JP2003047238A - Battery-driven electronic apparatus and mobile communication apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery-driven electronic apparatus and a mobile communication apparatus which can realize an extended operation life of a battery. SOLUTION: Even if a time, when an output voltage of a battery 201 becomes lower than a power supply voltage required by a load 206 including a wireless communication power amplifier by discharge characteristics showing a battery voltage change rate of not less than 0.25, is earlier than that of a conventional lithium ion battery, while the output voltage of the battery is higher than the power supply voltage required by the load, a voltage of step-up/step-down converter 200 is set at a prescribed power supply voltage with a step-down operation mode and, if the output voltage of the battery is lowered to a value lower than the power supply voltage required by the load, the voltage of the step-up/ step-down converter 200 is set at a prescribed power supply voltage with a step-up operation mode. With such a constitution, even if a battery employing new material having a high energy density is used, an extended operation life of the battery can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery-driven electronic device using a battery as an input source and a mobile communication device such as a mobile phone or a mobile communication terminal on which the battery-driven electronic device is mounted.

[0002]

2. Description of the Related Art Including wireless communication devices and information terminals,
An electronic device that uses a battery as a power source, which requires convenience of portability, is compact and lightweight, and has a usable time after charging if the battery is a secondary battery or after battery replacement if the battery is a primary battery. Longer time is required.

As such a battery-powered electronic device,
The configuration shown in FIG. 19 is general. As shown in FIG. 19, a conventional battery-powered electronic device includes a conventional lithium ion battery, specifically, a lithium cobalt oxide for a positive electrode, graphite for a negative electrode, and a nonaqueous solvent containing a lithium supporting electrolyte as an electrolytic solution. It uses a battery 401, which is typified by one having an average battery voltage of 3.7 V at room temperature as an input source, and comprises a switching means 402, a rectification switching means 403, an inductor 404 and an output capacitor 405. A predetermined power supply voltage Eo is supplied to the load 406 via the step-down converter.

Here, the terms will be explained. The "average battery voltage" is the time integral of the battery voltage when discharging at the rated current from the rated charge state to the rated discharge capacity divided by the discharge time.The "rated charge end voltage" is the rated discharge capacity. Battery voltage at the end of charging operation required to obtain, "rated discharge end voltage" is the battery voltage when the rated discharge capacity is obtained,
"Rated end-of-discharge voltage" is defined as the battery voltage when a large change occurs in the slope of the discharge voltage characteristic when discharging at the rated current.

First, the operation of the step-down converter will be described. When the voltage of the battery 401 is Ei, when the switching means 402 is turned on, the inductor 404 outputs the battery output voltage (hereinafter, referred to as battery voltage) Ei,
A difference (Ei-Eo) from the power supply voltage Eo is applied. At this time, current flows from the battery 401 to the output capacitor 405 via the switching means 402 and the inductor 404. As the current of the inductor 404 increases, magnetic energy is accumulated in the inductor 404. This period is Ton.

Next, when the switching means 402 is turned off, the voltage of the inductor 404 is inverted, the rectification switching means 403 becomes conductive, and the power supply voltage Eo is applied to the inductor 404. At this time, the current of the inductor 404 flows to the output capacitor 405 via the rectification switching means 403. This current decreases and the magnetic energy stored in the inductor 404 is released. This period is Toff.

When the storage and release of the magnetic energy are balanced through the on / off operation of the switching means 402, the increase / decrease in the current flowing through the inductor 404 is also balanced. When the inductance of the inductor 404 is L, the relationship of (Ei−Eo) · Ton / L = Eo · Toff / L is established. Switching cycle T = Ton + To
If ff, there is a relation of Eo / Ei = Ton / T between the input and output of the step-down converter.

That is, the step-down converter can adjust the power supply voltage Eo to the load 406 under the restriction of Ei> Eo against the fluctuation of the battery voltage Ei by controlling the ON / OFF of the switching means 402.

On the contrary, when the power supply voltage Eo required to be supplied to the load 406 is higher than the battery voltage Ei,
A step-up converter is used instead of the step-down converter. A configuration using a boost converter is disclosed in, for example, Japanese Patent Laid-Open No.
-315320.

The conventional lithium-ion battery as the battery 401 is characterized in that the discharge characteristic is flat, that is, the battery voltage drop due to discharge is small (the battery voltage change rate is small). As a result, the battery voltage and the power supply voltage required to supply to the load 406 can be brought close to each other, the loss in the step-down converter can be reduced, and this relationship does not change with discharge, so that the battery has Energy can be used efficiently.

In the configuration of the conventional battery-driven electronic device, when the step-down converter is used, the battery voltage E
i must be higher than the power supply voltage Eo required to supply the load. On the other hand, in order to operate the step-down converter efficiently, the battery voltage Ei should be close to the power supply voltage Eo. On the contrary, when the boost converter is used, the battery voltage Ei must be lower than the power supply voltage Eo required to supply the load. To operate the boost converter efficiently, the battery voltage Ei is equal to the power supply voltage Ei.
The point that it is better to be closer to o is the same as in the case of the step-down converter.

Therefore, the characteristics required for the battery are that the battery voltage Ei is slightly higher or lower than the power source voltage Eo and the discharge characteristics are flat. Batteries have been increased in capacity while satisfying such characteristics. By increasing the capacity with the same weight or volume, the battery usage time, which is the period until the battery voltage that decreases with discharge reaches the lower limit voltage that can be used, has been lengthened.

It should be noted that the flatter the discharge characteristics, the more the battery voltage tends to decrease remarkably toward the end of discharge. In other words, there is little energy left at this point. The conventional lithium-ion battery, which uses lithium cobalt oxide for the positive electrode, graphite for the negative electrode, and a non-aqueous solvent containing a lithium-supporting electrolyte for the electrolyte and has an average battery voltage of 3.7 V at room temperature, has the best discharge characteristics at present. It is a thing.

[0014]

However, as battery-driven electronic devices are becoming smaller and more sophisticated, there is a demand for smaller batteries and larger capacities, that is, improved energy density. The conventional lithium-ion battery is approaching the theoretical limit for increasing the capacity. Therefore,
A lithium ion battery using a new material that enables improvement of the energy density of the battery is required, but a battery using a material that realizes this high energy density is compared to conventional lithium ion batteries. There are problems that the average battery voltage drops and the battery voltage change rate increases.

A lithium ion battery using such a new material is incorporated into a device in which a conventional lithium ion battery is used, and the power supply voltage required by the load in the electronic device is the rated end-of-charge voltage of the battery. Between the battery and the rated end-of-discharge voltage, the battery voltage drops with discharge, and the time it takes to drop below the power supply voltage required by the load is faster than that of a conventional lithium-ion battery. However, there is a problem that the operating time of the device is shorter than that of the conventional lithium ion battery.

Further, a lithium ion battery made of a new material having a low average battery voltage and a large battery voltage change rate is used.
It is also possible to increase the battery voltage as a cell and combine it with a step-down converter. However, because the voltage difference between the input and output becomes large, it is difficult to achieve high efficiency of the step-down converter, and because the input voltage becomes high, it becomes necessary to increase the breakdown voltage of the capacitor and the semiconductor. Further, there are problems that efficiency is lowered, and the size of the component becomes large and the size cannot be reduced.

According to the present invention, the lithium ion battery, which is a new material that enables the energy density of the battery to be improved, has a low average battery voltage and a large battery voltage change rate.
When this battery is used in a battery-powered electronic device, the energy of the battery can be reduced by combining a lithium-ion battery and a buck-boost converter, which are new materials, against the problem that the energy with increased capacity cannot be fully utilized. It was made paying attention to the fact that can be effectively utilized.

That is, an object of the present invention is to provide a battery-powered electronic device capable of prolonging the battery usage time and also compatible with batteries having various discharge characteristics, and the battery-powered electronic device mounted on the battery. To provide such a mobile communication device.

[0019]

In order to achieve the above object, the first battery-powered electronic device according to the present invention has an open circuit voltage after reaching the rated charge cutoff voltage, Ec, and a rated discharge cutoff voltage. When the open circuit voltage after reaching the temperature is Ed, the voltage difference (Ec-Ed) is divided by the Ec, and the battery voltage change rate is 0.25 or more. Using the output voltage as the input source, depending on the output voltage of the battery,
At least a step-down operation mode and a step-up operation mode are provided to output a predetermined voltage, and a step-up / step-down converter is provided, and a load to which an output voltage of the step-up / step-down converter is supplied as a power supply voltage is provided.

According to this structure, the battery voltage change rate is 0.
Due to the discharge characteristic of 25 or more, even when the output voltage of the battery is lower than the power supply voltage required by the load for a shorter time than the conventional lithium-ion battery, the buck-boost converter needs the output voltage of the battery for the load. If it is higher than the power supply voltage to be set, set to the predetermined power supply voltage by the step-down operation mode,
When the output voltage of the battery drops and becomes lower than the power supply voltage required by the load, the voltage is set to a predetermined power supply voltage in the boosting operation mode. As a result, even for a lithium secondary battery, for example, using a new material having a high energy density, it is possible to realize a long battery usage time.

