Electric power conversion apparatus and manufacturing method for the apparatus

The electric power conversion apparatus 110 according to the present invention comprises an electric power conversion module 150 for converting electric power from the commercial power supply 112 to converted electric power, a filler container 152 for accommodating said electric power conversion module 150, and a filler 154 with which said filler container 152 is filled, said filler having electric non-conductance and directly embracing said electric power conversion module 150, wherein the melting point of said filler 154 is equal to or lower than a temperature of said electric power conversion module 150 achieved by electric power conversion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a U.S. National Phase Application of International Application No. PCT/JP2008/063605 filed Jul. 29, 2008, which claims priority to Japanese Patent Application No. 2007-198161 filed Jul. 30, 2007, the disclosures of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to an electric power conversion apparatus for converting electric power from the commercial power supply to converted electric power and to a manufacturing method for the apparatus.

Today, it is known that an electric power conversion apparatus such as an AC adapter can convert electric power from the commercial power supply and transmit the converted electric power to an electronic device such as cell phone, Personal Handy phone System (PHS) or Personal Digital Assistant (PDA).

However, converting electric power from the commercial power supply causes a heat generation. In order to radiate the heat generated by an electric power conversion apparatus etc., a heat sink is used for broadening a radiation area which radiates the heat outside, as known in the art (See Patent Document 1, for example).Patent Document 1: Japan Laid Open Patent 1996-182324

However, when using such a heat sink of the prior art, it would be necessary to enlarge the heat sink in accordance with the increasing amount of heat generated by the electric power conversion. This leads to a problem that the size of the electric power conversion apparatus is too large.

The present invention attempts to solve the problem of the prior art. The object of the present invention is to provide a new electric power conversion apparatus and a manufacturing method for the apparatus. According to the invention, by forming a simple heat-absorbing structure using heat of fusion, the apparatus can control, without enlarging the size of the apparatus, the temperature rise caused by the increasing amount of heat generated by the electric power conversion.

In order to solve the above problems, according to an aspect of the present invention, an electric power conversion apparatus comprises: an electric power conversion module for converting electric power from the commercial power supply to converted electric power; a filler container for accommodating said electric power conversion module; and a filler with which said filler container is filled, said filler having electric non-conductance and directly embracing said electric power conversion module; wherein the melting point of said filler is equal to or lower than a temperature of said electric power conversion module achieved by electric power conversion.

The apparatus may further comprises: a temperature detector for detecting temperature of said filler; a controller for reducing output of electric power from said electric power conversion module when temperature detected by said temperature detector is equal to or higher than the melting point of said filler and is also higher than the first temperature which is equal to or lower than the boiling point.

Said controller may further restart the output of electric power when the temperature detected by said temperature detector is equal to or lower than the second temperature which is equal to or lower than the melting point of said filler, under the condition that the output of electric power is reduced.

Said controller may change the second temperature in accordance with voltage of a secondary battery to which the converted electric power is supplied, when the temperature detected by said temperature detector is higher than the first temperature.

Said electric power conversion module may be provided with frames for securing a volume of said filler which reaches every circuit on the main surface of said electric power conversion module.

The converted electric power may be electric power for charging a secondary battery.

In order to solve the above problems, according to another aspect of the present invention, a manufacturing method for an electric power conversion apparatus comprises: a step for creating a filler container; a step for accommodating by the filler container an electric power conversion module for converting electric power from the commercial power supply to converted electric power; a step for filling the filler container, which accommodates the electric power conversion module, with a filler having electric non-conductance; and a step for sealing the filler container.

EFFECTS OF THE INVENTION

As explained above, according to the present invention, by forming a simple heat-absorbing structure using heat of fusion, the electric power conversion apparatus can control, without enlarging the size of the apparatus, the temperature rise caused by the increasing amount of heat generated by the electric power conversion.

