Abstract:
An electric power supplier includes an alternating/direct current conversion circuit, a first path, a second path, a switch circuit, and a current detection circuit. The alternating/direct current conversion circuit converts an alternating voltage to a direct voltage. One end of the first path is connected to a first load. One end of the second path is connected to the first path, and the other end thereof is connected to a second load. The first and second paths supply output voltage of the alternating/direct current conversion circuit to the first and second loads. The current detection circuit detects a value of the output current flowing through a node between the first and second paths, and controls the switch circuit, formed in the second path, to electrically connect or disconnect the node to/from the second load, based on a detected current value.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electric power supplier, a method for controlling supplying of electric power, and an information processing device. 
     2. Description of the Related Art 
     An electric power supplier for use in an information processing device, such as a personal computer and the like, includes an AC-DC converter, DC-DC converter, etc. 
     The electric power supplier converts an alternating voltage into a direct-current voltage, using the AC-DC converter, and converts an output voltage value of the AC-DC converter into a plurality of direct-current voltage values, using the DC-DC converter. Output voltages of the DC-DC converter are sent to each section included in the information processing device, such as a CPU (Central Processing Unit), memory, hard disk drive, etc. 
     Conventionally, the electric power supplier supervises whether the AC-DC converter is overloaded, and includes a current detection circuit and a detection resistor so as to avoid such an overloaded state of the AC-DC converter. The detection resistor is formed on a power supplying line for supplying electric power from the AC-DC converter to the DC-DC converter. The current detection circuit detects a current flowing through the resistor for detection, controls the DC-DC converter and reduces the output voltage of the DC-DC converter in the case where the detected current value exceeds a rated current value of the AC-DC converter (i.e. in the case where an overcurrent flows through the detection resistor). 
     However, in the conventional electric power suppliers, in the case where the AC-DC converter is prevented from being in an overloaded state, a reduction occurs in the voltage to be supplied to each section included in the information processing device, such as the CPU, etc. Hence, the electric power lacks in those devices, such as the CPU, memory, and the like which require sufficient electric power to operate. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in consideration of the above. It is accordingly an object of the present invention to provide an electric power supplier which can continuously supply a predetermined load of the supplier with electricity required by the load, a method for controlling supplying of electricity and an information processing device. 
     In order to achieve the above object, according to the first aspect of the present invention, there is provided an electric power supplier comprising: 
     an alternating/direct-current conversion circuit which converts an alternating voltage into a direct voltage, and outputs a converted voltage; 
     a first path, one end of which is connected to the alternating/direct-current conversion circuit, and other end of which is connected to a first load, the first path supplying output voltage of the alternating/direct-current conversion circuit to the first load; 
     a second path, one end of which is connected to the first path, and other end of which is connected to a second load, the second path supplying output voltage of the alternating/direct-current conversion circuit to the second load; 
     a switch circuit which is formed in the second path; and 
     a current detection circuit which detects a value of a current flowing a portion of the first path between the alternating/direct current conversion circuit and a node between the first path and the second path, and controls the switch circuit to electrically connect or disconnect the node to or from the second load, based on a detected current value. 
     The current detection circuit may control the switch circuit to electrically connect or disconnect the node to or from the second load, based on a difference between the detected current value and a predetermined current value, so that the detected current value becomes lower than the predetermined current value. 
     The current detection circuit may control the switch circuit to electrically connect or disconnect the node to or from the second load, in accordance with at least one of the difference between the detected value and the predetermined current value, an integrated result of the difference, and a differentiated result of the difference. 
     The current detection circuit may control the switch circuit to electrically disconnect the node from the second load, in a case where the detected value of the current is equal to or larger than a reference value which is an output current value of the alternating/direct-current conversion circuit being overloaded, and to electrically connect the node to the second load, in a case where the detected value of the current is lower than the reference value. 
     The current detection circuit may include a passive element which is formed in a portion of the first path located between the alternating/direct-current conversion circuit and the node, and detect a value of a current flowing through the passive element, and compare a detected value of the current with the reference value. 
