High voltage generating circuit, ion generating device and electrical apparatus

A high voltage generating circuit includes a boosting portion (e.g., a trigger coil (22)) for boosting DC voltage delivered from a DC power supply (26) so as to deliver high voltage at a secondary side, a switching element (e.g., a MOSFET (23)) for turning on and off current flowing in the primary side of the boosting portion, and a pulse signal generating portion (24B) for generating a pulse signal for controlling on and off of the switching element.

This nonprovisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2007-018920 filed in Japan on Jan. 30, 2007 and Patent Application No. 2007-090219 filed in Japan on Mar. 30, 2007, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a high voltage generating circuit for generating high voltage, an ion generating device having the high voltage generating circuit for emitting ions into a space so that a room environment can be improved, and an electrical apparatus equipped with the ion generating device. Note that the above-mentioned electrical apparatus may include an air conditioner, a dehumidifier, a humidifier, an air cleaner, a refrigerator, a fan heater, a microwave oven, a washing machine with a dryer, a cleaner, a pasteurizer and the like, for example, used mainly in a closed space (indoor, a room in a building, a sickroom or an operating room in a hospital, a car interior, a cabin of a plane or a ship, a warehouse, a chamber of a refrigerator and the like).

2. Description of Related Art

Generally speaking, if a large number of people are in a closed room such as an office or a meeting room with little ventilation, air pollutant including carbon dioxide exhausted by breathing, tobacco smoke, dust and the like increases so that minus ions having an effect of relaxing people may decrease in the air. In particular, existence of tobacco smoke may decrease the minus ions to approximately ½ to ⅕ of a normal state. Therefore, various types of ion generating devices are on the market conventionally in order to supply minus ions in the air.

However, all the conventional ion generating devices are the DC high voltage type that generates only minus ions by a DC voltage. Therefore, such the ion generating devices cannot actively remove floating germs or the like in the air though they can supply minus ions in the air.

In view of the above-mentioned problem, the applicant has invented the ion generating device that generates H+(H2O)mas plus ions and O2−(H2O)nas minus ions (m and n are natural numbers) in the air in substantially the same quantity, which are adhered to the floating germs or the like in the air so that the floating germ can be removed by decomposing action of active hydrogen peroxide (H2O2) and/or hydroxyl radical (•OH) generated on the occasion (see JP-A-2003-47651, for example).

Note that the above-mentioned invention is already brought into a practical use by the applicant. There are practical apparatuses including the ion generating device having a structure in which a discharging electrode is disposed outside a ceramic dielectric while an induction electrode is disposed inside the same, and the air cleaner, the air conditioner or the like equipped with the ion generating device.

FIG. 15is a circuit diagram showing a conventional example of the ion generating device that can generate H+(H2O)mas plus ions and O2−(H2O)nas minus ions (m and n are natural numbers) in substantially the same quantity. The conventional ion generating device shown inFIG. 15has a high voltage generating circuit for generating AC impulse high voltage and a discharging portion X1for generating ions by discharging the high voltage applied from the high voltage generating circuit. Furthermore, the above-mentioned high voltage generating circuit includes a resistor R1, a diode D1, a capacitor C1, a transformer T1and a semiconductor switching element S1.

In the conventional ion generating device shown inFIG. 15, the output voltage of the commercial AC power source E1is dropped by the resistor R1and is rectified by the diode D1as half-wave rectification, which is applied to the capacitor C1. When the capacitor C1is charged until the terminal voltage E2of the capacitor C1shown inFIG. 16Aincreases to a predetermined threshold value VTHshown inFIG. 16A, the semiconductor switching element S1is turned on so that the charged voltage of the capacitor C1is discharged. This discharge causes current flowing in the primary winding L1of the transformer T1so that energy is transmitted to the secondary winding L2. As a result, the AC impulse high voltage E3shown inFIG. 16Bis applied to the discharging portion X1. Just after that, the semiconductor switching element S1is turned off, so that charging of the capacitor C1is restarted.

The changing and the discharging described above are repeated, and thus the AC impulse high voltage shown inFIG. 16Bis applied to the discharging portion X1repeatedly. On this occasion, corona discharge is generated in the vicinity of the discharging portion X1so that the ambient air is ionized. As a result, plus ions of H+(H2O)mare generated when the positive voltage is applied while minus ions of O2−(H2O)nare generated when the negative voltage is applied (m and n are natural numbers). Therefore, it is possible to make both ions be adhered to the floating germs or the like in the air so that the floating germ can be removed by decomposing action of active hydrogen peroxide (H2O2) or hydroxyl radical (•OH) composing action generated on the occasion.

It is sure that the conventional ion generating device shown inFIG. 15can actively remove floating germs or the like in the air, so the room environment can be improved to be more comfortable.

However, the above-mentioned conventional ion generating device shown inFIG. 15has a problem as follows. Since it uses the commercial AC power source E1as an input power source, it needs the capacitor C11with high withstand voltage and large capacitance and the semiconductor switching element S1with high withstand voltage discharge for storing energy in the capacitor C1temporarily and switching between charge and discharge of the capacitor C1by the semiconductor switching element S1, which causes increase in the size.

In addition, the above-mentioned conventional ion generating device shown inFIG. 15cannot adjust the voltage to be applied to the discharging portion X1since the predetermined threshold value VTHof the semiconductor switching element S1and a voltage transforming ratio of the transformer T1determine the voltage to be applied to the discharging portion X1. Therefore, it has a problem that the discharging portion X1may be broken down when voltage exceeding the withstand voltage of the discharging portion X1is applied to the discharging portion X1.

In addition, the above-mentioned conventional ion generating device shown inFIG. 15cannot adjust the voltage to be applied to the discharging portion X1, which is determined by the predetermined threshold value VTHof the semiconductor switching element S1and the voltage transforming ratio of the transformer T1. Therefore, the same high voltage generating circuit thereof cannot support the case where the discharging portion X1has a different material or shape so that the discharge start voltage of the discharging portion X1is different.

In addition, the above-mentioned conventional ion generating device shown inFIG. 15has the problem that the number of discharge times of the capacitor C1per unit time, i.e., generating quantity of ions cannot be adjusted arbitrarily because the discharge energy is stored in the capacitor C1temporarily.

In addition, the above-mentioned conventional ion generating device shown inFIG. 15has a following problem. If the capacitance of the discharging portion X1increases due to deterioration of the discharging portion X1or adherence of foreign substances or the like, the output voltage from the high voltage generating circuit will be dropped (seeFIG. 17). When the output voltage becomes below the discharge start voltage of the discharging portion X1, the discharge may stop, i.e., generation of ions may stop.

SUMMARY OF THE INVENTION

A first object of the present invention is to provide a high voltage generating circuit that can be downsized, an ion generating device equipped with the high voltage generating circuit, and an electrical apparatus equipped with the ion generating device.

In addition, a second object is to provide a high voltage generating circuit that can adjust an output high voltage value, an ion generating device equipped with the high voltage generating circuit so that a breakdown of the discharging portion can be prevented, and an electrical apparatus equipped with the ion generating device.

In addition, a third object is to provide a high voltage generating circuit that can adjust the output high voltage value, an ion generating device equipped with the high voltage generating circuit so that a change in specifications of the high voltage generating circuit in accordance with the discharge start voltage of the discharging portion is not necessary, and an electrical apparatus equipped with the ion generating device.

In addition, a fourth object is to provide a high voltage generating circuit that can adjust generating frequency of the output high voltage, an ion generating device equipped with the high voltage generating circuit so that the generating quantity of ions can be controlled freely, and an electrical apparatus equipped with the ion generating device.

In addition, a fifth object is to provide a high voltage generating circuit that can keep the output high voltage value, an ion generating device equipped with the high voltage generating circuit that can adjust the output to be maintained at a constant value even if a capacitance value of the discharging portion increases so that the output high voltage value from the high voltage generating circuit is decreased, and an electrical apparatus equipped with the ion generating device.

In order to achieve the above-mentioned first object, a high voltage generating circuit according to the present invention includes a boosting portion for boosting DC voltage delivered from a DC power supply, so as to deliver high voltage at a secondary side, a switching element for turning on and off primary current of the boosting portion, and a pulse signal generating portion for generating a pulse signal for controlling on and off of the switching element. According to this structure, the DC voltage delivered from the DC power supply is supplied without using the commercial AC power source as the input power source. Therefore, the switching element is not required to be a high withstand voltage component, and it is not necessary to provide a capacitor with high withstand voltage and large capacitance for storing discharge energy temporarily. For this reason, the high voltage generating circuit can be downsized. However, if the DC voltage delivered from the DC power supply is too large, it is necessary to increase the withstand voltage of the switching element. Therefore, it is desirable that the DC voltage delivered from the DC power supply should be lower than or equal to 24 volts.

