JPH1042576A - Power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable setting the breakdown voltage of switching elements to a low value and further reduce the sum of the chip area of the switching elements, by series-connecting a combination of cells which differ in output voltages, and making a switched capacitor circuit output a voltage higher than that of the cells in the combined number. SOLUTION: Three capacitor cells SC1, SC2, SC3 are used, and capacitors C1, C2, C3, C4 are charged at a voltage different from the direct-current supply voltage. These are combined to reduce the number of switching elements, and yet positive and negative voltages in five levels are generated. This enables reducing the number of switching elements and simplifying a control circuit, and enables the reduction of supply voltage and the breakdown voltage for each switching element.

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 a high-frequency AC voltage using a switched capacitor circuit.

[0002]

2. Description of the Related Art Conventionally, there is a circuit as shown in FIG. 18 as a power conversion circuit for obtaining a smooth AC output from a DC power supply using a minute inductor and a switched capacitor. In the circuit configuration of this conventional example, a series circuit of a diode Dj, a unidirectional switch element Sj1, and a capacitor Cj (j = 1 to 5) is connected in parallel, and a single DC power supply DC is connected via a switch element Ss and an inductor L1. This parallel circuit is connected, a diode Ds is connected between the intersection of the switch element Ss and the inductor L1 and the ground, and capacitors C1 to C
5 is constituted. Further, unidirectional switch elements (for example, MOSFETs) Sj2a, Sj2b (j = 1 to 5)
Bidirectional switch element (Fig. 1)
9) and a capacitor Cj are connected in parallel, and connected to the load circuit 1 via an inductor L2 to form a power conversion unit, which is composed of these control circuits (not shown in the figure). The load circuit 1 includes a parallel circuit of a load Z, a full bridge circuit including switch elements Sz1 to Sz4 for inverting the output polarity to the load Z, and a load capacitor Cz.

The operation of this circuit will be described. Capacitors C1 to C1 are supplied from a DC power supply DC via an inductor L1.
C5 is charged with different voltages in a voltage relationship of V10 <V20 <V30 <V40 <V50, and the capacitors C1 to C5 are sequentially connected to the load circuit 1 one by one via the inductor L2 to smoothly change the load voltage. Then, an AC voltage is supplied to the load Z. Also, the minute inductors L1, L2
The power transmission efficiency is improved by transmitting the power in a resonant manner via the.

Further, there is a circuit as shown in FIG. 20 as another conventional example. In this conventional example, a plurality of capacitors (C1
To C5) with the DC power supply DC (voltage E) at once.
By discharging an arbitrary number of capacitors in series to an arbitrary polarity, -5E, -4E, -3E, -2E,-
A switched capacitor circuit SC capable of supplying voltages Vsc of E, 0, E, 2E, 3E, 4E, and 5E.
z and a small capacitor Cz
And a load Z connected in parallel.

The configuration of the switched capacitor circuit SC includes 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 is a connection point between Sm1 and Sm2 and Sn3. The connection is made in series by connecting the connection points of Sn4 (m ≠ n). Further, when these switch elements are realized by MOSFETs having antiparallel diodes, each of the switch elements Sm1, Sm2 and Sm
3, 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, a control method for supplying an AC voltage to the load Z will be described with reference to FIG. As an 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. At time t0, switch element S13
Is turned off and the switch element S14 is turned on, the switch element S11, the capacitor C1, the switch element S14, the switch elements S21, S23, S31, S33, S41, S
43, S51, and S53, the capacitor C1 is connected to the load Z in the positive direction, and the output Vsc of the switched capacitor circuit SC becomes + E. When the switch element S23 is turned off and the switch element S24 is turned on at time t1, the switch element S11, the capacitor C1, and the switch element S1 are turned on.
4, S21, capacitor C2, switch element S24, S
31, S33, S41, S43, S51, and S53, the capacitors C1 and C2 are connected in series to the load Z in the plus direction, and the output Vs of the switched capacitor circuit SC is output.
c becomes + 2E. By the same control, the capacitor C
3, C4, and C5 are also connected in series in the positive direction, so that the output Vsc of the switched capacitor circuit SC sequentially increases in a stepwise manner to + 3E, + 4E, and + 5E.

