JP2003125576A - Dc-dc converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To materialize further improvement of the performance, such as smoothing the shifting of the movement region of itself, by the DC voltage of a battery or the like which is inputted and supplying desired DC voltage to load, and is used for each kind of electronic apparatus. SOLUTION: In a configuration, with input DC voltage Ei being inputted and output DC voltage, is supplied to load 6 from an output capacitor 5 via a step-down capacitor part 2 and a step-up capacitor part 3, the increase and decrease of power loss are controlled at the time of shifting action among a step-down movement region, an uncontrolled movement region, and a step-up movement region and the shifting is conducted smoothly, by having a movement region where the motion frequency of the step-down converter part 2 becomes lower the lower the input DC voltage is during step-down motion of the step- down converter part 2 and having a movement region, where the motion frequency of the step-up converter part 3 becomes lower the higher the input DC voltage Ei is during the step-up motion of the step-up converter part 3.

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 which is used in various electronic devices and receives a direct current voltage from a direct current power source such as a battery and supplies a desired direct current voltage to a load.

[0002]

2. Description of the Related Art As a technique relating to a DC-DC converter for controlling a DC voltage input from a DC power source such as a battery and supplying it to a load, the technique described in Japanese Utility Model Publication No. 6-70486 is known. . Fig. 9 shows the actual Kaihei 6-70
It is a circuit diagram which shows the structure of the conventional DC-DC converter disclosed by the 486 publication. As shown in FIG. 9, the input DC voltage Ei is input to the conventional DC-DC converter, and the first main switch unit 24 composed of a PNP transistor, the first rectifying unit 34 composed of a diode, the inductor 44, Second main switch means 25 composed of an NPN transistor and second rectifying means 3 composed of a diode.
5 and an output capacitor 45 are provided. The voltage Eo of the output capacitor 45 is output as the output DC voltage of this DC-DC converter.

The first main switch means 24, the first rectifying means 34 and the inductor 44 constitute a step-down converter section, and the inductor 44, the second main switch means 25 and the second rectifying means 35 constitute a step-up section. Is configured. The output DC voltage Eo is the resistance 15 having the resistance value R1.
It is detected by a series circuit of 1 and a resistor 152 having a resistance value R2. On the other hand, a series circuit of a first reference voltage source 161 that outputs the first reference voltage Vref1 and a second reference voltage source 162 that outputs the second reference voltage Vref2 is provided. The first control circuit 171 includes resistors 151 and 152.
Output detection voltage, which is the voltage at the connection point with, and the combined reference voltage
Vref1 + Vref2 is input to the first main switch means 2
The drive signal to 4 is output. The second control circuit 172 is
The output detection voltage and the reference voltage Vref2 are input, and a drive signal to the second main switch means 25 is output.

In the DC-DC converter configured as described above, the first control circuit 171 controls the ON / OFF of the first main switch means 24 to output the output DC voltage Eo by (1+
R1 / R2) · Try to adjust to (Vref1 + Vref2). On the other hand, the second control circuit 172 controls the on / off of the second main switch means 25 to change the output DC voltage Eo to (1
Try to adjust to + R1 / R2) · Vref2. As a result, the input DC voltage Ei is (1 + R1 / R2). (Vref1
If it is higher than + Vref2), the second main switch means 25 is turned off, and the first main switch means 24 is turned on and off to perform the step-down operation, whereby the output DC voltage Eo is (1 + R1 / R2).・ (Vref1 + Vref2)
Stabilized to. In addition, the input DC voltage Ei is (1 + R1
/ R2) · Vref2, the first main switch means 24 is turned on and the second main switch means 25 is turned on.
By turning on and off, and boosting operation,
The output DC voltage Eo is stabilized at (1 + R1 / R2) · Vref2.

Further, the input DC voltage Ei is (1 + R1 /
R2) ・ Vref2 or more, (1 + R1 / R2) ・ (Vref1 +
In the case of Vref2) or less, the first main switch means 24 is turned on and the second main switch means 25 is turned off. Therefore, the input DC voltage Ei is equal to the output DC voltage E
It is output directly as o. As described above, the conventional D
In the C-DC converter, the step-down operation and the step-up operation are not performed at the same time, thus preventing the power efficiency of the DC-DC converter from decreasing. In the above description, the voltage drop of each component when the current is conducted is ignored.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the C-DC converter, by providing an uncontrolled operation area between the step-down operation area and the step-up operation area,
The switching operation of the DC-DC converter is configured so that the step-down operation and the step-up operation are not performed at the same time, and the power conversion efficiency thereof is improved. Such a conventional DC-D
Since no switching loss occurs in the uncontrolled operation region of the C converter, the power conversion efficiency was higher than in the step-down operation region and the step-up operation region. Therefore, in the conventional DC-DC converter, the power loss increases or decreases during the transition operation between the step-down operation region and the non-control operation region or between the non-control operation region and the step-up operation region. There was a problem that the transition operation was not performed smoothly. INDUSTRIAL APPLICABILITY The present invention can smoothly perform the transition operation between the operation areas of the DC-DC converter.
The purpose is to further improve the performance of the C-DC converter.

[0007]

In order to achieve the above object, a DC-DC converter according to the present invention has an input DC power supply, a step-down converter section, a step-up converter section, and an output capacitor. DC- that supplies an input DC voltage from an input DC power supply to the load from the output capacitor via the step-down converter section and the step-up converter section
In the DC converter, the step-down converter section performs a step-down operation when the input DC voltage is higher than a first set voltage, and an operating region in which the operating frequency becomes lower as the input DC voltage becomes lower during the step-down operation. The boost converter unit performs a boost operation when the input DC voltage is lower than a second set voltage that is lower than the first set voltage, and the boost converter operates as the input DC voltage is higher during the boost operation. An operating region in which the frequency becomes low, and the input DC voltage is directly supplied to a load when the input DC voltage is between the first set voltage and the second set voltage. Has been done. DC configured in this way
In the −DC converter, the increase / decrease in power loss is suppressed, the transition operation between the operation regions can be smoothly performed, and the performance of the DC-DC converter can be improved.

Further, in the DC-DC converter according to the present invention, the inductor is shared with the step-down converter unit having the first main switch means connected to the input DC power supply, the first rectifying means and the inductor. Boosting converter section having a second main switch means and a second rectifying means, an output capacitor for supplying an output DC voltage to a load, the output DC voltage is detected, and a first set voltage and A second control voltage that outputs error information between the output DC voltage and a second control voltage that is lower than the first set voltage and that outputs the first control voltage that includes error information between the output DC voltage
And an oscillating voltage that periodically increases / decreases between a first predetermined voltage and a second predetermined voltage lower than the first predetermined voltage. An oscillation circuit having a function of slowing the rising speed or the falling speed of the oscillating voltage when it is between the first control voltage and the second control voltage; and the first control voltage and the oscillating voltage. In comparison, at least the second main switch means is compared with the first control drive circuit for controlling on / off of at least the first main switch means, and the second control voltage and the oscillating voltage are compared with each other to turn on / off the second main switch means. A second control drive circuit for controlling. DC configured in this way
-In the DC converter, during the transition operation between the uncontrolled operation region and the boost operation region, or during the transition operation between the buck-boost operation region and the boost operation region, the increase / decrease in power loss is suppressed, and the transition operation is performed smoothly. Be seen.

In the DC-DC converter according to the present invention, in addition to the function of outputting the first control voltage and the second control voltage, the output detection circuit having the above-mentioned configuration is provided with the first control voltage. The oscillation circuit has a function of outputting a first auxiliary control voltage having a predetermined potential difference, and the oscillation circuit, instead of when the oscillation voltage is between the first control voltage and the second control voltage, When the oscillating voltage is between the first auxiliary control voltage and the second control voltage, the oscillating voltage has a function of reducing the rising speed or the falling speed of the oscillating voltage. In the DC-DC converter configured as above,
By setting the auxiliary control voltage that determines the fluctuation area of the operating frequency separately from the control voltage, the fluctuation of the operating frequency can be limited to the vicinity of the uncontrolled operation area where the input / output voltage approaches or the vicinity of the buck-boost operation area. .

