JP3329956B2 - Power conversion circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power conversion circuit which uses a switched capacitor to obtain power from a unipolar power supply whose voltage waveform changes into a pulsating waveform or a sine waveform with the passage of time.

[0002]

2. Description of the Related Art A configuration shown in FIG. 17 can be considered as a power conversion circuit that uses a switched capacitor to obtain AC power having a sinusoidal voltage waveform from a DC power supply. In this circuit configuration, a full-bridge type inverter circuit INV for alternating the direction of the current applied to the load Z, and an inverter circuit INV from the DC power supply DC.
And a switched capacitor for changing the voltage to be applied to the pulsating waveform over time.

A switched capacitor includes five switching elements S _j1 and five capacitors C _j , four switching elements S _j2 and four diodes D _j, and performs switching for turning on / off power supply from a DC power supply DC. It has an element _{S s.} Switching element S
_j1 and the capacitor C _j (j ≧ 1) are connected in series one by one, and the switching element S _j1 and the capacitor C _j (j ≧ 2)
The anode of the diode D _(j-1) is connected to one end on the capacitor _Cj side in each series circuit. The switching element S _j1 , the capacitor C _j and the diode D
The series circuit with _(j-1) (j ≧ 2) is the switching element S
_{(j-1) 1} and the capacitor C _(j-1) are connected in parallel. Furthermore, the switching element S _j1 is connected between the connection point of the capacitor C _j and the connection point of the switching element S _{(j-1) 1} and the cathode of the diode D _{(j-1).
(j-1) 2} is inserted. Series circuit of the switching element S ₁₁ and the capacitor C ₁ is connected to a DC power source via the switching element S _s in this configuration.

On the other hand, the inverter circuit INV is a full-bridge type as described above and has four switching elements S.
_zj (j = 1, 2, 3, 4) is bridge-connected. That is, two switching elements S _z1 and S _z4
Is connected in parallel with the series circuit of the two switching elements S _z2 and S _z3 , and the output voltage of the switched capacitor is applied to the parallel circuit composed of both series circuits. The switching elements S _z1 and S _z2 are connected in series via a load Z, and the switching elements S _z3 and S _{z3 are} connected in series.
S _z4 is connected in series via a load Z.

Next, the operation of the above-described power conversion circuit will be described. The operation of each unit in FIG. 17 is summarized in FIG. In the inverter circuit INV, the switching elements S _z1 and S _z2
Is turned on or the switching elements S _z3 and S _z4 are turned on, the direction of the current supplied to the load Z is reversed. That is, the power supply to the load Z can be alternated by alternately turning on and off two switching elements S _zj connected in series via the load Z. However, assuming that the output voltage of the switched capacitor is constant and the on / off time of the switching element _Szj is not changed, the voltage applied to the load Z is an alternating rectangular wave.

[0006] This type of power converter applies a voltage to a load Z.
Voltage V_z1The purpose is to make the waveform of the
Therefore, the voltage change with the passage of time
Is more realized. That is, with a switched capacitor
First, the switching element S _sAnd switching elements
S_j1Is turned on and the switching element S_j2Turn off.
Here, the switching element S_j1On-resistance and diode
D_jNeglecting the voltage effect of_jTerminal
The voltage is equal to the power supply voltage E of the DC power supply DC. However
And the switching element S_sDuring the ON period of the inverter
Switching element S of road INV_zjTurn off all.

Next, the switching element S_sTurn off,
Switching element S of inverter circuit INV_z1, S_z2Ma
Or switching element S_z3, S_z4Turn on. here
In the switched capacitor, the switching element S₅₁of
If you turn on only the capacitor C_FiveVoltage across
Applied to the inverter circuit INV.
The applied voltage is equal to the power supply voltage E of the DC power supply DC. Sa
Furthermore, without changing the inverter circuit INV,
Switching element S₅₁To turn off the switching element S
₄₁, S₄₂Is turned on, the capacitor C_Four, C_FiveIs in series
The inverter circuit INV is connected to the DC power supply DC.
A voltage that is twice the source voltage E is applied. At this time,
Code D_FourOf the cathode potential is equal to the power supply voltage E of the DC power supply DC
Equal to diode D_FourIs reverse biased and held off.
Dripping. Next, the switching element S ₄₁Turn off the switch
Switching element S₃₁, S₃₂Turn on the capacitor C_Three
~ C _FiveAre connected in series and applied to the inverter circuit INV.
The voltage becomes three times the power supply voltage E of the DC power supply DC, and
By performing such control, the inverter circuit INV
Applied voltage V_zRises step by step, and finally DC power DC
Power supply voltage E reaches 5 times. Then control in reverse order
Then, the applied voltage V to the inverter circuit INV _zThe stage
It can be lowered down. Like this
Voltage V applied to inverter circuit INV_zBetween the rise and fall
Switching element S_z1, S_z2And switching element S_z3,
S_z4By keeping only one of these ON, the load Z
Voltage V_z1Can be changed over time
You.

[0008] Then, turn off all the switching elements S _zj of the inverter circuit INV, with the switched capacitor to turn on all the switching elements S _j1, if you turn on the switching element S _s, the capacitor C _j again terminal The battery can be charged so that the voltage becomes the power supply voltage E of the DC power supply DC. Next, the turn off switching element S _s, the switching element S _z1 to S _z4 of the inverter circuit INV to the last off period of the switching element S _s and the relationship between on and off in the opposite,
By operating the switched capacitor as described above, the voltage V _z1 applied to the load Z can be changed with time with a polarity opposite to that of the previous off period of the switching element S _s .

By repeating the above operation as described above, the voltage V _z1 applied to the load Z can be changed stepwise with the passage of time with the width of the power supply voltage E of the DC power supply DC, and the polarity can be alternated. That is, the AC voltage can be applied to the load Z.

