JPH0667181B2 - DC / DC converter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a DC / DC converter, and more particularly to a reactor and a switching device for converting a DC voltage into a DC voltage higher than the DC voltage or a DC voltage with a negative polarity. The present invention relates to a DC / DC converter using an element.

(Prior Art) FIG. 21 is a typical circuit diagram of a conventional step-up DC / DC converter, and FIG. 22 is a DC / D circuit of FIG.
FIG. 22 is a voltage / current waveform diagram in the C converter,
Figure (a) shows the power supply voltage E _S , the voltage at point P, and the output voltage V0
And FIG. 22 (b) is a current waveform diagram of each part. In FIG. 21, reference numeral E _S is a DC power supply, L is a reactor, S is a switching element, D is a diode, and C is a smoothing capacitor.

By the way, a conventional DC / DC having such a configuration
In the case of the converter, the switching element S is on during the period from time t1 to t2 in FIG. 22, and the power supply voltage E _S is applied to the reactor L during this period, and the current iL
(Equal to i1) increases. During the period from time t2 to t3, the switching element S is off, and the current iL decreases during this period. In this case, the output voltage V0 is always higher than the power supply voltage E _S , and the voltage at the point P changes between zero and a value higher than the power supply voltage E _S. The power supply current is the average value of the current iL, and the output current 10 is the average value of the current iD (equal to i3). Then, as is apparent from the change in the voltage at the point P, an AC voltage having an amplitude corresponding to the output voltage V0 is applied to the reactor L, so that a reactor L having a considerably large inductance is required to smooth the current, This increases the size of the reactor L. Further, the switching element S must operate so as to switch a current corresponding to the output voltage V0 and corresponding to the power supply current. The voltage / current waveform diagram at the time of switching of the switching element S in this case is shown in FIG.
It becomes like the figure. That is, the turn of the switching element S
When it is on, the current is 0 to i when the output voltage V0 is applied.
It increases to L and then the voltage changes from V0 to 0.
At turn-off, the voltage increases from 0 to V0 while the current iL is still flowing, and the current iL starts flowing through the diode D, and then the current of the switching element S starts to decrease to zero. Become. In this case, the power required by the switching element S for switching is V0 · i.
Since the maximum point of L is passed, the power consumption of the switching element S increases.

(Purpose) The present invention has been made in view of such circumstances, and is a DC / D provided with a reactor and a switching element.
An object of the present invention is to make it possible to reduce the size and weight of the reactor in the C converter and reduce the power loss in the switching element.

(Structure of the Invention) In order to achieve such an object, the present invention provides a DC voltage converter between a reactor connected to a DC power supply and a capacitor for smoothing an output voltage, and the DC voltage converter The first switching device includes first and second switching elements, a charging / discharging capacitor that performs a charging / discharging operation by turning on / off both switching elements, and a diode that provides a charging path and a discharging path of the charging / discharging capacitor. When the element is turned on, the charge / discharge capacitor is charged through the diode, and when the second switching element is turned on, the charge / discharge capacitor is discharged through the diode,
This discharge current is given to the smoothing capacitor, and the two switching elements are alternately turned on to obtain a voltage twice that of the DC power supply.

Further, the present invention, a reactor connected to a DC power supply,
First and second DC voltage converters are provided between the output voltage smoothing capacitor, and the DC voltage converters are charged by turning on and off the first and second switching elements, respectively. A charging / discharging capacitor that performs a discharging operation, and a diode that provides a charging path and a discharging path for the charging / discharging capacitor are provided. When the first switching element is turned on, the charging / discharging capacitor is charged through the diode, and the second switching element is provided. Is turned on, the charging / discharging capacitor is discharged through the diode, and the discharging current is given to the smoothing capacitor. A plurality of charging / discharging capacitors in the first and second DC voltage converters are respectively connected in series. Connect the series capacitor of
The discharge current from the charging / discharging capacitor and the series capacitor in the DC voltage converter is charged in the charging / discharging capacitor and the series capacitor in the second DC voltage converter, and the charging / discharging capacitor and the series capacitor in the second DC voltage converter are connected. A diode is connected so that the discharge current from the first DC voltage converter is charged into the charge / discharge capacitor and the series capacitor, and the final stage of each series capacitor is commonly connected to the smoothing capacitor. The switching elements in the DC voltage converter are sequentially turned on / off to obtain an output voltage that is an integral multiple of the DC power supply.