In the DC-DC converter according to the present invention, in addition to the function of outputting the first control voltage and the second control voltage, the output detection circuit having the above-mentioned configuration is provided with the second control voltage. The oscillation circuit has a function of outputting a second auxiliary control voltage having a predetermined potential difference, and the oscillation circuit, instead of when the oscillating voltage is between the first control voltage and the second control voltage, When the oscillating voltage is between the first control voltage and the second auxiliary control voltage, the oscillating voltage has a function of reducing the rising speed or the falling speed of the oscillating voltage. In the DC-DC converter configured as above,
By setting the auxiliary control voltage that determines the fluctuation area of the operating frequency separately from the control voltage, the fluctuation of the operating frequency can be limited to the vicinity of the uncontrolled operation area where the input / output voltage approaches or the vicinity of the buck-boost operation area. .

In the DC-DC converter according to the present invention, in addition to the function of outputting the first control voltage and the second control voltage, the output detection circuit having the above-mentioned configuration is provided with the first control voltage. A function of outputting a first auxiliary control voltage having a predetermined potential difference, and a function of outputting a second auxiliary control voltage having a predetermined potential difference from the second control voltage,
In the oscillation circuit, the oscillation voltage may be the first auxiliary control voltage and the second auxiliary control voltage instead of when the oscillation voltage is between the first control voltage and the second control voltage. In the meantime, it has a function of slowing down the rising speed or the falling speed of the oscillating voltage. D configured in this way
In the C-DC converter, by setting an auxiliary control voltage that determines the fluctuation region of the operating frequency separately from the control voltage, the fluctuation of the operating frequency is controlled in the vicinity of the uncontrolled operation region where the input / output voltage approaches, or the buck-boost operation region. It can be limited to the vicinity.

In the DC-DC converter according to the present invention, when the first control voltage having the above-mentioned configuration is higher than the first predetermined voltage and the second control voltage is lower than the second predetermined voltage, Alternatively, the oscillation circuit is configured to stop operating when the first control voltage is lower than the second predetermined voltage and the second control voltage is higher than the first predetermined voltage. . D configured in this way
In the C-DC converter, the power loss in the uncontrolled operation area can be further reduced.

A DC-DC converter according to another aspect of the invention has an input DC power supply, a step-down converter section, and an output capacitor, and inputs the DC input voltage from the input DC power supply to the step-down converter section. A DC-DC converter for supplying a load from an output capacitor, wherein the step-down converter section performs a step-down operation to stabilize the output DC voltage with respect to fluctuations in the input DC voltage, and the input DC voltage is low. It has an operating region where the operating frequency becomes lower. In the DC-DC converter configured as described above, the increase / decrease in power loss is suppressed, the transition operation between the operation regions can be smoothly performed, and the performance of the DC-DC converter can be improved.

A DC-DC converter according to another aspect of the invention has an input DC power supply, a step-up converter section, and an output capacitor, and inputs the DC input voltage from the input DC power supply to the step-down converter section. A DC-DC converter that supplies a load from an output capacitor, performs a boosting operation to stabilize the output DC voltage with respect to variations in the input DC voltage, and the operating frequency decreases as the input DC voltage increases. Has an operating area. In the DC-DC converter configured as described above, the increase / decrease in power loss is suppressed, the transition operation between the operation regions can be smoothly performed, and the performance of the DC-DC converter can be improved.

A DC-DC converter according to another aspect of the invention has an input DC power supply, a step-down converter section, a step-up converter section, and an output capacitor, and converts the input DC voltage from the input DC power supply into the step-down converter. A DC-DC converter that supplies the load from the output capacitor via a voltage converter and the boost converter, the step-down converter performs a step-down operation when the input DC voltage is higher than a set voltage, and the step-down During operation, the lower the input DC voltage, the lower the operating frequency of the step-down converter section has an operating region, the step-up converter section performs the step-up operation when the input DC voltage is lower than the set voltage, There is an operating region in which the higher the input DC voltage during boost operation, the lower the operating frequency of the boost converter section. , And it is configured to perform the step-down operation and the step-up operation at the same time when the input DC voltage is the set voltage vicinity. In the DC-DC converter configured as described above, the increase / decrease in power loss is suppressed, the transition operation between the operation regions can be smoothly performed, and the DC-DC converter
The performance of the DC converter can be improved.

According to another aspect of the invention, there is provided a DC-DC converter in which a step-down converter section having a first main switch means, a first rectifying means and an inductor connected to an input DC power source, and the inductor are shared. A boost converter section having a second main switch means and a second rectifying means, an output capacitor for supplying an output DC voltage to a load,
A second control that detects the output DC voltage, outputs a first control voltage having error information between the set voltage and the output DC voltage, and has a predetermined potential difference from the first control voltage. An output detection circuit that outputs a voltage and an oscillating voltage that periodically increases and decreases between a first predetermined voltage and a second predetermined voltage lower than the first predetermined voltage are output, and the oscillating voltage is output as the first predetermined voltage. The potential difference between the second predetermined voltage and the second control voltage is set to be equal to or more than the potential difference between the first control voltage and the second control voltage, and the oscillating voltage is set between the first control voltage and the second control voltage. When it is between the control voltage and the oscillation voltage, the oscillation circuit having the function of slowing down the rising speed or the falling speed of the vibration voltage is compared with the first control voltage and the vibration voltage,
A first control drive circuit for controlling at least the first main switch means on / off and a second control voltage for comparing at least the second control voltage and the oscillating voltage to control at least the second main switch means on / off. And a control drive circuit of. In the DC-DC converter configured as described above, the increase / decrease in power loss is suppressed, the transition operation between the operation regions can be smoothly performed, and the performance of the DC-DC converter can be improved.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a DC-DC converter according to the present invention will be described below with reference to the accompanying drawings.

<< First Embodiment >> FIG. 1 is a circuit diagram showing a configuration of a DC-DC converter according to a first embodiment of the present invention. As shown in FIG. 1, an input DC voltage Ei is input to the DC-DC converter according to the first embodiment of the present invention, the first main switch means 21 including a P-channel MOSFET and the first main switching means including a diode. Rectifying means 3
1, an inductor 4, a second main switch means 22 composed of an N-channel MOSFET, a second rectifying means 32 composed of a diode, and an output capacitor 5 are provided. In the DC-DC converter of the first embodiment, voltage Eo of output capacitor 5 is output as the output DC voltage. The step-down converter unit 2 is configured by the first main switch unit 21, the first rectifying unit 31, and the inductor 4, and the boost converter unit 3 is formed by the inductor 4, the second main switch unit 22, and the second rectifying unit 32. Is configured.

The output DC voltage Eo is detected by a series circuit of a first resistor 71 having a resistance value R1, a second resistor 72 having a resistance value R2, and a third resistor 73 having a resistance value R3. The reference voltage source 70 outputs a reference voltage Vref. The first error amplifier 74 includes a first resistor 71 and a second resistor 71.
The connection point voltage with the resistor 72 and the reference voltage Vref are input, and the first control voltage Ve1 is output. As for the first control voltage Ve1, the output DC voltage Eo is the first set voltage Eo1.
(= Vref. (R1 + R2 + R3) / R1) It decreases when it becomes higher, and it rises when it becomes lower.
The second error amplifier 75 receives the connection point voltage between the second resistor 72 and the third resistor 73 and the reference voltage Vref, and outputs the second control voltage Ve2. Second control voltage Ve2
The output DC voltage Eo is the second set voltage Eo2 (= Vr
ef ・ (R1 + R2 + R3) / (R1 + R2)) It decreases when it becomes higher, and it rises when it becomes lower. The output detection circuit 7 is composed of the reference voltage source 70, the resistors 71, 72, 73, the first error amplifier 74, and the second error amplifier 75.

