 and 51 in hotplate A and filament~; 52 and 53 in hotplate B into serie3 or parallel arrangements, ~uch that, when filament3 50 and 51 are in 3erie3, power to both of them is controlled by triac 55, and, when filament3 52 and 53 25 are in 3erie3 power to both of them i~ controlled by triac 57.
Outputs 8 and 09 from microproce3~0r 60 control a relay protection and drive circuit 63, which operates the relays RA1 and RA2 and/or RB1 and RB2 and prevent~ arcing through the circuit when the relays are changed.
Inputs I5 to Ig to the microproces30r 60 control the clock frequency of the microproces~or.
Different power outputs from the filaments of each hotplate can thu~ be achieved by pha3e control, ~eries conneatlon of the filament3, parallel connection of the filament~, series 35 connection in combination with a diode, and parallel connection in combination with one or more diode~.
33~1'3 : 9:
Po~er output~ bolow 200W can be achieved by phase control alone. To alleviate the aforementioned ~lickering effect of the lamps, above 200W9 outputs are preferably achieved by switching the filaments between a number~ pre~erably two~ o~ the above conneotions, with or without dlodes, for proportiors of a predetermined burst-fire cycle.
The diodes are proYided by the triacs 54 to 577 which are cau~ed to function as diodes by the microprocessor 60.
A specific example of power outputs achieved by the circuit is ~hown below, wherein fifteen temperature settings are provided with two la~p filament~, each of 900W.
SETTIN PHASE CONTROL OF FILAMENTAPPROX. PO~ER
NO. ARRANGEMENT FOR % AGE OF CYCLE OUTPUT (W) 1 Phase control 60 15 2 Pha~e control 76 3 Phase control 98 4 Phase control 124 Phase control 159 6 Phase control 200 20 7 hase control-54~. Series with diode-46% 260 8 erie~ with diode-93~. Series 7S 35o 9 eries with diode 69~. Series 31%419 eries with diode-28%. Series - 72%534 11 eries - 84% Parallel with diode~ 16S 681 2512 eries 40% Parallel with diode~ 60% 868 13 arallel with diodes - 90%. Parallel - 10% 1107 14 arallel with diodes - 51S. Parallel - 49~ 1411 Parallel - 100% 1800 If~ for example, setting no. 9 is required for hotplate A, this setting ls set on switch SA, which passes the correct signal to the microprocessor 60, via inputs I1 to I4. The microprocessor then positions relays RA1 and RA2, via outputs 8 and 09 and relay protection and drive cirouit 63, so that filaments 50 and 51 are in series and power to the two filaments is then controlled, via output 05 by triac 55, ~ ~73;~
~.~
: 10 whieh operates a3 a diode for 69% o~ a bur3t-fire cyole pre-set by the microproces~or 60 and continuously conduets for the remaining 31S oP the eycle.
The filament arrangements are preferably only ~witoh~d between two arrangements having power outputs adjacent eaeh other in order of magnitude of the power outputs of all ths arrangements, so that any undesirable flickerlng of the lamp~ is mlnimised.
It can be seen that, by this circuit, it qhould be possible to achieve an infinite number of temperature setting~q by varying the proportionq of the eyele oeeupied by each filament arrangement.
However~ uqually le~qs than ~ifteen 3ettings are, in Pact 7 required, the re~peetive outputs of whieh ean be salected a~
required.
Although the cireuit in Figure 5 i3 intended to control the filament~ for two hotplates, only a ~imple modification would be required to enable the circuit to eontrol only one or more than two hotplates by changing the number of triacs, swit¢he~, 2Q relays, ete.
Furthermore, by ehanging the number of triacs and relays, the circuit could easily be modified to eontrol one or more heating unitq, eaeh ineluding more than two lamps, whieh would then be capable of providing other arrangements eonsi3ting of eombination~ of serie3 and parallel eonnneetions, as shown, for example, in Figure 3.