Furthermore, the present invention includes a reactor connected to the output side, a capacitor for smoothing the output voltage, and a DC voltage conversion unit connected to a DC power supply, wherein the DC voltage conversion unit is
A second switching element, a charging / discharging capacitor that is charged / discharged via the both switching elements, and a diode that provides a charging / discharging path of the charging / discharging capacitor, and a state in which the both switching elements are turned on periodically. Switching, when one of the switching elements is turned on, the current from the DC power source is charged into the capacitor through the diode, and when the other switching element is turned on, the charging voltage of the capacitor is discharged through the diode, and this discharge is performed. The current is set to the reactor current.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings. FIG. 1 shows DC / DC according to the first embodiment of the present invention.
It is a circuit diagram of a converter.

L is a reactor, S1 and S2 are first and second switching elements connected in series, D1 and D2 are also first and second diodes connected in series, and C1 is a first capacitor. They are connected in series with each other and the DC power source E _S and the reactor L and the two switching elements S1, S2.
Each switching element S1, S2 and each diode D1, D
2 is connected in series with each other, and the whole is a second smoothing
It is connected in parallel with the capacitor C0. And the first
The capacitor C1 is connected in parallel with the first diode D1 and the second switching element S2.

The circuit operation of the DC / DC converter having such a configuration will be described with reference to FIGS. 2 and 3. Second
FIG. 1A is an equivalent circuit diagram of FIG. 1 when the first switching element S1 is on and the second switching element S2 is off.
In FIG. 2 (b), the first switching element S1 is off,
Second equivalent circuit diagram when the switching element S2 is on,
FIG. 2 (c) is an equivalent circuit diagram when both switching elements S1 and S2 are off, and FIG. 2 (d) is both switching element S.
It is an equivalent circuit diagram when both 1 and S2 are on. FIG. 3 is a waveform diagram for explaining the operation of the equivalent circuit of FIGS. 2 (a) and (b), and FIG. 4 is a waveform diagram for explaining the operation of the equivalent circuit of FIG. 2 (c). , Fig. 5 is Fig. 2
FIG. 7 is a waveform diagram for explaining the operation of the equivalent circuit diagram of (d).

(A) when converting DC power supply voltage E _S twice the DC voltage that: The equivalent circuit of FIG. 2 (a), first capacitor C
1 is an equivalent circuit when the cycle is charged by a current from the DC power source E _S is shown. This charging period is the third
It is shown in the period T _a figure that charging curve indicated by the dashed line. B in FIG. 3 indicates the voltage at point B in FIG. 1, that is, the charging voltage of the first capacitor C1, and P in FIG.
The voltage at point P in the figure is shown. In FIG. 2 (b), it is a cycle in which the first capacitor C1 is discharged, and this discharging period is shown as a period _Tb in FIG. In this discharging period (b), as shown in FIG. 3, the added voltage of the power supply voltage E _S and the charging voltage E _C of the first capacitor C1 becomes high as shown by the broken line, but the second capacitor C0 Is charged by this added voltage, and the charged voltage becomes the output voltage V0. Thus, in this case, the DC power supply voltage E _S is converted into the doubled DC voltage (output voltage V0). Here, in FIG. 2 (a), the first capacitor C1
Charging voltage E _C has a reverse polarity with respect to the DC power supply voltage E _S , and in FIG. 2B, the charging voltage E _C of the first capacitor C1 has a reverse polarity with respect to the output voltage V0. Therefore,
Voltage applied to the reactor L supply voltage of FIG. 3 is the difference between E _S and P point voltage. In the period T _a or T _b ,
In the first half of the period, the voltage of the reactor L is higher than the point P on the power supply side, and the reactor L gives a voltage drop to the circuit and absorbs and stores energy. In the latter half of the period, the voltage of the reactor L is higher at the point P than at the power source side, and the reactor L releases the energy accumulated earlier to the capacitor C1 side. As a result, the output voltage V ₀ is constant (2
E _S ) and does not pulsate. Even if the load current I ₀ increases,
The output voltage V ₀ is kept constant (2E _s ) because the average value of the voltage drop of the reactor L is zero only when the voltage change rate at the point P becomes steep. If the reactor L is not inserted, the difference between the power supply voltage E _S and the voltage at the point P is added to the internal resistance of the switching elements S1 and S2. The voltage at the point P never exceeds the power supply voltage E _S , and the output voltage V ₀
Drops by the amount of decrease in E _C due to discharge of the capacitor C1. When the load current I ₀ increases, the drop in the output voltage V ₀ increases, and the voltage applied to the internal resistances of the switching elements S1 and S2 increases accordingly. As a result, the voltage drop and the power loss are significantly increased. The inductance of the reactor L may be smaller than that of the conventional example shown in FIG. 21, and a small and lightweight reactor L can be used. In this case, in the conventional example, the energy stored in the reactor L is used for boosting, whereas in this embodiment, most of the voltage is boosted by the energy stored in the first capacitor C1. , First
DC power supply voltage E with respect to the charging voltage of the capacitor C1
_The reactor L absorbs a slight potential difference of _S (period T _a ) or the output voltage V0 (period T _b ).