EXPLANATION OF REFERENCE NUMERALS

BEST MODE FOR CARRYING OUT THE INVENTION

The best embodiments for realizing the present invention will be explained in detail below with reference to the accompanying drawings. In the present description and drawings, the structural elements which have essentially the same functional structure are indicated by the same reference numerals in order to omit overlapping explanations.

It is preferable to give a higher capacity and a higher output voltage to a secondary battery such as a Lithium ion battery used in an electronic device such as a mobile terminal. However, in order to charge such a secondary battery more rapidly, a battery charger (electric power conversion apparatus) capable of charging the secondary battery with charging current of more than 10 C is needed, for example.

In the present embodiment, heat generated by such a large amount of charging current supplied to an electronic device is not only radiated into the air but also absorbed by a heat storage material of lower melting point. In this way, without enlarging the size of the electric power conversion apparatus, a large amount of charging current can be supplied to the secondary battery, and the volume of the electric power conversion apparatus can be reduced. In the following, in order to understand the present embodiment easily, the whole structure of an electric power supply system including an electric power conversion apparatus will be described initially. After that, features of the electric power conversion apparatus will be described in detail.

FIG. 1is a schematic perspective view of an electric power supply system100. The electric power supply system100comprises an electric power conversion apparatus110and a mobile terminal120.

The electric power conversion apparatus110receives AC 100 V power from the commercial power supply112. The supplied power may also be 100 to 240 V, for example, in accordance with a country. The apparatus110converts the received AC power to DC power and supplies the converted DC power, for example effective DC 5V, to the mobile terminal120. In the present embodiment the electric power conversion apparatus110is used for a battery charger for charging the secondary battery rapidly. However, the apparatus110may also be used for other things such as an AC adapter which can handle a sudden overload during a continuous power supply.

In the present embodiment, the electric power conversion apparatus110is an adapter which is directly connected to the commercial power supply112. However, the apparatus110may be replaced with other types of adapter, such as an adapter with a plug (socket) to be connected to the commercial power supply112, or a so-called cradle which fixes the mobile terminal120with a latch and supplies electric power to the fixed terminal120. In the present embodiment, the electric power conversion apparatus110is separated from the mobile terminal120, but the apparatus110may also be integrated into the mobile terminal120. The electric power conversion apparatus110can charge not only the mobile terminal120but also another object which needs electric power supply (an electric car which needs to be charged rapidly, for example).

The mobile terminal120may be not only the above-stated devices such as a cell phone, PHS and PDA, but also various portable electronic devices such as a note type personal computer. In the present embodiment, a cell phone is adopted for the mobile terminal120for easy understandings of the embodiment. The mobile terminal120is provided with a detachable secondary battery (not shown inFIG. 1) on the rear side of the operation unit122. The mobile terminal120has a connector124corresponding to the plug114extended from the electric power conversion apparatus110. The terminal120receives from the connector124electric power converted by the electric power conversion apparatus110and charges the secondary battery.

The secondary battery stores a partial amount of the converted power from electric power conversion apparatus110and, after the mobile terminal120is unconnected to the electric power conversion apparatus110, supplies power to each circuit in the mobile terminal120. For the secondary battery, a Lithium ion battery or a Nickel-Metal Hydride battery can be used typically.

The present embodiment is characterized that it encloses a phase transition material in the above-stated electric power conversion apparatus110and temporarily stores heat necessary for phase transition of the phase transition material. Accordingly, the phase transition material functions as a so-called heat buffer which carries out heat-absorption for a short time period only when a rapid heat-radiation is needed and carries out heat-radiation when a rapid heat-radiation is not needed.

FIG. 2is a schematic transparent view of an electric power conversion apparatus110. The electric power conversion apparatus110comprises an electric power conversion module150, a filler container152, a filler154, a temperature detector156, a voltage meter158a controller160and a housing162.