     The current detection circuit may include a current control circuit which: 
     generates a control signal for controlling an operation of the switch circuit, based on a voltage generated across the passive element; and 
     supplies the switch circuit with a generated control signal; and 
     wherein the switch circuit may electrically connect or disconnect the node to or from the second load, in accordance with the control signal. 
     The passive element may comprise a fuse. 
     The passive element may comprise a coil included in a noise filter. 
     A signal may represent whether the second load is possible to electrically be disconnected from the node; and 
     the current control circuit may generate the control signal for controlling an operation of the switch circuit, in a case where a current flowing through the passive element is equal to or larger than the reference value and the signal sent from the second load represents that the second load is possible to electrically be disconnected from the node. 
     The first load may comprise a voltage-value conversion circuit which converts a voltage having a value of the alternating/direct-current conversion circuit into voltages having a plurality of values, and outputs the plurality of voltage. 
     The voltage-value conversion circuit may be connected to an information processing unit including a microprocessor and a memory. 
     The second load may comprise a battery circuit including a secondary battery; and 
     the battery circuit may detect whether the secondary battery is fully charged with electricity, and send a detection signal which represents detection results to the current control circuit; and 
     the current control circuit may generate the control signal for electrically disconnecting the node from the second load, in a case where the current flowing through the passive element is equal to or larger than the reference value and the detection signal represents that the secondary battery is fully charged. 
     In order to achieve the above object, according to the second aspect of the present invention, there is provided a method for controlling supplying of electric power, comprising: 
     sending electric power to a first load from a power circuit via a first path; 
     sending electric power to a second load from the power circuit via a second path connected to the first path; 
     detecting a value of the electric power sent from the power circuit to the first and second loads; and 
     electrically connecting and disconnecting a node between the first and second paths to or from the second load, based on a detected value of the electric power. 
     The electrically connecting and disconnecting may include: 
     electrically connecting and disconnecting the node to or from the second load, so that the detected value of the power becomes equal to or lower than the predetermined value, based on a difference between the detected value and a predetermined value of the power. 
     The electrically connecting and disconnecting may include: 
     electrically connecting or disconnecting the node to or from the second load, in accordance with at least one of the difference between the detected value of the power and the predetermined value of the power, an integrated result of the difference, and a differentiated result of the difference. 
     The electrically connecting and disconnecting may include: 
     electrically disconnecting the node from the second load, in a case where the detected value of the electric power is equal to or higher than a reference value which is output power of the power circuit being overloaded; and 
     electrically connecting the node to the second load, in a case where the detected value of the electric power is lower than the reference value. 
     The detecting may include: 
     detecting a value of output power of the power circuit, based on a value of a current flowing through a passive element which is formed in a portion of the first path between the power circuit and the node; and 
     comparing a detected value with the reference value. 
     The detecting may include: 
     generating a control signal for controlling an operation of a switch circuit which is formed in the second path; 
     sending the control signal to the switch circuit; and wherein 
     the electrically connecting and disconnecting may include connecting and disconnecting the node to or from the second load by controlling the switch circuit, in accordance with the control signal. 
     The passive element may comprise a fuse, or a coil included in a noise filter. 
     The sending the control signal includes: 
     accepting a permitting signal, for permitting the second load to electrically be disconnected from the node; and 
     generating the control signal for controlling an operation of the switching circuit, in a case where the detected value of the power is equal to or higher than the reference value and the permitting signal sent from the second load represents that the second load is possible to electrically be disconnected from the node. 
