JPH11341825A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of switching elements without increasing a withstand voltage and to downsize a power conversion device, by reducing the chip area of the switching elements. SOLUTION: The source terminals of switching elements S11, S31, S51 are connected with those of switching elements S21, S41, S61 respectively, and the drain terminals of the switching elements S21, S41 are connected with those of the switching elements S31, S51 respectively. Similarly, the drain terminals of switching elements S12, S32, S52 are connected with those of switching elements S22, S42, S62 respectively, and the source terminals of switching elements S22, S42 are connected with those of switching elements S32, S52, respectively. Capacitors Cm are connected between the connection points of switching element Sm1 and Sm+1, 1 and those of switching elements Sm2 and Sm+1, 2. Two of the four switching elements for one capacitor are shared by two neighboring capacitors. Therefore, it is possible to reduce the number of the switching elements without increasing the withstand voltage, and to downsize a power converting device by reducing the chip area of the switching elements.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter for converting a DC voltage into an AC voltage using a switched capacitor circuit.

[0002]

2. Description of the Related Art Conventionally, there is a circuit as shown in FIG. 11 as a power conversion circuit for obtaining a smooth AC output from a DC power supply using a minute inductor and a switched capacitor (see Japanese Patent Application Laid-Open No. 9-47032). .

This conventional example (hereinafter, referred to as "conventional example 1")
Connects a plurality of capacitors (C1 to C5) to a DC power supply DC.
(Voltage E) and collectively and parallel charging, and discharging an arbitrary number of capacitors in series to an arbitrary polarity, so that a load of -5
E, -4E, -3E, -2E, -E, 0, E, 2E, 3
A switched capacitor circuit SC capable of supplying voltages Vsc of E, 4E and 5E, a filter circuit including a small inductor Lz and a small capacitor Cz is connected to the output thereof, and a load Z is connected in parallel with the small capacitor Cz. And these control circuits (not shown).

The configuration of the switched capacitor circuit SC is composed of five switched capacitor cells SCm (m = 1,
2, 3, 4, 5) and its charging circuit. Each of the switched capacitor cells SCm includes switch elements Sm1, Sm2 and Sm3, Sm which operate complementarily.
4 and a capacitor Cm connected between a connection point between the switch elements Sm3 and Sm1 and a connection point between Sm4 and Sm2, and each cell includes a connection point between the switch elements Sm1 and Sm2. Switch elements Sn3 and S
The connection is made in series by connecting n4 connection points (m ≠ n). Further, when these switch elements are realized by MOSFETs having body diodes, the switch elements Sm1, Sm2 and Sm3, Sm4 are connected in series such that the plus side of the capacitor Cm is the drain and the minus side is the source.

The output of the switched capacitor circuit SC is
Switched capacitor cells SC1, SC2,..., SC5
From the cells at both ends of the series circuit, specifically, the connection point between the switch elements S11 and S12 and the switch element S5
A load circuit is connected between nodes 3 and S54.

Further, each switched capacitor cell SCm
In the parallel charging circuit, the cathodes of the diodes D1 to D5 are connected to the positive sides of the capacitors C1 to C5, the anodes are connected to each other and connected to a series circuit of the DC power supply DC and the switch element S6. S13, S2
1,..., S43, S51, and S31, which are the midpoints of the series circuit (switch row A) of S53 and S31
To the connection point. Switch elements S12, S14, S
, S52 and S54 (switch row B) are turned off, all switch rows A are turned on, and switch element S6 is turned on.
Is turned on, all the capacitors C1 to C5 are charged in parallel with the same voltage E, with the side connected to the switch array B being positive.

