EP2512682A1

EP2512682A1 - Bipolar air ionization method and corresponding air bipolar ionization circuit

Info

Publication number: EP2512682A1
Application number: EP09807462A
Authority: EP
Inventors: Domenico Toneatto; Cataldo Volo; Gianmarco Malcotti
Original assignee: Periso SA
Current assignee: Periso SA
Priority date: 2009-12-17
Filing date: 2009-12-17
Publication date: 2012-10-24
Also published as: RU2514074C2; JP2013514619A; RU2012126615A; WO2011073732A1

Abstract

The invention refers to a method and a circuit in which the ionisation of the air is controlled to limit the generation of positive ions, obtaining a predetermined proportion between positive and negative ions. More specifically, the method comprises an attenuation or reduction of the positive component of an ionisation voltage, to obtain the limitation of the generation of positive ions.

Description

Bipolar air ionization method and corresponding air bipolar ionization circuit

DESCRIPTION

Field of application

The present invention refers to a bipolar ionisation method and a respective bipolar ionisation circuit of the air.

Prior art

As known, the quality of air, especially in closed environments with little circulation of air, tends to degrade due to the accumulation of particulate such as smoke, bacteria, gas, pollen and other volatile organic compounds emitted by household appliances or office equipment, such as printers, photocopiers, food storage apparatuses, etc. Such substances make the environment less pleasant, not only due to the smell associated with them but also due to a proven harmful effect on man.

Devices and methods for purifying air are known that consist of holding the aforementioned substances in a particulate filter.

However, such devices and methods suffer from the substantial drawbacks of undergoing progressive and rapid deterioration of the air purification capability, which goes down as impurities accumulate in the filters, as well as of being substantially unable to hold small- sized particulate.

There are also known air ionisation devices and techniques that instead of holding the particulate transform it into elements that are not harmful to man, in particular by sending the particulate to undergo aggregations into non-polluting molecules. Such devices are preferred to the filters quoted above since they also act upon small-sized particulate and they last for a substantially unlimited amount of time, since they do hot use filters that are subject to deterioration. Moreover, they only require ordinary maintenance foreseen every 10000 hours of uninterrupted operation,

Indeed, ionisation methods consist of electrically exciting atoms or molecules present in the air to the point of causing electrons to detach from the respective atomic orbits; the atoms with an electron removed, commonly known as cations or positive ions, are positively charged. Moreover, the freed electrons collide with other atoms or molecules present in the air, negatively charging them and forming so-called anions or negative ions.

The ionisation is thus based on the transformation of atoms or molecules of particulate into respective anions or cations that are not harmful to man. Indeed, the atoms from which electrons are subtracted are unstable and seek an equilibrium that generates new collisions and aggregations.

However, many environments are already rich in positive ions, for example produced by office equipment such as monitors or printers or by commonly used household appliances, and a further introduction of cations and anions through ionisation, although on the one hand has the beneficial effect of introducing negative ions, on the other hand has the disadvantage of further increasing the number of positive ions, and has an undesired and harmful effect on man which can, for example, manifest itself with symptoms of depression, anxiety or headache.

The problem forming the basis of the present invention is to provide a method and device that are able to ionise air without excessively increasing the concentration of positive ions or of negative ions, substantially overcoming the limitations and disadvantages that ionisation systems and methods according to the prior art still suffer from.

Summary of the invention

The idea of solution at the basis of the present invention is to device a bipolar ionising circuit and a relative method that produce positive ions and negative ions in a predetermined proportion, on the one hand allowing the particulate present in an environment to be transformed into substances not harmful to man, in the form of positive ions and negative ions, and on the other hand allowing a more human-friendly concentration of positive ions and negative ions to be established.

In particular, the applicant has found that in known ionisation processes, the concentration of positive ions present in the ionised environment is substantially greater than the concentration of negative ions, also due to the fact that the average lifetime of positive ions is longer and can reach a few minutes, compared to an average lifetime of a few seconds for negative ions. Therefore, according to an aspect of the invention, the ionisation of air is controlled to generate a limited amount of positive ions with respect to negative ions; the predetermined proportion is able to balance the concentration of positive and negative ions in the environment, not only compensating the longer lifetime of the negative ions but also their introduction into the environment by office equipment such as printers, fax machines, etc.

