BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an energy storage device, and more particularly to an energy storage device with functions of electric quantity storage, AC and DC charging, electric quantity detection, and DC boost output, which is applicable for AC and DC bidirectional charging. 
         [0003]    2. Related Art 
         [0004]    Recently, in the common technical field of portable energy storage devices (i.e., POWERBANK), a built-in electrical core is usually taken as an energy storage device. The electrical core is charged by a special charger to store electric energy, and in usage, the electrical core outputs the electric energy. After being boosted by a boost circuit, the output voltage is raised to 5V, so as to supply power to an external device. The energy storage device in the prior art still has defects, that is, the energy storage device in the prior art can only charge the built-in electrical core in a manner of supplying with a DC current. Therefore, if a failure occurs to the configured charger or no special charge adapter is available, the energy storage device cannot be charged. Meanwhile, it is inconvenient for a user to take along a fitted charger or charge adapter when going out. The energy storage device in the prior art does not have an electric quantity detection function, so that the user cannot figure out the remaining electric quantity before going out, which is rather inconvenient. The energy storage device in the prior art cannot be discharged when being charged, cannot be charged when being discharged, and cannot be discharged through a USB port, which lacks of flexibility in usage. 
       SUMMARY OF THE INVENTION 
       [0005]    In view of the above defect in the prior art that the portable energy storage device can merely be charged with a DC current, the present invention is directed to a novel portable energy storage device, which is connected to a buck circuit, an AC/DC conversion circuit, and a regulator circuit at an input interface. A high-voltage commercial AC current is converted into a low-voltage DC current, and then regulated by the regulator circuit, and then used to charge an electrical core in the present invention, so that the portable energy storage device of the present invention can be charged with either an AC current or a DC current. 
         [0006]    A control unit in the present invention is further connected to a light-emitting diode (LED) for indicating the remaining electric quantity in the electrical core of the present invention, so as to solve the problem in the prior art that the portable energy storage device cannot indicate the electric quantity in the electrical core. The present invention is further configured with an input USB port connected to a charging management unit, so that the present invention is charged through the USB port. The present invention is further configured with an output USB port connected to a powering interface in parallel, so that the power is output through the USB port. 
         [0007]    The technical solution provided in the present invention for solving the technical problem is described as follows. A multifunctional portable energy storage device is provided, which includes an electrical core, a charging interface, and a powering interface. An external power supply charges the electrical core through the charging interface, and the electrical core supplies power to an external device through the powering interface. The energy storage device further includes an AC/DC converter, a control unit, and a charging management unit. The charging interface is connected to an input terminal of the AC/DC converter. An external AC current is converted into a DC current by the AC/DC converter and then input to the charging management unit. The charging management unit controls the DC current and supplies power to the electrical core. The electrical core supplies power to the external device through the powering interface. The control unit controls operations of the charging management unit. 
         [0008]    The technical solution provided in the present invention for solving the technical problem further includes the following aspects. 
         [0009]    The energy storage device further includes: an input USB port, connected to a power input terminal of the charging management unit and the powering interface respectively. 
         [0010]    The AC/DC converter includes a buck portion, an AC/DC conversion portion, and a regulator portion. The external AC current is bucked in voltage by the buck portion and input to the AC/DC conversion portion, then converted into the DC current by the AC/DC conversion portion and input to the regulator portion, such that a stable voltage is output to the charging management unit. 
         [0011]    The buck portion employs a resistance/capacitance (R/C) buck circuit. 
         [0012]    A data terminal of the control unit is connected to two or more LEDs for indicating electric quantity of the electrical core. 
         [0013]    A fuse is connected on a live wire of the charging interface in series. 
         [0014]    The energy storage device further includes: an output USB port, connected to the powering interface in parallel. 
         [0015]    A field effect transistor (FET) is respectively disposed between the input USB port and the powering interface and between the charging management unit and the powering interface, and a control terminal of each FET is respectively connected to the data terminal of the control unit. 
