JPH05111243A - Dc/dc converter - Google Patents

Abstract

PURPOSE:To provide a DC/DC converter having no transformer and a plurality of outputs. CONSTITUTION:The DC/DC converter comprises a first reactor L1 connected in series with a DC power source E, a capacitor C0 and a second reactor L2. The converter also comprises a pair of switches S1A and S1B to be so operated that one end of a first output capacitor COUT1 is alternately connected to connecting points 10 and 12. One end of a second output capacitor C0UT2 is connected to one end of the capacitor COUT1, and the other end is connected to the point 10 through a switch S2. The switch S2 is operated ON, OFF in coincidence with ON, OFF of the switch S1B. One end of a third output capacitor COUT is connected to the other end of the capacitor COUT1, and the other end is connected to the point 12 through a switch S3. The switch S3 is operated ON, OFF in coincidence with ON, OFF of the switch S1A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC-DC converter having a plurality of outputs without using a transformer.

[0002]

2. Description of the Related Art Conventionally, a transformer has been used to obtain a plurality of outputs in a DC-DC converter. FIG. 20 shows an example of a conventional multiple output DC-DC converter using a transformer. In the conventional method as shown in FIG. 20, an output obtained by converting DC into AC is input to the primary side of the transformer T, a plurality of taps are provided on the secondary side of the transformer T, and different output voltages are taken out from the respective taps. Is configured as follows. As a control method, generally, PW
M control is used, and adjusting any V _OUT will also adjust the other V _OUT . The error amplifier which _receives V _OUT1 in FIG. 20, the pulse width control circuit and the switch S are a PWM control system.

Therefore, the conventional DC-D having a plurality of outputs
Since the C converter uses a transformer, it is difficult to miniaturize and integrate it, and there is a problem that the conversion efficiency is reduced due to loss due to the leakage inductance of the transformer.

On the other hand, as a type that does not use a transformer, for example, a switched capacitor type D for converting a DC input voltage into a required DC output voltage by connecting and disconnecting a switch is used.
Recently, C-DC converters have been studied and various ones have been developed. 21 and 22 show Japanese Patent Application No. 02-167800 and Japanese Patent Application No. 02-1678 related to the applicant's prior application.
No. 01 step-down type and step-up type DC-D
An example of a C converter is shown.

The step-down DC-DC converter shown in FIG. 21 operates as follows. That is, in FIG. 21, the switches S _1A and S _1B are connected to the connection point of the first reactor L ₁ and the capacitor C ₀ at one end of the output capacitor C _OUT and the connection of the capacitor C ₀ and the second reactor L ₂ . Alternately connect points and. When the switch S _1A is turned on and at the same time the switch S _{1 B} is turned off, the DC power source E supplies energy to the first reactor L ₁ and the output capacitor C _OUT , and the first reactor L ₁ stores energy, Output capacitor C
_OUT is charged. On the other hand, the capacitor C ₀ is connected to the switch S
Energy is supplied to the output capacitor C _OUT and the second reactor L ₂ via _1A , the output capacitor C _OUT is charged, and the second reactor L ₂ stores energy. Next, switch S _1A is turned off, and at the same time, switch S _1A is turned off.
_{When 1B} is switched on, the first reactor L ₁ is connected in series with the DC power source E and releases energy. The released energy and the energy of the DC power source E charge the capacitor C ₀ and the output capacitor C _OUT . On the other hand, the second reactor L ₂ releases energy via the switch S _1B to charge the output capacitor C _OUT . By the above-described operation, is converted to the ratio d (where d = the sum of the ON period and the OFF time of the ON period / switch S _1A of the switch S _1A) only a DC voltage obtained by stepping down when the voltage of the DC power source E It