Next, when the switching element S54 is turned off and the switching element S53 is turned on at time t3, 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 t4, 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 t5 when charging is completed, switch element S6 is turned off, switch element S11 is turned off, and switch element S12 is turned off.
Is turned on, the switch element S12, the capacitor C1,
Switch elements S13, S21, S23, S31, S3
3, the capacitor C1 is connected to the load Z in the negative direction through the paths of 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 t7, the capacitor C5 is disconnected from the current path, and the output Vsc of the switched capacitor circuit SC becomes -4E. Similarly, by disconnecting the capacitors C4, C3, C2, and C1 from the current path, the output Vsc of the switched capacitor circuit SC returns to zero at time t8. As described above, if the operation at the times t0 to t8 is performed, the switched capacitor circuit SC applies the AC having the amplitude of −5E to 5E in a stepwise manner to the load Z.
Is applied. The small inductor Lz and the small capacitor Cz in the load section are connected to the output 1 of the switched capacitor circuit SC.
If the step waveform of the step is filtered to obtain a smooth waveform, a smooth AC voltage Vz as shown in FIG.

[0010]

In the first conventional example, power with less harmonic distortion can be supplied to a load by combining a switched capacitor circuit, a small LC filter, and a bridge circuit. Since a plurality of capacitors having different voltages are sequentially switched and used in parallel, each switch element needs to have a withstand voltage corresponding to the maximum output voltage. Generally, the chip area A of the double-diffused MOSFET is a voltage BVdss having a constant withstand voltage BVds between the drain and the source (approximately 100 V in current commercial devices).
If it is above, the on-resistance Ro is proportional to the square of BVgs, and
It tends to be inversely proportional to n. Furthermore, the chip area does not tend to become very small even if the breakdown voltage falls below BVdss. Therefore, a chip with a high breakdown voltage tends to have a large chip area. Further, in order to realize one bidirectional switch, two one-way switch elements Qa and Qb are required as shown in FIG. 19, so that the number of switch elements increases, and when viewed as a whole power conversion circuit, In addition, the total chip area of the switching elements becomes considerably large.

On the other hand, in the second conventional example, 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. A switch element having a low withstand voltage 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 whose reference potential fluctuates, so that the control circuit becomes complicated.

As described above, in the conventional example, there is a problem that a switch element having a high withstand voltage and a large area is required, or the number of switch elements is increased, and a control circuit is complicated.

[0013]

According to the present invention, in order to solve the above-mentioned problems, at least one set of cells comprising a capacitor as a voltage source and a bridge circuit for inverting the polarity of the capacitor is connected in series. Means connected to a load in parallel with the load, and a means for charging the capacitor of the cell in parallel from a voltage source. In a power converter that performs control for supplying an AC output, the switched capacitor circuit outputs a voltage equal to or greater than the number of cells by combining and serially connecting the cells having different output voltages. is there.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is shown in FIG. In the second conventional example described above, five capacitors C1 to C5 are equally charged to the same voltage E from the DC power supply DC, and these are combined in series to generate voltages of five positive and negative levels, respectively. In the circuit of the above, there are three switched capacitor cells SC1, SC2, SC3,
The capacitors C1 and C2 are charged to a voltage different from 2E and the capacitors C3 and C4 are charged to a voltage different from E, and E, 2E, E + 2E, 2E +
2E, E + 2E + 2E, and a combination thereof, to generate a voltage of five positive and negative levels even if the number of switch elements is reduced as compared with the second conventional example.