As shown in FIG. 1, the oscillation circuit 8 is composed of an oscillation capacitor 80 and a charging / discharging circuit 81. In the charge / discharge circuit 81, the voltage Vc of the oscillation capacitor 80, which is an oscillating voltage, is the first predetermined voltage Vc1 and the second predetermined voltage Vc.
A charging / discharging current is passed through the oscillation capacitor 80 so as to increase / decrease periodically between 2 (<Vc1). In the first embodiment, the charging current and the discharging current are equal. The charging / discharging current when the oscillation voltage Vc, which is the voltage of the oscillation capacitor 80, is equal to or higher than the first control voltage Ve1 and when the oscillation voltage Vc is equal to or lower than the second control voltage Ve2 is I1. Further, the charging / discharging current when the oscillation voltage Vc is lower than the first control voltage Ve1 and higher than the second control voltage Ve2 is I2. The charge / discharge current is set to I1> I2. Therefore, the rising speed and the falling speed of the oscillating voltage Vc are Ve2 <Vc <Ve1.
It will be slowed down. That is, the rising slope and the falling slope of the oscillating voltage Vc become gentle when Ve2 <Vc <Ve1.

The first control drive circuit 9 includes a first comparator 9
1 and a first power amplifier 92. The first comparator 91 compares the first control voltage Ve1 with the oscillating voltage Vc and outputs a signal that becomes L level when Ve1> Vc. The first power amplifier 92 power-amplifies the output signal from the first comparator 91 and outputs the first main switch means 21.
A signal (driving signal Vg1) for turning on and off is output. The first control drive circuit 9 includes the first main switch means 2
The output DC voltage Eo is adjusted to approach the first set voltage Eo1 = Vref (R1 + R2 + R3) / R1 by controlling ON / OFF of 1. The second control drive circuit 10 is composed of a second comparator 101 and a second power amplifier 102. The second comparator 101 has a second control voltage Ve2.
And the oscillating voltage Vc are compared, and when Ve2 <Vc, a signal which becomes L level is output. The second power amplifier 102 power-amplifies the output signal from the second comparator 101 and outputs a signal (driving signal Vg2) for turning on and off the second main switch means 22. Second control drive circuit 10
Controls the second main switch means 22 to turn on / off the output DC voltage Eo to the second set voltage Eo2 = Vref.
Adjust so that (R1 + R2 + R3) / (R1 + R2) approaches.

Next, the operation of the DC-DC converter of the first embodiment configured as described above will be described. FIG. 2 is a waveform diagram showing the operation of each part of the DC-DC converter according to the first embodiment of the present invention. In FIG.
The oscillating voltage Vc, the first control voltage Ve1, and the second control voltage Ve when the input DC voltage Ei gradually decreases.
2, the on / off operation of the first main switch means 21 (driving signal Vg1), the on / off operation of the second main switch means 22 (driving signal Vg2), and the output DC voltage Eo are shown.

First, when the input DC voltage Ei is higher than the first set voltage Eo1 = Vref (R1 + R2 + R3) / R1, the second control voltage Ve2 is at the L level as shown in the area (a) of FIG. The second main switch means 22 is always off because it is fixed to. In this region, the first control voltage Ve1 and the oscillating voltage Vc intersect, so that the first main switch means 21 performs an on / off operation. That is, the DC-DC converter at this time operates as a step-down converter, and the output DC voltage Eo is stabilized to the first set voltage Eo1 = Vref. (R1 + R2 + R3) / R1. The ON time of the first main switch means 21 is T
On1, off time is Toff1, oscillation voltage Vc
Letting T be the cycle of, that is, the switching cycle, the relationship between the input and output voltages is: Eo / Ei = Ton1 / T.

In the region of FIG. 2 (a), the first control voltage Ve1 rises as the input DC voltage Ei decreases, the ON time Ton1 of the first main switch means 21 increases, and the OFF time Toff1 decreases. It gets shorter. The charging / discharging current I2 to the oscillating capacitor 80, which is also a determining factor of the on time Ton1 of the first main switch device 21, is set smaller than the charging / discharging current I1 which is a determining factor of the off time Toff1. Therefore, as the input DC voltage Ei decreases, the effect of the extended ON time Ton1 of the first main switch means 21 is greater and the switching cycle T becomes longer.

The input DC voltage Ei is equal to the first set voltage Eo
When 1 = Vref · (R1 + R2 + R3) / R1 is reached, the first control voltage Ve1 exceeds the first predetermined voltage Vc1 as shown in the region of FIG. 2 (b). As a result, the off time Toff1 of the first main switch means 21 becomes zero, and the first main switch means 21 is always on. In this region, the second control voltage Ve2 remains at the L level, so that the second main switch means 22 always remains in the off state. Therefore, in the region shown in FIG. 2B, the input DC voltage Ei is directly output as the output DC voltage Eo, which is an uncontrolled operation. In this state, the input DC voltage Ei is the second set voltage Eo2 = Vref.
-Continue until (R1 + R2 + R3) / (R1 + R2) is reached.

The input DC voltage Ei is the second set voltage Eo.
2 = Vref- (R1 + R2 + R3) / (R1 + R2)
When it becomes lower, the second control voltage Ve2 intersects with the oscillating voltage Vc as shown in the region (c) of FIG. 2, so that the second main switch means 22 performs an on / off operation. At this time, since the first main switch means 21 is always in the ON state, the DC-DC converter at this time operates as a step-up converter, and the output DC voltage Eo is the second set voltage Eo.
o2 = Vref- (R1 + R2 + R3) / (R1 + R2)
Stabilized to. The on time of the second main switch means 22 is Ton2, the off time is Toff2, and the oscillating voltage V
When the cycle of c, that is, the switching cycle is T, the relationship between the input and output voltages is: Eo / Ei = 1 / (1-Ton2 /
T).

In the region (c) of FIG. 2, the second control voltage Ve2 rises as the input DC voltage Ei decreases, the ON time Ton2 of the second main switch means 22 increases, and the OFF time Toff2 decreases. It gets shorter. The charging / discharging current I1 to the oscillating capacitor 80, which is also a determining factor of the on time Ton2 of the second main switch means 22, is set to be larger than the charging / discharging current I2 which is a determining factor of the off time Toff2. Therefore, as the input DC voltage Ei decreases, the shortened off time Toff2 of the second main switch means 22 has a greater influence, and the switching cycle T
Is getting shorter.

As described above, according to the first embodiment, the input DC voltage Ei is equal to the second set voltage Eo2 = Vref. (R
1 + R2 + R3) / (R1 + R2) Above, the first
Set voltage of Eo1 = Vref ・ (R1 + R2 + R3) /
In the case of R1 or less, the first main switch means 21 is in the on state, the second main switch means 22 is in the off state,
The input direct-current voltage Ei is directly output as the output direct-current voltage Eo in the non-controlled operation region. That is, it is possible to prevent a decrease in power efficiency in the DC-DC converter due to the step-down operation and the step-up operation being performed at the same time. Moreover, in the step-down operation region, the lower the input DC voltage Ei is, the longer the switching cycle T is, and the switching loss is reduced. Also in the boost operation region, the higher the input DC voltage Ei, the longer the switching cycle T and the switching loss is reduced. Therefore, in the first embodiment, an increase or decrease in power loss is suppressed during the transition operation between the step-down operation region and the uncontrolled operation region or during the transition operation between the uncontrolled operation region and the boost operation region. The transition operation is smoothly performed. In the description of the operation in the first embodiment, the voltage drop of each component when the current is conducted is ignored.