The ionisation is obtained by passing a flow of air through an electric field of suitable intensity. The flow of air licks at least one ioniser that produces the electric field and causes the ionisation of the air. The electrically neutral molecules of air are split into two or more parts (ions) with positive or negative electrical charges. The disassociation takes place by addition of energy. Preferably, according to the invention, the ionisation is caused through the generation of a suitable electric field.

According to the idea for a solution outlined above, the technical problem is solved by a method in which the ionisation of air is controlled to limit the generation of positive ions, obtaining a predetermined proportion between positive and negative ions.

According to a first aspect of the method of the present invention, the method comprises an attenuation or reduction of the positive component of an ionisation voltage, to obtain the aforementioned limitation of the generation of positive ions.

In particular, the method comprises the steps of feeding an ionisation circuit with a voltage, raising such a voltage and reducing predetermined positive values of the voltage to obtain less production of positive ions.

In an embodiment of such a method, the voltage is associated with a positive half-wave with alternating voltage values with respect to time, which is reduced so that the RMS value associated with it develops a lower power than the RMS value associated with a negative half-wave of the voltage value. In particular, the positive half- wave has the same amplitude as the negative half-wave but a lower height.

In another embodiment of the method, the voltage is associated with a positive half-wave of alternating voltage values having a lower amplitude and height than a negative half- wave of voltage values; also in this case, the RMS value associated with the positive half-wave develops a lower power than the RMS value associated with the negative half-wave of the aforementioned voltage value. Consequently, the energy transferred by the positive part of the voltage is less than the energy transferred by the negative part of the voltage. In particular, the voltage can be symmetrical or asymmetrical with respect to zero and have different waveforms; preferably, the voltage has a substantially sinusoidal trend.

In a particular one of the aforementioned embodiments, the positive voltage value is rectified, through a first circuit portion, in a first direct voltage value, lower than a module of a direct voltage value at which a negative voltage value is rectified, through a second circuit portion. Said first and second circuit portions comprise passive elements arranged upstream of at least one positive and negative electrode for emitting respective positive and negative ions.

According to the aforementioned aspect of the present invention, the attenuation of the RMS value of the positive half-waves can be obtained for example in one of the following ways. In a first way, the function V(t) of the voltage with respect to time is asymmetrical with respect to zero, i.e. the peak values of the positive half-waves are lower (in absolute value) than the peak values of the negative half-waves. For example, the function V(t) is substantially an sinusoidal-shape displaced with respect to the line of the zero and towards the negative values. In a second way, a voltage V(t) symmetrical with respect to zero undergoes an attenuation of the positive half-waves, with a levelling of the positive peak values. It is possible to reduce the RMS value of the positive voltages through the attenuation of the positive half-waves of the voltage signal. The attenuation can be obtained for example with the aforementioned passive components, for example one or more resistances and one or more diodes. As stated, the ionisation of the air is induced through the generation of an electric field. In particular, again according to this aspect of the invention, the electric field has a substantially alternating trend over time, wherein the RMS voltage value of the positive half-wave is lower than the RMS voltage value of the negative half- wave. In this way the production of positive ions is limited, obtaining the aforementioned balancing effect between positive and negative ions. Indeed, the applicant has observed a correlation between a generation of positive ions and the positive voltage values and that by reducing the positive voltage values it is possible to reduce the production of positive ions.

According to another aspect of the method of the present invention, the limitation of the production of positive ions is obtained by feeding an ionisation unit with a high voltage gate transformer having a primary winding connected to a feeding circuit of the impulse type, and a secondary winding connected to at least one electrode of an ionisation device. In this case, there is a switch for the feeding of the transformer whose opening corresponds to the generation of a leading edge of a voltage curve that determines the passage of energy from the secondary of the transformer to the ionising device 24, and therefore the actual ionisation process with limited production of positive ions.

According to the idea of solution at the basis of the present invention, the technical problem is also solved by an ionisation circuit in which the ionisation of the air is controlled to limit the generation of positive ions, obtaining a predetermined proportion between positive and negative ions.

According to an aspect of the invention, the circuit comprising a power supply and a filter for the reduction of predetermined values of the voltage of the current, corresponding to the production of positive ions.