The description will focus on the differences from the second conventional example.
The DC power supply DC has a voltage of 2E. The switched capacitor circuit SC includes three switched capacitor cells SC1 to SC1.
In the switched capacitor cell SC3 including SC3, two capacitors C3 and C4 having the same capacitance and diodes D31 to D31 are substituted for one capacitor C3.
33 are connected. The operation of the switched capacitor cell SC3 is as follows. Since the switch row A is on at the time of charging, when the switch element S6 is on, the diode D31 is forward-biased, and the DC power supply DC, the diode D3, the capacitor C4,
Diode D31, capacitor C3, switch element S3
1. The capacitors C3 and C4 are charged in series along the path of S23. The diodes D33 and D32 are off due to reverse bias. Here, if the initial charges of the capacitors C3 and C4 are equal, they are charged to the same voltage E, respectively. When the switching elements S31 and S34 are turned on and the switched capacitor cell SC3 is connected to the load Z at a positive voltage, the current of the switched capacitor cell SC3 becomes equal to the switching element S3.
When the capacitors C3 and C4 are to be discharged, the diode D31 is reverse-biased and turned off, and the diodes D32 and D33 are forward-biased and turned on.
3, capacitor C4, path of switch element S34 and switch element S31, capacitor C3, diode D3
2. Connected in parallel to the load Z on the path of the switch element S34, the switched capacitor cell SC3 applies the voltage E to the load Z. On the other hand, when the switching elements S32 and S33 are turned on and the switched capacitor cell SC3 is connected to the load Z with a negative voltage, the switched capacitor cell SC3
Flows in the direction from the switch element S33 to S32.
When current flows through the capacitors C3 and C4, the diode D31 is reverse-biased and turned off, and the diode D31 is turned off.
32 and D33 are forward-biased and turned on, and switch element S33, diode D33, capacitor C4, the path of switch element S32 and the path of switch element S33, capacitor C3, diode D32, and switch element S32 are applied to load Z in parallel. Connected, switched capacitor cell SC3 applies voltage -E to load Z. Capacitor C
3, C4 repeatedly charges and discharges under the same conditions each time, so that the voltage becomes Vc3 = Vc4 = E.

The overall operation of the circuit shown in FIG. 1 will be described with reference to FIG. As an initial state, the capacitors C1 and C2 are connected to the power supply voltage 2
It is assumed that E, the capacitors C3 and C4 are charged with E, the switch row A is all on, and the switch row B is all off. When the switch element S33 is turned off and the switch element S34 is turned on at time t0, the switch element S11,
Via S13, S21, S23, and S31, a series circuit of the capacitor C3 and the diode D32 and the diode D3
The capacitor C3 and the capacitor C4 are connected in parallel in the plus direction along the path of the switch element S34, and the output Vsc of the switched capacitor circuit SC becomes + E. Next, at time t1, switch element S34 is turned off, and switch element S3 is turned off.
3 on, switch element S13 off, switch element S
14, when the switch element S11 and the capacitor C
1, switch elements S14, S21, S23, S31, S
33, the capacitor C1 is connected to the load Z in the plus direction, and the output Vsc of the switched capacitor circuit SC is output.
Becomes + 2E. Next, at time t2, the switch element S33
Is turned off and the switch element S34 is turned on, the parallel circuit of the capacitor C1 and the capacitors C3 and C4 is connected in series, and 2E + E = 3E is connected to the load Z in the plus direction. Hereinafter, as shown in FIG. 2, the capacitors C1 and C2 are connected in series to obtain 2E + 2E = 4E, and the capacitors C1 and C2
And a parallel circuit of the capacitors C3 and C4 are connected in series, and 2E + 2E + E = 5E is sequentially applied to the load Z.

