ELECTRONIC DEVICE AND SYSTEM

According to one embodiment, an electronic device includes a battery, a power supply circuit, and a charging circuit. The power supply circuit supplies power to components in the device by using DC power from an AC power supply or DC power from the battery. The charging circuit charges the battery by using the DC power from the AC power supply. The charging circuit includes a charger IC that controls a charging current and a charging voltage which are output from the charging circuit to the battery. The charger IC includes a first input terminal for monitoring a temperature of the AC power supply, and performs control for reducing the charging current when the temperature of the AC power supply exceeds a first temperature during the charging of the battery.

DETAILED DESCRIPTION

In general, according to one embodiment, an electronic device includes a battery, a power supply circuit, and a charging circuit. The power supply circuit supplies power to components in the electronic device by using DC power from an AC power supply or DC power from the battery. The charging circuit charges the battery by using the DC power from the AC power supply. The charging circuit includes a charger IC that controls a charging current and a charging voltage which are output from the charging circuit to the battery. The charger IC includes a first input terminal for monitoring a temperature of the AC power supply, and is configured to perform control for reducing the charging current when the temperature of the AC power supply exceeds a first temperature during the charging of the battery.

First, a configuration of an electronic device according to an embodiment will be described below with reference toFIG. 1. The electronic device may be implemented as, for example, a notebook type portable personal computer, a tablet terminal, or other various portable electronic devices. Hereinafter, a case where the electronic device is implemented as a notebook type portable personal computer10will be assumed.

FIG. 1is a perspective view viewed from the front side of the computer10in a state in which a display unit is opened. The computer10is configured to receive power from the battery20. The computer10is configured to supply power (operating power) to components inside the computer10by using power from the battery20or power from an AC power supply (AC adapter).

The computer10includes a computer main body11and a display unit12. The display unit12is provided with a display device such as a liquid crystal display (LCD)31. Furthermore, a camera (web camera)32is disposed in an upper portion of the display unit12.

The display unit12is attached to the computer main body11rotatably between an open position at which a top surface of the computer main body11is exposed and a closed position at which the top surface of the computer main body11is covered with the display unit12. The computer main body11includes a thin box-like housing and, on the top surface thereof, a keyboard13, a touch pad14, a fingerprint sensor15, a power switch16configured to turn on/off the power of the computer10, a plurality of function buttons17, and speakers18A and18B are disposed.

Also, a power connector (DC power input terminal)21is provided in the computer main body11. The power connector21is provided on a side of the computer main body11, for example, a left side thereof. An AC power supply is removably connected to the power connector21. As the AC power supply, an AC adapter may be used. The AC adapter is an AC power supply that converts commercial power (AC power) into DC power.

In the present embodiment, as the above-described AC power supply, a detachable AC adapter removably mounted into the computer10may be used. Rated current capacity required to the AC adapter for computer is relatively large. Therefore, in the past, it has been difficult to miniaturize the AC adapter for computer.

In recent years, the development of a high-speed switching element using a GaN chip has been in progress. The use of the high-speed switching element made of GaN makes it possible to miniaturize an inductor and a capacitor inside the AC adapter. By miniaturizing the inductor and the capacitor, a small-size AC adapter including sufficient rated current capacity may be realized.

In the present embodiment, as the above-described detachable AC adapter, a small-size AC adapter using a high-speed switching element made of GaN may be used. The detachable AC adapter may improve the portability of the computer10. This is because a user may carry the computer10in a state in which the detachable AC adapter is attached to the computer10, reducing the number of luggage to be carried. Furthermore, if necessary, the user may remove the detachable AC adapter from the computer10and carry the computer10alone. In this case, the weight of the computer10is reduced as much as that of the detachable AC adapter, improving the portability of the computer10. Furthermore, the detachable AC adapter may also contribute to efficient use of a work space on a desk. Moreover, like a general AC adapter, the detachable AC adapter may be connected to the power connector (DC power input terminal)21through a power cable. In this case, it is possible to suppress a temperature rise in the housing of the computer10due to heat generation of the detachable AC adapter.