The ionisation circuit can be integrated in a device comprising an ionisation unit with needles or with a tube.

In particular, the filter for the reduction of the positive values of the voltage can be made through known circuit elements, such as voltage reducers and passive components like resistances. Further characteristics of the circuit and of the filter will be given in the following description, both with reference to an ionisation unit with needles and to one with a tube.

Preferably, according to this aspect of the invention, the filter is adjustable to reduce the positive value of the voltage of the current progressively and obtain a proportional reduction of the production of positive ions. Advantageously, the adjustable filter allows the proportion to be modified from the preferred value of 1:4, for example, to the value of 1:3, i.e. about 3/9 positive ions and 6/9 negative ions, which is pleasant in environments in which the concentration of negative ions is already per se low.

According to another aspect of the invention, the ionisation circuit carries out the limitation of the production of ions through a particular connection between an electrical power supply of an ionisation unit, carried out between a high voltage gate transformer having a primary winding connected to a feeding circuit of the impulse type, and a secondary winding connected to at least one electrode of an ionisation unit. Preferably, the primary winding of the transformer is connected to earth by means of at least one electronic switch, for example MOS-FET. In this way the closing of said switch induces current in the primary winding of the transformer, and the opening of the switch causes an impulse of current in the secondary winding and energy transfer to the ionisation unit. The switch can be controlled with a square wave signal provided by an oscillator.

The opening of the switch in greater detail is the equivalent to the transfer of one impulse of current, and thus of energy, to the secondary winding of the transformer and with it to the ionisation device. The ionisation process takes place substantially during the leading edge of said impulse. According to one of the aspects of the invention, the opening and closing frequency of the switch is such that the time period between two impulses is substantially the equivalent to the time period necessary for transferring to the secondary winding the energy obtained from the passage of current in the primary during the closing time of the switch. The applicant has found that, in this way, the production of ions is mainly negative and the desired controlled bipolar ionisation effect is obtained. Without limiting the scope of protection of the invention, the predetermined proportion between the positive and negative ions made through the method and the circuit quoted above is roughly 1:4, i.e. 2/ 10 of positive ions and 8/ 10 of negative ions. Such a proportion can be adjusted, for example in the proportion of 1/ 10 positive ions and 9/ 10 negative ions that is preferred in some therapeutic environments.

Further technical characteristics and advantages of the ionisation circuit and of the relative ionisation method according to the present invention shall become clear from an embodiment thereof, given as an example and not for limiting purposes with reference to the attached drawings.

Brief description of the drawings

Fig. la represents an ionisation circuit according to the present invention;

Fig. lb is a graph of the voltage of the current according to the time, in input to the circuit of figure la;

Fig. lc is a graph of the voltage of the current according to the time, in input to an ionising element with needles of figure la;

Fig. 2a represents a variant embodiment of the ionisation circuit according to the present invention;

Fig. 2b is a graph of the voltage of the current according to the time, in input to the circuit of figure 2 a;

Fig. 2c is a graph of the voltage of the current according to the time, in input to an ionisation element with a tube of figure 2a;

Fig. 2d represents the voltage of the current of figure 2a, according to a different graph;

Fig. 3a represents another embodiment of the ionisation circuit according to the present invention;

Fig. 3b is a graph of the voltage of the current according to the time, in input to the circuit of figure 3a; Fig. 3c is a graph of the voltage of the current according to the time, in input to an ionisation element with a tube of figure 3a;

Detailed description

With reference to Fig. la an ionisation circuit 1 according to the present invention comprising a first electrode 3c for the emission of positive ions and a second electrode 4c for the emission of negative ions is schematically represented. Preferably, the first and second electrode are incorporated in an ionisation unit 5 with needles configured to receive a voltage of the current.

In the circuit 1, an alternating voltage power supply 2, for example at 220 VAC with frequency 50 Hz, is connected to an HVG transformer that raises the voltage of said current. Preferably, the HVG transformer is made from ferrite, which raises the alternating voltage of the current at its input, for example from 220 V at 50 Hz, to a voltage of about 800 V. In particular, an output from the HVG transformer is connected to a variable resistance 6 in turn connected between a first resistance 7, through which the first electrode 3 is fed, and a second variable resistance 8 through which the second electrode 4 is fed. Through the adjustment of the variable resistances 6 and 8 it is possible to obtain the positive value of the voltage, and thus adjust the proportion of positive ions and negative ions, limiting the production of positive ions.