<< Second Embodiment >> Next, a DC-DC converter according to a second embodiment of the present invention will be described with reference to the attached FIGS. 3 and 4. FIG. 3 is a circuit diagram showing the configuration of the DC-DC converter according to the second embodiment of the present invention. FIG. 4 is a waveform diagram showing the operation of each part of the DC-DC converter of the second embodiment.

Referring to FIG. 3, the DC of the first embodiment described above.
The components having the same functions and configurations as those of the -DC converter are designated by the same reference numerals, and the description thereof will be omitted. The second embodiment differs from the configuration of the first embodiment shown in FIG. 1 in that output detection circuit 7 is provided with first offset circuit 76 and second offset circuit 77. In the output detection circuit 7, the first offset circuit 76 receives the first control voltage Ve1 and outputs the first control voltage Ve1.
The first auxiliary control voltage Vx1 lower than the control voltage Ve1 of 1 is output by a predetermined value. The second offset circuit 77 is the second
Of the second control voltage Ve2.
A second auxiliary control voltage Vx2 higher than the predetermined value by 2 is output.

The oscillation circuit 8 in the second embodiment is composed of an oscillation capacitor 80 and a charging / discharging circuit 81.
The charging / discharging circuit 81 uses an oscillating capacitor 80 that is an oscillating voltage.
Of the first predetermined voltage Vc1 and the second predetermined voltage Vc
A charging / discharging current is passed through the oscillation capacitor 80 so as to increase / decrease periodically between c2 (<Vc1). In the second embodiment, the charging current and the discharging current are equal. Let I1 be the charging / discharging current when the oscillation voltage Vc, which is the voltage of the oscillation capacitor 80, is equal to or higher than the first auxiliary control voltage Vx1 and when the oscillation voltage Vc is equal to or lower than the second auxiliary control voltage Vx2.
Further, the charge / discharge current when the oscillation voltage Vc is lower than the first auxiliary control voltage Vx1 and higher than the second auxiliary control voltage Vx2 is I2. These charge / discharge currents are set to I1> I2. Therefore, the rising speed and the falling speed of the oscillating voltage Vc are reduced when Vx2 <Vc <Vx1. That is, the rising slope and the falling slope of the oscillating voltage Vc are
When Vx2 <Vc <Vx1, it becomes gentle.

Next, the operation of the DC-DC converter of the second embodiment configured as described above will be described. FIG. 4 shows D of the second embodiment configured as described above.
The operation | movement waveform of each part in a C-DC converter is shown. In FIG. 4, as the input DC voltage Ei gradually decreases, the oscillation voltage Vc, the first control voltage Ve1, the first auxiliary control voltage Vx1, the second control voltage Ve2, and the second auxiliary control voltage Vx2. , ON / OFF operation of the first main switch means 21 (drive signal Vg1), ON / OFF operation of the second main switch means 22 (drive signal Vg2), and output DC voltage E
The state of o is shown respectively.

First, when the input DC voltage Ei is higher than the first set voltage Eo1 = Vref. (R1 + R2 + R3) / R1, the DC-DC converter operates as a step-down converter and the output DC voltage Eo is the first set voltage Eo1. Stabilized to. The ON time of the first main switch means 21 is T
When the on-time and the off-time are Toff1 and the cycle of the oscillating voltage Vc, that is, the switching cycle is T, the relationship between the input and output voltages is Eo / Ei = Ton1 / T as in the first embodiment.

As shown in the region (a) of FIG. 4, when the input DC voltage Ei is sufficiently high and the first auxiliary control voltage Vx1 is lower than the second predetermined voltage Vc2, the oscillation capacitor 80
Since the charging / discharging current to and from is I1, the period of the oscillating voltage Vc, that is, the switching period T is constant. But,
As the input DC voltage Ei decreases, the first control voltage Ve
The first auxiliary control voltage Vx1 rises with 1, and the first auxiliary control voltage Vx1 crosses the oscillation voltage Vc. As a result, as shown in the area (b) of FIG.
ON time Ton1 of the main switch means 21 becomes longer,
The off time Toff1 becomes shorter. In the second embodiment, the on-time Ton1 of the first main switch means 21.
The charging / discharging current I2 to the oscillating capacitor 80, which is also a determining factor of, is set to be smaller than the charging / discharging current I1 which is a determining factor of the off time Toff1. Therefore, as the input DC voltage Ei decreases, the effect of the extended ON time Ton1 of the first main switch means 21 is greater and the switching cycle T becomes longer.

Next, as shown in the area (c) of FIG.
The input DC voltage Ei is the first set voltage Eo1 = Vref
When (R1 + R2 + R3) / R1 is reached, the first main switch means 21 is always turned on. On the other hand, in this region, the second control voltage Ve2 remains at the L level, so that the second main switch means 22 always remains in the off state. Therefore, in the region of (c) of FIG. 4, the input DC voltage Ei is directly output as the output DC voltage Eo, which is an uncontrolled operation, and this uncontrolled operation is shown in (b) of FIG. This is the same as the uncontrolled operation in the area of.

Next, in the region shown in FIG. 4D, the input DC voltage Ei is the second set voltage Eo2 = Vref.
When it becomes lower than (R1 + R2 + R3) / (R1 + R2), the second control voltage Ve2 intersects with the oscillating voltage Vc, so that the second main switch means 22 is turned on / off. In this region, the first main switch means 21 is always on, so the DC-DC converter operates as a boost converter, and the output DC voltage Eo is the second set voltage Eo2 = Vref. (R1 + R2 + R3) / (R1
+ R2) is stabilized. Second main switch means 22
When the on-time of the above is Ton2, the off-time is Toff2, and the cycle of the oscillating voltage Vc, that is, the switching cycle is T, the relationship between the input and output voltages is Eo / Ei = 1 / (1-T
on2 / T).

In the region (d) of FIG. 4, the second auxiliary control voltage Vx2, which is set higher by ΔV2 than the second control voltage Ve2, intersects with the oscillation voltage Vc, and the charge / discharge current is I.
Switched between 1 and I2. As the input DC voltage Ei decreases, the second auxiliary control voltage Vx2 increases with the second control voltage Ve2, and the second main switch means 2
2 has a longer on time Ton2 and an off time Toff2.
Is getting shorter. In the second embodiment, the charging / discharging current I1 to the oscillation capacitor 80, which is also a determining factor of the on-time Ton2 of the second main switch means 22, is the off-time T.
It is set to a value larger than the charging / discharging current I2 which is a determining factor of off2. Therefore, as the input DC voltage Ei decreases, the shortened off time Toff2 of the second main switch means 22 has a greater influence, and the switching cycle T
Is getting shorter.

As shown in the area (e) of FIG. 4, when the input DC voltage Ei further decreases, the second auxiliary control voltage Vi
x2 becomes higher than the first predetermined voltage Vc1, and the oscillating voltage Vc
It will not intersect with c. Since the charging / discharging current to the oscillation capacitor 80 is I1, the cycle of the oscillating voltage Vc, that is, the switching cycle T is constant.

As described above, according to the second embodiment, when the input DC voltage Ei is the second set voltage Eo2 or more and the first set voltage Eo1 or less, the input DC voltage Ei is the output DC voltage Eo. The non-control operation region ((c) in FIG. 4) is output directly. That is, in the second embodiment,
DC due to simultaneous step-down and step-up operations
-A decrease in power efficiency in the DC converter can be eliminated. Further, in the step-down operation region ((b) of FIG. 4) close to the uncontrolled operation region, the lower the input DC voltage Ei, the longer the switching period T and the switching loss is reduced. Also in the boosting operation region ((d) of FIG. 4) close to the uncontrolled operation region, the higher the input DC voltage Ei, the longer the switching period T and the switching loss is reduced. Therefore, during the transition between the step-down operation region and the uncontrolled operation region, or during the transition between the uncontrolled operation region and the boost operation region, the increase / decrease in power loss is suppressed, and DC- of the second embodiment is suppressed. In the DC converter, the transition operation is smoothly performed.

