patent cooperation treaty (pct) published application wo 03 007657 a2

8/6/2019 Patent Cooperation Treaty (PCT) Published Application WO 03 007657 A2

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(12) INTERNATIONAL APPLICATION PllBLlSHED llNDER THE PATENT COOPERATION TREATY (peT)

(19) World Intellectual Property Organization111111111111111111111111111111111111111111111111111111111111111111111111111111111 mllnternalional Bureau

(43) International Publication Date (10) International Publication Number23 January 2003 (23.01.2003) peT WO 03/007657 A2

(51) International Patent Classification': H05B (''1.. DE. DK. DM. DZ. EC. 11. ES. 1'1. OH. (JI) . GI. OIl.OM. IIR.IIlI. ID. 11.. IN. IS. JP. KI. KG. KI'. KR. KZ. LC(21) International Alllllication Number: I'CT/1H02/02577 IX I.R.I.S. IT. I.lJ. LV. MA. MD. MG. MK. MN. MW.MX. MZ. NO. NZ. OM. I'll. PI.. IYr. RO. RlI. SD. SE. SG.(22) International Filing Date: 3 July 2002 (0.Hl7.2002) SI. SK. SI.. TJ. 'I'M. TN. TR. 'IT. '1''1.. lIA. lIG. liS. lIl'..

(25) Filing Language: English VN. YU. ZA. ZM. zw.(26) Publication Language: English (84) Designated States ,rel!iOlwl): ARII'O p


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WO 031007(157 PCT/IB02102577

POWER SUPPLY FOR ELECTRICAL RESISTANCE OPERATEDINSTALLATIONS AND APPLIANCES

FIELD OF THE INVENTION

This invention relates to a power supply for electrical resistance operatedinstallations and appliances and to installations and appliances embodyingsame. The invention thus also relates to a method of energizing electricalheat generating resistances.

More particularly, the invention relates to electrical installations andappliances in which electrical resistance elements become heated in order toachieve their objective and thus the invention extends to installationsemploying incandescent electric light bulbs as well as to appliances such aselectric stoves, water heaters (commonly termed geysers in some countries),space heaters (which could be of the radiant type, the oil filled type, or anyother type utilizing electrical resistance heating), as well as to smallerappliances such as kettles, electric frying pans, toasters and the like. Theinvention also, of course, extends to larger scale applications, particularlyindustrial applications, such as the production and processing of metals.

BACKGROUND TO THE INVENTION

Electrical installations and heating appliances of the general type indicatedabove are all typically operated either on a standard alternating current ofeither 110-120 volts or 220-240 volts and a frequency of 50 or 60 cycles persecond or on the direct current output of a battery of some sort or another.Of course, larger installations and appliances are also operated on a threephase supply which in each case results in a phase voltage of about 220volts and 380 volts respectively.


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In the alternative, and in a system that is common in small electricalinstallations such as in rural areas in which the electrical installationcomprises a limited number of light bulbs and other facilities, the powersupply may be a battery or other electrical storage facility that may be

5 energized by an alternative energy supply source such as solar energy orwind or water power.

In either case it has now been found that by operating such installations andappliances with a different type of power supply arrangement certain benefits

10 can be achieved and, most importantly, greater efficiency can be achievedthan would be the case in directly utilizing a standard power supply.

OBJECT OF THE INVENTION

15 It is, accordingly, an object of this invention to provide a power supply forelectrical resistance operated installations and appliances as well asappliances and installations embodying the principles of the power supplythat exhibit improved efficiency of electricity utilization.

20 SUMMARY OF THE INVENTION

In accordance with one aspect of this invention there is provided a powersupply for an electrical installation or appliance presenting a resistive load,the power supply having electrical input means for connection to a supply of

25 electrical energy and output means for connection to a suitable resistiveload; the power supply being characterized in that electronic switchingmeans for switching the electrical power supply to the output means on andoff at a switching frequency of at least about 100 Hz is included to therebycreate a series of cycles each having an "on" and an "off' component with a

30 duty cycle of from about 3 percent to about 90 percent; the power supplyoptionally including one or more inductors, as may be necessary, to provide,


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together with the resistive load, a circuit inductance; and wherein theswitching frequency, dUty cycle, and any inductors in the power supply arechosen so as to cooperate with the resistive load to provide a requiredoperation of the resistive load and wherein the circuit includes means for

5 ensuring that any back emf or transient energy generated across theinductance is dissipated across the resistive load or fed back to the powersupply source, or both.

