GB2421643A - AC-DC converter with improved effciency - Google Patents
AC-DC converter with improved effciency Download PDFInfo
- Publication number
- GB2421643A GB2421643A GB0428052A GB0428052A GB2421643A GB 2421643 A GB2421643 A GB 2421643A GB 0428052 A GB0428052 A GB 0428052A GB 0428052 A GB0428052 A GB 0428052A GB 2421643 A GB2421643 A GB 2421643A
- Authority
- GB
- United Kingdom
- Prior art keywords
- voltage
- diode
- power supply
- inductor
- output
- 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.)
- Granted
Links
Classifications
-
- 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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/06—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode
-
- 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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
-
- 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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/25—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only arranged for operation in series, e.g. for multiplication of voltage
-
- 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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/05—Capacitor coupled rectifiers
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Rectifiers (AREA)
- Dc-Dc Converters (AREA)
- Control Of Eletrric Generators (AREA)
- Supply Devices, Intensifiers, Converters, And Telemotors (AREA)
- Prostheses (AREA)
Abstract
In order to operate a low voltage source from a mains voltage power supply, such as an electricity meter, the alternating current (AC) mains voltage must first be converted to direct current (DC). It is common practice in low cost power supplies to make use of a very simple arrangement of components to reduce the high ac voltage to a lower useable dc voltage, such systems operating in a half wave rectification mode to reduce the circuit component numbers. This makes for inefficient DC voltage supplies. The present invention seeks to address a need to increase an amount of available electrical energy to operate the low voltage circuit requirements of an electricity meter without increasing the energy taken from the mains voltage. The present invention provides a power supply of which both cycles of an input alternating current are employed through the use of an inductor based circuit. During the negative half-cycle, current from Diode D32 flows through inductor L31 which stores the energy, which is released by diode D33 during the positive half-cycle. A switch (Q1, see figure 4) may be used to pulse or chop the current so that a smaller, less costly inductor L31 may be used.
Description
IMPROVEMENTS IN OR RELATING TO POWER SUPPLIES
Ekid of Invention The present invention relates to improvements in or relating to power supplies, and more particularly, although not exclusively, relates to power supplies for utility meters such as power supplies that are commonly used in electricity meters.
ickground to the Invention In order to operate a low voltage electrical component from a mains voltage power supply, such as an electricity meter, the alternating current (AC) mains voltage must first be converted to direct current (DC). It is common practice in low cost power supphes to make : use of a very simple arrangement of components to reduce the high AC voltage to a lower * e 5 useable DC voltage, such systems operating in a half wave rectification mode to reduce the S..
circuit component numbers. *. S * . . * I.
* : ** Fiirc 1 shows a simple circuit wherein a capacitor is selected such that it has an impedance at the AC voltage frequency that can be used to reduce the AC voltage frequency, :20 whereby the effective AC voltage is reduced. Specifically, a first capacitor Cli has a value : chosen such that its impedance at the supply voltage frequency will reduce the supply voltage.
During the positive half cycle of the AC waveform, a first diode Dli conducts and allows current to flow to charge up the first capacitor Cii. A DC voltage is thereby developed across the first capacitor CII, which can be used for a DC load. During the subsequent negative half cycle, a second diode 1)12 conducts and removes the charge from the first capacitor Cli, SO that it can again be used during the next positive half cycle. Whilst this provides the basis for a very simple DC supply, where only a single positive DC voltage rail is provided, it is important to realize that during the negative half cycle, all energy flowing through the second diode D12 is effectively wasted and cannot provide any form of useful ener to enable operation of the electronics of a low voltage circuit. Accordingly, apart from any intrinsic heat wastage through circuit components, there is automatically a sub-50% level of efficiency within the circuitry.