Furthermore, in order to achieve the above-mentioned second and third objects as to the high voltage generating circuit having the structure described above, it is preferable to adopt the structure in which the pulse signal delivered from the pulse signal generating portion has a variable pulse width. According to this structure, the high voltage value delivered from the high voltage generating circuit can be adjusted. Therefore, if the present invention is applied to the ion generating device, a breakdown of the discharging portion can be prevented. In addition, it becomes unnecessary to change specifications of the high voltage generating circuit in accordance with the discharge start voltage of the discharging portion.

Furthermore, in order to achieve the above-mentioned fourth object as to each of the high voltage generating circuits having the structures described above, it is preferable to adopt the structure in which the pulse signal delivered from the pulse signal generating portion has a variable pulse interval. According to this structure, generating frequency of the high voltage delivered from the high voltage generating circuit can be adjusted. Therefore, if the present invention is applied to the ion generating device, the number of generating times per unit time of the high voltage applied to the discharging portion, i.e., the number of discharge times per unit time of the discharging portion can be adjusted, so that the generating quantity of ions can be adjusted.

Furthermore, in order to achieve the above-mentioned fifth object as to each of the high voltage generating circuits having the structures described above, it is preferable to adopt the structure including a feedback voltage generating portion for generating feedback voltage that is DC voltage corresponding to a peak value of the high voltage delivered from the secondary side of the boosting portion, and a voltage comparing portion for comparing the feedback voltage with a reference voltage, in which the high voltage delivered from the secondary side of the boosting portion is kept to be a constant value based on a result of the comparison performed by the voltage comparing portion. According to this structure, it is possible to adjust so that the output is maintained to be a constant value even if the value of the high voltage delivered from the high voltage generating circuit is dropped. Therefore, if the present invention is applied to the ion generating device, it is possible to adjust so that the output is maintained to be a constant value even if capacitance of the discharging portion increases so that the high voltage value delivered from the high voltage generating circuit is dropped.

Furthermore, in order to achieve the above-mentioned fifth object as to each of the high voltage generating circuits having the structures described above, it is preferable to adopt the structure including a feedback voltage generating portion for generating feedback voltage that is DC voltage corresponding to a peak value of node voltage of a primary side of the boosting portion and the switching element, and a voltage comparing portion for comparing the feedback voltage with a reference voltage, in which the high voltage delivered from the secondary side of the boosting portion is kept to be a constant value based on a result of the comparison performed by the voltage comparing portion. According to this structure, it is possible to adjust so that the output is maintained to be a constant value even if the value of the high voltage delivered from the high voltage generating circuit is dropped. Therefore, if the present invention is applied to the ion generating device, it is possible to adjust so that the output is maintained to be a constant value even if capacitance of the discharging portion increases so that the high voltage value delivered from the high voltage generating circuit is dropped. Note that it is possible in this structure that the secondary side of the boosting portion is floating.

In the high voltage generating circuit having the structure for achieving the above-mentioned fifth object, if the feedback voltage is always lower than the reference voltage during a predetermined period, it is preferable, for example, to increase a pulse width of the pulse signal delivered from the pulse signal generating portion so that the high voltage delivered from the secondary side of the boosting portion can be maintained to be a constant value. Alternatively, it is possible to increase a DC voltage delivered from the DC power supply so that the high voltage delivered from the secondary side of the boosting portion can be maintained to be a constant value.

In case of adopting the structure of increasing the DC voltage delivered from the DC power supply so that the high voltage delivered from the secondary side of the boosting portion can be maintained to be a constant value, it is preferable, for example, that the high voltage generating circuit includes a chopper type booster switching regulator, and that the output voltage of the booster switching regulator is the DC voltage delivered from the DC power supply. If the feedback voltage is always lower than the reference voltage during a predetermined period, it is preferable to increase the number of switching times of the booster switching regulator per a predetermined time so that the high voltage delivered from the secondary side of the boosting portion can be maintained to be a constant value.

Furthermore, in case of adopting the structure of increasing the pulse width of the pulse signal delivered from the pulse signal generating portion so that the high voltage delivered from the secondary side of the boosting portion can be maintained to be a constant value, it is possible to set an upper limit to the pulse width of the pulse signal delivered from the pulse signal generating portion, and to provide an error output portion that produces an error output when the pulse width of the pulse signal delivered from the pulse signal generating portion reaches the upper limit. Thus, if the present invention is applied to the ion generating device, a user can recognize that capacitance of the discharging portion has increased from the error output so that maintenance of the discharging portion can be performed.

Furthermore, in case of adopting the structure of increasing the number of switching times of the booster switching regulator per a predetermined time so that the high voltage delivered from the secondary side of the boosting portion can be maintained to be a constant value, it is possible to set an upper limit to the number of switching times of the booster switching regulator per a predetermined time, and to provide an error output portion that produces an error output when the number of switching times of the booster switching regulator per a predetermined time reaches the upper limit. Thus, if the present invention is applied to the ion generating device, a user can recognize that capacitance of the discharging portion has increased from the error output so that maintenance of the discharging portion can be performed.

It is possible to adopt a structure in which the voltage comparing portion operates when power is turned on or only at a constant interval of time. Thus, power consumption of the voltage comparing portion can be reduced.

In each of the high voltage circuits having the structures described above, a transformer or a trigger coil can be used as the boosting portion, for example. A MOSFET or a bipolar transistor can be used as the switching element. The pulse signal generating portion can be a microcomputer for controlling the generation of the pulse signal by software or a customer specific LSI for controlling the generation of the pulse signal by hardware.

Furthermore, in each of the high voltage circuits having the structures described above, it is desirable to adopt a structure in which the boosting portion delivers one AC impulse high voltage corresponding to one pulse of the pulse signal delivered from the pulse signal generating portion.

Furthermore, in each of the high voltage circuits having the structures described above, it is preferable to adopt a structure in which the high voltage value delivered from the secondary side of the boosting portion changes in accordance with a value of the DC voltage delivered from the DC power supply, so that the above-mentioned second and third objects can be achieved.

An ion generating device according to the present invention includes a high voltage generating circuit having any one of the structures described above, and a discharging portion to which the high voltage delivered from the high voltage generating circuit, in which the discharging portion generates ions when the high voltage delivered from the high voltage generating circuit is applied to the discharging portion.

Furthermore, in order to achieve the above-mentioned second and third objects as to the ion generating device having the structure described above, it is preferable to adopt the structure in which a pulse width of the pulse signal delivered from the pulse signal generating portion provided in the high voltage generating circuit is adjusted so that the value of the high voltage delivered from the high voltage generating circuit can be adjusted.

Furthermore, in order to achieve the above-mentioned fourth object as to each of the ion generating devices having the structures described above, it is preferable to adopt the structure in which a pulse interval of the pulse signal delivered from the pulse signal generating portion provided in the high voltage generating circuit is adjusted so that generating quantity of ions can be controlled.

Furthermore, in each of the ion generating devices having the structures described above, it is preferable to adopt a structure in which a first rectifying portion (e.g., a diode) for rectifying the high voltage delivered from the secondary side of the boosting portion provided to the high voltage generating circuit into positive voltage, and a second rectifying portion (e.g., a diode) for rectifying the high voltage delivered from the secondary side of the boosting portion provided to the high voltage generating circuit into negative voltage are provided to the high voltage generating circuit, and the discharging portion has a first discharging portion to which the positive voltage from the first rectifying portion is applied and a second discharging portion to which the negative voltage from the second rectifying portion is applied. According to this structure, the first discharging portion to which the positive voltage is applied can generate plus ions and emit them in the air, while the second discharging portion to which the negative voltage is applied can generate minus ions and emit them in the air. In other words, both the plus and the minus ions are emitted separately. Therefore, the generated plus ions and minus ions are prevented from canceling each other and disappearing in the vicinity of the electrode of the discharging portion, so that the generated plus ions and minus ions can be emitted in the space effectively and with a balance.

Furthermore, in each of the ion generating devices having the structures described above, it is preferable that the discharging portion generates both the minus ions and the plus ions, and that the plus ions are H+(H2O)mwhile the minus ions are O2−(H2O)n(m and n are natural numbers), so that the floating germs or the like can be removed.