Next, at times t3 to t4, times t0 to t
Contrary to 3, the series capacitor is sequentially disconnected, and the output Vsc is lowered stepwise to 4E, 3E, 2E, E, 0. At time t4, when all the capacitors are disconnected from the load current path, all the switch rows A are turned on, and all the switch rows B are turned off, the switch element S6 is turned on to connect the capacitors C1, C2 and the series circuit of the capacitors C3 and C4. Are charged in parallel from the DC power supply DC. At time t5 when charging is completed, switch element S6 is turned off, and switch element S31 is turned off.
Is turned off and the switch element S32 is turned on, via the switch elements S11, S13, S21, S23 and S32,
A circuit in which a series circuit of a capacitor C3 and a diode D32 and a series circuit of a diode D33 and a capacitor C4 are connected in parallel;
3, C4 is connected in parallel to the load Z in the negative direction,
The output Vsc of the switched capacitor circuit SC becomes -E. Thereafter, the capacitor C1 is connected in the minus direction to
2E, a parallel circuit of the capacitor C1 and the capacitors C3 and C4 are connected in series in the minus direction to -3E, and a series circuit of the capacitor C1 and C2 are connected in series to the minus direction and -4E, and a series circuit of the capacitors C1 and C2 and the capacitor C3. , C4
Are connected in series in the minus direction to -5E, and the output Vsc of the switched capacitor circuit SC changes stepwise in the order of -2E, -3E, -4E, -5E. At times t7 to t8, the series capacitors are sequentially disconnected in the reverse of the times t5 to t7, and -4E and -3 are stepped.
By changing the output Vsc to E, -2E, -E, the output Vsc of the switched capacitor circuit SC returns to zero at time t8.

As described above, if the operation at times t0 to t8 is performed, the switched capacitor circuit SC applies an AC voltage having an amplitude of -5E to 5E to the load Z in a stepwise manner. If the small inductor Lz and the small capacitor Cz of the load section filter the one-step staircase waveform output from the switched capacitor circuit SC into a smooth waveform, the load Z can be applied to the load Z as shown in FIG.
A smooth AC voltage Vz as shown in FIG.

As described above, in the power conversion circuit of the present invention shown in FIG. 1, the same output as that of the five-stage switched capacitor cell circuit shown in the second conventional example is constituted by three-stage switched capacitor cells. Also, the number of switch elements constituting the switched capacitor unit can be reduced to three fifths, and the control circuit can be simplified. Further, the power supply voltage and the withstand voltage of each switch element are twice as large as those of the second conventional example, but can be suppressed to two fifths of the maximum output voltage.

FIG. 3 shows a circuit diagram of an embodiment of the present invention. In the present embodiment, by connecting a switch element S35 in anti-parallel to the diode D31 in the basic circuit of FIG. 1, the capacitors C3 and C4 can be discharged in series, and outputs of positive and negative 6 levels are possible. When charging the switched capacitor cell SC3, the diode D3 is charged from the DC power supply DC (voltage 2E) through the capacitor C4, the diode D31 and the capacitor C3 as in the basic circuit of FIG. If the initial charges of the capacitors C3 and C4 are equal, both the capacitors C3 and C4 are charged to the voltage E.
When the switched capacitor cell SC3 applies + E or -E to the load Z, the switch element S35 is turned off, and the series circuit of the capacitor C3 and the diode D32 and the diode D33 and the capacitor are turned off as in the basic circuit of FIG. C4 series circuits are connected in parallel and output. When the switched capacitor cell SC3 applies + 2E or -2E to the load Z, the switch element S35 is turned on, and the voltage of + 2E or -2E is applied to the series circuit of the capacitor C3, the switch element S35, and the capacitor C4. Output.

The overall operation of this embodiment will be described with reference to FIG. The difference from the basic circuit of FIG. 1 is that the capacitors C3 and C4
Are connected in parallel, and when the output Vsc of the switched capacitor circuit SC is + 5E, the switch element S35 is turned on at time t3, and the switch element S11, the capacitor C1, the switch elements S14, S21, the capacitor C2,
A current flows through the paths of the switch elements S24 and S31, the capacitor C3, the switch element S35, the capacitor C4, and the switch element S34, and the output Vsc of the switched capacitor circuit SC becomes + 6E. Similarly, at time t8, the switch element S35 is turned on to connect the capacitors C3 and C4 in series and output -6E. Since the capacitors C3 and C4 are connected in parallel or connected in series and are discharged uniformly, the capacitors C3 and C4 are both charged to the voltage E during the series charging.