It is possible to make use of the power in the negative half cycle and this is commoniy demonstrated in circuits that have a split' or positive and negative DC power supply rails. Figure 2 shows a simple alternative circuit where two DC voltages are developed; additional to the circuit components of Figure 1, a third capacitor C23 is connected to a second diode D22. During the negative half cycle of the AC supply voltage, the current flow through the second diode D22 removes charge from the third capacitor C23 and causes a negative DC voltage to be developed across the third capacitor, (223. FIowever, if the remainder of the electronic circuitry cannot be configured so that it operates from a spht rail DC supply, then the use of this circuit topology is not appropriate. To address such an 1 0 inherent inefficiency, sunpie full wave rectification circuits have been developed. This can be conventionally accomplished by passing the mains voltage AC input to a full wave bridge rectifier, smoothing the output with, for example, an electrolytic capacitor, and then regulating the output voltage with, for example, a zener diode. Whilst this technique works reasonably well with a filament transformer and the like, it is either highly inefficient or is incapable of : :: J.s providing adequate power for many low power circuits. I. *
Notwithstanding the above, one problem associated with conventional full wave * bridge rectification of incoming alternating current is that considerable amounts of heat can * be generated. This extra heat generated flows to the rest of the circuit through conduction *.20 within components such as the leads thereo and, where space permits, through convection.
Not only does the heat affect other components, it also indicates that the bridge rectifier is wasting energy. Component, life can also be reduced.
Another consideration to be taken into account is the fact that a voltage drop across the diodes of a conventional bridge rectifier also reduces the output voltage available to drive a low voltage circuit such as a utility meter measuring circuit. Utility meter measuring circuits are typically situated within the confines of a small enclosure: wherein excess heat generated by a conventional bridge rectifier circuit can also affect normal operation. Utility meter measuring circuits are rated for operation at a specific ambient temperature and current. If they are operated at higher than their typical temperae, the utthty meter accuracy may be compromised. Furthermore, operating any equipment at other than its rated temperature will have an effect on it is operath-ig longevity.
=bject of the Invention It is therefore an object of the present invention to provide an improved DC low voltage power supply.
It is also an object of the present invention to provide an increased efficiency I)C low Voltage power supply.
In another aspect, the present invention seeks to address a need to increase an amount of available electrical energy to operate low voltage circuit requirements of an electricity meter without increasing the energy taken from the mains voltage.
Statement of Invention
in accordance with a first aspect of the invention, there is provided a power supply circuit for the conversion of mains alternating current voltage received at first and second a...
* , j5 input terminals to provide a direct current voltage at first and second output terminals, the Sf*4 first input terminal havmg a first capacitor coupled in series with a fist diode and connected : thereto by an ouut voltage rail to the first ouut terminal; the second input terminal being * ,: coupled to a common voltage rail, which rail is connected to the second output terminal; wherein an inductor in series with a second diode couples the colmon voltage rail to a node * :20 between the first capacitor and the first diode on the ouut voltage rail and an inductor .: couples with an input of a third diode in series, the third diode being connected to an output of the first diode; and wherein a second capacitor couples the con-u-non voltage line to an output of the third diode; whereby a DC reduced voltage output is provided between the first output terminal and the second output terminal.
A switch can be placed between the inductor and second diode, the switch being operable to pulse the signal through the inductor from the earth voltage line. This switch is conveniently fabricated as a transistor based switch and can receive DC pulses from a signal generator, whereby truncated pulses can be output from the inductor. The switch transistor can be a FET or BJT transistor.
In accordance with a further aspect of the invention, there is provided a method of operating a power supply made in accordance with the invention.
In accordance with a still further aspect of the invention, there is provided a utility meter comprising a power supply made in accordance with the invention.
In accordance with another aspect of the invention there is provided an electricity meter having a power supply, as described above, and wherein the power supply connects directly to metered mains voltage supply.
An advantage arising form the increase in efficiency, as provided by the present invention, is that there is a reduction in the amount of energy taken from the mains AC voltage supply while maintaJng the same low DC voltage supply available for use within the meter. U. **
A further advantage arises from a reduction in the power consumption of the * .: electronic ccuit within the meter is that there is a cumulative environmental impact given
ISSI
*s,5 that, whilst only small savings in the power consumption are made per meter, this could add * * up to a large energy saving when viewed over a large installed population.