An electrical apparatus according to the present invention includes the ion generating device having any one of the structures described above, and a delivery portion for delivering ions generated by the ion generating device in the air.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.FIG. 1is a functional block diagram showing a structural example of an ion generating device according to the present invention. The ion generating device shown inFIG. 1includes an ion generating element11having a discharging portion and a high voltage generating circuit100for applying high voltage to the discharging portion. The high voltage generating circuit100includes a boosting portion12for boosting DC voltage supplied from a DC power supply16such as a battery so as to supply the high voltage to the discharging portion that is connected to a secondary side, a switching element13for turning on and off current flowing in a primary side of the boosting portion12, a pulse signal generating portion15for generating a pulse signal for controlling on and off of the switching element13, and a timer14for adjusting the pulse width and the pulse interval of the pulse signal. Furthermore, if it is not necessary to adjust the value of the high voltage delivered from the high voltage generating circuit100and to adjust generating frequency of the high voltage delivered from the high voltage generating circuit100, it is preferable to eliminate the timer14so as to fix the waveform of the pulse signal generated by the pulse signal generating portion15.

The ion generating device shown inFIG. 1does not use the commercial AC power source as the input power source, and the DC voltage delivered from the DC power supply16is supplied to the high voltage generating circuit100. Therefore, the switching element13is not required to be a high withstand voltage component, and it is not necessary to provide a capacitor with high withstand voltage and large capacitance for storing discharge energy temporarily. For this reason, the high voltage generating circuit100can be downsized. However, if the DC voltage delivered from the DC power supply16is too large, it is necessary to increase the withstand voltage of the switching element13. Therefore, it is desirable that the DC voltage delivered from the DC power supply16should be lower than or equal to 24 volts.

FIG. 2is a circuit diagram showing an embodiment of the ion generating device shown inFIG. 1. The ion generating device shown inFIG. 2includes an ion generating element21having a discharging portion and a high voltage generating circuit200for applying high voltage to the discharging portion. The high voltage generating circuit200includes a trigger coil22as a boosting portion for boosting the DC voltage supplied from a DC power supply26so as to deliver the high voltage to the discharging portion that is connected to the secondary side, a MOSFET23as a switching element for turning on and off current flowing in the primary side of the trigger coil22, and a processing unit24having a pulse signal generating portion24B for generating a pulse signal for controlling on and off of the MOSFET23, a timer24A for adjusting the pulse width and the pulse interval of the pulse signal. As an example of the processing unit24, there is a microcomputer for controlling by software the generation of the pulse signal and the adjustment of the pulse width and the pulse interval of the pulse signal, or a customer specific LSI for controlling by hardware the generation of the pulse signal and the adjustment of the pulse width and the pulse interval of the pulse signal.

A positive electrode of a DC power supply25is connected to a power source terminal of the processing unit24. A positive electrode of the DC power supply26is connected to an end of a primary winding L1and an end of a secondary winding L2of the trigger coil22. A negative electrode of the DC power supply25, a negative electrode of the DC power supply26and a GND terminal of the processing unit24are connected to the ground. The other end of the primary winding L1of the trigger coil22is connected to a drain terminal of the MOSFET23. A source terminal of the MOSFET23is connected to the ground. A gate terminal of the MOSFET23is connected to a pulse signal output terminal of the processing unit24. The other end of the secondary winding of the trigger coil22is connected to a discharge electrode of the discharging portion of the ion generating element21. An induction electrode of the discharging portion of the ion generating element21is connected to the ground.

Here, a structural example of the ion generating element21is shown inFIGS. 3A and 3B.FIG. 3Ais a top view of the ion generating element21, andFIG. 3Bis a cross sectional view of the ion generating element21cut along the line X-X.

The ion generating element shown inFIGS. 3A and 3Bincludes a dielectric27(an upper dielectric27A and a lower dielectric27B), a discharging portion (a discharge electrode28A, an induction electrode28B, a discharge electrode contact28C, an induction electrode contact28D, connecting terminals28E and28F, and connecting channels28G and28H), and a coating layer29.

The dielectric27includes the upper dielectric27A and the lower dielectric27B having substantially rectangular solid shapes glued to each other. If an inorganic material is selected as a material of the dielectric27, it is possible to use a ceramic such as high purity alumina, glass ceramics, forsterite, steatite or the like. Furthermore, if an organic material is selected as a material of the dielectric27, it is preferable to use a resin such as polyimide, glass epoxy or the like that is superior in oxidation resistance. However, considering an aspect of corrosion resistance, it is desirable to select an inorganic material as a material of the dielectric27. Further, considering formability and easiness of forming electrodes as described later, it is preferable to use a ceramic for forming the dielectric27. In addition, since it is desirable that insulation resistance between the discharge electrode28A and the induction electrode28B be uniform, the material of the dielectric27should preferably have little variation of density and a uniform insulation factor. Furthermore, the shape of the dielectric27may be other than the substantially rectangular solid shape (e.g., a disk shape, an elliptical plate shape, a polygonal plate shape or the like) or a cylindrical shape. However, considering productivity, it is preferable to adopt a plate-like shape (including a disk shape and a rectangular solid shape) like this structural example.

The discharge electrode28A is formed on the surface of the upper dielectric27A integrally to the upper dielectric27A. As a material of the discharge electrode28A, any material having electrical conductivity such as tungsten, for example, can be used without limitation, under the condition that the material is not melted or deformed by electric discharge.

In addition, the induction electrode28B is disposed in parallel with the discharge electrode28A via the upper dielectric27A. This arrangement enables a distance between the discharge electrode28A and the induction electrode28B (hereinafter referred to as an interelectrode distance) to be constant, so that insulation resistance between the discharge electrode and the induction electrode can be equalized. Thus, a state of discharge can be stabilized so that ions can be generated appropriately. Furthermore, if the dielectric27has a cylindrical shape, it is preferable to dispose the discharge electrode28A on the outer surface of the cylinder and to dispose the induction electrode28B like a shaft, so that the interelectrode distance can be constant. Although any material such as tungsten, for example, having electrical conductivity can be used without limitation as a material of the induction electrode28B similarly to the discharge electrode28A, under the condition that the material is not melted or deformed by electric discharge.

The discharge electrode contact28C is connected electrically to the discharge electrode28A via a connecting terminal28E formed on the same surface as the discharge electrode28A (i.e., on the surface of the upper dielectric27A) and the connecting channel28C. Therefore, the discharge electrode28A can be connected electrically to the secondary winding L2of the trigger coil22by connecting the discharge electrode contact28C to an end of a lead wire (a copper wire, an aluminum wire or the like) and by connecting the other end of the lead wire to the other end of the secondary winding L2of the trigger coil22.

The induction electrode contact28D is connected electrically to the induction electrode28B via a connecting terminal28F formed on the same surface as the induction electrode28B (i.e., on the surface of the lower dielectric27B) and the connecting channel28H. Therefore, the induction electrode28B can be set to the GND potential by connecting the induction electrode contact28D to an end of a lead wire (a copper wire, an aluminum wire or the like) and by connecting the other end of the lead wire to the ground.

Furthermore, in the ion generating element shown inFIGS. 3A and 3B, the discharge electrode28A has acute angle portions for concentrating electric field so that local discharge can be generated.

Next, with reference toFIG. 2again, an operation of the ion generating device shown inFIG. 2will be described. When the MOSFET23of the ion generating device shown inFIG. 2is turned on temporarily by the pulse signal delivered from the processing unit24, current flows in the primary winding L1of the trigger coil22. Then, the secondary winding L2of the trigger coil22generates high voltage depending on a turns ratio by mutual induction, which is applied to the discharge electrode of the discharging portion of the ion generating element21. After that, the MOSFET23becomes a turned-off state until the next pulse signal is delivered at a time interval controlled by the timer24A of the processing unit24, so the high voltage is not applied to the discharge electrode of the discharging portion of the ion generating element21. The operation of generating the high voltage is repeated in accordance with the pulse signal delivered at a time interval controlled by the timer24A of the processing unit24.

The voltages at the individual portions in the ion generating device shown inFIG. 2have waveforms as shown inFIGS. 4A to 4C. Here,FIG. 4Ashows a waveform of the voltage applied to the trigger coil22from the DC power supply26, i.e., the input voltage of the trigger coil22,FIG. 4Bshows a waveform of the pulse signal delivered from the processing unit24, i.e., the gate signal of the MOSFET23, andFIG. 4Cshows a waveform of the output voltage of the trigger coil22.

The AC impulse high voltage shown inFIG. 4Cis applied to the discharge electrode of the discharging portion of the ion generating element21. On this occasion, if the voltage that is applied to discharge electrode of the discharging portion of the ion generating element21reaches discharge start voltage ±VBDof the ion generating element21(seeFIG. 4C), corona discharge is generated on the surface and the vicinity of the ion generating element21so that the surrounding air is ionized. Since plus ions of H+(H2O)mare generated when the positive voltage is applied while minus ions of O2−(H2O)nare generated when the negative voltage is applied (m and n are natural numbers), substantially the same quantity of H+(H2O)mas plus ions and O2−(H2O)nas minus ions (m and n are natural numbers) are generated.

