Apparatus and method for power conversion
A power converting apparatus includes a rectifying circuit having a pair of AC power input terminals and a pair of rectified voltage output terminals; a reactor; and a charging and discharging circuit connected between the rectified voltage output terminals. The charging and discharging circuit includes a first condenser connected with one of the rectified voltage output terminals and one of the AC power input terminals; and a second condenser connected with the other of the rectified voltage output terminals and the one AC power input terminal. The reactor generates a resonance current together with the first condenser and the second condenser, and the second condenser discharges to zero voltage while the first condenser is charged.
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1. Field of the Invention
The present invention relates to a power converting apparatus and a power converting method, and in particular, relates to a power converting apparatus involving a rectifier and a power converting methods
2. Description of the Related Art
A converter incorporated into a power supply circuit of an air conditioning equipment and so on is generally used as a single-phase full-wave rectifier circuit. Power factor improvement and suppression of harmonic wave generation are required for the converter. As shown in
A converter in which a voltage boosting circuit is mounted between power supply terminals is shown in the first conventional example. As shown in
The technique in the first conventional example would be specifically realized as shown in
In an aspect of the present invention, a power converting apparatus includes a rectifying circuit having a pair of AC power input terminals and a pair of rectified voltage output terminals; a reactor; and a charging and discharging circuit connected between the rectified voltage output terminals. The charging and discharging circuit includes a first condenser connected with one of the rectified voltage output terminals and one of the AC power input terminals; and a second condenser connected with the other of the rectified voltage output terminals and the one AC power input terminal. The reactor generates a resonance current together with the first condenser and the second condenser, and the second condenser discharges to zero voltage while the first condenser is charged.
Here, a maximum value of a current flowing from one of the first condenser and the second condenser to the one AC input terminal at a rated operation may be substantially same as a maximum value of a rated input current.
Also, capacitances of the first condenser and the second condenser and an inductance of the reactor are preferably determined such that a resonance frequency is in a range of 3 times to 5 times of a frequency of AC power supplied to the AC power input terminals.
When a rated impedance is determined as a value obtained by dividing a second power of rated power by rated voltage, a square root of a value obtained by dividing the inductance by the capacitance is preferably in a range of 0.7 times to 1.2 times of the rated impedance.
Also, capacitances of the first condenser and the second condenser and an inductance of the reactor are preferably determined such that a resonance frequency is in a range of 3 times to 5 times of a frequency of AC power supplied to the AC power input terminals. Also, when a rated impedance is determined as a value obtained by dividing a second power of rated power by rated voltage, a square root of a value obtained by dividing the inductance by the capacitance is preferably in a range of 0.7 times to 1.2 times of the rated impedance.
Also, in another aspect of the present invention, a power converting apparatus includes a rectifying circuit having a pair of AC power input terminals and a pair of rectified voltage output terminals; a reactor; and a charging and discharging circuit connected between the rectified voltage output terminals. The charging and discharging circuit includes a first charging and discharging circuit connected with one of the rectified voltage output terminals and one of the AC power input terminals; and a second charging and discharging circuit connected with the other of the rectified voltage output terminals and the one AC power input terminal. The first charging and discharging circuit includes a first diode and a first condenser connected with the first diode in series. The second charging and discharging circuit may include a second diode and a second condenser connected with the second diode in series. The charging and discharging circuit further includes a switch section connected in parallel with a series connection of the first and second diodes, and the reactor generates a resonance current together with the first condenser and the second condenser.
Here, the switch section may include two switches which are connected in parallel with said first and second diodes, respectively.
Also, the switch section may include a switching element. Instead, each of the switches may include a switching element.
Also, a maximum value of a current flowing from one of the first condenser and the second condenser to the one AC input terminal at a rated operation may be substantially same as a maximum value of a rated input current.
Also, capacitances of the first condenser and the second condenser and an inductance of the reactor are preferably determined such that a resonance frequency is in a range of 3 times to 5 times of a frequency of AC power supplied to the AC power input terminals.
Also, when a rated impedance is determined as a value obtained by dividing a second power of rated power by rated voltage, a square root of a value obtained by dividing the inductance by the capacitance is preferably in a range of 0.7 times to 1.2 times of the rated impedance.
Also, capacitances of the first condenser and the second condenser and an inductance of the reactor are determined such that a resonance frequency is preferably in a range of 3 times to 5 times of a frequency of AC power supplied to the AC power input terminals.
