JPH10201245A - Power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power converter capable of impressing a given voltage of almost continuous waveform to a load without using an element of high withstand voltage or making the efficiency in converting power reduced. SOLUTION: A first power supply part 2a, which outputs the pulsating voltage of staircase form, and a second power supply part 2b, which reverses polarity every cycle of the output voltage waveform of the first power supply part 2a, are provided. The output of the second power supply part 2b is impressed to a load 3 via a leakage transformer T1 with a capacitor C4 connected parallel to its primary winding. The leakage constituent of the leakage transformer T1 and the capacitor C4 constitute a filter, and only the fundamental wave constituent of the second power supply part 2b is transformed by the leakage transformer T1 and impressed to the load 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter which can apply a required voltage and an almost continuous waveform AC voltage to a load by using a power supply unit for generating a discontinuous waveform AC voltage. Things.

[0002]

2. Description of the Related Art The present inventor has conventionally proposed a power conversion device for converting power from DC to AC by using a switched capacitor and an inverter circuit together. FIG. 17 shows a basic circuit configuration of this type of power converter. The switched capacitor, is shown what with three capacitors C ₁ -C _3. Also,
Between the positive electrode and the capacitor C ₁ of the DC power source E and insert the charging switching element S _1, a capacitor C _2, C ₃ and the charge switching element S ₂ ~ respectively between each electrode of the DC power source E It is inserted into the S _5. Further, each of the capacitors C _{1 to} C ₃ and the charging switching elements S ₁ , S ₂ , S
₄ the discharging switching element S ₈ to S ₁₀ that connects the other end is connected at one end to the common connection point between the provided capacitor C ₁
The switching elements S ₆ and S ₇ for discharging are inserted between the positive electrode of the capacitor C _{2 and} the negative electrode of the capacitor C ₂ and between the positive electrode of the capacitor C _{2 and} the negative electrode of the capacitor C ₃ , respectively. The on / off timing of the charging switching elements S _{1 to} S ₅ and the discharging switching elements S _{6 to} S ₁₀ is controlled by a control circuit (not shown), and the discharging switching element S ₈
The potential at a connection point connecting to S ₁₀ in common is changed stepwise.

On the other hand, the inverter circuit has switching elements Sa to Sd connected in a bridge, and switching elements Sa, Sb and Sc, Sd in each arm in which switching elements Sa to Sd are connected in series.
Between the connection point is connected a series circuit of the load 3 and the inductor L _1. Further, a capacitor C ₄ is connected to the load 3 in parallel. This type of inverter circuit is well known and provides a period during which the switching elements Sa, Sd or Sb, Sc arranged at diagonal positions of the bridge circuit are simultaneously turned on, and the switching element S of each arm is provided.
a, Sb or Sc, Sd are controlled so as not to be simultaneously turned on, and a period in which the switching elements Sa, Sd are simultaneously turned on and a period in which the switching elements Sb, Sc are simultaneously turned on are alternately generated. The polarity of the voltage applied to the load 3 is alternated. Off of the switching element Sa~Sd it is controlled by the same control circuit and the charging switching element S ₁ to S ₅ and discharging switching element S ₆ to S ₁₀ of the switched capacitor.

Therefore, a voltage that changes stepwise can be generated by the switched capacitor, and the polarity of the voltage applied to the load 3 can be changed by the inverter circuit. The switched capacitor and the inverter circuit are appropriately controlled. This makes it possible to apply a sinusoidal AC voltage that changes stepwise (that is, has a discontinuous waveform) to the load 3.

By the way, the control circuit comprises switching elements S _{1 to} S ₅ for charging and switching elements S _{6 to} S for discharging.
_{10. The} switching elements Sa to Sd are controlled at timings as shown in FIG. Now, the operation will be described assuming that the circuit shown in FIG. 17 performs a steady operation. First,
At time t ₀ and all the charging switching element S ₁ to S ₅ on and the discharging switching element S ₁₀ is turned on. At this time, the voltage across each of the capacitors C _{1 to} C ₃ is charged to a voltage substantially matching the voltage across the DC power supply E, and the voltage V ₁ applied to the inverter circuit is
As shown in (o), the voltage becomes almost equal to the voltage of the DC power supply E.