The electric power conversion module150converts electric power from the commercial power supply112into converted electric power with which the secondary battery of the mobile terminal120can be charged. The electric power conversion module150may be formed, as shown inFIG. 2, as a substrate on which circuits for electric power conversion are arranged, and the circuits on the substrate may be connected by any type of connecting means.

FIG. 3is a circuit diagram of the electric power conversion module150. In the electric power conversion module150, AC electric power input from a connection plug180is rectified by a rectifier182and further converted by a switching circuit184into a pulsed power with a desirable pulse width. The pulsed power is then transformed by a transformer186and rectified by a rectifier188into DC power. A constant current constant voltage control circuit190detects the rectified DC power and feeds it back to the switching circuit184so that a constant voltage and a constant current are output. A photo-coupler192is used, as well as the transformer186, to insulate the circuit190from the commercial power supply112. The output of electric power from the circuit190is supplied by way of the controller160to the secondary battery194. The functions of the controller160and the temperature detector156are explained later.

InFIG. 3, circuits illustrated by dotted lines generate heat when electric power is converted. The amount of heat generated is increased gradually in accordance with the increasing amount of current to be converted. So, when a larger amount of electric power is converted in order to shorten the charge time, the amount of heat generated is larger accordingly.

The filler container152accommodates the electric power conversion module150and is filled with the filler154. Then the electric power conversion module150and filler154are confined in the container152by sealing the container152.

The filler container152is made of synthetic resin. Since the synthetic resin can be processed easily and can be transformed though the filler154is accommodated therein, it can be transformed flexibly in accordance with transformation of the melting filler154. The container152may be made also of a natural material instead of the synthetic resin. In the case that the housing162has sufficient air tightness, the housing162can be regarded as the filler container152of the present embodiment.

The filler154has electric non-conductance and directly embraces the electric power conversion module150. When the filler container152is filled with a desirable amount of the filler154, the container152is sealed for example by thermo compression bonding.

When performing phase transition, the filler154can rapidly absorb heat generated by the electric power conversion module150. Since the volume of the filler154is changed little when it melts, if the heat-absorption is carried out by the filler154melting, the electric power conversion apparatus110can supply a large amount of current to the mobile terminal120without changing a shape and a usual volume of the apparatus110.

It is preferable that the melting point of the filler154is equal to or higher than an environmental temperature of the electric power conversion apparatus110, and is equal to or lower than a temperature of the electric power conversion module150achieved by electric power conversion.

Since the present embodiment uses heat of fusion, it is preferable that the melting point of the filler154is reached by heat generated when a large amount of current is supplied. Therefore, in order not to melt the filler154too early under the environmental temperature, the melting point of the filler154should be equal to or higher than the environmental temperature, and should further be equal to or lower than a temperature reachable by electric power conversion i.e. within the heat variation range. The reason why the melting point is defined by the environmental temperature is because the heat variation range of the melting point can be changed in accordance with an environment such as an air temperature dependent on country, region, indoor place and outdoor place.

In order to make the above-stated melting point to be equal to or higher than the environmental temperature of the electric power conversion apparatus110and further to be equal to or lower than a temperature of the electric power conversion module150reachable by electric power conversion, the melting point may be in the range from about 40 degrees centigrade to about 60 degrees centigrade, more preferably in the range from about 50 degrees centigrade to about 60 degrees centigrade. The melting point may also be equal to or higher than 60 degrees centigrade.

For universal use of the electric power conversion apparatus110, the melting point should be set to the temperature equal to or higher than 40 degrees centigrade, more preferably equal to or higher than 50 degrees centigrade, in order to avoid the dependence on region or season. Although each circuit in the electric power conversion module150has a 100 degrees centigrade or more heat tolerance generally, if the amount of generated heat were too large, the heat would be transmitted to the housing162and a user would have a feeling of wrongness when he/she touches the housing162. So, in the present embodiment, the melting point is set to 60 degrees centigrade, though an upper limit of the melting point may be greater than 60 degrees centigrade, in order to maintain a low temperature of outer surface of the electric power conversion apparatus110.