Further features of the invention provide for the required operation of the10 resistive load to have an enhanced efficiency when compared to the

efficiency thereof in the absence of the said power supply; for the circuit toinclude diode means for ensuring that any back emf or transient energygenerated across the inductance is dissipated across the resistive load orfed back to the power supply source. or both; for the resistance, inductance,

15 duty cycle and frequency to be chosen to ensure operation of the circuit in astate of resonance or a state of oscillation; for the electronic switching meansto be adapted to effect switching at a frequency of between about 800 Hzand 200,OOOHz; for the duty cycle to be from about 5% to 75%, moreparticularly between about 10 and 50% and, preferably I about 15 to 40

20 percent and typically about 25%; for the electronic switching means tocomprise an electronic switch operating in combination with a signalgenerator, the electronic switch optionally being a mos-fet which embodiesdiode means which serve as said diode means defined above, a fet, an IGBTtransisitor, thyristor or other electronic switching device; and for the circuit

25 inductance to be chosen to provide a large back emf.

Still further features of the invention provide for the power supply circuit tooptionally include electrical energy storage means for receiving electricalenergy associated with any back emf or transient energy generated and for

30 returning it to the circuit; and for the electrical storage means to be either abattery, conveniently the same battery as forms the power supply in the case


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of a battery supply, or for the electrical storage means to be a capacitor inthe case of an alternating current power supply.In some cases the inherent inductance of the resistive load may be adequate

5 and in such a case it will not be necessary to add any further inductance toeither the electrical power supply or the resistive load of the circuit. On theother hand, it may be desirable to adjust the inductance in any event in orderto adjust the overall effectiveness of the inductance as may be desirable forany particular resistive load type and with the objective of creating a large

10 back emf or packet of transient energy.

It is to be noted that the exact interrelationship between the resistance of theload, the frequency of switching, the duty cycle and the inductance is not yetfully understood and it is therefore necessary that the various values for any

15 particular application be determined empirically and with suitableexperimentation. It is envisaged, in this regard that special resistive elementsmay need to be designed and produced in order to best employ the featuresof the present invention and, in particular, resistive elements inherentlyhaving a particularly advantageous inductance, may be desirable. It is also

20 to be noted that components, in particular switching devices suitable toconduct an elevated power output level will apparently have to be developedin order to most effectively exploit the advantages provided by this invention.

The resistive load may be that of any appliance, such as an electric stove, an25 electric space heater which could be fan assisted or not, a water heater

(geyser), or on the smaller side, a toaster, a kettle, an electric frying or deepfryer, or any other appliance. The resistive load may, however, also be asimple incandescent light bulb circuit such as may be found in rural areasand which may be based on a battery which is charged using solar and/or

30 wind energy. The power supply of this invention may be built into suchappliance or it may be a separate unit.


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The invention also therefore provides, as an article of commerce, a powersupply unit comprising an electric circuit having an input and an output forconnection between an existing supply of electrical energy and a resistiveload circuit and wherein the power supply unit embodies electronic circuitry

5 adapted to provide an output having the characteristics defined above.

In the latter case the power supply unit can simply be connected betweenthe existing power supply and, for example, an appliance in order to achievethe advantages provided by this invention.

10Still further, the invention provides, as an article of commerce, an applianceembodying a power supply as defined above.

Of course, the invention can also be applied to industrial scale heat15 generating resistances such as those that are commonplace in the metals

processing industry and in the generation of steam for use in numerousdifferent applications.

In addition, the invention also provides a method of operating a heat20 generating resistive load comprising applying, across the resistive load, the

output of a power supply as defined above.

