Patent ID: 12224677

DESCRIPTION OF EMBODIMENTS

Embodiment 1

Embodiment 1 relates to a power source device including a capacitive load; and an AC power source, as a voltage source, which applies AC voltage to the capacitive load. The power source device has a configuration in which a series circuit composed of a first inductor and a first capacitor is connected to the AC power source; a series circuit composed of a load inductor and the capacitive load is connected in parallel to one of the first inductor or the first capacitor; a resonance frequency of the first inductor and the first capacitor and a resonance frequency of the load inductor and the capacitive load are matched with each other; and a frequency of the AC power source is matched with each of the resonance frequencies.

In embodiment 1, descriptions are given also regarding a case where an inductive load is driven and a case where multiple stages of resonance circuits are formed.

Hereinafter, configurations and operations of the power source device according to embodiment 1 will be described with reference toFIG.1toFIG.3which are each a configuration diagram of a power source device in which the capacitive load is driven by the AC voltage source and a series resonance circuit;FIG.4which is a configuration diagram of a power source device in which two capacitive loads are driven; andFIG.5which is a configuration diagram of a power source device in which the capacitive load is driven by the AC voltage source and multiple stages of series resonance circuits.

A basic configuration of a power source device100according to embodiment 1 will be described with reference toFIG.1. In addition, modifications of the power source device100inFIG.1which is a basic configuration diagram thereof will be described with appropriate reference toFIG.2andFIG.3.

The power source device100includes an AC power source1; a capacitive load2; a load inductor5which forms a resonance circuit together with the capacitive load2; and furthermore, an inductor6and a capacitor7which are used for amplifying the quality factor of the resonance circuit. Here, the inductor6and the capacitor7are a first inductor and a first capacitor in the claims.

It is noted that the quality factor of the resonance circuit will be described later.

In embodiment 1, the AC power source1is a voltage-type AC power source, that is, an AC voltage source. The voltage-type AC power source and a current-type AC power source will be described later.

The capacitive load2corresponds to, for example, an ozonizer and a barrier discharge lamp. The capacitive load2is a load to be driven by the AC power source1. An equivalent circuit of the capacitive load2is expressed with an equivalent capacitor3as a capacitive component; and an equivalent resistor4as a resistance component.

Although the equivalent capacitor3and the equivalent resistor4are expressed as being in series to each other inFIG.1, there is also a case where it is more appropriate to express the equivalent capacitor3and the equivalent resistor4as being in parallel to each other as inFIG.2, for example. In addition, there is also a case where both a resistance component that is in series to the equivalent capacitor3and a resistance component that is in parallel to the equivalent capacitor3exist.

It is noted that the power source device inFIG.2is shown as a power source device101to be distinguished from the power source device100inFIG.1.

These cases slightly differ from one another in terms of circuits but do not significantly differ from one another in terms of the manner of handling. Thus, descriptions will be given while the equivalent capacitor3and the equivalent resistor4of the capacitive load2are expressed as being connected in series to each other as inFIG.1.

Here, an equivalent capacitance of the equivalent capacitor3is defined as Cs, and a resistance value of the equivalent resistor4is defined as RL.

The equivalent capacitance Cs and the equivalent resistance value RL are determined according to a physical operation of the capacitive load2and, in general, fluctuate over time. However, if the equivalent capacitance Cs and the equivalent resistance value RL are treated as in circuits, the average values thereof can be used.

For example, as described in Patent Document 1, the equivalent capacitance Cs or the equivalent resistance value RL defined here are such equivalent average values.

In a case where the capacitive load2is driven with series resonance, an inductor is provided in series thereto. The load inductor5inFIG.1is the inductor for series resonance. Here, an inductance of the load inductor5is defined as Ls.

In addition thereto, the inductor6and the capacitor7are connected in series to the AC power source1as inFIG.1in the present disclosure. Here, an inductance of the inductor6is defined as Lp, and a capacitance of the capacitor7is defined as Cp.

A circuit including the capacitive load2and further including the inductor6(inductance Lp), the capacitor7(capacitance Cp), and the load inductor5(inductance Ls) which form resonance circuits of the present disclosure, is described as a load circuit21in the sense of a load as seen from the AC power source1.

It is noted thatFIG.2and the subsequent drawings for embodiment 1 do not show any circuit corresponding to the load circuit21.

An operational characteristic of the load circuit21is that two stages of resonance circuits are present.

Specifically, a first stage of resonance circuit is formed by the inductor6and the capacitor7connected in series to the AC power source1. A second stage of resonance circuit is formed by a series circuit that is composed of the capacitive load2and the load inductor5and that is connected in parallel to the capacitor7.

Descriptions will be given regarding a case where both a resonance frequency of the first stage of resonance circuit (the series circuit composed of the inductor6and the capacitor7) and a resonance frequency of the second stage of resonance circuit (the series circuit composed of the capacitive load2and the load inductor5; are matched with a frequency fv of the AC power source1, that is, a case where expression (1) is satisfied. It is noted that the frequency of the AC power source1is defined as fv.
Ls·Cs=Lp·Cp=1/((2π·fv){circumflex over ( )}2)  (1)

An impedance of the load inductor5and an impedance of the equivalent capacitor3of the capacitive load2are canceled out, and thus the only apparent impedance of the series circuit composed of the load inductor5, the equivalent resistor4, and the equivalent capacitor3is the equivalent resistance value RL of the equivalent resistor4.

The circuit in this case is equivalent to a circuit in which the inductor6and the capacitor7are connected in series to the AC power source1; and the equivalent resistor4is connected in parallel to the capacitor7.

It is further known from expression (1) that the inductor6and the capacitor7also satisfy a resonance condition, and thus only the equivalent resistor4is apparent from the AC power source1.

That is, the power factor of the AC power source1becomes 1, and the most efficient drive can be performed.

This load circuit21is characterized in that the boost ratio thereof can be freely designed. This characteristic will be described.

Here, a case where a series resonance circuit composed of an ordinary inductor (an inductance thereof is defined as L), an ordinary capacitor (a capacitance thereof is defined as C), and an ordinary resistor (a resistance value thereof is defined as R) is driven at a resonance frequency f0(angular frequency ω0), will be contemplated first. The relationship thereamong is expressed with expression (2).
ω0=2π·f0=1/(√(L·C))  (2)

The quality factor of the series resonance circuit is expressed with expression (3).
Q=(1/R)·(√(L/C))=(ω0·L)/R=1/(ω0·C·R)  (3)

Here, the capacitive load2is a part to be driven, and the equivalent circuit constants thereof, that is, the equivalent capacitance Cs of the equivalent capacitor3and the equivalent resistance value RL of the equivalent resistor4, cannot be changed. Meanwhile, the frequency of the AC power source1can be slightly adjusted but cannot be significantly changed since this frequency significantly influences the performance of the capacitive load2.

Therefore, the quality factor of the resonance circuit composed of the capacitive load2and the load inductor5is uniquely determined according to expression (3). The quality factor is the maximum value of the boost ratio, that is, the ratio of the voltage of the capacitive load2(here, the voltage to be applied to the equivalent capacitor3) to the power source voltage.

If the frequency of the AC power source1is changed from the resonance frequency f0, the boost ratio becomes lower than the quality factor in expression (3). That is, if the frequency of the AC power source1is determined on the basis of an operation condition of the capacitive load2, the quality factor of the resonance circuit composed of the capacitive load2and the load inductor5is uniquely determined, resulting in determination of the extent to which boosting can be performed by this resonance circuit.