         [0016]    The efficacies of the present invention are listed as follows: the present invention has a simple structure and multiple functions, and can be charged with an external AC current, an external DC current, or charged by the computer through the USB port, which thus has various charging manners and is flexible in usage. The present invention is further configured with an electric quantity indicator, which enables the user to easily figure out the electric quantity of the electrical core in the present invention. The present invention is further configured with a battery over-discharge protection module and an output over-current protection module, for protecting the present invention from being damaged. The present invention can supply power to the external device through the powering interface or the USB port, thus having flexible supplying manners. 
         [0017]    The present invention is illustrated below in detail with reference to the accompanied figures and specific embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The present invention will become more fully understood from the detailed description given herein below for illustration only, and thus is not limitative of the present invention, and wherein: 
           [0019]      FIG. 1  is a block circuit diagram of the present invention. 
           [0020]      FIG. 2  is a circuit principle diagram of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    The following embodiment is merely a preferred embodiment of the present invention, others embodiments with principles and basic structures the same as or similar to this 
         [0022]    embodiment also fall within the scope sought to be protected by the present invention. Referring to  FIGS. 1 and 2 , the energy storage device of the present invention mainly includes an AC/DC converter, a control unit, a charging management unit, a charging interface, a powering interface, and an electrical core. The charging interface, the powering interface, and the electrical core are the same as those in the prior art. The electrical core is used as a storage element in the present invention for storing energy. The present invention supplies power in a form of a commercial AC current, and the commercial AC current is bucked in voltage by the buck portion and then input to the AC/DC conversion portion. In this embodiment, the buck portion employs an R/C buck circuit. A resistor RX 1  and a resistor RX 2  are connected between a neutral wire and a live wire in series, and are connected to a capacitor CX 1  in parallel. A resistor R 1  and an inductor L 1  are connected on the live wire in series. In the present invention, the commercial AC current is converted into a low-voltage AC current through the above circuit, and then input to the AC/DC conversion portion. In order to prevent the present invention from being damaged by a high-voltage pulse, in this embodiment, a voltage-sensitive resistor MOV 1  is connected between the neutral wire and the live wire in series, and a fuse F 1  is connected on the live wire in series for power input, so as to prevent the present invention from being damaged due to the over-current. The commercial AC current with the voltage bucked by the buck portion is converted into an approximately low-voltage DC by a bridge rectifier, input to an AC/DC chip U 1  to be converted into a DC current, and then output to the regulator portion. In this embodiment, the AC/DC chip U 1  employs a LD7535 chip. In this embodiment, the regulator portion is formed by an optical coupler U 2  and an adjustable regulated power supply U 3 . An LED and a zener diode ZD 1  in the optical coupler U 2  are connected between a positive pole of the power supply and the ground in series. A photosensitive triode in the optical coupler U 2  is connected to an FB pin in the AC/DC chip U 1 . A power output pin OUT of the AC/DC chip U 1  is connected to a control terminal of a field effect transistor Q 1 , and the field effect transistor Q 1  is connected between a SENSE pin of the AC/DC chip U 1  and the positive pole of the power supply. In this embodiment, the adjustable regulated power supply U 3  employs a 3-terminal adjustable shunt voltage regulator TL 431 . An adjustment control terminal of the adjustable regulated power supply U 3  is connected to a resistor R 31  and a resistor R 32  in series, so that an output voltage of the adjustable regulated power supply U 3  can be accurately adjusted and controlled by adjusting the resistor R 31  and the resistor R 32 . The adjustable regulated power supply U 3  outputs power to the charging management unit. In this embodiment, a core chip of the charging management unit employs a lithium battery charger circuit U 4 , and the lithium battery charger circuit U 4  employs a CN3052A chip. A positive power input terminal of the lithium battery charger circuit U 4  is connected to the positive pole of the power supply through a diode D 6  