[0010]

As is apparent from the above description, since the voltage changes stepwise with the width of the power supply voltage E of the DC power supply DC in the above-described configuration, many harmonic components are included. In particular, when the load Z is a discharge lamp, this causes a discharge of harmonics from the discharge lamp. Further, when the voltage applied to the discharge lamp changes stepwise, the stress on the discharge lamp increases, which causes a problem that the life of the discharge lamp is shortened.

In order to solve these problems, it is required to smooth the change in voltage. To satisfy such a demand, the capacitor C of the switched capacitor is designed so that the change width of the voltage per one step becomes small. _Although it is conceivable to increase the number of _j , there is a problem that the number of parts is greatly increased and the cost is increased, and yet the voltage waveform cannot be completely continuous.

An object of the present invention is to provide a power conversion circuit capable of obtaining a completely continuous voltage waveform without significantly increasing the number of parts. is there.

[0013]

According to a first aspect of the present invention, a plurality of capacitors, a charging unit for charging each capacitor so that terminal voltages thereof are different from each other to a predetermined voltage, and a load unit are provided.
A load capacitor connected in parallel, an inductor connected in series to the load capacitor, a plurality of switching elements respectively inserted between a series circuit of the load capacitor and the inductor and each capacitor; And a control circuit for controlling the switching element so as to change the voltage between both ends of the load capacitor into a pulsating waveform by sequentially and selectively connecting the series circuit.

According to a second aspect of the present invention, the control circuit disconnects the capacitor connected to the series circuit at the first zero crossing point of the current passing through the inductor after connecting the capacitor to the series circuit of the load capacitor and the inductor. The switching element is controlled.
According to a third aspect of the present invention, the control circuit disconnects the capacitor connected to the series circuit at a point before the first zero crossing point of the current passing through the inductor after connecting the capacitor to the series circuit of the load capacitor and the inductor. The switching element is controlled as described above.

According to a fourth aspect of the present invention, the terminal voltage at the time of charging each capacitor by the charging unit is set so that the voltage across the load capacitor has a sine wave shape.
The invention of claim 5 is characterized in that the connection time of each capacitor by the switching element is controlled so that the voltage across the load capacitor has a sine wave shape. The invention according to claim 6 is characterized in that the capacitance of each capacitor is set such that the voltage across the load capacitor has a sine wave shape.

A seventh aspect of the present invention is characterized in that an inverter circuit for supplying alternating power to a load using a load capacitor as a power supply is provided. The invention according to claim 8 is characterized in that two sets of capacitor groups each including a plurality of capacitors, a charging unit that charges each capacitor constituting each capacitor group so that terminal voltages become predetermined voltages different from each other ,
A load capacitor connected in parallel, an inductor connected in series with the load capacitor, a plurality of switching elements respectively inserted between the series circuit of the load capacitor and the inductor and each capacitor, and each capacitor group By alternately connecting the capacitors constituting the capacitor group to the series circuit and connecting them alternately to the series circuit, the voltage at both ends of the load capacitor is changed into a form in which a pulsating waveform is alternated. And a plurality of switching elements.

According to a ninth aspect of the present invention, the load is a discharge lamp.

[0018]

According to the present invention, a plurality of capacitors are charged so that terminal voltages become predetermined voltages different from each other, and each capacitor is sequentially connected to a series circuit of an inductor and a load capacitor. Since the terminal voltage of the load capacitor is changed to a pulsating waveform or an alternating pulsating waveform, power is supplied to the load capacitor in a resonant manner using resonance between the inductor and the capacitor. It is possible to continuously change the voltage between both ends of the load capacitor. That is, the waveform of the voltage applied to the load in which the load capacitors are connected in parallel also becomes a smoothly continuous waveform, and the harmonic component of the load voltage waveform can be reduced. In particular, when the load is a discharge lamp, the radiation of harmonics from the lamp can be reduced, and the stress on the lamp is also reduced.

[0019]

【Example】

(Embodiment 1) In this embodiment, an example is shown in which a DC power supply is used as a power supply, and a voltage that changes into a pulsating waveform over time is applied to a load. As shown in FIG. 1, the power conversion circuit uses a switched capacitor, and includes a capacitor C _j , a switching element S _j1 , and a diode D
_{j (j = 1,2, ......,} 5) five series circuit comprising connected in parallel, as well as connected to a DC power supply DC to the parallel circuit via the inductor L ₁ and the switching element S _s, the capacitor C _j, five series circuits are connected in parallel to a switching element S _j2, having the configuration connecting the parallel circuit to the load Z via the inductor L _2. Also,
The series circuit of the DC power source and the switching element S _s connected in parallel a diode D _s, the load Z are connected in parallel load capacitor C _z. Both inductors L ₁ and L ₂
The power transmission efficiency is improved by transmitting the power in a resonant manner. Here, each switching element S _j1 ,
S _j2 and S _s are controlled by a control circuit (not shown) as described later. The control circuit monitors the terminal voltage of each capacitor C _j, during charging of each capacitor C _j and to stop charging reaches a predetermined terminal voltage set for each capacitor C _j. A MOSFET, a bipolar transistor, or the like is used for each of the switching elements S _j1 , S _j2 , and S _s, and has a predetermined on-resistance when turned on.