The operation of the step-up DC-DC converter shown in FIG. 22 is as follows. That is, in FIG. 22, when the switch S _1A is turned on and the switch S _1B is turned off at the same time, the second reactor L ₂ stores the energy of the DC power source E. On the other hand, the capacitor C ₀ is connected to the switch S
_It is connected in series with the DC power supply E via _1A and discharged. The energy of the DC power source E and the discharged energy are supplied to the first reactor L ₁ and the output capacitor C _OUT , and the output capacitor C _OUT is charged. Next, when the switch S _1A is turned off and the switch S _1B is turned on at the same time, the second reactor L ₂ releases energy via the DC power source E. This released energy charges the capacitor C ₀ together with the energy of the DC power source E. On the other hand, the first reactor L ₁ is connected in series with the DC power source E and emits energy. This released energy is output along with the energy of the DC power source E to the output capacitor C.
Charge _OUT . By the operation as described above, the DC power source E
1 / (1-d) (wherein d is the ON period and the sum of the off-time of the ON period / switch S _1A of d = switches S _1A represents a time ratio) with respect to the voltage is converted into only boosted DC voltage It

However, all of these DC-DC converters that do not use a transformer have a single output and cannot satisfy the requirement of requiring a plurality of outputs.

[0008]

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a compact and highly efficient DC-DC converter having a plurality of outputs without using a transformer.

[0009]

In order to achieve the above object, a DC-DC converter of the present invention comprises a first reactor, a capacitor, a second reactor, a DC power supply, and the first reactor. A means for connecting the capacitor and the second reactor in series, a first output capacitor having one end connected to a connection point between the DC power supply and the second reactor, The other end of the first output capacitor alternates between a first connection point between the first reactor and the capacitor and a second connection point between the capacitor and the second reactor. A first switching means for connecting to the second output capacitor, the second output capacitor having one end connected to the other end of the first output capacitor, and the other second output capacitor. Edge and said first A second switching means for connecting / disconnecting to / from the connection point in synchronization with the first switching means, or a third output having one end connected to the one end of the first output capacitor Or a third switching means for connecting and disconnecting between the other end of the third output capacitor and the second connection point in synchronization with the first switching means, or It is characterized by having all the configurations of.

Another DC-DC converter of the present invention is the first reactor, the capacitor, the second reactor, the first output capacitor, the first output capacitor, and the first output capacitor. Means for connecting the first reactor, the capacitor, and the second reactor in series, and means for connecting the connection point between the second reactor and the first output capacitor to one end of a DC power supply The other end of the DC power supply, a first connection point between the first reactor and the capacitor, the capacitor and the second
A second switching point for alternately connecting to a second connection point between the first output capacitor and the first reactor, and a second switching point for alternately connecting to the second connection point between the first output capacitor and the first reactor. A second output capacitor having one end connected thereto, another end of the second output capacitor and the first connection point are connected and disconnected in synchronization with the first switching means. A third output capacitor having switching means, or one end of which is connected to a connection point between the first output capacitor and the second reactor;
A third switching means for connecting and disconnecting the other end of the third output capacitor and the second connection point in synchronization with the first switching means is provided, or all of the above configurations are provided. It is characterized by being provided.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows a circuit configuration of a step-down DC-DC converter having three outputs which is an embodiment of the present invention.
In FIG. 1, the circuit configuration surrounded by a broken line is the same configuration as the single output step-down DC-DC converter shown in FIG. 21, and the elements with the same reference numerals have the same functions. The first reactor L ₁ , the capacitor C ₀ , and the second reactor L ₂ are connected in series to the DC power source E. The switch S _1A is connected between the connection point 10 of the first reactor L ₁ and the capacitor C ₀ and one end of the first output capacitor C _OUT1 . The switch S _1B is connected between the connection point 12 of the capacitor C ₀ and the second reactor L ₂ and the one end of the capacitor C ₀ . The other end of the first output capacitor C _OUT1 is connected to a common return line 14 connected to a connection point between a DC power supply prepared separately from the DC-DC converter of the present invention and the second reactor L _2. , Both ends of the first output capacitor C _OUT1 are DC−
It constitutes the first output of the DC converter. One end of the second output capacitor C _OUT2 has a first output capacitor C
_OUT1 is connected to the one end, and the other end is connected to the connection point 10 via the switch S ₂ . The other end of the second output capacitor C _OUT2 constitutes the second output of the DC-DC converter together with the common return line 14. Third
One end of the output capacitor C _OUT3 is connected to the other end of the first output capacitor C _OUT1 , that is, the common return line 14, and the other end is connected to the connection point 12 via the switch S ₃ . Both ends of the third output capacitor C _OUT3 form a third output of the DC-DC converter. Second output capacitor C _OUT2 and third output capacitor C
_OUT3 functions as an output smoothing capacitor. Each switch is preferably a switching transistor, but may be a mechanical switch.