In addition, as to the ion generating device shown inFIG. 2, a peak value of the high voltage generated at the secondary winding L2of the trigger coil22can be adjusted arbitrarily by adjusting at least one of the pulse width of the pulse signal delivered from the processing unit24and the voltage applied to the trigger coil22from the DC power supply26. Therefore, a breakdown of the discharging portion of the ion generating element21can be prevented. In addition, it becomes unnecessary to change specifications of the high voltage generating circuit in accordance with the discharge start voltage of the discharging portion of the ion generating element21. Furthermore, the number of generating times per unit time of the AC impulse high voltage applied to the discharge electrode of the discharging portion of the ion generating element21, i.e., the number of discharge times per unit time of the ion generating element21can be adjusted by adjusting the pulse interval of the pulse signal delivered from the processing unit24.

Examples will be described, in which discharge is generated by the high voltage generating circuit200according to the present invention as for three types of ion generating elements including the ion generating element A that starts discharge at ±1.5 kilovolts, the ion generating element B that starts discharge at ±2.0 kilovolts, and the ion generating element C that starts discharge at ±3.0 kilovolts as shown in Table 1 in the ion generating device shown inFIG. 2.

A first example will be described, which is for performing the discharge of the ion generating elements having different discharge start voltage values as shown in Table 1 (the ion generating element A and the ion generating element B). The voltage that is applied to the trigger coil22from DC power supply26(the input voltage of the trigger coil22) is supposed to be 5 volts as shown inFIG. 5A, and the pulse width of the pulse signal that is delivered from the processing unit24is supposed to be 0.5 μsec like the first pulse shown inFIG. 5B. Then, the voltage that is generated at the secondary winding L2of the trigger coil22(i.e., the output voltage of the trigger coil22) becomes ±1.6 kilovolts as the peak value like the first AC impulse high voltage shown inFIG. 5C, so that the ion generating element A having the discharge start voltage of ±1.5 kilovolts can discharge. However, under this condition the ion generating element B having the discharge start voltage of ±2.0 kilovolts cannot discharge. Therefore, the voltage applied to the trigger coil22from the DC power supply26(i.e., the input voltage of the trigger coil22) is maintained to be 5 volts as shown inFIG. 5A, while the pulse width of the pulse signal delivered from the processing unit24is increased to be 1.0 μsec like the second pulse shown inFIG. 5B. In this case, the voltage generated at the secondary winding L2of the trigger coil22(the output voltage of the trigger coil22) increases to ±2.1 kilovolts as the peak value like the second AC impulse high voltage shown inFIG. 5C, so that the ion generating element B having the discharge start voltage of ±2.0 kilovolts can discharge. A relationship between the pulse width of the pulse signal delivered from the processing unit24and the voltage generated at the secondary winding L2of the trigger coil22(the output voltage of the trigger coil22) in the first example is shown in Table 2.

Note that the pulse width values of 0.5 μsec and 1.0 μsec are merely examples, and that the output voltage of the trigger coil22varies in accordance with the number of turns of the windings L1and L2of the trigger coil22, and the turned-on time of the MOSFET23and the like. In other words, the voltage generated at the secondary winding L2of the trigger coil22(the output voltage of the trigger coil22) can be controlled arbitrarily by adjusting the pulse width in accordance with the components that are used.

Next, a second example will be described, which is for performing the discharge of the ion generating elements having different discharge start voltage values as shown in Table 1 (the ion generating element A and the ion generating element B). The voltage that is applied to the trigger coil22from the DC power supply26(the input voltage of the trigger coil22) is supposed to be 5 volts as shown inFIG. 6A, and the pulse width of the pulse signal that is delivered from the processing unit24is supposed to be 0.5 μsec like the first pulse shown inFIG. 6B. Then, the voltage generated at the secondary winding L2of the trigger coil22(i.e., the output voltage of the trigger coil22) becomes ±1.6 kilovolts as the peak value like the first AC impulse high voltage shownFIG. 6C, so that the ion generating element A having the discharge start voltage of ±1.5 kilovolts can discharge. However, under this condition the ion generating element B having the discharge start voltage of ±2.0 kilovolts cannot discharge. Therefore, the pulse width of the pulse signal delivered from the processing unit24is maintained to be 0.5 μsec as shown inFIG. 6B, while the voltage applied to the trigger coil22from the DC power supply26(i.e., the input voltage of the trigger coil22) is increased to be 10 volts as shown inFIG. 6A. In this case, the voltage generated at the secondary winding L2of the trigger coil22(the output voltage of the trigger coil22) increases to ±2.1 kilovolts as the peak value like the second AC impulse high voltage shown inFIG. 6C, so that the ion generating element B having the discharge start voltage of ±2.0 kilovolts can discharge. A relationship between the voltage applied to the trigger coil22from the DC power supply26(the input voltage of the trigger coil22) and the voltage generated at the secondary winding L2of the trigger coil22(the output voltage of the trigger coil22) in the second example is shown in Table 3.

The value 0.5 μsec as the pulse width and the values 5 volts and 10 volts as the voltage applied to the trigger coil22from the DC power supply26(the input voltage of the trigger coil22) are merely example, and the output voltage of the trigger coil22varies in accordance with the number of turns of the windings L1and L2of the trigger coil22, and the turned-on time of the MOSFET23and the like. In other words, the voltage generated at the secondary winding L2of the trigger coil22(the output voltage of the trigger coil22) can be controlled arbitrarily by adjusting the pulse width and the input voltage of the trigger coil22in accordance with the components that are used.

Next, a third example will be described, which is for performing the discharge of the ion generating elements having different discharge start voltage values as shown in Table 1 (the ion generating element A and the ion generating element C). The voltage that is applied to the trigger coil22from the DC power supply26(the input voltage of the trigger coil22) is supposed to be 5 volts as shown inFIG. 7A, and the pulse width of the pulse signal that is delivered from the processing unit24is supposed to be 0.5 μsec like the first pulse shown inFIG. 7B. Then, the voltage that is generated at the secondary winding L2of the trigger coil22(i.e., the output voltage of the trigger coil22) becomes ±1.6 kilovolts as the peak value like the first AC impulse high voltage shown inFIG. 7C, so that the ion generating element A having the discharge start voltage of ±1.5 kilovolts can discharge. However, under this condition the ion generating element C having the discharge start voltage of ±3.0 kilovolts cannot discharge. Therefore, the voltage applied to the trigger coil22from the DC power supply26(i.e., the input voltage of the trigger coil22) is increased to 10 volts as shown inFIG. 7A, while the pulse width of the pulse signal delivered from the processing unit24is increased to be 1.0 μsec like the second pulse shown inFIG. 7B. Then, the voltage generated at the secondary winding L2of the trigger coil22(the output voltage of the trigger coil22) increases to ±3.1 kilovolts as the peak value like the second AC impulse high voltage shown inFIG. 7C, so that the ion generating element C having the discharge start voltage of ±3.0 kilovolts can discharge. A relationship among the voltage applied to the trigger coil22from the DC power supply26(the input voltage of the trigger coil22), the pulse width of the pulse signal delivered from the processing unit24and the voltage generated at the secondary winding L2of the trigger coil22(the output voltage of the trigger coil22) in the third example is shown in Table 4.

The values 0.5 μsec and 1.0 μsec as the pulse width and the values 5 volts and 10 volts as the voltage applied to the trigger coil22from the DC power supply26(the input voltage of the trigger coil22) are merely example, and the output voltage of the trigger coil22varies in accordance with the number of turns of the windings L1and L2of the trigger coil22, and the turned-on time of the MOSFET23and the like. In other words, the voltage generated at the secondary winding L2of the trigger coil22(the output voltage of the trigger coil22) can be controlled arbitrarily by adjusting the pulse width and the input voltage of the trigger coil22in accordance with the components that are used.

Next, an example will be described, in which the generating quantity of ions is increased as to the ion generating device shown inFIG. 2. If the pulse interval of the pulse signal delivered from the processing unit24is decreased from 2 milliseconds as the interval between the first pulse and the second pulse shown inFIG. 8Bto 1 millisecond as the interval between the second pulse to the third pulse, a frequency of the voltage generated at the secondary winding L2of the trigger coil22(the output voltage of the trigger coil22) increases from the 500 Hz as a frequency of the first and the second AC impulse high voltages shown inFIG. 8Cto 1 kHz as a frequency of the second and the third AC impulse high voltages. In other words, the number of discharge times at the discharging portion of the ion generating element21is doubled, so the generating quantity of ions is also doubled in theory.