Next, an example of a control method for supplying an AC voltage to the load Z will be described with reference to FIG. In the initial state, it is assumed that all the capacitors C1 to C5 are equally charged with the same voltage E, all the switch rows A are on, and all the switch rows B are off. When the switch element S13 is turned off and the switch element S14 is turned on at time t0, the switch element S11, the capacitor C1, and the switch element S1 are turned on.
4, switch elements S21, S23, S31, S33, S
41, S43, S51, and S53 through the capacitor C1.
Is connected to the load Z in the plus direction, and the output Vsc of the switched capacitor circuit SC becomes + E. When switch element S23 is turned off and switch element S24 is turned on at time t1, switch element S11, capacitor C1, switch elements S14 and S21, capacitor C2, switch element S
24, S31, S33, S41, S43, S51, S5
In the path 3, the capacitors C1 and C2 are connected in series in the plus direction to the load Z, and the output Vsc of the switched capacitor circuit SC becomes + 2E. From time t2 to time t4, by the same control, the capacitors C3, C4, and C5 are also connected in series in the positive direction sequentially, so that the output Vsc of the switched capacitor circuit SC sequentially increases in steps of + 3E, + 4E, and + 5E.

Next, when the switch element S14 is turned off and the switch element S13 is turned on at time t5, the capacitor C5
Is disconnected from the load current path, and the output Vsc of the switched capacitor circuit SC drops to + 4E. Similarly, by sequentially disconnecting the capacitors C4, C3, C2, and C1 from the load current path, the output Vsc of the switched capacitor circuit SC decreases stepwise to + 3E, + 2E, + E, and 0. At time t9, when all the capacitors C1 to C5 are disconnected from the load current path and all the switch rows A are turned on and all the switch rows B are turned off, the switch element S6 is turned on and the capacitors C1 to C5 are connected in parallel to the DC power supply DC. Charge from. At time t10 when charging is completed, switch element S6 is turned off, switch element S11 is turned off, and switch element S1 is turned off.
2, the switching element S12 and the capacitor C
1, switch elements S13, S21, S23, S31, S
The capacitor C1 is connected to the load Z in the negative direction through the paths 33, S41, S43, S51, and S53, and the output Vsc of the switched capacitor circuit SC becomes -E. With the same control, the capacitors C2, C3, C4, and C5 are also connected in series in the negative direction, so that the output Vsc of the switched capacitor circuit SC is sequentially changed to -2E, -3.
E, -4E, and -5E change stepwise. When the output Vsc of the switched capacitor circuit SC becomes -5E,
At time t16, the capacitor C5 is disconnected from the current path,
The output Vsc of the switched capacitor circuit SC becomes -4E. Similarly, the output Vsc of the switched capacitor circuit SC returns to zero at time t19 by disconnecting the capacitors C4, C3, C2, and C1 from the current path. that's all,
When the operation at times t0 to t19 is performed, the switched capacitor circuit SC applies an alternating current having an amplitude of −5E to 5E to the load Z in a stepwise manner. If a one-step staircase waveform output from the switched capacitor circuit SC is filtered into a smooth waveform by the small inductor Lz and the small capacitor Cz in the load section, a smooth AC voltage Vz as shown in FIG. Can be supplied.

In the conventional example 1, a single low-voltage capacitor is connected or disconnected in series to generate a plurality of voltages, and a small LC filter supplies a smooth AC voltage to the load. And a small chip area can be used. However, the number of switch elements increases, and most of the switch elements are high-side switches in which the reference potential fluctuates. Therefore, many level shift circuits for adjusting the drive pulse to the reference potential of each switch element are required. .

Another prior art example (hereinafter, referred to as "conventional example 2") in which the number of switch elements is reduced in view of the disadvantage of the prior art example 1 is a circuit configuration as shown in FIG. No. 10-42576). Conventional example 2
In the conventional example 1, the switched capacitor circuits having different outputs are combined and connected in series, so that the switched capacitor circuit can output a voltage equal to or more than the number of the switched capacitor cells.