Next, the operation of the circuit shown in FIG. 1 will be described with reference to FIG.
It will be described in the light of the above. 2 (a) to 2 (k) each switching
Element S_j1, S_j2, S_sAbout the operation of the shading period
It indicates ON, and the other periods indicate OFF. First, FIG.
Time t as in (b)₀In the switching element S_s
And switching element S₁₁Only turn on. Capacity
Sita C₁Is the switching element S_s, Inductor L₁,
Diode D₁, Switching element S₁₁Charged via
As shown in FIG.₁Terminal voltage V_C1
Is time t₁And V_TenThe switching element S_sTo
Switching element S while being kept on₁₁Turn off
You. After that, as shown in FIG._{twenty one}
Turn on the capacitor C_TwoTerminal voltage V_c2Is time t_Two
And V₂₀(> V_Ten) Until capacitor C_TwoCharge
You. Similarly, as shown in FIGS.
Ching element S_j1Are sequentially turned on and each capacitor C_jEnd of
Child voltage V_cjIs a predetermined set value V_Ten, V₂₀, V₃₀,
V₄₀, V₅₀(V_Ten<V₂₀<V ₃₀<V₄₀<V₅₀)
Sea Capacitor C_jCharge. However, the capacitor
C_FiveAs shown in FIGS. 2A, 2F, and 2L,
And the capacitor C_FiveTerminal voltage is V₅₀Just before reaching
Time t₄₁Switching element S_sBy turning off
Nacta L₁, Diode D_Five, Switching element
S₅₁, Capacitor C_Five, Diode D_sOn the route,
Dacta L₁The battery is charged using the stored energy. The above
Thus, using a single DC power supply DC, each capacitor
C_jAre different terminal voltages V_cjCan be charged
it can. Here, each capacitor C_jIs the inductor L₁To
Charge through the power supply, reducing power transfer losses
can do.

On the other hand, the load Z is supplied to the
Sita C_jPower is supplied in order from. That is, the time t₁In
And capacitor C₁As soon as the charging of
As shown in (g), the switching element S₁₂Turn on
And the capacitor C₁From inductor L_TwoThrough the load for
Capacitor C_zAnd load Z. Capacitor C
₁When power is supplied to the load Z from the
TA C_zParallel circuit and inductor L_TwoAnd capacitor C₁
Form a resonance circuit, and the inductor L_TwoFigure 2
Resonant current I as shown in (n)₁Will flow. did
Therefore, as shown in FIG._zEnd of
Child voltage V_zRises resonantly and the capacitor C ₁Terminal power
The pressure drops as shown in FIG. Now, load Z
Impedance is sufficiently high and capacitor C₁And load key
Japashita C_zIf the capacity of the load
Pasita C_zTerminal voltage V_zIs the capacitor C₁About
Fixed terminal voltage V_TenTo a voltage close to
Japashita C₁Terminal voltage V_c1Is the load capacitor C_zof
Original terminal voltage V_z(= 0V)
You. The load capacitor C_zTerminal voltage V_zBut almost
V_Ten, Then the load capacitor C_zIs discharged
And the capacitor C₁Is charged. Therefore, the load
Pasita C_zTerminal voltage V_zHas almost reached its peak
(Time t_Two) And the switching element S₁₂Turn off. Time
Time t_TwoThen capacitor C_TwoSince the charging of
As shown in FIG._{twenty two}Turn on
You. At this time, the capacitor C_Two, Inductor L_Two,load
Capacitor C_zAnd the load Z forms a resonance circuit.
The capacitor C_TwoAnd load capacitor C
_zIs approximately equal, the time t_ThreeFigure 2
Load capacitor C as in (m)_zTerminal voltage
Pasita C_TwoTerminal voltage V set for₂₀Up to near
As shown in FIG. 2 (l), the capacitor C_TwoTerminal voltage V
_c2Is the load capacitor C_zOriginal terminal voltage V_TenTo near
Descend. If the above operation is repeated one after another, FIG.
Load capacitor C_zTerminal voltage V_zRises sequentially
And time t₆Has a load capacitor C_zTerminal voltage V
_zIs the capacitor C_FiveTerminal voltage V set for
₅₀Rise to near.

The idea continues to turn on the switching element S ₅₂ so that the load capacitor C _z FIG even after reaching nearly peak at the terminal voltage V _z the time t ₆ of 2 (l), FIG. 2
Resonance current I ₁ in the opposite direction to flow through the inductor L ₂ as (n), the terminal voltage of the load capacitor C _z is 2
It gradually descends as in (l). Load capacitor C _z
Since the terminal voltage decreases at time t ₈ to the vicinity of V _40, while turning off the switching element S ₅₂ at this time,
The switching element _S42 is turned on as shown in FIG. The terminal voltage V _c4 of the capacitor C ₄ is at this point V ₃₀
And the terminal voltage V _z of the load capacitor C _z is close to V ₄₀ , so that a resonance current I ₁ flowing from the load capacitor C _z to the capacitor C ₄ flows as shown in FIG.
With the terminal voltage V _z of the load capacitor C _z is reduced to near V _30, the terminal voltage V _c4 of the capacitor C ₄ is V ₄₀
Rise to near. Thus, the switching element S _j2
Are sequentially turned on, and the terminal voltage V _z of the load capacitor C _z is turned on.
, And finally the terminal voltage V _z of the load capacitor C _z can be reduced to almost 0V.
Here, the timing of turning off each switching element S _j2 is determined by detecting the zero cross point of the resonance current I ₁ .

As described above, the switching element S_j1,
S_j2, S_sIs controlled, the capacitor C _j, Inductor
L_Two, Load capacitor C_zFlows into a resonant circuit consisting of
Resonant current I₁By using, as shown in FIG.
Loading capacitor C_zTerminal voltage V _zChange smoothly
Can be If the load Z is resistive, the load
Style I_TwoIs a load capacitor C as shown in FIG._zEnd of
Child voltage V_zChanges smoothly in proportion to
Load current I flowing through_TwoHarmonic distortion can be reduced
You. Here, the resonance frequency of each resonance circuit described above is determined by the load
Capacitor C_z(T) at which the voltage across the₀~ T
₁₁) Is higher than the frequency equivalent to
C_jAnd inductor L₁, L_TwoTime constant determined by
Can be set smaller. Moreover, the inductor L_Two
Is equal to the potential difference between adjacent capacitors C_j, C_{(j + 1)}
(For example, V₅₀-V₄₀)
From the load capacitor C_zTerminal voltage peak value (V₅₀
Level), compared to the voltage applied to the load Z.
A low withstand voltage type can be used. In addition,
L₁, L_TwoSince power is transmitted through
Compared to a regular switched capacitor that does not use
High efficiency.