A CONTROL CIRCUIT FOR A HEATING UNIT
Thi~ invention relate~ a control circuit for a heatin8 unit and particular, though not exclusively, to a unit arranged to be mounted in a oooking hob to fonm a hotplate area of a glass oe ramic cook top of the hob.
Heating units of thi~ type are disolo~ed in our corresponding U.K. Patent Application No. 2132060A, wherein, in a preferred embodi~ent, ea2h unit includes four tungstsn-halogen lamps supported above a shallow metallic tray containing a layer of non-metallic, thermally-ir~ulative material. A temperature control arrangement is capable of switching the lamp filament3 into a number of series and/or parallsl c binations providing a corresponding number of d1screte power outputs of the lamps to achieve an optimi3ed characteristic heat output curve. Other temperature control3 may also be used~ 3uch a3 phase control of the lamp filaments below a power level of 200~ and/or bur~t-fire or mark-3pace control above this power level, because it has been found that the use of bur3t-fire control at lower power levels causes visual flickering effects of the lamps, which can be disturbing to a user of the cooking hob.
However, the above-mentioned temperature control of the lamp filaments may be disadvantageous if les~ than four lamps are required, because the pos~ible number of ~eries and/or parallel combinations of the lamp filaments i~ reduced, thereby reducing undesirably the number of pos3ible temperature settines on the cooking hob.
Furthermore, it is also desirable to maintain a balanced '~
t 7~
: 2 output from the lamp arrarlgement oYer thc whole hotplat~ area, which becomes increasingly dlffioult as the nu~ber of la~p~ ls reduced .
It is therefore an ob~ect of the pr sent invention to provide a heating unit including a more fle~ible control arrargement, which enable~ an increased number of heat output~
to be achieved from a reduced number of lamps.
It is a further ob~ect of the invention to provide a heating unit including a control arrangement, which all2viates the problem of di~turbing flickering of the lamps when burst-fire control i9 used at relatively low power levels.
According to one aqpect Or the present invention there iY
provided a control circuit for a heating unit including a plurality of lamps emissive of infra-red radiation, said circuit inoluding switchine mean~ for selectively ~witching said lamps into a plurality of series andJor parallel arrangements, each having a respective power output, u~er-operable means for ~etting a desired heat output from said lamps, and proce~or mean3 to effeot switohing between at least two of said arrangements for predetermined proportions of a burst-fire cycle to achieve ~aid de~ired heat output.
According to a second aspect of the invention there is provided a oontrol circuit for a heating unit including at least one lamp emiQsive of infra-red radiation, ~aid circuit including processor means for effecting burst-fire control of power supplied to said at least one lamp and for effecting phase control of 3aid at least one lamp intermediate periods of continuous energi ation of 3aid at lea3t one lamp during burst-fire control.
The present invention will now be further described by way of example only with reference to the accompanying drawing~, wherein:-Figure 1 shows a plan view of a heating unit including three irfra-red lamps, ~7~
3:
Fieure 2 shows a oircuit for controlling the heat output of the lamps shown in Fl~ure 1, Figure 3 ~ho~s a table illustrating the various configurat~on~ of the lampY in Figures 1 and 2, Figure 4 shows an ~lternative circuit to that 3hown in Figure 2 for controlllng the heat output from a heating unit in¢orporating two lamps, and Figure 5 show3 another oircuit for controlling the heat output from a heating unit incorporating two lamps.
Referring to Figure 1, a heating unit includes a generally circular shallow tray 1, preferably made of metal~ having a layer 2 of t~ermally-insulative materialt such a~ a microporou3 material known a~ Microtherm, di~posed therewithin. Three infra-red lamps 3 to 5 are supported above the layer 2 by two ~uitably-shaped piece~ 6, 7 of thermally-insulative material located re~pectively ad~acent the ends of the lamps 3 to 5.