The first and the second electrode 3c, 4c are connected downstream of passive elements comprising a respective plurality of condensers 3a, 3b and diodes 4a, 4b connected in cascade to further raise the voltage of the current and to rectify it into a respective direct voltage, through which to emit the positive and negative ions. For example, the condensers 3a and diodes 3b of the first electrode 3c are configured to supply in output a voltage of 4500 VDC and the condensers 4a and the diodes 4b of the second electrode to supply a voltage of 5000 VDC, corresponding to a greater production of negative ions. Preferably, the ionisation unit has tungsten needles.

Figure lb schematically represents the trend of the alternating voltage in output from the HVG transformer and figure lc represents the trend of the positive and direct voltage 9a and of the negative and direct voltage 9b in output, respectively, from the condensers and diodes 3a, 3b and from the condensers and diodes 4a, 4b, where the negative voltage has a higher module than the positive voltage.

It is worth describing the structure of the circuit of figure la in greater detail. The ioniser with needles 5 comprises an electrode or needle, or else a respective plurality of needles, connected to a positive pole 3c, and correspondingly one or more needles connected to a negative pole 4c. A supply voltage of 220 VAC or else directly of 12 VDC is raised in a first HVG transformer and than is raised further and rectified with a series of condensers and diodes 3a, 3b, 4a, 4b, obtaining a direct output signal (DC). Suitable trimmers 6-8 adjust the signal in output available at the poles 3c and 4c, attenuating the level of the positive voltage at the pole 3c. For example, a signal in input like in Fig. lb provides a signal in output of 4.5 kV DC of positive voltage 9a and 5 kV DC of negative voltage 9b.

With reference to the above embodiment, the electric field that is established, during operation, between the needles connected to the poles 3c and 3d, ionises the flow of air, releasing a substantial amount of ions.

The present invention also refers to a bipolar ionisation method of air, able to be applied to the circuit described above or to its variant embodiments, for example based on ionisation units with a tube, some examples of which shall be given in the following description.

The method foresees controlling the ionisation of air to limit the generation of positive ions, obtaining a predetermined proportion between positive and negative ions. In particular, the method attenuates and reduces the positive component of the ionisation voltage, to obtain the limitation of the generation of positive ions. The air is ionised with at least one ionisation unit that comprises two electrodes separated by a body of dielectric material, in which one of the two electrodes is connected to earth and the other electrode is fed with a voltage V(t) having an alternating trend over time with respect to a zero voltage. The RMS value Veff,- associated with the negative half-waves of the voltage V(t) is greater than the RMS value Veff,+ associated with the positive half- waves. With reference to figure 2 a, an ionisation circuit 10 according to a variant embodiment of the present invention is schematically represented, comprising an inner electrode 11 and an outer electrode 12, preferably integrated in an ionisation unit 14 and separated by a body 13 of said unit 14 made from dielectric material; one of the electrodes 11 is connected to earth and the other electrode 12 is fed with a voltage having a substantially sinusoidal trend over time. Preferably, the ionisation unit 14 is of the tube type, comprising a dielectric tube and two electrodes respectively inside and outside of the tube; for example, the outer electrode 12 is earthed and the inner electrode 11 is connected to a secondary winding of a HVG transformer. Preferably, the transformer has a primary winding of 230 VAC at 50 Hz and a secondary one at 2.7 kV. The applicant has observed that a transformer with a ferrite core and an ionisation unit with a quartz tube make it possible to make a proportion of positive and negative ions with high precision.