Next, at time t₁All charging
Switching element S₁~ S_FiveTurn off and discharge switch
Element S₆, S₉Only turn on. by this,
Capacitor C₁, C_TwoAre connected in series, and the voltage V₁Is DC
It becomes almost twice the voltage between both ends of the power supply E. At time t_TwoTo
From this state, the discharging switching element S₉The
Switch element S₇, S₈If you turn on,
All capacitors C ₁~ C_ThreeConnected in series
And the voltage V₁Is approximately three times the voltage across the DC power supply E.
You.

Time t_ThreeAt time t₁In the same state as
Set time t_FourAt time t ₀Set to the same state as
I do. Time t_FiveThen time t_FourState
One. Thereafter, by repeating the above operation, the voltage V
₁Is a pulsating flow in which the voltage rises and falls stepwise as shown in FIG.
It becomes a wave shape. On the other hand, the switches that make up the inverter circuit
The ching elements Sa to Sd are shown in FIGS.
As described above, the charging switching element S₁~ S_FiveYou
And discharge switching element S₆~ S_TenPeriod t₀~ T
_Five, The inductor L₁And capacitor C
_FourThe polarity of the voltage applied to the series circuit is inverted. Toes
The period t₀~ T_FiveTurns off the switching elements Sa and Sd.
To turn off the switching elements Sb and Sc.
The period t_Five~ T_TenTurns off the switching elements Sa and Sd.
The switching elements Sb and Sc are turned on.
You. Thus, the inductor L₁And capacitor C_Four
The voltage applied to the series circuit changes in steps
And the voltage changes as a whole in a sinusoidal AC wave shape.
Will be.

As is apparent from the above description, charging switching elements S ₁ to S ₁ constituting a switched capacitor are provided.
And S ₅ and discharging switching element S ₆ to S _10, is controlled to the switching element Sa~Sd constituting the inverter circuit interlocked with each other. Further, by changing the time interval for switching the on / off combination of the switching elements S _{1 to} S ₁₀ and Sa to Sd, the cycle of the voltage applied to the series circuit of the inductor L ₁ and the capacitor C ₄ can be easily changed. Therefore, a power supply unit having a variable output frequency can be configured by this configuration.

[0009] In this case, the voltage applied to the series circuit of the inductor L ₁ and capacitor C ₄ are those changes stepwise, the inductor L ₁ and capacitor C ₄
Functions as a filter circuit, and can apply a substantially continuous sinusoidal alternating voltage V ₂ as shown in FIG. In this circuit configuration, the energy of one charge / discharge of each of the capacitors C _{1 to} C ₃ can be reduced by increasing the frequency at which the switching elements S _{1 to} S ₁₀ and Sa to Sd are switched. The capacity of C _{1 to} C ₃ can be reduced, and a compact power converter can be provided.

[0010]

In the above configuration, when a load 3 to which a high voltage must be applied is used, the voltage across the DC power supply E is increased or the DC power supply E is connected in series to discharge. It is conceivable to increase the number of capacitors. However, in the former case, the charging switching elements S _{1 to} S ₅ and the discharging switching elements S ₆
It requires that a high breakdown voltage as to S _10, a problem that the upsizing occurs become necessary large element size.
In the latter case, the number of components increases and the size increases, and the number of discharge switching elements connected in series at the time of discharging the capacitor increases. As a result, the power conversion efficiency decreases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to apply a required voltage to a load, as well as to make the voltage applied to the load have a substantially continuous waveform. It is an object of the present invention to provide a power conversion device that does not use a high-withstand-voltage element or reduce power conversion efficiency.

[0012]

According to a first aspect of the present invention, there is provided a power supply section for outputting an alternating current having a discontinuous sinusoidal waveform, a filter element for shaping an output voltage waveform of the power supply section into a substantially continuous waveform, and a power supply. A voltage conversion element for converting the output voltage of the power supply unit into a voltage, and supplying the output voltage of the power supply unit to the load through the filter element and the voltage conversion element. According to this configuration,
Even though the output voltage waveform is discontinuous as the power supply unit, the voltage waveform can be shaped into a substantially continuous waveform using the filter element, and the power supply unit is transformed by using the voltage transformation element to achieve high withstand voltage. It is possible to apply a desired voltage to the load without using the element described above or reducing the power conversion efficiency. As a result, a relatively small power converter can be provided.