Meanwhile, in the case of a circuit configuration such as one inFIG.1, addition of the inductor6and the capacitor7makes it possible to freely design the boost ratio.

Specifically, if load conditions (the capacitance Cs of the equivalent capacitor3and the equivalent resistance value RL of the equivalent resistor4) and a drive condition (the frequency of the AC power source1) are determined, the value of the inductance Ls of the load inductor5is determined according to expression (1) in a resonance condition. Therefore, the quality factor of the resonance circuit composed of the capacitive load2and the load inductor5cannot be changed.

However, the inductance Lp of the inductor6and the capacitance Cp of the capacitor7can be freely determined as long as expression (1) is satisfied.

The ratio of the voltage to be applied to the capacitive load2, that is, the boost ratio, is a product of the boost ratio of the first stage of resonance circuit (the resonance circuit composed of the inductor6and the capacitor7) and the boost ratio of the second stage of resonance circuit (the resonance circuit composed of the capacitive load2and the load inductor5). Thus, the voltage to be applied to the capacitive load2can be freely designed.

In the circuit inFIG.1, the inductor6and the capacitor7in the first stage play equivalent roles under the resonance condition, and thus may be exchanged to obtain a configuration such as one inFIG.3.

It is noted that the power source device inFIG.3is shown as a power source device102to be distinguished from the power source device100inFIG.1.

The configuration inFIG.3is suitable for a case where the potential on a high-voltage side (the high-voltage side of the capacitive load2) is desired to be assuredly set to zero when the power source is stopped. In order to express this, in particular, a GND potential is shown inFIG.3.

Next, a case where two capacitive loads are simultaneously driven by the single AC power source will be described with reference toFIG.4. Here, the power source device inFIG.4is shown as a power source device103to be distinguished from the power source device100inFIG.1.

The power source device103includes the AC power source1; two capacitive loads2aand2b; load inductors5aand5bwhich form resonance circuits together with the respective capacitive loads2aand2b; and furthermore, the inductor6and the capacitor7which are used for amplifying the quality factors of the resonance circuits.

The capacitive load2aincludes an equivalent capacitor3aand an equivalent resistor4a. The capacitive load2bincludes an equivalent capacitor3band an equivalent resistor4b.

Here, the capacitive load2band the load inductor5bare a second capacitive load and a second load inductor in the claims.

InFIG.4, there is a characteristic that the two capacitive loads2aand2bcan be simultaneously driven by the single AC power source1. The capacitive load2aand the capacitive load2bmay be identical to or different from each other.

If circuit constants differ from each other, it is necessary to design the respective load inductors5aand5bfor resonances so as to individually satisfy expression (1). The equivalent resistors of the capacitive load2aand the capacitive load2bmay have different resistance values.)

In the same manner as in the power source device100to the power source device102described above, GND may be located anywhere in the power source device103as well. However, since there are the plurality of capacitive loads2aand2b, it is general to locate GND at a connection point between the capacitive load2aand the capacitive load2bas shown inFIG.4.

If the equivalent capacitances of the capacitive load2aand the capacitive load2bare equal to each other and the values of the load inductor5aand the load inductor5bare equal to each other, a common inductor may be provided to simplify the circuit.

Specifically, if a common inductor is provided on a path extending from a connection point between the inductor6and the capacitor7to the connection point between the capacitive load2aand the capacitive load2b, the load inductor5aand the load inductor5bcan be replaced with one common inductor. As a result, downsizing and cost reduction can be achieved.

However, if the connection point between the capacitive load2aand the capacitive load2bis at a GND potential as shown inFIG.4, this configuration causes fluctuation, at high voltage, of the potential of the connection point between the inductor6and the capacitor7and the potential of the AC power source1.

Next, a power source device in which multiple stages of resonance circuits composed of inductors and capacitors are used will be described with reference toFIG.5. Here, the power source device inFIG.5is shown as a power source device104to be distinguished from the power source device100inFIG.1.

Unlike in the power source device100inFIG.1in which two stages of LC resonance circuits are present, a configuration in which three or more stages of LC resonance circuits are present can also be employed.

The power source device104includes the AC power source1; the capacitive load2; the load inductor5which forms a resonance circuit together with the capacitive load2; and furthermore, a first inductor L1and a first capacitor C1, . . . , an (n−1)-th inductor Ln−1 and an (n−1)-th capacitor Cn−1, and an n-th inductor In and an n-th capacitor Cn which are used for amplifying the quality factor of the resonance circuit, where “n” is an integer not smaller than 2.

Here, the first inductor L1and the first capacitor C1form a first resonance circuit, . . . , the (n−1)-th inductor Ln−1 and the (n−1)-th capacitor Cn−1 form an (n−1)-th resonance circuit, and the n-th inductor In and the n-th capacitor Cn form an n-th resonance circuit.

It is noted that the first inductor is denoted by L1and the first capacitor is denoted by C1in order to form multiple stages and generalize descriptions.

If the resonance frequency of each stage of LC resonance circuit is adjusted so as to satisfy expression (1), the advantageous effect of further increasing the boost ratio in the power source device100described with reference toFIG.1can be obtained.

InFIG.5, for example, a series circuit composed of a second inductor12and a second capacitor C2is connected in parallel to the first capacitor C1out of the first inductor L1and the first capacitor C1connected to form a series circuit. However, the same advantageous effect can be obtained also by connecting the series circuit composed of the second inductor L2and the second capacitor C2in parallel to the first inductor L1as described with reference toFIG.1andFIG.3.

As described above, the power source device according to embodiment 1 includes a capacitive load; and an AC power source, as a voltage source, which applies AC voltage to the capacitive load. The power source device has a configuration in which a series circuit composed of a first inductor and a first capacitor is connected to the AC power source; a series circuit composed of a load inductor and the capacitive load is connected in parallel to one of the first inductor or the first capacitor; a resonance frequency of the first inductor and the first capacitor and a resonance frequency of the load inductor and the capacitive load are matched with each other; and a frequency of the AC power source is matched with each of the resonance frequencies. Therefore, in the power source device according to embodiment 1, the quality factor of the resonance circuit can be freely designed, and the boost ratio can be increased so that high voltage for driving the capacitive load can be generated without using any transformer.

Embodiment 2

In a power source device according to embodiment 2, an inductive load is driven by the AC voltage source.

The power source device according to embodiment 2 will be described focusing on differences from that according to embodiment 1 with reference toFIG.6which is a configuration diagram of a power source device in which an inductive load is driven by the AC voltage source and the series resonance circuit.

InFIG.6for embodiment 2, portions identical or corresponding to those in embodiment 1 are denoted by the same reference characters.

It is noted that the present power source device is shown as a power source device200to be distinguished from that according to embodiment 1.

In embodiment 1, drive of the capacitive load such as an ozonizer and a barrier discharge-utilizing lamp has been described.

In embodiment 2, capability to use the basic configuration of the power source device100according to embodiment 1 also for driving an inductive load will be described.

Here, the inductive load refers to a load including a strong inductive component as an electric property, and a representative example thereof is, for example, an induction heating (IH) coil for an IH cooking heater or the like.

The power source device200includes the AC power source1as an AC voltage source; an inductive load8; a load capacitor11which forms a resonance circuit together with the inductive load8; and furthermore, the inductor6and the capacitor7which are used for amplifying the quality factor of the resonance circuit.

The inductive load8is a load to be driven by the AC power source1. An equivalent circuit of the inductive load8is expressed with an equivalent inductor9as an inductive component; and an equivalent resistor10as a resistance component.