(B) When converting to a DC voltage other than twice the DC power supply voltage E _S : (B-A) When converting to a DC voltage smaller than twice the DC power supply voltage E _S (output voltage V0): In the conversion, both the first and second switching elements S1 and S2 are turned off. Then, FIG. 1 becomes the equivalent circuit diagram of FIG. 2 (c). In the case of this equivalent circuit, in addition to the periods T _a and T _b , a period T _{c in} which both switching elements S1 and S2 are turned off so that a voltage waveform diagram as shown in FIG. 4 (a) is obtained. To provide. In FIG. 4 (b),
D2 is the second diode D2, D1 is the first diode D
Reference numerals 1 and S2 denote the first switching element S2, and S1 denotes the ON / OFF states of the first switching element S1.
Here, ON is indicated by a thick horizontal line, and OFF is indicated by a thin horizontal line. In this figure, for simplicity, it is assumed that there is no voltage ripple in the first capacitor C1. In the period T _c , the current iL of the reactor L passes through the first and second diodes D1 and D2, and the potential at the point P is almost the output voltage V0. The average value of principle the voltage across the inductor L is zero, the other periods T _c, the voltage of the point P is lower than the power supply voltage E _S, the charging voltage of the first capacitor C1 is also than E _S It becomes smaller and operates as if the power supply voltage became smaller. as a result,
The output voltage V0 of the DC / DC converter is smaller than twice the power supply voltage.

(B- B) When converted into large DC voltage than twice the DC power supply voltage _{E S} (output voltage V0): To increase the output voltage V0 is the period _T a, in addition to the two switching elements S1 of _{T b,} By turning on both S2, a period T _d for shorting the point P is provided. The equivalent circuit diagram of FIG. 1 in this case is as shown in FIG. 2 (d). And
A voltage waveform diagram by this equivalent circuit is shown in FIG. In FIG. 5 (a), contrary to FIG. 4, the output voltage V0 operates as if the power supply voltage E _S were high.
Grows. FIG. 5 (b) is a view corresponding to FIG. 4 (b). Incidentally, the operation of turning on both switching elements S1 and S2 at the same time may be performed by this switching element S3 by providing another one switching element S3 indicated by a broken line instead of both switching elements S1 and S2 in series. The same effect can be obtained. In this case, the switching element S
On / off of 3 may be performed regardless of the operation of the switching elements S1 and S1. In this way, the output voltage V0 can be changed according to the ratio of the periods T _c and T _d in which both the switching elements S1 and S2 are both off or on.

FIG. 6 is a circuit diagram of the DC / DC converter of the second embodiment. In the embodiment of FIG. 6, two sets b, c of the circuit a surrounded by the broken line of FIG. 1 are used, and the DC power supply E _S , the reactor L, and the capacitor C0 are commonly used. In the circuit surrounded by the broken line a, S11 and S12 are first and second switching elements, D11 and D12 are first and second diodes, and C1 is a first capacitor. In the circuit surrounded by the broken line b, S21 and S22 are third and fourth switching elements, D21 and D22 are third and fourth diodes, and C2 is a second capacitor. E _S is a DC power source, L is the reactor, C0 is the third capacitor.

