CN103619095A - LED driving circuit - Google Patents
LED driving circuit Download PDFInfo
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- CN103619095A CN103619095A CN201310552365.0A CN201310552365A CN103619095A CN 103619095 A CN103619095 A CN 103619095A CN 201310552365 A CN201310552365 A CN 201310552365A CN 103619095 A CN103619095 A CN 103619095A
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Abstract
The invention provides an LED driving circuit. The LED driving circuit comprises a rectifying circuit, a power supplying circuit, a load driving circuit and a switch circuit. A zero-cross detecting unit of the switch circuit is used for detecting the source electrode voltage of a first power switch pipe to obtain the on-off time and the conduction time of a fly-wheel diode, and then LED constant current driving is achieved. According to the LED driving circuit, a driving power source can be simplified, the size of a PCB of the LED driving power source can be reduced, and the cost of an LED driving power application system is reduced; according to the driving circuit, the zero current time of the fly-wheel diode can be obtained with the only requirement for collecting the source electrode voltage of the first power switch pipe, and the design difficulty, the area and the cost of a chip can be reduced; when the driving circuit is in a BCM, the switch loss can be reduced, the power transfer efficiency is improved, and the EMI can be improved.
Description
Technical field
The present invention relates to electric circuit electronics technical and integrated circuit fields, particularly relate to a kind of for the drive circuit to LED power supply.
Background technology
LED(light-emitting diode) be the luminous semi-conductor electricity sub-element of a kind of energy, LED can only be toward a direction conducting (energising), when electric current flows through, electronics and hole are compound and send monochromatic light within it, this is electroluminescent effect, and the wavelength of light, color are relevant with the element impurity of mixing with its semi-conducting material kind adopting.Have advantages of that efficiency is high, the life-span is long, the conventional light source such as high, the high reliability of cracky, switching speed is not too late.The advantage because of LED with energy-conserving and environment-protective is popularized and is used gradually, and user has proposed more and more higher requirement to its performance simultaneously, and particularly cost control requires more and more stricter.
As shown in Figure 1, traditional LED drive circuit mainly adopts switch flyback switch circuit to control, and electric main becomes direct current through rectification circuit 1, and powers to LED power driving circuit by power supply circuits 2.LED power driving circuit comprises a transformer, and transformer comprises former limit winding NP, secondary winding NS and tri-windings of auxiliary winding NA.After this switching circuit energising, secondary change winding Ns is LED power supply through diode D, and auxiliary winding NA detects the information of sustained diode current over-zero moment point and detection output voltage simultaneously, controls the break-make of transistor M1, makes LED realize constant current and drives.
This switch flyback switch circuit detects the current over-zero moment of diode D by auxiliary winding NA, on its feedback circuit, need to use the components and parts such as rectifier diode, divider resistance, will make like this design of whole Circuits System become complicated, the pcb board volume of LED drive circuit system is increased, will increase the cost of LED electric power system like this, and can cause restriction to its use occasion.
Summary of the invention
The shortcoming of prior art in view of the above, the object of the present invention is to provide a kind of simple in structure, body is less, cost is low LED drive circuit.
For achieving the above object and other relevant objects, the invention provides a kind of LED drive circuit, it comprises: rectification circuit, and described rectification circuit is for becoming direct current by the alternating current of input, power supply circuits, described power supply circuits and the coupling of described rectification circuit, load driving circuits, described load driving circuits and the coupling of described power supply circuits, described power supply circuits are for powering to described load driving circuits, described load driving circuits comprises LED load, inductance element, a fly-wheel diode and an electric capacity, described LED load, inductance element, fly-wheel diode form loop, and described electric capacity is in parallel with described LED load, switching circuit, described switching circuit and the coupling of described load circuit, described switching circuit comprises the first power switch pipe, the second power switch pipe, sampling resistor and a zero cross detection circuit, the drain electrode of described the first power switch pipe and inductance element coupling, the source electrode of described the first power switch pipe is connected with the drain electrode of described the second power switch pipe, the grid of described the first power switch pipe is connected with described power supply circuits, the source electrode of described the second power switch pipe is by sampling resistor ground connection, the output of described zero cross detection circuit is connected with the grid of described the second power switch pipe, when described sampling resistor is greater than defined threshold, described zero cross detection circuit output signal is turn-offed described the second power switch pipe, when the drain voltage of described the second power switch pipe is during lower than defined threshold, described zero cross detection circuit output signal makes described the second power switch pipe open-minded.