Also, when a rated impedance is determined as a value obtained by dividing a second power of rated power by rated voltage, a square root of a value obtained by dividing the inductance by the capacitance is preferably in a range of 0.7 times to 1.2 times of the rated impedance.
Also, the power converting apparatus further includes a drive circuit which includes: a parallel circuit provided between a gate of the switching element and a control circuit. The parallel circuit may include a resistor circuit having a higher resistance; and a series circuit connected in parallel to the resistor circuit and comprising a resistor having a lower resistance, and a diode connected with the resistor to block off a gate current on charging of the gate.
Also, the switching element may receives at a gate thereof, a voltage from a control power supply of the power converting apparatus through a resistor and a diode.
Also, the first and second condensers discharge to zero voltage once for one period of the AC power.
The power converting apparatus may further include mechanical switches provided between a common node and the first condenser and between the common node and the second condenser.
In another aspect of the present invention, a power converting apparatus may include a rectifying circuit having a pair of AC power input terminals and a pair of rectified voltage output terminals; a reactor; and a charging and discharging circuit connected between the rectified voltage output terminals. The charging and discharging circuit includes a first charging and discharging circuit connected with one of the rectified voltage output terminals and one of the AC power input terminals; and a second charging and discharging circuit connected with the other of the rectified voltage output terminals and the one AC power input terminal. The first charging and discharging circuit includes a first switch and a first condenser connected with the first switch in series. The second charging and discharging circuit includes a second switch and a second condenser connected with the second switch in series, and the reactor generates a resonance current together with the first condenser and the second condenser.
Also, capacitances of the first condenser and the second condenser and an inductance of the reactor are preferably determined such that a resonance frequency is in a range of 3 times to 5 times of a frequency of AC power supplied to the AC power input terminals.
In another aspect of the present invention, a power converting method is achieved by connecting a rectifying circuit with an AC power supply; by charging a first charging and discharging section which is connected between a first output terminal as one of two first output terminals of the rectifying circuit and one of two AC power input terminals of the rectifying circuit; by discharging from a second charging and discharging section which is connected between a second output terminal as the other of the two first output terminals of the rectifying circuit and the one AC power input terminal in synchronization with the charging; by charging the second charging and discharging section after a half period to the charging the first charging and discharging section; by discharging the first charging and discharging section in synchronization with the charging the second charging and discharging section; by continuing to connect a terminal of the first charging and discharging section on a side of the AC electric power input terminals and a terminal of the second charging and discharging section on a side of the AC electric power input terminals during a rated operation; and intermittently opening the terminal of the first charging and discharging section on the side of the AC electric power input terminals and the terminal of the second charging and discharging section on the side of the AC electric power input terminals during a low load operation.
Here, the first charging and discharging section and the second charging and discharging section may have condensers, respectively. A reactor may be provided between the AC electrode input terminal and the rectifying circuit or between the rectifying circuit and the first charging and discharging section. The maximum value of a current flowing from one of the first condenser and the second condenser to the one AC input terminal at a rated operation condition may be substantially same as the maximum value of the rated input current.
Also, capacitances of the first condenser and the second condenser and an inductance of the reactor are preferably determined such that a resonance frequency is in a range of 3 times to 5 times of a frequency of AC power supplied to the AC power input terminals.
Also, the first charging and discharging section and the second charging and discharging section may have condensers, respectively. A reactor may be provided between the AC electrode input terminal and the rectifying circuit or between the rectifying circuit and the first charging and discharging section. A charging period of one of the first and second condensers and a discharging period of the other condenser may be synchronized with each other. The condenser preferably discharges to zero voltage after being charged.
In this case, capacitances of the first condenser and the second condenser and an inductance of the reactor are determined such that a resonance frequency is preferably in a range of 3 times to 5 times of a frequency of AC power supplied to the AC power input terminals.
BRIEF DESCRIPTION OF THE DRAWINGS
Hereinafter, a power converting apparatus according to the present invention will be described in detail with reference to the attached drawings.