IS...' * This invention is particularly advantageous to the manufacture of low cost electricity * meters where the material cost of the power supplies has to be kept to a minimum. *: *
irief Description of the Figures
For a better understanding of the present invention, reference will now be made, by way of example only, to the Figures as shown in the accompanying drawing sheets, wherein: Figure 1 illustrates a first prior art DC voltage supply; Figure 2 Illustrates a second prior art DC voltage supply; Figure 3 illustrates a first power supply, made in accordance with the present invention; Figure 4 represents a second power supply, made in accordance with the present invention; and Figure 5 shows acal values of duty cycle versus AC input voltage obtained for a constant lOmA load DC output.
itailed descnption of the Preferred Embodiments There will now be described, by way of example only, the best mode contemplated by the inventor for carrying out the present invention. In the following description, numerous specific details are set out in order to provide a complete understanding to the present invention. It will be apparent to those skilled in the art, that the present invention may be put into practice with variations of the specific.
With reference to Figure 3, there is shown a first embodni-ient of the invention. In this circuit, a first capacitor C31 is used with a first diode D31 and second capacitor C32 to form a DC voltage supply. Second diode D32 is configured in the circuit so that it will conduct during the negative half-cycle such that the circuit operates in similar fashion to the circuit shown with reference to Figure 1. During the negative halfcycle, current from second diode D32 flows through inductor L31 storing energy, which is released via a third diode 1)33 :15 when second diode D32 is non-conducting in the positive half-cycle of the AC mains supply. I...
* *s* l'he second capacitor C32 is therefore not only charged during the positive half-cycle from *: * first diode Dl but is additionally charged due to energy being released by inductor L3 I via third diode D3.
S..... * .
* . : One constraint imposed by the above circuit is that the inductor L3 I is a relatively *:* : large circuit component in order for the circuit to operate at AC supply frequency (50-60Hz).
Furthermore, the expense of such a component may also be viewed as being disproportionate in relation to the circuit as a whole.
Referring now to Figure 4, a rther embodient of the invention is shown. The size and cost of a conductor can be considerably reduced if the current is pulsed or "chopped".
This may be achieved by a switching device QI which is pulsed from an external source. In this circuit as described above, the first capacitor C41 is used with first diode D41 and second capacitor C42 to form a DC voltage. Second diode D42 is configured in the circuit so that it will conduct during the negative half-cycle as discussed above in relation to the circuit of Figure 1. The switching device, in this case a transistor, QI is arranged such that it conducts in a normal state. The signal source can be either an oscillator or an output port from the microcontroller with appropriate level-shifting.
When the negative half-cycle current from second diode D42 flows through inductor L41 and transistor QI, initially the circuit functions exactly as Figure 1 with the loss of negative half-cycle of the AC supply. However, when high frequency pulses are then applied to the switching device Q1, the switching device turns off and on and consequently "chops" the current flowing through the inductor L41. The stored energy in inductor Ml is thereby released via third diode D43 when transistor QI is in a non-conducting state during the negative half-cycle of the AC mains supply, whereby second capacitor C42 is not only charged during the positive half-cycle of the AC mains supply from first diode D41 but is also additionally charged due to the pulses of energy released by inductor L41 and transistor QI via third diode D43 during the negative AC mains supply cycle.
Chosen values for experimentation, which have been shown to perform well, are as follows: C41 - 33OnF *15 I)42,D421000p1V IA S...
D43 - IOOV l'IV fast switching diode (e.g. BAS16 etc.) *:*. QI - BC846 NPN bipolar Junction transistor L41 - 47mH *.S...
* C42 - 47OF * I)C Pulses- 5 kHz PWM signal ulse-width varies, dependent upon load current).
S * I S * S.