Preferably, described zero cross detection circuit comprises zero passage detection unit, switching logic control unit, the input of described zero passage detection unit is connected with the drain electrode of described the second power switch pipe, the output of described zero passage detection unit is connected with the first input end of described switching logic control unit, the second input of described switching logic control unit is connected with the source electrode of described the second power switch pipe, and the output of described switching logic control unit is connected with the grid of described the second power switch pipe.
Preferably, described zero passage detection unit comprises a comparator and a filter delay circuit unit, the negative input of described comparator is connected with the source electrode of described the second power switch pipe, the positive input of described comparator is connected with the source electrode of described the second power switch pipe by described filter delay circuit unit, and the output of described comparator is connected with the first input end of described switching logic control unit.
Preferably, described zero passage detection unit is a trailing edge signal deteching circuit.
Preferably, between described zero passage detection unit and described switching logic control unit, be also provided with one and open short-circuit protection circuit.
Preferably, described inductance element is the secondary winding of a transformer, the former limit winding of described transformer and the coupling of described power supply circuits.
Preferably, described transformer is a flyback transformer.
Preferably, the two ends of the former limit winding of described flyback transformer are connected with for absorbing the leakage inductance reset circuit of peak current.
Preferably, the first power switch pipe is high-voltage circuit breaker pipe, and described the second power switch pipe is middle voltage power switching tube.
As mentioned above, LED drive circuit of the present invention has following beneficial effect: this LED drive circuit can be simplified the design of driving power, dwindles the PCB volume of LED driving power, reduces the cost of LED driving power application system; This drive circuit only need gather the source voltage of the first power switch pipe, can obtain the zero current of fly-wheel diode constantly, and design difficulty that can facilitating chip and saved the area of chip has reduced the cost of chip; While adopting this drive circuit to be in critical conduction mode (BCM), can reduce switching loss simultaneously, improve power supply conversion efficiency, and can improve EMI.
Accompanying drawing explanation
The existing LED drive circuit schematic diagram of Fig. 1.
Fig. 2 is the circuit diagram of first embodiment of the invention.
Fig. 3 is the circuit diagram of the embodiment in embodiment of the present invention zero passage detection unit.
Fig. 4 is voltage or the electric current output waveform schematic diagram of each signaling point in Fig. 3 embodiment.
Fig. 5 is voltage or the electric current output waveform schematic diagram of each signaling point embodiment illustrated in fig. 2.
Fig. 6 is the circuit diagram of second embodiment of the invention.
Fig. 7 is the circuit diagram of third embodiment of the invention.
Embodiment
Below, by specific instantiation explanation embodiments of the present invention, those skilled in the art can understand other advantages of the present invention and effect easily by the disclosed content of this specification.The present invention can also be implemented or be applied by other different embodiment, and the every details in this specification also can be based on different viewpoints and application, carries out various modifications or change not deviating under spirit of the present invention.
Refer to Fig. 2 to Fig. 7, it should be noted that, the diagram providing in the present embodiment only illustrates basic conception of the present invention in a schematic way, satisfy and only show with assembly relevant in the present invention in graphic but not component count, shape and size drafting while implementing according to reality, during its actual enforcement, kenel, quantity and the ratio of each assembly can be a kind of random change, and its assembly layout kenel also may be more complicated.
As shown in Figure 2, be an embodiment of LED drive circuit of the present invention, this LED drive circuit comprises rectification circuit 1, power supply circuits 2, load driving circuits and switching circuit four parts.Rectification circuit 1 and power supply circuits 2 couplings, power supply circuits 2 and load driving circuits coupling, load driving circuits and switching circuit coupling.Rectification circuit 1 is for becoming direct current by civil power alternating current.Power supply circuits 2 comprise the capacitor C 0 connecting between input direct voltage and circuit ground, the resistance R 0 being connected in series and capacitor C 1, and with the voltage-stabiliser tube Dz that capacitor C 1 is connected in parallel, power supply circuits 2 are for powering to load driving circuits and switching circuit.