     In order to achieve the above object, according to the third aspect of the present invention, there is provided an information processing device comprising: 
     the electric power supplier according to claim 1; and 
     an information processing unit which is connected to the electric power supplier and driven by a voltage, applied thereto and sent from the electric power supplier; and 
     wherein the information processing unit includes 
     a memory which stores information, 
     an operational input section which inputs an instruction, 
     an input/output control section which performs inputting and outputting processing, 
     a display section which displays information, and 
     a processor which supervises a state of the operational input section through the input/output control section, reads out information from the memory and/or an external memory, executes processing based on read information, and controls the display section to display information corresponding to executed processing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The object and other objects and advantages of the present invention will become more apparent upon reading of the following detailed description and the accompanying drawings in which: 
     FIG. 1 is a block diagram showing the structure of a personal computer; 
     FIG. 2 is a block diagram showing the structure of an electric power supplier according to the first embodiment of the present invention; 
     FIG. 3 is a block diagram showing the structure of an electric power supplier according to the second embodiment of the present invention; 
     FIG. 4 is a block diagram showing the structure of an electric power supplier according to the third embodiment of the present invention; 
     FIG. 5 is a block diagram showing the structure of a personal computer; and 
     FIG. 6 is a block diagram showing the structure of an electric power supplier according to the fourth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will now be explained with reference to the accompanying drawings. 
     First Embodiment 
     An electric power supplier is used in a state where it is connected to a target device to be connected. Explanations will now be made to an electric power supplier according to the first embodiment of the present invention. A personal computer, including the electric power supplier and an information processing unit connected to the electric power supplier installed therein, will now specifically be described by way of example. 
     FIG. 1 is a block diagram showing the structure of a personal computer  100 , in which the electric power supplier according to the first embodiment is installed. This personal computer  100  briefly includes an information processing unit  120  and an electric power supplier  140 . 
     The information processing unit  120  has the structure for realizing an information processing function which is fundamental to a general-purpose computer. The electric power supplier  140  supplies each section, such as a bus, etc., included in the information processing unit  120  with electric power. The supplying of the electric power toward the information processing unit  120  is shown and represented by three arrows in FIG.  1 . 
     As illustrated in FIG. 1, the information processing unit  120  comprises a memory  121 , an input/output control section  122 , a display section  123 , an external memory  124 , an operational input section  125 , and a processor  126 . 
     The memory  121  includes a ROM (Read Only Memory), RAM (Random Access Memory), etc., and stores program data or any other various data. the input-output control section  122  includes a DMA (Direct Memory Access) controller. The memory  121 , input/output control section  122 , and processor  126  are connected with each other through a bus, and can send and receive data to and from one another. The input/output control section  122  controls the display section  123 , the external memory  124 , and the operational input section  125 , so as to input and output various information. 
     The display section  123  has an LCD (Liquid Crystal Display) plate and a driving circuit, etc., for example, and display various data. The external memory  124  includes an HDD (Hard Disk Drive), a CD-ROM read circuit, or the like, and stores program data and any other various data. The operational input section  125  has a keyboard, etc., and sends various instructions to the processor  126 . 
     The processor  126  has a CPU (Central Processing Unit), and controls each section included in the information processing unit  120 , as will specifically described below. 
     The processor  126  supervises the state of the operational input section  125  through the input/output control section  122 . The processor  126  reads out program data and various data from the memory  121  or external memory  124 , in accordance with the operational state of the input/output control section  122 . The processor  126  executes various information processing, based on the read data from the memory  121  or external memory  124 , and controls the display section  123  to display information corresponding to the executed information processing. 
     As shown in FIG. 2, the electric power supplier  140  includes an AC-DC converter  141 , a DC-DC converter  142 , a fuse  143 , a switching device  144 , a battery  145 , and a current control circuit  146 . 
     The AC-DC converter  141  converts, for example, a commercial source voltage to a direct-current voltage of 19V (volts), and outputs the converted direct-current voltage. 
     The DC-DC converter  142  is connected to the AC-DC converter  141 , and is a load which absorbs power from the AC-DC converter  141 . The DC-DC converter  142  converts an output voltage value of the AC-DC converter  141  to a plurality of direct-current voltage values. To be more specific, connected to the DC-DC converter  142  is the information processing unit  120 . The DC-DC converter  142  converts an output voltage of the AC-DC converter  141  to three direct-current voltages of, for example, 5.0V, 3.3V, 1.5V, and supplies the sections inside the information processing unit  120  with their corresponding one of the converted direct-current voltages. 