Figure 5 shows the actual values for duty cycle versus the AC input voltage obtained for a constant I O load and 9.2V DC output. Measurements (simulated) have been taken with respect to the standard circuit shown in Figure 1 gave 6mA load current maximum for 23OVAC mput and 3 max for 138VAC input for a IOV DC output for both cases.
Simulation results indicate that for a 138V AC input without the current boost, the power supply will dehver 3mA at I OV DC and when current boost is enabled, it will deliver I OmA at IOV DC. That is to say a three-fold increase in output power can be realised. It will be appreciated that this has a significant impact upon the overall efficiency of the circuit.
Although the specific embodiments above have been described in relation to a power supply for a utility meter, it will be appreciated that the same of circuit is equally applicable to many other low voltage circuits, where the use of electrical cells is inconvenient or that there is a more readily accessible mains electrical supply.
Claims (8)
- CLAIMS: I. A power supply circuit for the conversion of mains alternatingcurrent voltage received at first and second input terminals to provide a direct current voltage at first and second output terminals, the first input terminal (11)1) having a first capacitor (C31) coupled in series with a diode (031) and connected thereto by an output voltage rail to the first output terminal (OPI); the second input terminal (1P2) being coupled to a common voltage rail, which rail is connected to the second output terminal (0P2); wherein an inductor (L31) couples in series with a second diode (D32) the common voltage rail to a node between the first capacitor (C31) and the first diode (D31) on the output voltage rail and inductor the (L31) couples with an input of a thfrd diode (033) in series, the third diode (033) being connected to an output of first diode (D31); and * S. : wherein a second capacitor (C32) couples the comon voltage rail to an output of S...third diode (033); whereby a DC voltage is provided between the first output terminal and the * :*. second output terminal.SI.....*
- 2. A power supply accordmg to clami one, wherein a switch is placed between :o the inductor (L41) and second diode (042), the switch being operable to pulse the signal *. through conductor (L41) from the common voltage rail.
- 3. A power supply according to clami two wherein the switch is a transistor and receives I)C pulses from a signal generator, whereby truncated pulses can be output from the inductor (L41).
- 4. A power supply according to claim three, wherein the switch is a transistor switch selected from a set including BJT and FET transistors.
- 5. A utility meter comprising a power supply according to any one of claims one to four.
- 6. A utility meter, according to claim five, wherein the utility is electricity and the power supply connects directly to metered mains voltage supply.
- 7. A utility meter, according to claim five, wherem the utility is gas and the power supply of the meter connects with a mains supply voltage. a.*ISS * S *5** a. a * . a a a...CLME: SSSSSSS * S
- S. S *SSS 5 S * a S.
Priority Applications (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0428052A GB2421643B8 (en) | 2004-12-22 | 2004-12-22 | Improvements in or relating to power supplies |
| AT05856246T ATE500645T1 (en) | 2004-12-22 | 2005-12-22 | INCREASING THE EFFICIENCY OF AC/DC LOW VOLTAGE SUPPLY THROUGH TOPOLOGICAL MODIFICATIONS |
| DE602005026715T DE602005026715D1 (en) | 2004-12-22 | 2005-12-22 | INCREASING THE EFFICIENCY OF AC / DC LOW VOLTAGE SUPPLIES BY TOPOLOGICAL MODIFICATIONS |
| PCT/IB2005/003873 WO2006070254A2 (en) | 2004-12-22 | 2005-12-22 | Enhancing the efficiency of ac-dc low voltage power supplies by topological modifications |