Furthermore, although the MOSFET23is used as the switching element for turning on and off the current flowing in the primary side of the boosting portion in the ion generating device shown inFIG. 2, it is possible to use a bipolar transistor instead of the MOSFET23to have the structure shown inFIG. 9so that the same effect can be obtained.

Furthermore, although the trigger coil22is used as the boosting portion in the ion generating device shown inFIG. 2, it is possible to use a transformer instead of the trigger coil22to have the structure shown inFIG. 10so that the same effect can be obtained. In this case, an end of the secondary winding of the transformer is connected electrically to the discharge electrode of the ion generating element21, while the other end of the secondary winding of the transformer is connected electrically to the induction electrode of the ion generating element21.

In addition, the ion generating device according to the present invention is not limited to the ion generating device that generates the plus ions and the minus ions by the same quantity. It is possible to adopt another structure in which a rectifying diode is disposed on the secondary side of the trigger coil22as shown inFIG. 11of the ion generating device shown inFIG. 2so that only plus ions are generated. Alternatively, it is possible to adopt another structure in which a rectifying diode is disposed on the secondary side of the trigger coil22as shown inFIG. 12of the ion generating device shown inFIG. 2so that only minus ions are generated. Although the ion generating device shown inFIGS. 11 and 12cannot remove floating germs or the like, it can achieve the first to the fourth objects described above.

Furthermore, although one AC impulse high voltage is generated corresponding to one pulse in the pulse signal delivered from the processing unit24inFIGS. 4A to 4C,5A to5C,6A to6C,7A to7C and8A to8C, it is possible to adopt another structure in which one AC impulse high voltage is generated corresponding to a plurality of pulses in the pulse signal delivered from the processing unit24.

Next, a structural example of the ion generating device according to the present invention equipped with a plurality of discharging portions will be described with reference toFIG. 13. The ion generating device shown inFIG. 13includes an ion generating element32having two discharging portions and the high voltage generating circuit that applies high voltage to the discharging portions. The high voltage generating circuit provided to the ion generating device shown inFIG. 13has a structure including rectifying diodes30and31added to the high voltage generating circuit200provided to the ion generating device shown inFIG. 2. The anode of the rectifying diode30and the cathode of the rectifying diode31are connected to the secondary winding L2of the trigger coil22, and the cathode of the rectifying diode30is connected electrically to a first discharge electrode33A of the first discharging portion of the ion generating element32, and the anode of the rectifying diode31is connected electrically to a second discharge electrode34A of the second discharging portion of the ion generating element32. Furthermore, a first induction electrode33B of the first discharging portion of the ion generating element32and a second induction electrode34B of the second discharging portion of the same are connected to the ground.

According to this structure, plus ions are generated and emitted in the air by the first discharging portion of the ion generating element32to which the positive voltage is applied, while minus ions are generated and emitted in the air by the second discharging portion of the ion generating element32to which the negative voltage is applied. In other words, both plus and minus ions are emitted individually. Therefore, the generated plus ions and minus ions can be prevented from canceling each other and disappearing in the vicinity of the electrode of the ion generating element, so that the generated plus ions and minus ions can be emitted in the space effectively and with a balance.

Here, a structural example of the ion generating element32is shown inFIGS. 14A and 14B.FIG. 14Ais a top view of the ion generating element32, andFIG. 14Bis a cross section of the ion generating element32cut along the line X-X.

The ion generating element shown inFIGS. 14A and 14Bincludes a first discharging portion (the first discharge electrode33A, the first induction electrode33B, a discharge electrode contact33C, an induction electrode contact33D, connecting terminals33E and33F, and connecting channels33G and33H), a second discharging portion (the second discharge electrode34A, the second induction electrode34B, a discharge electrode contact34C, an induction electrode contact34D, connecting terminals34E and34F, and connecting channels34G and34H), a dielectric35(an upper dielectric35A and a lower dielectric35B), and a coating layer36. The ion generating element shown inFIGS. 14A and 14Bhas a structure in which two ion generating elements shown inFIGS. 3A and 3Bare combined. The structure of the ion generating element shown inFIGS. 3A and 3Bis already described in detail, so detailed description of the structure of the ion generating element shown inFIGS. 14A and 14Bwill be omitted.

Next, the ion generating device that can achieve the fifth object described above will be described.FIG. 18is a circuit diagram showing an embodiment of the ion generating device that can achieve the fifth object described above. Note that the same parts inFIG. 18as those inFIG. 2will be denoted by the same references.

The ion generating device shown inFIG. 18is equipped with the high voltage generating circuit that can maintain the output voltage to be a constant value by a feedback of the delivered high voltage value, and it can adjust so as to maintain the output to be a constant value even if the value of the high voltage delivered from the high voltage generating circuit is decreased because of increase of capacitance of the discharging portion.

The ion generating device shown inFIG. 18includes the ion generating element21having the discharging portion and a high voltage generating circuit300for applying high voltage to the discharging portion. The high voltage generating circuit300includes the trigger coil22as the boosting portion that boosts the DC voltage delivered from the DC power supply26and supplies the high voltage to the discharging portion that is connected to the secondary side, a bipolar transistor TR1as the switching element that turns on and off current flowing in the primary side of the trigger coil22, a processing unit24′ having the pulse signal generating portion24B that generates the pulse signal for controlling on and off of the bipolar transistor TR1, the timer24A for adjusting pulse width and pulse interval of the pulse signal, a reference voltage circuit24C for delivering reference voltage VREF, and a voltage comparing portion24D for comparing the feedback voltage VFBwith the reference voltage VREF, a voltage divider circuit37having resistors R11and R12for dividing the high voltage boosted by the trigger coil22, and a peak hold circuit38having a diode D11, a capacitor C11and a resistor R13for rectifying the output voltage of the voltage divider circuit37and smoothing the same so as to generate the feedback voltage VFB. As an example of the processing unit24′, there is a microcomputer for controlling by software the generation of the pulse signal, the adjustment of pulse width and pulse interval of the pulse signal and comparison of the feedback voltage VFBwith the reference voltage VREF, or a customer specific LSI for controlling by hardware the generation of the pulse signal, the adjustment of the pulse width and the pulse interval of the pulse signal and comparison of the feedback voltage VFBwith the reference voltage VREF.

A positive electrode of the DC power supply25is connected to a power source terminal of the processing unit24′. A positive electrode of the DC power supply26is connected to an end of a primary winding L1and an end of a secondary winding L2of the trigger coil22. A negative electrode of the DC power supply25, a negative electrode of the DC power supply26and a GND terminal of the processing unit24′ are connected to the ground. The other end of the primary winding L1of the trigger coil22is connected to a collector terminal of an npn-type bipolar transistor TR1. An emitter terminal of the bipolar transistor TR1is connected to the ground. A base terminal of the bipolar transistor TR1is connected to a pulse signal output terminal of the processing unit24′. The other end of the secondary winding L2of the trigger coil22is connected to a discharge electrode of the discharging portion of the ion generating element21and an end of the resistor R11. An induction electrode of the discharging portion of the ion generating element21is connected to the ground. The other end of the resistor R11is connected to an end of the resistor R12and an anode terminal of the diode D11. The other end of the resistor R11is connected to the ground. A cathode terminal of the diode D11is connected to an end of the capacitor C11, an end of the resistor R13and an input terminal of feedback voltage of the processing unit24′. The other end of the capacitor C11and the other end of the resistor R13are connected to the ground. For example, if the high voltage generating circuit300applies the AC impulse high voltage having a peak value of ±1.5 kilovolts to the ion generating element21and if the feedback voltage VFBis set to a value of +1.5 volts, constants of the circuit elements are set as follows, for example. A resistance value of the resistor R11is set to 1 megohms, a resistance value of the resistor R12is set to 1 kilohms, a capacitance value of the capacitor C11is set to 0.01 microfarads, and a resistance value of the resistor R13is set to 1 megohm.