Load driving circuits comprises LED load 8a, inductance element, a sustained diode 0 and a capacitor C 2, and LED load 8a and inductance element, sustained diode 0 form loop, and capacitor C 2 is in parallel with LED load 8a.As shown in Figure 2, as one embodiment of the present of invention, the inductance element of this load driving circuits is the secondary winding Ns of a transformer 8b, and transformer 8b is flyback transformer, the former limit winding Np of transformer 8b and power supply circuits coupling.
Switching circuit comprises the first power switch pipe M0, the second power switch pipe M1, sampling resistor Rcs and a zero cross detection circuit, the first power switch pipe M0 is high-voltage circuit breaker pipe, the second power switch pipe M1 is middle voltage power switching tube, and the first power switch pipe M0 can bear higher operating voltage.The former limit winding Np of the drain voltage device 8b of the first power switch pipe M0 connects, the source electrode of the first power switch pipe M0 is connected with the drain electrode of the second power switch pipe M1, the grid of the first power switch pipe M0 is connected with power supply circuits, the grid of the first power switch pipe M0 is connected with the negative electrode of voltage-stabiliser tube Dz, and voltage-stabiliser tube Dz provides a constant voltage to make the first power switch pipe M0 always in opening state.The source electrode of the second power switch pipe M1 is by sampling resistor Rcs ground connection, the output of zero cross detection circuit is connected with the grid of the second power switch pipe M1, when sampling resistor Rcs is greater than defined threshold, zero cross detection circuit output signal will make the second power switch pipe M1 turn-off, when the drain voltage of the second power switch pipe M1 is during lower than defined threshold, zero cross detection circuit output signal makes the second power switch pipe M0 open-minded.
As a kind of optimal way, zero cross detection circuit comprises zero passage detection unit 5 and switching logic control unit 6 two parts, the input of zero passage detection unit 5 is connected with the drain electrode of the second power switch pipe M1, the output of zero passage detection unit 5 is connected with the first input end of switching logic control unit 6, the second input of switching logic control unit 6 is connected with the source electrode of the second power switch pipe M1, and the output of switching logic control unit 6 is connected with the grid of the second power switch pipe M1.When the drain voltage saltus step of the second power switch pipe M1 is during lower than defined threshold, high level will be exported to switching logic control unit 6 in zero passage detection unit 5, switching logic control unit 6 output high level make the second power switch pipe M1 open-minded, and the voltage of working as on sampling resistor Rcs rises, when this voltage reaches the threshold values of switch control logic unit 6 inner settings, switch control logic unit 6 output low level signals, turn-off power switch MOS transistor M0.
As a kind of optimal way, between zero passage detection unit 5 and switching logic control unit 6, be also provided with one and open short-circuit protection circuit 3, this is opened short-circuit protection circuit 3 and comprises overvoltage crowbar and short-circuit protection circuit two parts.The zero passage detection unit 5 that the input of described overvoltage crowbar connects, output is connected to switch control logic unit 6, and zero passage detection unit 5 detects the zero crossing moment of sustained diode 0, obtains thus the inductance element erasing time; When this erasing time is less than default time of overvoltage crowbar, over-voltage protecting function is triggered, and closes the second power switch pipe M1.The zero passage detection unit 5 that the input of short-circuit protection circuit connects; output is connected to switch control logic unit 6; when the inductance element erasing time is greater than default time of described short-circuit protection circuit, short-circuit protection function is triggered, and closes the second power switch pipe M1.
As a kind of optimal way, as shown in Figure 3, zero passage detection unit comprises a comparator and a filter delay circuit unit, the negative input of comparator is connected with the source electrode of the second power switch pipe M1, the positive input of comparator is connected with the source electrode of the second power switch pipe M1 by filter delay circuit unit, and the output of comparator is connected with the first input end of switching logic control unit.When work as shown in Figure 4, VD is the input waveform of zero passage detection unit to this circuit; VE is the waveform after filtering delay-time; At Ta constantly, when VE magnitude of voltage reaches Δ V over VD magnitude of voltage, comparator is exported by low transition to high level (as shown in Vzcd).