Furthermore, in the above arrangement, within one cycle of the terminal voltage V _z of the load capacitor C _z is changed, before performing the charge and discharge between the respective capacitors C _j and the load capacitor C _z, each among (1 cycle period t ₀ ~t ₁₁ by doing the charging from the DC power source to the capacitor C _j, the capacitor C ₁ time t ₁ earlier, the capacitor C
The ₂ time t ₂ previously to the time t ₁₀ after the capacitor C
Time t ₃ before to the time t ₉ after the _3, capacitor C
Time t ₄ prior to the time t ₈ after the _4, the capacitor C
The ₅ time t ₅ previous to time t ₇ after), it is possible to substantially symmetric voltage waveform at the time and falling time of rise of the terminal voltage V _z of the load capacitor C _z.

[0025] As described above, while using a single DC power source in this embodiment, to charge a plurality of capacitors C _j so that the terminal voltage V _cj are different, each capacitor C _j
From the load capacitor C _z via the inductor L ₂ sequentially.
Is charged, and power is supplied to the load Z connected in parallel to the load capacitor _Cz , so that the voltage applied to the load Z can be smoothly changed over time. As is clear from the above description, the DC power supply DC,
The switching section S _s , S _j1 , inductor L ₁ , diode D _j , and control circuit constitute a charging section.

(Embodiment 2) In the present embodiment, the timing for turning off each switching element _Sj2 is different from that in Embodiment 1 for the same circuit configuration as in Embodiment 1. In the first embodiment, as shown in FIG. 3A, each switching element S _{j2 is} at a zero cross point of the resonance current I ₁ flowing through the inductor L _1.
Since the off, as in the terminal voltage V _z of the load capacitor C _z FIG. 3 (b), rising due to the charging of the capacitor C _j (or discharge of the capacitor C _j) (or descending) approximately After stopping, the next capacitor C
_{(j + 1)} (or the capacitor C _(j-1) ). In this case, the rate of increase (or the rate of decrease) of the terminal voltage V _z of the load capacitor C _z changes abruptly when the switching element S _j2 is switched.

Therefore, in this embodiment, as shown in FIG. 4A, the switching element S _j2 is turned off before the zero cross point of the resonance current I ₁ , and the next capacitor C _{(j + 1)} is turned off.
(Or the capacitor C _(j-1) ) to perform charging (or discharging), thereby increasing the rate of rise (or fall) of the terminal voltage V _z of the load capacitor C _z as shown in FIG. That is, a sudden change at the time of switching of the switching element _Sj2 is suppressed, and the voltage waveform is further smoothed. That is, the ON / OFF of the switching element S _j2
If the OFF timing is controlled as in the present embodiment, harmonic distortion can be further suppressed as compared with the first embodiment.
Other configurations and operations are the same as those of the first embodiment.

(Embodiment 3) This embodiment relates to a load capacity.
TA C_zIn this example, the terminal voltage of
Therefore, in the first embodiment, each capacitor C_jFrom DC power supply DC
Terminal voltage V when charging_cjSet value of V₂₀-V_Ten≒ V₃₀−
V₂₀≒ V₄₀-V₃₀≒ V₅₀-V₄₀Is set to
However, in this embodiment, V₂₀-V_Ten> V₃₀-V₂₀> V₄₀-V
₃₀> V₅₀-V ₄₀It is set to be.

Each capacitor C_jTerminal voltage V_cjThe above
In order to set such a relationship, in this embodiment, the load capacity is set.
Pasita C_zTerminal voltage V_zIs shown by a solid line in FIG.
Period is equal to the target waveform
Threshold waveform (shown by a dashed line in FIG. 5)
Based on each capacitor C_jTerminal voltage V to be reached _z
And the control circuit sets the set terminal voltage V_cjWill be
Sea Capacitor C_jAdjust the charging time.
For example, the capacitor C_TwoTerminal voltage V_c2Is the time t_Two
In FIG. 5, the time t of the waveform shown by the dashed line in FIG._ThreeElectricity in
It must be under pressure. Also, the capacitor C_FiveEnd of
Child voltage V_c5Is the time t_FiveNow, the wave indicated by the dashed line in FIG.
It is set to reach the peak value of the shape. Capacitor C
_jTerminal voltage V_zIs set as described above,
Pasita C_jAnd load capacitor C _zBetween charge and discharge
The switching element S_j2ON / OFF timing
While applying substantially equal time intervals,
Can be changed to a substantially sinusoidal shape.

Here, the amplitude is larger than the target waveform.
Capacitor C based on the large waveform of_jTerminal voltage V_cj
Is determined by the load key due to the power consumption at the load Z.
Japashita C_zTerminal voltage V_zCompensation for descent
To do so. Also, by adopting this setting,
As in Embodiment 2, the resonance current I₁Before the zero crossing point of
Switching element S_j2Control to switch
Also, load capacitor C _zTerminal voltage V_zTo the target value
You can. As described above, the capacitor C_j
Terminal voltage when charging from DC power supply DC_cjIs mentioned above
The load capacitor C_zTerminal voltage
V_zCan be changed to a sine wave shape, and the load Z
Harmonic distortion of applied voltage and current can be further reduced.
You can. Other configurations and operations are the same as those of the first embodiment.
is there.