In the DC / DC converter having such a configuration, among the switching elements, for example, the second and third switching elements S12 and S21 are turned on at the same time, or the first and fourth switching elements are turned on.
The switching elements S11 and S22 are operated so as to be turned on at the same time. FIG. 8 (a) is a voltage waveform diagram at that time, and FIG. 8 (b) is a diagram showing ON / OFF states of each switching element and each diode. This Figure 8 (b)
[Fig. 4] is a view similar to Figs. 4 and 5. FIG. 7 is an equivalent circuit diagram of FIG. 6 when the first and fourth switching elements S11 and S22 are turned on at the same time. In this equivalent circuit, the first switching element S11 is turned on so that the first switching element S11 is turned on.
The capacitor C1 is charged through the first diode D11, and the second capacitor C2 is discharged through the fourth diode D22 when the fourth switching element S22 is turned on. In FIG. T _a . In this period T _a , the power supply current is iL, and this power supply current simultaneously supplies the charging current ic1 of the first capacitor C1 and the discharging current ic2 of the capacitor C2.
The value is twice the load current 10. Then, if the period _{T b} and a switching element S12, S21 of the on-first capacitor C1 in the opposite discharge, the second capacitor C2 is charged with it. Therefore, in the switching element, S1
If the states of the groups of 1, S22 and the groups of S12, S21 are alternately turned on every half cycle of the period T _a and the period T _b , the voltage waveform becomes as shown in FIG. 8 (a). . In FIG. 8, in the period T _a , the first capacitor C1
Is equal to the discharge amount of the second capacitor C2, and the total voltage of both capacitors C1 and C2 is always the output voltage V
It becomes equal to 0, and the total is the same voltage immediately after changing from the period T _a to the period T _b . Further, since the output voltage V0 is always supplied with half the current iL, the output voltage V0
The pulsation of 0 is extremely small.

9 (a) (b) (c) (d) show in detail the switching state of the switching element when the period T _a is changed to the period T _b . That is, each switching element S11
And the switching timings of S12 and S21 and S22 are shifted. First, at time t11, the first switching element S
When 11 is turned off, of the current iL, the amount of the current flowing in the first capacitor C1 before the time t11 in the state of the equivalent circuit of FIG.
Are all ic2. Then, the second switching element S12 enters a turn-on operation and the terminal voltage thereof gradually decreases.
No current is flowing in the collector of, so no switching loss occurs. Next, at time t12, when the B1 point reaches the output voltage V0, current flows through the second diode D12, and the B1 point becomes equal to V0. At this time, since the charging voltage E _c 1 of the first capacitor C1 is higher than the charging voltage E _c 2 of the second capacitor C2, the point A1 does not reach the voltage at the point P. After time t12, the equivalent circuit of FIG. 9 (b) is obtained, and at time t12 of FIG.
As at ~ t14, the fourth diode D22 is turned off, and the current iL is all ic1. Second at time t13
The switching element S12 ends the turn-on, and the time t
The fourth switching element S22 is turned off from 14 and turn-on of the third switching element S21 is started.
The voltage at the point drops. Until time t15, the current i
c2 does not flow, and switching from the fourth switching element S22 to the third switching element S21 is performed with no current. When the voltage at the point A2 reaches almost zero at time t15, only the co-discharge of the first and second capacitors C1 and C2 was performed at times t11 to t15 before that, so E _c
1 + E _c 2 is lower than V0. As in the equivalent circuit of FIG. 9 (c) and the times t15 to t16 of FIG. 10, the second diode D12 is turned off and the second capacitor C2 is turned off.
After time t16 when only the battery is charged and E _c 2 becomes large and E _c 1 + E _c 2 reaches V0, the current iL is ic2 and i.
The first capacitor C1 is discharged and the second capacitor C2 is charged.

FIG. 11 shows the second commutation of FIG.
It is a figure showing a locus of voltage and current about switching element S12. As is apparent from FIG. 11, since the current is turned on and off under a very low device voltage,
Switching loss is extremely small. Further, similarly to that of FIG. 1, when it is necessary to change the output voltage, the first, fourth switching elements S11, S22, or the second, third switching elements S12, S21, or elements in place of them are used. It is possible to provide a period in which the point P and the point O are short-circuited or a period in which all of the respective switching elements are turned off.

FIG. 12 is a circuit diagram of the third embodiment. The embodiment shown in FIG. 12 is similar to that shown in FIG. 6 in that the fourth to seventh capacitors C1 ',
C1 ″, C2 ′, C2 ″ and fifth to eighth diodes D1
3, D23, D10, D20 are added.
When the first to fourth switching elements S11 to S22 are switched in the same manner as in FIG. 6, the capacitor C
0 except the capacitors are all substantially DC power supply voltage E _S
In this embodiment, the output voltage V0 becomes a DC voltage which is almost four times the power supply voltage E _S.