For the higher-order of oscillation false triggering zero passage detection that prevents from causing because of leakage inductance, can also be used for preventing leakage inductance to the envelope shaping of the first power switch pipe M0 source class voltage.Envelope shaping module adopts peak envelop detection, and time constant is chosen and is greater than the higher-order of oscillation cycle that leakage inductance is introduced, and prevents false triggering zero passage detection, simultaneously also as far as possible little, avoids introducing too much delay time error and causes zero passage detection constantly too much to postpone.By the further filtering wave by prolonging time of the envelope signal after shaping, as a dynamic benchmark with the comparison of former shaping envelope voltage, time constant is chosen and should be sufficiently more than the time constant that envelope detection circuit is introduced, be less than switch power supply power tube switch periods, so that can accumulated error during next switch simultaneously.Shaping envelope voltage and filtering delay-time signal as a comparison two inputs of device compare, and compare result signal is by low transition to high level, and the zero current moment of sustained diode 0 can be thought in hopping edge.
This zero passage detection unit can also be realized by trailing edge signal deteching circuit; Or by the anti-phase generation rising edge signal of trailing edge signal process, then realized by rising edge signal deteching circuit.
Operation principle of the present invention is, when zero passage detecting unit 5 detects the first power switch pipe M0 source voltage envelope by high level saltus step during to low level, this zero passage detection unit output is high level by low transition, obtains the current over-zero of sustained diode 0 constantly; The input of high level connecting valve control logic unit 6 is exported in this zero passage detection unit 5 simultaneously, as the signal of opening of the second power switch pipe M1.After the second power switch pipe M1 conducting, transformer primary side Current rise, voltage on sampling resistor Rcs also rises, and when reaching the default threshold voltage in switch control logic unit 6, switch control logic unit 6 output low level signals turn-off the second power switch pipe M1.In the present invention, by 5 pairs of zero passage detection unit the first power switch pipe M0 source voltage, detected, obtain the shutoff moment and the ON time of sustained diode 0, thereby realize LED constant current, drive.
The course of work below in conjunction with Fig. 2,5 pairs of first embodiment of the invention is described:
The grid voltage waveform of the second power switch pipe M1 is as described in GD in Fig. 5.At T0 constantly, the second power switch pipe M1 conducting, transformer 8b primary current (as shown in Ip in Fig. 5) rises, voltage on sampling resistor Rcs boosts on also, when this voltage reaches the threshold values of switch control logic unit 6 inner settings (in Fig. 5, T1 constantly), switch control logic unit 6 output low level signals, turn-off the second power switch pipe M1; Meanwhile, transformer 8b sustained diode 0 starts conducting, and electric current is as shown in Is in Fig. 5, because transformer 8b is flyback transformer.At the second power switch pipe M1, turn-off T1 constantly, the second power switch pipe M1 drain voltage rises rapidly, as shown in DRAIN in Fig. 5.This voltage obtains voltage signal as shown in VD in Fig. 5 through being capacitively coupled to the SOURCE end of the second power switch pipe M1.At T2 constantly, the secondary winding degaussing of transformer 8b finishes, and sustained diode 0 electric current drops to zero, and the secondary winding voltage of transformer 8b starts rapid decline.Due to the coupling of transformer 8b former limit winding and secondary winding, therefore the drain voltage of the second power switch pipe M1 also starts rapid decline, through the voltage VD of electric capacity the second power switch pipe M1 source electrode, also starts rapid decline.To the T3 moment, VD voltage will be lower than filtering delay-time signal voltage, zero-crossing comparator output by low level signal saltus step to high level signal in Fig. 5 as shown in VZCD, be now the zero passage moment of sustained diode 0, switch control logic unit 6 output high level signals are by the conducting again of power switch MOS transistor.Primary current at T1 constantly, reaches maximum Ipk; T0 to T1 is the ON time of the second power switch pipe M1 constantly, at T1 to T2, is the secondary winding degaussing time in the time.At T2 to T3, be resonance time in the time, its value is far smaller than the degaussing time.