(Embodiment 4) This embodiment is also similar to Embodiment 3.
Load capacitor C_zTerminal voltage V_zTo a sine wave shape.
The control method is different from that of the third embodiment.
Are different. That is, in the third embodiment, each pair
Capacitor C_j, C_{(j + 1)}Terminal voltage V _j, V_{(j + 1)}
Were made different, but in the present embodiment, the difference shown in FIG.
Using a circuit configuration similar to that of the first embodiment, each pair of adjacent keys is used.
Japashita C_j, C_{(j + 1)}Terminal voltage V_j, V_{(j + 1)}Difference
Is substantially constant as in the first embodiment, and each capacitor C_jWhen
Load capacitor C_zEach switching element provided between
Child S_j2By controlling the ON period of the
The load capacitor C_zTerminal voltage V_zThe sine waveform
It changes in shape. Here, each capacitor C_jof
Terminal voltage V_cjThe method of setting the target value is the same as in the third embodiment.
First, as shown by the solid line in FIG.
_zTarget terminal voltage V_zThe amplitude of the waveform
The waveform as shown by the dashed line in FIG.
Each time t on the waveform_Two, T_Three, T_Four, T_Five, T₆In
Each capacitor C_jTerminal voltage V_cjIf you decide the target value of
Good.

In the configuration of the third embodiment, the terminal voltage V _cj of each capacitor C _j is different, and the change width of the voltage in the time width for switching the switching element S _j2 is larger on the low voltage side than on the high voltage side. since it is, the potential difference across the inductor L ₂ is increased, it becomes necessary to use a high breakdown voltage than in example 1 as an inductor L _2. On the other hand, in the configuration of the present embodiment, the width of change of the voltage in the time width for switching the switching element S _j2 is substantially constant (ie, the terminal voltage between the adjacent capacitors C _j and C _{(j + 1 )).} V _j , V _{(j + 1)} is constant), inductor L ₂
The potential difference between both ends can be kept substantially constant, it is possible to use those results in low breakdown voltage at the same level as in Example 1 as an inductor L _2. Other configurations and operations are the same as those of the first embodiment.

(Embodiment 5) In this embodiment, similarly to Embodiments 3 and 4, the terminal voltage _Vz of the load capacitor _{Cz is formed} into a sine wave shape using the same configuration as that of Embodiment 1 shown in FIG. To change it. Therefore, capacitors C _j having different capacities are used (C ₁ <C ₂ <C ₃ <
C ₄ <C _5). That is, for the capacitor C _j that is connected to the load capacitor C _z, the load capacitor C _z
Are connected during a period in which the terminal voltage _Vz is low, the capacitance is reduced. Therefore, the resonance frequency in the period in which the respective capacitors C _j and the load capacitor C _z are connected to a than would be changed for each capacitor C _j, high terminal voltage V _z of the load capacitor C _z In the period, a sinusoidal voltage waveform is obtained by lowering the resonance frequency and making the voltage change gradual.
Conversely, during a period in which the terminal voltage of the load capacitor _Cz is low, the resonance frequency increases and the voltage changes quickly. Other configurations and operations are the same as those of the first embodiment.

(Embodiment 6) In this embodiment, as shown in FIG. 7, a full-bridge type inverter circuit INV similar to that described in the prior art is employed as the load Z. That is, the four switching elements S _{z1 to} S _z4 are bridge-connected, and the two switching elements S _z1 and S _z2 (S _z3 and S _z4 ) connected in series via the load Z are simultaneously turned on and connected in series with each other. Switching elements S _z1 , S
By alternately turning on and off _z4 ( _Sz3 , _Sz2 ), an alternating current flows through the load Z. This type of inverter circuit INV is well known,
By using such an inverter circuit INV as the load Z having the configuration of the fifth embodiment, a sinusoidal AC voltage can be applied to the load Z.

(Embodiment 7) In this embodiment, as shown in FIG. 8, a series circuit of _a capacitor C _a , a switching element S _a1 , a diode D _a1 and a capacitor C _a are arranged in parallel with the configuration of the first embodiment. The two connected switching elements S _a2 ,
It has a configuration in which a series circuit of _Sa3 and a diode _Da2 is added. The series circuit of the capacitor C _a , the switching element S _a1 , and the diode D _a1 is connected in parallel to the series circuit of the capacitor C ₃ , the switching element S ₃₁ , and the diode D ₃ , and the series circuit of the switching element S _a3 and the diode D _a2 is It is inserted between one ends of the capacitors C ₂ and C ₃ .
The diode D _a2 is a cathode connected to one end of the capacitor C _2.

This configuration is equivalent to the load capacitor C_zThe pea
Set the power supply voltage higher than the power supply voltage E of the DC power supply DC.
And a capacitor C_jOut of
Japashita C_Three~ C_FiveWhen charging from the DC power source DC,
Capacitor C_aTerminal voltage V _caBy adding
Pasita C_jTerminal voltage V_cjIs the power supply voltage E of the DC power supply DC.
So that it can be higher. Capacitor C_aNitsu
Is the terminal voltage V_caTo V_a0Is set to Based on FIG.
Then, the operation will be specifically described. First, as shown in FIG.
Time t ₁In the switching element S_sTurn on
In the state in which the switching element S is switched as shown in FIG.₁₁To
Turn on the capacitor C₁Charge. Also switch
Element S₁₁At time t_ThreeTime t immediately before turning off_TwoTo
Here, as shown in FIG._{twenty one}On
And capacitor C_TwoCharge. Next, switching
Element S_{twenty one}At time t_FiveTime t immediately before turning off_Foursmell
As shown in FIG. 9D, the switching element S₃₁On
And at the same time, as shown in FIG.
S_a2Also turn on. Here, the capacitor C_aAlready
If it is, the capacitor C_aTerminal voltage V_a0
Is added to the power supply voltage E of the DC power supply DC.
Is the capacitor C_ThreeWill be applied. That is,
Capacitor C_ThreeTerminal voltage V_c3Higher than the power supply voltage E
It becomes possible to do. After that, switching in the same way
Element S_a29 (e) and 9 (f), while
As shown, the switching element S₄₁, S₅₁Turn on in order
And the capacitor C_Four, C_FiveTerminal voltage V_c4, V_c5Is power
Charge until voltage becomes higher than voltage E. In this way, Sui
Switching element S_j1Part of the ON period of
Therefore, the inductor L ₁A pause occurs in the current flowing through
I do not have it.