The detachable AC adapter may be removably mounted on an AC adapter mounting portion25of the computer10. The AC adapter mounting portion25is implemented as, for example, an AC adapter slot into which the entire detachable AC adapter may be inserted. The AC adapter mounting portion25is provided on a side of the computer main body11, for example, a left side thereof. The AC adapter mounting portion25is disposed, for example, under the keyboard13. The AC adapter mounting portion25includes an opening on the left side of the computer main body11, and a space extending from the opening toward a central portion of the computer main body11. The space has a size enough to receive the detachable AC adapter. Also, instead of using the detachable AC adapter, an AC adapter built in the computer10(internal AC power supply) may be used.

The battery20is removably mounted on, for example, a rear portion of the computer main body11. The battery20may be a battery built in the computer10.

The computer10is driven by the power from the AC power supply (for example, the detachable AC adapter) or the power from the battery20. When the detachable AC adapter is mounted on the AC adapter mounting portion25, or when the detachable AC adapter is connected to the power connector21through the power cable, the computer10is driven by the power from the detachable AC adapter. Also, the power from the detachable AC adapter is also used to charge the battery20. During a period of time when the detachable AC adapter is not electrically connected to the computer10, the computer10is driven by the power from the battery20.

Furthermore, the computer main body11is provided with a plurality of USB ports22, a high-definition multimedia interface (HDMI) output terminal23, and an RGB port24.

FIG. 2illustrates a detachable AC adapter150. As illustrated inFIG. 2, the detachable AC adapter150includes a housing including a slim box shape. A power cable150A is derived from the front side of the housing of the detachable AC adapter150. A power plug is attached to a leading end of the power cable150A. Also, the power cable150A may be configured to be removably connected to a power connector of the detachable AC adapter150.

A receiving space of the AC adapter mounting portion25has a size enough to receive the entire detachable AC adapter150, and the detachable AC adapter150is mounted in the AC adapter mounting portion25such that the front surface thereof is flush with the left side of the computer main body11. A connector is provided on a rear side of the housing of the detachable AC adapter150. When the detachable AC adapter150is mounted in the AC adapter mounting portion25, the connector of the detachable AC adapter150is electrically connected to a power connector inside the AC adapter mounting portion25.

FIG. 3illustrates a case where the detachable AC adapter150is used as an external AC power supply. A power cable150B for DC power output may be connected to the detachable AC adapter150. A plug for DC power output is attached to the leading end of the power cable150B. Therefore, by connecting the plug for DC power output to the power terminal21of the computer10, the detachable AC adapter150may be used as the external AC power supply.

FIG. 4illustrates a system configuration of the computer10. The computer10includes a CPU111, a system controller112, a main memory113, a graphics processing unit (GPU)114, a sound codec115, a BIOS-ROM116, a hard disk drive (HDD)117, an optical disk drive (ODD)118, a BT (Bluetooth™) module120, a wireless LAN module121, an embedded controller/keyboard controller IC (EC/KBC)130, a system power supply circuit141, and a charging circuit142.

The CPU111is a processor that controls an operation of each component of the personal computer10. The CPU111executes various programs that are loaded from the HDD117on the main memory113. The programs include an operating system (OS)201and various application programs.

The CPU111also executes the basic input/output system (BIOS) stored in the BIOS-ROM116being a nonvolatile memory. The BIOS is a system program for hardware control.

The GPU114is a display controller that controls the LCD31used as a display monitor of the personal computer10. The GPU114generates a display signal (LVDS signal) to be supplied to the LCD31from display data stored in a video memory (VRAM)114A. Furthermore, the GPU114may generate an analog RGB signal and an HDMI video signal from the display data. The analog RGB signal is supplied to an external display through the RGB port24. The HDMI output terminal23may transmit an HDMI video signal (uncompressed digital video signal) and a digital audio signal to the external display through a cable. The HDMI control circuit119is an interface configured to transmit the HDMI video signal and the digital audio signal to the external device through the HDMI output terminal23.