and a field effect transistor Q 2 A connected in series. A control terminal of the field effect transistor Q 2 A is connected between a resistor R 12  and a resistor R 13 , and the resistor R 12  and the resistor R 13  are connected in series. The resistor R 12  is connected to the positive pole of the power supply, and the resistor R 13  is grounded through a diode D 5  and a capacitor C 19  connected in series. An anode of the diode D 5  is connected to the resistor R 13 . A common terminal of the resistor R 13  and the diode D 5  is connected to the positive pole of the power supply through a field effect transistor Q 3 A. A cathode of the diode D 5  is connected to the positive power input terminal of the lithium battery charger circuit U 4 . A positive pole of the powering interface is connected to the positive pole of the power supply sequentially through a zener diode ZD 5 , a resistor R 14 , and a resistor R 15  connected in series. A control terminal of the field effect transistor Q 3 A is connected to a common terminal of the resistor R 14  and the resistor  15 . When no electrical equipments is connected to the powering interface, the field effect transistor Q 3 A is turned off, the field effect transistor Q 2 A is turned on, and the positive power supply supplies power to the lithium battery charger circuit U 4  through the field effect transistor Q 2 A. When certain electrical equipment is connected to the powering interface, the field effect transistor Q 3 A is turned on, and then, the field effect transistor Q 3 A drags the control terminal of the field effect transistor Q 2 A down to a low level. At this time, the field effect transistor Q 2 A is turned off, and the positive power supply stops supplying power to the lithium battery charger circuit U 4 , but directly outputs the power to the powering interface. A BAT terminal of the lithium battery charger circuit U 4  is connected to a positive pole of the electrical core, for supplying power to the electrical core. In this embodiment, the electrical core employs a lithium battery BAT. A chip enable (CE) terminal and a charging status indicator terminal CHAR of the lithium battery charger circuit U 4  are respectively connected to a data terminal of a single-chip processor U 5 . The single-chip processor U 5  controls operations of the lithium battery charger circuit U 4  and is used to identify a charging status of the lithium battery charger circuit U 4 . The present invention further includes a control unit, and the core of the control unit is the single-chip processor U 5 . In this embodiment, the single-chip processor U 5  employs a single-chip processor chip of Model EM78P347N. The control unit controls the overall operations of the present invention. A data terminal of a third pin of the single-chip processor U 5  is connected to a control terminal of a field effect transistor Q 2 B. The field effect transistor Q 2 B is connected between the positive pole of the electrical core and the positive pole of the powering interface in series, for controlling whether the electrical core supplies power to the external equipment or not. A data terminal of a sixteenth pin of the single-chip processor U 5  is connected to a control terminal of a field effect transistor Q 4 . The field effect transistor Q 4  is connected between the positive pole and the negative pole of the electrical core. In an emergency, the single-chip processor U 5  controls to turn on the field effect transistor Q 4 , so as to prevent the present invention from being damaged. A data terminal of a twelfth pin of the single-chip processor U 5  is connected to a switch SW for turning on/off and inputting control commands to the present invention. In this embodiment, the data terminal, a twentieth pin, and a twenty-first pin of the single-chip processor U 5  are connected to a dual-color LED LED 4 . A twenty-second pin is connected to an LED 3 . A twenty-third pin is connected to an LED 2 . A twenty-fourth pin is connected to an LED 1 . The LED 1 , LED 2 , and LED 3  are used to indicate a capacity of the battery, which is helpful for the user to determine the electric quantity of the electrical core in the present invention. In this embodiment, when the electric quantity of the electrical core is less than 10%, the LED 1 , LED 2 , and LED 3  are all turned off; when the electric quantity of the electrical core is 10%-40%, the LED 1  is turned on, and the LED 2  and LED 3  are turned off; when the electric quantity of the electrical core is 40%-70%, the LED 1  and LED 2  are turned on, and the LED 3  is turned off; when the electric quantity of the electrical core is 70%-100%, the LED  1 , LED 2 , and LED 3  are all turned on. The LED 4  is used to indicate the charging status in the present invention, in which when the electrical core is in a charging status, the red light of the LED 4  is turned on; after the charging is finished, the green light of the LED 4  is turned on. 