The capacitor C_FiveTerminal voltage V_c5Gaho
Set value V₅₀Time t just before _TenIn FIG.
Switching element S as in (i)_a3Turn on the
Pasita C _aFrom capacitor C_FiveTo stop discharging. This
, The inductor L₁The energy stored in is released
The capacitor C_FiveCharging continues
You. Next, as shown in FIG.₁₁At the switch
Ching element S_a2Is turned off, and as shown in FIG.
Time t₁₂In the switching element S_a1Turn on
And the capacitor C_aIs charged by the DC power supply DC.
Thereafter, as shown in FIG.₁₃Switching element
Child S₅₁Turn off the capacitor C_FiveEnd charging.

Next, turning off the switching element S _s at time t ₁₄ as shown in FIG. 9 (a), the inductor L ₁ stored energy of the inductor L _1, diode D _a, the switching element S _a1, capacitor C _a , Switching element S
_a3, diode D _a2, released a path of the diode D _s, the capacitor C _a is charged by the energy. In this way, the energy stored in the inductor L ₁ is eliminated, to turn off the switching element S _a1, S _a3.

As described above, each switching element S _j1
By controlling the _{S a1, S a2, S a3} , FIG 9 (j)
As shown in, it is possible to obtain the capacitor C _j, the C target terminal voltage set respectively for _{a V 10 ~V 50, V a0} . Thus, as shown in the first embodiment and the like, the switching element S _j2 is controlled and each capacitor C _j is controlled.
By connecting via the inductor L ₂ to the load capacitor C _z to _j, the capacitor C _z terminal voltage V
_z can be changed over time. Other configurations and operations are the same as those of the first embodiment.

(Embodiment 8) This embodiment is shown in FIG.
As described above, in the configuration of the first embodiment,
Capacitor C_sIs used. This capacitor
C_sIs the load capacitor C_zOf the voltage change every cycle
Charged. In addition, each of the components constituting the switched capacitor
Capacitor C_jIs the terminal voltage V in the first embodiment._cjLow
Are charged in the order of
However, in this embodiment, the terminal voltage V _cjFrom high to low
The battery is charged in order. Here, the capacity
Sita C_jC before starting charging_sTerminal
Voltage V_csIs the terminal voltage V_cjIs set to the highest
Japashita C_FiveTerminal voltage V_c5Set value V₅₀Higher than
It has been set.

In the configuration of the first embodiment, as shown in FIG.
All the capacities that make up the switched capacitor
TA C_jWas charged with the power supply voltage E,
Sita C_jTerminal voltage V_cjV between power supply voltage E and_ejIs
Japashita C_jTerminal voltage V_cjIs set lower
(V_e1> V_c2> V_c3> V_c4> V_c5).
As a result, the voltage difference V_ejThe greater the loss during charging
Was increasing. In contrast, in the present embodiment, the capacity is
Sita C_sBy the capacitor C_jAnd charge the terminal
Pressure V_cjIs the highest set capacitor C_FiveFirst
To the terminal voltage V in order._cjIs set lower
TA C_jIs charged, as shown in FIG.
Japashita C_jAs the charging of the capacitor progresses_sof
Terminal voltage V_csThe capacitor C_jOpen charging
Both capacitors C at the beginning_s,C _jTerminal voltage V_cs, V
_cjDifference V_sjChange becomes small. That is, the charging current
The peak value can be suppressed, and the circuit efficiency is improved.
Other configurations and operations are the same as those of the first embodiment.

[0042] (Example 9) In this embodiment, as shown in FIG. 12, instead of the capacitor C _j, is obtained using a switched capacitor SC _j of the configuration shown in FIG. 13. Each switched capacitor SC _j, a plurality of capacitor C
_jn (j = 1, 2,..., 5, x = 1, 2,...) and a switching element S _j1 inserted between one end of each of the pair of capacitors C _{j (n−1)} and C _{jn. (n-1),} each pair of capacitors C _{j (n-1),} and C _jn respectively inserted switching element between the other end of the S _{j3 (n-1),} the one end and the capacitor C of the capacitor C _jn and a switching element S _{j2 (n-1)} inserted between the other end of _{j (n-1)} .
This switched capacitor SC _j is configured to change the terminal voltage of the switched capacitor SC _j between charging and discharging.

That is, each switched capacitor SC _j
Is set lower than the power supply voltage E of the DC power supply DC, the switching element _{Sj2 (n-1)} is turned on and the switching elements _{Sj1 ( n-1)} and _{Sj3 (n- 1)}
Is turned off, the capacitor C _jn is connected in series, and at the time of discharging, the switching element S _{j2 (n-1)} is turned off and the switching elements S _{j1 (n-1)} and S _{j3 (n-1)} are turned on. C _jn may be connected in parallel. In this case, _assuming that the terminal voltage at the time of charging of the switched capacitor SC _j is V _j0 , the terminal voltage at the time of discharging becomes V _j0 / n.

On the other hand, the switching element S _j1 together to set higher than the power supply voltage E of the DC power source DC terminal voltage of each switched capacitor SC _j turns off the switching element S _{j2 (n-1)} to _{( n-1)} and S _{j3 (n-1)} are turned on and the capacitor C _jn is connected in parallel. During discharging, the switching element S _{j2 (n-1)} is turned on and the switching elements S _{j1 (n-1)} and S _{j1 (n-1)} are turned on. S _{j3 (n-1)} may be turned off and the capacitor C _jn may be connected in series. In this case, _assuming that the terminal voltage at the time of charging of the switched capacitor SC _j is V _j0 , the terminal voltage at the time of discharging becomes n · V _j0 .