Next, an operation of the ion generating device shown inFIG. 18will be described. As for the ion generating device shown inFIG. 18, when the bipolar transistor TR1is turned on temporarily by the pulse signal delivered from the processing unit24′ so that current flows in the primary winding L1of the trigger coil22, its mutual induction makes the secondary winding L2of the trigger coil22generate high voltage determined by the turns ratio, which is applied to the discharge electrode of the discharging portion of the ion generating element21. At the same time, the high voltage generated by the trigger coil22is divided by the voltage divider circuit37that includes the resistor R11and the resistor R12. The output voltage of the voltage divider circuit37is supplied to the peak hold circuit38and is rectified by the diode D11. Then, a peak value of the voltage is held by the capacitor C11and the resistor R13and is converted into the feedback voltage VFB. The feedback voltage VFB delivered from the peak hold circuit38is supplied to the feedback input terminal of the processing unit24′. Then, the voltage comparing portion24D of the processing unit24′ compares the feedback voltage VFB with the reference voltage VREF. If the feedback voltage VFB is always lower than the reference voltage VREF during a predetermined period, i.e., if the output voltage of the high voltage generating circuit300drops, the timer24A changes its setting so as to increase only the pulse width of the pulse signal delivered from the processing unit24′ without changing the pulse interval of the same. Thus, if the output voltage of the high voltage generating circuit300drops, the pulse width of the pulse signal delivered from the processing unit24′ is increased so that the output voltage of the high voltage generating circuit300increases. Therefore, the output voltage of the high voltage generating circuit300can be maintained at a constant value.

After that, the bipolar transistor TR1is turned off so that high voltage is not applied to discharge electrode of the discharging portion of the ion generating element21until the next pulse signal is delivered at a time interval controlled by the timer24A of the processing unit24′. The operation of generating the high voltage is repeated responding to the pulse signal that is produced at an interval controlled by the timer24A of the processing unit24′.

Here, an operation of the peak hold circuit38will be described with reference toFIGS. 19A and 19B.FIGS. 19A and 19Bare diagrams showing voltage waveforms at individual portions of the peak hold circuit38. The voltage E4shown inFIG. 19Ais an input voltage of the peak hold circuit38. The voltage E5shown inFIG. 19Bis a voltage after rectification by the diode D11and peak hold by the capacitor C11and the resistor R13, which is the output voltage of the peak hold circuit38. The voltage E6shown inFIG. 19Bis the voltage after rectification by the diode D11. The input voltage E4of the peak hold circuit38is rectified by the diode D11as the half-wave rectification to be the voltage E6shown inFIG. 19B. Then, the capacitor C11is charged as the voltage E6after the half-wave rectification increases during the period t1-t2. Since the time for the capacitor C11to be charged is usually short, the output voltage E5of the peak hold circuit38substantially follows the voltage E6after the half-wave rectification. After that, the capacitor C11is discharged during the period t2-t3. The discharge time is determined by a time constant that is a product of a capacitance value of the capacitor C11and a resistance value of the resistor R13. During the period in which the capacitor C11is being discharged, the output voltage E5of the peak hold circuit38does not follow the voltage E6after the half-wave rectification. As a result, the output voltage E5of the peak hold circuit38has a smooth waveform after the peak hold compared with the input voltage E4of the peak hold circuit38.

Voltages at individual portions of the ion generating device shown inFIG. 18have waveforms as shown inFIGS. 20A to 20E. Here,FIG. 20Ashows a waveform of the voltage applied to the trigger coil22from the DC power supply26, i.e., a waveform of the input voltage of the trigger coil22,FIG. 20Bshows a waveform of the pulse signal delivered from the processing unit24′, i.e., a waveform of a base signal of the bipolar transistor TR1,FIG. 20Cshows a waveform of the output voltage of the trigger coil22,FIG. 20Dshows a waveform of a voltage supplied to the peak hold circuit38from the voltage divider circuit37, andFIG. 20Eshows a waveform of the feedback voltage VFBdelivered from the peak hold circuit38and a waveform of the reference voltage VREFdelivered from the reference voltage circuit24C of the processing unit24′.

FIGS. 21A to 21Eshow voltage waveforms at individual portions of the ion generating device shown inFIG. 18, indicating the state in which the feedback circuit (the voltage divider circuit37, the peak hold circuit38, the reference voltage circuit24C, and the voltage comparing portion24D) works for maintaining the output voltage of the high voltage generating circuit300when the output voltage of the high voltage generating circuit300decreases in accordance with an influence of the increase of capacitance in the discharging portion of the ion generating element21.FIG. 21Ashows a waveform of the voltage applied to the trigger coil22from the DC power supply26, i.e., the input voltage of the trigger coil22,FIG. 21Bshows a waveform of the pulse signal delivered from the processing unit24′, i.e., the base signal of the bipolar transistor TR1,FIG. 21Cshows a waveform of the output voltage of the trigger coil22,FIG. 21Dshows a waveform of the voltage that is supplied to the peak hold circuit38from the voltage divider circuit37,FIG. 21Eshows a waveform of the feedback voltage VFBdelivered from the peak hold circuit38and a waveform of the reference voltage VREFdelivered from the reference voltage circuit24C in the processing unit24′.

The timer24A sets the pulse width in the next pulse interval in accordance with the output voltage level of the voltage comparing portion24D at each pulse interval. In the first pulse interval T1there is a period in which the output voltage of the voltage comparing portion24D has a high level (seeFIG. 21E), so the timer24A sets the pulse width at the second pulse interval T2to 0.5 μsec (standard value). In the second pulse interval T2, the output voltage of the high voltage generating circuit300drops under the influence of increase of capacitance in the discharging portion of the ion generating element (seeFIG. 21C). As a result, the feedback voltage VFBis always below the reference voltage VREFso that there is no period in which the output voltage of the voltage comparing portion24D has a high level (seeFIG. 21E). Therefore, the timer24A sets the pulse width at the third pulse interval T3to 1.0 μsec detailed description thereof will be omitted.

The ion generating device shown inFIG. 25adopts a method of boosting the input voltage of the trigger coil22from the voltage of the DC power supply26by increasing the number of pulses per a predetermined time of a control signal for controlling the switching transistor of the chopper type booster switching regulator39(by increasing the number of switching times per a predetermined time) so as to increase the output voltage of a high voltage generating circuit500when the feedback voltage VFBis always below the reference voltage VREFduring a predetermined period. Therefore, the ion generating device shown inFIG. 25is different from the ion generating device shown inFIG. 18in that the former has the additional booster switching regulator39and in the inner structure of the processing unit.

The booster switching regulator39includes a bipolar transistor TR2that is a switching transistor, a coil L11, a diode D12, and a capacitor C12. A processing unit24″ includes an additional pulse signal generating portion24E for the booster switching regulator that delivers a pulse signal for switching the booster switching regulator39. The pulse width of the pulse signal for switching current that flows in the primary winding L1of the trigger coil22can be constant. Therefore, it is structured so that a result of the voltage comparing portion24D is not reflected on the timer24A but is reflected on the number of pulses of the pulse signal delivered from the pulse signal generating portion24E for the booster switching regulator.

Here, an operation of the booster switching regulator having the same structure as the booster switching regulator39will be described with reference toFIGS. 26A to 26C. First, when the transistor TR is turned on, the energy is stored in the coil L. On this occasion, the input side of the coil L becomes positive potential while the output side of the same becomes negative potential (seeFIG. 26A). Next, when the transistor TR is turned off, the coil L permits the current to flow continuously following Lenz's law, so that the stored energy is discharged. On this occasion, the output side of the coil L becomes positive potential while the input side becomes negative potential. Since the transistor TR is turned off, the current flows through the diode D into the capacitor C and the load OUT (seeFIG. 26B). When the transistor TR is turned on again, the coil L stores energy again. The energy stored in the capacitor C causes current flowing in the load OUT. The energy stored in the capacitor C flows only into the load OUT without flowing into the transistor TR because of the diode D (seeFIG. 26C). If energy stored in the coil is large, the energy to be stored in the capacitor C increases so that the voltage rises.

Voltages at individual portions of the ion generating device shown inFIG. 25have waveforms as shown inFIGS. 27A to 27F. Here,FIG. 27Ashows a waveform of the pulse signal delivered from the processing unit24″ to the booster switching regulator39, i.e., a waveform of the base signal of the bipolar transistor TR2.FIG. 27Bshows a waveform of the voltage to be applied to the trigger coil22that is boosted by the booster switching regulator39from the voltage of the DC power supply26, i.e., a waveform of the input voltage of the trigger coil22.FIG. 27Cshows a waveform of the pulse signal delivered from the processing unit24″ to the bipolar transistor TR1, i.e., a waveform of the base signal of the bipolar transistor TR1.FIG. 27Dshows a waveform of the output voltage of the trigger coil22.FIG. 27Eshows a waveform of the voltage that is supplied from the voltage divider circuit37to the peak hold circuit38.FIG. 27Fshows a waveform of the feedback voltage VFBdelivered from the peak hold circuit38and the reference voltage VREFthat is delivered from the reference voltage circuit24C of the processing unit24″.