In the present embodiment, the filler154is alpha-olefin polymer which has a side-chain of crystalline. Alpha-olefin polymer has a melting point for example of 53 degrees centigrade, which is within the range of 40 to 60 degrees centigrade. Alpha-olefin polymer also has a narrow fusion temperature variation range at the amount of heat of fusion more than 100 J/g. That is to say, rapid heat-absorption can be carried out around the melting point.

Besides, since alpha-olefin polymer has a weight loss temperature equal to or higher than 300 degrees centigrade for example, it is not dissolved even if the temperature of the filler exceeds the melting point. Moreover, since the volume of alpha-olefin polymer is little changed regardless of its phase, solid or liquid, the filler container152can absorb the volume change even if the container152is small. Since alpha-olefin polymer can be dissolved in an inexpensive low-molecular-weight solvent such as toluene, methyl-cyclohexan or heptan, it is easy to wash the container152in the manufacturing process and it is possible to reduce the manufacturing costs. The filler154may also be, instead of alpha-olefin polymer, a phase transition material made of highly polymerized materials such as paraffin or plastic.

The volume of the filler154is determined so that at least one secondary battery194can be charged one time. For example, in the case of a recently proposed Titanium Lithium ion battery of 600 mAh, the amount of energy required for one hour charge is calculated as 5 V×6 A (with charging current of 10 C)×6 min×60 sec=10800 J. On the assumption that the efficiency of power conversion is 80%, the amount of energy loss is calculated as 10800/0.8×0.2=2700 J. So, the amount of heat generated per unit time is calculated as 2700 J/(6 min×60 sec)=7.5 W. As a result, in order to charge one secondary battery one time, it is preferable to set the heat storage capacity Q of the filler to be equal to or greater than 2700 J.

In the case of using alpha-olefin polymer stated above as the filler154, the amount of heat of fusion is equal to or more than 100 J/g, for example. Accordingly, in order to absorb energy loss of 2700 J, alpha-olefin polymer of 2700/100=27 g is required. Taking account of the specific gravity 0.9 g/cm3of alpha-olefin polymer, the volume of alpha-olefin polymer of 27/0.9=30 cm3is needed. This volume can be accommodated in a parallelepiped with the conventional size 4 by 4 by 2 centimeters. By using the filler154of such volume, the secondary battery194can be full charged. In the following, the temperature of the filler154caused by charging is explained.

FIG. 4is a time series chart illustrating the temperature of the filler154during a secondary battery charge. In the present embodiment, the battery is charged with a constant current and a constant voltage output by the constant current constant voltage control circuit190.FIG. 4shows voltage and current of the secondary battery194and temperature of the filler154in a normal one time charge.

For example, on the assumption that voltage of the secondary battery194is lowered to 3 V, voltage at the charge start timing is 3 V and is raised to 4.2 V when the battery is full-charged. The battery charge is continued until charging current is lowered to a predetermined value. Charging current at the charge start timing is 10 C, which is a constant current of 6 A. Joule heat generated by such charging current is absorbed by the filler154. Since the present embodiment uses the filler154with the melting point of 53 degrees centigrade, when temperature of the filler154reaches 53 degrees centigrade, this constant temperature is maintained. During this constant temperature, the filler154in the filler container152is in the melting condition (solid and liquid mixed condition). When the constant current condition is finished, charging current is decreased lower than 6 A, fusion of the filler154stops, and after a certain time, temperature is decreased, too.

The temperature detector156is provided on the electric power conversion module150and detects temperature (atmospheric temperature) of the filler154around it. The voltage meter158measures voltage of the secondary battery194.