In the power converting circuit 10, the charging and discharging circuit 11 is added as a power factor improving circuit, instead of the voltage boosting circuit in the conventional examples. In the charging and discharging circuit 11, a condenser 12 as a first charging and discharging circuit and a condenser 13 as a second charging and discharging circuit portion are connected in series. An intermediate node Z between the condenser 12 and the condenser 13 is referred to as a “common node” in relation to the charging and discharging circuit, and is connected directly to the node Z2 by a conductive short-circuited line 21. The direction of current flowing from the common node Z to the positive-output line 8 is referred as a first polarity 50, and the direction of current flowing from the common node Z to the negative-output line 9 is referred as a second polarity 60.
A feature of the common line 21 is that the current direction specifying circuit 106 (the two-directional switching circuit in
As shown in
A First Half Cycle of the First Operation Mode:
A Second Half Cycle of the First Operation Mode:
A switch for carrying out such alternate charging and discharging operation is not shown in
A Full Cycle of a Second Operation Mode:
The second operation mode is a conventional operation mode, in which the operation mode control switch 16 is opened at low load, the charging and discharging circuit 11 does not operate, and the rectifier circuit 3 carries out full-wave rectification. The opening and closing control of the operation mode control switch 16 will be mentioned later.
In the power converting apparatus of the present invention, the operation mode control switch 16 is closed at all times in the rated operation mode, and is opened at all times in the low load operation mode. The operation mode control switch 16 is a one-directional switch for switching the mode between the rated operation mode and the low load operation mode. In order to make the electric current flowing into the load 2 smooth in the low load operation mode, a rectification means (an example: the diode 24) is inserted in the positive-output line 8 in a downstream side from the condenser 12. A means of making the electric current flowing into the load 2 smooth in the low load operation mode is not limited to additional provision of the diode 24. It is also suitable to design the circuit constants of a plurality of circuit elements in a circuit, or to provide a reactor to an appropriate position in the circuit.
P=VI
Average power P during one cycle T of the AC power (=2π/ω) is expressed by the following equation as an average value of integration.
P=V′*I′*cos Ψ
Here, V′ and I′ are effective values. In the present invention, the input current Iin is the discharge current discharged from the condenser 12 or the condenser 13 for every half period. Therefore, the voltage Vin and the current Iin are synchronized with each other in the half period, and a phase difference Ψ between the input voltage Vin and the input current Iin is generally zero. Therefore, the power factor cos Ψ is approximately 1. The AC delay problem that the phase difference Ψ between the input current Iin and the input voltage Vin increases is eliminated by the presence of the reactor 7 through the charge and discharge current, and the phase difference Ψ is close to zero. Periodic switching of the charging operation and discharging operation resolves the problems of the electromagnetic interference as well as the power factor improvement, through suppression of the increase in output voltage. The decrease of output power can be made possible through the power factor improvement even if the output voltage is not increased, and as a result, it is possible to effectively resolve the power factor problem and the higher harmonic wave problem.
A combination of the operation mode control switch 16, the diodes 14 and 15, and the common line 21 forms a half-cycle alternate rectification charging and discharging circuit for supplementarily increasing the electric current from the positive-output line 8 to the load 2 through the discharging operation of one of the condensers 12 and 13 for every half period and eliminates the necessity of generation of double voltage by a boosting circuit. In such a charging and discharging circuit, a directionality of the operation mode control switch 16 is not required. A one-way directionality is enough and a two-way directionality is not necessary in reality. However, the operation mode control switch 16 is not necessarily forbidden to have the two-way directionality. Thus, various techniques can be used as the operation mode control switch 16.
In the above embodiments of the half-cycle alternate rectification charging and discharging circuit, the switching cycle (a discharge alternate cycle) is synchronized with (corresponds to) a cycle of the AC power supply 1.
The circuit constants (capacitances) of the condenser 12 and the condenser 13 contained in such a charging and discharging circuit are suppressed to a greatly lower value than the capacitance of the condenser in the conventional techniques (approximately one tenth). As a result of the provision of such circuit constants, the voltage-doubling circuit is completely or almost completely disappeared in the present invention. Peak values of the both condenser voltages are approximately equal to the peak output voltage Vm of the AC power supply 1. Consequently, high voltage endurance of all elements in the circuit is alleviated, and the miniaturization and the light weight can be realized. In a circuit section between the common node Z and the condenser 12 in the charging and discharging circuit, the polarity is given in which electric current flows from the common node Z to the condenser 12. In a circuit section between the common node Z and the condenser 13 in the charging and discharging circuit, the polarity is given in which electric current flows from the condenser 13 to the common node Z.