In order to achieve the above object, the second battery-powered electronic device according to the present invention has an open circuit voltage Ec after reaching the rated charge cutoff voltage and an open circuit voltage after reaching the rated discharge cutoff voltage. When the circuit voltage is Ed, the voltage difference (Ec-Ed) is divided by the Ec, and the battery has a discharge characteristic such that the battery voltage change rate is 0.25 or more. The battery output voltage is used as an input source. A buck-boost converter that performs a buck-boost operation mode according to the output voltage of the battery and outputs a predetermined voltage, and a load to which the output voltage of the buck-boost converter is supplied as a power supply voltage are provided.

According to this structure, the battery voltage change rate is 0.
Due to the discharge characteristic of 25 or more, even if the output voltage of the battery is lower than the power supply voltage required by the load for a shorter time than the conventional lithium-ion battery, the buck-boost converter operates in the buck-boost operation mode. Set the output voltage to the power supply voltage required by the load. As a result, even for a lithium secondary battery, for example, using a new material having a high energy density, it is possible to realize a long battery usage time.

In the first and second battery-driven electronic devices, the battery is a prismatic battery, and the energy density per unit volume of the prismatic battery is preferably 460 Wh / l or more.

Alternatively, in the first and second battery-driven electronic devices, the battery is a cylindrical battery, and the energy density per unit volume of the cylindrical battery is 530 Wh / l.
The above is preferable.

In the first and second battery-powered electronic devices, the power supply voltage required to supply the load is within the range between the rated end-of-charge voltage and the rated end-of-discharge voltage of the battery. The difference between the average battery voltage due to the discharge characteristics of the battery and the power supply voltage to the load is preferably within a predetermined range.

As a result, the loss in the buck-boost converter can be reduced, and the battery can be used for a longer time.

In the first and second battery-driven electronic devices, the power supply voltage required to supply the load has a predetermined fluctuation range, and the whole or part of the fluctuation range of the power supply voltage. And all or part of the range between the rated end-of-charge voltage and the rated end-of-discharge voltage of the battery, and in this case, the power supply voltage required to be supplied to the load is
There is a predetermined fluctuation range, the generation distribution of the required power supply voltage in the predetermined fluctuation range has one peak value, the required power supply voltage at the peak of the generation distribution and the average battery voltage accompanying the discharge characteristics of the battery It is preferable that the difference between and is within a predetermined range.

As a result, the loss in the buck-boost converter can be reduced and the battery can be used for a longer time.

In the first and second battery-powered electronic devices, the load includes a power amplifier for wireless transmission, and the battery-powered electronic device having such a configuration is mounted on mobile communication equipment.

In the first battery-powered electronic device, when the difference between the power supply voltage to the load and the output voltage of the battery is within a predetermined range, the buck-boost converter turns on the active component interposed between its input and output. It is preferable to have a function of fixing to the state because the loss in the buck-boost converter can be further reduced and the battery can be used for a longer time.

In this case, the step-up / down converter of the first configuration has a first switching means having one end connected to one end of the battery, one end connected to the other end of the first switching means, and the other end connected to the battery. A first rectifying switching means connected to the other end of the inductor, an inductor having one end connected to the other end of the first switching means, one end connected to the other end of the inductor, and the other end connected to the other end of the battery. A second switching means connected to the second switching means, one end of which is connected to one end of the second switching means, the other end of which is connected to one end of the load; and one end of which is connected to one end of the load, The other end is connected to the other end of the battery and the other end of the load, the output capacitor that supplies the power supply voltage to the load, the power supply voltage at the output capacitor is detected, and the detected power supply voltage and the step-down operation mode are performed. 1 set The error signal with the value (Eoh) is output as the first control signal (Ve1), and the error signal with the detected power supply voltage and the second set value (Eol) for performing the boosting operation mode is controlled by the second control. According to the detection circuit that outputs as the signal (Ve2) and the first control signal, the power supply voltage is the first
In accordance with the first control drive circuit for ON / OFF controlling the first switching means and the second control signal, the power supply voltage is adjusted to the second set value. As described above, it is preferable to include a second control drive circuit that controls ON / OFF of the second switching unit.

The detection circuit includes a series circuit of the first detection resistor, the second detection resistor and the third detection resistor to which a power supply voltage is applied, a reference voltage source for outputting a reference voltage, and A first error amplifier that receives a connection point potential between the first detection resistor and the second detection resistor and a reference voltage and outputs a first control signal; a second detection resistor and a third detection resistor; A second error amplifier that receives the connection point potential and the reference voltage and outputs a second control signal.

According to the above structure, the step-up / down converter of the first structure operates as a step-down converter when the output voltage Ei of the battery is higher than the first set value Eoh, and the power supply voltage is set to the first value. Adjust to the set value of 1. When the output voltage Ei of the battery drops and becomes lower than the first set value Eoh of the power supply voltage (higher than the second set value Eol), both the step-down operation and the step-up operation are stopped and the through voltage is passed. Functions as a mode. When the output voltage Ei of the battery further decreases and becomes lower than the second set value Eol of the power supply voltage, it operates as a boost converter and adjusts the power supply voltage to the second set value.

As a result, the difference between the output voltage Ei of the battery and the power supply voltage Eo to the load is within a predetermined range (<(Eoh-E
ol)), it functions as a through mode in which both the step-down operation and the step-up operation are stopped, so that the loss in the buck-boost converter can be reduced and the battery can be used for a long time.

In the first battery-powered electronic device, when the difference between the power supply voltage to the load and the battery output voltage is within a predetermined range, the buck-boost converter is a part of the components interposed between its input and output. Or having the function of short-circuiting all,
This is preferable in that the loss in the buck-boost converter can be further reduced and the battery can be used for a longer time.

In this case, the buck-boost converter of the second structure has a first switching means having one end connected to one end of the battery, one end connected to the other end of the first switching means, and the other end connected to the battery. A first rectifying switching means connected to the other end of the inductor, an inductor having one end connected to the other end of the first switching means, one end connected to the other end of the inductor, and the other end connected to the other end of the battery. Second switching means connected, one end of the first switching means is connected to one end of the first switching means, third switching means is connected to the other end of the inductor, and one end of the second switching means A second rectifying switching means connected to the load and the other end to one end of the load; one end connected to one end of the load; the other end connected to the other end of the battery and the other end of the load; Supply voltage The power supply voltage at the output capacitor and the output capacitor is detected, and an error signal between the detected power supply voltage and the first set value for performing the step-down operation mode is output as the first control signal to detect the detected power supply voltage. The power supply voltage is adjusted to the first set value in accordance with the detection circuit that outputs an error signal with respect to the second set value for performing the boosting operation mode as the second control signal, and the first control signal. So first
And a first control drive circuit for controlling on / off of the switching means and a second switching means so that the power supply voltage is adjusted to the second set value according to the second control signal. A second control drive circuit for controlling, and a level at which the first control signal fixes the first switching means in the ON state and the second control signal fixes the second switching means in the OFF state. And a third control drive circuit for turning on the third switching means.

According to this configuration, in addition to the advantage of the first step-up / step-down converter, by turning on the third switching means, an inductor having a large DC resistance component, that is, a loss, is short-circuited. Therefore, it is possible to reduce the loss as compared with the buck-boost converter having the first configuration, and it is possible to further extend the battery usage time.

Alternatively, in the first battery-driven electronic device, the buck-boost converter of the third structure has a first switching means having one end connected to one end of the battery and one end having the first switching means.
First rectification switching means connected to the other end of the switching means, the other end connected to the other end of the battery, one end connected to the other end of the first switching means, and one end of the inductor Second switching means connected to the other end, the other end being connected to the other end of the battery, and a second switching means having one end connected to one end of the second switching means and the other end connected to one end of the load. Rectification switching means, one end connected to one end of the inductor, the other end connected to the other end of the second rectification switching means, one end connected to one end of the load, the other end connected to the battery Output capacitor connected to the other end of the load and the other end of the load to supply the power supply voltage to the load, and the first set value for detecting the power supply voltage at the output capacitor and performing the step-down operation mode with the detected power supply voltage With A detection circuit that outputs a difference signal as a first control signal and outputs an error signal between the detected power supply voltage and a second set value for performing the boosting operation mode as a second control signal; A first control drive circuit that controls ON / OFF of the first switching unit so that the power supply voltage is adjusted to the first set value according to the signal, and the power supply voltage according to the second control signal. So as to be adjusted to the second set value, a second control drive circuit for ON / OFF controlling the second switching means, and a level at which the first control signal fixes the first switching means in the ON state. And a third control drive circuit for turning on the third switching means when the second control signal is at a level that fixes the second switching means in the off state.

According to this structure, in addition to the advantages of the first embodiment of the step-up / down converter, by turning on the third switching means, the inductor having a large DC resistance component, that is, a loss, is short-circuited. Therefore, it is possible to reduce the loss as compared with the buck-boost converter having the first configuration, and it is possible to further extend the battery usage time.

Alternatively, in the second battery-driven electronic device, the buck-boost converter of the fourth structure has a first inductor having one end connected to one end of the battery and one end connected to the other end of the first inductor. Switching means connected to the other end of the battery, one end connected to the other end of the first inductor, one end connected to the other end of the coupling capacitor, and the other end connected to the battery Second connected to the other end of
Of the inductor, one end of which is connected to one end of the second inductor, the other end of which is connected to one end of the load, and one end of which is connected to one end of the load and the other end of which is the other end of the battery and the load. An output capacitor connected to the other end for supplying a power supply voltage to the load, and a control driving means for controlling on / off of the switching means for adjusting the power supply voltage to a predetermined value required for supplying the load. It is preferable to provide.