Switched capacitor circuit SC of conventional example 2
13 includes three switched capacitor cells SC1 to SC3, for example, as shown in FIG.
3, a diode D31 and a capacitor C4 are connected in series, a diode D32 is connected in parallel with the diode D31 and the capacitor C4, and a diode D33 is connected in parallel with the diode D31 and the capacitor C3. In the configuration of the switched capacitor cell SC3, the series circuit of the capacitors C3 and C4 is connected to the DC power supply D
C to a voltage of 2E, and discharge capacitors C3 and C4
The voltage E is applied to the load circuit in the parallel circuit. That is, in the configuration of the conventional example 2, the capacitors Cl and C2 are connected to the voltage 2
E, charge the capacitors C3 and C4 to different voltages of the voltage E, and charge them to E, 2E, E + 2E, 2E + 2E,
By combining with E + 2E + 2E, it is possible to output five levels of positive and negative voltages even if the number of switch elements is reduced as compared with Conventional Example 1. For example, by performing control as shown in FIG. 14 on the switch element, an output voltage similar to that of the first conventional example can be obtained.

As described above, in the conventional example 2, a switched capacitor circuit including three switched capacitor cells has the same output as the switched capacitor circuit including the five switched capacitor cells SC1 to SC5 shown in the conventional example 1. And the number of switch elements constituting the switched capacitor circuit can be reduced to 分 の, and the number of level shift circuits can be reduced.

[0013]

As described above, in the first conventional example, although switch elements having a low withstand voltage can be used, the number of switch elements increases, and a number of level shift circuits are required in accordance with the number of switch elements. .

Further, in the conventional example 2, while the number of switch elements is small and the number of level shift circuits corresponding thereto is reduced, the same output as in the conventional example 1 can be obtained. You will need it.
For example, in the circuit configuration shown in FIG. 13, the switch elements S11.
Require a withstand voltage twice as high as that of the conventional example 1, and also require a switch element with a withstand voltage that is more than twice as high in other configurations. Since the chip area of the switch element tends to increase as the withstand voltage increases, there is a problem that there is a limit in reducing the chip area of the entire switch element even if the number of switch elements is reduced.

The present invention has been made in view of the above problems, and an object of the present invention is to reduce the number of switch elements and increase the chip area of the switch elements without increasing the withstand voltage. An object of the present invention is to provide a power conversion device that can be reduced in size and made smaller.

Another object of the present invention is to provide a power conversion device capable of reducing switching noise by blocking a through current.

It is another object of the present invention to provide a power conversion device which can reduce a loss and a noise due to switching and can downsize a circuit, and can use a small element as a countermeasure component. To provide.

Still another object of the present invention is to provide a power converter capable of reducing noise of a voltage applied to a load.

[0019]

According to a first aspect of the present invention, in order to achieve the above object, a plurality of capacitors serving as voltage sources are provided, and a low potential side and a high potential side of adjacent capacitors are respectively set. A series connection of two switch elements is connected in parallel to the capacitors at both ends, and a diode is connected in parallel from the low potential side to the high potential side of the capacitors in parallel with all switch elements. A switched capacitor circuit, means for charging each capacitor from a voltage source, a load circuit connected between the connection points of two switch elements connected to both ends of the switched capacitor circuit, and Control means for controlling the on / off of the switch element to supply an AC output to the load circuit so that the switch element is connected in series with an arbitrary polarity. In contrast to the conventional example in which four switch elements are connected to one capacitor in a bridge shape, the number of switch elements can be increased without increasing withstand voltage by sharing two switch elements with adjacent capacitors. , And the chip area of the switch element is reduced, so that downsizing can be achieved.

According to a second aspect of the present invention, in the first aspect of the present invention, a through current blocking means for blocking a through current caused by a parasitic capacitance of the switch element is connected in series with the capacitor. , The switching noise can be reduced.

According to a third aspect of the present invention, in the second aspect, the through current blocking means comprises a parallel circuit of an inductor and a diode, and the through current can be blocked with a simple configuration.

According to a fourth aspect of the present invention, in the first aspect of the present invention, a high-frequency current source is provided in a series circuit of two switch elements connected in parallel to the switch elements of the switched capacitor circuit, the directions of the diodes being alternated. Connected in parallel, the current when each switch element switches from the off state to the on state flows in the forward direction with the diode, and the current when the switch element switches from the on state to the off state flows in the reverse direction with the diode. In addition, the current flowing through the load circuit and the current from the high-frequency current source are superimposed, so that loss and noise due to switching can be reduced, and the circuit can be downsized. In addition, a small device can be used.