As described above, it is possible to further improve the power factor by making the input current Iin shown in
In the power converting apparatus of the present invention, although the common line 21 is short-circuited in principle, addition of an intermittent switch to control the current flow is not forbidden. The ON/OFF control is carried out by the intermittent switch in correspondence to, and particularly in synchronization with the cycle of the AC power supply. In principle, the switching element 16 is closed in the rated operation mode, and is open at the low load operation. However, it is not forbidden for the switching element 16 to be continuously or intermittently operated in the connection line 19 in a part of a half cycle, for the selection of the circuit constant or for stable low voltage resonance. The smoothing condenser 4 is connected in parallel with the charging and discharging circuit 11 between the positive output line 8 and negative output line 9 and may be placed outside the power converting circuit 10 board in
The operation mode control switch 16 is added. The operation mode control switch 16 is inserted in the connection line 19. The operation mode control switch 16 is effectively used to switch the first operation mode of the rated operation and the second operation mode of the low load operation. The first operation mode is an operation in which the charging and discharging operations of the first charging and discharging circuit and the second charging and discharging circuit are alternately switched in synchronization with the cycle of the AC power supply 1. The second operation mode is different from the first operation mode and an operation in which the rectifier circuit 3 carries out rectification. Advantages of controlling the opening and closing of the operation mode control switch 16 in a half cycle in the first operation mode are as mentioned above. The operation mode control switch 16 is used for both the operation mode switching and the control of the opening and closing in a half cycle. As such a switch, use of the one-directional switch or the two-directional switch is possible, and the IGBT is particularly suitable. More specifically, it is preferable to carry out intermittently switching control between the node P and the node Q in the first operation mode, in synchronization with the AC cycle, especially the half cycle, of the AC power supply 1. On the other hand, it is preferable to carry out opening control of the node P and the node Q in the second operation mode, regardless of the AC cycle, of the AC power supply 1.
In the power converting apparatus of the present invention, the first charging and discharging circuit has the first polarity in which the electric current flows from the common node Z to the first condenser 12 in one direction, and the second charging and discharging circuit has the second polarity in which the electric current flows from the second condenser 13 to the common node Z in one direction. Such polarity simplifies a circuit configuration. Such a circuit configuration is further simplified by addition of diodes 14 and 15.
In the circuit representations in FIGS. 4 to 7, shown as the preferred embodiments of the power converting apparatus of the present invention, the single-phase AC power supply 1 is connected to the full-wave rectifier circuit 3 through the reactor 7; the smoothing condenser 4 is connected between the positive and negative output lines 8 and 9 of the full-wave rectifier circuit 3; and the first condenser 12 and the second condenser 13 are connected between the positive and negative output lines 8 and 9 of the full-wave rectifier circuit 3. One side of the first condenser 12 is connected to the positive output line 8 of the full-wave rectifier circuit 3, and another side of the first condenser 12 is connected to a cathode of the first diode 14. An anode of the first diode 14 and a cathode of the second diode 15 are connected. An anode of the second diode 15 and one side of the second condenser are connected, and another side of the second condenser 13 is connected to the negative output line 9 of the full-wave rectifier circuit 3. The IGBT 16 is connected between the cathode of the first diode 14 and the anode of the second diode 15 as the operation mode control switch A control unit 20 controls the switch 16 in accordance with the load 2.
When the circuit is configured in the power supply voltage of 200V, the load of 1.5 kW, and the reactor of 16 mH, for example, as a more specific example for a circuit of
A simulation is carried out of the operation of the power converting apparatus according to the first embodiment of the present invention shown in
The simulation was carried out by using a measurement circuit shown in
Here, the rated operation mode is an operation mode that it is possible to cope with in case of rated load. Therefore, the simulation was carried out in the ON state of the switching element 16, that is, the connection line 19 was substantially short-circuited. It should be noted that in the rated operation mode, the load needs not to be rated load (100%) at all times, and may be 60% or 80% of the rated load be 60%.