Each infra-red lamp 3 to 5 consists of a halogenated, quartzS tubular er~velope 8 to 10 respectively, within which a single coil or coiled coil tungsten filament, 11 to 13 respectively, is ~upported. Each end of each lamp 3 to 5 consist~ of a pinch seal (not shown), having electrical connections to the respective end of the lamp filament sealed therein, and each pinch seal is enclosed by a ceramic end cap, such as at 14, to protect the pinch seals.
Th~ heating unit, preferably together with three other heating units, is preferably mounted adjacent the underside of a gla~ ceramic cook-top (not ~hown) of a cooking hob (also not shown), ~o as to form a number of hotplate area~ of the cook-top.
The heating unit also includes a thermal limiting device 15, which is arranged to monitor the operating temperature of the glas~ ceramic cook-top, to ensure that it is not damaged by overheating. The device 15 is arranged to activate a microswitch 16, which di3connects the power supply to the lamps 3 to 5, if the operating temperature of the glas~ ceramic exceed~ a predetermined temperature.
73~
Figure 2 shows a oircuit for providing at least fifteen temperature ~ettings of the heating unit, a~ shown in the table in Figure 3, from only the three la~nps 3 to 5, shawn in Figure 1~ To this end, the circuit enable~ th~ hsat output of the 5 lamp3 to be varied by selecti~rely using either phase control, wherein power is 3upplied to one or more of the lamp~ for variable proportions of each positive half cycle of the 3upply waveform or burst-f~re control, wherein power is supplied intermittently to the lamp or lan~ps for a predetermined number 10 of cycles o~ the ~upply waveform.
The circuit shown in Figure 2 includes the three lamp ~ilaments 11 to 13, the power supplied to which is controlled by three triacs 17 to 19, re pe¢tively.
Overall control of the circuit is governed by a 15 microprocessor 20, pre~erably of type TMS 1000, which has inputs at 21 to user-operable temperature setting controls and may also include temperature feedback controls for ~onitoring the temparature of cooking utensils on the hotplate area of the cooking hob.
Outputs from the microprocessor 20 control a number of gates 22 to 25, and gates 22 to 24 control respectively activation of the triacs 17 to 19. The microproce3sor 20 i~
also connected to a zero cross-over detecting circuit 26, a phase control generating circuit 27, and a triac inhibit circuit 25 28. The three gates 22 to 24, and thu~ triacs 17 to 19, are arranged to effect burst-fire control of the power 3upplied to each of the lamp filaments 11 to 13, in dependence on the setting of the user-operable control and corre~ponding output of the microprocessor 20.
The circuit also includes a relay consisting of switches 29 and 30. With ~witch 29 in position A, a9 ~hown, triac 19 will effect burst-fire control of power supp].ied to filament 13.
However, if ~witch 29 is changed to position B, triac 19 will be connected to the phase control generating circuit 27, 90 that 35 power supplied to filament 13 will be pha~e controlled.
33~3 : 5 Switch 29 therefore snable3 the output of ~llament 13 to be selectively controlled by eithar pha~e control or bur.~t-~ire control. Switch 30 i~ arranged to connect filaments 11 and 13 in ~erie when pha~e control i8 u~ed, a~ de3cribed hereinafter.
A voltage divider circuit 31 provides the appropriate voltage for operation of the relay, from output 32, and of the logic component~, from output 33.
Figure 3 ~how~ lamp filament configuration~, provlded by the circuit in Figure 2, to achieve fifteen heat output~ of the heating unit, with the maximum power o~ each lamp preferably being 600W.
Setting no. 15 generate~ the highe~t power output of 1800W
by having all three filaments 11 to 13 connected in parallel at maximu~ power level, i.eO continuou~ly energi~ed.
Setting no~. 14 to 12 eaoh have filaments 11 and 13 at maximum power and triac 18 is arranged to control power to filament 12 by bur~t-firing. Setting no~. 14 and 13 generate power o~tputs of 1600W and 1400W, re~pectively, by filament 12 being energi~ed for 66~ and 33~ re~pectively, of each bur~t fire cycle, and ~etting no. 12 generate~ an output of 120oW with filament 12 continuou~ly de-energi~ed.