According to this structure, the ripple component of the input current can be reduced, that is, the abrupt change from the discharge current of the battery can be reduced, so that the characteristic deterioration of the battery can be prevented, the shortening of the life can be suppressed, and the battery can be used. A longer time can be realized.

Alternatively, in the first battery-driven electronic device, the buck-boost converter of the fifth configuration has a first inductor having one end connected to one end of the battery and one end connected to the other end of the first inductor. A switching means connected to the other end of the battery, the other end connected to the other end of the battery, the first rectification switching means connected to the other end of the first inductor, and the other end of the first rectification switching means. And a first capacitor having one end connected to the other end of the battery
Second rectifying and switching means connected to the other end of the rectifying and switching means, and second rectifying and switching means having one end connected to the other end of the second switching means and the other end connected to the other end of the battery. A second inductor whose one end is connected to one end of the second rectification switching means and whose other end is connected to one end of the load; and one end which is connected to one end of the load and whose other end is connected to the other end of the battery and the load. Intermediate voltage setting value for detecting the intermediate voltage (E1) at the second capacitor connected to the other end and supplying the power supply voltage to the load and the first capacitor, and performing the boost operation mode And a power supply voltage setting for detecting the power supply voltage (Eo) in the second capacitor and outputting the detected error voltage signal as a first control signal and performing the step-down operation mode. Error signal with the value A second detection circuit for outputting a second control signal, in response to a first control signal, so that the intermediate voltage at the first capacitor is adjusted to an intermediate voltage set value,
A first control drive circuit for controlling ON / OFF of the first switching means, and a second control drive circuit for adjusting the power supply voltage of the second capacitor to the power supply voltage set value according to the second control signal. For controlling on / off of the switching means of the second
And a control drive circuit of

According to this structure, unlike the buck-boost converter of the first to fourth structures, the preceding stage is a boost converter,
With the configuration in which the latter stage is the step-down converter, since the latter stage step-down converter has a continuous output current, it is possible to reduce the ripple voltage of the power supply voltage and the capacitance of the second capacitor at the same time. As a result, it can be adapted even to applications that require a large change in the power supply voltage in a short time.

In this case, the intermediate voltage set value is obtained by adding the maximum output voltage required by the load to the voltage obtained by multiplying the resistance component between the first capacitor and the second capacitor by the maximum output current required by the load. It is preferable that the voltage values are set to different values.

As a result, when the load demands the maximum output voltage and the maximum output current, the step-down converter in the subsequent stage is
The second switching means can be operated in an efficient state where the second switching means is always in the conductive state.

[0046]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
2 is a circuit block diagram showing a schematic configuration of a battery-driven electronic device according to the embodiment of FIG. In FIG. 1, reference numeral 1 is a conventional lithium-ion battery using lithium cobalt oxide for the positive electrode, graphite for the negative electrode, and a non-aqueous solvent containing a lithium-supporting electrolyte for the electrolyte, and having an average battery voltage of 3.7 V at room temperature as discharge characteristics. Compared with, the battery has a discharge characteristic that is graded with time and has a battery voltage change rate of 0.25 or more. Here, the "battery voltage change rate" means a voltage difference (Ec-, where Ec is an open circuit voltage after reaching the rated charge cutoff voltage and Ed is an open circuit voltage after reaching the rated discharge cutoff voltage). It is a value obtained by dividing Ed) by the above Ec.

Reference numeral 2 is a step-up / down converter using the battery 1 as an input source, and reference numeral 3 is a load to which the output voltage of the step-up / down converter 2 is input as a power supply voltage.

Further, FIG. 2 shows a typical discharge characteristic (a) of the battery 1 and a power supply voltage (b) required to be supplied to the load 3. For comparison, a conventional lithium ion battery is shown. The discharge characteristic (c) is additionally shown.

FIG. 4 is a cross-sectional view showing the structure of the coin cell for evaluation manufactured as the battery 1. FIG. 4 will be described.

A negative electrode mixture was prepared by mixing 7.5 g of the negative electrode powder, 2 g of graphite powder as a conductive agent, and 0.5 g of polyethylene powder as a binder. 7.5 g of positive electrode powder and 2 g of conductive agent,
0.5 g of polyvinylidene fluoride powder was mixed as a binder to prepare a positive electrode mixture. 0.1 g of this mixture was added to a diameter of 17.5.
The electrode 5 was pressure-molded to have a thickness of mm and placed in a case 6. Next, the microporous polypropylene separator 7 is attached to the electrode 5
Put it on. The test counter electrode 8 was arranged in a state of being separated from the electrode 5 by the microporous polypropylene separator 7. Specifically, the test counter electrode 8 uses metallic lithium.

1.5 mol / l of supporting salt LiPF ₆
A mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1: 1 was poured as a non-aqueous electrolyte into a coin cell for evaluation. A sealing plate 10 in which metal Li having a diameter of 17.5 mm is adhered on the inside and a polypropylene gasket 9 is attached on the outer peripheral portion
Was placed and the test cell was sealed.

In this coin-type cell for evaluation, when the negative electrode mixture was evaluated, constant current charging (reaction in which lithium was inserted into the active material) was performed at a constant current of 0.5 mA / cm ² until the terminal voltage became 0V. The battery voltage is 1.5.
Discharge (reaction in which lithium is released from the active material) was performed at a current density of 0.5 mA / cm ² until the voltage reached V, and a charge / discharge curve was obtained. When evaluating the positive electrode mixture, 0.5 mA / cm
Perform constant current charging (reaction of releasing lithium from the active material) at a constant current of ² until the terminal voltage reaches 4.25V,
Continue to 0.5mA / c until the battery voltage reaches 3.0V
Discharge (reaction in which lithium is inserted into the active material) was performed at a current density of m ² , and a charge / discharge curve was similarly obtained. Using this, the time average of the discharge voltage of the positive electrode and the negative electrode, the average discharge potential, the characteristic shape or the capacity was measured. The results of measuring the battery discharge average voltage of various materials using this evaluation coin-type cell are shown in Table 1, Table 2, Table 3 and Table 4.

[0054]

[Table 1]

[0055]

[Table 2]

[0056]

[Table 3]

[0057]

[Table 4]

A cylindrical battery was prototyped using a material selected from these materials. This manufacturing method will be described.

As the positive electrode active material, oxide-based positive electrode active materials LiNiO ₂ , LiCoO ₂ and LiMn _{2 are used.}
O ₄ was examined.

LiNiO₂Is LiOH and Ni (OH)₂When
Are mixed in a prescribed molar ratio and heated in air at a temperature of 900 ° C.
Synthesized by heating, 100 mesh or less
What was classified into was used. LiCoO₂Is Li₂CO₃When
Co (OH)₂And at a predetermined molar ratio,
Synthesized by heating in air at a temperature of 1
The one classified to 00 mesh or less was used. LiMn₂
O_FourIs Li₂CO₃And MnO ₂And are mixed at a predetermined molar ratio,
Synthesized by heating at 800 ° C.
A mesh classified below was used.

To 100 g of the above positive electrode active material, 10 g of acetylene black as a conductive agent and 8 g of polyvinylidene fluoride as a binder were added, and N, N-dimethylformamide was added as a solvent thereto, and they were sufficiently mixed. A positive electrode paste was prepared. This positive electrode paste was applied to an aluminum core material, dried and rolled to obtain a positive electrode 11 shown in FIG.

On the other hand, when a non-oxide type positive electrode is used,
An ink prepared by dissolving an organic compound having a sulfur, thiol or thiolate group in an organic solvent was coated on an aluminum foil and dried.

As the negative electrode active material, multi-component alloys and metal nitrides were examined. These active materials were pulverized into powder, acetylene black as a conductive agent, and styrene-butadiene rubber (SBR) as a binder were mixed in a weight ratio of 70:20:10, and N, It was made into a paste using N-dimethylformamide. This paste was applied to a copper core material and dried to obtain a negative electrode 12 shown in FIG.
In the case of metallic lithium, a foil was attached to a copper core material to give a negative electrode.

The procedure for producing a cylindrical battery will be described below with reference to FIG. The positive electrode lead 14 made of aluminum was attached to aluminum of the positive electrode core material by ultrasonic welding. Similarly, the negative electrode lead 15 made of the same material was joined to the negative electrode core material copper by laser spot welding. A strip-shaped porous polypropylene separator 13 having a width between the positive electrode and the negative electrode, which is wider than both electrode plates.
The whole structure was wound in a spiral shape through. Further, insulating plates 1 made of polypropylene are provided above and below the electrode body, respectively.
After placing 6 and 17 into the battery case 18 and forming a step on the upper part of the battery case 18, 1.5 mol /
A liter of a mixed solution of EC and DMC in an equal volume, in which LiPF ₆ was dissolved, was injected and sealed with a sealing plate 19 to obtain a battery.

In the comparative battery using an oxide system for the positive electrode and a graphite system for the negative electrode at an ambient temperature of 20 ° C. and a charging current of 0.2 CmA (1 C is a 1-hour rate current) for the cylindrical battery thus manufactured, Constant current charging was performed up to 4.2V. Similarly, batteries using an oxide system for the positive electrode and an alloy system and a nitride system for the negative electrode were charged to 4.0 V and 3.8 V, respectively. Batteries using a thiolate or thiol group-containing organic compound having sulfur for the positive electrode and a nitride system and metallic lithium for the negative electrode were charged to 3.6 V and 4.0 V, respectively. The first discharge was performed at a current of 0.2 CmA to 3.0 V in a comparative battery using an oxide system for the positive electrode and a graphite system for the negative electrode. Similarly, all the batteries used in the examples were discharged to 1.5V. After recharging under the above conditions, discharge current was discharged at a current density of 2 CmA to a predetermined voltage. The battery voltage, discharge shape, discharge capacity, etc. of the battery system obtained by combining various positive and negative electrode active materials by using this cylindrical battery were measured.