The system controller112is a bridge device that connects the CPU111and each component. The system controller112is embedded with a serial ATA controller configured to control the hard disk drive (HDD)117and the optical disk drive (ODD)118. Also, devices such as the USB port22, the BT module120, the wireless LAN module121, the web camera32, and the fingerprint sensor15are connected to the system controller112.

The EC/KBC130is a power management controller configured to perform power management of the computer10. For example, the EC/KBC130is implemented as a one-chip microcomputer embedded with a keyboard controller that controls the keyboard (KB)13and the touch pad14, or the like. The EC/KBC130has a function of turning on and off the power of the computer10according to a user's manipulation of the power switch16. The power on/off control of the computer10is performed by a co-operation of the EC/KBC130and the system power supply circuit141.

The system power supply circuit141is a power supply circuit configured to supply the power (operating power Vcc) to each component in the computer10by using the power (DC power) from the battery20or the power (DC power) from the detachable AC adapter150. The power input terminal of the system power supply circuit141is connected to both the power connector21and the power connector160inside the AC adapter mounting portion25. Therefore, even in either of the case where the detachable AC adapter150is connected to the power terminal21through the power cable and the case where the detachable AC adapter150is mounted in the AC adapter mounting portion25, the system power supply circuit141may receive the power (DC power) from the detachable AC adapter150.

When an ON signal transmitted from the EC/KBC130is received, the system power supply circuit141supplies the operating power to each component in the computer10. Also, when an OFF signal transmitted from the EC/KBC130is received, the system power supply circuit141stop supplying the operating power to each component.

The EC/KBC130may communicate with each of the charging circuit142and the battery20through a serial bus. The charging circuit142is a circuit that charges the battery20by using the DC power from the detachable AC adapter150. The charging circuit142includes a charger IC143configured to control a charging current and a charging voltage which are output from the charging circuit142to the battery20. The charging current is a regulated output current of the charging circuit142and is used for charging the battery20. The charging voltage is a regulated output voltage of the charging circuit142and is also referred to as a battery voltage.

The EC/KBC130, the system power supply circuit141, the charging circuit142, and the charger IC143are operated even during a period of time when the power of the computer10is turned off.

Incidentally, when the detachable AC adapter150is in a state of being mounted in the AC adapter mounting portion25, an area of a contact region between the detachable AC adapter150and outside air is reduced. Therefore, since heat dissipation of the detachable AC adapter150does not proceed, it is likely that the temperature of the housing of the computer main body11will be raised by heat generation of the detachable AC adapter150.

As described above, the power from the detachable AC adapter150is used for not only driving the system load (system components) but also charging the battery20. Therefore, when the charging of the battery20is started, much current is drawn from the detachable AC adapter150. Hence, the temperature of the detachable AC adapter150easily rises. The heat generation of the detachable AC adapter150raises the temperature of the housing of the computer main body11, which may cause a risk of low-temperature burn.

In the present embodiment, the charger IC143is configured to include a feedback loop (temperature feedback loop) that automatically reduces the charging current according to the temperature of the detachable AC adapter150. That is, the charger IC143includes an input terminal (temperature monitoring pin) for monitoring the temperature of the detachable AC adapter150, and performs control for reducing the charging current when the temperature of the detachable AC adapter150exceeds a threshold temperature during the charging of the battery20. Since this may suppress the heat generation of the detachable AC adapter150, it is possible to reduce a risk of low-temperature burn caused by the temperature rise in the housing of the computer main body11.