According to a second aspect of the present invention, in the first aspect of the present invention, the filter element and the transformer element are composed of a piezoelectric transformer. According to this configuration, since the piezoelectric transformer is used also as the filter element and the voltage transforming element, the number of components is small and the size can be further reduced. According to a third aspect of the present invention, in the second aspect of the present invention, the piezoelectric transformer includes a driving unit in which a pair of input electrodes are opposed to each other across the piezoelectric element, and an output electrode provided on the piezoelectric element at a predetermined distance from the driving unit. In this configuration, the output frequency of the power supply unit is made substantially equal to the resonance frequency of the power generation unit. In this configuration, the piezoelectric transformer can be used with high efficiency and high power conversion efficiency can be obtained. .

According to a fourth aspect of the present invention, in the first to third aspects of the present invention, the discharge lamp is used as a load, and the transformer element outputs a voltage capable of stably lighting and maintaining the discharge lamp. This configuration is a preferred embodiment. The invention according to claim 5 is the invention according to claims 1 to 4,
A power supply unit including a plurality of capacitors, a charging switching element inserted in a charging path from the DC power supply to the capacitor, a discharging switching element inserted in a discharging path from the capacitor to the piezoelectric transformer, and a charging switching element And a control circuit having a pulsating waveform that changes the output voltage waveform stepwise by controlling the on / off timing of the discharge switching element, and pulsating the polarity of the output voltage of the switched capacitor. There is provided a means for inverting the waveform every one cycle. This configuration is a preferred embodiment.

According to a sixth aspect of the present invention, in the first to fifth aspects of the present invention, the output voltage of the power supply section is variable, and is particularly effective when a load having a low applied voltage is used. According to a seventh aspect of the present invention, an output electrode is provided on the piezoelectric element at a predetermined distance from a power supply section for outputting an alternating current having a discontinuous sinusoidal waveform and a driving section having a pair of input electrodes opposed to each other across the piezoelectric element. A piezoelectric transformer for forming an output voltage waveform of the power supply unit into a substantially continuous waveform and converting the output voltage of the power supply unit into a voltage, wherein the power supply unit includes a plurality of capacitors and ,
The switching element for charging inserted in the charging path from the DC power supply to the capacitor, the switching element for discharging inserted in the discharging path from the capacitor to the piezoelectric transformer, and the ON / OFF timing of the switching element for charging and the switching element for discharging. Means for controlling the output voltage waveform so as to gradually change the output voltage waveform into a pulsating waveform, and a means for inverting the polarity of the output voltage of the switched capacitor for each cycle of the pulsating waveform. The output frequency of the power supply unit is set to substantially match the resonance frequency of the power generation unit of the piezoelectric transformer, and the output voltage of the power supply unit is applied to the discharge lamp via the piezoelectric transformer. According to this configuration, it is possible to shape the voltage waveform into a substantially continuous waveform by using the piezoelectric transformer as a filter element, while using a power supply unit that changes the output voltage waveform in a stepwise manner. Since it functions as an element, it becomes possible to apply a desired voltage to a load without using a high-withstand-voltage element in the power supply unit or reducing power conversion efficiency.
As a result, a relatively small power converter can be provided. In addition, since the piezoelectric transformer is used for both the filter element and the voltage transforming element, the number of components is small and the size can be further reduced. Further, since the output frequency of the power supply unit is made substantially equal to the resonance frequency of the power generation unit of the piezoelectric transformer, the piezoelectric transformer can be used with high efficiency, and high power conversion efficiency can be obtained.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) In this embodiment, as shown in FIG. 1, a first power supply section 2a for outputting a stepwise-changing pulsating-wave-shaped voltage, and four switching elements Sa to 3 connected in a bridge. A power supply unit is constituted by the second power supply unit 2b including an inverter circuit having Sd. Each pair of switching elements Sa connected in series constituting each arm of the bridge, Sb and Sc, the inter-connection point of Sd 1 primary winding of the leakage transformer T ₁ of the as a transformer element is connected. Moreover, the load 3 is connected to the secondary winding of the leakage transformer T _1. Capacitor C ₄ is connected in parallel to the leakage primary winding of the transformer T _1, also configured filter element by the leakage component and the capacitor C ₄ of the leakage transformer T _1. This filter element is set to pass only the fundamental wave component of the power supply unit. Therefore, the output voltage waveform of the second power supply section 2b is made discontinuous at the stepped, substantially continuous voltage waveform obtained in the secondary winding of the leakage transformer T _1. Further, since using the leakage transformer T _1, it can be set transformation ratio appropriately, the boost or buck the required voltage can be applied to the load 3.