FIG. 13 shows the second and third switching elements S12 and S21.
12 is an equivalent circuit diagram of FIG. 12 when is ON, and as shown in this equivalent circuit, each diode D10, D13, D1
2, the average value of the currents i10 to i13 flowing through D21 is equal to I0. Also, the fourth capacitor C1 'and the sixth capacitor
The connection point E1 with the capacitor C1 ″ and the sixth capacitor C
6 in each of the 2 'and the connection point E2 between the seventh capacitor C2 ", the seventh diode D10, D20, by connecting the circuit similar to the third capacitor C0, the DC power supply voltage _{E S}
It is possible to obtain a DC voltage three times as high as that of the above. 12th
Although the pulsation of the output voltage V0 in the figure is slightly larger than that in FIG. 6, the voltage applied to the reactor L becomes small and the switching loss of the first to fourth switching elements S11 to S22 is very small. It is similar to that of the figure.

FIG. 14 is a circuit diagram of the fourth embodiment, which is the same as that of FIG. 6 except that the switching element and the diode are replaced in the circuit diagram of FIG. In the case of this embodiment, when the first and fourth switching elements S11 and S22 or the second and third switching elements S12 and S21 are alternately turned on, the voltage waveform thereof becomes the first
It becomes Fig. 6 (a). Incidentally, FIG. 16 (b) shows each switching element S11, S12, S21, S2 similarly to FIG. 4 (b) and the like.
2 and the diodes D11, D12, D21 and D22 are shown in the on / off state. In the period T _a , as is clear from FIG. 16, the first and fourth switching elements S1
1, S22 and the first and fourth diodes D1 and D22 are turned on, and the first and third switching elements S12 and S21 and the first and third diodes DD12 and D21 are turned off. In such a state, the circuit of FIG.
It looks like the equivalent circuit in the figure. For the period T _a, as shown in this equivalent circuit, the first capacitor C1 discharge current ic
The sum of 1 and the charging current ic2 of the second capacitor C2 is the current iL of the reactor L. The direction of this current iL is opposite to that of FIG. 6, the positions of the power source and the load are reversed, and the first and second capacitors C1 and C2 are charged to approximately 1/2 of the DC power source voltage E _S. since the output voltage V0 is almost halved the DC source voltage E _S, and since the average value of the current iL is the load current, the power supply current is 1/2 of the load current. In this equivalent circuit, the first capacitor C1
Is discharged and the second capacitor C2 is charged, so that the voltage at the point P decreases with time and has a slope opposite to that in FIG. 8 (FIG. 16). In the case of this embodiment, the pulsation of the power supply and the output current is small, and each switching element S1
The switching loss can be remarkably reduced by shifting the commutation timings of S1, S22, S12 and S21, and the switching elements S11 and S22 or S12 and S21.
Short circuit mode or switching elements S11 to S22
The output voltage can be made variable by all the open modes described above, and the same features as those in FIG. 6 are provided.

FIG. 17 shows a fifth embodiment in which the DC / DC converter is constituted by only one of the circuits d and e surrounded by the broken line in FIG. 15th except loss is not small
It has the same characteristics as the circuit of FIG. 6 or FIG. The relationship between FIG. 17 and FIG. 14 is similar to the relationship of FIG. 1 with respect to FIG.

FIG. 18 shows a sixth embodiment capable of transmitting electric power from the low voltage DC V1 side to the high voltage DC V2 side and in the opposite direction. The circuit of FIG. 18 is shown in FIG.
The circuit shown in Fig. 4 is superposed. The period in which the switching elements S11, S13, S22, S24 are turned on, and the switching elements S12, S14, S21,
The period for which S23 is turned on is alternately operated. The first and second capacitors C1 and C2 are almost charged to the voltage V1, and the voltage V2 becomes twice the voltage V1.

When V2 / V1 is smaller than 2, the circuit of the sixth embodiment is
In the superposition, the element connected to the position of the portion corresponding to FIG. 6 operates, and the equivalent circuit of the circuit of FIG. 18 in that case is the same as the circuit of FIG. 7, and the voltage waveform is It is similar to FIG. Electric power is transmitted from the voltage V1 side to the voltage V2 side.