It may be used a configuration that EC/KBC130monitors the temperature of the detachable AC adapter150and the firmware of the EC/KBC130instructs the charging circuit142or the charger143to reduce the charging current when the temperature of the detachable AC adapter150reaches the threshold temperature. However, when using this configuration, it is likely that the temperature of the detachable AC adapter150will exceed a temperature rating by response delay the EC/KBC130or hang-up of the EC/KBC130. If the control of the charging current by the firmware is early started by setting the threshold temperature to be low, the temperature of the detachable AC adapter150may be prevented from exceeding the temperature rating. However, in this case, even though the temperature of the detachable AC adapter150is within an allowable range, the charging current is reduced, that is, the charging current is excessively limited. Hence, it is likely that time necessary for charging the battery will be lengthened. In the present embodiment, since the charger IC143itself has the above-described temperature feedback loop, the control of automatically reducing the charging current may be rapidly performed. During a period of time when the temperature of the detachable AC adapter150is higher than the threshold temperature, the operation of charging the battery20is continued and the battery20is charged with the reduced charging current. During the charging of the battery20, when the temperature of the detachable AC adapter150is reduced to below the above-described threshold temperature, or is reduced to below another threshold temperature lower than the above-described threshold temperature, the charging current of the battery20is returned to the original value.

Therefore, the present embodiment can prevent the temperature of the detachable AC adapter150from exceeding the rated temperature, without excessive charging current limitation.

Also, the charger IC143may be configured to enable the above-described control of reducing the charging current only when the detachable AC adapter150is mounted on the computer10, and to disable the above-described control of reducing the charging current only when the detachable AC adapter150is connected to the power connector21of the computer10through the power cable. This configuration may be easily implemented by electrically connecting the temperature monitoring pin of the IC143to only the temperature terminal inside the power connector160.

FIG. 5illustrates a configuration of a power subsystem of the computer10.

The detachable AC adapter150includes a temperature sensor151. The temperature sensor151detects the temperature inside the detachable AC adapter150. The temperature sensor151may be implemented by a thermistor. The detachable AC adapter150includes a positive (+) terminal152A, a negative (−) terminal152B, and a temperature terminal152C.

When the detachable AC adapter150is connected to the power connector21of the computer10through the power cable, the positive (+) terminal152A and the negative (−) terminal152B of the detachable AC adapter150are connected to the power connector21through the power cable. The power cable does not include a signal line connected to the temperature terminal152C. Therefore, the temperature terminal152C is not connected to the power connector21. DC power from the positive (+) terminal152A of the detachable AC adapter150is supplied to the above-described system power supply circuit141through the power connector21. The system power supply circuit141supplies the power to the system load10A. The system load10A is each component inside the computer10.

The power connector160inside the AC adapter mounting portion25includes three terminals electrically connected to, respectively, the positive (+) terminal152A, the negative (−) terminal152B, and the temperature terminal152C of the detachable AC adapter150. When the AC adapter150is mounted in the AC adapter mounting portion25of the computer10, the DC power from the positive (+) terminal152A of the detachable AC adapter150is supplied to the above-described system power supply circuit141through the power connector160. Also, the temperature monitoring pin of the charger IC143is connected to the temperature terminal152C of the detachable AC adapter150through the power connector160of the AC adapter mounting portion25to receive the signal representing the temperature of the detachable AC adapter150from the detachable AC adapter150.

FIG. 6illustrates a configuration of the charging circuit142including the charger IC143.

The charging circuit142is implemented as, for example, a synchronous rectification type switching power supply. A high-side FET301and a low-side FET302are connected in series between a power input terminal VIN connected to the positive (+) terminal152A of the detachable AC adapter150and a ground terminal. An inductor303and a capacitor305constitute a smoothing circuit. A resistor304for current sense is inserted between the inductor303and the capacitor305.

The charger IC143functions as a DC/DC converter configured to control the charging current and the charging voltage by controlling on-duty ratio of the high-side FET301being a switching element.

The charger IC143includes a high-side FET driver block311, a low-side FET driver block312, a driver logic unit313, a pulse width modulation (PWM) generation unit314, a current feedback unit315, a voltage feedback unit316, and a temperature feedback unit317. The high-side FET driver block311controls the switching of the high-side FET301according to a switch control signal S1from the driver logic unit313. The low-side FET driver block312controls the switching of the low-side FET302according to a switch control signal S2from the driver logic unit313. The switch control signal S2is a complementary signal obtained by inverting the switch control signal S1. The low-side FET302maintains an on state while the high-side FET301is in an off state. Therefore, the low-side FET302functions as a synchronous rectifier (synchronous rectifying diode).