According to a fifth aspect of the present invention, in the fourth aspect, the high-frequency current source comprises a series resonant circuit of an inductor and a capacitor, and the high-frequency current source is operated by the operation of each switch element using the capacitor as the voltage source as a power supply. And the circuit configuration of the high-frequency current source can be simplified.

According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the resonance frequency of the resonance circuit is at least three times the frequency of the output voltage of the switched capacitor circuit. Loss and noise can be reduced.

According to a seventh aspect of the present invention, in the first aspect, a filtering circuit for filtering a discontinuous output voltage of the switched capacitor circuit is connected between the switched capacitor circuit and the load. As a feature, noise of the load applied voltage can be reduced.

According to an eighth aspect of the present invention, in the seventh aspect of the present invention, a substantially sinusoidal current is supplied to the load by the switched capacitor circuit and the filtering circuit, thereby reducing noise in the voltage applied to the load. be able to.

[0027]

(Embodiment 1) Embodiment 1 of the present invention is different from Conventional Example 1 in that the switched capacitor cells are arranged so that the polarities of the capacitors of the switched capacitor cells are alternately arranged. 4 connected to the connection point of
The number of switching elements is reduced as a whole by sharing the two switching elements with two switched capacitor cells.

Hereinafter, the present embodiment will be described in detail with reference to the circuit diagram of FIG. 1 and the operation explanatory diagrams of FIGS.

As shown in FIG. 1, the switched capacitor circuit SC has two switch rows A and B. One switch row A connects the source terminals of the switch elements S11 and S21, the switch elements S31 and S41, and the switch elements S51 and S61.
And S31, and the drain terminals of the switch elements S41 and S51 are connected to each other. The switch row B includes switch elements S12 and S22, and switch elements S32 and S4.
2. The drain terminals of the switch elements S52 and S62 are connected to each other, and the source terminals of the switch elements S22 and S32 and the switch elements S42 and S52 are connected to each other. And, five capacitors C for power conversion
m (m = 1, 2, 3, 4, 5) are switching elements Sm1 and Sm + 1, 1 (= S21, S31, S41,
S51, S61), and the switching elements Sm2 and Sm2.
m + 1, 2 (= S22, S32, S42, S52, S6
The capacitor Cm adjacent to the connection point 2) is connected so that the polarities of the adjacent capacitors Cm are opposite to each other.

The drain terminal of the switch element S11 and the source terminal of the switch element S12, and the drain terminal of the switch element S61 and the source terminal of the switch element S62 are connected, and a load circuit is connected between the connection points of the switch elements. I have. This load circuit includes a load Z such as a discharge lamp, a small inductor Lz and a small capacitor Cz.
And a filtering circuit composed of a series circuit. That is, as described later, the one-step staircase waveform output from the switched capacitor circuit SC is filtered by the above-described filtering circuit into a smooth waveform, so that a smooth AC voltage Vz as shown in FIG. It can be supplied.

By the way, as a means for charging each capacitor Cm, a switch element S is connected between a connection point between the switch elements S31 and S41 and a connection point between the switch elements S52 and S62.
The DC power supply DC is connected via a switching element S71 to the connection point between the DC power supply DC and the switch element S71.
The switch element S72 is connected between the connection point of S12 and S22. Here, assuming that the charging voltage of each capacitor Cm is E, the power supply voltage of the DC power supply DC is 3E, and each of the capacitors C1 to C5 is charged by turning on and off each switch element by a control unit (not shown).