InFIG.6, the equivalent circuit of the inductive load8is expressed with series connection between the equivalent inductor9and the equivalent resistor10. However, as described in embodiment 1, there are cases where, depending on the inductive load, it is more appropriate to express the equivalent circuit with parallel connection between the equivalent inductor and the equivalent resistor; or both an equivalent resistor that is in series to the equivalent inductor and an equivalent resistor that is in parallel to the equivalent inductor.

These cases slightly differ from one another in terms of circuits but do not significantly differ from one another in terms of the manner of handling. Thus, descriptions will be given while the inductive load8is expressed with series connection between the equivalent inductor9and the equivalent resistor10as inFIG.6.

Here, an inductance of the equivalent inductor9is defined as Ls, and a capacitance of the load capacitor is defined as Cs.

As is known fromFIG.6, the AC power source1as a voltage source, the capacitor7(the capacitance thereof is defined as Cp), and the inductor6(the inductance thereof is defined as Lp) are the same as those inFIG.1for embodiment 1. A series circuit composed of the load capacitor11(the capacitance thereof is defined as Cs) and the inductive load8is connected in parallel to the capacitor7.

As is obvious by expressing with the equivalent circuits, the circuit inFIG.6is completely identical to that inFIG.1for embodiment 1, and the same advantageous effect can be expected.

In the case where the frequency of the AC power source1is defined as fv, high voltage can be applied across the inductive load8if circuit constants (i.e., the equivalent inductance Is of the equivalent inductor9, the capacitance Cs of the load capacitor11, the inductance Lp of the inductor6, and the capacitance Cp of the capacitor7) are set so as to satisfy expression (1).

Specifically, high voltage can be applied across the inductive load8if the series circuit composed of the inductor6and the capacitor7is connected to the AC power source1; a series circuit composed of the load capacitor11and the inductive load8is connected in parallel to one of the inductor6or the capacitor7; the resonance frequency of the inductor6and the capacitor7and a resonance frequency of the load capacitor11and the inductive load8are matched with each other; and the frequency fv of the AC power source is matched with each of the resonance frequencies.

A configuration (not shown), such as one shown inFIG.2toFIG.4for embodiment 1, that conforms to the configuration inFIG.6can also be realized in the same manner.

That is, if the series resonance circuit composed of the capacitor7and the inductor6is added, a voltage higher than a voltage capable of being realized with ordinary series resonance of the inductive load8and the load capacitor11can be applied to the inductive load8by the AC voltage source.

Embodiment 3

In a power source device according to embodiment 3, the inductive load is driven by an AC current source.

The power source device according to embodiment 3 will be described focusing on differences from that according to embodiment 1 with reference toFIG.7toFIG.9which are each a configuration diagram of a power source device in which the inductive load is driven by an AC current source and a parallel resonance circuit;FIG.10which is a configuration diagram of a power source device in which two inductive loads are driven; andFIG.11which is a configuration diagram of a power source device in which the capacitive load is driven by the AC current source and the parallel resonance circuit,

InFIG.7toFIG.11for embodiment 3, portions identical or corresponding to those in embodiment 1 are denoted by the same reference characters.

It is noted that the present power source device is shown as a power source device300to be distinguished from that according to embodiment 1.

In embodiment 2, an example has been described in which the AC power source as a voltage source is used for the purpose of applying, to the inductive load, a voltage higher than that in ordinary series resonance.

However, in general, an inductive load is an inductor, that is, a coil, and thus is frequently used for allowing high current to flow therethrough instead of allowing high voltage to be applied thereto. As a circuit that does not perform “boosting” for high voltage but “amplifies” high current, a parallel resonance circuit is more suitable than a series resonance circuit.

In parallel resonance, with an inductor and a capacitor being connected in parallel to an AC current source, even when current from the AC power source is very low, current of each of the inductor and the capacitor is significantly amplified by the resonance. Consequently, high current can be caused to flow through the inductor or the capacitor.

A basic configuration of the power source device300according to embodiment 3 will be described with reference toFIG.7. In addition, modifications of the power source device300inFIG.7which is a basic configuration diagram thereof will be described with appropriate reference toFIG.8andFIG.9.

The power source device300includes an AC power source12as an AC current source; the inductive load8; the load capacitor11which forms a resonance circuit together with the inductive load8; and furthermore, the inductor6and the capacitor7which are used for amplifying the quality factor of the resonance circuit.

InFIG.7, the inductive load8is expressed as a series circuit composed of the equivalent inductor9and the equivalent resistor10. However, there is also a case where it is more appropriate to express the inductive load8as a parallel circuit composed of the equivalent inductor9and the equivalent resistor10as inFIG.8.

It is noted that the power source device inFIG.8is shown as a power source device301to be distinguished from the power source device300inFIG.7.

Here, the inductance of the equivalent inductor9is defined as Ls, and a resistance value of the equivalent resistor10is defined as RL. The equivalent inductance Ls and the equivalent resistance value RL are determined according to a physical operation of the inductive load8and, in general, fluctuate over time. However, if the equivalent inductance Ls and the equivalent resistance value RL are treated as in circuits, the average values thereof can be used.

In the same manner as in embodiment 1, the equivalent inductance Ls or the equivalent resistance value RL defined here are such equivalent average values.

In the case where the inductive load8is driven with parallel resonance, a capacitor is provided in parallel thereto. The load capacitor11inFIG.7is the capacitor for parallel resonance. Here, the capacitance of the load capacitor11is defined as Cs.

In addition thereto, the capacitor7and the inductor6are connected in parallel to the AC power source12as inFIG.7in the present disclosure. Here, the capacitance of the capacitor7is Cp, and the inductance of the inductor6is Lp.

A circuit including the inductive load8and further including the capacitor7(capacitance Cp), the inductor6(inductance Lp), and the load capacitor11(capacitance Cs) which form the resonance circuits of the present disclosure, is described as a load circuit321in the sense of a load as seen from the AC power source12,

It is noted thatFIG.8and the subsequent drawings for embodiment 3 do not show any circuit corresponding to the load circuit321.

An operational characteristic of the load circuit321is that two stages of resonance circuits are present,

Specifically, the capacitor7and the inductor6connected in parallel to the AC power source12form a first stage of resonance circuit. A parallel circuit composed of the inductive load8and the load capacitor11, connected in series to the inductor6is formed as a second stage of resonance circuit.

If both the resonance frequencies of the first stage of resonance circuit and the second stage of resonance circuit are matched with the frequency fv of the AC power source12so as to satisfy expression (1), high current can be caused to flow through the inductive load8according to the same principle as that described in embodiment 1.

Specifically, current having been caused to flow by the AC power source12as an AC current source is first resonated by the first stage of resonance circuit composed of the inductor6and the capacitor7and is further resonated by the second stage of resonance circuit composed of the load capacitor11and the inductive load8, whereby high current can be caused to flow through the inductive load8.

This load circuit321is characterized in that the current amplification ratio thereof can be freely designed. Descriptions regarding this characteristic are the same as those in embodiment 1, and thus will be omitted.

In the circuit inFIG.7, the inductor6and the capacitor7in the first stage play equivalent roles under the resonance condition, and thus may be exchanged to obtain a configuration such as one inFIG.9.

It is noted that the power source device inFIG.9is shown as a power source device302to be distinguished from the power source device300inFIG.7,

The parallel circuit composed of the inductor6and the capacitor7is connected to the AC power source12, the parallel circuit composed of the load capacitor11and the inductive load8is connected in series to one of the inductor6or the capacitor7, the resonance frequency of the inductor6and the capacitor7and the resonance frequency of the load capacitor11and the inductive load8are matched with each other, and the frequency fv of the AC power source12is matched with each of the resonance frequencies. Consequently, the quality factor of the resonance circuit can be freely designed, and the current amplification ratio can be increased so that high current for driving the inductive load can be generated without using any transformer.