In the present embodiment, at winding two ends, the former limit of flyback transformer 8b, connect leakage inductance reset circuit 4, be used for the peak current of absorbed power switch mos transistor M0 shutdown moment, this leakage inductance reset circuit 4 can consist of diode, resistance, electric capacity or voltage-stabiliser tube.It is pointed out that the second power switch pipe M1 source voltage is the alternating current component part of the first power switch pipe M0 drain voltage due to the effect of the isolated DC coupling interchange of electric capacity, and this alternating current component and winding voltage are linearly proportional.Therefore the second power switch pipe M1, in the valley voltage vicinity conducting of drain electrode, is conducive to reduce the switching loss of the second power switch pipe M1, improves drive circuit power supply conversion efficiency, improves EMI.
Compared with prior art, present embodiment is carried out single-ended detection by single-ended zero current detection unit to the source voltage hopping edge of the first power switch pipe M0, according to comparative result, obtain the circuit zero passage moment of sustained diode 0, thereby determine the degaussing time of winding, the average current of LED load detected, realize LED constant current and drive.Without auxiliary winding, also without the design of extra low-voltage power switch MOS transistor and high-voltage capacitance, can simplify the design of LED driving power, dwindled the size of PCB circuit board in application system, reduced LED driving power cost.
As shown in Figure 6,7, for the other two kinds of execution modes of the present invention relate to a kind of buck-boost type LED driving power circuit.Be with the main distinction of the first execution mode: in the first execution mode, the connected mode of LED load 8a and switching circuit and control method is isolated; And in latter two execution mode of the present invention, the connected mode of LED load 8a and switching circuit and control method is non-isolation.
Fig. 6 is the switching circuit and the control method schematic diagram that detect based on single-ended edge of the second execution mode of the present invention; rectification circuit 1; power supply circuits 2; open short-circuit protection circuit 3; single-ended zero current detection unit 5; switch control logic unit 6 is identical with the first execution mode with power switch MOS transistor M0, and its course of work is also identical, does not repeat them here.Difference is: in the first execution mode, the switching circuit detecting based on single-ended edge and control method are connected with LED load 8a by magnetic couplings element transformer, realizes isolation in electrical characteristic; And in the second execution mode of the present invention, the magnetic element inductance L 1 of LED load 8a and switching circuit and control method is connected in parallel.
Fig. 7 is the switching circuit and the control method schematic diagram that detect based on single-ended edge of the third execution mode of the present invention.The third execution mode of the present invention relates to a kind of voltage-dropping type LED driving power circuit.With the second execution mode of the present invention the same, the connected mode of LED load 8a and switching circuit and control method is also non-isolation, and its course of work is also identical.Difference is: in second embodiment of the invention, the magnetic element inductance L 1 of LED load 8a and switching circuit and control method is connected in parallel; And in the third execution mode of the present invention, the magnetic element inductance L 1 of LED load 8a and switching circuit and control method is connected in series.
LED drive circuit of the present invention has following beneficial effect: this LED drive circuit can be simplified the design of driving power, dwindles the PCB volume of LED driving power, reduces the cost of LED driving power application system; This drive circuit only need gather the source voltage of the first power switch pipe, can obtain the zero current of fly-wheel diode constantly, and design difficulty that can facilitating chip and saved the area of chip has reduced the cost of chip; While adopting this drive circuit to be in critical conduction mode (BCM), can reduce switching loss simultaneously, improve power supply conversion efficiency, and can improve EMI.So the present invention has effectively overcome various shortcoming of the prior art and tool high industrial utilization.
Above-described embodiment is illustrative principle of the present invention and effect thereof only, but not for limiting the present invention.Any person skilled in the art scholar all can, under spirit of the present invention and category, modify or change above-described embodiment.Therefore, such as in affiliated technical field, have and conventionally know that the knowledgeable, not departing from all equivalence modifications that complete under disclosed spirit and technological thought or changing, must be contained by claim of the present invention.