When the voltage is increased by the leakage transformer T ₁ , the _first voltage is applied to the load 3 when the high voltage is applied to the load 3.
A small power change circuit can be provided without requiring a high withstand voltage element for the power supply unit 2a or the second power supply unit 2b and without increasing the number of components. Moreover, since the voltage waveform applied to the load 3 is substantially continuous in a sine wave shape, power can be stably supplied to the load 3 and the noise is reduced.

(Embodiment 2) In this embodiment, as shown in FIG. 2, the switched capacitor shown in FIG. 17 is used as the first power supply section 2a. Is output from the second power supply unit 2b. In this configuration, the leakage transformer T
_In the secondary winding of No. ₂ , an AC voltage having a sine wave shape is obtained. Other configurations and operations are the same as those of the first embodiment.

(Embodiment 3) This embodiment corresponds to Embodiment 2
Capacitor C at_FourWas changed.
Then, as shown in FIG.₁Primary
Capacitor C for winding_FourAre connected in series. Other configurations
The operation is the same as in the second embodiment. (Embodiment 4) As shown in FIG.
Leakage transformer T in form 2 ₁Instead of piezoelectric
Lance T_TwoThe load 3 is a capacitor
C_FiveAre connected in parallel. Therefore, the first power supply unit 2a
The configuration of the second power supply unit 2b is the same as that of the second embodiment.
It is.

The piezoelectric transformer T ₂ has a pair of input electrodes 12 a, 12 a at one longitudinal end of a rectangular parallelepiped piezoelectric element 11.
b facing each other and the output electrode 13 on the other end surface in the longitudinal direction.
Is provided. Both input electrodes 12a, 12b
During this period, the power generation unit 16 functions as the drive unit 15, and the power generation unit 16 is formed between the drive unit 15 and the output electrode 13. The piezoelectric transformer T ₂ generates a mechanical vibration in the piezoelectric element 11 by applying an AC voltage to the drive unit 15, and extracts a voltage generated by the mechanical vibration from the output electrode 13. Since mechanical vibration has inertia, it equivalently functions as a filter circuit. Further, the piezoelectric transformer T ₂ has a resonance frequency corresponding to the length dimension of the power generation unit 16, and a voltage having a frequency close to the resonance frequency is applied to the input electrodes 12 a and 12 b to resonate the piezoelectric element 11. Thus, a greatly boosted voltage can be obtained from the output electrode 13.

As described above, since the piezoelectric transformer T ₂ has both a function as a filter element and a function as a boosting element, it is not necessary to separately provide an element for constituting the filter element. Moreover, the piezoelectric transformer T ₂ compared to the transformer having a winding on the iron core leads to since it is possible downsizing as a whole compact or low profile of (thin).

Each switching element S in the present embodiment
₁ to S _10, FIG. 5 by a control circuit Sa~Sd is not shown
The timing is controlled as follows. This timing is the same as the timing in the conventional configuration shown in FIG. That is, the output voltage V ₁ of the first power supply section 2a as shown in FIG. 5 (o) is the same as the conventional example, also similar to the output voltage of the second power supply section 2b also conventional as in Fig. 5 (p) Sine wave AC wave shape which is a step-like shape. Here, the piezoelectric transformer T
By applying a voltage to the load 3 via the _2, 5
As shown in (q), a sine wave AC wave shape and a boosted voltage can be applied to the load 3. Other configurations and operations are the same as those of the conventional example.

[0023] (Embodiment 5) In this embodiment, as shown in FIG. 6, in the embodiment 4 is obtained by omitting the capacitor C ₅ connected in parallel with the load 3. In this configuration, the second
The output frequency of the power supply unit 2b, by substantially coincides with the resonance frequency of the power generation portion 16 of the piezoelectric transformer T _2, without the capacitor C ₅ and applying an AC voltage of a continuous wave to the load 3, the power with low noise It can be supplied. Other configurations and operations are the same as those of the fourth embodiment.