When V2 / V1 is larger than 2, in the circuit of the sixth embodiment shown in FIG. 18, the elements of the portion corresponding to FIG. 14 operate in the superposition, and the equivalent of FIG. 18 in that case. The circuit is the same as in FIG. 15, and the voltage waveform is
It becomes similar to FIG. Electric power is transmitted from the voltage V2 side to the voltage V1 side. This is as if the winding ratio in alternating current is 1:
It is considered to be an operation like a transformer of No.2. 18th
The figure also has the features and characteristics shown in FIGS. 6 and 14, and a circuit configuration having only the first capacitor C1 as shown in FIG. 19 can be used.

FIG. 20 is a circuit configuration diagram of the seventh embodiment, which obtains a negative output voltage V0 with respect to the DC power supply voltage E _S.
In this case, the circuit surrounded by the chain line will be described later.

First capacitor C1 when the second switching element S12 is turned on, is charged by a circuit code in _{E S → S12 → C1 → D12} → L, the first switching element S11 is in the code when on C1 → S11 → The circuit of L → C0 → D11 is discharged, and the discharge current charges the third capacitor C0. The first capacitor C1 and the third capacitor C0 are charged to about E _S , and the load current is supplied from the terminal of the third capacitor C0 as a negative DC power source. Its operation and characteristics are similar to those of the circuit of FIG. 1, but the power supply current and the load current have the same magnitude. Each terminal x1, x of this circuit
2, x3, terminals x1 ', x2', x3 'of the circuit surrounded by a chain line including the second capacitor C2 are connected in correspondence with the arrows, respectively, and the first capacitor C2 is connected.
When operated in the opposite phase to the circuit of No. 1, the power supply current and the charging current of the third capacitor C0 are both continuous. Further, the commutation loss of the switching element can be significantly reduced.

When the DC conversion is performed by using the charge / discharge of the capacitor in this way, the size of the series reactor can be significantly reduced. Further, when the two circuits are operated in two phases, both the power supply current and the output current become continuous currents, and if the commutation timing of the two circuits is slightly shifted, the switching loss of the switching element can be significantly reduced. Basically, it is possible to obtain the output of double boosting, 1/2 dropping, and -1 negative voltage, and the output voltage can be continuously changed by placing the short-circuit mode and the open mode. Depending on the circuit configuration, it is also possible to freely transfer power from the low voltage side to the high voltage side or vice versa. With the multi-stage configuration, it is possible to obtain a voltage that is an arbitrary integral multiple of the power supply voltage.
Further, since the diode in the circuit has a slightly large voltage drop, it is possible to further improve the efficiency by short-circuiting the elements having a small voltage drop across the diode when energized.

(Effects of the Invention) As described above, according to the present invention, the charging / discharging of the capacitor is switched by the switching element, and the discharging current is supplied to the output so that a DC voltage higher than the power supply voltage is obtained and the charging / discharging is performed. The current is always carried out through the choke coil inserted in series with the power supply, and the charge and discharge of the capacitor is 2
By operating in phase, it is possible to reduce the size and weight of the choke coil, and it is possible to obtain an integral multiple DC voltage with less switching element loss and less output voltage pulsation.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention, and FIGS. 2 (a) (b).
(c) and (d) are equivalent circuit diagrams of FIG. 1 depending on the ON / OFF state of the switching element of FIG. 1, and FIGS. 3 to 5 are waveform diagrams for explaining the operation of the circuit of FIG. FIG. 7 is a circuit diagram of the second embodiment, FIG. 7 is an equivalent circuit diagram of FIG. 6, and FIG.
FIG. 9 is a waveform diagram for explaining the operation of the equivalent circuit shown in FIG.
Detailed equivalent circuit diagram of FIG. 10, FIG. 10 is a waveform diagram for explaining the operation of the equivalent circuit of FIG. 9, FIG. 11 is a voltage / current waveform diagram for explaining the operation of FIG. 9, and FIG. Circuit diagram of the embodiment, FIG. 13 is an equivalent circuit diagram of FIG. 12, FIG. 14 is a circuit diagram of the fourth embodiment, and FIG. 15 is an equivalent circuit diagram of FIG.
16 is a waveform diagram for explaining the operation of the equivalent circuit of FIG. 15, FIG. 17 is a circuit diagram of the fifth embodiment, FIG. 18 is a circuit diagram of the sixth embodiment, and FIG. 19 is a circuit diagram of FIG. Modified circuit diagram, second
FIG. 0 is a circuit diagram of the seventh embodiment, FIG. 21 is a circuit diagram of a conventional example, FIG. 22 is a waveform diagram used to explain the operation of the circuit of FIG. 21, and FIG. 23 is an operation diagram of the circuit of FIG. FIG. 3 is a voltage / current waveform diagram used for the above. In the figure, reference numeral S11, S12, S21, S22 are switching elements, D11, D12, D21, D22 is a diode, _{E S} is a DC power source, L is the reactor, C1, C2, C
0 is a capacitor.