By outputting a step-like voltage of 6 levels to the load circuit by the control as described above, the positive and negative 5 levels are output.
A finer voltage is output than at the time of the level, and a smoother load voltage can be obtained by the smaller filter circuits Lz and Cz. Further, since the boost ratio with respect to the power supply voltage is tripled, the power supply voltage can be reduced to 5/6 compared to the basic circuit of FIG. 1, and the withstand voltage of each switch element can be reduced in proportion thereto. Become. Further, when a vertical MOSFET is used as the switch element S35, the diode D31 can be used instead of the body diode.

FIG. 5 shows a circuit diagram of another embodiment of the present invention. The above-described embodiment of FIG. 3 combines four capacitors C1 to C4 having voltages of E, E, 2E, and 2E to add positive and negative
In contrast to the output of the voltage of level 3, in the present embodiment,
Three capacitors C1 to C3 having voltages of E, 2E and E
To enable output of six levels of positive and negative.

Hereinafter, the embodiment of FIG. 5 will be described focusing on differences from the embodiment of FIG. The DC power supply DC has a voltage of 3E. The switched capacitor circuit SC includes two switched capacitor cells SC1 and SC2. Among them, the switched capacitor cell SC2 is similar to the switched capacitor cell SC3 of the embodiment of FIG. A switch element S27 is connected in anti-parallel to a diode D21 between two capacitors C2 and C3. Further, switch elements S25 and S26 are connected in series with diodes D23 and D22 for connecting the capacitors C2 and C3 in parallel. Connect. Also, the capacitor C3
Is set to be twice as large as the capacitor C2. Therefore,
When the capacitors C2 and C3 are charged in series, the voltage becomes V
c2 = 2 × Vc3. Therefore, capacitors C2, C
When the 3 series circuit is charged with 3E, Vc2 = 2E, Vc
3 = E.

In this embodiment, unlike the embodiment shown in FIG. 3, only one of the capacitors C2 and C3 is connected to the load circuit by turning off one of the newly connected switch elements S25 and S26. It is possible to do.
For example, the switch element S25 is turned on, and the switch element S2 is turned on.
6. By turning off S27, the output of the switched capacitor cell SC2 becomes E with only the capacitor C3.
Further, the switch element S26 is turned on, and the switch element S2 is turned on.
5. By turning off S27, the output of the switched capacitor cell SC2 becomes 2E with only the capacitor C2. Further, by turning on the switch element S27 and turning off the switch elements S25 and S26, the output of the switched capacitor cell SC2 becomes 3E by connecting the capacitors C2 and C3 in series. The capacitor C1 has a power supply voltage of 3
Since E is charged to E, C1, C2, and C3 are combined in series to obtain E (= C
3), 2E (= C2), 3E (= C1), 4E (= C1)
+ C3), 5E (= C1 + C2), 6E (= C1 + C2)
+ C3) output of 6 levels of positive and negative.

As described above, in the present embodiment, the power supply voltage (3
Although the boosting ratio of the output voltage Vsc with respect to E) is as small as twice, it is possible to obtain the same output as the embodiment of FIG. 3 by using two switched capacitor cells.

If the direct-current power supply DC is directly connected as in the embodiment of FIG. 7 instead of the capacitor C1 in the embodiment of FIG. 5, the switched capacitor circuit SC
Can be constituted by two capacitors C2 and C3. In the embodiment of FIG. 7, the capacitor C2,
To charge C3, switch element S from DC power supply DC
6. Capacitor C via backflow prevention diode D2
3, connected to a series circuit of a diode D21 and a capacitor C2 to charge the series circuit of the capacitors C2 and C3 at the same timing as the timing of charging each capacitor in the above embodiments.

In each of the above embodiments, a single DC power supply DC
A plurality of capacitors are charged with different voltages, and these are combined to obtain a multi-level step-like waveform, and a smooth output waveform is obtained by a minute filtering circuit. On the other hand, in the embodiment of FIG. 8, a plurality of capacitors are charged with different voltages by different power sources. In the circuit of FIG. 8, different DC voltage sources DC1, DC
2 and DC3 are respectively connected to switch elements S16, S26, S
36 and capacitors C1, C2, C3 via a backflow prevention diode D1, D2, D3. Since the capacitors C1 to C3 are independently charged by the different DC voltage sources DC1 to DC3, they can be charged to different voltages. Here, for example, DC1 = E, DC2 = 2E, DC
Assuming that C1 = E, C2 = 2E, and C3 = 3E at 3 = 3E, the capacitor C1 is charged as in the embodiment of FIG.
To C3 can be combined in series to output positive and negative 6 levels.