It should also be noted that operation of the power supply of this invention isnot limited to any particular type of input supply of electrical energy although

25 the circuit design of the power supply will in all likelihood vary according tothe nature of the input power supply. Thus, it is envisaged that any voltageinput could be used, typically a voltage appropriate to the relevant sourcethat, in the case of an alternating current supply, is typically 110-120 volts;220-250 volts; or 380 volts, as case may be. In the case of a direct current

30 power supply, the voltage could be that typically inherent in any battery thatis being used as a power supply source or, for that matter, any other source


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of electrical energy such as solar photo panels, wind or water drivengenerators.In order that the invention may be more fully understood various embodiment

5 thereof will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:10

Figure 1 is a schematic circuit diagram of an electricalinstallation or appliance configured to operateaccording to the invention off an alternating currentsupply;

15Figures 2 &3 are schematic circuit diagrams of two variations of

electrical installation or appliance configured to operateaccording to the invention off a direct current supply inthe form of a battery;

20Figures 4 to 7 are similar circuit diagrams of variations of electrical

installations or appliances configured to operateaccording to the invention off an alternating currentsupply;

25Figures 8 to 10 are schematic circuit diagrams of variations of a power

supply unit adapted to be installed between an existingpower supply and an existing appliance, for example;and,

30Figure 11 is a circuit diagram of a still further test circuit.


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DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

Referring firstly to Figure 1 of the drawings, there is illustrated a circuitadapted to be connected to an alternating current power supply, for example,

5 a 230 volt 60 cycles per second power supply. The circuit includes a heatingelement (1) that is connected to the output of a rectifier circuit (2) in turnconnected to the alternating current power supply. The power supply to theheating element is controlled by means of a mosfet (3) adapted, in use, toswitch on and off at a required frequency and with a predetermined duty10 cycle. In this case an inductance (4) is connected in series with the heatingelement (1). The mosfet (3) is fired by a signal generator (5). In thisembodiment of the invention the electrical storage means assumes the formof a capacitor (6) connected across the output from the rectifier.

15 The values of the various components described above will depend entirelyon the circuit and the nature of the load resistor(s) in each individualapplication. In each case the nature of the relevant resistive load and itsown inherent inductance will dictate the value of the added inductance, ifany, which is to be added to the relevant circuit, and at least initially, it is

20 envisaged that this may have to be determined empirically. The capacitor (6)should be capable of operating at maximum anticipated voltages and in thecase of a 230 volt supply, it is anticipated that this may be up to about 440volts. The actual capacitance required may also have to be determinedempirically initially.

25It is envisaged that a circuit of the type described above will operate with asignificant improvement in efficiency of electrical energy utilization. It will beunderstood that, in its application the invention can be applied to any type ofresistive load that generates heat and thus to any of the appliances indicated

30 above as well as to electrical circuits that include incandescent light bulbs.


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Turning now to Figure 2 of the drawings, there is illustrated a circuit similar tothat described with reference to Figure 1 except that the power supply is adirect current power supply of a battery (7) thereby rendering the rectifierunnecessary. In this case the load is illustrated as being a resistance (8) and

5 this could typically be the resistance of an incandescent light bulb or of aplurality thereof. The output from the mosfet (9) is, in this case, very muchthe same as that indicated above although it is expected that the selection offrequency and duty cycle may well have to be optimized for each application.

10 In regard to use in conjunction with batteries, it is envisaged that theinvention may be particularly advantageously employed in that it appearsthat drawing a current from at least certain types of battery may well takeplace in a manner enabling a battery to more efficiently give up its energywhen a circuit according to this invention is employed when compared to that

15 which it would give up if its electrical energy were extracted in a conventionalmanner.

It will be understood that the inclusion or otherwise of an inductance in anycircuit in practice will also be a matter for optimization as the heating

20 resistors may be chosen to exhibit their own inductance in which case theaddition of an inductance may prove to be unnecessary. Alternatively, it mayprove to be advantageous to choose heat generating resistors which exhibitno appreciable inductance and the inductance necessary to give effect tothis invention would then of necessity be added to the circuit.

25Still further, it is not as yet clear as to whether it is always better to place anyadded inductance in series with the load, as indicated by numeral (10) inFigure 2 or if it should be connected in parallel as indicated by numeral (11)in Figure 3.