The frequency of AC power supply 1 was 50 Hz which was one of the typical commercial cycles. The rated voltage was 200 V, the rated output was 1500 W, and the capacitance of the load condenser was set to 4700 μF which was general. The capacitances of the first and second condensers 12 and 13 were identical to each other, because the identical or approximately identical capacitance was preferable. In an actual case, because it was sometimes difficult to select the condensers having a strictly identical capacitance, it is preferable to select condensers having the same rated capacitance. Here, if the actual capacitance values are same even if the name of the condenser is different, the condensers can be used. Although the aluminum electrolytic condenser or the film condenser which are commercially available has the deviation of + or −10%, the deviation is permissible. Therefore, the condensers having an identical name can be used in many cases
It should be noted that the first condenser 12 is equivalent to the condenser 107 in
The simulation result and the consideration are presented below. For generalization of this simulation result, the resonance frequency f0 is employed as a measure of evaluation in relation of the capacitance of the condenser and the inductance value of the reactor 7. Here, the resonance frequency is a frequency determined from the well known equation: f0=1/2Π(LC)1/2, when the capacitance of the first or second condenser 12 is C and the inductance of reactor 7 is L.
In the first half period in which the input voltage is positive, input electric current Iin becomes Iin=Idc_a+Idc. Also, in the second half period in which the input voltage is negative, the input current becomes Iin=Idc_a−Idc.
Also,
From the above three simulation results, the result is obtained that the power factor is highest when the resonance frequency f0 is 4 times of the frequency of the AC power supply 1. Below, the general power factor characteristic will be discussed
Generally, the effective electric power P(ω) in the load is given by the following equation. This equation indicates that the effective electric power is obtained as an average of an integral value of a product of the instantaneous AC voltage v applied to the load 2 and the instantaneous AC current i flowing through the load 2 over one period.
Also, the apparent power S(ω) in the load 2 is given by the following equation.
The first term of the apparent power S(ω) indicates an effective value of load voltage and the second term indicate the effective value of the load electric current. The power factor (PF) is given as PF=P(ω)/S(ω).
Therefore, in order to improve the power factor, the effective electric power P should be made large. For this purpose, it is first necessary to make phase difference Ψ between the load voltage and the load electric current small. Next, it is necessary to make the apparent power S small. For this purpose, it is important to make the effective value of the electric current small, and thus, to suppress the peak value of the electric current.
Summarizing these results, it is preferable that the phase difference between the load voltage and the load electric current is made zero, and the load electric current has the same waveform as the sine voltage waveform, for the best power factor. Also, it is preferable that the peak value is equal to 1.41 times of the peak value of the load electric current. When the load electric current has a waveform different from the sine voltage waveform, the power factor decreases. Also, when the peak value is higher even in the same effective value, the power factor decreases. It is preferable that there is the uniform amplitude over the period.
From the above conclusion, the peak of the input electric current is large at the first simulation shown in
Moreover, in case of
Here, the input electric current is the rated input electric current when it is assumed that the input electric current waveform from the AC power supply 1 is a sine wave. More specifically, it is the sine wave electric current obtained by dividing the rated electric power of the load by the effective value of the rated voltage of the AC power supply (the effective value of the sine wave).
On the other hand, in
It should be noted that by selecting the condensers and reactors with proper circuit constants in the present invention, the “charge period of voltage VC1 (condenser 12)” and the “discharge period of voltage VC2 (condenser 13)” are substantially fully synchronizes with each other, and the “discharge period of voltage VC1” and the “charge period of voltage VC2” are substantially fully synchronizes with each other. That is, the fact that “the condenser always discharges fully to the zero voltage as shown in
In relation between the above fact and the three examination results, it was confirmed that the discharging operation was carried out until the voltage across the condenser reaches zero voltage as shown in
However, the reason why there is the difference in the power factor is the difference in a resonance frequency. The resonance frequency is determined in the relation of the inductance value (L) of the reactor 7 and the capacitance value (C) of the condensers 12 and 13. Therefore, it is preferable to select the inductance value (L) of the reactor 7 and the capacitance value (C) of the condensers 12 and 13 such that the maximum value of the resonance electric current is approximately the same as the maximum value of the rated input electric current, as the show in
On the other hand, in a usual power converting apparatus, the inductance of the reactor 7 is about 16 mH, and the capacitance value of condensers 12 and 13 is about 1000 μF or more. Under such conditions, the power factor becomes low. For this reason, the power factor is improved by using a switching element and so on. If the power converting circuit of the present invention is used, the good power factor can be obtained without carrying out a complicated switching operation.