Next, a case where two inductive loads are simultaneously driven by the single AC power source will be described with reference toFIG.10, Here, the power source device inFIG.10is shown as a power source device303to be distinguished from the power source device300inFIG.7.

The power source device303includes the AC power source12; two inductive loads8aand8b; load capacitors11aand11bwhich form resonance circuits together with the respective inductive loads8aand8b; and furthermore, the inductor6and the capacitor7which are used for amplifying the quality factors of the resonance circuits.

The inductive load8aincludes an equivalent inductor9aand an equivalent resistor10a. The inductive load8bincludes an equivalent inductor9band an equivalent resistor10b.

Here, the inductive load8band the load capacitor11are a first inductive load and a second load capacitor in the claims.

InFIG.10, there is a characteristic that the two inductive loads8aand8bcan be simultaneously driven by the single AC power source12. The inductive load8aand the inductive load8bmay be identical to or different from each other. However, the resonance condition, that is, expression (1), needs to be kept satisfied in each resonance circuit.

The capacitive load described in embodiment 1 can also be driven by using the parallel-resonance-type circuit. A configuration example of a power source device in which the capacitive load is driven by using the parallel resonance circuit is shown inFIG.11.

Here, the power source device inFIG.11is shown as a power source device304to be distinguished from the power source device300inFIG.7.

In the power source device304, the inductor6and the capacitor7form a first stage of parallel resonance circuit, and the capacitive load2and the load inductor5form a second stage of parallel resonance circuit.

That is, in the power source device304, the capacitive load2is driven by the AC power source12as an AC current source with use of the parallel resonance circuit composed of the inductor6and the capacitor7.

That is, a configuration is employed in which the parallel circuit composed of the inductor6and the capacitor7is connected to the AC power source12; a parallel circuit composed of the load inductor5and the capacitive load2is connected in series to one of the inductor6or the capacitor7; the resonance frequency of the inductor6and the capacitor7and the resonance frequency of the load inductor5and the capacitive load2are matched with each other; and the frequency of the AC power source is matched with each of the resonance frequencies. Consequently, by using the AC current source, the quality factor of the resonance circuit can be freely designed, and the current amplification ratio can be increased so that high current for driving the capacitive load can be generated without using any transformer.

Alternatively, it is also possible to employ a configuration in which the two capacitive loads are simultaneously driven in the same manner as in the power source device303inFIG.10, with the power source device304inFIG.11being a base.

As described above, in the power source device according to embodiment 3, the inductive load is driven by the AC current source,

Therefore, in the power source device according to embodiment 3, by using the AC power source as a current source, the quality factor of the resonance circuit can be freely designed, and the current amplification ratio can be increased so that high current for driving the inductive load can be generated without using any transformer.

Embodiment 4

In embodiment 4, specific configuration examples of the AC voltage source described in embodiment 1 and the AC current source described in embodiment 3 will be described.

A power source device according to embodiment 4 will be described with reference toFIG.12which is a configuration diagram of a power source device in which an AC voltage source is formed by using IGBTs;FIG.13which is a configuration diagram of a power source device in which an AC voltage source is formed by using MOSFETS;FIG.14which is a configuration diagram of a power source device in which an AC current source is formed by using thyristors; andFIG.15which is a configuration diagram of a power source device in which an AC current source is formed by using IGBTs.

In the configuration diagrams for embodiment 4, portions identical or corresponding to those in embodiments 1 and 3 are denoted by the same reference characters.

Firstly, the AC voltage source will be described.

A voltage source refers to a power source designed to control the voltage value of an output to a certain value, and is ideally a power source that, no matter how much the current increases, has a non-fluctuating output voltage, that is, has an internal impedance of zero.

Although a power source having an internal impedance of zero does not exist in actuality, power sources are designed in consideration of this characteristic. An AC voltage source refers to a voltage source in which the value of the voltage thereof is caused to fluctuate at a certain frequency.

A power source device400in which an AC voltage source is formed by using IGBTs will be described with reference toFIG.12.

The power source device400includes an AC voltage source1A; a control circuit13which controls an inverter unit of the AC voltage source1A; and the load circuit21.

The AC voltage source1A includes a constant voltage source14; a capacitor15for stabilizing the output voltage of the constant voltage source14; and a full-bridge inverter30formed by four IGBTs as elements.

Here, the AC voltage source LA corresponds to the AC power source1inFIG.1for embodiment 1.

The control circuit13controls switching of each of the IGBTs so as to obtain an AC waveform having a predetermined frequency. The IGBT is a voltage-type element, and a voltage waveform determined according to the constant voltage source14and the switching waveform is outputted from the full-bridge inverter30. That is, the AC voltage source1A functions as a voltage-type inverter.

The load circuit21includes the capacitive load2composed of the equivalent capacitor3and the equivalent resistor4; the load inductor5; the capacitor7; and the inductor6. The load circuit21has already been described in embodiment 1, and thus will not be described here.

Next, a power source device401in which an AC voltage source is formed by using MOSFETs will be described with reference toFIG.13. It is noted that the power source device inFIG.13is shown as the power source device401to be distinguished from the power source device400inFIG.12.

The power source device401includes an AC voltage source18; the control circuit13which controls an inverter unit of the AC voltage source1B; and the load circuit21.

The AC voltage source18includes the constant voltage source14; the capacitor15for stabilizing the output voltage of the constant voltage source14; and a half-bridge inverter31formed by two MOSFETs as elements.

Here, the AC voltage source18corresponds to the AC power source1inFIG.1for embodiment 1.

The control circuit13controls switching of each of the MOSFETs so as to obtain an AC waveform having a predetermined frequency. The MOSFET is a voltage-type element, and a voltage waveform determined according to the constant voltage source14and the switching waveform is outputted from the half-bridge inverter31. That is, the AC voltage source18functions as a voltage-type inverter.

Next, the AC current source will be described.

A current source refers to a power source designed to control the current value of an output to a certain value, and is ideally a power source that, no matter how high the output voltage becomes, can be kept having a fixed current value, that is, has an internal admittance of zero (infinite impedance).

Although a power source having an infinite impedance does not exist in actuality, power sources are designed in consideration of this characteristic. An AC current source refers to a current source in which the valve of the current thereof is caused to fluctuate at a certain frequency.

A power source device402in which an AC current source is formed by using thyristors will be described with reference toFIG.14. It is noted that the power source device inFIG.14is shown as the power source device402to be distinguished from the power source device400inFIG.12.

The power source device402includes an AC current source12A; the control circuit13which controls an inverter unit of the AC current source12A; and the load circuit321.

The AC current source12A includes a constant current source16; an inductor17for stabilizing the output current of the constant current source16; and a full-bridge inverter32formed by four thyristors as elements.

Here, the AC current source12A corresponds to the AC power source12inFIG.7for embodiment 3.

The control circuit13controls switching of each of the thyristors so as to obtain an AC waveform having a predetermined frequency. The thyristor is a current-type element, and a current waveform determined according to the constant current source16and the switching waveform is outputted from the full-bridge inverter32by causing current to be ON/OFF. That is, the AC current source12A functions as a current-type inverter.)

The load circuit321includes the inductive load8composed of the equivalent inductor9and the equivalent resistor10; the load capacitor11; the capacitor7; and the inductor6. The load circuit321has already been described in embodiment 3, and thus will not be described here.