| BRPI0519433-4A BRPI0519433A2 (en) | 2004-12-22 | 2005-12-22 | improvements in or relating to power supplies |
| EP05856246A EP1836762B1 (en) | 2004-12-22 | 2005-12-22 | Enhancing the efficiency of ac-dc low voltage power supplies by topological modifications |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0428052A GB2421643B8 (en) | 2004-12-22 | 2004-12-22 | Improvements in or relating to power supplies |
Publications (5)
| Publication Number | Publication Date |
|---|---|
| GB0428052D0 GB0428052D0 (en) | 2005-01-26 |
| GB2421643A true GB2421643A (en) | 2006-06-28 |
| GB2421643B GB2421643B (en) | 2008-01-09 |
| GB2421643B8 GB2421643B8 (en) | 2008-11-05 |
| GB2421643A8 GB2421643A8 (en) | 2008-11-05 |
Family
ID=34113027
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0428052A Active GB2421643B8 (en) | 2004-12-22 | 2004-12-22 | Improvements in or relating to power supplies |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP1836762B1 (en) |
| AT (1) | ATE500645T1 (en) |
| BR (1) | BRPI0519433A2 (en) |
| DE (1) | DE602005026715D1 (en) |
| GB (1) | GB2421643B8 (en) |
| WO (1) | WO2006070254A2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2209013A1 (en) * | 2009-01-17 | 2010-07-21 | EMH Elektrizitätszähler GmbH & Co KG | Electronic multi-phase meter |
| GB2531415A (en) * | 2014-08-28 | 2016-04-20 | E I Technology | An alarm device drive circuit |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8711592B2 (en) | 2011-06-21 | 2014-04-29 | Elster Solutions, Llc | Linear transformer power supply |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003164155A (en) * | 2001-11-29 | 2003-06-06 | Kyocera Corp | Rectifier and piezoelectric transconverter |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1599757A (en) * | 1977-02-04 | 1981-10-07 | Tronicair Int Ltd | Voltage converter |
| JPH07327384A (en) * | 1994-05-04 | 1995-12-12 | Emerson Electric Co | Motor,circuit and method for controlling it |
| US6954008B2 (en) * | 2003-05-27 | 2005-10-11 | Zippy Technology Corp. | Integrated power supply apparatus for information appliances |
-
2004
- 2004-12-22 GB GB0428052A patent/GB2421643B8/en active Active
-
2005
- 2005-12-22 AT AT05856246T patent/ATE500645T1/en not_active IP Right Cessation
- 2005-12-22 EP EP05856246A patent/EP1836762B1/en active Active
- 2005-12-22 DE DE602005026715T patent/DE602005026715D1/en active Active
- 2005-12-22 BR BRPI0519433-4A patent/BRPI0519433A2/en not_active IP Right Cessation
- 2005-12-22 WO PCT/IB2005/003873 patent/WO2006070254A2/en active Application Filing
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003164155A (en) * | 2001-11-29 | 2003-06-06 | Kyocera Corp | Rectifier and piezoelectric transconverter |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2209013A1 (en) * | 2009-01-17 | 2010-07-21 | EMH Elektrizitätszähler GmbH & Co KG | Electronic multi-phase meter |
| GB2531415A (en) * | 2014-08-28 | 2016-04-20 | E I Technology | An alarm device drive circuit |
| GB2531415B (en) * | 2014-08-28 | 2021-03-03 | E I Tech Unlimited Company | An alarm device drive circuit |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2421643B (en) | 2008-01-09 |
| GB2421643B8 (en) | 2008-11-05 |
| WO2006070254A3 (en) | 2006-08-31 |
| DE602005026715D1 (en) | 2011-04-14 |
| BRPI0519433A2 (en) | 2009-01-20 |
| GB2421643A8 (en) | 2008-11-05 |
| EP1836762B1 (en) | 2011-03-02 |
| EP1836762A2 (en) | 2007-09-26 |
| WO2006070254A2 (en) | 2006-07-06 |
| ATE500645T1 (en) | 2011-03-15 |
| GB0428052D0 (en) | 2005-01-26 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| S117 | Correction of errors in patents and applications (sect. 117/patents act 1977) | ||
| S117 | Correction of errors in patents and applications (sect. 117/patents act 1977) | ||
| S73 | Revocation on comptroller's initiative (section 73/patents act 1977) |
Free format text: PATENT REVOKED; PATENT REVOKED UNDER SECTION 73(2) ON 21 AUGUST 2012 |