FIGS. 28A to 28Fshow voltage waveforms at individual portions of the ion generating device shown inFIG. 25, indicating the state in which the feedback circuit (including the voltage divider circuit37, the peak hold circuit38, the reference voltage circuit24C, and the voltage comparing portion24D) works for maintaining the output voltage of the high voltage generating circuit500when the output voltage of the high voltage generating circuit500drops in accordance with an influence of increase of capacitance in the discharging portion of the ion generating element21.FIG. 28Ashows a waveform of the pulse signal delivered from the processing unit24″ to the booster switching regulator39, i.e., a waveform of the base signal of the bipolar transistor TR2.FIG. 28Bshows a waveform of the voltage to be applied to the trigger coil22that is boosted by the booster switching regulator39from the voltage of the DC (seeFIG. 21B). Note that the pulse width values 0.5 μsec and 1.0 μsec are examples.

Next, another embodiment of the ion generating device that can achieve the fifth object described above is shown inFIG. 22. Note that the same parts shown inFIG. 22as those shown inFIG. 18are denoted by the same references, so that detailed description thereof will be omitted.

The ion generating device shown inFIG. 22is different from the ion generating device shown inFIG. 18in that the former generates the feedback voltage VFBbased on the voltage generated by output current I1flowing in the resistor R14, but another operations for the high voltage output and maintaining the output voltage by the feedback circuit are the same as the ion generating device shown inFIG. 18. For example, using the feedback voltage VFBat the +1.5 volts generated based on the voltage generated when the output current I1that is 15 mA flows in the resistor R14, a resistance value of the resistor R14is set to 100 ohms, a capacitance value of the capacitor C1is set to 0.01 microfarads, and a resistance value of the resistor R13is set to 1 megohm for setting circuit element constants as an example.

FIGS. 23A to 23Eshow voltage waveforms at individual portions of the ion generating device shown inFIG. 22.FIGS. 24A to 24Fshow voltage waveforms at individual portions of the ion generating device shown inFIG. 22, indicating the state in which the feedback circuit (including the resistor R14, the peak hold circuit38, the reference voltage circuit24C, and the voltage comparing portion24D) works for maintaining the output voltage of the high voltage generating circuit400when the output voltage of the high voltage generating circuit400decreases in accordance with an influence of increase of capacitance in the discharging portion of the ion generating element21. The voltage waveforms shown inFIGS. 23A to 23Eare similar to voltage waveforms shown inFIGS. 20A to 20E, and voltage waveforms shown inFIGS. 24A to 24Eare similar to voltage waveforms shown inFIGS. 21A to 21E. Therefore, detailed description thereof will be omitted here.

Next, still another embodiment of the ion generating device that can achieve the fifth object described above is shown inFIG. 25. Note that the same parts shown inFIG. 25as those shown inFIG. 18are denoted by the same references, so that power supply26, i.e., a waveform of the input voltage of the trigger coil22.FIG. 28Cshows a waveform of the pulse signal delivered from the processing unit24″ to the bipolar transistor TR1, i.e., a waveform of the base signal of the bipolar transistor TR1.FIG. 28Dshows a waveform of the output voltage of the trigger coil22.FIG. 28Eshows a waveform of the voltage supplied from the voltage divider circuit37to the peak hold circuit38.FIG. 28Fshows a waveform of the feedback voltage VFBdelivered from the peak hold circuit38and a waveform of the reference voltage VREFdelivered from the reference voltage circuit24C of the processing unit24″.

The pulse signal generating portion24E for the booster switching regulator sets the number of pulses during the next predetermined time in accordance with the output voltage level of the voltage comparing portion24D at each predetermined time. In a first predetermined time PT1, there is a period in which the output voltage of the voltage comparing portion24D has a high level (seeFIG. 28F), so the pulse signal generating portion24E for the booster switching regulator sets the number of pulses at the second predetermined time PT2to three (a standard value). At the second predetermined time PT2, the output voltage of the high voltage generating circuit500drops because of an influence of the increased capacitance of the discharging portion of the ion generating element (seeFIG. 28D). As a result, the feedback voltage VFBis always below the reference voltage VREFso that there is no period in which the output voltage of the voltage comparing portion24D has a high level (seeFIG. 28F). Therefore, the pulse signal generating portion24E for the booster switching regulator sets the number of pulses at a third predetermined time PT3to six (seeFIG. 28A). Note that the number of pulses3and6are examples.

Next, still another embodiment of the ion generating device that can achieve the fifth object described above is shown inFIG. 29. Note that the same parts shown inFIG. 29as those shown inFIG. 18are denoted by the same references, so that detailed description thereof will be omitted.

The ion generating device shown inFIG. 29adopts a method of feeding back a voltage value at the primary side of the boosting portion that generates the high voltage as an output voltage of the high voltage generating circuit, so that the output voltage of the high voltage generating circuit is maintained at a constant value.

The ion generating device shown inFIG. 29includes the ion generating element21having the discharging portion and a high voltage generating circuit600for applying high voltage to the discharging portion. The high voltage generating circuit600includes a trigger coil40that is the boosting portion for boosting the DC voltage delivered from the DC power supply26so as to deliver the high voltage to the discharging portion connected to the secondary side, the bipolar transistor TR1that is the switching element for turning on and off current flowing at the primary side of the trigger coil40, the processing unit24′ having the pulse signal generating portion24B for generating a pulse signal for controlling on and off of the bipolar transistor TR1, the timer24A for adjusting the pulse width and the pulse interval of the pulse signal, the reference voltage circuit24C for delivering the reference voltage VREF, and the voltage comparing portion24D for comparing the feedback voltage VFBwith the reference voltage VREF, and a peak hold circuit41having a diode D13for rectifying the node voltage at the primary side of the trigger coil40and the bipolar transistor TR1, resistors R15and R16for dividing the voltage rectified by the diode D13, and a capacitor C13for smoothing the voltage divided by the resistors TR15and R16so as to generate the feedback voltage VFB. As an example of the processing unit24′, there is a microcomputer for controlling by software the generation of the pulse signal, the adjustment of the pulse width and the pulse interval of the pulse signal, and the voltage comparison between the feedback voltage VFBand the reference voltage VREF, or a customer specific LSI for controlling by hardware the generation of the pulse signal, the adjustment of the pulse width and the pulse interval of the pulse signal, and the voltage comparison between the feedback voltage VFBand the reference voltage VREF.

The positive electrode of the DC power supply25is connected to the power source terminal of the processing unit24′. The positive electrode of the DC power supply26is connected to an end of the primary winding L1of the trigger coil40. The negative electrode of the DC power supply25, the negative electrode of the DC power supply26, and the GND terminal of the processing unit24′ are connected to the ground. The other end of the primary winding L1of the trigger coil40is connected to the collector terminal of the bipolar transistor TR1. The emitter terminal of the bipolar transistor TR1is connected to the ground. The base terminal of the bipolar transistor TR1is connected to the pulse signal output terminal of the processing unit24′. Both ends of the secondary winding L2of the trigger coil40are connected to the discharge electrode and the induction electrode of the discharging portion of the ion generating element21. The collector terminal of the bipolar transistor TR1is connected to the anode terminal of the diode D13. The cathode terminal of the diode D13is connected to an end of the resistor R15. The other end of the resistor R15is connected to an end of the resistor R16, an end of the capacitor C13and the feedback terminal of the processing unit24′. The other end of the resistor R16and the other end of the capacitor C13are connected to the ground. For example, in case of setting the feedback voltage VFBto +1.5 volts when the high voltage generating circuit600supplies the AC impulse high voltage having a peak to peak potential difference of 3 kilovolts to the ion generating element21, an inductance value of the primary winding L1of the trigger coil40is set to 0.256 μH, an inductance value of the secondary winding L2of the trigger coil40is set to 23 mH, a resistance value of the resistor R15is set to 33 kilohms, a resistance value of the resistor R16is set to 180 kilohms, and a capacitance value of the capacitor C13is set to 4.7 nF for setting circuit element constants as an example.

Next, an operation of the ion generating device shown inFIG. 29will be described. As for the ion generating device shown inFIG. 29, when the pulse signal delivered from the processing unit24′ turns on the bipolar transistor TR1so that current flows in the primary winding L1of the trigger coil40, the mutual induction causes generation of the high voltage determined by the turns ratio at the secondary winding L2of the trigger coil40, and the high voltage is applied between the discharge electrode and the induction electrode of the ion generating element21. At the same time, the collector voltage of the bipolar transistor TR1is rectified by the diode D13and then divided by the resistor R15and the resistor R16. The divided voltage is smoothed by the capacitor C13and is converted into the feedback voltage VFB. The feedback voltage VFBdelivered from the peak hold circuit41is supplied to the feedback input terminal of the processing unit24′. Then, the voltage comparing portion24D in the processing unit24′ compares the feedback voltage VFBwith the reference voltage VREF. If the feedback voltage VFBis always below the reference voltage VREFduring a predetermined period, i.e., if the output voltage of the high voltage generating circuit600drops, the timer24A changes setting so that only the pulse width is increased without changing the pulse interval of the pulse signal delivered from the processing unit24′. Thus, if the output voltage of the high voltage generating circuit600drops, the pulse width of the pulse signal delivered from the processing unit24′ increases so that the output voltage of the high voltage generating circuit600increases. Therefore, the output voltage of the high voltage generating circuit600can be maintained at a constant value.