The driver logic unit313generates the above-described switch control signals S1and S2according to the PWM signal from the PWM generation unit314. The PWM generation unit314includes a comparator314A. The comparator314A compares a triangular-wave reference signal with a control signal, and generates a PWM signal whose on-duty duration is duration where a voltage of the triangular-wave is higher than a voltage of the control signal. Therefore, a length of the on duty duration of the PWM signal, that is, a ratio (on duty ratio) of the on duration of the high-side FET301to the switching period, varies according to the voltage of the control signal. In order to generate the control signal, the current feedback unit315, the voltage feedback unit316, and the temperature feedback unit317are used.

The current feedback unit315includes two input terminals P1and P2for monitoring the charging current. The input terminal P1is connected to a positive-side terminal of the current-sense resistor304, and the input terminal P2is connected to a negative-side terminal of the current-sense resistor304. An error amplifier315A inside the current feedback unit315controls the voltage of the above-described control signal such that the charging current becomes constant. The current feedback unit315and the PWM generation unit314function as a current feedback loop that monitors the charging current and controls the switching of the switching element (high-side FET301) according to the charging current. When this current feedback loop is dominant over other feedback loops, the control of the charging current is performed for constant current charging at the constant current by the current feedback loop.

The voltage feedback unit316includes an input terminal P3for monitoring the charging voltage (battery voltage). The input terminal P3is connected to a node between the current-sense resistor304and the capacitor305. An error amplifier316A inside the voltage feedback unit316controls the voltage of the above-described control signal such that the charging voltage (battery voltage) is matched with a reference voltage. The voltage feedback unit316and the PWM generation unit314function as a voltage feedback loop that monitors the charging voltage (battery voltage) and controls the switching of the switching element (high-side FET301) according to the charging voltage (battery voltage). When this voltage feedback loop is dominant over other feedback loops, the control of the charging voltage (battery voltage) is performed for constant voltage charging at the constant voltage by the voltage feedback loop. In other words, the charging current is controlled such that the regulated charging voltage (battery voltage) is obtained.

The temperature feedback unit317includes an input terminal P4for monitoring the temperature of the detachable AC adapter150. The input terminal P4is connected to the temperature terminal152C of the detachable AC adapter150through the AC adapter mounting portion25. An error amplifier317A inside the temperature feedback unit317controls the voltage of the control signal such that the charging current is reduced when the temperature of the detachable AC adapter150exceeds the threshold temperature. The temperature feedback unit317and the PWM generation unit314function as a temperature feedback loop that performs control for reducing the charging current being currently used in the constant current charging or the constant voltage charging when the temperature of the detachable AC adapter150exceeds the threshold temperature. During a period of time when the temperature of the detachable AC adapter150exceeds the threshold temperature, the temperature feedback loop is dominant over other feedback loops. For example, during the period of time when the temperature exceeds the threshold temperature, the output voltage of the temperature feedback unit317may be set to be higher than the output voltage ranges of other feedback units315and316.

A case where the temperature of the detachable AC adapter150is equal to or lower than the threshold temperature will be assumed. In this case, the output voltage of the temperature feedback unit317is almost zero. Also, until the charging voltage (battery voltage) reaches a certain voltage, the output voltage of the voltage feedback unit316is also almost zero. Therefore, until the charging voltage (battery voltage) reaches the certain voltage, the control signal is controlled by only the output voltage of the current feedback unit315. Therefore, the charger IC143controls the switching of the high-side FET by using the current feedback unit315such that the charging current becomes constant, and charges the battery20in a constant current charging mode.

A feedback unit for controlling the control signal transitions from the current feedback unit315to the voltage feedback unit316when the charging voltage (battery voltage) reaches the certain voltage. For example, the output voltage of the voltage feedback unit316may be set to be higher than the output voltage range of the current feedback unit315. Therefore, after the charging voltage (battery voltage) reaches the certain voltage, the control signal may be controlled by only the output voltage of the voltage feedback unit316.