In the above discussion, the capacitance value of the condenser is determined under the specific condition, by specifying the inductance value of the reactor 7. Therefore, based on above-mentioned assumption, the circuit constants for general design are considered using % impedance to be described below and the ratio of the square root of the ratio of the inductance value of the reactor to the capacitance value of the condenser to the % impedance. It should be noted that the word “condenser” means either of the condenser 12 or the condenser 13 for the simple explanation, because the both of the condensers 12 and 13 have the same capacitance.
When the following equation of the previous resonance frequency
f01/(2Π)(LC)1/2
is transformed, the following equation is obtained
LC=1/4Π2f02
Therefore, there are various combinations of L and C which meet this condition. For example, supposing the power supply frequency is 50 Hz, the resonance frequency is 200 Hz from f0=4f. If the capacitance C of the condenser is 20 μF, the inductance L is about 32 mH. Also, supposing that the capacitance C is 10 μF, the inductance L is about 63 mH. In this way, various combinations are possible.
As described above, the simulation was carried out at the rated voltage of 200 V, the rated electric power of 1500 W, and the frequency of 50 Hz. In this case, when the rated voltage, the rated output, and the frequency are changed, the inductance of the reactor and the capacitance of the condenser can be found such that the % impedance becomes constant.
In order to determine the % impedance (hereinafter, to be referred to as “% Z”), the rated electric current In is first determined from the rated voltage Vn and the rated output Pn and then impedance is determined from Zn=Vn/In. Supposing that the frequency is f and a desirable inductance value of the reactor determined from the above simulation is La, the reactor impedance Zr is Zr=2ΠfLa. Therefore, % Zr (% Z of the reactor) can be determined from a ratio of Zr to Zn used in the simulation, i.e., % Zr=Zr/Zn. similarly, supposing that a desirable capacitance value of the condenser is Ca, the condenser capacitance Zc is Zc=1/2πfCa. Therefore, % Zc (% Z of the condenser) can be determined from % Zc=Zc/Zn.
By using the determined % Zr and % Zc, the specific inductance and capacitance of the reactor and condenser can be set for the change of the rated voltage, the rated electric power, and the frequency. For example, when the frequency is simply only changed from 50 Hz to 60 Hz and the other rated values are not changed, it is not necessary to change the inductance value of the reactor and the capacitance of the condenser because % Zr and % Zc are not changed. When the rated voltage is 100 V (1/2 in the simulation) and the rated output is 1000 W (2/3 in the simulation), the rated current is 10 A, and Zn=10. Therefore, the impedance becomes 3/8 times in comparison of Zn=200/7.5=80/3 in the above example. In this case, the inductance value of the reactor and the capacitance of the condenser are determined by multiplying the impedance Zr and Zc by 3/8, respectively.
The general design method was considered based on the examined rated impedance described above, and a square root of a ratio of the inductance value (L) of the reactor and the capacitance value (C) of the condenser, i.e., (L/C)1/2. Here, the reason why (L/C)1/2 is used as one measure is that Zr*Zc=La/Ca because Zr=2πfLa and Zc=1/2πfCa as mentioned above. Thus, it is assumed that the square root became one measure. A result of simulation which is carried out over an extensive value range by using this square root value and the above-mentioned rated impedance, (rated Z) is shown in
Assuming that the power supply frequency is 50 Hz, the capacitance value of the condenser is 1000 μF and the inductance value of the reactor is 16 mH, in the conventional power converting apparatus, the resonance frequency about 0.8 times the frequency of the AC power supply and very low, because the resonance frequency is about 40 HZ. Also, although the multiplying factor of the resonance frequency to the AC power supply frequency changes depending on the value of the (L/C)1/2/rated Z, it is preferable that the inductance value of the reactor is as small as possible, from the viewpoint of cost reduction. Also, it is also preferable that the capacitance value of the condenser is small in a range. It could be understood from the
As a modification of this embodiment of the present invention, the number of degrees of freedom of the position of the reactor 7 is improved. In other words, in
As described above with reference to
Moreover, in order to improve the power factor, the inductance value of the reactor and the capacitance value of the condenser are determined in such a manner that the maximum value of the resonance electric current is made approximately same as the maximum value of the rated input electric current.
The specific values of the resonance frequency already described and the values of the % impedance and so on are only examples specified based on above basic idea.