         [0023]    In order to enable the present invention to become more flexible, a USB port is added as a power input interface, in which a positive pole of the USB port is connected to the positive power input terminal of the lithium battery charger circuit U 4  through the diode D 5 , and a negative pole of the USB port is grounded. In this embodiment, the input USB port is a mini USB port. Another USB port is further added in the present invention as a power output interface, in which the output USB port is connected to the powering interface in parallel. A field effect transistor Q 3 B is connected between the output USB port and the powering interface, in which a control terminal of the field effect transistor Q 3 B is connected to a data terminal of a first pin of the single-chip processor U 5 . Therefore, the single-chip processor U 5  controls to output power through the USB port, or through both the powering interface and the output USB port. 
         [0024]    In usage, three power supply manners may be adopted in the present invention: 1. supply with a DC current; 2. supply with an AC current; and 3. supply through USB. Since the buck portion in the present invention bucks the voltage through an R/C buck circuit instead of a transformer, if the power is supplied with a DC current, an external DC source is directly connected to the charging interface. If the power is supplied with a commercial AC current, the commercial AC current is connected to the charging interface, and the high-voltage commercial AC current is bucked in voltage by the buck portion, and then rectified by the bridge rectifier BR 1 , so as to convert the AC current into an approximate DC current. After that, the process of supplying power with the DC current has the same operating mode as that of supplying power with the AC current. Particularly, an input power is output to a regulator module, processed by the AC/DC chip U 1 , and converted into a DC current, and then the DC current is output. Then, after being regulated by the adjustable regulated power supply U 3 , the power is output to the charging management unit, thereby charging the electrical core in the present invention. If the power is supplied through the USB, it merely needs to connect the input USB port of the present invention to the USB port of the computer through a USB data line, and the power is directly output to the charging management unit through the USB port, so as to charge the electrical core in the present invention. The present invention can directly supply power to the external device through the powering interface or the output USB port. 
         [0025]    When being charged, the present invention is connected to a data terminal of the single-chip processor U 5  through the charging status indicator terminal CHAR of the lithium battery charger circuit U 4 , so as to detect and identify the electric quantity of the electrical core in real time, and the electric quantity of the electrical core is displayed through the four LEDs connected to the single-chip processor U 5 . 
         [0026]    The present invention is further configured with a switch SW, for switching the operation status of the present invention, such as turning on/off the battery boost function, and turning on/off the USB output, and the specific function settings are realized by the programs in the single-chip processor U 5 . When no input or output operation occurs for OS, the single-chip processor U 5  automatically enters a sleep mode, and when an AC input or a DC input or a switching operation occurs, the single-chip processor U 5  automatically wakes up. 
         [0027]    The present invention can charge the internal electrical core with the AC current and DC current, and detect and display the energy stored in the internal electrical core. By adopting the standard output USB port, it is convenient to charge mobile phones and digital products of all models that are connected to the motherboard of the computer, and those products that cannot be connected to the motherboard of the computer can be charged through a randomly-fitted conversion adapter.
A multifunctional portable energy storage device, particularly, an energy storage device with functions of electric quantity storage, AC and DC charging, electric quantity detection, and DC boost output is provided, which is applicable for AC and DC bidirectional charging. The energy storage device includes an electrical core, a charging interface, and a powering interface. An external power supply charges the electrical core through the charging interface, and the electrical core supplies power to an external device through the powering interface. The energy storage device further includes an AC/DC converter, a control unit, and a charging management unit. The charging interface is connected to an input terminal of the AC/DC converter. An external AC current is converted into a DC current by the AC/DC converter and then input to the charging management unit. The charging management unit controls the DC current and supplies power to the electrical core, and the electrical core supplies power to the external device through the powering interface. The control unit controls the operations of the charging management unit. The present invention has a simple structure and can be used flexibly, which brings a lot of conveniences to users.