The circuit 10, essentially, comprises a high voltage gate transformer, with primary winding fed with an alternating voltage, and secondary connected to one of the electrodes, for example the inner electrode of the ioniser with a tube. The electrodes 11 and 12 are configured to receive a first component of the current having positive voltage values and a second component having negative voltage values. A series of resistances 15, 16, 17 are configured to reduce predetermined values of the first component with respect to the second and obtain a predetermined proportion between positive and negative ions emitted by

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The circuit 10 is controlled through the bipolar ionisation method according to the present invention and in particular, the voltage V to supply voltage to the inner electrode 11 of the ionisation unit is taken from the high voltage gate transformer and reduced, through a voltage filter comprising the resistors 15-17, in predetermined values corresponding to the production of positive ions, in a different proportion with respect to the negative ions. The resistances 15, 16 are used in series to reduce the current to less than 20 mA. Preferably, such resistances have a very high value, for example over 10ΜΩ. Such a condition makes it possible to level a positive half-wave associated with the positive voltage values leaving a corresponding negative half-wave, associated with the negative voltage values, unchanged. As the resistance 17 varies it is possible to modify the threshold cut-off value of the positive half-wave.

Preferably, the filter made through the resistors and diodes 15-19 is adjustable to progressively reduce the positive value of the voltage of the current and obtain a proportional reduction of the production of positive ions. Advantageously, the adjustable filter makes it possible to modify the proportion -for example - from the preferred value of 1 :4 to the value of 1 :3, i.e. about 3/9 positive ions and 6/9 negative ions, which is pleasant in environments in which the concentration of negative ions is already per se low.

Figure 2 b schematically shows the trend over time t of the voltage V in output from the high voltage gate transformer. Preferably, such a voltage is of the order of 2.7 kV. Figure 2c, on the other hand, schematically represents the voltage in input to the ionisation unit 14, downstream of the voltage boost applied by the HVG transformer and of the reduction of the positive values carried out through the components 15-17 and 19. In particular, the predetermined reduced voltage values limit a production of positive ions, obtaining a greater proportion of negative ions with respect to the positive ions.

With reference to figure 2d, the predetermined voltage values V(t), tl<t<t2, found in a predetermined upper portion SI' of a positive half- wave S 1 of the voltage V with respect to the time t, corresponding to the production of positive ions, are schematically represented.

The step of reducing the predetermined voltage values modifies the positive half- wave S I so that the RMS value Veff+ associated with it develops a lower power than a RMS value Veff- associated with a negative half-wave S2 of aforementioned voltage values V(t). Such a difference is due to the fact that the negative voltage values of the alternating current are not reduced.

In other words, again with reference to figure 2d, the voltage values according to the method of the present invention are never within the upper portion SI' outlined by the half- wave S, which assumes a substantially half- square shape.

It is worth noting the structural composition of the circuit of figure 2a. The ionising unit 14 structurally comprises a tube of insulating material, an- inner plate 11 and an outer mesh 12. The voltage is supplied by a high voltage gate HVG transformer, in which the primary HVG2 receives an alternating sinusoidal voltage V4,in as in Fig. 2b, and the secondary HVG1 provides a voltage V4,out with levelling of the positive peaks (Fig. 2d) obtained through resistances 15-17 and diode 19. Through the effect of said passive components 15-17, 19, the positive half- wave is levelled at a maximum value V* below the peak voltage value V+ of the sinusoid. The peak area indicated with a broken line in Fig. 2c is "cut" by the signal and, consequently, the RMS voltage value of the positive half-wave is less than the RMS voltage value of the negative half-wave. For example, the input signal of Fig. 3b is at 220 VAC and the signal of Fig. 3c reaches 2.7 kVAC.

It should be understood that in the embodiment of Fig. 2d, the energy transferred from the positive half-wave is less than that transferred from the negative half- wave.

The ionisation circuits of figures la and 2a are, on the other hand, controlled by the method of the invention, in which the ionisation of the air is induced through the generation of an electric field having a substantially alternating trend over time with a positive voltage peak V+ and a negative voltage peak V-, and the positive half- wave of the electric field is levelled so that the module of the RMS voltage value Veff+ of the positive half-wave is less than the RMS voltage value Veff- of the negative half- wave.

In particular, the voltage of the electric field that causes the ionisation of the air has a nominal value of between 2 and 5 kV and more preferably between 2 and 3 kV. The electric field has an oscillation frequency of between 20 and 60 kHz and more preferably between 45 and 50 kHz.