In the embodiment shown in FIG. 9, similarly to the embodiment shown in FIG. 8, different voltages are charged to a plurality of capacitors by different power sources. In this embodiment, DC voltage sources DC1 and DC2 are particularly used. , DC3 each have the same voltage of E, which are connected in series, and the capacitor C1 is connected to the switch element S1 from the connection point of the DC voltage sources DC1 and DC2.
6. E is connected through the diode D1, and the capacitor C2 is connected to the switch element S from the connection point of the DC voltage sources DC2 and DC3.
26, DC voltage source DC1 and DC via diode D2
2 is connected to the DC voltage source D by the capacitor C3.
From the series circuit of C1, DC2 and DC3, switch element S3
6. Charge the voltage of 3E via the diode D3. In this manner, the capacitors C1 to C3 are charged with E, 2E, and 3E, and a step-like output having six levels of positive and negative can be obtained as in the embodiment of FIG. The DC voltage sources DC1 to DC1 of the present embodiment
The DC3 can be easily configured with a battery power source such as a dry cell or a solar cell, can output a voltage higher than the series voltage of the batteries and a voltage higher than the number of batteries, and does not require a large resonance circuit. Therefore, DC
-It is possible to reduce the size of battery devices that require AC conversion.

Next, in the embodiment of FIG. 10, the power supply of the switched capacitor circuit SC in the basic circuit of FIG.
A multi-stage output voltage is obtained by using different voltage sources. Specifically, a DC voltage source DC1 having a voltage of 2E,
DC2 is connected in series similarly to the embodiment of FIG. 9, and the negative side of the DC voltage source DC2 is connected to the negative side of the capacitor C2. A diode D2 and a capacitor C are connected from a connection point between the DC voltage sources DC1 and DC2 via the switch element S26.
The series circuit of No. 2 is connected to a series circuit of a capacitor C3, a diode D31 and a capacitor C4 via a diode D3. Also, the capacitor C1 is connected from the DC voltage source DC1 via the switch element S16 and the diode D1.

As shown in FIGS. 11 and 12, the operation of the present embodiment turns on the switches S16 and S26 at time t8, and charges the capacitor C1 with 4E from the series circuit of the DC voltage sources DC1 and DC2. C2 is a DC voltage source D
Charging with C2 to 2E, capacitors C3 and C4 are connected in series and charging with DC voltage sources DC2 to 2E, resulting in capacitors C3 and C4 each charging E.

The discharge to the load Z is performed by the capacitors C3 and C4.
Are connected in parallel, E is connected in parallel with the capacitors C2 to 2E, the capacitors C3 and C4 are connected in series, and the capacitor C2 is connected in series to 3E, the capacitors C1 to 4E, and the capacitors C3 and C are connected.
4 and the capacitor C1 are connected in series, 5E. The capacitors C2 and C1 are connected in series, 6E.
3, C4 is connected in parallel, and capacitors C2 and C1 are connected in series, and seven voltage levels of 7E are combined to output positive and negative 14 levels.

As described above, in the present embodiment, a finer level of voltage can be output by using a plurality of voltage sources as a power supply for charging a capacitor in the basic circuit of FIG.