(Embodiment 6) In the present embodiment, as shown in FIG.
This is a discharge lamp 31 provided with: In this configuration,
Although a high voltage is required at the time of starting the discharge lamp 31, the output voltages of the first power supply unit 2a and the second power supply unit 2b may be low, so that the elements constituting the first power supply unit 2a and the second power supply unit 2b It is not necessary to use a high withstand voltage device, and a high voltage can be obtained while using a low withstand voltage element. Other configurations and operations are the same as those of the fourth embodiment.

(Embodiment 7) In this embodiment, as shown in FIG. 8, the load 3 in the configuration of Embodiment 4 is a discharge lamp 31 provided with a hot cathode (filament) 33. A capacitor C ₆ is connected between one ends of both filaments 33. Therefore, the filament 3 by passing a current through the capacitor C ₅ at the time of preheating
3 can be heated, and thereafter, by applying a high voltage boosted by the piezoelectric transformer T ₂ to the discharge lamp 31,
The discharge lamp 31 can be started. Other configurations and operations are the same as those of the fourth embodiment.

[0026] (Embodiment 8) In this embodiment, as shown in FIG. 9, in the configuration of the fourth embodiment shown in FIG. 6, a capacitor C ₄ connected in parallel with the primary side of the piezoelectric transformer T _2,
A series circuit of a capacitor C ₄ and the inductor L ₁ which are connected between the output terminal of the second power supply section 2b. Since general piezoelectric transformer T ₂ are has a capacitive component, there is a possibility that an inrush current flows through the output voltage upon application of the second power supply section 2b, in the circuit configuration of the present embodiment, the piezoelectric transformer T ₂ and choke input type circuit is constituted by the inductor L ₁ in series connection to a parallel circuit of a capacitor C _4, it is possible to reduce the rush current. Therefore, generation of stress and noise due to the rush current can be suppressed. Other configurations and operations are the same as those of the fourth embodiment.

(Embodiment 9) This embodiment is shown in FIG.
As described above, in the configuration of the fifth embodiment shown in FIG.
An inductor L is provided between the first power supply unit 2a and the second power supply unit 2b._Two
And capacitor C ₇With a filter circuit consisting of
It is. This filter circuit is a choke input type
A low-pass filter that is output from the first power supply unit 2a.
Function to make the step-like discontinuous voltage waveform slightly smoother
And a piezoelectric transformer T_TwoTo reduce the inrush current
It has a function to Therefore, similar to the eighth embodiment,
It can suppress the generation of stress and noise due to current.
Wear. Other configurations and operations are the same as those of the fourth embodiment.

(Embodiment 10) In this embodiment, as shown in FIG. 11, a power supply section capable of obtaining an output voltage in a stepped and sinusoidal AC wave form is realized by using only a switched capacitor without using an inverter circuit. Is what you do. That is, the positive power supply unit 2 including a switched capacitor having the same configuration as the switched capacitor shown in the conventional example.
c and a negative power supply 2d. However, the positive power supply unit 2c and the negative power supply unit 2d have the connection polarities to the DC power supply E reversed. Therefore, as described as a conventional example, a step-like and pulsating wave output voltage is obtained at the positive potential from the positive power supply unit 2c, and a step-like and pulsating wave whose polarity is reversed is obtained from the negative power supply unit 2d. A shape output voltage is obtained. In other words, by alternately operating the positive power supply unit 2c and the negative power supply unit 2d, a step-like output having a sine wave AC wave shape can be obtained.

This will be described more specifically. Positive power supply portion 2c is a switched capacitor of the same configuration described in the conventional example, the capacitor C ₁ -C _3, charge switching element S
₁ to S _5, constituted by a discharge switching element S ₆ to S _10. On the other hand, the negative power supply unit 2d, the capacitors C ₁₁ -C
_13, charge switching element S ₁₁ to S _15, constituted by a discharge switching element S ₁₆ to S _20. Positive power supply 2c
And the negative power supply unit 2d have the same configuration,
In c the capacitor C ₁ whereas being connected to the negative electrode of the DC power source E, a point that connects the negative power supply unit 2d capacitor C ₁₁ to the positive electrode of the DC power source E is different. Further, to the output terminal with one end connected to a common discharge switching element S ₈ to S _10, one end of the discharge switching element S ₁₈ to S ₂₀ are connected in common. Piezoelectric transformer T ₂ is inserted between the power supply unit and the load 3, discharge switching element S ₈ to S
_10, one end of the S ₁₈ to S ₂₀ are connected in common to one input terminal 12a of the piezoelectric transformer T _2, and the other input terminal 12b is connected to the negative electrode of the DC power source E.