In such conditions, the bipolar ionising method according to the present invention generates about 50.000 ION-/cm3 (negative ions per cm3) and about 10.000 ION+/cm3 (positive ions per cm3). Figure 3a represents an ionisation circuit 20 according to another embodiment of the present invention, comprising an ionisation unit 24 substantially analogous to the one schematised in figure 2a, i.e. an ioniser with a tube, and equipped with an outer electrode 22 and with an inner electrode 21. The outer electrode 22 is connected to earth and the inner electrode 21 to a second winding 26 of a HVG transformer, having a first winding 27 fed with a current in direct voltage, for example with the current schematically represented in figure 3b of 12VDC. A voltage compensation circuit 29, comprising an oscillator 30, receives in input the supply of direct current and is connected in output to a MOS circuit 31, connected to the first winding 27 of the HVG transformer. The HVG transformer and the oscillator 30 modify the direct current into a high-voltage alternating current, of the type schematically represented in figure 3c, preferably at a voltage of 1.9 kVAC.

The ionisation unit 24 comprises a substantially cylindrical tube, made of quartz or another insulating dielectric material. The tube is equipped with an inner plate 21 and with an outer mesh 22 both made from an electrically conductive material, for example metallic. Said plate 21 and mesh 22 basically form the armatures of a condenser and extend substantially for the entire length of the tube. The mesh 22 is connected to earth, whereas the other armature, i.e. the plate 21 is connected to one end of a secondary winding 26 (high voltage) of a HVG transformer. Said winding 26, at the opposite end, is earthed.

Said HVG transformer is connected to the circuit 29 of the impulse type, which is substantially based on the use of an electronic switch 31. When the switch 31 is closed, the primary of the transformer is crossed by an electric current; when the switch is open, there is energy transfer to the secondary and to the ionising device connected to it. In greater detail, the primary winding 27 of said HVG transformer is connected to a supply line 32 in low direct voltage (12V) and to a control circuit 29 that essentially comprises a square wave oscillator 30, a driver stage 33 and an electronic MOS switch 31. Said switch 31 has a closing time given by the positive impulse of the square wave generated by the oscillator. The input signal V3,in at 12 VDC is shown in Fig. 3b. Fig. 3c shows the square wave of the oscillator that determines the closing of the switch 31, and the curve that represents the current in the secondary winding of the HVG transformer. The closing (conduction) time of the switch 31 corresponds in Fig. 3c to the time period between times tA and fe. At time £B the feeding to the transformer is interrupted and a leading edge 202 of the curve 201 is generated, corresponding to the passage of energy to the ionising device 24 and thus to the actual ionisation process. The opening and closing frequency of the switch preferably is such that the time period between two impulses, i.e. between two successive openings of the switch that generate the leading edges 202, is substantially equivalent to the time period necessary for the complete energy transfer from the primary to the secondary.

The ionisation circuit comprises a voltage control in case there are overvoltages that could damage the system (for example, up to 16 VDC with a nominal voltage of 12 VDC), and it also comprises a trimmer for adjusting the oscillation frequency.

Advantageously, the ionisation method and circuits according to the present invention allow the air to be ionised without excessively increasing the concentration of positive ions, not only compensating for the longer lifetime of the positive ions emitted by the ioniser, through greater production of negative ions, but also compensating for a concentration of positive ions emitted by other ionisation devices through a well-proportioned and adjustable production of such ions.

Claims

1. An ionisation method wherein the ionisation of the air is controlled to limit the generation of positive ions, obtaining a predetermined proportion between positive and negative ions.

2. Method according to claim 1, comprising an attenuation or reduction of the positive component of an ionisation voltage, to obtain said limitation of the generation of positive ions.

3. A method according to claim 2, wherein the air is ionised with at least one ionisation unit that comprises two electrodes separated by a body of dielectric material, one of said two electrodes (4c, 12) is connected to earth and the other electrode (3c, 11) is fed with a voltage V(t) having an alternating trend over time with respect to a zero voltage, wherein the RMS value (Veff,-) associated with negative half-waves of said voltage V(t) is greater than the RMS value (Veff,+) associated with the positive half-waves.

4. Method according to claim 3, wherein the live electrode (3c, 11) is connected to the secondary winding of a high voltage gate (HVG) transformer, and the positive half-waves of the voltage signal supplied to said electrode (3c, 11) are attenuated through passive components (3a, 3b, 4a, 4b, 15-19) obtaining a levelling of the peak values of the positive half-waves.