The circuit shown in
It should be noted that the booster circuit 26 of
The power converting apparatus and the power converting method according to the present invention effectively improve the power factor. As the embodiments, the number of circuit elements is decreased.
Claims
1. A power converting apparatus comprising:
- a rectifying circuit having a pair of AC power input terminals and a pair of rectified voltage output terminals;
- a reactor; and
- a charging and discharging circuit connected between said rectified voltage output terminals,
- wherein said charging and discharging circuit comprises:
- a first condenser connected with one of said rectified voltage output terminals and one of said AC power input terminals; and
- a second condenser connected with the other of said rectified voltage output terminals and said one AC power input terminal,
- said reactor generates a resonance current together with said first condenser and said second condenser, and
- said second condenser discharges to zero voltage while said first condenser is charged.
2. The power converting apparatus according to claim 1, wherein a maximum value of a current flowing from one of said first condenser and said second condenser to said one AC input terminal at a rated operation is substantially same as a maximum value of a rated input current.
3. The power converting apparatus according to claim 1, wherein capacitances of said first condenser and said second condenser and an inductance of said reactor are determined such that a resonance frequency is in a range of 3 times to 5 times of a frequency of AC power supplied to said AC power input terminals.
4. The power converting apparatus according to claim 1, wherein when a rated impedance is determined as a value obtained by dividing a second power of rated power by rated voltage, a square root of a value obtained by dividing said inductance by said capacitance is in a range of 0.7 times to 1.2 times of said rated impedance.
5. The power converting apparatus according to claim 2, wherein capacitances of said first condenser and said second condenser and an inductance of said reactor are determined such that a resonance frequency is in a range of 3 times to 5 times of a frequency of AC power supplied to said AC power input terminals.
6. The power converting apparatus according to claim 2, wherein when a rated impedance is determined as a value obtained by dividing a second power of rated power by rated voltage, a square root of a value obtained by dividing said inductance by said capacitance is in a range of 0.7 times to 1.2 times of said rated impedance.
7. A power converting apparatus comprising:
- a rectifying circuit having a pair of AC power input terminals and a pair of rectified voltage output terminals;
- a reactor; and
- a charging and discharging circuit connected between said rectified voltage output terminals,
- wherein said charging and discharging circuit comprises:
- a first charging and discharging circuit connected with one of said rectified voltage output terminals and one of said AC power input terminals; and
- a second charging and discharging circuit connected with the other of said rectified voltage output terminals and said one AC power input terminal,
- said first charging and discharging circuit comprises a first diode and a first condenser connected with said first diode in series,
- said second charging and discharging circuit comprises a second diode and a second condenser connected with said second diode in series, and
- said charging and discharging circuit further comprises:
- a switch section connected in parallel with a series connection of said first and second diodes,
- said reactor generates a resonance current together with said first condenser and said second condenser, and
- said second condenser discharges to zero voltage while said first condenser is charged.
8. The power converting apparatus according to claim 7, wherein said switch section comprises two switches which are connected in parallel with said first and second diodes, respectively.
9. The power converting apparatus according to claim 7, wherein said switch comprises a switching element.
10. The power converting apparatus according to claim 8, wherein each of said switches comprises a switching element.
11. The power converting apparatus according to claim 7, wherein a maximum value of a current flowing from one of said first condenser and said second condenser to said one AC input terminal at a rated operation is substantially same as a maximum value of a rated input current.
12. The power converting apparatus according to claim 7, wherein capacitances of said first condenser and said second condenser and an inductance of said reactor are determined such that a resonance frequency is in a range of 3 times to 5 times of a frequency of AC power supplied to said AC power input terminals.
13. The power converting apparatus according to claim 7, wherein when a rated impedance is determined as a value obtained by dividing a second power of rated power by rated voltage, a square root of a value obtained by dividing said inductance by said capacitance is in a range of 0.7 times to 1.2 times of said rated impedance.
14. The power converting apparatus according to claim 8, wherein capacitances of said first condenser and said second condenser and an inductance of said reactor are determined such that a resonance frequency is in a range of 3 times to 5 times of a frequency of AC power supplied to said AC power input terminals.
15. The power converting apparatus according to claim 8, wherein when a rated impedance is determined as a value obtained by dividing a second power of rated power by rated voltage, a square root of a value obtained by dividing said inductance by said capacitance is in a range of 0.7 times to 1.2 times of said rated impedance.