Next, an example of a control method for supplying an AC voltage to the load Z will be described with reference to FIGS. In the initial state, it is assumed that all the capacitors C1 to C5 are equally charged with the same voltage E, all the switch rows A are off, and all the switch rows B are on. In this state, the output Vsc of the switched capacitor circuit SC is zero (see FIG. 3A). When the switching element S12 is turned off and the switching element S11 is turned on at time t1, the switching element S
11, the capacitor C1, the switch elements S22, S32,
The capacitor C1 is connected to the load Z in the positive direction through the paths of S42, S52, and S62, and the output Vsc of the switched capacitor circuit SC becomes + E (see FIG. 3B).
At time t2, the switch elements S32, S42, S52, S6
2 off, switch elements S31, S41, S51, S6
1 when the switch element S11 and the capacitor C
1, the capacitors C1 and C2 are connected in series in the plus direction to the load Z through the path of the switch element S22, the capacitor C2, and the switch elements S31, S41, S51, and S61.
The output Vsc of the switched capacitor circuit SC becomes + 2E (see FIG. 3C). By the same control from time t3 to time t5, the capacitors V3, C4, and C5 are sequentially connected in series in the positive direction, so that the output Vsc of the switched capacitor circuit SC sequentially increases by + 3E, + 4E, and +5.
As shown in FIG. 3 (d) and FIG.
(See (a) and (b)).

Next, when the switch element S11 is turned off and the switch element S12 is turned on at time t6, the capacitor C1 is turned on.
Is disconnected from the load current path, and the output Vsc of the switched capacitor circuit SC drops to + 4E (FIG. 4C).
reference). Similarly, capacitors C2, C3, C4, C5
And the load current path, the output Vsc of the switched capacitor circuit SC is increased stepwise by + 3E, + 2E.
E and + E (FIGS. 4D and 5A and 5B)
reference). By turning on the switch row A and turning off the switch row B at time t10, all the capacitors C1 to C5
Is disconnected from the load current path, and the output Vsc of the switched capacitor circuit SC becomes 0 (see FIG. 5C).
When the switch element S11 is turned off and the switch element S12 is turned on at time t11, the switch element S12, the capacitor C1, the switch elements S21, S31, S41, S51,
In the path of S61, the capacitor C1 moves the load Z in the negative direction.
Is connected to the output Vs of the switched capacitor circuit SC.
c becomes -E (see FIG. 5D). With the same control, the capacitors C2, C3, C4, and C5 are also connected in series in the negative direction, so that the output Vsc of the switched capacitor circuit SC is sequentially changed to -2E, -3E, -4E,
It changes stepwise as −5E (see FIGS. 6A to 6D). The output Vsc of the switched capacitor circuit SC is-
After reaching 5E, at time t16, the capacitor C5 is disconnected from the current path, and the output Vsc of the switched capacitor circuit SC becomes -4E (see FIG. 7A). Similarly, by separating the capacitors C4, C3, C2, and C1 from the current path, the output V of the switched capacitor circuit SC is reduced.
sc returns to zero at time t20 (see FIGS. 7B to 7D). Then, at time t20, all the switch rows A are turned off,
Turn on all the switch rows B and return to the initial state (FIG. 3
(A)). As described above, if the operation from time t1 to t20 is performed, the switched capacitor circuit SC becomes -5E-
An AC having an amplitude of 5E can be applied to the load circuit, and the filtering circuit of the load circuit filters the one-step staircase waveform output from the switched capacitor circuit SC into a smooth waveform. A smooth AC voltage Vz as shown in FIG. 2 can be supplied.

The charging of the capacitors C1 to C5 is performed as follows. When both the switch elements S42 and S51 of the switched capacitor circuit SC are on, the capacitors C3, C4, and C5 are connected in series. When the switch element S71 is turned on, the capacitor C3 is supplied by the DC power supply DC. , C4 and C5 are charged in series. Since the switch elements S42 and S51 are turned on at time t4 and the switch element S42 is turned off at time t9,
Charging is enabled between times t4 and t9 (FIG. 4A).
(D) and FIG. 5 (a)). Also, the switching element S
When both 21 and S32 are on, the capacitors C1, C2, and C3 are connected in series,
By turning on the switch element S72, the capacitor C1,
C2 and C3 are charged in series. In this case, time t11 to time t11
Charging is possible during t17 (see FIGS. 6A to 6D and FIG. 7A).