As described above, each switched capacitor S
By appropriately controlling C _j , the terminal voltage of the switched capacitor SC _j can be set in a wide range, and the voltage applied to the load Z is variously set according to the purpose while using a single DC power supply DC. It becomes possible. Other configurations and operations are the same as those of the first embodiment. (Example 10)
In this embodiment, as shown in FIG. 14, with respect to the configuration of Embodiment 1, a configuration obtained by adding the switching element S _t connected in parallel to the series circuit of the inductor L ₁ and the diode D _s. In this circuit configuration, when switching at an appropriate frequency of the switching element S _s leave off the switching element S _t, the switching element S _s, inductor L _1, diode D _s, to function as a step-down chopper circuit composed of the capacitor C _j The switching element S _s is turned on and the switching element S _t is turned on.
Is switched at an appropriate frequency, the switching element _St , the inductor L ₁ , the diode D _j , the capacitor C
_j can function as a boost chopper circuit.

Therefore, according to the above configuration, each capacity
Sita C_jTerminal voltage V when charging _cjIs set to DC
If it is lower than the power supply voltage E of the source DC, the step-down chopper
Capacitor C by functioning as a circuit_jCharging power
Voltage lower than the power supply voltage E, and the terminal voltage V_cjIs set to
When the voltage is higher than the source voltage E,
Capacitor C_jCharging voltage to the power supply
The pressure can be raised above the pressure E. Like this
Using a pressure chopper circuit or a boost chopper circuit
Sita C_jBy charging the negative electrode, the negative
It is possible to set the voltage applied to the load Z in a wide range.
And the switching power supply can also
Loss can be reduced. Other configurations and operations are examples.
Same as 1.

(Embodiment 11) As shown in FIG. 15, this embodiment has a configuration in which the switching element S _s , diodes D _s and D _j , and inductor L ₁ are omitted from the configuration of the first embodiment. That is, when charging the respective capacitor C _j is charged not through the inductor L _1, so that the terminal voltage V _cj of the capacitor C _j to a desired set value only by controlling the ON period of the switching element S _1j To charge.
Other configurations and operations are the same as in Example 1, smaller, lighter is facilitated by omitting the inductor L _1.

(Embodiment 12) This embodiment relates to an inverter circuit.
Load Z using only switched capacitor without using path
Is to apply an AC voltage to the
As shown in FIG._jWhat is
A configuration to add a reverse current to the load Z
It is. The diode D_sHas a switching element S
_uAre connected in series. Capacitor C_jThe opposite direction
The configuration for flowing the current to the load Z includes a capacitor C_j
A plurality of capacitors C_k(K = 6,7, ... 1
0) is adopted. That is, two sets of keys
A plurality of capacitors C in each capacitor group_j, C
_KIs used. Each capacitor C_kHas diode D_k
And switching element S_k1Connected in series, and
Code D_kAnd switching element S_k1Separate from the switch
Element S_k2Are connected in series. Capacitor C _kAnd da
Iod D_kAnd switching element S_k1Series circuit with
The parallel circuit is connected in parallel with the DC power supply DC.
Switching element S_sIs connected in parallel to the series circuit. Ma
The capacitor C_kAnd switching element S_k2Series times with
Paths are connected in parallel with each other, this parallel circuit
₁And load capacitor C_zConnected in parallel with the series circuit
You.

The operation of charging the DC power source to the capacitor C _j is the same as in Example 10, keeping the switching element S _t off, turning on the switching element S _u, by switching at an appropriate frequency of the switching element S _s serves as a place step-down chopper circuit, a capacitor C _j can be charged to a voltage lower than the power supply voltage E of the DC power source DC, also keeping the switching element S _s, the S _u on the appropriate frequency of the switching element S _t , The capacitor _Cj can function as a boost chopper circuit and charge the capacitor _Cj with a voltage higher than the power supply voltage E.

On the other hand, the capacitor C_kFrom DC power supply DC
To charge, the switching element S _tKeep on
Switching element S_sAt the appropriate frequency
You. By this operation, the switching element S_s, Indah
Kuta L₁, Capacitor C_k, Diode D_kInversion by
Used as a chopper circuit (also called a buck-boost chopper circuit)
Works, switching element S_sWhen the inductor L is off₁
Capacitor C by the stored energy of_kCharging
Can be. The switching element S_sSwitching
The frequency of the capacitor C_jThe power
It can be charged with a lower or higher voltage than the voltage E
Wear.

With the above configuration, the capacitor C
_jFrom the top to the bottom with respect to the load Z in FIG.
And the capacitor C_kFrom the load Z
Thus, a current can be made to flow upward from the bottom in FIG.
That is, the direction of the current is alternated with respect to the load Z.
And inductor L_TwoAnd load capacitor C _z
As a result, a current flows resonantly to the load Z,
A smoothly changing AC voltage can be applied to the load Z
Because Other configurations and operations are the same as in the first embodiment.
You.

(Embodiment 13) This embodiment intends to apply an AC voltage to a load Z only by a switched capacitor in the same manner as the embodiment 12, and a series circuit of a pair of capacitors is connected in parallel to a DC power supply DC. By connecting, a configuration is adopted in which the power supply voltage E of the DC power supply DC is divided and two sets of switched capacitors are charged using each capacitor as a power supply. That is, the switched capacitor has the same configuration as that of the twelfth embodiment. However, instead of charging the capacitor C _k through the inverting chopper circuit, the DC power supply DC is connected to the cathode side of the diode D _k via the inductor and the switching element. Is connected to the negative electrode. One end of the common connection between the capacitors C _j and C _k is connected to a connection point between the two capacitors that divides the power supply voltage E.