The controller160is provided on the electric power conversion module150. The controller160reduces the output of electric power from the electric power conversion module when the temperature detected by the temperature detector156is equal to or higher than the melting point of the filler154and is also higher than the first temperature which is equal to or lower than the boiling point. The controller160further restarts the output of electric power when the temperature detected is equal to or lower than the second temperature which is equal to or lower than the melting point. In the present embodiment, a weight loss temperature of the filler is a high value 300 degrees centigrade and therefore it does not matter. However, if a weight loss temperature of the filler were a low value, it would be necessary to set the first temperature to be equal to or lower than the weight loss temperature in order not to dissolve the filler154.

FIG. 5is a time series chart illustrating the temperature variation of the filler154during another battery charge different from that ofFIG. 4. Also in the case ofFIG. 5, a constant current constant voltage charge is carried out by the constant current constant voltage control circuit190.FIG. 5shows, as well asFIG. 4, voltage and current of the secondary battery194and temperature of the filler154in a normal one time charge.

For example, assuming that, after the first charge is finished, the second charge starts for charging another secondary battery. Because of the first charge, at the first charge finish timing, the filler154is in the melting condition (solid and liquid mixed condition). When the second charge starts, the filler154further absorbs heat. Then, when all the solid filler is melted to be liquid i.e. when heat-absorption (heat storage) capacity of the filler154is saturated, temperature of the filler154restarts rising from the constant temperature of 53 degrees centigrade. When the temperature reaches the first temperature, for example of 100 degrees centigrade, the controller160stops (reduces) the charge. Then, because of a decrease of charging current, temperature of the filler154starts decreasing. When the temperature decreases back to the second temperature for example of 50 degrees centigrade, the controller160restarts the second charge.

When temperature of the filler154reaches the first temperature, in accordance with voltage of the another secondary battery measured by the voltage meter158(under the charging condition), the controller160may change a value to which the second temperature is set. For example, the controller160may set the second temperature to a high value (for example 70 degrees centigrade) in the case that voltage of the another secondary battery is equal to or higher than a prescribed value (nearly equal to a value of full-charged condition, for example) when temperature of the filler154reaches the first temperature. On the other hand, the controller160may also set the second temperature to a low value (for example 50 degrees centigrade) in the case that voltage of the another secondary battery is lower than the prescribed value. According to the above manner, in the case that voltage of the another secondary battery measured by the voltage meter158is equal to or higher than the prescribed value when temperature of the filler154reaches the first temperature, the battery charge restarts before temperature of the filler154is lowered. Therefore, the battery charge is carried out more rapidly, while the battery charge stops automatically when the another secondary battery is full charged. So, a rise of temperature of the filler154can be controlled preferably. Besides, in the case that voltage of the another secondary battery measured by the voltage meter158is lower than the prescribed value when temperature of the filler154reaches the first temperature, the battery charge restarts after temperature of the filler154is sufficiently lowered. So, a rise of temperature of the filler154can be controlled preferably also in this case.

If heat is continuously applied, by means of such two time charges, to the filler154even after the fusion of the filler154started, the filler154is completely melted to be liquid and temperature of the filler may reach the boiling point. At the boiling point, a volume change of 1,000 times is carried out, for example. If the filler container152and the housing162described later were structured to allow such a volume change, it would cost too much. Therefore, the present embodiment uses only fusion of the filler which causes little shape change, by reducing or stopping the output of electric power at the first temperature equal to or lower than the boiling point. Then, at the second temperature by which the filler154can be rapidly back to a solid phase which is capable of heat-absorption, the output of electric power is restarted. According to the above structure, heat generated by electric power conversion can be radiated safely and efficiently.

In the present embodiment, the first temperature is set to 100 degrees centigrade, which is higher than the melting point, 53 degrees centigrade, of the filler154. However, in the present embodiment, the first temperature is not confined to the above value but may also be set for example to 54 to 55 degrees centigrade, which is calculated by adding a margin a (1 to 2 degrees centigrade) to the melting point, 53 degrees centigrade, of the filler154. Because of this, temperature of the filler154is prevented from rising to a temperature equal to or more than the melting point. Therefore, a feeling of wrongness felt by a user when he/she touches the housing162is reduced.

The housing162formed of a resin such as plastic protects the filler container152which is filled with the filler154against external pressure. Since the resin such as plastic has a specific heat far smaller than those of metals, even when temperature of the electric power conversion module150inside becomes higher, heat is not so much transmitted to the outer face of the housing162. Accordingly, even when temperature of the filler154becomes 60 degrees centigrade, a user would not have so much feeling of wrongness when he/she touches the housing162.

(Manufacturing Method for the Electric Power Conversion Apparatus)

In the following, a manufacturing method for the electric power conversion apparatus110is explained.

FIG. 6is a flowchart illustrating the manufacturing method for the electric power conversion apparatus110. Initially, the filler container152to be enclosed in the electric power conversion module150is created (step S200).

FIGS. 7A to 7Dare schematic views illustrating a process for forming the filler container. As shown inFIG. 7A, on both sides of the aluminium film250, PET (Poly Ethylene Terephthalate) films252are laminated to make a laminating film254. The laminating film254is processed by compression molding using the die-and-mold256. Accordingly, the laminating film254is transformed by the compression molding to a box shown inFIG. 7B. This laminating film254becomes a part of the filler container152. In this embodiment, the laminating film254includes the aluminium film250but the film254may also include different existing materials.

As shown inFIG. 7C, the electric power conversion module150is accommodated by the created filler container152(step S202) with drawing only input and output lines258. From the top of the container152, it is filled with the filler154(step S204). Then the filler container152is covered by another laminating film260and sealed by thermo compression bonding of the film260in a vacuum to confine the filler154in the container152(step S206). The sealing can be carried out variously not only by thermo compression bonding but also by a sealing element such as an O-ring or by an adhesive agent. Then, as shown inFIG. 7D, the electric power conversion module150and the filler container152filled with the filler154are completed. Due to such sealing, even if the filler154is melted to be liquid, it is possible to reduce the risk that the filler154would be leaked outside from the filler container152.

Since the filler154has electric non-conductance, it does not electrically affect the electric power conversion module150and other electronic parts arranged in the filler container152, even if it is melted to be liquid.

Since the filler container152can be transformed freely, frames270may be prepared on the accommodated electric power conversion module150in order to maintain the form of the container152to some extent.

FIGS. 8 and 9are perspective views of the electric power conversion module150on which frames270are prepared. InFIG. 8, protrusions272of the frames270are directed toward each other. InFIG. 9, protrusions272of the frames270are directed radiantly from the electric power conversion module150. In both cases, the protrusions272support the filler container152by touching it. By preparing the frames270at the four corners of the electric power conversion module150, it is possible to maintain the parallelepiped shape of the filler container152even when external pressure is applied to the container152. Besides, because of the frames270, a certain space is formed over the main surface of the electric power conversion module150so that the filler154reaches every electronic parts on the electric power conversion module150.

Finally, input and output lines258are disposed appropriately and the filler container152is accommodated by the housing (step S208).

As explained above, according to the present embodiment, by means of a simple heat-absorbing structure using heat of fusion, a large amount of charging current can be supplied without changing a usual volume of the electric power conversion apparatus. Besides, in the case that the amount of charging current to be supplied is small, the size and weight of the electric power conversion apparatus can be reduced so that portability of the apparatus is improved.

For example, voltage of the secondary battery, which is the basis of control of the controller160, may be measured by the mobile terminal120, though it is measured by the voltage meter158of the electric power conversion apparatus110in the present embodiment.

Furthermore, each process in the manufacturing method for the electric power conversion apparatus described in the present description does not have to be performed in a chronological order according to the order described in the flow chart. The processes may also be performed in parallel or by a subroutine.

INDUSTRIAL APPLICATION OF THE INVENTION

The present invention can be applied to an electric power conversion apparatus for converting electric power from the commercial power supply to converted electric power and to a manufacturing method for the apparatus.