FIG. 2 shows a time chart of the operation of each switch. As shown in FIG. 2, the switch S _1A is turned on,
The switch S _1B is turned off, and the switch S _1B is turned on and off complementarily to the switch S _1A . Also, as shown in FIG. 2, the switch S ₂ performs the same on / off operation as the switch S _1B with respect to time, and the switch S ₃ has the same on / off operation as the switch S _1A with respect to time. To be controlled.

Assuming that each circuit element is ideal, the equivalent circuit of the DC-DC converter shown in FIG.
When the switch S _1A is turned on, the switch S _1B is turned off, the switch S ₂ is turned off, and the switch S ₃ is turned on.
As shown in FIG. 3A, when the switch S _1A is turned off, the switch S _1B is turned on, the switch S ₂ is turned on, and the switch S ₃ is turned off. ..

Next, the principle of operation of the DC-DC converter thus constructed will be described with reference to the equivalent circuit shown in FIG.

Now, in the state shown in FIG. 3A when the switch S _1A is on, the directions of the voltages and currents of the respective parts are as shown in FIG. 3A, the first reactor L
₁ and 2 respectively flowing in the reactor L ₂ of energy U _ON1 and U _ON2 respectively expressed as follows.

U _ON1 = I _L1 · (V _IN −V _OUT1 ) · T _ON (1) U _ON2 = I _L2 · (V _C −V _OUT1 ) · T _ON (2) where V _IN is the input voltage. , V _OUT1 is the first output voltage, V _C is the voltage across capacitor C ₀ , I _L1 and I _L1
Is the current flowing through the first reactor L ₁ and the second reactor L ₂ , respectively, and T _ON is the on-time of the switch S _1A .

Further, in the state shown in FIG. 3B when the switch S _1A is off, that is, when the switch S _1B is on, the directions of the voltages and currents of the respective parts are as shown in FIG. 3B. Then, the respective energies U _OFF1 and U _OFF2 emitted from the first reactor L ₁ and the second reactor L ₂ to the load (not shown) are as follows.

U _OFF1 = I _L1 · (V _C + V _OUT1 −V _IN ) · T _OFF (3) U _OFF2 = I _L2 · V _OUT1 · T _OFF (4) where T _OFF is the off time of the switch S _1A And other symbols have the same meanings as in formulas (1) and (2).

[0020] Here, in the ideal steady state, each of the energy U _ON1 and U _ON2 switch S _1A is turned on to flow into the first reactor L ₁ and second reactor L _2, the switch S _1B is since equal on to the first reactor L ₁ and second reactor L ₂ each energy U _OFF1 and U _OFF2 released _{from, U ON1 = U OFF1 (5} ) relationship U _ON2 = U _OFF2 (6) Holds.

From the equations (1) to (6), when the voltage V _C of the capacitor C ₀ is erased, the ratio V _OUT1 / V _IN of the input voltage to the first output voltage is V _OUT1 / V _IN = T _ON / ( T _ON + T _OFF ) = T _ON / T _S = d (7) Here, T _S represents the sum of the ON time and the OFF time of the switch S _1A , that is, the repetition time, and d represents the duty ratio.

From the equation (7), the first output capacitor C
The first output voltage _OUT1 across the V _OUT1 when it can be seen that is stepped down from the input voltage V _IN in accordance with the ratio d.

Further, from the equations (1) to (6), when V _OUT1 is erased, the relationship between the voltage V _C of the capacitor C ₀ and the input voltage V _IN is shown by the following equation.

V _C = V _IN (8) On the other hand, as shown in FIG. 3B, between one end of the second output capacitor C _OUT2 connected to the connection point 10 and the common return line 14. the second output voltage V _{OU T2} of, V
_The following relationship is established between _OUT1 and V _C.

[0025] _{V OUT2 = V OUT1 + V C} (9) In addition, as shown in (A) of FIG. 3, the third output voltage V _OUT3 across the third output capacitor C _OUT3 is, V
_The following relationship is established between _OUT1 and V _C.