     The fuse  143  is, for example, of a current-fusing type. One end of the fuse  143  is connected to an output end of the AC-DC converter  141 , and the other end thereof is connected to an input end of the DC-DC converter  142 . 
     The switching device  144  includes a P-channel type MOSFET (Metal Oxide Semiconductor Field Effect Transistor). In this specification, the switching device  144  is hereinafter referred to as an FET  144 . The source (S) of the FET  144  is connected to the other end of the fuse  143 . A control voltage is sent from an output end of the current control circuit  146  to the gate (G) of the FET  144 . The drain (D) of the FET  144  is connected to the battery  145 , as will more specifically be described later. In the case where the FET  144  is in an on state, a current flows between the source and drain of the FET  144 , and a current flows from the AC-DC converter  144  to the battery  145 . In the state where the FET  144  is in an off state, no current flow between the source and drain of the FET  144 , the battery  145  is electrically disconnected from the AC-DC converter  141 . 
     The battery  145  is a load which absorbs power from the AC-DC converter  141 . In the case where commercial electric power is suspended to be sent to the AC-DC converter  141 , the battery  145  functions as a back-up power source for supplying electric power to the information processing unit  120 . The battery  145  includes a charge control circuit  150 , a charge circuit  151 , and a secondary battery  152 . In the case where the charge control circuit  150  is in the ON, the charge control circuit  150  controls the charge circuit  151  to charge the secondary battery  152  with electricity. As the secondary battery  152 , any one of, for example, a lithium ion battery, a Nickel-cadmium battery, a Nickel-hydrogen battery, etc. can be employed. When the battery  145  functions as a back-up battery, it supplies each section inside the information processing unit  120  with electricity charged in the secondary battery  152  through the DC-DC converter  142 . 
     The current control circuit  146  discriminates whether the current flowing through the fuse  143  is an overcurrent. In the case where it discriminated that the current is an overcurrent, the current control circuit  146  controls the FET  144  to reduce the amount of current flowing through the fuse  143 . In particular, the current control circuit  146  detects a voltage across the fuse  143 , and amplifies the detected voltage. The current control circuit  146  compares the value of the amplified voltage with a predetermined threshold value, and generates a control signal S 1  corresponding to a result of the comparison. In this case, the threshold value is set to a value larger than the value of the amplified voltage across the fuse  143  in the case where a rated current of the AC-DC converter  141  flows through the fuse  143 . The current control circuit  146  generates a control signal S 1  at a low level, in the case where the value of the amplified voltage is lower than a threshold value, and generates a control signal S 1  at a high level, in the case where the value of the amplified voltage is higher than a threshold value. Then, the current control circuit  146  supplies the gate of the FET  144  with the generated control signal S 1 . 
     If the electric power supplier  140  supplies the information processing unit  120  with driving electricity, and if the information processing unit  120  executes various processing operations, the personal computer  100  executes fundamental information processing, likewise any other general-purpose computers. 
     Generally, the electric power supplier  140  operates in the manner described below. 
     The AC-DC converter  141  converts a commercial source voltage of AC100V to a direct-current voltage of DC19V, for example. After this, the AC-DC converter  141  provides the direct-current voltage to the DC-DC converter  142  and battery  145 . The DC-DC converter  142  converts an output voltage (19V) of the AC-DC converter  141  into three direct-current voltages of 5.0V, 3.3V, 1.5V, and supplies each section inside the information processing unit  120  with their corresponding one of the three direct-current voltages. The AC-DC converter  141  converts a commercial source voltage into a direct-current voltage, and outputs the converted direct-current voltage. Upon this, a current flows through the fuse  143 , and a voltage drop is generated between both ends of the fuse  143 . The current control circuit  146  detects the voltage across the fuse  143 , amplifies the detected voltage, and compares the value of the amplified voltage with a threshold value. The current control circuit  146  generates a control signal S 1  in accordance with a result of the comparison, and supplies the gate of the FET  144  with the generated control signal S 1 . The FET  144  will be in an ON or OFF state, in accordance with the supplied control signal S 1 . 