16. The power converting apparatus according to claim 9, further a drive circuit which comprises:
- a parallel circuit provided between a gate of said switching element and a control circuit, and
- said parallel circuit comprises:
- a resistor circuit having a higher resistance; and
- a series circuit connected in parallel to said resistor circuit and comprising a resistor having a lower resistance, and a diode connected with said resistor to block off a gate current on charging of said gate.
17. The power converting apparatus according to claim 9, wherein said switching element receives, at a gate thereof, a voltage from a control power supply of said power converting apparatus through a resistor and a diode.
18. The power converting apparatus according to claim 7, wherein said first and second condensers discharge to zero voltage once for one period of said AC power.
19. The power converting apparatus according to claim 1, further comprising:
- mechanical switches provided between a common node and said first condenser and between said common node and said second condenser.
20. A power converting apparatus comprising:
- a rectifying circuit having a pair of AC power input terminals and a pair of rectified voltage output terminals;
- a reactor; and
- a charging and discharging circuit connected between said rectified voltage output terminals,
- wherein said charging and discharging circuit comprises:
- a first charging and discharging circuit connected with one of said rectified voltage output terminals and one of said AC power input terminals; and
- a second charging and discharging circuit connected with the other of said rectified voltage output terminals and said one AC power input terminal,
- said first charging and discharging circuit comprises a first switch and a first condenser connected with said first switch in series,
- said second charging and discharging circuit comprises a second switch and a second condenser connected with said second switch in series,
- said reactor generates a resonance current together with said first condenser and said second condenser, and
- said second condenser discharges to zero voltage while said first condenser is charged.
21. The power converting apparatus according to claim 20, wherein capacitances of said first condenser and said second condenser and an inductance of said reactor are determined such that a resonance frequency is in a range of 3 times to 5 times of a frequency of AC power supplied to said AC power input terminals.
22. A power converting method comprising:
- connecting a rectifying circuit with an AC power supply;
- charging a first charging and discharging section which is connected between a first output terminal as one of two first output terminals of said rectifying circuit and one of two AC power input terminals of said rectifying circuit;
- discharging from a second charging and discharging section which is connected between a second output terminal as the other of the two first output terminals of said rectifying circuit and said one AC power input terminal in synchronization with said charging;
- charging said second charging and discharging section after a half period of said first charging and discharging period;
- discharging said first charging and discharging section in synchronization with said charging said second charging and discharging section;
- continuing to connect a terminal of said first charging and discharging section on a side of said AC electric power input terminals and a terminal of said second charging and discharging section on a side of said AC electric power input terminals during a rated operation; and
- intermittently opening the terminal of said first charging and discharging section on the side of said AC electric power input terminals and the terminal of said second charging and discharging section on the side of said AC electric power input terminals during a low load operation.
23. The power converting method according to claim 22, wherein said first charging and discharging section and said second charging and discharging section have condensers, respectively,
- a reactor is provided between said AC electrode input terminal and said rectifying circuit or between said rectifying circuit and said first charging and discharging section, and
- a maximum value of a current flowing from one of said first condenser and said second condenser to said one AC input terminal at a rated operation is substantially same as a maximum value of a rated input current.
24. The power converting method according to claim 22, wherein capacitances of said first condenser and said second condenser and an inductance of said reactor are determined such that a resonance frequency is in a range of 3 times to 5 times of a frequency of AC power supplied to said AC power input terminals.
25. The power converting method according to claim 22, said first charging and discharging section and said second charging and discharging section have condensers, respectively,
- a reactor is provided between said AC electrode input terminal and said rectifying circuit or between said rectifying circuit and said first charging and discharging section,
- a charging period of one of said first and second condensers and a discharging period of the other condenser are synchronized with each other, and
- said one condenser discharges to zero voltage after being charged.
26. The power converting method according to claim 25, wherein capacitances of said first condenser and said second condenser and an inductance of said reactor are determined such that a resonance frequency is in a range of 3 times to 5 times of a frequency of AC power supplied to said AC power input terminals.
Type: Application
Filed: Nov 1, 2005
Publication Date: May 4, 2006
Applicant: NEC ELECTRONICS CORPORATION (KAWASAKI)
Inventor: Youichi Ito (Yokohama)
Application Number: 11/262,806
International Classification: H02M 7/00 (20060101);