[0026] _{V OUT3 = V OUT1 -V C (} 10) (9) (10), using the relationship of equation (7) (8), a second output voltage V _{OU T2,} and the third output voltage V _OUT3 can be expressed by the following equations with respect to the input voltage.

V _OUT2 = (d + 1) · V _IN (11) V _OUT3 = (d−1) · V _IN (12) FIG. 4 schematically shows changes in each output voltage when the time ratio d is changed.
Shown in. From FIG. 4, in the DC-DC converter shown in FIG. 1, the first and third output voltages are step-down with respect to the input voltage, and the third output voltage has the opposite polarity to the input voltage. 3-output DC-DC in which the output voltage of 2 is step-up
You can see that it works as a converter.

FIG. 5 shows a modification of the step-down DC-DC converter having the three outputs shown in FIG. That is, the switches S _1B , S ₂ and S ₃ in FIG. 1 are replaced with diodes D ₁ , D ₂ and D ₃ , respectively. For each diode, the anode of the diode D ₁ is at the connection point 12
, The anode of the diode D ₂ is connected to the connection point 10, and the cathode of the diode D ₃ is connected to the connection point 12.

From the above description with reference to the equivalent circuits shown in FIGS. 3A and 3B, when the switch S _1A is on, the diode D ₁ is reverse biased with V _C and turned off, The diode D ₂ is turned off by _applying a reverse bias of V _OUT2 −V _OUT1 . As for the diode D _3, given the polarity of the voltage generated in the second ends of the reactor L _2, the cathode side of the diode D ₃ is a negative, the diode D ₃ is turned on, a third output capacitor C _{OUT3 Are} charged and an output voltage V _OUT3 is generated.

On the other hand, in the switch S _1A is off, the diode D _1, given a voltage generated in the second ends of the reactor L _2, the anode side of the diode D ₁ becomes positive, the diode D ₁ turn on. The terminal voltage of the reactor for the generation, the cathode side of the diode D ₃ is positive, the diode D ₃ is turned off. As for the diode D _2, given the polarity of the voltage induced in the first ends of the reactor L _1, becomes the anode side of the diode D ₂ is positive, the second output capacitor C _OUT2 to the diode D ₂ is turned on Charge, C
V _OUT2 -V _{OU T1} is generated in the _OUT2 both ends.

6 to 9 show various modified embodiments based on FIG.

The embodiment shown in FIG. 6 is different from the embodiment shown in FIG. 1 in that the switch S ₃ and the third output capacitor C shown in FIG.
_It is different from _OUT3 except that it operates as a 2-output step-down DC-DC converter.

FIG. 7 shows the switches S _1B and S ₂ shown in FIG.
An example is shown in which the elements are replaced with diodes D ₁ and D ₂ , respectively.

The embodiment shown in FIG. 8 is different in that the switch S ₂ and the second output capacitor C _OUT2 in the embodiment of FIG. 1 are omitted, and operates as a two-output step-down DC-DC converter.

FIG. 9 shows the switches S _1B and S ₃ shown in FIG.
An example is shown in which the elements are replaced by diodes D ₁ and D ₃ , respectively.

FIG. 10 shows a circuit configuration of a step-up DC-DC converter having three outputs which is an embodiment of the present invention. In FIG. 10, the circuit configuration surrounded by the broken line is shown in FIG.
It has the same configuration as the single output step-up DC-DC converter shown in FIG. 2, and the elements with the same reference numerals have the same functions. The first reactor L ₁ , the capacitor C _0, and the second reactor L ₂ are connected in series to the first output capacitor C _OUT1 . One end of a DC power supply E prepared separately from the DC-DC converter of the present invention is connected to the first reactor L ₁
And the connecting point 20 of the capacitors C _0, the capacitor C ₀ and the second
Switch S _1B between the one end of the DC power supply E and the connection point 20, and the switch S _1A between the one end of the DC power supply E and the connection point 22 in order to alternately connect to the connection point 22 of the reactor L _2. Is provided. The other end of the DC power supply E,
The second reactor L ₂ and the first output capacitor C _OUT1
Is connected to the common return line 24. Both ends of the first output capacitor C _OUT1 form a first output. The second output capacitor C _OUT2 has one end connected to the connection point between the first output capacitor C _OUT1 and the first reactor L ₁ , and the other end connected to the connection point 20 via the switch S _2. It is connected. The other end of the second output capacitor C _OUT2 forms a second output with the common return line 24. Third output capacitor C
_OUT3 has one end connected to the common return line 24 and the other end connected to the connection point 22 via the switch S ₃ . The other end of the third output capacitor C _OUT3 is
A third output is formed between the common return lines 24.
The second output capacitor C _OUT2 and the third output capacitor C _OUT3 function as output smoothing capacitors. Each switch is preferably a switching transistor, but may be a mechanical switch.