     In the case where, for example, the processor  126  or external memory  124  inside the information processing unit  120  is to consume relatively a large amount of electric power, a current having a value higher than a rated current value of the AC-DC converter  141  flows through the fuse  143 . In such a case, the electric power supplier  140  operates as described below. 
     The current control circuit  146  discriminates that the value of the amplified voltage is higher than a threshold value, generates a control signal S 1  at a high level, and supplies the gate of the FET  144  with the generated control signal S 1 . Because the FET  144  will be in an OFF state in response to the supplied control signal S 1 , no current flows between the source and drain of the FET  144 . In addition, the battery  145  is electrically disconnected from the AC-DC converter  141 . Hence, the AC-DC converter  141  supplies only the DC-DC converter  142  with a direct-current voltage. This prevents a state wherein the AC-DC converter  141  is over loaded. 
     While this state continues for a predetermined period of time, the amount of electric power consumed by the processor  126  or external memory  124  is reduced. Along with the reduction in the amount of consumed electric power, the current flowing through the fuse  143  is reduced, and the value thereof is returned to a value which is equal to or lower than the rated current value of the AC-DC converter  141  afterwards. 
     In the case where the current, whose value is equal to or lower than the rated current value of the AC-DC converter  141 , flows through the fuse  143 , the electricity power supplier  140  operates in the manner described below. 
     The current control circuit  146  discriminates that the value of the amplified voltage is lower than a threshold value, generates a control signal S 1  at a low level, and supplies the gate of the FET  144  with the generated control signal S 1 . Because the FET  144  will be in an ON state in response to the supplied control signal S 1 , a current flows between the source and drain of the FET  144 . The AC-DC converter  141  supplies the DC-DC converter  142  and battery  145  with a direct-current voltage. 
     In the battery  145 , the charge control circuit  150  controls the charge circuit  151  to charge the secondary battery  152  with electricity. Even if the battery  145  is electrically disconnected from the AC-DC converter  141 , while the secondary battery  152  of the battery  145  is charged with electricity, as long as the disconnection period is only a short period of time, the secondary battery  152  will not badly be effected. 
     Second Embodiment 
     In the above-described embodiment, the current control circuit  146  generates the control signal S 1 , based on the value of the both-end voltage of the fuse  143 . However, the current control circuit  146  may generate the control signal S 1 , based on both of the value of the both-end voltage of the fuse  143  and the charge state of the secondary battery  152 . Explanations will now be made to thus structured electric power supplier according to the second embodiment. 
     FIG. 3 is a block diagram showing the structure of an electric power supplier  240  according to the second embodiment. 
     The electric power supplier  240  according to the second embodiment is installed in a personal computer, and has substantially the same structure as that of the electric power supplier of the first embodiment, so the same reference numerals as affixed to the same component elements. 
     A battery  245  has a detection signal generation circuit  153 , in addition to the structure of the battery  145  described in the first embodiment. The detection signal generation circuit  153  detects whether the secondary battery  152  is fully charged with electricity, generates a detection signal S 2 , and sends the generated signal to the current control circuit  146 . 
     The detection signal generation circuit  153  usually generates a detection signal S 2  at a low level, and generates a detection signal S 2  at a high level when the secondary battery  152  is fully charged with electricity. 
     When the value of the amplified both-end voltage is lager than a predetermined value, and when the detection signal S 2  at a high level is supplied, the current control circuit  246  generated a control signal S 1  for controlling the FET  144 . In the case where the detection signal generation circuit  153  generates a detection signal S 2  at a high level, the battery  245  can electrically be disconnected from the AC-DC converter  141 . Hence, in the case where the detection signal S 2  is at a high level, it is meant that the AC-DC converter  141  is electrically disconnected from the battery  245 . 
     According to this embodiment, a direct-current voltage is stably supplied to the information processing unit  120 . At the same time, while the secondary battery  152  is charged with electricity, the battery  245  is electrically disconnected from the AC-DC converter  141 . 