Each of the embodiments shown in FIGS. 1 to 7 charges a plurality of capacitors from a single power supply with different voltages.
In each of the embodiments described above, the plurality of capacitors were charged with different voltages from the plurality of power supplies, whereas the embodiment of FIG. 13 charged the plurality of capacitors with different voltages from the power supply whose voltage fluctuated over time, and combined these capacitors. A multi-level step-like waveform is output, filtered by a minute filter, and converted into AC power. As shown in FIG.
The output Vi obtained by full-wave rectification of the AC power supply AC by the diode bridge circuit DB changes every moment as shown in FIG. When the capacitor C1 is charged to the voltage E1, the capacitor C2 is charged to the voltage E2, and the capacitor C3 is charged to the voltage E3, the switch element S16 is turned on around the times t1 and t5 when the full-wave rectified output Vi becomes the voltage E1 to charge the capacitor C1. Then, before and after times t2 and t4 when the full-wave rectified output Vi becomes the voltage E2, the switch element S26 is turned on to charge the capacitor C2, and before and after the time t3 when the full-wave rectified output Vi becomes the voltage E3, the switching element S36 is turned on. Is turned on to charge the capacitor C3. Since the timing for charging the capacitors C1, C2, and C3 is limited in the cycle in which the full-wave rectified output Vi changes, the capacitance of the capacitors C1, C2, and C3 is set to be large so that the voltage change due to charging and discharging is reduced. There is a need. However, when a single DC power supply DC such as the basic circuit of FIG. 1 is obtained by smoothing the commercial AC power supply, the input current is greatly distorted. In this embodiment, the input current is divided into five times per half cycle of the AC. , The distortion of the input current is smaller than in a single capture. When the level of the voltage to be taken is further increased, the distortion of the input current is further reduced.

In the embodiment of FIG. 15, instead of the multiple power supplies in the embodiment of FIG. 10, similarly to the embodiment of FIG. C4 is charged. In particular, when the AC power supply is rectified and used, the number of steps can be increased compared to the embodiment of FIG. 13 and a finer step voltage is output, so that the filter circuit composed of the small inductor Lz and the small capacitor Cz can be further improved. Can be reduced in size.

FIGS. 16 and 17 show the circuit of the embodiment shown in FIG. 3 in which the load Z is a discharge lamp, and a binary control of the discharge lamp applied voltage allows stable lighting without specially providing a ballast. It is. When a voltage Vh higher than the characteristic voltage Vla of the discharge lamp is applied, the lamp current Ila increases and runs away, and when a voltage Vl lower than the characteristic voltage Vla is applied, the lamp current Ila decreases and the discharge lamp extinguishes. Therefore, assuming that the voltage of the DC power supply DC is 2E, the characteristic voltage Vla of the discharge lamp is larger than 4E and smaller than 5E, that is, the power supply voltage is 0.4 to 0.5 times the characteristic voltage Vla. Set.

FIG. 16 is similar to the operation of FIG. 4, and the voltage Vh higher than the characteristic voltage Vla is applied to the discharge lamp, so that the discharge lamp tends to run away. When the lamp current Ila is detected and becomes equal to or greater than the set value, the capacitors C3 and C4 are output in parallel without turning on the switch element S35 at the timing (t13 to t14) when the output Vsc becomes maximum as shown in FIG. An AC voltage having an amplitude of ± 5E is supplied. At this time, since the voltage Vl lower than the characteristic voltage Vla is applied to the discharge lamp, the discharge lamp tends to extinguish, and the lamp current Ila decreases. When the lamp current Ila is detected and becomes equal to or less than the set value, the operation returns to the operation of FIG.
At the timing when sc becomes maximum, the switch element S35 is turned on, the capacitors C3 and C4 are connected in series to output 6E, and a voltage Vh higher than the characteristic voltage Vla is supplied to the discharge lamp.

By switching the above operations and outputting binary values while detecting the lamp current Ila, the discharge lamp can be lit stably. Therefore, the only switch element that is directly controlled is the ON / OFF operation of S35, and stable ballastless lighting can be easily realized. In addition, the same operation as the present embodiment can be performed by the same control in the other embodiments described above.

In each of the above embodiments, an example in which a MOSFET is used as a switching element has been described. However, it goes without saying that any switching element such as a bipolar transistor has the same effect.