FIG. 11 shows a time chart of the operation of each switch. As shown in FIG. 11, the switch S _1A is on / off controlled, and the switch S _1B is on / off controlled complementarily to the switch S _1A . Further, as shown in FIG. 11, the switch S ₂ performs the same on / off operation as the switch S _1A with respect to time, and the switch S ₃ has the same on / off operation with respect to the time as the switch S _1B. To be controlled.

Assuming that each circuit element is ideal, the equivalent circuit of the DC-DC converter shown in FIG. 10 has the switch S _1B turned off and the switch S ₂ turned off when the switch S _1A is turned on. Since the switch S ₃ is turned on and the switch S ₃ is turned off, when the switch S _1A is turned off as shown in FIG. 12A, the switch S _1B is turned on, the switch S ₂ is turned off, and the switch S ₃ is turned on. Therefore, (B) of FIG.
As shown in.

Next, the principle of operation of the DC-DC converter thus constructed will be described with reference to the equivalent circuit shown in FIG.

FIG. 12 when the switch S _1A is on.
In the state shown in (A) of Fig. 12, when the directions of the voltages and currents of the respective parts are taken as shown in (A) of Fig. 12, respective energies U _ON1 flowing into the first reactor L ₁ and the second reactor L ₂ are _taken. And U _ON2 are respectively as follows.

[0041] _{U ON1 = I L1 · (V} IN + V C -V OUT1) · T ON (13) U ON2 = I L2 · V IN · T ON (14) , where the V _IN is the input voltage, V _OUT1 Is the first output voltage, V _C is the voltage across capacitor C ₀ , I _L1 and I _L2
Is the current flowing through the first reactor L ₁ and the second reactor L ₂ , respectively, and T _ON is the on-time of the switch S _1A .

In the state shown in FIG. 12B when the switch S _1A is off, that is, when the switch S _1B is on, the directions of the voltages and currents of the respective parts are as shown in FIG. 12B. Then, the respective energies U _OFF1 and U _OFF2 emitted from the first reactor L ₁ and the second reactor L ₂ to the load (not shown) are as follows.

U _OFF1 = I _L1 · (V _OUT1 −V _IN ) · T _OFF (15) U _OFF2 = I _L2 · (V _C −V _IN ) · T _OFF (16) where T _OFF is the switch S _1A Off time, and other symbols are the same as in equations (13) and (14).

Here, in an ideal steady state, the energies U _ON1 and U _{O N2} flowing into the first reactor L ₁ and the second reactor L ₂ when the switch S _1A is turned on are _{equal to those} of the switch S _1B. since but equal to respective energy U _OFF1 and U _OFF2 which is turned on to discharge from the first reactor L ₁ and second reactor _{L 2, U ON1 = U OFF1} (17) U ON2 = U OFF2 (18) The relationship holds.

From the equations (13) to (18), the capacitor C
_When the voltage V _C of ₀ is erased, the ratio of the first input voltage to the output voltage V _OUT1 / V _IN is V _OUT1 / V _IN = (T _ON + T _OFF ) / T _OFF = T _S / T _OFF = 1 / ( 1-d) (19) Here, T _S represents the sum of the ON time and the OFF time of the switch S _1A , that is, the repetition time, and d represents the duty ratio.

The equation (19), the output voltage V _OUT1 across the first output capacitor C _OUT1, depending on the ratio d when being boosted from the input voltage V _IN.

Further, from the equations (13) to (19), when V _IN is erased, the following equation holds between the voltage V _C of the capacitor C ₀ and V _OUT1 .