Further, in the second embodiment, the step-down operation region in which the input DC voltage is sufficiently high and the step-up operation region in which the input DC voltage is sufficiently reduced operate at a constant switching cycle. That is, the fluctuation of the operating frequency can be limited to the vicinity of the uncontrolled operating region where the input / output voltage approaches. In the second embodiment, the first auxiliary control voltage and the second auxiliary control voltage are provided so that the operating frequency can be fixed in both the step-down operation and the step-up operation.
Depending on the input / output specifications and the like, even if the operation is limited to any one, the same effect as that of the second embodiment can be obtained. For example, when most of the range of the input DC voltage is higher than the desired output DC voltage, only the first auxiliary control voltage may be provided and the operating frequency may be fixed only during the step-down operation.

Further, in the second embodiment, the predetermined potential difference between the first control voltage Ve1 and the first auxiliary control voltage Vx1 is not a constant value but 1 as shown in FIG.
It is next functional. Further, the case where the predetermined potential difference between the second control voltage Ve2 and the second auxiliary control voltage Vx2 also has a linear function relationship instead of a constant value has been described. However, in the present invention, these relationships may be appropriately determined in consideration of how to change the operating frequency, easiness of the circuit configuration, and the like, and need not be constant values.
It is not limited to the linear functional relationship as in the second embodiment.

<< Third Embodiment >> Next, a DC-DC converter according to a third embodiment of the present invention will be described with reference to the attached FIG. FIG. 5 shows a third embodiment according to the present invention.
3 is a circuit diagram showing a configuration of a DC-DC converter of FIG. 5, components having the same functions and configurations as those of the components of the DC-DC converter according to the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted. The third embodiment differs from the first embodiment shown in FIG. 1 in that the oscillator circuit 8 includes a third comparator 82 and a fourth comparator 8.
3, the NOR circuit 84, and the PNP transistor 85 are provided.

A first control voltage Ve is applied to the third comparator 82.
1 is positively input and the second predetermined value Vc2 is negatively input.
The second control voltage Ve2 is negatively input to the fourth comparator 83, and the first predetermined value Vc1 is positively input to the fourth comparator 83. The outputs of the third comparator 82 and the fourth comparator 83 are input to the NOR circuit 84, and the output of the NOR circuit 84 is the PNP transistor 85.
Power is being received from the base terminal of. PNP transistor 8
5 is inserted in the power supply line to the charge / discharge circuit 81.

In the DC-DC converter of the third embodiment, when the output of the NOR circuit 84 becomes H, the PNP transistor 85 is turned off and the power supply from the input DC power supply 1 to the charging / discharging circuit 81 is cut off. Is configured. Therefore, in the DC-DC converter of the third embodiment, the first control voltage Ve1 is lower than the second predetermined voltage Vc2, and the second control voltage Ve2 is the first predetermined voltage Vc.
When it is higher than 1, the charging / discharging circuit 81 stops the inflow and outflow of the charging / discharging current to / from the oscillation capacitor. That is, the DC-DC converter of the third embodiment has a function of stopping the operation of the oscillation circuit 8.

The DC-DC converter of the third embodiment is
Since the input DC voltage Ei is configured as described above, the power supply to the charging / discharging circuit 81 is cut off in the uncontrolled operation region where the input DC voltage Ei is between the first set value Eo1 and the second set value Eo2. , The operation of the oscillation circuit 8 is stopped. Such a configuration does not require the oscillation circuit 8 to send the oscillating voltage Vc in the uncontrolled operation region, and thus the power consumption can be reduced by stopping the operation of the oscillation circuit 8.

<< Fourth Embodiment >> Next, a DC-DC converter according to a fourth embodiment of the present invention will be described with reference to the attached FIG. 6 is a fourth embodiment according to the present invention.
3 is a circuit diagram showing a configuration of a DC-DC converter of FIG. In FIG. 6, components having the same functions and configurations as those of the components of the DC-DC converter of the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted.

D of the above-described first to third embodiments
In the C-DC converter, the DC-DC converter having the step-down converter section and the step-up converter section has been described, but the present invention is not limited to such a configuration, and only the step-down converter section or the step-up converter section is provided. The present invention can be applied to the case of only a part. The sixth embodiment described below is a case of a DC-DC converter provided with only a step-down converter unit.

FIG. 6 is a diagram showing DC-of the fourth embodiment according to the present invention.
It is a circuit diagram which shows the structure of a DC converter. As shown in FIG. 6, the input DC voltage Ei is input to the DC-DC converter according to the fourth embodiment of the present invention, and the switch means 23 including a P-channel MOSFET, the diode 33, the inductor 40, and the output capacitor 5 are provided. Is provided. The voltage Eo of the output capacitor 5 is output as the output DC voltage. The switch means 23, the diode 33, and the inductor 40 constitute a step-down converter section.

The output DC voltage Eo has a first resistance 111 having a resistance value R1 and a second resistance 11 having a resistance value R2.
It is detected by a series circuit with 2. The reference voltage source 110, which is a DC voltage source, outputs a reference voltage Vref. The error amplifier 113 receives the connection point voltage between the first resistor 111 and the second resistor 112 and the reference voltage Vref, and outputs the control voltage Ve. This control voltage Ve is the output DC voltage E
o is the set voltage Eo1 = Vref (R1 + R2) / R1
It goes down as it goes higher, and goes up as it goes low. The offset circuit 114 also controls the control voltage Ve.
1 is input and the auxiliary control voltage Vx lower than the control voltage Ve by ΔV is output. The above-mentioned reference voltage source 110, the first
The output detection circuit 11 is configured by the resistor 111, the second resistor 112, the error amplifier 114, and the offset circuit 114.

The oscillation circuit 12 is composed of an oscillation capacitor 120 and a charging / discharging circuit 121. The charging / discharging circuit 121 converts the voltage Vc of the oscillation capacitor 120, which is an oscillating voltage, into a first predetermined voltage Vc1 and a second predetermined voltage Vc2.
A charging / discharging current is passed through the oscillation capacitor 120 so as to increase / decrease periodically between (<Vc1). In the fourth embodiment, the charging current and the discharging current are equal. The charge / discharge current when the oscillating voltage Vc is equal to or higher than the auxiliary control voltage Vx is I1. Further, the charging / discharging current when the vibration voltage Vc is lower than the auxiliary control voltage Vx is I2. These charge / discharge currents are set to I1> I2. Therefore, the rising speed (gradient when rising) and the falling speed (gradient when falling) of the oscillating voltage Vc are slowed down (gradually) when Vc <Vx.

Control drive circuit 13 in the fourth embodiment
Is composed of a comparator 131 and a power amplifier 132. The comparator 131 has a control voltage Ve and an oscillating voltage Vc.
And are compared, and when Ve <Vc, a signal that becomes L level is output. The power amplifier 132 power-amplifies the output signal of the comparator 131 and turns on / off the switch means 23. Therefore, the control drive circuit 13 controls the switch means 23 to turn on and off to set the output DC voltage Eo to the set voltage Eo1.
= Vref ・ (R1 + R2) / Try to adjust to R1.

Next, the operation of the DC-DC converter of the fourth embodiment having the above configuration will be described. The operation of the DC-DC converter according to the fourth embodiment is similar to the operation from the step-down operation region to the uncontrolled operation region in the DC-DC converter according to the second embodiment described above, and the operation waveform is as shown in FIG. This is the same as the areas a), (b) and (c). Therefore, the description of the operation from the step-down operation area to the uncontrolled operation area in the fourth embodiment will be omitted.