In the configuration described above, the capacitors C _j and C _k are charged from the respective capacitors that divide the power supply voltage E of the DC power supply DC, and the capacitors C _j and C _k are connected in common. Because one end is connected to the connection point of the capacitor for voltage division,
As a result, the capacitor C _j and the capacitor C _k flow a current in the opposite direction to the load Z at the time of discharging, so that the AC voltage whose voltage smoothly changes with respect to the load Z is similar to the twelfth embodiment. It can be applied. Other configurations and operations are the same as those of the first embodiment.

The switched capacity described in each of the above embodiments
Capacitor C that constitutes the capacitor_j, C _kThe number of
It is not specified, and if necessary,
It may be less or more. However, the capacitor
C_j, C_kThe more the number of
And the adjacent capacitor C_j,
C_{(j + 1 )}, C_k, C_{(k + 1)}Terminal voltage difference becomes smaller
From inductor L_TwoIt is necessary to use a material with low pressure resistance for
it can. By using the power conversion circuit described above,
Even if the load Z is a discharge lamp, it is radiated from the lamp
Voltage waveform applied to lamp with less harmonics
Has a sinusoidal shape, which reduces stress on the lamp.
The lamp life is extended.

[0055]

According to the present invention, a plurality of capacitors are charged so that their terminal voltages become predetermined voltages different from each other, and each capacitor is sequentially connected to a series circuit of an inductor and a load capacitor. As a result, the terminal voltage of the load capacitor is changed to a pulsating waveform or an alternating pulsating waveform, and power is supplied to the load capacitor resonantly using resonance between the inductor and the capacitor. Therefore, it is possible to continuously change the voltage between both ends of the load capacitor. That is, the waveform of the voltage applied to the load in which the load capacitors are connected in parallel also becomes a smoothly continuous waveform, and the harmonic component of the load voltage waveform can be reduced. In particular, when the load is a discharge lamp, the radiation of harmonics from the lamp can be reduced, and the stress on the lamp is also reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment.

FIG. 2 is an operation explanatory diagram of the first embodiment.

FIG. 3 is an operation explanatory diagram of the first embodiment.

FIG. 4 is an operation explanatory diagram of the second embodiment.

FIG. 5 is an operation explanatory diagram of the third embodiment.

FIG. 6 is an operation explanatory diagram of the fourth embodiment.

FIG. 7 is a circuit diagram showing a sixth embodiment.

FIG. 8 is a circuit diagram showing a seventh embodiment.

FIG. 9 is an operation explanatory diagram of the seventh embodiment.

FIG. 10 is a circuit diagram showing an eighth embodiment.

FIG. 11 is an operation explanatory diagram of the eighth embodiment.

FIG. 12 is a circuit diagram showing a ninth embodiment.

FIG. 13 is a main part circuit diagram of a ninth embodiment.

FIG. 14 is a circuit diagram showing a tenth embodiment.

FIG. 15 is a circuit diagram showing an eleventh embodiment.

FIG. 16 is a circuit diagram showing a twelfth embodiment.

FIG. 17 is a circuit diagram showing a conventional example.

FIG. 18 is an operation explanatory diagram of a conventional example.

[Explanation of symbols]

C ₁ -C ₁₀ capacitor C _s capacitor C _z load capacitor D ₁ to D ₁₀ diodes D _s diode DC DC power supply INV inverter circuit S ₁₁ to S ₁₀₁ switching elements S ₁₂ to S ₁₀₂ switching elements L ₁ inductor L ₂ inductor Z load

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-190288 (JP, A) JP-A-60-82061 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02M 7/48 H02M 3/07

Claims (9)

(57) [Claims] 1. A plurality of capacitors, a charging unit for charging each capacitor so that terminal voltages thereof are different from each other to a predetermined voltage, and a load capacitor connected in parallel to a load.
An inductor connected in series to the load capacitor, a plurality of switching elements inserted between the series circuit of the load capacitor and the inductor and each of the capacitors, and each of the capacitors being sequentially selected in the series circuit. And a control circuit for controlling the switching element so as to change the voltage between both ends of the load capacitor into a pulsating waveform by connecting the power conversion circuit. 2. A control circuit controls a switching element to disconnect a capacitor connected to the series circuit at a first zero crossing point of a passing current of the inductor after connecting the capacitor to the series circuit of the load capacitor and the inductor. The power conversion circuit according to claim 1, wherein: 3. The control circuit according to claim 1, wherein the control circuit disconnects the capacitor connected to the series circuit at a point before the first zero crossing point of the current passing through the inductor after connecting the capacitor to the series circuit of the load capacitor and the inductor. The power conversion circuit according to claim 1, wherein the power conversion circuit controls a switching element. 4. The power conversion circuit according to claim 1, wherein the terminal voltage at the time of charging each capacitor by the charging unit is set so that the voltage across the load capacitor has a sine wave shape. 5. The power conversion circuit according to claim 1, wherein the connection time of each capacitor by the switching element is controlled so that the voltage across the load capacitor has a sine wave shape. 6. The power conversion circuit according to claim 1, wherein the capacitance of each capacitor is set such that the voltage across the load capacitor has a sine wave shape. 7. The power conversion circuit according to claim 1, further comprising an inverter circuit that uses the load capacitor as a power supply and supplies alternating power to the load. 8. A capacitor unit comprising a plurality of capacitors each having a plurality of capacitors, a charging unit for charging each of the capacitors constituting each of the capacitor groups so as to have predetermined terminal voltages different from each other, and a parallel connection to a load. A load capacitor, an inductor connected in series with the load capacitor,
A plurality of switching elements respectively inserted between a series circuit of a load capacitor and an inductor and each capacitor, and each capacitor group is alternately connected to the series circuit, and each capacitor constituting each capacitor group is connected. A power conversion circuit, comprising: a plurality of switching elements that are connected to the series circuit in order to change the voltage between both ends of the load capacitor in an alternating pulsating waveform. 9. The power conversion circuit according to claim 1, wherein the load is a discharge lamp.