The switching elements S _{1 to} S ₂₀
Are controlled by a control circuit (not shown) as shown in FIGS. That is, in the periods t _{0 to} t ₁ , the charging switching elements S _{1 to} S ₅ and the discharging switching element S ₁₀ are turned on, and a voltage substantially equal to the voltage across the DC power supply E as shown in FIG. Is output. Next, at time t _1, to turn off the charge switching element S ₁ to S ₅ and discharging switching element S _10, to turn on the discharge switching element S _6, S _9.
This connects the capacitors C ₁ and C ₂ in series,
The voltage V ₁ is almost twice the voltage across the DC power supply E. In yet time t _2, the turn off the discharge switching element S ₉ from this state, when turning on the switching element S _7, S _8, it will be connected to all of the capacitors C ₁ -C ₃ in series, the voltage V ₁ is approximately three times the voltage across the DC power supply E.

Time t_ThreeAt time t₁In the same state as
Set time t_FourAt time t ₀Set to the same state as
I do. Time t_FiveThen time t_FourState
One. During the series of operations described above, the switching element S₁₁
~ S₂₀Are all kept off. This kind of operation
And the piezoelectric transformer T_TwoApplied to input terminals 12a and 12b
Voltage V₁Is positive and stepped as shown in FIG.
Up and down.

Time t_Five, The above operation is
2d, the period t_Five~ T₆Then
Switching element S for charging₁₁~ S_FifteenAnd discharge switch
Ching element S₂₀Is turned on, and as shown in FIG.
A negative voltage substantially equal to the voltage across the power supply E is output.
Next, at time t₆, The charging switching element S ₁₁
~ S_FifteenAnd discharge switching element S₂₀Turn off,
Switching element S for discharge₁₆, S₁₉Turn on. this
As a result, the capacitor C₁₁, C₁₂Are connected in series and the voltage
V₁Becomes almost twice the voltage between both ends of the DC power supply E. further
Time t₇In this state, the switching element for discharging
Child S₁₉Is turned off, and the switching element S ₁₇, S₁₈On
Then all capacitors C₁~ C_ThreeConnected in series
The voltage V₁Is the voltage between both ends of the DC power supply E.
It is about three times as large.

Time t₈At time t₆In the same state as
Set time t₉At time t ₀Set to the same state as
I do. Time t_TenThen time t₉State
One. During the series of operations described above, the switching element S₁
~ S_TenAre all kept off. This kind of operation
And the piezoelectric transformer T_TwoApplied to input terminals 12a and 12b
Voltage V₁Is the period t_Five~ T_TenIn FIG.
As shown in (u), it goes up and down stepwise with negative polarity.

By repeating the above operation, it is possible to obtain an output voltage that changes stepwise and in the form of a sine wave AC wave.
It becomes possible to apply a sinusoidal high voltage as shown in FIG. Even with this configuration, a low-noise power changing device can be provided. (Embodiment 11) As shown in FIG.
The output voltage of the DC power supply E is variable in the configuration of the fourth embodiment. According to this configuration, by adjusting the voltage across the DC power source E, it is possible to change the voltage applied to the load 3 and the piezoelectric transformer T _2. This is particularly effective when the voltage applied to the load 3 is to be reduced.

Load 3 and piezoelectric transformer T_TwoVoltage applied to
To reduce it, the output voltage of DC power supply E is changed.
No, switching element S₁~ S_TenTo control the first
The peak value of the output voltage of the power supply unit 2a is determined by calculating
It is also possible to suppress it to twice as large as Other configurations and
The operation is the same as that of the fourth embodiment. (Embodiment 12) In this embodiment, as shown in FIG.
Switch between DC power supply E and switched capacitor
Insert a series circuit of the impedance element Sx and the impedance element Z
And a direct connection between the switching element Sx and the DC power supply E.
Diode D in column circuit₁Are connected in parallel.
In this configuration, the charging switching element S₁~ S_ThreeNo
Turns on the switching element Sx during the period when the shift is on
And the capacitor C via the impedance element Z₁~
C_ThreeTo charge the capacitor C₁~ C _Threeof
The voltage between both ends is reduced. Therefore, Sui
By appropriately controlling the switching element Sx, the first
The output voltage of the power supply unit 2a can be adjusted. What
Contact, diode D₁Is for regeneration. Impeder
As the impedance element Z, as shown in FIGS.
Resistance R₀, Inductor L₀, Inductor L₀And conde
Sensor C₀It can use various things such as a series circuit with
Wear. Other configurations and operations are the same as those of the fourth embodiment.