Setting no. 11 generates an output of 1000W by controlling all three filament~ 11 to 13 by bur~t-firing, ~ith filament~ 11 and 13 energi~ed for 58.3~ of the cycle and filament 12 energised for 50% of the cycle. It may be preferable to ~tagger the energisation periods of one or more of the filament~ 11 to 13, to even out the load di~tribution on the main~ ~upply and enqure that at lea~t one lamp is on at any given time.
Setting nos. 10 to 6 provide pha~e control of power ~upplied to filament~ 11 and 13 and bur3t-fire control of power ~upplied to filament 12. The pha~e control i~ aohieved by ~witching 3witch 29 to po~ition B and al~o ~witch 30 from po~ition C a3 ~hown, wherein filament~ 11 and 13 are in parallel, to po~ition D, to connect filament~ 11 and 13 in ~erie~. Triac 17 i~ then inhibited by triac inhibit circuit 28, ~73 : 6:
~hioh i~ connected to an input of ~ate 24, 90 that the output~
of bs~th f`ilaments 11 and 13~ in series 7 are controlled by activation OI triac 19. Triac 18 i9 activated, a~ before, to achieve bur~t-fire control of the output of filament 12.
Fllaments 11 and 13 are phase controlled for ea¢h ~etting 10 to 6 ac 20W, and settings 10 to 6 generate outputs of 800'd, 600W, 450W, 35a~1 and 250~ re~psctively by burst-firing filament 12 for 100~, 70%, 45~, 30% and 12~ of the cycle, respectively.
Setting no~. 5 to 1 generate outputs of 180W, 14~W, 100~3 10 80W and 60W, re~pectively by appropriate pha~e controlling of the power supplied to filaments 11 to 13, connected in series, and having filament 12 continuou~3ly de-energi3ed.
It can be seen that, in each of the configurations, fllaments 11 and 13 are arranged to generate the same outputA
15 and filament 12 generates a lower output than filaments 11 and 13, thereby en uring that a balanced vi~ual effect of the three lamps i~ maintained and also enabling more uniform cooking of certain food~, ~uch as pancakes, which tend to require more intense heat around the periphery of the hotplate area Figure 4 ~hows an alternative circuit, which can be u~ed to control the heat output of` a heating unit accommodating only two lamps having filaments 34, 35. The circuit includes a microprocessor 36, which ha~ input~ 37 from user-operable temperature setting controls and possibly also temperature 25 feedback controls, and also an input from zero cross-over detector circuit 38. The ~icroproces~or 36 has outputs 39, 40 to control operation of triacs 41, 42, re~pectively, which are connected re~pectively to t~e lamp filament3 34, 35. It may also be necessary to include RFI components 43, 44 to reduce 30 unde~irable disturbances in the power ~upply to the filaments 34, 35.
The microprocessor 36 is arranged to select either phase control or burst-fire control of the power supplied to the filaments 34, 35, thereby reducing the number of circuit 35 components required and al~o ~implifying the circuit lay-out.
~733~39 The oircuit ~hown in Figure 4 could, of ¢ourse, be modlfied so as to ¢ontrol a heating unit including more than two lamps 3imply by providing additional triac~ and corre~pondlng outputq from the microprooessor 36.
From the two de~cribed circuits, it can thuq be seen that the pre~ent invention provides aelectable bur3t fire and pha~e control~ of the outputs of the lamp filament~, thereby providing a flexible arrangement that i~ capable of generating a ~ub~tantial number of different heat output~ from the heating unit.