As described above, m capacitors (the output Vsc of the switched capacitor circuit SC: -mE to + mE)
In this case, the number of switch elements required for the switched capacitor circuit SC is 2 (m + 1), and four of the switch elements have a withstand voltage of E, and 2 (m-1) switch elements have a withstand voltage. 2E is required. For example, when m = 5 as in the present embodiment, the number of switch elements required is 12, and the number of switch elements required in Conventional Example 1 (= 20) is equal to three-fifths. An output Vsc is obtained. In addition, although the conventional example 2 is also composed of 12 switch elements, all 12 switch elements require a withstand voltage of 2E, whereas in the present embodiment, the switch elements requiring 2E withstand voltage are used. Eight switches are sufficient, and the remaining four switch elements can have a withstand voltage of E.

As described above, according to this embodiment, two switch elements are shared by adjacent capacitors, compared to the conventional example in which four switch elements are connected to one capacitor in a bridge shape. The number of switch elements of the switched capacitor circuit SC required to obtain the same output as in the conventional example can be reduced. as a result,
The number of level shift circuits for adjusting the drive pulse to the reference potential of each switch element can be reduced.
Moreover, since the number of switch elements having a high withstand voltage can be reduced at the same time as the number of switch elements as a whole, the chip area of the entire switch element can be reduced when the switched capacitor circuit SC is integrated. .

(Embodiment 2) FIG. 8 shows Embodiment 2 of the present invention.
(However, a DC power source D constituting a charging means is shown.)
Illustration of C and switch elements S71 and S72 is omitted. ). This embodiment is characterized in that a through current blocking means is connected in series with each of the capacitors C1 to C5 with respect to the configuration of the first embodiment. Therefore, the same reference numerals are given to the same configurations and operations as those of the first embodiment. The illustration and description are omitted.

As shown in FIG. 8, the connection point between the switching elements Sm1 and Sm + 1,1 and the switching elements Sm2 and Sm +
A series circuit of a through current blocking means F composed of a parallel circuit of a diode Dm and an inductor Lm (m = 1, 2, 3, 4, 5) and a capacitor Cm is connected between the connection points 1 and 2. .

The circuit operation of this embodiment will be described focusing on the differences from the first embodiment. When the output Vsc of the switched capacitor circuit SC switches, for example, the switching element S12
Current flows in the direction from the source terminal to the drain terminal of the switch element S12, the switch element S12 is turned off, and the switch element S11 is turned off.
Is turned on in the first embodiment, the capacitor C is set in parallel with the switch element S12 by the reverse recovery time of the diode.
1 → switching element S12 → spike-shaped through current flows through switch element S11 for a moment, and this through current causes switching noise. Thus, in the present embodiment, the through current can be suppressed by the inductor Lm of the through current blocking means F, and the switching noise can be reduced. The diode Dm is connected to the inductor L
This prevents a high voltage from being applied to the switch element by the back electromotive force of m. Note that the inductor Lm may be one that can suppress the current during the reverse recovery time of the diode, and may use a small inductor.

As described above, according to the present embodiment, by providing the through current blocking means F in series with each of the capacitors C1 to C5 of the switched capacitor circuit SC, the through current is prevented from flowing through the switch element. Thus, a smooth AC voltage can be supplied to the load Z while suppressing switching noise.

(Embodiment 3) A schematic circuit diagram of Embodiment 3 of the present invention is shown in FIG. 9, and a specific circuit diagram thereof is shown in FIG. 10 (however, a DC power source DC constituting a charging means, switch elements S71 and S72). Is omitted from the drawing). The basic configuration of this embodiment is the same as that of the first embodiment.
Therefore, the same reference numerals are given to the common parts, and the description is omitted.

In this embodiment, the switching elements S12 and S2
2, switch elements S21 and S31, switch element S32
And S42, switching elements S41 and S51, and switching elements S52 and S62 in parallel with high-frequency current sources H1 to H2, respectively.
5 is connected. That is, the current flowing in the switch element when each switch element switches from the off state to the on state starts from minus (source → drain), and the current flowing in the switch element when the switch element switches from the on state to the off state is positive ( By superimposing the high-frequency currents of the high-frequency current sources H1 to H5 so as to end with (drain → source), it is possible to prevent a through current flowing during the reverse recovery time of the diode connected in anti-parallel to the switch element.