     Third Embodiment 
     In the above-described embodiments, the electric power supplier detects whether the AC-DC converter  141  is over loaded, based on the current flowing through the fuse, and the AC-DC converter  141  is electrically disconnected from the battery  145 . However, the component element for detecting the state wherein the AC-DC converter  141  is over loaded is not limited to the fuse. Explanations will now be made to the third embodiment of the present invention, which has another component element for detecting the above state. 
     FIG. 4 is a block diagram showing the structure of an electric power supplier  340  according to the third embodiment of the present invention. 
     The electric power supplier  340  is installed in a general-purpose personal computer. The direct-current voltage which is output from the AC-DC converter  141  includes frequency components which are caused by, for example, various noise, etc. In order to remove such noises, the electric power supplier  340  includes a noise filter. In place of the fuse, the electric power supplier  340  has substantially the same structure as that of the first embodiment, except that a coil included in the noise filter is used for detecting the state in which the AC-DC converter  141  is over loaded. Hence, the same reference numerals are affixed to the component elements. 
     A coil  343  forms a noise filter, together with a capacitor  347 , and has a function as resistance for a current including the frequency components. One end of the coil  343  is connected to an input terminal of one end of the current control circuit  346 . While the other end of the coil  343  is connected to an input terminal of the other end of the current control circuit  346  and to the source of the FET  144 . The capacitor  347  is connected to the other end of the coil  343  and a ground line. 
     The current control circuit  346  detects and amplifies the voltage generated between both ends of the coil  343 , and compares the amplified voltage value with a predetermined value. Under the same comparison condition performed in the first embodiment, the current control circuit  346  generates a control signal S 1  at a high or low level. 
     According to the above structure, the electric power supplier  340  according to this embodiment, can be operated likewise the first embodiment. The electric power supplier  340  can attenuate noises to be transmitted to the information processing unit  120  connected to the electric power supplier  340 , through the noise filter. 
     Fourth Embodiment 
     The structures of the electric power supplier and personal computer, in which the electric power supplier is installed, are not limited to those described in the above embodiments. A circuit which can electrically be disconnected from the AC-DC converter  141  may be prepared outside the electric power supplier. Explanations will now be made to an electric power supplier having such a structure, according to the fourth embodiment of the present invention. 
     FIG. 5 is a block diagram showing the structure of a personal computer in which an electric power supplier  440  according to the fourth embodiment is installed. 
     This personal computer  400  briefly includes an information processing unit  420  and the electric power supplier  440 . 
     The information processing unit  420  has substantially the same structure as that of the information processing unit  120  of the first embodiment, except that the information processing unit  420  includes two auxiliary power supplying sections  427   a  and  427   b.    
     The electric power supplier  440  has substantially the same structure as that of the electric power supplier  140  of the second embodiment, except that the electric power supplier  440  individually supplies the auxiliary power supplying section  427   a,    427   b,  and any other sections included in the personal computer  400  with electricity. 
     Each of the auxiliary power supplying sections  427   a  and  427   b,  which are shown in FIG. 5, has a secondary battery, and provides each section included in the information processing unit  120  with electricity, when electricity stops to be supplied from the electric power supplier  440 . 
     Each of the auxiliary power supplying sections  427   a  and  427   b  detects the electricity charged-level of the secondary battery in its corresponding auxiliary power supplying section, generates binary-level detection signals S 2   a  and S 2   b  of high or low, and supplies the electric power supplier  440  with the generated signals. 
     When a current having a current value which is higher than the rated current value of the AC-DC converter  141  flows through the fuse  143 , the electric power supplier  140  electrically disconnects at least one auxiliary power supplying section  427  from the AC-DC converter  141 , thereby to stably supply any other sections included in the information processing unit  420  with electricity. 
     The electric power supplier  440  has the structure shown in FIG.  6 . The same reference numerals are affixed to the same component elements as those of the first embodiment. 
     As seen from FIG. 6, the DC-DC converter  142  is connected to any sections inside the information processing unit  420  other than the auxiliary power supplying sections  427   a  and  427   b.    
     The AC-DC converter  141  is connected to each of the auxiliary power supplying sections  427   a  and  427   b  inside the information processing unit  420 , through transmission paths of FETs  444   a  and  444   b.    