FIG. 6 shows the discharge characteristics of various combinations of active materials using the cylindrical battery thus obtained.
Battery A exhibits the characteristics of a battery having a relatively high voltage in which an oxide type is used for the positive electrode and a graphite type is used for the negative electrode. Batteries B, C, and D show the characteristics of batteries in which an oxide system is used for the positive electrode and an alloy system or a nitride system is used for the negative electrode. Battery E exhibits the characteristics of a battery in which a positive electrode is made of an organic material having a sulfur-containing thiolate or thiol group and a negative electrode is made of a nitride material.

In general, the open circuit state after charge and discharge changes in the process in which the positive and negative electrode active materials change to the equilibrium potential. Therefore, regardless of the set rated end voltage of charge and discharge, there is a voltage drop on the charge side and a discharge side. In the voltage rise is seen. As shown in FIG. 7, the open circuit voltage after reaching the rated end-of-charge voltage is Ec,
When the open circuit voltage after reaching the rated end-of-discharge voltage is Ed, the battery voltage change rate (Ec-Ed) / Ec, which is the value obtained by dividing the voltage difference (Ec-Ed) by the open circuit voltage Ec, is expressed as:
For example, battery A shows 0.21 and battery E shows 0.35.

From these results, it can be said that a material system having a large discharge capacity tends to have a large rate of change in battery voltage, that is, to have a discharge characteristic inclined with time. In the present invention,
A battery having discharge characteristics with a battery voltage change rate of 0.25 or more is used. In addition, the average battery voltage of these material batteries tends to decrease.

The battery-powered electronic device of this embodiment having the above-described structure will be described with reference to FIGS. 1, 2 and 3.

The lithium-ion battery, which is a new material and has a discharge characteristic with a battery voltage change rate of 0.25 or more, used in the battery 1 which is a constituent element of the present invention, has a large discharge capacity.
That is, it is possible to increase the energy density per unit volume or per unit weight. On the other hand, as shown in FIG. 2, as compared with the discharge characteristic (c) of the conventional lithium-ion battery, the discharge characteristic of the battery is inclined with time such that the battery voltage decreases with discharge, and the average battery voltage is low. It has the characteristic (a). (D) is a rated end-of-charge voltage of a conventional lithium-ion battery, (e) is an end-of-discharge voltage, (f) is a rated end-of-charge voltage of a lithium-ion battery made of a new material, and (g) is an end-of-discharge voltage. . In other words, (d)-(e) is the voltage drop due to the discharge of the conventional lithium ion battery, and (f)-(g) is the voltage drop due to the discharge of the lithium ion battery of the new material. .
This voltage drop is larger in the new material lithium-ion battery, and the absolute level is also smaller. Therefore, in the battery-driven electronic device having the conventional configuration, the power supply voltage (b) required to be supplied to the load 3 is shorter than the usage time (T1) of the discharge characteristic (c) of the conventional lithium ion battery (T1). It will fall below T2).

Therefore, by adopting a circuit configuration in which the output voltage of the battery 1 is input to the step-up / down converter 2, as shown in FIG.
When the discharge characteristic (a) of the battery 1 is higher than the power supply voltage (b) required to be supplied to the load 3 as shown in (1), the buck-boost converter 2 performs a step-down operation (indicated by arrow D), and the battery 1 When the discharge characteristic (a) of (1) becomes lower than the power supply voltage (b) required to be supplied to the load 3, the buck-boost converter 2 performs a boosting operation (indicated by an arrow U), so that the buck-boost converter is operated. Usage time when not incorporated (T2)
The operating time (T3) that exceeds the operating time (T1) of the conventional lithium-ion battery is significantly exceeded, and the large discharge capacity of the battery 1, that is, the energy stored in the battery can be effectively used, enabling long-term use. Become.

Here, it is assumed that the load is 3 V, 100 mA, and the power consumption is 0.3 W. Average battery voltage at room temperature 3.7
V, a discharge capacity of 800 mAh, a positive electrode of lithium cobalt oxide, a negative electrode of carbon, a conventional lithium-ion battery using a non-aqueous solvent containing a lithium supporting electrolyte as an electrolyte and a conventional step-down converter battery-driven electronic device combined In this case, the battery usage time is 8 hours.

On the other hand, LiNiO 2 was used as an active material for the positive electrode having an average battery voltage of 3.3 V at room temperature and a discharge capacity of 1100 mAh.
_In the case of the present embodiment in which a lithium ion battery made of a new material using Ti ₆ Sn ₅ as a negative electrode active material is combined with a buck-boost converter, the battery usage time is 10 hours.
It can be extended to 2 hours.

(Second Embodiment) FIG. 8 shows a second embodiment of the present invention.
It is a figure which shows the structure of the battery drive type electronic device and mobile communication apparatus which concern on embodiment of this. In the present embodiment, the load includes a power amplifier for wireless transmission that transmits a burst-like signal as in the time division multiplexing method. In FIG. 8, 21 is a battery having a characteristic that the power density is higher than that of a battery having a conventionally used composition, but has a discharge characteristic inclined with time, and 22 is a step-up / down converter having the battery 21 as an input. Yes, 23 is a power amplifier to which the output voltage of the buck-boost converter is input. Reference numeral 25 is an input terminal of the power amplifier 23, and 26 is an output terminal of the power amplifier 23. Reference numeral 24 is a control means for controlling the supply of the output voltage of the step-up / down converter 22 as the power supply voltage of the power amplifier 23 during the period in which the power amplifier 23 operates to amplify the transmission signal.

The operations of the battery-driven electronic device and mobile communication device of this embodiment will be described below.

Since the power amplifier 23 sends out a burst-like signal, the control means 24 supplies power only when the power amplifier 23 sends out a signal for power saving. Power amplifier 23
Outputs power-amplified signals input from the input terminal 25. For this power amplification, the power amplifier 23 needs a power supply voltage above a certain level. On the other hand, if the power supply voltage is supplied more than necessary, the power loss in the power amplifier 23 increases. For example, PDC (Personal Digital Cellula)
The power supply voltage required for the r) type power amplifier is 3V, the average battery voltage is 3.7V, and the discharge capacity is 800mAh. The positive electrode is lithium cobalt oxide, the negative electrode is carbon,
The output voltage of a conventional lithium-ion battery using a non-aqueous solvent containing a lithium-supporting electrolyte as the electrolyte is directly input to the power amplifier. However, as the power consumption of multifunctional mobile phones tends to increase, as described above, it is necessary to increase the capacity of the battery in order to extend the usage time of the mobile phone.

Therefore, like the configurations of the battery-driven electronic device and the mobile communication device of this embodiment shown in FIG. 8, the battery has an average battery voltage of 3.3 V and a discharge capacity of 1100 mAh.
By combining the lithium-ion battery 21, which is a new material using LiNiO ₂ as the positive electrode active material and Ti ₆ Sn ₅ as the negative electrode active material, and the buck-boost converter 22, the voltage of the battery 21 is the power supply voltage of the power amplifier 23. If it is higher than this, the step-up / down converter 22 supplies the necessary power supply voltage to the power amplifier 23 by the step-down operation, so that the efficiency of the power amplifier 23 becomes good. In addition, when the voltage of the battery 21 is lower than the power supply voltage of the power amplifier 23, the step-up / down converter 22 converts the voltage of the battery 21 into a voltage required for the power amplifier 23 by a boosting operation. Can be achieved for a long time.

(Third Embodiment) FIG. 9 shows the third embodiment of the present invention.
2 is a configuration diagram of a battery-driven electronic device and a mobile communication device according to the embodiment of FIG. In this embodiment, the load is CDMA.
(Code Division Multiple Access) type wireless transmission power amplifier. In FIG. 9, reference numeral 21 denotes a battery having a characteristic that the power density is higher than that of a battery having a conventionally used composition, but the discharge characteristic is inclined with time. A voltage converter, and 23 is a power amplifier that uses the output voltage of the step-up / down converter as a power supply voltage. Reference numeral 25 is an input terminal of the power amplifier 23, and 26 is an output terminal of the power amplifier 23. Reference numeral 24 is a control means for controlling the output voltage of the step-up / down converter 23.

The power amplifier 23 needs a power supply voltage higher than a certain level depending on the transmission power, and conversely, if the power supply voltage is too high, the power loss in the power amplifier 23 increases. That is, the power amplifier 23 has a suitable power supply voltage according to the transmission power. The control means 24 has a function of controlling the power supply voltage to the power amplifier 23 in which the transmission power fluctuates according to the usage environment of the battery-driven electronic device of this embodiment such as the radio wave condition and the distance from the radio base station.

The operation of the battery-driven electronic device and mobile communication equipment of this embodiment will be described below with reference to FIGS. 10 and 11A.
And it demonstrates using FIG. 11B.