30The circuit of Figure 3 is otherwise the same as the circuit of Figure 2 andincludes a load resistor (12); a mos-fet (13) and signal generator (14). The


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circuit of Figure 3 was used to develop the test results reported below andwith that end in view it also included a series measurement resistor (15)connected to the negative of the battery; a voltmeter (16) connected acrossthat measurement resistor; and a voltmeter (17) connected across the load

5 resistor (12).

The variations of basic circuits shown in Figures 4 to 7 are all adapted foruse in respect of alternating current supplies. Figure 4 shows a circuit similarto that of Figure 1 but in which the added inductance (18) is connected in

10 parallel with the load resistor (19) and without a capacitor equivalent to thatindicated by numeral (5) in Figure 1.

Figure 5 shows a circuit substantially the same as that of Figure 4 but withthe inclusion of a capacitor (20) equivalent to that indicated by numeral (5) in

15 Figure 1.

Figure 6 shows a circuit in which there is no rectifier but the two half cycles ofan alternating current supply are employed in separate sub-circuits each ofwhich has a load resistor (21,22); any required added inductance (23,24);

20 and its own mosfet (25,26), the two mosfets being of opposite polarity. Thecircuit has. however, only one signal generator (27) connected to fire both ofthe mosfets simultaneously. A diode (28,29) in each of the "live" lines directsthe half cycles to the appropriate mosfet. This circuit has no capacitors to actas temporary storage units whereas the circuit of Figure 7 does have a

25 capacitor (30,31) across each sub-circuit. Apart from that the circuit of Figure7 is identical to that of Figure 6.

It is within the scope of this invention that a power supply unit may besupplied as an article of commerce for inclusion between a conventional

30 power supply and a conventional appliance in order to employ theadvantages provided by this invention in an existing situation.


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There is thus illustrated in Figure 8, a power supply unit indicated by a dottedline (32) having input terminals (33) for connection to an alternating currentpower supply and output terminals (34) that can be connected to the inputterminals (35) of an appliance generally indicated by numeral (36). Of

5 course, any added inductance (37) in the power supply unit, which is shownas being in series with the output terminals (34) may be absent in the eventthat the inductance of the circuit in the appliance is adequate.

Figure 9 illustrates the relevant part of the same arrangement but one in10 which any added impedance (38) is connected in parallel with (ie across) the

output terminals whilst Figure 10 illustrates the same part of sucharrangement but wherein any added impedance (39) is connected in parallelwith (ie across) the load resistor (40) in the appliance.

15 Reverting now to some of the actual tests that have been conducted, thesetests were conducted on a circuit as shown in Figure 3 in which a Fluke 20megahertz bandwidth storage scope meter (with a digital display device)served as the voltmeter (17) to measure the rms voltage drop across theload resistor (12) which in this case was a 10 ohm resistor. The insulated

20 probes were placed across the load. The level of energy dissipated at theload was calculated in line with classical energy computations being theinstantaneous product of volts across the load squared divided by the Ohmsvalue of the resistor over time.

25 The waveform over the load was stored and down loaded to a spreadsheetfor detailed analysis and confirmation of the voltmeter measurements. Thevalues were found to conform to the digitally displayed values.

A carbon measurement resistor (15) of 0.75 Ohms was employed in series30 with the negative terminal of the battery. The applied voltage across the

resistor was measured in the same way. The level of energy delivered bythe battery was calculated in line with classical computations being the


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equivalent temperature rise. A temperature rise to 47 degrees centigradeover a period of 20 minutes was consistent with an applied wattage of 7.5watts or 8.66 volts. A temperature rise to 39 degrees centigrade wasconsistent with an applied wattage of 4.5 watts or 6.7 volts.

5Referring now to the circuit of Figure 11 (which is substantially similar to thatof Figure 3), a higher frequency test was carried out. In this case thenecessary voltage measurements were taken using a calibrated Fluke 199C200 MHz dual channel scope meter whereof the two channels were

IQ connected to measure the voltage across a 24 volt battery (41) as indicatedschematically as a voltmeter (42) and across the shunt (43) as indicatedschematically as a voltmeter (44). The signal generator (45) was adjustableand was set at a duty cycle of 3.7% 'on' at a frequency of 2.4 kHz. Byremoving any resistance from the gate of the mos-fet (46) an oscillating

15 'frequency of between 143 kHz and 200 kHz with the duty cycle ofapproximately 1.3% was achieved.