5. Method according to claims 3-4, wherein the ionisation unit is of the tube type, comprising a dielectric tube and two electrodes respectively inside and outside the tube.

6. Method according to claims 3-4, wherein the ionisation unit is of the needle type, comprising an electrode or needle or else a respective plurality of needles connected to a positive pole (3c), and correspondingly one or more needles connected to a negative pole (4c).

7. Method according to claim 2, wherein the air is ionised with at least one ionisation unit that comprises at least one electrode (3c) for the generation of positive ions, fed with a positive direct voltage, and at least one electrode (4c) for the generation of negative ions, fed with a negative direct voltage, said negative voltage having a higher absolute value than said positive voltage.

8. Method according to any one of the previous claims, the voltage of the electric field that causes the ionisation of the air having a nominal value of between 2 and 5 kV and more preferably between 2 and 3 kV.

9. Method according to claim 8, said electric field having an oscillation frequency of between 20 and 60 kHz and more preferably between 45 and 50 kHz.

10. Method according to claim 1, wherein an ionisation unit (24) is fed by a high voltage gate (HVG) transformer, and said transformer comprises a primary winding (27) connected to a feeding circuit (33) of the impulse type, and a secondary winding (26) connected to at least one electrode (21) of said ionisation device (24).

11. Method according to claim 10, wherein the primary winding (27) of the transformer is connected to earth by means of at least one electronic switch (31), so that the closing of said switch induces current in the primary winding of the transformer, and the opening of said switch causes an impulse of current in the secondary winding and energy transfer to the ionisation device.

12. Method according to claim 11, wherein the opening and closing frequency of the switch is such that the time period between two transfer to the secondary winding the energy obtained from the passage of current in the primary . during the closing time of the switch.

13. Method according to any one of the previous claims, said proportion preferably being about 1:4, i.e. 2/ 10 of positive ions and 8/ 10 of negative ions.

14. Ionisation method according to claim 1 characterised in that said limitation of positive ions is obtained through the steps of feeding an ionisation circuit with a voltage, of raising a positive half- wave and a negative half-wave of said alternating current with respect to time, reducing said positive half-wave, and feeding a first electrode of an ionisation unit with the resulting voltage, said ionisation unit having a second electrode that is earthed.

15. Ionisation method according to claim 14 characterised in that said positive and negative half-wave are rectified in a direct voltage of the current with positive and negative voltage values through passive components of said ionisation unit, said positive voltage value being less than a module of said negative voltage value.

16. Ionisation method according to claim 14 characterised in that said raising step lifts said voltage preferably to a value of 800VAC.

17. Ionisation method according to claim 14 characterised in that said reduction step levels a predetermined upper portion (SI 'J of said positive half- wave (SI).

18. Ionisation circuit of the air comprising an ionisation unit of the air and a circuit control portion for limiting the generation of positive ions to obtain a predetermined proportion between positive and negative ions.

19. Ionisation circuit according to claim 18, characterised in that said circuit portion comprises electrical components (3a, 3b, 4a, 4b, 15-17, 19) for the reduction of a positive component of an ionisation voltage and to obtain said limitation of the generation of positive ions.

20. Circuit according to claim 19, wherein the ionisation unit comprises two electrodes separated by a body of dielectric material, one of said two electrodes (4c, 12) is connected to earth and the other electrode (3c, 11) is fed with a voltage V(t) having an alternating trend over time with respect to a zero voltage, wherein the RMS value (Veff,-) associated with negative half-waves of said voltage V(t) is greater than the RMS value (Veff,+) associated with the positive half-waves.

21. Circuit according to claim 18, wherein the ionisation unit (24) is connected to a high voltage gate (HVG) transformer that comprises a primary winding (27) connected to a feeding circuit (33) of the impulse type, and a secondary winding (26) connected to at least one electrode (21) of said ionisation unit (24).

22. Circuit according to claim 21, wherein the primary winding (27) of the transformer is connected to earth by means of at least one electronic switch (31), to induce current in the primary winding of the transformer, through the closing of said switch, and to provide an impulse of current in the secondary winding and energy transfer to the ionisation unit, through the opening of said switch.