The current-type inverter is ordinarily formed by thyristors as current switching elements. The current-type inverter can be formed by using, instead of ordinary thyristors, any of gate turn-off thyristors (GTOs), gate commutated turn-off thyristors (GCTs), static induction (SI) thyristors, and MOS gate thyristors,

Recently, voltage-type switching elements such as IGBTs and MOSFETs are generally used, and thus, as inverters as well, voltage-type ones are often used. However, in the case of using a parallel-type resonance circuit, a current-type power source is suitable, and, in the case of using voltage-type switching elements, the voltage-type switching elements are used with a voltage-type inverter being caused to have a characteristic similar to that of a current-type inverter.

A configuration example in this case is shown inFIG.15. It is noted that the power source device inFIG.15is shown as a power source device403to be distinguished from the power source device400inFIG.12.

The power source device403includes an AC current source128; the control circuit13which controls an inverter unit of the AC current source128; and the load circuit321.

The AC current source128includes the constant voltage source14; the capacitor15for stabilizing the output voltage of the constant voltage source14; the full-bridge inverter30formed by four IGBTs as elements; and furthermore, an inductor18for stabilizing the output current of the full-bridge inverter30.

Here, the inductor18has a high inductance value. If this inductor18is provided, the output current of the full-bridge inverter30is stabilized, and a power source impedance as seen from a secondary side of the inductor18becomes high. Consequently, the inverter circuit including the inductor18as well comes to have a characteristic similar to that of an AC current source.

It is noted that the control circuit13and the load circuit321are respectively the same as those described regarding the power source device400and the power source device402, and thus will not be described here.

An actual power source is not an ideal voltage source or an ideal current source, and the internal impedance thereof has a value that is not zero and that is not infinite but finite. The power source is merely designed to be used as a voltage source or a current source, or has a characteristic similar to that of the voltage source and the current source.

In the present disclosure, the “AC voltage source” means a power source that is designed to be used as a voltage source and that has a characteristic comparatively similar to that of the voltage source. Likewise, the “AC current source” means a power source that is designed to be used as a current source and that has a characteristic comparatively similar to that of the current source.

Although only the inverters in which the switching elements are used have been taken as examples in the above descriptions, there are other methods for obtaining AC voltage. For example, a bipolar power source formed by a linear amplifier can be used. In a case where the frequency does not need to be made variable, a commercial frequency can be directly used, or a harmonic can also be used.

Embodiment 5

A power source device according to embodiment 5 is provided with a mechanism that adjusts the inductance of an inductor composing a resonance circuit or the capacitance of a capacitor composing the resonance circuit.

The power source device according to embodiment 5 will be described focusing on differences from embodiment 1 with reference toFIG.16which is a configuration diagram of a power source device provided with an inductance adjustment circuit; andFIG.17which is a configuration diagram of a power source device provided with a capacitance adjustment circuit.

In the configuration diagrams for embodiment 5, parts identical or corresponding to those in embodiment 1 are denoted by the same reference characters.

As described in embodiment 1, the quality factor of the resonance circuit can be freely designed by using the configuration of the power source device according to the present disclosure. That is, the quality factor can be set to a very high value.

However, if the quality factor is high, the width of the frequency for resonance is narrowed. That is, production of a circuit having a high quality factor makes it difficult to achieve resonance circuit matching.

A resonance circuit is composed of a reactor and a capacitor, and, in general, characteristics of these circuit constituents change according to temperature and over time. That is, an inductance value and a capacitance thereof change.

In addition, in general, electric properties of a capacitive load or an inductive load change when operation conditions change.

As is generally known, an average capacitance of a barrier discharge load as a capacitive load changes according to power. Such change in the inductance or the capacitance in a circuit inflicts influence on resonance characteristics of the circuit. In a case where the quality factor is very high and the frequency range in which resonance is possible is very narrow, an off-resonance state might be taken so that the circuit stops operating.

Therefore, in the case of applying the power source device according to the present disclosure, any adjustment mechanism for maintaining resonance of the circuit is desirably present.

In the case of realizing the adjustment mechanism for maintaining resonance of the circuit, there are two problems in terms of means for adjusting resonance; and a control method as to the basis and the manner of the adjustment. They will be sequentially described.

Firstly, the means for adjusting resonance will be described.

The most easily applicable means for adjusting resonance is adjustment based on frequency.

In the power source device according to the present disclosure, a case where an inverter is used as an AC power source has been mainly described in embodiment 4. By using the control circuit13which controls each inverter described regarding the power source device400to the power source device403inFIG.12toFIG.15for embodiment 4, the frequency of the inverter is easily made variable.

Therefore, the inverter used for the power source device according to the present disclosure is desirably provided with a mechanism capable of controlling the frequency.

Meanwhile, a case where the frequency cannot be made variable is also conceivable.

For example, this case corresponds to a case where operation needs to be performed at a specific frequency; a case where a frequency command value is given from outside; or a case where matching with another device needs to be made.

Alternatively, this case corresponds to a case where AC of a frequency-fixed AC power source instead of an inverter, that is, AC of a grid, is directly used; or a case where oscillation is desired to be caused at 13.56 MHz or a frequency obtained by multiplication thereof in consideration of restrictions stipulated in the Radio Act.

In such a case, it is necessary to fix the frequency and adjust a circuit constant to achieve resonance matching. To this end, a mechanism capable of adjusting the inductance of the inductor or the capacitance of the capacitor is provided.

FIG.16shows a specific configuration example of a power source device in which the adjustment mechanism is used.

A power source device500includes the AC power source1as a voltage source; the capacitive load2composed of the equivalent capacitor3and the equivalent resistor4; a variable load inductor5A which forms a resonance circuit together with the capacitive load2; and the capacitor7and the inductor6which are used for amplifying the quality factor of the resonance circuit.

The power source device500further includes a voltage detector19which detects a voltage applied to the capacitive load2; and an adjustment mechanism40which adjusts the inductance of the variable load inductor5A.

In the case of adjusting the inductance of an inductor (coil), the inductance ordinarily needs to be mechanically adjusted. The adjustment mechanism40described here includes such a mechanical adjustment mechanism.

Further, it is also possible to, for example, provide the voltage detector19which detects a voltage of the circuit, and feed back the detected voltage value to the adjustment mechanism40. In this case, the adjustment mechanism40adjusts the inductance value of the variable load inductor5A such that the detected voltage is maximized.

The power source device500inFIG.16is configured to perform feedback adjustment on the inductance value of the variable load inductor5A according to the voltage value from the voltage detector19by using the adjustment mechanism40.

Although, in the power source device500inFIG.16, the adjustment mechanism is provided with respect to the load inductor5of the power source device100inFIG.1for embodiment 1, an adjustment mechanism can also be provided with respect to the load capacitor11of the power source device300inFIG.7for embodiment 3.

FIG.17shows a configuration example in which an adjustment mechanism is provided with respect to the load capacitor11of the power source device300inFIG.7for embodiment 3. It is noted that the power source device inFIG.17is shown as a power source device501to be distinguished from the power source device500inFIG.16.

The power source device501inFIG.17performs feedback adjustment on the capacitance value of a variable load capacitor11A according to the voltage value from the voltage detector19by using an adjustment mechanism41.

Further, an adjustment mechanism can also be provided with respect to the inductor6or the capacitor7which form the first stage of resonance circuit in the power source device100or the power source device300.

Specifically, for example, it is effective to provide, to the power source device100inFIG.1for embodiment 1, an adjustment mechanism which makes variable at least one inductance or capacitance among the inductance of the inductor6, the capacitance of the capacitor7, and the inductance of the load inductor5.