Next, a case where the temperature of the detachable AC adapter150exceeds the threshold temperature will be assumed. When the temperature of the detachable AC adapter150exceeds the threshold temperature, the voltage of the control signal is raised by the output voltage of the temperature feedback unit317. Therefore, the on duty ratio of the high-side FET301is lowered, and the charging current is reduced.

As described above, in the present embodiment, when the temperature of the detachable AC adapter150exceeds the threshold temperature, the current supplied to the system load10A is not limited, but the charging current of the battery20is reduced. Therefore, the temperature rise in the detachable AC adapter150may be suppressed without affecting the operation of the system.

Also, when the temperature of the detachable AC adapter150exceeds a first threshold temperature, the charger IC143starts the control of reducing the charging current of the battery20. When the temperature of the detachable AC adapter150exceeds a second threshold temperature higher than the first threshold temperature, the EC/KBC130may start processing of lowering the operating speed of the CPU111or other devices.

Also, the connection relationship between the feedback units315to317and the PWM generation unit314described above with reference toFIG. 6is exemplary. It is possible to use an arbitrary configuration that may reduce the charging current by automatically lowering the on duty ratio of the high-side FET301when the temperature of the detachable AC adapter150exceeds the threshold temperature Th during the constant current charging or the constant voltage charging.

FIG. 7illustrates the operation of the charger IC143ofFIG. 6.

Herein, a case where the temperature of the detachable AC adapter150is equal to or lower than the threshold temperature Th will be assumed. The charger IC143charges the battery20with a certain constant charging current (I2) by using the current feedback loop configured to monitor and control the charging current (constant current charging). When the charging voltage (output voltage) reaches a certain threshold voltage (V2) (timing to ofFIG. 7), the charger IC143charges the battery20with a certain constant voltage (V2) by using the voltage feedback loop configured to monitor and control the charging voltage (constant voltage charging). When the battery20becomes a fully charged state, for example, when the charging current is lowered to the charging stop current, the charging of the battery20is ended.

FIG. 8illustrates the operation of the temperature feedback loop of the charger IC143.

Herein, a case where the temperature of the detachable AC adapter150exceeds the threshold temperature Th during the constant current charging will be assumed. The charger IC143charges the battery20with a certain constant charging current (I2) by using the current feedback loop configured to monitor and control the charging current (constant current charging). When the temperature of the detachable AC adapter150exceeds the threshold temperature Th (timing t1ofFIG. 8), the charging current is reduced. After the charging current is reduced, when the temperature of the detachable AC adapter150is lowered to below the threshold temperature Th (timing t2ofFIG. 8), the control for reducing the charging current is stopped, and the charging current is returned to the original charging current (I2).

Also, although the case where the temperature of the detachable AC adapter150exceeds the threshold temperature Th during the constant current charging has been exemplified, the control for reducing the charging current of being used during the constant voltage charging is also performed in the case where the temperature of the detachable AC adapter150exceeds the threshold temperature Th during the constant voltage charging. When the temperature of the detachable AC adapter150is lowered to below the threshold voltage Th, the control for reducing the charging current is stopped, and the charging current is returned to the regulated original charging current.

FIG. 9illustrates another configuration of the power subsystem of the computer10.

InFIG. 9, the charger IC143is connected to the temperature terminal152C of the detachable AC adapter150in the case where the detachable AC adapter150is connected to the power connector21through the power cable as well as the case where the detachable AC adapter150is inserted into the AC adapter mounting portion25. Therefore, the above-described temperature feedback loop may be functioned in the case where the detachable AC adapter150is connected to the power connector21through the power cable as well as the case where the detachable AC adapter150is inserted into the AC adapter mounting portion25.

As described above, according to the present embodiment, the charger IC143includes the input terminal P4for monitoring the temperature of the detachable AC adapter150, and performs control for reducing the charging current when the temperature of the detachable AC adapter150exceeds the threshold temperature during the charging the battery20. Therefore, the temperature rise in the detachable AC adapter150may be suppressed.

Also, the temperature feedback loop of the charger IC143may be applied to the detachable AC adapter150, may be applied to the conventional external AC adapter, and may also be applied to the internal AC adapter.