(Embodiment 13) As shown in FIG. 16, the present embodiment differs from the configuration of Embodiment 4 in that
a and is inserted impedance element Z ₂ between the second power supply section 2b, and a capacitor C ₇ between the input terminal of the second power supply section 2b, more regenerative between output terminals of the first power supply section 2a it is obtained by connecting the diode D ₂ of use.

According to this configuration, the capacitor C₁~ C_Three
Impedance element Z in the discharge path of _TwoIs inserted
From the switching element S₈~ S_TenThe on-period of the
If it is adjusted, the input voltage to the second power supply section 2b can be adjusted.
And become possible. Where the impedance element Z_TwoTo
The same one as in Embodiment 12 can be used. other
The configuration and operation are the same as in the fourth embodiment.

[0038]

According to the first aspect of the present invention, there is provided a power supply section for outputting an alternating current having a discontinuous sinusoidal waveform, a filter element for shaping an output voltage waveform of the power supply section into a substantially continuous waveform, and an output voltage of the power supply section. And a transformer element for converting the voltage of the power supply unit, the output voltage of the power supply unit is supplied to the load through the filter element and the transformer element, and the filter element is used as the power supply unit while the output voltage waveform is discontinuous. The voltage waveform can be shaped into a substantially continuous waveform by using a voltage-transforming element, and the desired voltage can be obtained without using a high-voltage element in the power supply unit or reducing the power conversion efficiency. Can be applied to the load. As a result, there is an advantage that a relatively small power converter can be provided.

According to the second aspect of the present invention, when the filter element and the transforming element are composed of a piezoelectric transformer, the piezoelectric transformer is used for both the filter element and the transforming element.
There is an advantage that the number of parts is small and the size can be further reduced. As in the invention according to claim 3, the piezoelectric transformer includes a driving unit in which a pair of input electrodes are opposed to each other with the piezoelectric element interposed therebetween, and a power generation unit in which the piezoelectric element is provided with an output electrode at a predetermined distance from the driving unit. In the case where the output frequency of the power supply unit is made substantially equal to the natural frequency of the power generation unit, there is an advantage that the piezoelectric transformer can be used with high efficiency and high power conversion efficiency can be obtained.

According to the sixth aspect of the present invention, when the output voltage of the power supply unit is variable, when the load with a low applied voltage is used, it is only necessary to lower the output voltage of the power supply unit. There is an advantage that it is possible to cope with load. According to a seventh aspect of the present invention, an output electrode is provided on the piezoelectric element at a predetermined distance from a power supply section for outputting an alternating current having a discontinuous sinusoidal waveform and a driving section having a pair of input electrodes opposed to each other across the piezoelectric element. A piezoelectric transformer for forming an output voltage waveform of the power supply unit into a substantially continuous waveform and converting the output voltage of the power supply unit into a voltage, wherein the power supply unit includes a plurality of capacitors and A charging switching element inserted in a charging path from a DC power supply to a capacitor, a discharging switching element inserted in a discharging path from a capacitor to a piezoelectric transformer, and ON / OFF timing of the charging switching element and the discharging switching element. And a control circuit for forming a pulsating waveform in which the output voltage waveform changes stepwise by controlling the output voltage waveform. Together, comprising means for inverting the polarity of the output voltage of the switched capacitor in each cycle of the pulsating voltage, the output frequency of the power supply unit is set so as to substantially coincide with the natural frequency of the power generating portion of the piezoelectric transformer,
The output voltage of the power supply section is applied to the discharge lamp via the piezoelectric transformer.Although the output voltage waveform changes stepwise as the power supply section, the voltage waveform is almost continuous using the piezoelectric transformer as a filter element. Because the piezoelectric transformer can function as a transformer element, a desired voltage can be applied to the load without using a high-voltage element in the power supply unit or reducing the power conversion efficiency. It has the advantage that it becomes possible. As a result, there is an effect that a relatively small power converter can be provided. In addition, since the piezoelectric transformer is used for both the filter element and the transformer element, the number of parts is small and the size can be further reduced. Since the frequency substantially matches the frequency, there is an advantage that the piezoelectric transformer can be used with high efficiency and high power conversion efficiency can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram showing a second embodiment.