It is also pos~ible with the preRent invention to alternate the~e ~electable control~ by pha3e controllin~ power to a filament~ preferably at 20 W , intermediate period~ of energiQat10n of the filament during bur t-f~re control. In thi3 way~ however law the power output, the lamp remain3 vi~ibly energi~ed, thereby alleviating flickering problem~ o~ the lamps at 1QW power ~etting~, whioh can be di~turbing to a user of the heating unit. Furthermore, by varylng the proportion of bur~t-fire control to pha~e ¢ontrol, a large number of different heat outputs ¢an be obtained.
When a number o~ heating unit~ are mounted in a cooking hob, the microprocessor of the c1rcuits could be u~ed to control the output~ of more than one of the unit~ a~ ~hown in Figure 4 by additional outputs 45 from microproces~or 36 to the lamp filaments of another heating unit.
Figure 5 sho~ a control circuit for controlling the power output~ of two heating unitq, each including two tung~ten-ha'ogen la~p~ and each forming a hotplate area of a cooking hob (not ~hown).
In the circuit, the four lamp filament~ 50 to 53 are each connected in ~erie~ with a triac 54 to 57, respectively.
Filament~ 50 and 51 are provided to heat hotplate A and filamentY 52 and 53 are to heat hotplate B. Triac~ 55 and 57 are connected in 3erie~ with RFI components 58, 59, reYpectively, as ~hown in the circuit in Figure 4.
~7.;~
A microproces~or 60 oontrols conduction Or ths triac3 51~ to 579 and thus energisation of tha filament~ 50 to 53, ln accordance with user-oparable switches SA and SB, which ~et the required heat output~ from hotplate~ A and B, respectively.
5 Switches SA and SB preferably each con~i~t of a Gray Code slider or rotary switch, which generate~ a binary output directly readable by the microproce~or 60 and is advantageous in that only one digit change~ on ar,y transition from one setting to another.
S~itche3 SA and SB have inputs I1 to Ill into the microproce3~0r 60 and, if both ~witche3 SA and S}~ are on ~imultaneously, ie. heat output i9 required fro~ both hotplate3 A and B, the microproce~or 60 ~electively sample~, via output~
1 and 2~ the re3pective inputl from ~witches SA and SB.
The microprocessor 60 i3 also connected to a zero-cros~oYer detector circuit 61, via output 03 and input I1, and to a triac ~iring circuit, via output3 04 to 07, which re~pectively operate~ triacs 54 to 57.
Relays RA~ and R.q2 are inoluded in the circuit for 20 hotplate A and relays RB1 and RB2 for hotplate B, 80 as to 3witch the filament~ 50 and 51 in hotplate A and filament~; 52 and 53 in hotplate B into serie3 or parallel arrangements, ~uch that, when filament3 50 and 51 are in 3erie3, power to both of them is controlled by triac 55, and, when filament3 52 and 53 25 are in 3erie3 power to both of them i~ controlled by triac 57.
Outputs 8 and 09 from microproce3~0r 60 control a relay protection and drive circuit 63, which operates the relays RA1 and RA2 and/or RB1 and RB2 and prevent~ arcing through the circuit when the relays are changed.
Inputs I5 to Ig to the microproces30r 60 control the clock frequency of the microproces~or.
Different power outputs from the filaments of each hotplate can thu~ be achieved by pha3e control, ~eries conneatlon of the filament3, parallel connection of the filament~, series 35 connection in combination with a diode, and parallel connection in combination with one or more diode~.
33~1'3 : 9:
Po~er output~ bolow 200W can be achieved by phase control alone. To alleviate the aforementioned ~lickering effect of the lamps, above 200W9 outputs are preferably achieved by switching the filaments between a number~ pre~erably two~ o~ the above conneotions, with or without dlodes, for proportiors of a predetermined burst-fire cycle.
The diodes are proYided by the triacs 54 to 577 which are cau~ed to function as diodes by the microprocessor 60.
A specific example of power outputs achieved by the circuit is ~hown below, wherein fifteen temperature settings are provided with two la~p filament~, each of 900W.