In FIG. 10, (d) is the discharge characteristic of the battery 21, and (f) is the variable range of the power supply voltage required by the load. (G) is a general discharge characteristic of a conventional lithium-ion battery for comparison. FIG. 11A is a characteristic diagram showing the relationship between the output power of the amplifier, which is the transmission power of the power amplifier 23, and the power supply voltage required by the power amplifier 23,
FIG. 11B is a characteristic diagram showing the output power of the amplifier which is the transmission power of the power amplifier 23 and the probability of occurrence of the output power. As shown in FIG. 11B, the probability of occurrence is high in the center, and as a result, the power supply voltage required by the power amplifier 23 is most required in the center of the variable range. For example, the variable range of the power supply voltage of the CDMA power amplifier 23 is about 1.5V to 3.5V.

Conventionally, lithium cobalt oxide is used for the positive electrode, carbon is used for the negative electrode, and has an average battery voltage of 3.7 V and a discharge capacity of 800 mAh as shown in the discharge characteristic (g) of FIG.
The output voltage of a conventional lithium-ion battery using a non-aqueous solvent containing a lithium-supporting electrolyte as an electrolyte is input to a power amplifier via a step-down converter.

On the other hand, in the present embodiment, the average battery voltage 3.3 V and the discharge capacity 1 as shown in FIG.
LiNiO as the active material of the positive electrode having 100 mAh
₂ , a lithium ion battery 21 made of a new material using Ti ₆ Sn ₅ as the negative electrode active material and a buck-boost converter 22 are combined. Thus, even when the voltage change width of the battery 21 is large and the variable range of the power supply voltage of the power amplifier 23 is large, the buck-boost converter 22 can handle both the step-down operation and the step-up operation, so that the capacity is increased. The energy of the battery 21 can be effectively used, and the battery 2
It is possible to achieve a longer usage time of 1.

Generally, in the converter, the conversion efficiency deteriorates as the input / output voltage difference increases. According to the present embodiment, the output voltage of the battery 21 is close to the output voltage of the step-up / down converter 22 applied to the power amplifier 23, so that the efficiency is also good.

FIG. 12 is a characteristic diagram of the conversion efficiency of the prototype buck-boost converter. FIG. 12 shows changes in conversion efficiency when the output voltage is fixed at 3.5 V, the output current is fixed at 142 mA, and the input voltage is changed from 2.5 V to 5 V. As can be seen from this efficiency characteristic, the efficiency of the buck-boost converter becomes good when the input and output voltages are close.

FIG. 13 shows the conversion efficiency characteristics when the input voltage is fixed at 3.5 V and the output power is fixed at 0.5 W and the output voltage is changed from 2.5 V to 4.5 V in the same buck-boost converter. It is a figure. As can be seen from FIG. 13, similarly, the smaller the voltage difference between input and output, the better the efficiency. Further, when the voltage difference between the input and output of the step-up / down converter 22 is within a predetermined voltage range, the battery 21 and the load 23 are directly connected to each other, so that the efficiency can be improved, so that the battery can be used for a longer time. .

(Fourth Embodiment) FIG. 14 is a circuit diagram showing a configuration of a battery-driven electronic device according to a fourth embodiment of the present invention. As shown in FIG. 14, the buck-boost converter 200 used in the battery-driven electronic device of the present embodiment is
The step-down converter unit including the first switching unit 221, the first rectification switching unit 222, and the inductor 223, and the inductor 223 are shared with the step-down converter unit, the second switching unit 224, and the second rectification switching unit. Means 225 and a boost converter section.

Further, the step-up / down converter 200 has a detection circuit 226, a first control drive circuit 227, and a second control drive circuit 228. The detection circuit 226 converts the voltage at the output capacitor 205 into a first voltage having a resistance value R1.
Detection resistance 261, a second detection resistance 262 having a resistance value R2, and a third detection resistance 263 having a resistance value R3.
It is detected by dividing by and compared with the reference voltage Eb output from the reference voltage source 260.

The error amplifier 264 includes a second detection resistor 26
2 and the third detection resistor 263 connection point voltage E1 = Eo.
R3 / (R1 + R2 + R3) and the reference voltage Eb are input, and the error signal is amplified and output as the first control signal Ve1. The error amplifier 265 includes the first detection resistor 26
1 and the second detection resistor 262 connection point voltage E2 = Eo ·
(R2 + R3) / (R1 + R2 + R3) and reference voltage Eb
Are input, and the error signal is amplified and output as the second control signal Ve2. Here, the output capacitor 205
The first set value of the power supply voltage is Eo within the allowable range of the power supply voltage required to be supplied to the load 206 as the voltage of
h = Eb · (R1 + R2 + R3) / R3, and the second set value of the power supply voltage lower than the first set value is Eol = Eb
・ (R1 + R2 + R3) / (R2 + R3)

The first control drive circuit 227 periodically turns on / off the first switching means 221 with a duty ratio according to the first control signal Ve1. That is, the first
When the level of the first control signal Ve1 decreases, the control drive circuit 227 of the first control circuit 227 reduces the duty ratio of the first switching unit 221 and changes the voltage of the output capacitor 205 to E.
The first switching means 21 is on / off controlled so as to stabilize at oh = Eb · (R1 + R2 + R3) / R3.

The second control drive circuit 228 periodically turns on / off the second switching means 224 at a duty ratio according to the second control signal Ve2. That is, the second
When the level of the second control signal Ve2 is lowered, the control drive circuit 228 of Eol changes the voltage of the output capacitor 205 to Eol.
= Eb · (R1 + R2 + R3) / (R2 + R3) so that the second switching means 224 is turned on /
Turn off.

The operation of the battery-driven electronic device of the present embodiment configured as described above, and particularly the buck-boost converter 200 thereof, will be described below.

First, when the battery voltage Ei is higher than the first set value Eoh of the power supply voltage, in the step-down converter section, the first control drive circuit 227 adjusts the voltage Eo of the output capacitor 205 to Eoh. Then, the first switching means 221 is turned on / off. Therefore, the voltage Eo becomes higher than the second set value Eol, and the detection circuit 226 lowers the second control signal Ve2 to the “L” level. In the boost converter section, the second control signal Ve2 is at the “L” level, so the second control drive circuit 228
Fixes the second switching means 224 at 0% duty ratio, that is, in the off state. Therefore, the step-up / down converter 200 includes the first switching means 221 and the first rectification switching means 2 that is turned on / off accordingly.
22 accumulates and releases magnetic energy to and from the inductor 223, so that the output capacitor 205 to the load 206 via the second rectification switching means 225.
It operates as a step-down converter that supplies the power supply voltage Eoh to the.

When the battery voltage Ei drops and falls below the first set value Eoh of the power supply voltage, the detection circuit 2
At 26, the first control signal Ve1 is raised to the "H" level. Therefore, in the step-down converter unit, the first control drive circuit 227 causes the first switching means 221 to operate.
Is fixed at 100% duty ratio, that is, in the ON state. However, when the battery voltage Ei is higher than the second set value Eol of the power supply voltage, the 0% duty ratio operation in the boost converter unit does not change. Therefore, the battery voltage Ei passes through the first switching means 221, the inductor 223, and the second rectification switching means 225, and the output capacitor 20.
Directly connected to 5. Assuming that the voltage drop in each component can be ignored, Eo = Ei.

When the battery voltage Ei further decreases and falls below the second set value Eol of the power supply voltage, the detection circuit 2
At 26, the second control signal Ve2 rises from the "L" level. In the boost converter section, the second control drive circuit 228 turns on / off the second switching means 224 so that the voltage Eo of the output capacitor 205 is adjusted to the second set value Eol. On the other hand, the 100% duty ratio operation in the step-down converter unit does not change. Therefore,
The buck-boost converter 200 includes the second switching unit 2
24 and a second rectifying / switching means 225 that performs on / off operation accordingly store and release magnetic energy with respect to the inductor 223 to supply the power supply voltage Eol from the output capacitor 205 to the load 206. Operates as a converter.

As described above, according to the present embodiment, within the allowable range of the power supply voltage supplied to the load 206, the first set value Eoh of the power supply voltage and the power supply voltage lower than the first set value Eoh are set. When the second set value Eol is set and the battery voltage Ei is Eol <Ei <Eoh, the buck-boost converter 200 interposed between the battery 201 and the load 206.
However, a direct connection can be made. In such a direct connection state, none of the switching means perform a switching operation, and thus a highly efficient characteristic that switching loss does not occur is exhibited. As described above, if the efficiency of the buck-boost converter 200 is improved, the battery usage time can be extended.

Incidentally, in FIG. 14, the first rectification switching means 222 and the second rectification switching means 225 are used.
Although a diode is used as the above, a synchronous rectification switching unit using a switching unit represented by a MOSFET or the like may be used in order to reduce the ON voltage at the time of conduction and reduce the conduction loss.

(Fifth Embodiment) FIG. 15 is a circuit diagram showing a configuration of a battery-driven electronic device according to a fifth embodiment of the present invention. In this embodiment, in order to further improve the effect of the fourth embodiment shown in FIG. 14, constituent elements are added to the fourth embodiment. 15 is different from FIG. 14 in that the first switching means 22 is different.
1 and the third switching means 2 across the inductor 223
29, and the first control signal Ve1 is at a level that fixes the first switching means 221 in the ON state, and the second control signal Ve2 is the second switching means 22.
When it is at a level that locks 4 in the off state,
The third control drive circuit 290 for turning on the switching means 229 is added.

The operation of the battery-driven electronic device of the present embodiment having the above-described structure, particularly the buck-boost converter 200, will be described below.