Claims (9)
1. a LED drive circuit, is characterized in that, it comprises:
Rectification circuit (1), described rectification circuit (1) is for becoming direct current by the alternating current of input;
Power supply circuits (2), described power supply circuits (2) and described rectification circuit (1) coupling;
Load driving circuits, described load driving circuits and described power supply circuits (2) coupling, described power supply circuits are for powering to described load driving circuits, described load driving circuits comprises LED load (8a), inductance element, a fly-wheel diode (D0) and an electric capacity (C2), described LED load (8a), inductance element, fly-wheel diode (D0) form loop, and described electric capacity (C2) is in parallel with described LED load (8a);
Switching circuit, described switching circuit and described load circuit (2) coupling, described switching circuit comprises the first power switch pipe (M0), the second power switch pipe (M1), sampling resistor (RES) and a zero cross detection circuit, the drain electrode of described the first power switch pipe (M0) and inductance element coupling, the source electrode of described the first power switch pipe (M0) is connected with the drain electrode of described the second power switch pipe (M1), the grid of described the first power switch pipe (M0) is connected with described power supply circuits (2), the source electrode of described the second power switch pipe (M1) is by sampling resistor (RES) ground connection, the output of described zero cross detection circuit is connected with the grid of described the second power switch pipe (M1), when described sampling resistor (RES) is greater than defined threshold, described zero cross detection circuit output signal is turn-offed described the second power switch pipe (M1), when the drain voltage of described the second power switch pipe (M1) is during lower than defined threshold, described zero cross detection circuit output signal makes described the second power switch pipe (M1) open-minded.
2. LED drive circuit according to claim 1, it is characterized in that: described zero cross detection circuit comprises zero passage detection unit, switching logic control unit, the input of described zero passage detection unit is connected with the drain electrode of described the second power switch pipe (M1), the output of described zero passage detection unit is connected with the first input end of described switching logic control unit, the second input of described switching logic control unit is connected with the source electrode of described the second power switch pipe (M1), the output of described switching logic control unit is connected with the grid of described the second power switch pipe (M1).
3. LED drive circuit according to claim 2, it is characterized in that: described zero passage detection unit comprises a comparator and a filter delay circuit unit, the negative input of described comparator is connected with the source electrode of described the second power switch pipe (M1), the positive input of described comparator is connected with the source electrode of described the second power switch pipe (M1) by described filter delay circuit unit, and the output of described comparator is connected with the first input end of described switching logic control unit.
4. LED drive circuit according to claim 2, is characterized in that: described zero passage detection unit is a trailing edge signal deteching circuit.
5. LED drive circuit according to claim 2, is characterized in that: between described zero passage detection unit and described switching logic control unit, be also provided with one and open short-circuit protection circuit (3).
6. LED drive circuit according to claim 1, is characterized in that: described inductance element is the secondary winding of a transformer, the former limit winding of described transformer and the coupling of described power supply circuits.
7. LED drive circuit according to claim 6, is characterized in that: described transformer is a flyback transformer.
8. LED drive circuit according to claim 7, is characterized in that: the two ends of the former limit winding of described flyback transformer are connected with for absorbing the leakage inductance reset circuit of peak current.
9. LED drive circuit according to claim 7, is characterized in that: the first power switch pipe (M0) is high-voltage circuit breaker pipe, and described the second power switch pipe (M1) is middle voltage power switching tube.
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| CN104022651B (en) * | 2014-05-20 | 2017-02-15 | 重庆大学 | Critical conduction mode control circuit |
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| CN106100337B (en) * | 2016-01-31 | 2019-07-05 | 深圳麦格米特电气股份有限公司 | A kind of control method of flyback high pressure generator pulse width |
| CN106100337A (en) * | 2016-01-31 | 2016-11-09 | 深圳麦格米特电气股份有限公司 | A kind of control method of flyback high tension generator pulse width |
| CN107124787A (en) * | 2017-04-07 | 2017-09-01 | 广州市河东智能科技有限公司 | A kind of control device and method of capacitive light fixture |
| CN112449466A (en) * | 2019-09-04 | 2021-03-05 | 华润微集成电路(无锡)有限公司 | Linear LED drive circuit, power switch detection method and dimming control method |
| CN112449466B (en) * | 2019-09-04 | 2023-12-15 | 华润微集成电路(无锡)有限公司 | Linear LED driving circuit, power switch detection method and dimming control method |
| CN113873719A (en) * | 2021-11-30 | 2021-12-31 | 深圳赫飞物联科技有限公司 | Dimming control circuit |
| CN113873719B (en) * | 2021-11-30 | 2022-03-08 | 深圳赫飞物联科技有限公司 | Dimming control circuit |
| CN116032708A (en) * | 2023-02-06 | 2023-04-28 | 浙江正泰电器股份有限公司 | Characteristic current identification method and device, electronic equipment and storage medium |
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Application publication date: 20140305 |