SETTIN PHASE CONTROL OF FILAMENTAPPROX. PO~ER
NO. ARRANGEMENT FOR % AGE OF CYCLE OUTPUT (W) 1 Phase control 60 15 2 Pha~e control 76 3 Phase control 98 4 Phase control 124 Phase control 159 6 Phase control 200 20 7 hase control-54~. Series with diode-46% 260 8 erie~ with diode-93~. Series 7S 35o 9 eries with diode 69~. Series 31%419 eries with diode-28%. Series - 72%534 11 eries - 84% Parallel with diode~ 16S 681 2512 eries 40% Parallel with diode~ 60% 868 13 arallel with diodes - 90%. Parallel - 10% 1107 14 arallel with diodes - 51S. Parallel - 49~ 1411 Parallel - 100% 1800 If~ for example, setting no. 9 is required for hotplate A, this setting ls set on switch SA, which passes the correct signal to the microprocessor 60, via inputs I1 to I4. The microprocessor then positions relays RA1 and RA2, via outputs 8 and 09 and relay protection and drive cirouit 63, so that filaments 50 and 51 are in series and power to the two filaments is then controlled, via output 05 by triac 55, ~ ~73;~
~.~
: 10 whieh operates a3 a diode for 69% o~ a bur3t-fire cyole pre-set by the microproces~or 60 and continuously conduets for the remaining 31S oP the eycle.
The filament arrangements are preferably only ~witoh~d between two arrangements having power outputs adjacent eaeh other in order of magnitude of the power outputs of all ths arrangements, so that any undesirable flickerlng of the lamp~ is mlnimised.
It can be seen that, by this circuit, it qhould be possible to achieve an infinite number of temperature setting~q by varying the proportionq of the eyele oeeupied by each filament arrangement.
However~ uqually le~qs than ~ifteen 3ettings are, in Pact 7 required, the re~peetive outputs of whieh ean be salected a~
required.
Although the cireuit in Figure 5 i3 intended to control the filament~ for two hotplates, only a ~imple modification would be required to enable the circuit to eontrol only one or more than two hotplates by changing the number of triacs, swit¢he~, 2Q relays, ete.
Furthermore, by ehanging the number of triacs and relays, the circuit could easily be modified to eontrol one or more heating unitq, eaeh ineluding more than two lamps, whieh would then be capable of providing other arrangements eonsi3ting of eombination~ of serie3 and parallel eonnneetions, as shown, for example, in Figure 3.
Claims
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS :
1. A control circuit for controlling the power setting of a heating unit including a plurality of infra-red emmissive lamps, said control circuit comprising user-operable means for selecting any one of a number of different power settings, switching means for selectively connecting said lamps into a number of different series and or parallel configurations, means for effecting phase control of power supplied to the lamps, and processor means for effecting burst-fire control of power supplied to the lamps thereby to define a first sequence of energisation periods at a first level of energisation and a second sequence of energisation periods, interleaved with said first sequence, at a second level of energisation, said processor being arranged to select a said lamp configuration and or permit said phase control for each said energisation period of said first and second sequences thereby to attain said first and second levels of energisation in accordance with a power setting selected by said user-operable means.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8527683 | 1985-11-09 | ||
| GB858527683A GB8527683D0 (en) | 1985-11-09 | 1985-11-09 | Control circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1273389A true CA1273389A (en) | 1990-08-28 |
Family
ID=10587999