First, when the step-up / down converter 200 operates as a step-down converter or a step-up converter, the third switching means 229 is in the off state and does not participate in the operation.

When the battery voltage Ei is Eol <Ei <Eoh, the battery voltage Ei is the first switching means 221,
It is similar to the fourth embodiment in that it is directly connected to the output capacitor 205 via the inductor 223 and the second rectifying / switching means 225. In addition, the first control signal Ve1 is at a level that fixes the first switching means 221 in the ON state, and the second control signal V1
Since e2 is at a level that fixes the second switching means 224 in the off state, the third switching means 229 is in the on state.

In the description of the fourth embodiment, it is assumed that the voltage drop in each constituent element can be ignored, but in reality, each switching means has an ON voltage generated at conduction, and
A voltage drop occurs due to the direct current resistance of the inductor 223, and these become conduction losses. On the other hand, in the case of the present embodiment, the first switching means 221 and the inductor 2
Third switching means 22 connected in parallel with 23
Since 9 is turned on, such conduction loss is further reduced, and the buck-boost converter 200 can be made highly efficient.

Note that the third switching means 229 may be connected across the second rectification switching means 225 and the inductor 223 instead of the first switching means 221. The connection may be made by comparing the conduction loss of the first switching means 221 and the conduction loss of the second rectification switching means 225 so that a larger conduction loss can be covered.

Further, the third switching means 229 is
A configuration in which the first switching means 221, the inductor 223, and the second rectification switching means 225 are connected to each other is naturally conceivable. However, the buck-boost converter 200 operates as both a step-down converter and a step-up converter. In this case, the third switching means 229 is a switching means that can control ON / OFF in the OFF state regardless of whether the voltage difference between the input terminal and the output terminal is positive or negative, for example, a relay or two FETs whose body diodes are in opposite directions. Must be connected in series so that As a matter of course, it is preferable that the on-voltage is low from the use.

(Sixth Embodiment) FIG. 16 is a circuit diagram showing the structure of a battery-driven electronic device according to a sixth embodiment of the present invention. As shown in FIG. 16, the buck-boost converter 300 used in the battery-driven electronic device of the present embodiment is
First inductor 331 and switching means 332
, Coupling capacitor 333, and rectification switching means 3
35, the second inductor 334, and the output capacitor 3
05 and a control drive circuit 336.

The first inductor 331 and the switching means 332 form a series circuit and are connected to the battery 301,
The coupling capacitor 333 and the second inductor 334 form a series circuit and are connected to both ends of the switching means 332, and the rectification switching means 335 and the output capacitor 30 are connected.
5 forms a series circuit and is connected to both ends of the rectification switching means 335. The converter with such a configuration is Se
pic (Single EndedPrimary Inductive Converter)
It is a buck-boost converter called. Control drive circuit 33
6 has a function of controlling ON / OFF of the switching means 332 so that the voltage at the output capacitor 305 is adjusted to a predetermined value required to be supplied to the load 306.

The operation of the battery-driven electronic device of the present embodiment configured as described above, particularly the buck-boost converter Sepi
The operation of c will be described below. For ease of explanation, the capacitance of the coupling capacitor 333 is sufficiently large, and the coupling capacitor 333 is regarded as the voltage source of the voltage Ec.

First, when the switching means 332 is in the ON state, the battery voltage Ei is applied to the first inductor 331, the current flows from the battery 301 to the first inductor 331, and the magnetic energy is accumulated. At the same time, the second inductor 334 has a coupling capacitor 333.
Is applied to the second inductor 334, current flows from the coupling capacitor 333 to the second inductor 334, and magnetic energy is accumulated. The rectification switching means 335 is in the OFF state because the voltage is applied in the reverse direction, and the electrostatic energy stored in the output capacitor 305 is discharged and supplied to the load 306. This period is Ton.

Next, when the switching means 332 is turned off, the voltage of the first inductor 331 is inverted.
At the same time, the voltage of the second inductor 334 connected to the coupling capacitor 333 is also inverted. As a result, the rectification switching means 335 becomes conductive, and a current for charging the output capacitor 305 flows from the battery 301 via the first inductor 331, the coupling capacitor 333, and the rectification switching means 335. This current is applied to the first inductor 33
The magnetic energy stored in 1 is released. on the other hand,
The voltage Eo of the output capacitor 305 is applied to the second inductor 334, a current flows from the second inductor 334 to the output capacitor 305 via the rectification switching means 335, and the stored magnetic energy is released. This period is Toff.

By repeating the on / off operation as described above, the first inductor 331 and the second inductor 33 are
4, the accumulation and release of magnetic energy is repeated, and the coupling capacitor 333 and the output capacitor 305 are repeatedly charged and discharged. The condition for balancing the storage and release of these energy is that the currents flowing through the first inductor 331 and the second inductor 334 are balanced. Here, when the inductance of the first inductor 331 is L1, Ei · Ton / L1 = (Ec + Eo−Ei) · Toff
/ L1 holds, and the inductance of the second inductor 334 is L2, then Ec · Ton / L2 = Eo · Toff / L2 holds. By rearranging these equations, the relationship of Ec = Ei, Eo / Ei = Ton / Toff can be obtained. That is, the buck-boost converter Sepic
Can control the first switching means 332 to be turned on / off by the control drive circuit 336, so that the power supply voltage Eo to the load 306, which is the output voltage, can theoretically be adjusted to an arbitrary voltage.

Now, such a buck-boost converter Sep
The feature of ic is that since the first inductor 331 is provided in the input part of the converter, the input current can be kept in a continuous state with little fluctuation. Although detailed description is omitted, it is also known that the input current can be set to zero ripple by magnetically coupling the first inductor 331 and the second inductor 334 and adjusting the coupling coefficient. On the other hand, the characteristic of the battery 301 is that it is weak against a pulse-like sharply varying current, and tends to have a short life and a decrease in capacity. Therefore, according to the present embodiment,
By using Sepic, which has a small steep change in input current, as the buck-boost converter, the battery 3
It is possible to cover the demerits of the characteristics of No. 01 and suppress the shortening of the service life and prolong the usage time.

Although a diode is used as the rectification switching means 335 in FIG. 16, in order to reduce the on-voltage during conduction and reduce the conduction loss, the MOSFE is used.
A synchronous rectification switching means using a switching means represented by T may be used.

(Seventh Embodiment) FIG. 17 is a circuit diagram showing the structure of a battery-driven electronic device according to a seventh embodiment of the present invention. As shown in FIG. 17, the buck-boost converter used in the battery-powered electronic device of the present embodiment is 500.
Is a boost converter including a first switching unit 524, a first rectification switching unit 525, an inductor 523, and a first capacitor 504, and an intermediate voltage E1 which is an output voltage of the boost converter as an input,
It is composed of a second switching means 521, a second rectification switching means 522, a second inductor 526, and a step-down converter including a second capacitor 505.

In the boost converter, the first capacitor 5
The intermediate voltage at 24 is detected, and control is performed so as to stabilize it at a predetermined intermediate voltage E1. In the step-down converter, the voltage at the second capacitor 505 that becomes the output voltage Eo of the step-up / down converter 500 is detected. The control is performed so as to stabilize the voltage required for the load.

When the output voltage of battery 501 is higher than intermediate voltage E1, intermediate voltage E1 becomes a voltage close to the output voltage of battery 501 regardless of the boost converter. When the voltage of the battery 501 becomes lower than the intermediate voltage E1, the boost converter is controlled to stabilize the intermediate voltage E1.
The output voltage Eo supplied to the load is stabilized by the step-down converter.

The circuit configuration of this embodiment is different from that of the fourth embodiment in that in the fourth embodiment, the former stage is a step-down converter and the latter stage is a step-up converter, whereas in the present embodiment, the former stage is a step-up converter. The converter and the latter stage are the step-down converters. When the boost converter is in the latter stage as in the fourth embodiment, the current flowing to the output capacitor 205 of the step-up / down converter 200 shown in FIG. 14 is discontinuous, so that the ripple of the output voltage is reduced. Needs to increase the capacity of the output capacitor 205. For example, third generation CDMA (Code Division Multip
When a wireless access power amplifier of the le access type is used as a load, the ripple voltage of the power supply voltage causes distortion of the wireless transmission power amplifier, and therefore must be minimized. Also, when changing from voice mode to data transmission mode, the power for wireless transmission also changes close to the maximum, so it is necessary to change the power supply voltage, that is, the output voltage of the buck-boost converter from a small value to a large value. In order to make the length as long as possible, it is necessary to shift the power supply voltage quickly.

In order to reduce the ripple voltage of the power supply voltage, it is necessary to increase the output capacitor capacity 205. However, when this capacity is increased, the energy amount of the output capacitor increases, so that the power supply voltage is changed significantly. There is a conflicting problem that it takes time.

Therefore, as in the present embodiment, the step-up / step-down converter is configured so that the former stage is the step-up converter and the latter stage is the step-down converter, so that the latter-stage step-down converter has a continuous output current, so that the ripple voltage is reduced. It is possible to achieve both reduction of the output capacitor capacity.

The intermediate voltage E1 is the maximum output voltage required by the load 506, the voltage that can obtain this output at the maximum output current, that is, the resistance component between the first capacitor 504 and the second capacitor 505 and the maximum value. The voltage obtained by adding the maximum output voltage to the value obtained by multiplying the output current is set as the lower limit, and by setting a value close to this voltage, the second-stage step-down converter is efficient in that the second switching means 521 is always in the conducting state at this time. It becomes operable in the state.