V _C = V _OUT1 (20) On the other hand, as shown in FIG. 12A, it is common to one end of the second output capacitor C _OUT2 which is not connected to the first output capacitor C _OUT1. The second output voltage V _OUT2 between the return line 24 and V _IN and V _C has the following relationship.

[0049] _{V OUT2 = V IN + V C} (21) Further, as shown in (B) of FIG. 12, a third output voltage V _OUT3 across the third output capacitor C _OUT3 is
The following equation holds between V _IN and V _C.

V _OUT3 = V _C −V _IN (22) If the relations of the equations (19) and (20) are used in the equations (21) and (22), the second output voltage and the third output voltage become the input voltage. Can be expressed as follows.

V _OUT2 = (1 + 1 / (1-d)) · V _IN (23) V _OUT3 = (d / (1-d)) · V _IN (24) Each output voltage when the time ratio d is changed Figure 1 shows the outline of changes in
3 shows. From FIG. 13, in the DC-DC converter shown in FIG. 10, the first and second output voltages are boosted with respect to the input voltage, and the third output voltage is stepped down with respect to the input voltage according to the duty ratio d. DC-DC with 3 outputs varying from voltage to boost
You can see that it works as a converter.

FIG. 14 shows a modification of the step-down DC-DC converter having the three outputs shown in FIG. That is, the switches S _1B , S ₂ and S ₃ in FIG. 10 are replaced with diodes D ₁ , D ₂ and D ₃ , respectively. In each diode, the cathode of the diode D ₁ is connected to the connection point 20, the anode of the diode D ₂ is connected to the connection point 20, and the cathode of the diode D ₃ is connected to the connection point 2.
Connected to 2.

From the above description with reference to the equivalent circuits shown in FIGS. 12A and 12B, when the switch S _1A is on, the diode D ₁ is reverse biased with V _C and turned off, for the diode D _2, given the polarity of the voltage induced in the first ends of the reactor L _1, becomes the anode side of the diode D ₂ is positive, the diode D ₂ is turned on, charging a second output capacitor C _OUT2 and, a voltage of V _{OUT 2} -V _OUT1 is generated at both ends of the C _OUT2, with respect to the diode D _3, given the polarity of the voltage generated in the second ends of the reactor L _2, the cathode side of the diode D ₃ is positive Then, the diode D ₃ is turned on.

On the other hand, in the switch S _1A is off, the diode D _1, considering the polarity of the voltage induced in the first ends of the reactor L _1, the cathode side of the D ₁ becomes negative, the diode D ₁ off, the diode D _2, considering the terminal voltage of the reactor for the generation, the anode side of the diode D ₂ becomes negative, the diode D ₂ is turned off, occurs in the diode D ₃ in the second ends of the reactor L ₂ Considering the polarity of the voltage, the cathode side of the diode D ₃ is a negative, the diode D ₃ is turned on, a third output capacitor C _OUT3 charged, the voltage of V _OUT3 is generated across the C _OUT3.

15 to 18 show various modified examples based on FIG.

The embodiment shown in FIG. 15 corresponds to the switch S ₃ and the third output capacitor C _OUT3 in the embodiment shown in FIG.
The difference is that the two-step boost DC-DC converter operates.

FIG. 16 shows an embodiment in which the switches S _1B and S ₂ shown in FIG. 15 are replaced by diodes D ₁ and D ₂ , respectively.

The embodiment shown in FIG. 17 is different from the embodiment shown in FIG. 10 in that the switch S ₂ and the second output capacitor C _OUT2 shown in FIG.
Operates as a converter.

FIG. 18 shows an embodiment in which the switches S _1B and S ₃ shown in FIG. 17 are replaced by diodes D ₁ and D ₃ , respectively.