First, the input DC voltage Ei is equal to the set voltage Eo.
1 = Vref ・ (R1 + R2) / R1 sufficiently higher than
Since the auxiliary control voltage Vx is lower than the second predetermined voltage Vc2, the charge / discharge current is I1. That is, the cycle of the oscillating voltage Vc, that is, the switching cycle T of the switch means 23 is constant. In the control drive circuit 13, the control voltage Ve and the vibration voltage Vc are compared with each other, and the main switch means 2 is on / off controlled. As a result, the output DC voltage Eo is stabilized at the set voltage Eo1 = Vref. (R1 + R2) / R1. Assuming that the on time of the switch means 23 is Ton1, the off time is Toff1, and the cycle of the oscillating voltage Vc, that is, the switching cycle is T, the relationship between the input and output voltages is Eo / E.
i = Ton1 / T.

Next, when the input DC voltage Ei drops and the auxiliary control voltage Vx crosses the oscillating voltage Vc,
The on time Ton1 of the switch means 23 becomes longer and the off time Toff1 becomes shorter. In the fourth embodiment, the charging / discharging current I2 to the oscillating capacitor 120, which is also a determining factor of the on time Ton1 of the switch means 23, is set smaller than the charging / discharging current I1 which is a determining factor of the off time Toff1. Therefore, the ON time T of the switch means 23 is extended as the input DC voltage Ei is lowered.
The effect of on1 is larger, and the switching cycle T becomes longer.

Further, when the input DC voltage Ei reaches the first set voltage Eo1 = Vref (R1 + R2) / R1, the control voltage Ve reaches the first predetermined voltage Vc1.
As a result, the off time Toff1 of the switch means 23 becomes zero, and the switch means 23 is always on. That is, an uncontrolled operation in which the input DC voltage Ei is directly output as the output DC voltage Eo is performed.

As described above, according to the fourth embodiment, when the input DC voltage Ei is low and is close to the uncontrolled operation region, the switching period T becomes longer and the switching loss decreases as the input DC voltage Ei decreases. To be done. Eventually, the input DC voltage Ei becomes the set voltage Eo1 = Vref. (R1 + R
2) / R1 or less, the switch means 23 is always in the ON state, and the input DC voltage Ei is the output DC voltage Eo.
Is output directly as. That is, at this time, the operation is in the non-control operation area, and the operation is highly efficient with no switching loss.
Therefore, in the fourth embodiment, during the transition operation between the step-down operation region and the uncontrolled operation region, power loss is suppressed and the transition operation is smoothly performed. On the other hand, if the input DC voltage Ei is sufficiently high, the DC-
The DC converter operates at a constant switching cycle. That is, in the DC-DC converter according to the fourth embodiment, the fluctuation of the operating frequency can be limited to the vicinity of the uncontrolled operating region where the input / output voltage approaches.

In the fourth embodiment, DC
Although the case where the -DC converter is only the step-down converter has been described, it goes without saying that the DC-DC converter of the present invention can be similarly applied to the step-up converter. When the DC-DC converter of the present invention is a boost converter, when the input DC voltage is equal to or higher than the output DC voltage desired to be set, a highly efficient uncontrolled operation region without switching loss is obtained. Further, in this case, since the boosting operation in which the operating frequency rises as the input DC voltage decreases, the increase / decrease in power loss is suppressed during the transition operation between the uncontrolled operation region and the boosting operation region, and the transition operation is It is done smoothly.
Further, when the DC-DC converter of the present invention is a boost converter, when the input DC voltage Ei becomes sufficiently low, it operates at a constant switching cycle. That is, the fluctuation of the operating frequency can be limited to the vicinity of the uncontrolled operating region where the input / output voltage approaches. It is to be noted that the oscillating voltage is not necessary even in the uncontrolled operation region of the fourth embodiment, as in the third embodiment. Therefore, in the DC-DC converter of the fourth embodiment, the loss can be further reduced by configuring the oscillation circuit 12 to stop operating in the uncontrolled operation region.

<Fifth Embodiment> Next, a DC-DC converter according to a fifth embodiment of the present invention will be described with reference to the accompanying FIGS. 7 and 8. FIG. 7 is a circuit diagram showing the configuration of the DC-DC converter according to the fifth embodiment of the present invention. Referring to FIG. 7, the DC-DC of the first embodiment described above.
Components having the same functions and configurations as those of the components of the converter are designated by the same reference numerals, and the description thereof will be omitted. As shown in FIG. 7, DC-D according to the fifth embodiment of the present invention.
The input DC voltage Ei is input to the C converter,
First main switching means 21 made of P-channel MOSFET, first rectifying means 31 made of diode, inductor 4, second main switching means 22 made of N-channel MOSFET, second rectifying means 32 made of diode.
And an output capacitor 5 are provided. The voltage Eo of the output capacitor 5 is output as the output DC voltage. First
The main switch means 21, the first rectifying means 31, and the inductor 4 constitute the step-down converter section 2.
The inductor 4, the second main switching device 22, and the second rectifying device 32 constitute the boost converter unit 3.

The output DC voltage Eo has a first resistance 141 having a resistance value R1 and a second resistance 14 having a resistance value R2.
2 in series. The reference voltage source 140, which is a DC voltage source, outputs a reference voltage Vref. The error amplifier 143 receives the connection voltage between the first resistor 141 and the second resistor 142 and the reference voltage Vref, and receives the control voltage Vref.
Output e. The control voltage Ve decreases when the output DC voltage Eo becomes higher than the set voltage Eo1 = Vref · (R1 + R2) / R1 and increases when it becomes low. The control voltage Ve is input to the offset circuit 144, and the auxiliary control voltage V lower than the control voltage Ve by ΔV.
Output x. The above reference voltage source 140, the first resistor 1
The output detection circuit 14 is configured by 41, the second resistor 142, the error amplifier 143, and the offset circuit 144.

The oscillation circuit 15 is composed of an oscillation capacitor 150 and a charging / discharging circuit 151. Charge / discharge circuit 151
Is the first predetermined voltage Vc1 and the second predetermined voltage Vc2 (<Vc
A charging / discharging current is passed through the oscillating capacitor 150 so as to increase / decrease periodically between 1). In the fifth embodiment, the charging current and the discharging current are equal. The charging / discharging current when the vibration voltage Vc is equal to or higher than the control voltage Ve and when the vibration voltage Vc is equal to or lower than the auxiliary control voltage Vx is I1. Also,
The oscillation voltage Vc is lower than the control voltage Ve1 and the auxiliary control voltage V
The charge / discharge current when higher than x is I2. The charge / discharge current is set to I1> I2. Therefore, the oscillating voltage Vc
The ascending speed (inclination when ascending) and the descending speed (inclination when descending) are slowed (gradually) when Vx <Vc <Ve.

The first control drive circuit 9 includes a first comparator 9
1 and a first power amplifier 92. The first comparator 91 compares the control voltage Ve with the oscillating voltage Vc and outputs a signal that becomes L level when Ve> Vc. The first power amplifier 92 power-amplifies the output signal of the first comparator 91 to turn on / off the first main switch means 21. Therefore, the first control drive circuit 9 is
The main DC switch means 21 is controlled to be turned on and off to set the output DC voltage Eo to the set voltage Eo1 = Vref. (R1 + R2) /
Adjust to R1. The second control drive circuit 10 is composed of a second comparator 101 and a second power amplifier 102. The second comparator 101 compares the auxiliary control voltage Vx with the oscillating voltage Vc, and outputs a signal that becomes L level when Vx <Vc. The second power amplifier 102 power-amplifies the output signal of the second comparator 101 to turn on / off the second main switch means 22. Therefore, the second control drive circuit 10 controls the second main switch means 22 to turn on and off to set the output DC voltage Eo to the set voltage Eo1 = Vref.
Adjust to (R1 + R2) / R1.