[0040]

According to the power converter of the present invention, by applying a switched capacitor, a high-frequency AC output can be obtained by boosting from a DC voltage source without using large resonance L and C. A sine waveform with less harmonic distortion can be output with only a small filter circuit. Further, by combining capacitors having different voltages, a voltage of a level higher than the number of capacitors can be output, so that the circuit configuration and the control circuit can be simplified.
In addition, since the withstand voltage of the switch elements constituting the switched capacitor circuit can be set low, when the switch elements are integrated on a semiconductor, the total chip area of the switch elements when viewed as a whole can be reduced. effective.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of the circuit of FIG. 1;

FIG. 3 is a circuit diagram according to a second embodiment of the present invention.

FIG. 4 is an operation explanatory diagram of the circuit of FIG. 3;

FIG. 5 is a circuit diagram of a third embodiment of the present invention.

FIG. 6 is an operation explanatory diagram of the circuit of FIG. 5;

FIG. 7 is a circuit diagram of a fourth embodiment of the present invention.

FIG. 8 is a circuit diagram of a fifth embodiment of the present invention.

FIG. 9 is a circuit diagram of a sixth embodiment of the present invention.

FIG. 10 is a circuit diagram of a seventh embodiment of the present invention.

FIG. 11 is an operation explanatory diagram showing control signals of the circuit of FIG. 10;

FIG. 12 is an operation explanatory diagram showing output waveforms of the circuit of FIG. 10;

FIG. 13 is a circuit diagram of an eighth embodiment of the present invention.

FIG. 14 is an operation explanatory diagram of the circuit in FIG. 13;

FIG. 15 is a circuit diagram of a ninth embodiment of the present invention.

16 is an operation explanatory diagram showing an output waveform at the time of high voltage output of the circuit of FIG. 15;

FIG. 17 is an operation explanatory diagram showing an output waveform at the time of low voltage output of the circuit of FIG. 15;

FIG. 18 is a circuit diagram of Conventional Example 1.

FIG. 19 is a circuit diagram of a bidirectional switch element used in Conventional Example 1.

FIG. 20 is a circuit diagram of a second conventional example.

FIG. 21 is an operation explanatory diagram of Conventional Example 2.

[Explanation of symbols]

 C1 to C3 Capacitor D1 to D3 Diode S11 to S34 Switch element Z Load

Claims (9)

[Claims] A switched capacitor circuit comprising a series of one or more cells each comprising a capacitor serving as a voltage source and a bridge circuit for inverting the polarity of the capacitor is connected to a load, and a capacitor of the cell is connected from a voltage source. A power conversion device comprising means for charging in parallel and controlling the supply of AC output to a load by connecting the capacitors of the cells in an arbitrary number and an arbitrary polarity in series. A power converter wherein the switched capacitor circuit outputs a voltage equal to or greater than the number of cells by connecting in series with each other. 2. The power converter according to claim 1, wherein a part of the cells is constituted by a switched capacitor circuit that performs serial charging and parallel discharging. 3. The power converter according to claim 1, wherein a part of the cell is constituted by a plurality of capacitors,
A power converter wherein a power supply voltage is divided at an arbitrary ratio and charged, and the plurality of capacitors output independently or in series. 4. The power converter according to claim 1, wherein a capacitor having a maximum voltage among the capacitors is replaced with a DC voltage source. 5. The power conversion device according to claim 1, wherein there are a plurality of said voltage sources, each of said voltage sources has a different voltage, and said cell is charged with a different voltage. 6. The power converter according to claim 1, wherein said voltage source is composed of a plurality of series voltage sources, and said cell is charged with a voltage different from an intermediate potential of said series voltage source. Power converter. 7. The power converter according to claim 1, wherein the voltage source is a time-varying voltage source, and the cells are charged to different voltages by charging the cells at different timings. Characteristic power converter. 8. The power conversion device according to claim 1, wherein the load is a discharge lamp. 9. The power converter according to claim 8, wherein the amplitude of the output voltage of the switched capacitor circuit is alternately switched to a binary value larger or smaller than the characteristic voltage of the discharge lamp by rearranging the cells. A power converter characterized by the above-mentioned.