For example, a current flowing into the load Z from the switched capacitor circuit SC at time t2 in FIG.
It is called “main current”. ) Isc is switch element S31, S
Focusing on the change to the paths 41, S51, and S61, since the current flows from the source to the drain of the switch element S32 immediately before time t2, the instantaneous value of each current at time t2 is Isc <I2 + I3 (where Im (m = 1,
2, 3, 4, and 5) select the current values and phases of the currents I2 and I3 so as to satisfy the relationship (high-frequency current flowing from the high-frequency current source Hm). Then, the current of the switch element S31 starts with the current flowing from the source to the drain,
It is possible to prevent a through current from flowing. Further, since the current flows through the switch element S42 in the drain → source direction, the current I4 is set so that Isc> I3 + I4.
Choose the current value and phase. Similarly, Isc <I4 + I
5. The current value and the phase of the current I5 are selected so that Isc> I5. As described above, when the state of the switch element is switched in the entire cycle, the current flowing through the switch element when the current of each switch element switches from the off state to the on state starts from a minus value, and the current is switched from the on state to the off state. The current I1 of the high-frequency current sources H1 to H5 is set so that the current flowing through the switch element at the time of switching ends with a plus.
By selecting the current value, frequency and phase of I5, it is possible to prevent a through current from flowing and to reduce switching loss and noise.

The high-frequency current sources H1 to H5 are, for example, as shown in FIG. 10, a series resonance circuit of an inductor Lim and a capacitor Cim (m = 1, 2, 3, 4, 5). And a configuration in which a high-frequency current is driven by driving as described above. At this time, the frequency, phase, and current value of the high-frequency current sources H1 to H5 can be adjusted by the resonance frequency of the series resonance circuit of the inductor Lim and the capacitor Cim and the respective constants. When the resonance frequency of the resonance circuit is at least three times the frequency of the output voltage of the switched capacitor circuit SC, loss and noise due to switching can be further reduced.

[0045]

According to a first aspect of the present invention, there are provided a plurality of capacitors serving as voltage sources, wherein a low potential side and a high potential side of adjacent capacitors are connected via switching elements, and capacitors at both ends are connected. A switched-capacitor circuit configured by connecting a series circuit of two switch elements in parallel to each other, and connecting a diode in parallel from the low potential side to the high potential side of the capacitors in parallel with all switch elements; and Means for charging from a voltage source, a load circuit connected between the connection points of two switch elements connected to both ends of the switched capacitor circuit, and the capacitor connected in series with an arbitrary number and an arbitrary polarity of the capacitors. Control means for controlling the on / off of the switching elements to supply an AC output to the load circuit, so that four switching elements are connected to one capacitor. Compared to the conventional example in which the two switching elements are shared by adjacent capacitors, the number of switching elements can be reduced without increasing the withstand voltage, and the chip area of the switching elements can be reduced. Therefore, there is an effect that the size can be reduced.

According to the second aspect of the present invention, the through current blocking means for blocking the through current flowing due to the parasitic capacitance of the switch element is connected in series with the capacitor, so that the switching current is reduced by blocking the through current. There is an effect that can be achieved.

According to a third aspect of the present invention, since the through current blocking means comprises a parallel circuit of an inductor and a diode,
There is an effect that a through current can be blocked with a simple configuration.

According to a fourth aspect of the present invention, a high-frequency current source is connected in parallel to a series circuit of two switch elements in which the directions of diodes connected in parallel to the switch elements of the switched capacitor circuit are alternately changed. As the current when the element switches from the off state to the on state flows in the forward direction with the diode, and the current when the element switches from the on state to the off state flows in the reverse direction with the diode,
Since the current flowing through the load circuit and the current from the high-frequency current source are superimposed, loss and noise due to switching can be reduced, and the circuit can be downsized. There is an effect that it can be used.