Next, DC- of the fifth embodiment according to the present invention
The operation of the DC converter will be described. FIG. 8 is a waveform diagram showing the operation of each part in the DC-DC converter of the fifth embodiment. In FIG. 8, the input DC voltage E
As i gradually decreases, the oscillation voltage Vc, the control voltage Ve, the auxiliary control voltage Vx, and the first main switch means 21.
The on / off operation (driving signal Vg1) and the on / off operation of the second main switch means 22 (driving signal Vg2) are shown.

First, the input DC voltage Ei is equal to the set voltage Eo.
1 = Vref ・ (R1 + R2) / R1 when higher than FIG.
Since the auxiliary control voltage Vx is fixed at the L level, as shown in the area (a) of FIG.
Is always off. In this region, the control voltage V
Since e and the oscillating voltage Vc intersect, the first main switch device 21 is turned on and off. That is, D of the fifth embodiment
The C-DC converter operates as a step-down converter, and the output DC voltage Eo is a set voltage Eo1 = Vref. (R1 +
Stabilized to R2) / R1. When the on time of the first main switch means 21 is Ton1, the off time is Toff1, and the cycle of the oscillating voltage Vc, that is, the switching cycle is T, the relationship between the input and output voltages is: Eo / Ei = Ton1 /
It becomes T.

At this time, the control voltage Ve rises as the input DC voltage Ei decreases, and the first main switch means 21
The ON time Ton1 becomes longer and the OFF time Toff1 becomes shorter. In the fifth embodiment, the charging / discharging current I2 to the oscillating capacitor 140, which is also a determining factor of the on time Ton1 of the first main switch device 21, is the off time T1.
It is set smaller than the charging / discharging current I1 which is a determining factor of off1. Therefore, as the input DC voltage Ei decreases, the ON time T of the first main switch means 21 is extended.
The effect of on1 is larger, and the switching cycle T becomes longer.

The input DC voltage Ei decreases and the set voltage Eo
When approaching 1 = Vref (R1 + R2) / R1, the auxiliary control voltage Vx crosses the oscillating voltage Vc as shown in the region (b) of FIG. At this time, the second main switch means 22 also turns on and off. Furthermore, Vc <which is the ON period of the second main switch means 22
At Vx, since the charging / discharging current is I1, the oscillating voltage Vc
, The switching period T is constant. In this operating region, both the first main switching means 21 and the second main switching means 22 are turned on and off. That is, it is a step-up / down operation region in which the step-down converter section and the step-up converter section operate simultaneously. Assuming that the on time of the second main switch means 22 is Ton2, the relationship between the input and output voltages is Eo / Ei.
= Ton1 / (T-Ton2).

When the input DC voltage Ei further decreases and falls below the set voltage Eo1 = Vref. (R1 + R2) / R1,
As shown in the area (c) of FIG.
Becomes higher than the first predetermined voltage Vc1. At this time, the off time Toff1 of the first main switch means 21 becomes zero, and the first main switch means 21 is always on.
The DC-DC converter of the fifth embodiment operates as a step-up converter in which only the second main switch means 22 is turned on and off, and the output DC voltage Eo is the set voltage Eo1 = Vref.
-Stabilized to (R1 + R2) / R1. The on time of the second main switch means 22 is Ton2, and the off time thereof is To.
Assuming that ff2 and the cycle of the oscillating voltage Vc, that is, the switching cycle are T, the relationship between the input and output voltages is: Eo / Ei = 1
/ (1-Ton2 / T).

At this time, as the input DC voltage Ei decreases, the auxiliary control voltage Vx increases, the ON time Ton2 of the second main switch means 22 increases, and the OFF time Toff increases.
2 becomes shorter. In the fifth embodiment, the charging / discharging current I1 to the oscillation capacitor 80, which is also a determining factor of the on time Ton2 of the second main switch device 22, is set to be larger than the charging / discharging current I2 which is a determining factor of the off time Toff2. There is. Therefore, as the input DC voltage Ei decreases, the shortened off time Toff2 of the second main switch means 22 has a larger influence, and the switching cycle T becomes shorter.

As described above, according to the fifth embodiment, the input DC voltage Ei is equal to the set voltage Eo1 = Vref. (R1 +
In the vicinity of R2) / R1, both the first main switch means 21 and the second main switch means 22 are in the step-up / down operation region in which the on / off operation is performed. However, since its operating frequency is lowered, it is possible to suppress an increase in switching loss due to simultaneous step-down operation and step-up operation. Moreover, in the step-down operation region, the lower the input DC voltage Ei is, the longer the switching cycle T is, and the switching loss is reduced. Also in the boost operation region, the higher the input DC voltage Ei, the longer the switching cycle T and the switching loss is reduced. Therefore, in the DC-DC converter of the fifth embodiment, the power loss increases or decreases during the transition operation between the step-down operation region and the buck-boost operation region, or during the transition operation between the buck-boost operation region and the boost operation region. It is suppressed and the transition operation is performed smoothly.

Also in the DC-DC converter of the fifth embodiment, as shown in the second embodiment, by further adding the auxiliary control voltage, in the step-down operation region where the input DC voltage is sufficiently high, Alternatively, it can be operated at a constant switching cycle in the boosting operation region where the input DC voltage is sufficiently reduced. That is, with such a configuration, the fluctuation of the operating frequency in the DC-DC converter can be limited to the vicinity of the buck-boost operation region where the input / output voltage approaches.

[0070]

As is apparent from the above detailed description of the embodiments, the present invention has the following effects. The DC-DC converter according to the present invention receives the input DC voltage, supplies the output DC voltage from the output capacitor to the load via the step-down converter section and the step-up converter section, and the input DC voltage during the step-down operation. The lower the operating frequency is, the lower the operating frequency of the step-down converter section is, so that the power consumption during the transition operation between the step-down operation area and the uncontrolled operation area or the transition operation between the step-down operation area and the buck-boost operation area is reduced. The increase in loss is suppressed,
This has the effect that the transition operation is performed smoothly. Further, the DC-DC converter according to the present invention has an operating region in which the operating frequency of the boosting converter unit becomes lower as the input DC voltage is higher during the boosting operation, so that there is an uncontrolled operating region and a boosting operating region. During the transition operation, or during the transition operation between the buck-boost operation region and the boost operation region, increase / decrease in power loss is suppressed, and the transition operation is smoothly performed.

Further, in the DC-DC converter according to the present invention, the input DC voltage is input, and the output DC voltage is supplied from the output capacitor to the load via the step-down converter section. By having the operating region in which the operating frequency is low, an increase in power loss is suppressed during the transition operation between the step-down operation region and the uncontrolled operation region, and the transition operation is smoothly performed. Alternatively, in the DC-DC converter according to the present invention, the input DC voltage is input, the output DC voltage is supplied from the output capacitor to the load via the boost converter unit, and the higher the input DC voltage, the higher the operating frequency. By having the lower operating region, increase / decrease in power loss is suppressed during the transition operation between the uncontrolled operation region and the boosting operation region, and the transition operation is smoothly performed.

The DC-DC converter of the present invention is
By setting the auxiliary control voltage that determines the fluctuation area of the operating frequency separately from the control voltage, the fluctuation of the operating frequency can be limited to the vicinity of the uncontrolled operation area where the input / output voltage approaches or the vicinity of the buck-boost operation area. . Furthermore, the DC-DC converter of the present invention has the function of stopping the operation of the oscillation circuit in the uncontrolled operation region, so that the power loss in the uncontrolled operation region can be further reduced.

[Brief description of drawings]

FIG. 1 is a DC-DC in a first embodiment according to the present invention.
It is a circuit diagram which shows the structure of a converter.