In addition, for example, it is effective to provide, to the power source device300inFIG.7for embodiment 3, an adjustment mechanism which makes variable at least one inductance or capacitance among the inductance of the inductor6, the capacitance of the capacitor7, and the capacitance of the load capacitor11.

Further, each of the adjustment mechanisms described above in embodiment 5 can be provided to the power source device200inFIG.6for embodiment 2 and the power source device304inFIG.11for embodiment 3.

Further, a case where, even if the frequency of the AC power source can be made variable, the range of possible variation is restricted is also conceivable.

For example, in barrier discharge of an ozonizer or the like, the appropriate frequency range is limited since supplied power is proportional to frequency. Moreover, the fluctuation width of the circuit constant of each circuit element or the change width, of the average capacitance of the capacitive load or the like, based on an operation condition is large, and might be unable to be adjusted within a range of frequency capable of being made variable by the power source device. One of solutions in this case is to provide a mechanism for adjusting the circuit constant of the circuit element.

In this case, slight adjustment of a frequency within a narrow frequency range can be performed by an inverter, and thus the value of the inductance or the capacitance does not need to be continuously changed and only has to be adjusted in several stages,

Specifically, it is also possible to provide a plurality of inductors or capacitors in parallel and perform switching therebetween by a relay, to adjust the value of the inductance or the capacitance.

Embodiment 6

In embodiment 6, quantitative contemplation is conducted regarding allowable fluctuation ranges for each circuit constant in a resonance circuit as a part of the power source device; and the frequency of the AC power source as a part of the power source device.

In order for the power source device according to the present disclosure to sufficiently exhibit the performance thereof, expression (1) needs to be satisfied. However, when, for example, the average capacitance Cs of the Capacitive load has changed, both of the two equalities in expression (1) cannot be satisfied by merely changing the frequency. Provision of two mechanisms which each change an inductance or a capacitance makes it possible to simultaneously satisfy the two equalities in expression (1). However, this provision makes it difficult, in terms of mechanism, to physically change the circuit constant.

Therefore, in designing of the power source device according to the present disclosure, even if designing is made so as to satisfy expression (1) under a rated condition, it is necessary to first ascertain what the fluctuation range of the capacitance or the inductance of the load is. In addition, in a case where the capacitance or the inductance of the load fluctuates, in particular, in a case where the circuit constant changes according to an operation condition such as power of the load, it is necessary to ascertain how the circuit constant changes upon a change in the operation condition, a transient response, start-up, or the like. Further, it is necessary to ascertain the extent to which this change in the circuit constant influences resonance; and whether any problem arises in terms of circuit operation.

In this case, it is conceivable to control the frequency of the inverter so as to successfully perform resonance matching. A key to the power source device according to the present disclosure is to form a circuit that satisfies expression (1), and it is necessary to take a countermeasure on the assumption that, if the inductance and the capacitance of the circuit have simultaneously changed, the condition in expression (1) becomes unsatisfied and it becomes unable to perfectly achieve resonance matching.

That is, important issues are how to change the frequency and how to design an operation allowable range and a control method.

Next, for the power source device according to the present disclosure, quantitative contemplation is conducted as to the extent of deviation, from the equalities in expression (1), that may occur.

When the voltage of the load is boosted to Vp at a resonance angular frequency ω0(resonance point), an angular frequency at which the voltage of the load becomes Vp/2 as a result of changing the angular frequency from ω0 to a slightly lower side is defined as ω1. In contrast, an angular frequency at which the voltage of the load becomes Vp/2 as a result of changing the angular frequency to a slightly higher side is defined as ω2.

In this case, the quality factor is expressed with expression (4). In addition, expression (5) is derived from expression (4).
Q=ω0/(ω2−ω1)  (4)
ω2−ω1=ω0/Q(5)

Here, if the target value of the quality factor in the power source device according to the present disclosure is set to be equal to or larger than 5 and desirably equal to or larger than 10, a frequency width at which the voltage becomes half is 20% of a resonance frequency in the case of Q=5 and is equal to or lower than 10% of the resonance frequency in the case of Q=10.

This fact is considered as follows with reference back to expression (1). That is, if Q=5 is assumed to be satisfied, when the frequency fluctuates by a width of 20%, that is, ±10%, with respect to the resonance frequency, the right-hand side of expression (1) fluctuates by +20%. Likewise, if Q=10 is assumed to be satisfied, when the frequency fluctuates by a width of 10%, that is, 5%, with respect to the resonance frequency, the right-hand side of expression (1) fluctuates by ±10%.

This fact applies not only to the frequency but also to the circuit constant,

That is, in the case of Q=5, when, for example, the circuit constant fluctuates and, as a result, Lp×Cp fluctuates by 20%, this means that drive with the frequency fv being kept at a pre-fluctuation value causes a boost voltage to be half.

This way of thinking forms the basis of a fluctuation range regarding expression (1). That is, in the case of Q=5, designing should be performed on the assumption that each term in expression (1) fluctuates by about ±20%.

If the quality factor increases, the (allowable) width of this fluctuation decreases. For example, in the case of Q=10, this width is about ±10%.

If the above contemplation results are expressed with expressions, allowable fluctuation ranges of the respective circuit constants in the case of Q=5 are as indicated by expression (6) and expression (7).
0.8/((2π·fv){circumflex over ( )}2)<Lp·Cp<1.2/((2π·fv){circumflex over ( )}2)  (6)
0.8/((2π·fv){circumflex over ( )}2)<Ls·Cs<1.2/((2π·fv){circumflex over ( )}2)  (7)

Allowable fluctuation ranges of the respective circuit constants in the case of Q=10 are as indicated by expression (8) and expression (9).
0.9/((2π·fv){circumflex over ( )}2)<Lp·Cp<1.1/((2π·fv){circumflex over ( )}2)  (8)
0.9/((2π·fv){circumflex over ( )}2)<Ls·Cs<1.1/((2π·fv){circumflex over ( )}2)  (9)

Therefore, since the target value of the quality factor in the power source device according to the present disclosure is equal to or larger than 5 as described above, it is effective to employ a configuration in which expression (6) and expression (7) are basically satisfied for the power source device100inFIG.1for embodiment 1, for example.

In addition, it is effective to employ a configuration in which expression (6) and expression (7) are basically satisfied for the power source device200inFIG.6for embodiment 2.

In addition, it is effective to employ a configuration in which expression (6) and expression (7) are basically satisfied for the power source device300and the power source device304respectively inFIG.7andFIG.11for embodiment 3.

Embodiment 7

Embodiment 7 relates to a power source device configured such that one or both of a voltage and a current of a resonance circuit are detected and fed back to a control circuit of an inverter, and a resonance state is maintained; and a power source device configured such that a voltage and a current of the AC power source are detected and the phase difference between the voltage and the current is minimized so that a resonance state is maintained.

The power source device according to embodiment 7 will be described focusing on differences from embodiment 1 with reference toFIG.18which is a configuration diagram of a power source device that performs control based on a voltage of the capacitive load;FIG.19which is a configuration diagram of a power source device that performs control based on a current of the capacitive load;FIG.20which is a configuration diagram of a power source device that performs control based on a current of the AC power source; andFIG.21which is a configuration diagram of a power source device that performs control based on a voltage and a current of the AC power source.

In the configuration diagram for embodiment 7, parts identical or corresponding to those in embodiment 1 are denoted by the same reference characters.

In embodiment 7, control methods will be described as to how to confirm that resonance of the resonance circuit is attained; and how to perform control, Specific configuration examples of power source devices to which the control methods have been applied, will be described.