In FIG. 17, the first rectification switching means 525 and the second rectification switching means 522 are used.
Although a diode is used as the above, a synchronous rectification switching unit using a switching unit represented by a MOSFET or the like may be used in order to reduce the ON voltage at the time of conduction and reduce the conduction loss.

(Eighth Embodiment) FIG. 18 shows a battery-powered electronic device according to any of the first to seventh embodiments of the present invention as a mobile communication device according to the eighth embodiment of the present invention. FIG. 3 is a block diagram showing a circuit configuration of a portable telephone to be used.

In FIG. 18, at the time of transmission, the data generated by the baseband unit 1803 is modulated by the modulation unit 1804, and the signal output from the modulation unit 1804 is the amplification unit 1.
The power is amplified to the required power in 805, and the transmission and reception separation circuit 1808
It is radiated from the antenna 1809 via the.

On the other hand, at the time of reception, the signal received by the antenna 1809 is amplified through the transmission / reception separation circuit 1808 to the required power in the reception circuit 1807, frequency converted if necessary, and demodulated into a baseband signal in the demodulation unit 1806. ,
It is input to the baseband unit 1803.

The step-up / down converter 1802 receives the output voltage of the battery 1801 as an input and supplies the power supply voltage to the amplification section 1805. The power supply voltage is changed according to the power output from the amplification section 1805, and the amplification section 1805 is changed. Is increasing the efficiency of.

In the fourth to seventh embodiments,
A capacitor may be inserted in parallel with the battery between the battery and the buck-boost converter. By inserting a capacitor, the ripple current of the buck-boost converter can be suppressed from flowing to the battery, so that the battery can be used for a long time. Also,
It is also possible to reduce the ripple voltage generated between the battery and the buck-boost converter.

[0126]

As described above, according to the present invention,
Compared to conventional lithium-ion batteries, the discharge capacity is large (energy density per unit volume or unit weight is high), but the battery voltage change rate of battery voltage is 0.2.
By combining a battery having characteristics such as a large value of 5 or more and a low average battery voltage with a buck-boost converter,
If the discharge characteristic of the battery is higher than the power supply voltage required by the load, the buck-boost converter will step down, and if the discharge characteristic of the battery is lower than the power supply voltage required by the load, the buck-boost converter will step up, The large discharge capacity (high energy density) of the battery can be effectively utilized, and the battery-driven electronic device and the mobile communication device can be used for a long time.

Further, the power supply voltage to the load is within the battery voltage change range of the battery due to the discharge of the battery, and further,
By adjusting the power supply voltage to the load to the average battery voltage associated with battery discharge, the buck-boost converter can be operated with higher efficiency, and the battery usage time of the battery-driven electronic device can be extended. Can be obtained.

When the power supply voltage to the load has a predetermined fluctuation range, all or part of the fluctuation range,
The whole or part of the battery voltage change range of the battery matches, and the power supply voltage required to be supplied to the load has a predetermined fluctuation range, and the required power supply voltage within the fluctuation range. Has a single peak value, and the required power supply voltage and the average battery voltage of the battery at the peak of this generation distribution are within a predetermined potential difference, the buck-boost converter can be operated with high efficiency. Therefore, there is an advantageous effect that the battery usage time of the battery-driven electronic device can be extended.

Further, according to the present invention, when the power supply voltage to the load and the output voltage of the battery are within a predetermined potential difference, the step-up / down converter has a function of fixing the active component interposed between the input and output to the ON state. By having the above, it is possible to obtain an advantageous effect that a highly efficient characteristic that switching loss does not occur and a battery use time of a battery-driven electronic device can be extended.

Further, since the buck-boost converter has a function of short-circuiting a part or all of the components interposed between the input and output thereof, when the power supply voltage to the load and the output voltage of the battery are within a predetermined potential difference. Has the advantageous effect that conduction loss can be reduced in addition to the occurrence of switching loss, efficiency can be further improved, and battery usage time of battery-powered electronic devices and mobile communication devices can be extended. can get.

Further, according to the present invention, by using Sepic as the buck-boost converter, the ripple component of the input current of the buck-boost converter can be reduced.
That is, since it is possible to reduce abrupt changes from the discharge current of the battery, it is possible to obtain the advantageous effects of preventing deterioration of the characteristics of the battery, suppressing the shortening of the life, and extending the operating time.

According to the present invention from another point of view, the combination of a step-up / down converter as a step-up / step-down converter and a step-down converter as a subsequent step can advantageously prolong the battery usage time, and in addition to the output ripple. Can be realized and the output voltage can be switched at high speed, which is optimal when a CDMA (Code Division Multiple Access) type wireless transmission power amplifier is used as a load.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing a schematic configuration of a battery-powered electronic device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing discharge characteristics of a battery and a power supply voltage supplied to a load in the first embodiment of the present invention.

FIG. 3 is a diagram showing a transition from a step-down operation (arrow D) to a step-up operation (arrow U) depending on the magnitude relationship between the discharge characteristic of the battery and the power supply voltage supplied to the load in the first embodiment of the present invention.

FIG. 4 is a cross-sectional view showing the structure of the evaluation coin cell battery according to the first embodiment of the present invention.

FIG. 5 is a sectional view showing the structure of a cylindrical battery according to the first embodiment of the present invention.

FIG. 6 is a diagram showing discharge characteristics in a combination of various active materials according to the first embodiment of the present invention.

FIG. 7 is a diagram showing changes with time in battery voltage due to charge / discharge of the battery in the first embodiment of the present invention.

FIG. 8 is a partial configuration diagram of a PDC type mobile communication device on which a battery-powered electronic device according to a second embodiment of the present invention is mounted.

FIG. 9 is a partial configuration diagram of a CDMA mobile communication device on which a battery-powered electronic device according to a third embodiment of the present invention is mounted.

FIG. 10 is a diagram showing a discharge characteristic of a battery and a voltage range required by a load in the mobile communication device of FIG.

FIG. 11A is a diagram showing the relationship between the output power of the power amplifier and the power supply voltage in the mobile communication device of FIG. 9.

FIG. 11B is a diagram showing output power of the power amplifier and its occurrence probability in the mobile communication device of FIG. 9;

12 is a characteristic diagram of conversion efficiency with respect to input voltage when the output voltage of the buck-boost converter in the mobile communication device of FIG. 9 is constant.

13 is a characteristic diagram of the conversion efficiency with respect to the output voltage when the input voltage of the buck-boost converter in the mobile communication device of FIG. 9 is constant.

FIG. 14 is a circuit diagram showing a configuration of a battery-powered electronic device according to a fourth embodiment of the present invention.

FIG. 15 is a circuit diagram showing a configuration of a battery-powered electronic device according to a fifth embodiment of the present invention.

FIG. 16 is a circuit diagram showing the configuration of a battery-powered electronic device according to a sixth embodiment of the present invention.

FIG. 17 is a circuit diagram showing a configuration of a battery-powered electronic device according to a seventh embodiment of the present invention.

FIG. 18 is a block diagram showing a circuit configuration of a mobile phone as a mobile communication device on which the battery-powered electronic device according to the first to seventh embodiments of the present invention is mounted.

FIG. 19 is a circuit diagram showing a configuration of a conventional battery-driven electronic device.

[Explanation of symbols]

1, 21, 201, 301, 501, 1801 Battery 2, 22, 200, 300, 500, 1802 Buck-boost converter 3, 206, 306, 506 Load 23 Power amplifier 24 Control means 221 First switching means 222 First Rectification switching means 223 Inductor 224 Second switching means 225 Second rectification switching means 226 Detection circuit 227 First control drive circuit 228 Second control drive circuit 229 Third switching means 290 Third control drive circuit 305 Second capacitor 331 first inductor 332 switching means 333 first capacitor 334 second inductor 335 rectification switching means 504 first capacitor 505 second capacitor 522 second rectification switching means 523 first inductor 524 1st switching means 525 1st rectification switching means 526 2nd inductor 527 1st control drive circuit 528 2nd control drive circuit 1803 baseband section 1804 modulation section 1805 amplification section 1806 demodulation section 1807 reception circuit 1808 transmission / reception separation Circuit 1809 Antenna

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasufumi Nakajima             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Yasuhiko Mito             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Shinji Kasamatsu             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Yoshiaki Nitta             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 5H029 AK03 AL01 AL11 AM06 HJ18                 5H030 AA00 AS11 BB21 FF44                 5H730 AA14 AS01 BB13 BB14 BB18                       BB57 DD32 EE02 EE07 EE23                       FD01 FG02                 5K067 AA43 BB04 EE02 KK05

Claims (20)