Utilizing heat dissipation at a steady state temperature in the mannerdescribed above, that in this case was 52 degrees centigrade, it was

20 determined that the wattage extracted utilizing the power supply of thisinvention amounted to 1.13 watts whilst without the power supply of thisinvention the wattage was 17.74 watts. It was concluded that a frequency ofthe order of 200 kHz appeared to be highly appropriate in the case ofimplementation of the invention in instances in which a battery is the source

25 of power.

It will be understood that numerous variations may be made to the circuitsdescribed above without departing from the scope of this invention andadapted in the implementation of the invention empirical tests will have to be

30 done in respect of each application.


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CLAIMS:

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1. A power supply for an electrical installation or appliance presenting aresistive load (1, 8, 12, 19, 40), the power supply having electrical inputmeans for connection to a supply of electrical energy and output meansfor connection to a suitable resistive load; the power supply beingcharacterized in that electronic sWitching means (3, 9, 13, 25, 26) forswitching the electrical power supply to the output means on and off ata switching frequency of at least about 100 Hz is included to therebycreate a series of cycles each having an "on" and an "off' componentwith a duty cycle of from about 3 percent to about 90 percent; thepower supply optionally including one or more inductors (4, 10, 11, 18,23, 24, 37. 38, 39), as may be necessary, to provide, together with theresistive load, a circuit inductance; and wherein the switchingfrequency, duty cycle, and any inductors in the power supply arechosen so as to cooperate with the resistive load to provide a requiredoperation of the resistive load and wherein the circuit includes meansfor ensuring that any back emf or transient energy generated across theinductance is dissipated across the resistive load or is fed back to thepower supply source, or both, during the "off' component of the dutycycle.

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2. A power supply as claimed in claim 1 in which the resistive load has anenhanced efficiency when compared to the efficiency thereof in theabsence of the said power supply.

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3. A power supply as claimed in either one of claims 1 and 2 in which thecircuit includes diode means (28, 29) for ensuring that any back emf ortransient energy generated across the inductance is dissipated acrossthe resistive load or fed back to the power supply source, or both.


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4. A power supply as claimed in anyone of the preceding claims in whichthe resistance, inductance, duty cycle and frequency is chosen toensure operation of the circuit in a state of resonance or a state ofoscillating frequency.

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5. A power supply as claimed in anyone of the preceding claims in whichthe electronic switching means is adapted to effect switching at afrequency of between about 800 Hz and 200,000 Hz.

10 6. A power supply as claimed in anyone of the preceding claims in whichthe duty cycle is from about 5% to about 75%.

7. A power supply as claimed in claim 6 in which the duty cycle is betweenabout 10 and 50%.

158. A power supply as claimed in claim 6 in which the duty cycle is between

about 15 to 40 percent.

9. A power supply as claimed in claim 6 in which the duty cycle is about20 25%.

10. A power supply as claimed in anyone of the preceding claims in whichthe power supply circuit includes electrical energy storage means forreceiving electrical energy associated with any back emf or transient

25 energy generated and for returning it to the circuit.

11 . A power supply as claimed in claim 10 in which the electrical storagemeans is either a battery (7) or a capacitor (6,20,30, 31) in the case ofan alternating current power supply.

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12. A power supply as claimed in anyone of the preceding claims in whichthe resistive load is that of an appliance.


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13. A power supply as claimed in claim 12 in which the power supply is builtinto such appliance.

14. A power supply as claimed in claim 12 in which the power supply is a5 separate unit comprising an electric circuit having an input and an

output for connection between an existing supply of electrical energyand a resistive load circuit and wherein the power supply unit embodieselectronic circuitry adapted to provide an output as defined in anyoneof claims 1 to 11.

1015. An appliance embodying a power supply as defined in claim 12.

16. A method of operating a heat generating resistive load compnsmgapplying, across the resistive load. the output of a power supply as

15 claimed in anyone of claims 1 to 11.

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patent cooperation treaty (pct) published application wo 03 007657 a2

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