Each control method is applied to the power source device100inFIG.1for embodiment 1 as a base, but is applicable to the other power source devices in the same manner.

Firstly, a configuration example of a power source device that performs control based on a voltage of the capacitive load will be described with reference toFIG.18. The power source device and the control circuit inFIG.18are shown as a power source device701and a control circuit13A to be distinguished from those inFIG.1for embodiment 1.

The power source device701includes the AC power source1as a voltage source; the capacitive load2composed of the equivalent capacitor3and the equivalent resistor4; the load inductor5which forms a resonance circuit together with the capacitive load2; and the capacitor7and the inductor6which are used for amplifying the quality factor of the resonance circuit.

The power source device701further includes the voltage detector19which detects a voltage applied to the capacitive load2; and the control circuit13A which controls the inverter unit of the AC power source1as an AC voltage source according to the voltage detected by the voltage detector19.

It is noted that the capacitive load2, the load inductor5, the capacitor7, and the inductor6in the power source device701according to embodiment 7 are the same as those in the power source device100according to embodiment 1, and thus only the control circuit13A and the voltage detector19which have been added will be described.

A voltage across the voltage detector19which detects a voltage applied to the capacitive load2, that is, a voltage across the capacitive load2, is detected by the voltage detector19and fed back to the control circuit13, and the inverter unit of the AC power source1as an AC voltage source is controlled.

Specifically, since the voltage across the capacitive load2is AC voltage, for example, the amplitude of the voltage detected by the voltage detector19is detected and fed back to the control circuit13, and the frequency of the inverter is controlled such that the amplitude value of the detected voltage is maximized.

This is the most direct detection-and-control method for a power source device intended for boosting voltage by means of a series resonance circuit.

Next, a configuration example of a power source device that performs control based on a current of the capacitive load will be described with reference toFIG.19. The power source device and the control circuit inFIG.19are shown as a power source device702and a control circuit13B to be distinguished from those inFIG.18.

A difference between the power source device702inFIG.19and the power source device701inFIG.18is that a current flowing through the capacitive load2is detected by a current detector20instead of detecting a voltage across the capacitive load2by the voltage detector19. Only this difference will be described.

In general, when voltage increases, current also increases. Thus, if a current flowing through the capacitive load2is detected by the current detector20and fed back to the control circuit13B such that the detected current is maximized, the resonance point can be indirectly searched for.

FIG.19shows an example in which current detection is applied to a voltage-resonance-type circuit.

Although not shown, a method for detecting a current of the inductive load8of a current-resonance-type circuit such as one in the power source device300inFIG.7for embodiment 3 is, similarly to a method for detecting a voltage inFIG.18, a direct detection method for detecting a current that is intended to be controlled and that is desired to be amplified. If the detected current is fed back to the control circuit and control is performed such that the detected current is maximized, the resonance point can be directly searched for.

Alternatively, in the power source device300inFIG.7for embodiment 3, a voltage of the inductive load8is detected, the detected voltage is fed back to the control circuit, and control is performed such that the detected voltage is maximized. Consequently, the resonance point can be indirectly searched for.

It is also conceivable to detect a voltage of the capacitor7instead of detecting a voltage across the capacitive load2in the power source device701inFIG.18. However, the method in this case involves detection of a resonance state in the first stage and is an indirect detection method.

Regarding detection of a voltage or a current, a method involving reference to the amplitude or the effective value thereof is the easiest and clearest detection method, and another method involving reference to a waveform harmonic is also conceivable.

This is because, as the state of a resonance circuit becomes more approximate to a resonance state, the voltage/current waveform of the resonance circuit becomes more similar to the waveform of a sine wave, and the proportion of a harmonic becomes lower. If a harmonic having the voltage/current waveform of the resonance circuit is monitored and control is performed so as to make the voltage/current waveform as similar to that of a sine wave as possible such that the harmonic is set to be as small as possible, approximation to the resonance point can be achieved.

Next, a configuration example of a power source device that performs control based on a current of the AC power source will be described with reference toFIG.20. InFIG.20, the power source device and the control circuit are shown as a power source device703and a control circuit13C to be distinguished from those inFIG.18.

A difference between the power source device703inFIG.20and the power source device702inFIG.19is that a current flowing through the inductor6is detected instead of detecting a current flowing through the capacitive load2by the current detector20.

Although a current flowing through the inductor6is detected inFIG.20, this should rather be regarded as a situation in which a current of the inverter of the AC power source1is detected. In this case, attention needs to be paid to the fact that, if supplied power to the capacitive load2is the same, a lower detected current inFIG.20leads to further approximation to the resonance point.

In the case of detecting a current of the inverter of the AC power source1, control is desirably performed such that the power factor of the load, as seen from inverter output, including the resonance circuit as well, is set to be as approximate to 1 as possible. That is, an output voltage and an output current of the AC power source1are detected, and control is performed such that the phases of the output voltage and the output current are set to be as equal to each other as possible, that is, such that the phase difference between the output voltage and the output current is minimized. Consequently, approximation to the resonance point can be achieved.

A specific configuration example in this case is shown inFIG.21. The power source device and the control circuit inFIG.21are shown as a power source device704and a control circuit13D to be distinguished from those inFIG.18.

In the power source device704inFIG.21, an output voltage and an output current of the AC power source1are detected, and the control circuit13D performs control on the basis of the output voltage and the output current such that the phase difference between the output voltage and the output current is minimized.

In this case, a voltage-type inverter is formed, and the control circuit13D ascertains an inverter output waveform. Therefore, control is desirably performed such that the phase of a current waveform of the inverter is set to be as identical to the phase of a voltage waveform thereof as possible, that is, the phase difference therebetween is set to be as approximate to zero as possible; the phase of the current waveform is delayed behind the phase of the voltage waveform as described later; or so-called zero voltage switching is performed in which inverter switching is performed at a moment at which the current becomes zero.

The phases of the voltage waveform and the current waveform of the inverter becoming equal to each other means that the power factor is maximized. That is, this indicates that operation is performed at the resonance point.

This control method is applicable also to a current-type inverter, that is, the power source device300inFIG.7for embodiment 3.

That is, if control is performed such that the phase difference between the output voltage and the output current of the AC power source12as an AC current source is minimized, approximation to the resonance point can be achieved (not shown).

Descriptions have been given above regarding a method in which the state of the resonance circuit is detected by using the voltage detector or the current detector; and control is performed such that the state of the resonance circuit becomes approximate to a resonance state. Although examples in each of which only one voltage detector or only one current detector is used have been described above, it is also possible to use both the voltage detector and the current detector, or a plurality of voltages or currents may be detected by using a plurality of voltage detectors or current detectors.

In addition, although a method for detecting an optimum drive condition on the basis of the phase difference between the voltage and the current of the inverter has been described, since the phase difference between the current and the voltage sensitively reflects a resonance state, it is also useful to detect a voltage and a current, and detect the phase difference between the voltage waveform and the current waveform to use the phase difference for control.

In addition, the method in which the resonance state of the resonance circuit is maintained as described above in embodiment 7 is applicable also to the power source device200inFIG.6for embodiment 2 and the power source device304according to embodiment 3.

Embodiment 8

Embodiment 8 relates to a power source device in which an optimum operation state is obtained through feedforward control on the basis of a prestored optimal operation condition.

The power source device according to embodiment 8 will be described focusing on differences from embodiment 1 with reference toFIG.22which is a configuration diagram of a power source device that performs control on the basis of a prestored optimal operation condition.