FIG. 19 is a schematic configuration diagram of a three-output step-down DC-DC converter which is a more specific embodiment of the present invention shown in FIG. 5 and has a function capable of controlling an output voltage. The configuration shown in FIG. 19 is the same as that shown in FIG. 5 except for the following points, and description of the same configuration will not be repeated. In FIG. 19, the element corresponding to the switch S _1A in FIG. 5 is composed of the switching transistor STR. The voltage dividing resistors r ₁ and r ₂ are connected in series between one end of the first output capacitor C _OUT1 connected to the switching transistor STR and the ground. The first output voltage V _OUT1 across the first output capacitor C _OUT1 is _{divided by} the voltage _dividing resistors r ₁ and r ₂ ,
It is input to the comparator CP, compared with the reference voltage V _R in the comparator CP, and the error signal thereof is given to the pulse width control circuit via the error amplifier EA. The pulse width control circuit outputs a pulse having a pulse width corresponding to the duty ratio related to the output signal of the error amplifier to the switching transistor ST.
It is given to the R gate. Further, between the diode D ₂ and the second output capacitor C _OUT2 , and between the diode D3 and the third output capacitor C _OUT2 .
3 terminal regulators are respectively inserted between the output capacitors C _OUT3 , and one end of each 3 terminal regulator is connected to the common return line 24. R _L1 , R _L2, and R _L3 represent loads during use, and are respectively the first and the first.
Second and third output capacitors C _OUT1 , C _OUT2 and C
Connected to each end of _OUT3 .

With the configuration as described above, the output voltage V _OUT1 is controlled to a desired voltage according to the reference voltage by a normal switching regulator control method. The second and third output voltages are controlled to the voltage associated with V _OUT1 and further controlled by the three terminal regulator.

According to the embodiment of the present invention (FIG. 19), the conversion efficiency was improved by 5% or more as compared with the conventional example (FIG. 20), and the volume was decreased by 1.2 cc or more.

[0063]

Since the present invention is constructed as described above in detail, it has the following effects.

The first and second reactors, capacitors,
In a single output DC-DC converter having a switching means and an output capacitor, the second switching means and the second output capacitor, or the third switching means and the third output capacitor, or both of them are provided. Thus, it is possible to have a plurality of outputs such as two outputs or three outputs without using a transformer.

Despite having a plurality of outputs, the multiple-output DC-DC converter of the present invention does not use a transformer, and therefore has a small size, low noise, and high efficiency.

Further, since the input / output ratio is a function of the duty ratio d, other output voltages can be adjusted by adjusting any one output voltage among the plurality of outputs by PWM control.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit configuration of a step-down DC-DC converter having three outputs according to an embodiment of the present invention.

FIG. 2 is a diagram showing a time chart of the operation of each switch of the embodiment shown in FIG.

3A is an equivalent circuit when the switch S _1A is on and the switch S _1B is off in the circuit shown in FIG. 1, and FIG. 3B is a circuit diagram of the circuit shown in FIG.
_The figure which shows an equivalent circuit when _1A is turned off and switch _S1B is turned on.

FIG. 4 is a diagram schematically showing changes in each output voltage when the duty ratio d is changed in the embodiment shown in FIG.

FIG. 5 is a diagram showing a modification of the embodiment shown in FIG.

FIG. 6 is a diagram showing a circuit configuration of a step-down DC-DC converter having two outputs, which is another embodiment of the present invention.

FIG. 7 is a diagram showing a modification of the embodiment shown in FIG.

FIG. 8 is a diagram showing a circuit configuration of a step-down DC-DC converter having two outputs which is still another embodiment of the present invention.

FIG. 9 is a diagram showing a modification of the embodiment shown in FIG.

FIG. 10 is a diagram showing a circuit configuration of a step-up DC-DC converter having three outputs, which is another embodiment of the present invention.

11 is a diagram showing a time chart of the operation of each switch of the embodiment shown in FIG.

12A is an equivalent circuit when the switch S _1A is turned on and the switch S _1B is turned off in the circuit shown in FIG. 10, and FIG. 12B is the switch S _{1 in the} circuit shown in FIG. _The figure which shows an equivalent circuit when _1A is turned off and switch _S1B is turned on.

13 is a diagram schematically showing changes in each output voltage when the duty ratio d is changed in the embodiment shown in FIG.

14 is a diagram showing a modification of the embodiment shown in FIG.

FIG. 15 is a diagram showing a circuit configuration of a step-up DC-DC converter having two outputs which is another embodiment of the present invention.

16 is a diagram showing a modification of the embodiment shown in FIG.