FIG. 2 is a DC-DC in the first embodiment according to the present invention.
It is a wave form diagram which shows operation | movement of a converter.

FIG. 3 is a DC-DC in the second embodiment according to the present invention.
It is a circuit diagram which shows the structure of a converter.

FIG. 4 is a DC-DC in the second embodiment according to the present invention.
It is a wave form diagram which shows operation | movement of a converter.

FIG. 5 is a DC-DC in the third embodiment according to the present invention.
It is a circuit diagram which shows the structure of a converter.

FIG. 6 is a DC-DC in the fourth embodiment according to the present invention.
It is a circuit diagram which shows the structure of a converter.

FIG. 7 is a DC-DC in the fifth embodiment according to the present invention.
It is a circuit diagram which shows the structure of a converter.

FIG. 8 is a DC-DC in the fifth embodiment according to the present invention.
It is a wave form diagram which shows operation | movement of a converter.

FIG. 9 is a circuit diagram showing a configuration of a conventional DC-DC converter.

[Explanation of symbols]

1-input DC power supply 2 Step-down converter section 3 Boost converter section 4 inductor 5 output capacitors 6 load 7 Output detection circuit 8 oscillator circuits 9 First control drive circuit 10 Second control drive circuit 21 First Main Switch Means 31 First Rectifying Means 22 Second main switch means 32 Second rectifying means

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5H730 AA14 AS01 AS04 AS05 BB15                       BB86 BB88 DD04 EE59 FD01                       FG05 FG07 FG22

Claims (10)

[Claims] 1. An input DC power supply, a step-down converter section,
A DC-DC converter having a step-up converter section and an output capacitor, and supplying an input DC voltage from the input DC power source from the output capacitor to a load via the step-down converter section and the step-up converter section. The step-down converter section has an operation region that performs a step-down operation when the input DC voltage is higher than a first set voltage, and the operating frequency becomes lower as the input DC voltage becomes lower during the step-down operation, In the boost converter unit, the input DC voltage is the first
The boosting operation is performed when the voltage is lower than the second setting voltage that is lower than the setting voltage, and the operating frequency becomes lower as the input DC voltage becomes higher during the boosting operation. A DC-DC converter configured to supply an input DC voltage directly to a load when it is between a first set voltage and the second set voltage. 2. A step-down converter section having a first main switch means connected to an input DC power supply, a first rectifying means and an inductor, a second main switch means and a second main switch means sharing the inductor.
A step-up converter section having a rectifying means, an output capacitor for supplying an output DC voltage to a load, and a step of detecting the output DC voltage and having error information between the first set voltage and the output DC voltage. An output detection circuit which outputs a first control voltage and outputs a second control voltage having error information between the second set voltage lower than the first set voltage and the output DC voltage; An oscillating voltage that periodically increases or decreases between a voltage and a second predetermined voltage lower than the first predetermined voltage, and the oscillating voltage is between the first control voltage and the second control voltage. An oscillating circuit having a function of reducing the rising speed or the falling speed of the oscillating voltage in a certain case is compared with the oscillating voltage, and the on / off control of at least the first main switch means is performed. First to do 2. The DC according to claim 1, further comprising: a control drive circuit, and a second control drive circuit that compares the second control voltage and the oscillating voltage to control at least on and off of the second main switch means. -DC converter. 3. The output detection circuit has a function of outputting the first control voltage and the second control voltage, and a first auxiliary control voltage having a predetermined potential difference from the first control voltage. The oscillating circuit is configured to output the oscillation voltage to the first auxiliary control voltage instead of when the oscillation voltage is between the first control voltage and the second control voltage. 3. The DC-DC converter according to claim 2, wherein the DC-DC converter has a function of reducing the rising speed or the falling speed of the oscillating voltage when it is between the control voltage and the second control voltage. 4. The output detection circuit has a function of outputting the first control voltage and the second control voltage, and a second auxiliary control voltage having a predetermined potential difference from the second control voltage. The oscillation circuit is configured such that the oscillation voltage is the first control voltage instead of when the oscillation voltage is between the first control voltage and the second control voltage. 3. The DC-DC converter according to claim 2, wherein the DC-DC converter has a function of reducing the rising speed or the falling speed of the oscillating voltage when it is between the second auxiliary control voltages. 5. The output detection circuit has a function of outputting the first control voltage and the second control voltage, and a first auxiliary control voltage having a predetermined potential difference from the first control voltage. And a function of outputting a second auxiliary control voltage having a predetermined potential difference from the second control voltage, wherein the oscillation circuit has the oscillation voltage of the first control voltage and the first control voltage. Instead of when it is between two control voltages, when the oscillating voltage is between the first auxiliary control voltage and the second auxiliary control voltage, the rising speed or the falling speed of the oscillating voltage is reduced. DC-DC according to claim 2, which has the function of
converter. 6. The first control voltage is higher than the first predetermined voltage and the second control voltage is lower than the second predetermined voltage, or the first control voltage is the first control voltage. 6. The oscillation circuit is configured to stop operating when the second control voltage is lower than the second predetermined voltage and the second control voltage is higher than the first predetermined voltage. DC-DC converter. 7. An input DC power supply, a step-down converter section,
A DC-DC converter having an output capacitor and supplying an input DC voltage from the input DC power source to the load from the output capacitor via the step-down converter unit, wherein the step-down converter unit is the input DC voltage. DC-DC converter having an operation region in which a step-down operation is performed so as to stabilize the output DC voltage with respect to the fluctuation of 1), and the operating frequency decreases as the input DC voltage decreases. 8. An input DC power supply, a boost converter section,
A DC-DC converter having an output capacitor and supplying the input DC voltage from the input DC power source to the load from the output capacitor via the step-down converter unit, wherein DC-DC having an operating region in which a boosting operation is performed to stabilize the output DC voltage, and the operating frequency decreases as the input DC voltage increases.
converter. 9. An input DC power supply, a step-down converter section,
A DC-DC converter having a step-up converter section and an output capacitor, and supplying an input DC voltage from the input DC power source from the output capacitor to a load via the step-down converter section and the step-up converter section. The step-down converter section has an operation region in which the step-down operation is performed when the input DC voltage is higher than a set voltage, and the operating frequency of the step-down converter section becomes lower as the input DC voltage is lower during the step-down operation. However, the boost converter unit performs a boosting operation when the input DC voltage is lower than a set voltage, and an operating region in which the operating frequency of the boost converter unit decreases as the input DC voltage increases during the boosting operation. If the input DC voltage is near the set voltage, the step-down operation and the step-up operation are performed at the same time. The DC-DC
converter. 10. A step-down converter section having a first main switch means connected to an input DC power source, a first rectifying means, and an inductor, a second main switch means sharing the inductor, and a second main switch means.
A first converter having a rectifying means, an output capacitor for supplying an output DC voltage to a load, the output DC voltage, and error information between a set voltage and the output DC voltage. An output detection circuit that outputs a voltage and outputs a second control voltage having a predetermined potential difference from the first control voltage; a first predetermined voltage and a second lower voltage than the first predetermined voltage. An oscillating voltage that periodically increases and decreases between the first control voltage and the second control voltage, and a potential difference between the first predetermined voltage and the second predetermined voltage is output. Is set to be equal to or more than a potential difference between the first control voltage and the second control voltage, and has a function of reducing the rising speed or the falling speed of the vibration voltage when the vibration voltage is between the first control voltage and the second control voltage. An oscillation circuit, and the first control voltage A first control drive circuit that compares the oscillating voltage with at least the first main switch means to control ON / OFF, and compares the second control voltage and the oscillating voltage with at least the second The DC-DC converter according to claim 9, further comprising: a second control drive circuit that controls ON / OFF of the main switch unit.