In the configuration diagram for embodiment 8, parts identical or corresponding to those in embodiment 1 are denoted by the same reference characters.

Control involving a so-called closed loop in which a current and a voltage are detected and fed back to a control system has been described in embodiment 7. Meanwhile, it is also conceivable to perform control involving an open loop, that is, feedforward control. For example, in a case where change in the state of the load with respect to operation condition is known in advance, an optimum frequency is obtained in advance according to the operation condition.

For example, in an ozonizer, an optimum frequency is determined according to supplied power as described in Patent Document 1. In such a case, with a table regarding a drive frequency with respect to set power being prestored in a memory, drive only has to be performed at a frequency that is based on a power command value given from outside.

FIG.22shows a specific configuration example of a power source device in which this feedforward control is employed.

A power source device800includes the AC power source1as a voltage source; a control circuit13E which controls the inverter unit of the AC power source1; the capacitive load2composed of the equivalent capacitor3and the equivalent resistor4; the load inductor5which forms a resonance circuit together with the capacitive load2; and the capacitor7and the inductor6which are used for amplifying the quality factor of the resonance circuit.

The power source device800further includes a storage unit50storing therein a table regarding an optimum frequency with respect to a power command value. InFIG.22, PI is a power command.

The control circuit138receives the power command (PI) from outside and sets the frequency to an optimum frequency on the basis of a command value of the power command with reference to the table stored in the storage unit50, to control the inverter of the AC power source1. It is noted that the storage unit50may be provided inside the control circuit13E.

The configuration of the power source device800inFIG.22has an advantage that neither a voltage nor a current needs to be detected so that control is easily performed at high speed. In particular, in cases where power significantly fluctuates upon start-up or the like, that is, in the case of occurrence of discontinuous changes in Characteristics such as a change from a state where discharge lighting has not occurred to a state where discharge lighting has occurred, control might become unstable with a feedback system, and thus feedforward control is effective. Moreover, feedforward control is particularly effective in a case where, as in the power source device according to the present disclosure, the quality factor of the resonance circuit is high, the operation frequency range is narrow, and control might become unstable with a feedback system.

It is also effective to make use of the advantages of both feedforward control and feedback control as follows. That is, upon start-up of the power source device800and in the case of performing initial setting for power, feedforward control is performed on the basis of the table regarding an optimum frequency with respect to a power command value, whereas, when operation starts to be stabilized, a voltage and a current of the resonance circuit are detected to perform feedback control in order to accurately maintain this stabilized state.

An example in which the control circuit13E and the storage unit50are added to, and feedforward control is applied to, the power source device100inFIG.1for embodiment 1, has been described above.

The same advantageous effects can be obtained also if the control circuit and the storage unit are added to, and feedforward control is applied to, the power source device300inFIG.7for embodiment 3 (not shown).

In addition, the method described above in embodiment 8 is applicable to the power source device200inFIG.6for embodiment 2 and the power source device304inFIG.11for embodiment 3 in the same manner.

Embodiment 9

In embodiment 9, a resonance stabilization condition for a resonance circuit as a part of a power source device will be described.

In embodiment 5 to embodiment 8, descriptions have been given regarding a method in which the circuit constants in the resonance circuit and the frequency of the AC power source are changed; a method in which a voltage and a current of the resonance circuit are detected and fed back; and a method in which feedforward control is performed on the basis of a prestored optimal operation condition.

The above control methods are each intended for performing control so as to maintain an optimum condition for resonance.

Here, an optimum condition for resonance of the resonance circuit will be described.

Regarding an ozonizer as a capacitive load, operation of the ozonizer becomes more stable if a load circuit including a resonance circuit as seen from an inverter is experiencing phase delay than if the load circuit is exactly at the resonance point. This fact is described also in Patent Document 1.

The phase delay refers to a state where the phase of a current is delayed behind the phase of a voltage. In the case of a simple LC series circuit, this state is not a state where impedances of an inductor (L) and a capacitor (C) completely cancel each other out, but is a state where the inductance component is slightly greater, that is, a state where operation is being performed at a frequency that is slightly higher than the resonance frequency.

This can be explained from the aspect of stability of electric discharge with respect to a barrier discharge load such as an ozonizer. However, more generally, in the case of performing drive with a voltage-type inverter, operation of an inverter becomes more stable with a slight phase delay.

So-called zero voltage switching (ZVS) involving inverter switching at a moment at which a current waveform that has come to be substantially of a sine wave for resonance intersects zero, is considered to result in least loss. Further, an operation in which the frequency is set to be high as compared to a ZVS condition so as to perform adjustment in a direction of delaying the phase is considered to be more desirable, as an operation of the inverter, than an operation in which the frequency is set to be low (in a direction of advancing the phase) as compared to the ZVS condition.

Thus, drive is desirably performed with phase delay relative to a resonance point, that is, at a frequency that is slightly higher than a resonance frequency, in the case of driving a resonance circuit in consideration of operation and stability of an inverter as well,

Further, the following problem is also conceivable in the case of the power source device according to the present disclosure. That is, since the quality factor is considerably high, slight deviation of the frequency from the resonance frequency disables resonance operation, and thus disables normal operation of the capacitive load or the inductive load.

This problem is a design problem, and it is necessary to take a countermeasure of guaranteeing controllability at the sacrifice of the quality factor to some extent or performing configuring such that change in circuit constant upon change in operation condition and upon deterioration over time becomes allowable.

The power source device according to the present disclosure is applicable to various cases such as cases of utilizing an AC voltage source, an AC current source, series resonance, parallel resonance, an inductive load, a capacitive load, voltage detection, and current detection.

In embodiment 1 to embodiment 8, examples of only some of combinations thereof are shown, but applicability also to other similar combinations is realized.

Regarding use, descriptions have been given mainly for the inductive loads and the capacitive loads. In particular, descriptions have been given focusing on a barrier discharge load such as an ozonizer having characteristic properties owing to electric discharge. However, use for other general capacitive loads and inductive loads can be realized.

Further, applicability also to a resonance-type converter utilizing resonance and non-contact power feeding may be realized.

Although the disclosure is described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects, and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations to one or more of the embodiments of the disclosure.

It is therefore understood that numerous modifications which have not been exemplified can be devised without departing from the scope of the present disclosure. For example, at least one of the constituent parts may be modified, added, or eliminated. At least one of the constituent parts mentioned in at least one of the preferred embodiments may be selected and combined with the constituent parts mentioned in another preferred embodiment.

DESCRIPTION OF THE REFERENCE CHARACTERS

100,101,102,103,104,200,300,301,302,303,304,400,401,402,403,500,501,701,702,703,704,800power source device1AC power source1A,1B AC voltage source12AC power source12A,12B AC current source2capacitive load3equivalent capacitor4equivalent resistor5load inductor6inductor7capacitor8inductive load9equivalent inductor10equivalent resistor11load capacitor13,13A,13B,13C,13D,13E control circuit14constant voltage source15capacitor16constant current source17,18inductor19voltage detector20current detector21load circuit30,32full-bridge inverter31half-bridge inverter40adjustment mechanism41adjustment mechanism50storage unit321load circuit2a,2bcapacitive load3a,3bequivalent capacitor4a,4bequivalent resistor5a,5bload inductor8a,8binductive load9a,9bequivalent inductor10a,10bequivalent resistor11a,11bload capacitor5A variable load inductor11A variable load capacitorL1first inductorLn−1 (n−1)-th inductorLn n-th inductorC1first capacitorCn−1 (n−1)-th capacitorCn n-th capacitor