FIG. 3 is a main part circuit diagram showing a third embodiment.

FIG. 4 is a circuit diagram showing a fourth embodiment.

FIG. 5 is an operation explanatory view of the above.

FIG. 6 is a main part circuit diagram showing a fifth embodiment.

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

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

FIG. 9 is a circuit diagram showing an eighth embodiment.

FIG. 10 is a circuit diagram showing a ninth embodiment.

FIG. 11 is a circuit diagram showing a tenth embodiment.

FIG. 12 is an operation explanatory view of the above.

FIG. 13 is a main part circuit diagram showing an eleventh embodiment.

FIG. 14 is a main part circuit diagram showing a twelfth embodiment.

FIG. 15 is a diagram showing an example of an impedance element used in the Embodiment.

FIG. 16 is a main part circuit diagram showing a thirteenth embodiment;

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

FIG. 18 is an operation explanatory view of the above.

[Explanation of symbols]

2a first power supply portion 2b second power supply unit 3 load 11 piezoelectric elements 12a, 12b input electrodes 13a, 13b output electrode 15 driver 16 the power generation unit 31 discharge lamp 33 filaments _{C 1 ~C 3, C 11 ~C} 13 capacitor C ₄ capacitor L ₁ inductor _{S 1 ~S 5, S 11 ~S} 15 charge switching element _{S 6 ~S 10, S 16 ~S} 20 discharge switching element T ₁ the leakage transformer T ₂ piezoelectric transformer

Claims (7)

[Claims] 1. A power supply section for outputting an alternating current having a discontinuous sinusoidal waveform, a filter element for shaping an output voltage waveform of the power supply section into a substantially continuous waveform, and a transformer element for converting the output voltage of the power supply section into a voltage. And a power converter for supplying an output voltage of a power supply unit to a load through a filter element and a transformer element. 2. The power converter according to claim 1, wherein the filter element and the transforming element are composed of piezoelectric transformers. 3. A piezoelectric transformer comprises: a driving section in which a pair of input electrodes are arranged opposite to each other with a piezoelectric element interposed therebetween; and a power generating section in which an output electrode is provided on the piezoelectric element at a predetermined distance from the driving section. 3. The power converter according to claim 2, wherein an output frequency of the power converter is substantially equal to a resonance frequency of the power generation unit. 4. The power conversion device according to claim 1, wherein the discharge lamp is used as a load, and the transformer element outputs a voltage capable of stably lighting and maintaining the discharge lamp. 5. A power supply unit comprising: a plurality of capacitors; a charging switching element inserted in a charging path from the DC power supply to the capacitor; and a discharging switching element inserted in a discharging path from the capacitor to the piezoelectric transformer. A control circuit having a pulsating waveform that changes the output voltage waveform stepwise by controlling the on / off timing of the charging switching element and the discharging switching element. 5. The power converter according to claim 1, further comprising a unit for inverting the polarity every period of the pulsating waveform. 6. The power converter according to claim 1, wherein an output voltage of the power supply unit is variable. 7. A power generation unit, wherein a power supply unit for outputting an alternating current having a discontinuous sinusoidal waveform and a driving unit in which a pair of input electrodes are opposed to each other across a piezoelectric element by a predetermined distance are provided with an output electrode on the piezoelectric element to generate power. A piezoelectric transformer for forming the output voltage waveform of the power supply unit into a substantially continuous waveform and converting the output voltage of the power supply unit into a voltage,
The power supply unit includes a plurality of capacitors, a charging switching element inserted in a charging path from the DC power supply to the capacitor, a discharging switching element inserted in a discharging path from the capacitor to the piezoelectric transformer, and a charging switching element. And a control circuit having a pulsating waveform that changes the output voltage waveform stepwise by controlling the on / off timing of the discharge switching element, and pulsating the polarity of the output voltage of the switched capacitor. A means for inverting the waveform for each cycle is provided, the output frequency of the power supply is set to substantially match the resonance frequency of the power generation unit of the piezoelectric transformer, and the output voltage of the power supply is applied to the discharge lamp via the piezoelectric transformer. A power conversion device characterized in that: