JP2008131803A - Portable terminal device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid the casing temperature of a portable terminal device from becoming abnormally high, by preventing the temperature of a thermal diffusion sheet from becoming higher in temperature than is necessary, when diffusing the heat generated from a plurality of heat-generating components by using the thermal diffusion sheet. <P>SOLUTION: A power amplifier 10, a charge current control FET-A, and an auxiliary charge current control FET-B, respectively as a heat-generating component are mounted on a substrate 12. The power amplifier 10 and the charge current control FET-A are arranged, brought into contact with the thermal-diffusion sheet 13 or arranged close to the thermal-diffusion sheet across a slight space. The charge current control FET-B is arranged at a position planarly separated from the thermal-diffusion sheet 13. When the temperature of the thermal diffusion sheet 13, detected by a temperature sensor 9, is lower than a preset temperature, the charge current control FET-A is actuated. When the temperature of the thermal diffusion sheet 13, detected by the temperature sensor 9, exceeds a preset temperature, the auxiliary charge current control FET-B is actuated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cooling structure in a portable terminal device in which a substrate on which a component that generates heat during operation (a heat generating component) is mounted is mounted inside the housing, and in particular, heat generated from the heat generating component is transferred to a heat diffusion sheet. The present invention relates to a technique for radiating heat by thermally diffusing in the direction of the substrate surface.

  A mobile terminal device such as a mobile phone normally performs a predetermined operation using a secondary battery mounted in the mobile terminal as a power source. Therefore, when this portable terminal device is used, if the remaining capacity of the attached secondary battery is absent or low, it is necessary to charge the secondary battery. For this reason, a charging circuit is provided in the mobile terminal device for charging the connected secondary battery with a charging power supply circuit (AC adapter) (see, for example, Patent Document 1).

  FIG. 4 is a block diagram illustrating a configuration example of a conventional constant current charging type charging circuit that is supplied with constant voltage from the outside.

  In FIG. 4, a constant voltage current is supplied to a terminal 1 of the charging circuit from an external AC adapter (not shown) that converts a commercial AC power source into a predetermined DC voltage. The current input to the terminal 1 is supplied to the secondary battery 6 through the diode 2 for preventing backflow, the charging current control FET 3, and the current detector 4 to charge the secondary battery 6. The current detector 4 detects the charging current value during charging and outputs it to the charging control unit 7. Based on the charging current value detected by the current detector 4, the charging control unit 7 is used for charging current control so that the current flowing between the source and drain of the charging current control FET 3 becomes a predetermined constant current value. The gate voltage of the FET 3 is controlled.

  The charging voltage charged in the secondary battery 6 is supplied as an operation power supply to each functional circuit 5 in the terminal via the voltage detection circuit 8. The voltage detection circuit 8 detects a charging voltage value charged in the secondary battery 6 and outputs it to the charging control unit 7. The charging control unit 7 controls the charging current control FET 3 to be ON when the charging voltage of the secondary battery 6 is lower than the constant voltage set corresponding to the secondary battery 6, and is charged when the set constant voltage is reached. The current control FET 3 is controlled to be OFF. When the charging operation is performed, the charging current control FET 3 generates heat due to the drain current flowing through the charging current control FET 3.

  On the other hand, other components that easily generate heat are used for mobile phone terminals and the like, and it is a big problem to suppress the heat generated by these components and the surface temperature of the casing. Therefore, in order to suppress the heat generation of a small and thin portable device and average the amount of heat generation, a sheet-like “heat diffusion sheet” having a function of thermally diffusing in the surface direction is often used (for example, patent document) 2-3). In recent years, the material of the “thermal diffusion sheet” has been improved, and a polymer film is processed into a shape close to a single crystal by thermal decomposition, thereby having a thermal conductivity 1500 (W / mK) three times that of copper. "Diffusion sheet" has also been commercialized.

  FIG. 5 is a schematic view showing a conventional portable terminal device provided with a heat diffusion sheet that diffuses heat generated from such heat-generating components in the surface direction.

  In FIG. 5, a substrate 12 on which electrical components are mounted is disposed inside a housing 11 of the mobile terminal device. On the substrate 12, the transmission power amplification power amplifier 10 that generates the largest amount of heat, and the above-described charging device. Various circuit elements including the current control FET 3 are mounted. Further, a thermal diffusion sheet 13 is mounted between the housing 11 and the substrate 12 so as to be in contact with a part that generates a large amount of heat, such as the power amplifier 10 for transmission power amplification, the charging current control FET 3, or a small space. This thermal diffusion sheet 13 has an effect of suppressing the temperature rise of these components by diffusing local heat generated by heat generated during operation of the transmission power amplification power amplifier 10 and the charging current control FET 3 in the surface direction.

JP 2006-230080 A Japanese Patent Laid-Open No. 10-229287 JP 2006-019920 A

  In the case of the configuration shown in FIG. 5, each of the plurality of heat generating components (power amplifier 10 and charging current control FET 3) provided on the substrate 12 is thermally diffused using the heat diffusion sheet 13. Are operating at the same time, since both diffusion heats are added on the diffusion sheet 5, the heat dissipation by the diffusion sheet 5 is increased, and therefore the surface of the casing of the portable terminal device is likely to be hot, There was a problem of giving discomfort and anxiety to terminal users.

  In view of the above problems, the object of the present invention is that when the heat generated from a plurality of heat generating components provided on a substrate is thermally diffused using a heat diffusion sheet, the temperature of the heat diffusion sheet is abnormally high. It is to provide a means to prevent it.

  The present invention relates to a mobile terminal device in which a substrate on which a plurality of components that perform different functions are mounted is mounted inside a housing, and is in contact with a plurality of heat generating components that generate heat during operation among the plurality of components. A heat diffusion sheet that is arranged across a small space and diffuses heat generated from the plurality of heat generating components in the direction of the substrate surface, and the same component as the heat generating component selected in advance from the plurality of heat generating components. A spare heat-generating component mounted on the substrate at a position where the heat diffusion sheet is not disposed, temperature detection means for detecting the temperature of the heat diffusion sheet, and temperature detected by the temperature detection means And an operating component switching means for selecting and operating one of the selected heat generating component or the spare heat generating component.

  The operating component switching means selects and operates the selected heat generating component when the temperature detected by the temperature detecting means is lower than a preset temperature, and the temperature detected by the temperature detecting means is preset. When the temperature of the thermal diffusion sheet becomes higher than a preset temperature by selecting and operating the spare heat-generating component when the temperature is equal to or higher than the temperature, the number of components that are radiating heat by the thermal diffusion sheet The temperature of the heat diffusion sheet is controlled to be suppressed by reducing the temperature of the heat diffusion sheet, and when the temperature of the heat diffusion sheet is lower than the set temperature, the heat diffusion sheet is again placed in contact with or slightly sandwiched by the space. By selecting and operating a preselected heat-generating component, the heat generated by that component is sufficiently diffused by the heat diffusion sheet, and the component itself generates local heat and the housing is heated. There is to avoid that the partially hot.

  Further, when the plurality of heat generating components include a transmission power amplification power amplifier and a charging current control FET provided in a charging circuit for charging a secondary battery mounted on the portable terminal device, When the charge current control FET is provided as a spare heat generating component and the temperature of the heat diffusion sheet is higher than a preset temperature, the heat dissipation sheet dissipates heat by the heat diffusion sheet. By refraining from this, the heat radiation of the power amplifier for amplifying the transmission power is focused on, so that the temperature rise of the thermal diffusion sheet can be controlled to be kept low.

  In that case, it is preferable that the temperature detecting means is provided on the thermal diffusion sheet in the vicinity of the transmission power amplification power amplifier.

  According to the above configuration, it is possible to suppress the temperature on average both when the heat on the heat diffusion sheet is high and low, and to avoid the case surface temperature of the portable terminal device becoming abnormally high. Can do.

  According to the present invention, since the number of parts that are radiating heat by the heat diffusion sheet can be changed according to the temperature of the heat diffusion sheet, diffusion due to simultaneous operation of a plurality of heat generating parts on the heat diffusion sheet. By adding heat, it is possible to suppress the heat diffusion sheet itself from becoming abnormally high temperature, and it is possible to avoid the case surface temperature of the mobile terminal device from becoming abnormally high.

  In addition, when the temperature of the heat diffusion sheet is lower than a preset temperature, heat generated from all the heat generating components arranged in contact with the heat diffusion sheet or sandwiching a slight space is conducted to the heat diffusion sheet. Dissipating heat suppresses the temperature rise of all heat-generating components. In this case, the temperature of the heat diffusion sheet is lower than the preset temperature, so that the temperature of the device housing can be kept low, and the temperature of the device housing Has the effect of averaging.

  FIG. 1 is a block diagram illustrating a configuration example of a constant current charging type charging circuit used in the mobile terminal device of the present embodiment. FIG. 2 is a schematic view showing the portable terminal device of the present embodiment provided with a heat diffusion sheet that diffuses heat generated from the heat-generating component in the surface direction. 1 to 2, elements and blocks indicated by the same reference numerals as those in FIGS. 4 to 5 indicate elements and blocks having the same function.

  That is, the constant current charging type charging circuit used in the portable terminal device of the present embodiment is a charging current control FET-A (3-1) whose gate voltage is controlled by the charging control unit 7 as a charging current control FET. ) And FET-B (3-2) are provided in parallel, the temperature sensor 9 for detecting the temperature of the thermal diffusion sheet 13 is provided, and the charging controller 7 Depending on the temperature detected by the sensor 9, a control signal for controlling one of the two FETs, the charging current control FET-A (3-1) and the FET-B (3-2), to be turned on and the other to be turned off. Except for the point that the function to output is added, it is the same as the conventional constant current charging type charging circuit shown in FIG.

  The charging control unit 7 of the present embodiment has two charging current control FET-A (3-1) and FET-B (3-2) depending on the temperature of the thermal diffusion sheet 13 detected by the temperature sensor 9. A control voltage for controlling one of the FETs to be on and the other to be off is supplied to each gate terminal of the charging current control FET-A (3-1) and FET-B (3-2).

  Therefore, the charge control unit 7 includes the charge current control FET-A (3-1) and the FET-B (3) compared with the voltage or current value corresponding to the temperature of the thermal diffusion sheet 13 detected by the temperature sensor 9. -2) The voltage or current value data used as a reference for switching on and off of the two FETs is preset as threshold values and stored internally.

  Moreover, the constant current charge type charging circuit shown in FIG. 1 is mounted on the portable terminal device of the present embodiment. The temperature sensor 9 is mounted on the thermal diffusion sheet 13 and detects the temperature of the thermal diffusion sheet 13. The charging current control FET-A (3-1) is mounted at a position covered with the thermal diffusion sheet 13 on the substrate 12 and is placed in contact with the thermal diffusion sheet 13 or sandwiching a slight space. The control FET-B (3-2) is mounted on the substrate 12 at a position apart from the thermal diffusion sheet 13 in a plane where the thermal diffusion sheet is not disposed, and the charging current control FET-B (3-2) ) Is not conducted to the heat diffusion sheet 13.

  FIG. 3 is a flowchart showing the operation of the present embodiment. The operation of this embodiment will be described below with reference to FIGS. In the present embodiment, it is assumed that communication is performed while charging a secondary battery mounted on a mobile terminal device.

First, a storage unit (not shown) of the charging control unit 7 includes a reference for switching on and off of the two FETs, the charging current control FET-A (3-1) and the FET-B (3-2). The voltage or current value data is stored in advance as a temperature threshold value (threshold) _Tth , and can be read out in a timely manner (S1). Next, the charging control unit 7 detects the temperature data detected by the temperature sensor 9 by reading it in a timely manner (S2), and compares the detected temperature data T with the threshold value _Tth read from the storage unit ( S3).

When the detected temperature data T is less than the threshold value _Tth , the charging current control FET-A and FET- are set so that FET-A is active and FET-B is OFF (high impedance) (S4). The gate voltage of B is controlled, and the charging operation is performed by the charging current control FET-A (3-1) arranged in contact with the thermal diffusion sheet 13 or sandwiching a slight space.

On the other hand, when the detected temperature data T becomes equal to or greater than the threshold value _Tth , the charging current control FET is set so that the FET-A is turned off (high impedance) and the FET-B is activated (S5). -A and the gate voltage of FET-B are controlled, and charging operation is performed by the charging current control FET-B (3-2) not in contact with the thermal diffusion sheet 13. Thereafter, the operations of Step 2 to Step 5 are repeated to switch the operation FET by comparing the relationship between the detected change in the temperature data T and the threshold value _Tth .

  According to this embodiment, while charging the secondary battery mounted on the portable terminal device by the charging current control FET-A (3-1) arranged in contact with the thermal diffusion sheet 13 or sandwiching a slight space. When communication is performed, when the temperature of the thermal diffusion sheet 13 becomes equal to or higher than the set temperature, the charging current control FET-A (3-1) disposed in contact with the thermal diffusion sheet 13 or with a slight space interposed therebetween. ) Is switched to charging by the charging current control FET-B (3-2) arranged at a position away from the thermal diffusion sheet 13, so that the temperature increase of the thermal diffusion sheet 13 is suppressed.

  Thereafter, as the temperature of the charging current control FET-A (3-1) decreases, the temperature of the thermal diffusion sheet 13 also decreases, and when the temperature of the thermal diffusion sheet 13 becomes lower than the set temperature, it contacts the thermal diffusion sheet 13 again. Or since the operation | movement switched to charging operation by charging current control FET-A (3-1) arrange | positioned on both sides of slight space is repeated, charging current control FET-B arrange | positioned in the position away from the thermal diffusion sheet 13 The operation time of (3-2) can be set relatively short, and the charging current control FET-B due to the fact that the charging current control FET-B (3-2) is not subjected to the heat radiation action by the thermal diffusion sheet 13 (3-2) The temperature rise of itself can be suppressed small.

As described above, in this embodiment, when the temperature T of the thermal diffusion sheet 13 exceeds the predetermined threshold temperature _Tth , the FET-B (3-2) separated from the thermal diffusion sheet becomes active and the thermal diffusion is performed. Since the FET-A (3-1) on the sheet 13 is turned OFF and does not generate any more heat, only the heat generated by the power amplifier 10 is conducted to the heat diffusion sheet 13 and the FET-A from (3-1) is transmitted. Since heat is not added, the cooling efficiency of the power amplifier 10 is improved, the temperature on the heat diffusion sheet 13 can be suppressed, and the temperature of the apparatus housing can be suppressed.

When the temperature T is lower than the threshold temperature _Tth , the FET-A (3-1) on the thermal diffusion sheet 13 becomes active, and the heat of the FET-A (3-1) is conducted to the thermal diffusion sheet 13, Even when the charging current is large and the FET generates a lot of heat, there is an effect of diffusing to the thermal diffusion sheet 13 and averaging the temperature of the device casing.

  When the FET-B is switched from ON to OFF, the threshold temperature value when the FET-A is switched from ON to OFF is set so that the FET-A and FET-B are not frequently switched ON and OFF. By setting the value slightly higher than the threshold temperature value, it is possible to give hysteresis characteristics to the switching operation.

  In the above embodiment, the power amplifier 10 and the charging current control FET are described as parts that are disposed in contact with the thermal diffusion sheet 13 or sandwiching a slight space to diffuse heat generated during operation. The present invention can also be applied to the case where parts other than the above that need to diffuse the heat generated during operation are in contact with the heat diffusion sheet 13 or arranged with a slight space in between.

It is a block diagram which shows the structural example of the constant current charge type charging circuit used with the portable terminal device of this embodiment. It is the schematic which shows the portable terminal device of this embodiment provided with the thermal diffusion sheet which thermally diffuses the heat which generate | occur | produces from a heat-emitting component to a surface direction. It is a flowchart which shows operation | movement of this embodiment. It is a block diagram which shows the example of a structure of the conventional constant current charge type charging circuit supplied with constant voltage from the outside. It is the schematic which shows the conventional portable terminal device provided with the thermal diffusion sheet which thermally diffuses the heat | fever generate | occur | produced from a heat-emitting component to a surface direction.

Explanation of symbols

1 External constant voltage input terminal 2 Diode 3, 3-1, 3-2 Charging current control FET
4 Current Detector 5 Functional Circuits in Terminal 6 Secondary Battery 7 Charge Control Unit 8 Voltage Detection Circuit 9 Temperature Sensor 10 Power Amplifier 11 Housing 12 Substrate 13 Thermal Diffusion Sheet

Claims (5)

In a mobile terminal device in which a board on which a plurality of components that perform different functions are mounted is mounted inside the housing,
A thermal diffusion sheet that is disposed in contact with a plurality of heat generating components that generate heat during operation among the plurality of components or sandwiches a slight space, and that diffuses heat generated from the plurality of heat generating components in the direction of the substrate surface; ,
A spare heat-generating component that is the same as the heat-generating component selected in advance from the plurality of heat-generating components and is mounted on the substrate at a position where the heat diffusion sheet is not disposed,
Temperature detecting means for detecting the temperature of the thermal diffusion sheet;
In accordance with the temperature detected by the temperature detecting means, an operation component switching means for selecting and operating one of the selected heat generating component or the spare heat generating component;
A mobile terminal device comprising:   The operating component switching means selects and operates the selected heat generating component when the temperature detected by the temperature detecting means is lower than a preset temperature, and the temperature detected by the temperature detecting means is preset. The portable terminal device according to claim 1, wherein the portable terminal device has a function of selecting and operating the spare heat-generating component when the temperature is higher than a predetermined temperature.   The operating component switching means is a setting temperature for switching the operation from the selected heating component to the spare heating component, and a setting for switching the operation from the spare heating component to the selected heating component. The portable terminal device according to claim 1, wherein the switching function has a hysteresis characteristic by providing a certain difference in temperature.   The selected heat generating component is a charging current control FET provided in a charging circuit for charging a secondary battery mounted on the portable terminal device, and the drain-source between the drain-source of the charging current control FET The portable terminal device according to any one of claims 1 to 3, wherein a second charging current control FET whose sources are connected in parallel is provided as the spare heat-generating component.   The plurality of heat generating components include a transmission power amplification power amplifier, and the temperature detection means is provided on the thermal diffusion sheet in the vicinity of the transmission power amplification power amplifier. The mobile terminal device according to claim 4.

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