FIG. 17 is a diagram showing a circuit configuration of a step-up DC-DC converter having two outputs which is still another embodiment of the present invention.

18 is a diagram showing a modification of the embodiment shown in FIG.

FIG. 19 is a schematic configuration diagram of a three-output step-down DC-DC converter having a function of controlling the output voltage by further embodying the embodiment shown in FIG. 5 of the present invention.

FIG. 20 is a diagram showing an example of a conventional DC-DC converter having a plurality of outputs using a transformer.

FIG. 21 is a conventional single-output step-down DC that does not use a transformer.
-The figure which shows an example of a DC converter.

FIG. 22 is a conventional single output step-up DC that does not use a transformer.
-The figure which shows an example of a DC converter.

[Explanation of symbols]

L _1, L _2: Reactor _{C 0, C OUT1, C OUT2} , C OUT3: capacitor _{S 1A, S 1B, S 2} , S 3: Switch _{D 1, D 2, D 3} : Diode STR: switching transistor R _L1, R _L2 , R _L3 : load resistance r ₁ , r ₂ : resistance CP: comparator EA: error amplifier 10, 12, 20, 22: connection point 14, 24: common return line

Claims (6)

[Claims] 1. A first reactor, a capacitor, a second reactor, a means for connecting the first reactor, the capacitor, and the second reactor in series to a DC power supply, A first output capacitor whose one end is connected to a connection point between the DC power supply and the second reactor, and the other end of the first output capacitor are connected to the first reactor and the capacitor. First switching means for alternately connecting to a first connection point between them and a second connection point between the capacitor and the second reactor; and the first output capacitor described above. A second output capacitor whose one end is connected to the other end; and a second output capacitor which connects and disconnects the other end of the second output capacitor and the first connection point in synchronization with the first switching means. 2 switching hands DC-DC converter with a door. 2. The DC-DC converter according to claim 1, wherein one end of the first output capacitor is connected to one end of the third capacitor, the other end of the third capacitor is connected to the other end of the third capacitor. A third connection and disconnection between the second connection point and the first switching means in synchronization
DC-DC converter further comprising: 3. A first reactor, a capacitor, a second reactor, means for connecting the first reactor, the capacitor, and the second reactor in series to a DC power source, and A first output capacitor whose one end is connected to a connection point between the DC power supply and the second reactor, and the other end of the first output capacitor are connected to the first reactor and the capacitor. First switching means for alternately connecting to a first connection point between them and a second connection point between the capacitor and the second reactor; and the first output capacitor described above. A third output capacitor whose one end is connected to one end, and a third output capacitor which connects and disconnects between the other end of the third output capacitor and the second connection point in synchronization with the first switching means. Switching hands DC-DC converter with a door. 4. A first reactor, a capacitor, a second reactor, a first output capacitor, the first output capacitor, the first reactor, the capacitor, and the second reactor. Means for connecting a reactor in series; means for connecting a connection point between the second reactor and the first output capacitor to one end of a DC power supply; and the other end of the DC power supply for First switching means for alternately connecting to a first connection point between the first reactor and the capacitor and a second connection point between the capacitor and the second reactor; A second output capacitor having one end connected to a connection point between the first output capacitor and the first reactor, the other end of the second output capacitor, and the first connection Between the point and the The second DC-DC converter and a switching means for intermittently synchronously with the switching means. 5. The DC-DC converter according to claim 4, wherein a third output capacitor having one end connected to a connection point between the first output capacitor and the second reactor, A DC-DC converter further comprising: a third switching unit that connects and disconnects the other end of the third output capacitor and the second connection point in synchronization with the first switching unit. 6. A first reactor, a capacitor, a second reactor, a first output capacitor, the first output capacitor, the first reactor, the capacitor, and the second reactor. A means for connecting a reactor in series, a means for connecting a connection point between the second reactor and the first output capacitor to one end of the DC power supply, and the other end of the DC power supply, First switching means for alternately connecting a first connection point between the first reactor and the capacitor and a second connection point between the capacitor and the second reactor; A third output capacitor having one end connected to a connection point between the first output capacitor and the second reactor, the other end of the third output capacitor, and the second output capacitor. In front of the connection point The third DC-DC converter and a switching means for intermittently synchronously with the first switching means.