Claims (7)

[Claims] 1. A DC voltage converter is provided between a reactor connected to a DC power source and a capacitor for smoothing an output voltage, the DC voltage converter comprising first and second switching elements and both of the switching elements. A charging / discharging capacitor that performs charging / discharging operation by turning on / off the element, and a diode that provides a charging path and a discharging path of the charging / discharging capacitor,
When the first switching element is turned on, the charging / discharging capacitor is charged through the diode, and when the second switching element is turned on, the charging / discharging capacitor is discharged through the diode, and this discharging current is given to the smoothing capacitor. The DC / DC converter is characterized in that both of the switching elements are alternately turned on to obtain a voltage twice that of the DC power supply. 2. DC / according to claim 1
In the DC converter, two sets of the DC voltage converter are provided, and a state in which the first switching element of the first DC voltage converter and the second switching element of the second DC voltage converter are simultaneously turned on, A DC / DC converter in which the second switching element of the voltage conversion section and the first switching element of the second DC voltage conversion section are alternately turned on at the same time. 3. The DC / DC converter according to claim 1 or 2, wherein the first and second switching elements in the both DC voltage converters are turned on at the same time or turned off at the same time. Or a mode in which a DC power supply is short-circuited via a reactor by a third switching element is provided, the time ratio of the mode to the switching cycle of the switching element is controlled, and the output voltage is varied by this time ratio. DC converter. 4. DC / according to claim 2
In the DC converter, a DC that gives a drive signal to the switching element so that the commutation timing of the switching element in the first DC voltage conversion section and the commutation timing of the switching element in the second DC voltage conversion section are deviated by a predetermined time. / DC converter. 5. A first and a second DC voltage converter are provided between a reactor connected to a DC power source and a capacitor for smoothing an output voltage, and each DC voltage converter has a first and a second DC voltage converter, respectively.
A second switching element, a charging / discharging capacitor that performs a charging / discharging operation by turning on / off both of the switching elements, and a diode that provides a charging path and a discharging path of the charging / discharging capacitor are provided. A charging / discharging capacitor is charged via the diode, the charging / discharging capacitor is discharged via the diode when the second switching element is turned on, and this discharging current is given to the smoothing capacitor. A plurality of series capacitors are connected in series to each charging / discharging capacitor in the second DC voltage converter, and the discharge current from the charging / discharging capacitor and series capacitor in the first DC voltage converter is charged in the second DC voltage converter. The discharge capacitor and series capacitor are charged, and the charging / discharging capacitor in the second DC voltage converter is also charged. A diode is connected so that the discharge current from the capacitor and the series capacitor is charged in the charging / discharging capacitor and the series capacitor in the first DC voltage converter, and the final stage of each series capacitor is common to the smoothing capacitor. A DC / DC converter which is connected to the DC voltage converter and sequentially turns on / off the switching elements in each DC voltage converter to obtain an output voltage that is an integral multiple of the DC power supply. 6. A reactor connected to an output side, a capacitor for smoothing an output voltage, and a DC voltage converter connected to a DC power supply, wherein the DC voltage converter includes first and second converters.
A switching element, a charging / discharging capacitor charged / discharged through both the switching elements, and a diode that provides a charging / discharging path of the charging / discharging capacitor, the switching elements are periodically switched on.
When one of the switching elements is turned on, the current from the DC power source is charged into the capacitor through the diode, and when the other switching element is turned on, the charging voltage of the capacitor is discharged through the diode,
A DC / DC converter characterized in that the discharge current is the reactor current. 7. DC / according to claim 6
In the DC converter, two sets of the DC voltage converters are provided, and the charging / discharging operation of the charging / discharging capacitors in both the DC voltage converters is periodically switched by turning on / off a switching element to charge / discharge the first DC voltage converter. A DC / DC converter in which a discharge current from a discharge capacitor and a charge current from a charge / discharge capacitor in the first DC voltage converter flow in the same direction in the reactor, and the sum of the two currents is supplied as a load current.