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000521962A Expired - Lifetime CA1273389A (en) | 1985-11-09 | 1986-10-31 | Control circuit for a heating unit |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0223503B1 (en) |
| AT (1) | ATE76243T1 (en) |
| CA (1) | CA1273389A (en) |
| DE (1) | DE3685300D1 (en) |
| ES (1) | ES2030662T3 (en) |
| GB (1) | GB8527683D0 (en) |
| GR (1) | GR3005152T3 (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2634614A1 (en) * | 1988-07-20 | 1990-01-26 | Scholtes Ets Eugen | POWER CONTROL DEVICE, IN PARTICULAR FOR COOKTOP HOMES OR THE LIKE |
| DE3840360A1 (en) * | 1988-11-30 | 1990-05-31 | Ego Elektro Blanc & Fischer | RADIATION RADIATOR |
| GB2237940A (en) * | 1989-09-14 | 1991-05-15 | Electrolux Components Ltd | Power controller for electric hotplate |
| DE4004508A1 (en) * | 1990-02-14 | 1991-08-22 | Gaggenau Werke | Power control for ohmic load e.g. cooking hob - using combination of symmetrical oscillation packet control and DC-free half-wave control |
| GB2246253B (en) * | 1990-06-23 | 1994-02-16 | Ceramaspeed Ltd | Switch arrangement for a heater assembly |
| FR2679628A1 (en) * | 1991-07-23 | 1993-01-29 | Europ Equip Menager | Method for feeding a heat source and heat source equipped with its feed control allowing implementation of the said method |
| GB2336255B (en) * | 1998-04-08 | 2002-03-13 | Gen Domestic Appliances Ltd | Cooking appliance energy regulator |
| GB2339347A (en) * | 1998-07-09 | 2000-01-19 | Gen Domestic Appliances Limite | Cooking appliance heating unit |
| US8274020B2 (en) * | 2010-05-04 | 2012-09-25 | Whirlpool Corporation | Apparatus and method of controlling a triple heating element of a cooking appliance |
| EP2798907B1 (en) * | 2011-12-26 | 2015-09-16 | Arçelik Anonim Sirketi | Oven wherein the power of the heater is controlled |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2060329A (en) * | 1979-10-11 | 1981-04-29 | Thorn Domestic Appliances Ltd | Cooking hobs |
| US4443690A (en) * | 1981-12-23 | 1984-04-17 | General Electric Company | Power control for cooking appliance with transient operating modes |
| AT399976B (en) * | 1982-02-10 | 1995-08-25 | Bosch Siemens Hausgeraete | CIRCUIT ARRANGEMENT FOR HEATING ELEMENTS IN COOKING BASIN |
| GB2132060B (en) * | 1982-12-24 | 1985-12-18 | Thorn Emi Domestic Appliances | Heating apparatus |
| DE3334425A1 (en) * | 1983-09-23 | 1985-04-11 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | Additional switching device for a hotplate or cooking point which is integrated into a cooking hob or the like and has at least two heating resistors as the load |
| AU4688985A (en) * | 1984-09-11 | 1986-03-20 | Thorn Emi Appliances Ltd. | Heating apparatus |
| GB2170665B (en) * | 1985-02-02 | 1988-09-21 | Thorn Emi Appliances | Heating unit |
-
1985
- 1985-11-09 GB GB858527683A patent/GB8527683D0/en active Pending
-
1986
- 1986-10-31 CA CA000521962A patent/CA1273389A/en not_active Expired - Lifetime
- 1986-11-05 EP EP86308615A patent/EP0223503B1/en not_active Expired - Lifetime
- 1986-11-05 AT AT86308615T patent/ATE76243T1/en not_active IP Right Cessation
- 1986-11-05 ES ES198686308615T patent/ES2030662T3/en not_active Expired - Lifetime
- 1986-11-05 DE DE8686308615T patent/DE3685300D1/en not_active Expired - Lifetime
-
1992
- 1992-07-13 GR GR920401496T patent/GR3005152T3/el unknown
Also Published As
| Publication number | Publication date |
|---|---|
| GB8527683D0 (en) | 1985-12-11 |
| ATE76243T1 (en) | 1992-05-15 |
| DE3685300D1 (en) | 1992-06-17 |
| EP0223503B1 (en) | 1992-05-13 |
| EP0223503A1 (en) | 1987-05-27 |
| GR3005152T3 (en) | 1993-05-24 |
| ES2030662T3 (en) | 1992-11-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed | ||
| MKEC | Expiry (correction) |
Effective date: 20121205 |