According to a fifth aspect of the present invention, the high-frequency current source comprises:
Since a high-frequency current is generated by the operation of each switch element using the capacitor serving as the voltage source as a power supply, the circuit configuration of the high-frequency current source can be simplified.

According to the sixth aspect of the present invention, since the resonance frequency of the resonance circuit is at least three times the frequency of the output voltage of the switched capacitor circuit, the effect of further reducing loss and noise due to switching can be achieved. is there.

According to a seventh aspect of the present invention, since a filtering circuit for filtering a discontinuous output voltage of the switched capacitor circuit is connected between the switched capacitor circuit and the load, noise of a voltage applied to the load is reduced. There is an effect that can be.

According to the eighth aspect of the present invention, since a substantially sinusoidal current is supplied to the load by the switched capacitor circuit and the filtering circuit, the noise of the voltage applied to the load can be reduced.

[Brief description of the drawings]

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

FIG. 2 is an operation explanatory view of the above.

FIGS. 3 (a) to 3 (d) are operation explanatory diagrams of the above.

FIGS. 4A to 4D are explanatory diagrams of the operation of the above.

FIGS. 5A to 5D are explanatory diagrams illustrating the operation of the above.

FIGS. 6 (a) to 6 (d) are operation explanatory diagrams of the above.

FIGS. 7A to 7D are explanatory diagrams illustrating the operation of the above.

FIG. 8 is a circuit diagram of a second embodiment.

FIG. 9 is a circuit diagram of a third embodiment.

FIG. 10 is a specific circuit diagram of the above.

FIG. 11 is a circuit diagram of Conventional Example 1.

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

FIG. 13 is a circuit diagram of a second conventional example.

FIG. 14 is an operation explanatory view of the above.

[Explanation of symbols]

 C1 to C5 Capacitors S11 to S72 Switch element SC Switched capacitor circuit Z Load

Claims (8)

[Claims] 1. A capacitor comprising a plurality of capacitors serving as voltage sources, wherein a low potential side and a high potential side of adjacent capacitors are connected via switch elements, respectively, and two switch elements are connected in series to capacitors at both ends. A switched capacitor circuit in which circuits are connected in parallel with each other, and a diode is connected in parallel from the low potential side to the high potential side of the capacitor in parallel with all switch elements, and means for charging each capacitor from a voltage source A load circuit connected between the connection points of two switch elements connected to both ends of the switched capacitor circuit, and an on / off control of the switch elements such that the capacitors are connected in series with an arbitrary number and an arbitrary polarity; And a control means for supplying an AC output to the load circuit. 2. A switch according to claim 1, wherein a through current blocking means for blocking a through current flowing due to a parasitic capacitance of said switch element is connected in series with said capacitor.
The power converter according to any one of the preceding claims. 3. The power converter according to claim 2, wherein said through current blocking means comprises a parallel circuit of an inductor and a diode. 4. A high-frequency current source is connected in parallel to a series circuit of two switch elements in which the direction of a diode connected in parallel to the switch element of the switched capacitor circuit is alternated, and each switch element is turned off. The current when switching to the on state flows in the forward direction with the diode,
The current flowing through the load circuit and the current from the high-frequency current source are overlapped so that the current when switching from the on state to the off state flows in the opposite direction to the diode. Power converter. 5. The high-frequency current source comprises a series resonance circuit of an inductor and a capacitor, and generates a high-frequency current by operating each switch element using the capacitor as the voltage source as a power supply. Power converter. 6. The power converter according to claim 5, wherein the resonance frequency of the resonance circuit is at least three times the frequency of the output voltage of the switched capacitor circuit. 7. The power conversion device according to claim 1, wherein a filtering circuit for filtering a discontinuous output voltage of the switched capacitor circuit is connected between the switched capacitor circuit and the load. 8. The power converter according to claim 7, wherein a substantially sinusoidal current is supplied to the load by the switched capacitor circuit and the filtering circuit.