After that, until the next pulse signal is delivered at an interval controlled by the timer24A of the processing unit24′, the bipolar transistor TR1is turned off, so the high voltage is not applied to the discharge electrode of the discharging portion of the ion generating element21. The operation for generating the high voltage is repeated in accordance with the pulse signal delivered at the interval controlled by the timer24A of the processing unit24′.

An operation of the peak hold circuit41will be described with reference toFIGS. 30A to 30C.FIGS. 30A to 30Care diagrams showing voltage and current waveforms at individual portions of the peak hold circuit41. The voltage E7shown inFIG. 30Ais an input voltage of the peak hold circuit41. The current ID13shown inFIG. 30Bis current flowing in the diode D13, and the voltage E8shown inFIG. 30Cis an output voltage of the peak hold circuit41. When the input voltage E7of the peak hold circuit41exceeds the output voltage E8of the peak hold circuit41by a forward voltage VF of the diode D13, the current flows in the diode D13. In other words, the diode D13is turned on when the input voltage E7of the peak hold circuit41exceeds the output voltage E8of the peak hold circuit41by a forward voltage VF of the diode D13. Since the capacitor C13is charged, the period in which the diode D13is turned on becomes short. The period in which the diode D13is turned on is the period for charging the capacitor C13, and the period in which the diode D13is turned off is the period for discharging the capacitor C13. As a result, the input voltage E7of the peak hold circuit4l becomes a DC signal having a ripple like the output voltage E8of the peak hold circuit4l. The time that is necessary for the output voltage E8of the peak hold circuit41to reach the peak voltage E8PEAK depends on a capacitance value of the capacitor C13. Note that “E8PEAK={R15/(R15+R16)}×(E7PEAK−VF)” holds. However, “R15” represents a resistance value of the resistor R15, “R16” represents a resistance value of the resistor R16, and “E7PEAK” represents a peak voltage of the input voltage E7of the peak hold circuit4l.

Voltages at individual portions of the ion generating device shown inFIG. 29have waveforms shown inFIGS. 31A to 31E. Here,FIG. 31Ashows a waveform of the voltage that is applied to the trigger coil40from the DC power supply26, i.e., a waveform of the input voltage of the trigger coil40,FIG. 31Bshows a waveform of the pulse signal delivered from the processing unit24′, i.e., a waveform of the base signal of the bipolar transistor TR1,FIG. 31Cshows a waveform of the output potential difference on the secondary side of the trigger coil40,FIG. 31Dshows a waveform of the collector signal of the bipolar transistor TR1, andFIG. 31Eshows a waveform of the feedback voltage VFBdelivered from the peak hold circuit41and a waveform of the reference voltage VREFdelivered from the reference voltage circuit24C in the processing unit24′.

FIGS. 32A to 32Eshow voltage waveforms at individual portions of the ion generating device shown inFIG. 29, indicating the state in which the feedback circuit (including the peak hold circuit41, the reference voltage circuit24C, and the voltage comparing portion24D) works for maintaining the output voltage of the high voltage generating circuit600when the output voltage of the high voltage generating circuit600drops in accordance with an influence of increase of capacitance in the discharging portion of the ion generating element21.FIG. 32Ashows a waveform of the voltage that is applied to the trigger coil40from the DC power supply26, i.e., a waveform of the input voltage of the trigger coil40,FIG. 32Bshows a waveform of the pulse signal delivered from the processing unit24′, i.e., a waveform of the base signal of the bipolar transistor TR1,FIG. 32Cshows a waveform of the output potential difference on the secondary side of the trigger coil40,FIG. 32Dshows a waveform of the collector signal of the bipolar transistor TR1, andFIG. 32Eshows a waveform of the feedback voltage VFBdelivered from the peak hold circuit41and a waveform of the reference voltage VREFdelivered from the reference voltage circuit24C in the processing unit24′.

The timer24A sets the pulse width at the next pulse interval in accordance with an output voltage level of the voltage comparing portion24D at each pulse interval. In the first pulse interval T1, there is a period in which the output voltage of the voltage comparing portion24D has a high level (seeFIG. 32E), so the timer24A sets the pulse width at the second pulse interval T2to 0.5 μsec (a standard value). In the second pulse interval T2, increase of capacitance in the discharging portion of the ion generating element causes a drop of the output potential difference of the high voltage generating circuit600(seeFIG. 32C), so that the feedback voltage VFBis always below the reference voltage VREF, and that there is no period in which the output voltage of the voltage comparing portion24D has a high level (seeFIG. 32E). Therefore, the timer24A sets the pulse width at the third pulse interval T3to 1.0 μsec (seeFIG. 32B). Note that the pulse width values 0.5 μsec and 1.0 μsec are examples.

Note that it is possible to adopt the structure for increasing the DC voltage supplied to the boosting portion so that the high voltage delivered from the secondary side of the boosting portion can be maintained at a constant value as to the ion generating device adopting the method of feeding back the voltage on the primary side of the boosting portion that generates the high voltage as the output voltage of the high voltage generating circuit so that the output voltage of the high voltage generating circuit can be maintained at a constant value. For example, it is possible to maintain the high voltage delivered from the secondary side of the boosting portion when the DC voltage supplied to the boosting portion is raised by adding the same modification to the ion generating device shown inFIG. 29as the modification fromFIG. 18toFIG. 25.

In addition, as to the ion generating device shown inFIG. 18,22or29, it is possible to increase further the pulse width of the pulse signal delivered from processing unit24′ if the feedback voltage VFBis always below the reference voltage VREFduring a predetermined period, i.e., if the output voltage of the high voltage generating circuit drops after the pulse width of the pulse signal delivered from the processing unit24′ is increased. In this case, it is desirable to set an upper limit to the pulse width of the pulse signal delivered from the processing unit24′ and to provide in the processing unit24′ an error output portion that produces an error output when the pulse width of the pulse signal delivered from the processing unit24′ reaches the upper limit. Thus, since a user can recognize from the error output that a capacitance value of the discharging portion has increased, it is possible to maintain the discharging portion. As setting of the pulse width, for example, the standard value is set to 0.5 μsec, the pulse width is increased every 0.5 μsec, and the upper limit is set to 2.0 μsec.

In addition, as to the ion generating device shown inFIG. 25, it is possible to increase further the number of pulses per a predetermined time of the control signal for controlling the switching transistor of the booster switching regulator39if the feedback voltage VFBis always below the reference voltage VREFduring a predetermined period, i.e., if the output voltage of the high voltage generating circuit drops after the number of pulses per a predetermined time of the control signal for controlling the switching transistor of the booster switching regulator39is increased. In this case, it is desirable to set an upper limit to the number of pulses per a predetermined time of the control signal for controlling the switching transistor of the booster switching regulator39and to provide in the processing unit24″ an error output portion that produces an error output when the number of pulses per a predetermined time of the control signal for controlling the switching transistor of the booster switching regulator39reaches the upper limit. Thus, since the user can recognize from the error output that a capacitance value of the discharging portion has increased, it is possible to maintain the discharging portion. As the number of pulses per a predetermined time, for example, the standard value is set to three so that the increase is performed every three pulses, and the upper limit is set to twelve.

In addition, as to the ion generating device shown inFIGS. 18,22,25and29, it is possible to adopt the structure in which a switch is provided between the voltage comparing portion24D and the power source terminal of the processing unit, and the switch is turned on and off so that the voltage comparing portion works when the power is turned on or only at a constant interval of time. Thus, power consumption in the voltage comparing portion24D can be controlled.

In addition, the embodiments described above can be combined as necessity.

The ion generating device according to the present invention is preferably incorporated in an electrical apparatus such as an air conditioner, a dehumidifier, a humidifier, an air cleaner, a refrigerator, a fan heater, a microwave oven, a washing machine with a dryer, a cleaner and a pasteurizer. Furthermore, an electrical apparatus700is preferably equipped with a delivery portion (e.g., an air blower fan900) for delivering into the air the ion generated by an ion generating device800according to the present invention as shown inFIG. 33. This electrical apparatus can perform, adding to its essential function, the function of suppressing activity and growth of molds and germs in the air by the action of the plus ions and minus ions delivered from the incorporated ion generating device, so that the room environment can be desirable ambient air conditions.