[Claims] 1. The voltage difference (Ec-Ed) is divided by the Ec, where Ec is the open circuit voltage after the rated charge cutoff voltage is reached and Ed is the open circuit voltage after the rated discharge cutoff voltage is reached. A battery having a discharge characteristic such that the rate of change of battery voltage is 0.25 or more, and an output voltage of the battery as an input source, and at least a step-down operation mode and a step-up operation mode are set according to the output voltage of the battery. A battery-driven electronic device comprising: a buck-boost converter that outputs a predetermined voltage and a load to which an output voltage of the buck-boost converter is supplied as a power supply voltage. 2. The voltage difference (Ec-Ed) is divided by the Ec, where Ec is the open circuit voltage after the rated charge cutoff voltage is reached and Ed is the open circuit voltage after the rated discharge cutoff voltage is reached. A battery having a discharge characteristic such that the rate of change of the battery voltage is 0.25 or more, and an output voltage of the battery as an input source, and a buck-boost operation mode is performed according to the output voltage of the battery to set a predetermined voltage. A battery-driven electronic device, comprising: a buck-boost converter that outputs a voltage; 3. The battery-powered electronic device according to claim 1, wherein the battery is a lithium secondary battery. 4. The battery is a prismatic battery, and the energy density per unit volume of the prismatic battery is 460 Wh / l.
It is above, The battery drive type electronic device of Claim 1 or 2 characterized by the above-mentioned. 5. The battery is a cylindrical battery, and the energy density per unit volume of the cylindrical battery is 530 Wh.
/ L or more, The battery-powered electronic device according to claim 1 or 2, characterized in that. 6. The battery according to claim 1, wherein the power supply voltage required to supply the load is within a range between the rated end-of-charge voltage and the rated end-of-discharge voltage of the battery. Driven electronic device. 7. The battery-driven electronic device according to claim 6, wherein the difference between the average battery voltage according to the discharge characteristics of the battery and the power supply voltage to the load is within a predetermined range. 8. The power supply voltage required to be supplied to the load has a predetermined fluctuation range, and all or part of the fluctuation range of the power supply voltage, the rated end-of-charge voltage of the battery and the rated voltage. The battery-driven electronic device according to claim 1 or 2, wherein the entire range of the end-of-discharge voltage or a part thereof matches. 9. The power supply voltage required to be supplied to the load has a predetermined fluctuation range, and the generation distribution of the required power supply voltage within the predetermined fluctuation range has one peak value. 9. The battery-driven electronic device according to claim 8, wherein the difference between the required power supply voltage and the average battery voltage due to the discharge characteristics of the battery at the peak of the distribution is within a predetermined range. 10. The battery-powered electronic device according to claim 1, wherein the load includes a power amplifier for wireless transmission. 11. A mobile communication device comprising the battery-driven electronic device according to claim 10 mounted on a tower. 12. The buck-boost converter has a function of fixing an active component interposed between its input and output to an on state when a difference between a power supply voltage to the load and an output voltage of the battery is within a predetermined range. The battery-powered electronic device according to claim 1, further comprising: 13. The step-up / down converter has a first switching means having one end connected to one end of the battery, and one end connected to the other end of the first switching means.
A first rectifying switching means having the other end connected to the other end of the battery; an inductor having one end connected to the other end of the first switching means; one end connected to the other end of the inductor; A second switching means having an end connected to the other end of the battery, and one end connected to one end of the second switching means,
A second rectification switching means having the other end connected to one end of the load; one end connected to one end of the load; the other end connected to the other end of the battery and the other end of the load; An output capacitor for supplying a power supply voltage, a power supply voltage at the output capacitor is detected, and an error signal between the detected power supply voltage and a first set value for performing the step-down operation mode is output as a first control signal. A detection circuit that outputs an error signal between the detected power supply voltage and a second set value for performing the boosting operation mode as a second control signal; and the power supply voltage according to the first control signal. Is the first
A first control drive circuit that controls ON / OFF of the first switching unit so that the power supply voltage is adjusted to the second set value.
13. The battery-powered electronic device according to claim 12, further comprising a second control drive circuit that controls ON / OFF of the second switching means so as to be adjusted to the set value of. 14. The detection circuit includes a series circuit of a first detection resistor, a second detection resistor, and a third detection resistor, to which the power supply voltage is applied, and a reference voltage source that outputs a reference voltage. A first error amplifier that receives the connection point potential between the first detection resistor and the second detection resistor and the reference voltage, and outputs the first control signal; and the second detection resistor. 14. The battery drive according to claim 13, further comprising: a second error amplifier that receives the connection point potential between the third detection resistor and the third detection resistor and the reference voltage and outputs the second control signal. Electronic device. 15. The buck-boost converter short-circuits some or all of the components interposed between its input and output when the difference between the power supply voltage to the load and the output voltage of the battery is within a predetermined range. The battery-powered electronic device according to claim 1, which has a function. 16. The step-up / down converter has a first switching means having one end connected to one end of the battery, and one end connected to the other end of the first switching means,
A first rectifying switching means having the other end connected to the other end of the battery; an inductor having one end connected to the other end of the first switching means; one end connected to the other end of the inductor; A second switching means having an end connected to the other end of the battery, and one end connected to one end of the first switching means,
Third switching means having the other end connected to the other end of the inductor, and one end connected to one end of the second switching means,
A second rectification switching means having the other end connected to one end of the load; one end connected to one end of the load; the other end connected to the other end of the battery and the other end of the load; An output capacitor for supplying a power supply voltage, a power supply voltage at the output capacitor is detected, and an error signal between the detected power supply voltage and a first set value for performing the step-down operation mode is output as a first control signal. A detection circuit that outputs an error signal between the detected power supply voltage and a second set value for performing the boosting operation mode as a second control signal; and the power supply voltage according to the first control signal. Is the first
A first control drive circuit that controls ON / OFF of the first switching unit so that the power supply voltage is adjusted to the second set value.
A second control drive circuit for controlling ON / OFF of the second switching means so as to be adjusted to a set value of, and a level at which the first control signal fixes the first switching means in an ON state. And a third control drive circuit for turning on the third switching means when the second control signal is at a level that fixes the second switching means in the off state. 16. The battery-powered electronic device according to claim 15. 17. The step-up / down converter has a first switching means having one end connected to one end of the battery, and one end connected to the other end of the first switching means,
A first rectifying switching means having the other end connected to the other end of the battery; an inductor having one end connected to the other end of the first switching means; one end connected to the other end of the inductor; A second switching means having an end connected to the other end of the battery, and one end connected to one end of the second switching means,
Second rectification switching means having the other end connected to one end of the load, and third switching having one end connected to one end of the inductor and the other end connected to the other end of the second rectification switching means. Means, one end of which is connected to one end of the load, the other end of which is connected to the other end of the battery and the other end of the load, and which supplies a power supply voltage to the load, and a power supply voltage at the output capacitor For outputting the error signal between the detected power supply voltage and the first set value for performing the step-down operation mode as a first control signal, and detecting the power supply voltage and the first set value for performing the step-up operation mode. A detection circuit that outputs an error signal with respect to the set value of 2 as a second control signal;
A first control drive circuit that controls ON / OFF of the first switching unit so that the power supply voltage is adjusted to the second set value.
A second control drive circuit for controlling ON / OFF of the second switching means so as to be adjusted to a set value of, and a level at which the first control signal fixes the first switching means in an ON state. And a third control drive circuit for turning on the third switching means when the second control signal is at a level that fixes the second switching means in the off state. 16. The battery-powered electronic device according to claim 15. 18. The buck-boost converter has a first inductor having one end connected to one end of the battery, one end connected to the other end of the first inductor, and the other end connected to the other end of the battery. Connected switching means, a coupling capacitor having one end connected to the other end of the first inductor, one end connected to the other end of the coupling capacitor, and the other end connected to the other end of the battery Two inductors, one end of which is connected to one end of the second inductor and the other end of which is connected to one end of the load, and one end of which is connected to one end of the load and which is the other end of the battery. An output capacitor connected to the other end and the other end of the load for supplying a power supply voltage to the load; and the switching for adjusting the power supply voltage to a predetermined value required to supply the load. On the stage /
3. The battery-driven electronic device according to claim 2, further comprising a control drive means for performing an off control. 19. The buck-boost converter has a first inductor having one end connected to one end of the battery, one end connected to the other end of the first inductor, and the other end connected to the other end of the battery. Connected switching means, first rectification switching means having one end connected to the other end of the first inductor, one end connected to the other end of the first rectification switching means, and the other end connected to the battery A first capacitor connected to the other end of the second switching means, one end of which is connected to the other end of the first rectification switching means, and one end of which is connected to the other end of the second switching means ,
Second rectification switching means having the other end connected to the other end of the battery, and a second inductor having one end connected to one end of the second rectification switching means and the other end connected to one end of the load. A second capacitor, one end of which is connected to one end of the load, the other end of which is connected to the other end of the battery and the other end of the load, and which supplies a power supply voltage to the load, and the first capacitor. Detecting an intermediate voltage of the output voltage and outputting an error signal between the detected intermediate voltage and an intermediate voltage setting value for performing the boosting operation mode as a first control signal
Second detection circuit for detecting a power supply voltage at the second capacitor, and outputting an error signal between the detected power supply voltage and a power supply voltage setting value for performing the step-down operation mode as a second control signal.
Of the detection circuit, and the intermediate voltage at the first capacitor is adjusted to the intermediate voltage set value according to the first control signal,
A first control drive circuit for controlling ON / OFF of the first switching means, and a power supply voltage of the second capacitor is adjusted to the power supply voltage set value according to the second control signal. ,
2. A battery-driven electronic device according to claim 1, further comprising a second control drive circuit for controlling ON / OFF of the second switching means. 20. The intermediate voltage set value is a maximum voltage required by the load, which is a voltage obtained by multiplying a resistance component between the first capacitor and the second capacitor by a maximum output current required by the load. 20. The battery-powered electronic device according to claim 19, wherein the voltage value is set to a value obtained by adding an output voltage.