     The current control circuit  446  has two detection-signal input terminals. Sent to the two detection-signal input terminals are detection signals S 2   a  and S 2   b  from the respective auxiliary power supplying sections  427   a  and  427   b.    
     The current control circuit  446  has two control-signal output terminals, and sends control signals S 1   a  and S 1   b  to the gates of the FETs  444   a  and  444   b  corresponding to the auxiliary power supplying sections  427   a  and  427   b,  respectively. 
     According to the above-described structure, in the case where the detection signal S 2   a  at a high level and the control signal S 2   b  at a low level are sent respectively from the auxiliary power supplying sections  427   a  and  427   b  to the current control circuit  446 , the electric power supplier  440  operates in the manner as will be described below. 
     The current control circuit  446  amplifies a voltage across the fuse  143 , compares the amplified voltage with a threshold value. In the case where it is determined that the value of the amplified voltage generated between both ends of the fuse  143  is higher than the threshold value, the current control circuit  446  generates a control signal S 1   a  at a high level and a control signal S 1   b  at a low level. After this, the current control circuit  446  sends the control signal S 1   a  at a high level to the gate of the FET  444   a  and a control signal S 1   b  at a low level to the gate of the FET  444   b.  In response to the sent control signal S 1 , the FET  444   a  is OFF, and the AC-DC converter  141  does not send a direct-current voltage to the auxiliary power supplying section  427   a.  In response to the sent control signal S 1 , the FET  444   b  is ON, and the AC-DC converter  141  sends a direct-current voltage to the auxiliary power supplying section  427   b.  Hence, the voltage output from the AC-DC converter  141  is sent to the DC-DC converter  142  and auxiliary power supplying section  427   b.    
     Similarly, in the case where detection signals S 2   a  and S 2   b  at a high level are sent from the auxiliary power supplying sections  427   a  and  427   b  to the current control circuit  446 , the voltage output from the AC-DC converter  141  is sent only to the DC-DC converter  142 . 
     According to this embodiment, the electric power supplier  440  can stably supply each fundamental section inside the information processing unit  420  with electricity, when the AC-DC converter  141  is over loaded. In addition, the electric power supplier  440  can continuously send electricity to any one of the auxiliary power supplying sections which is not fully charged with electricity. 
     Various embodiments and changes may be made thereonto without departing from the broad spirit and scope of the invention. 
     In the above explanations, the current control circuit  146  generates a control signal S 1 , in accordance with whether the value of the voltage across the fuse  143  is higher or lower than the threshold value. The present invention is not limited to this method. For example, the current control circuit  146  may generate the control signal S 1 , in accordance with the difference, between the detected voltage and the threshold value, and an integrated result of the difference, and a differentiated result of the difference, under the control of a PID (Proportional Integration and Differential) control program stored therein. 
     In the above-described embodiments, the explanations have been made to the battery circuit inside the electric power supplier or the auxiliary power supplying section inside the information processing unit, as one electrically disconnectable from the AC-DC converter  141 . However, such a circuit which can be electrically disconnected from the AC-DC converter  141  is not limited to the above. Any circuit, other than the main circuit, such as the CPU or memory of the information processing device, etc., may electrically be disconnected from the AC-DC converter  141 . For example, the personal computer may have the structure, wherein the backlight of the LCD (Liquid Crystal Display) is electrically disconnected from the AC-DC converter. In this case, at the time a current whose current value exceeds the rated current value of the AC-DC converter  141  flows through the fuse  143  inside the electric power supplier, the electricity is temporarily suspended to be sent thereto. 
     In the above-described embodiments, the current control circuit of the electric power supplier has determined whether the AC-DC converter is over loaded, based on the voltage across the fuse, or the coil forming the noise filter. However, the component element for detecting the current output from the AC-DC converter is not limited to the fuse or coil. For example, the element component for detecting the current output from the AC-DC converter may be a current transformer. In this case, the primary coil of the current transformer is formed in the voltage supply line for connecting the AC-DC converter and the DC-DC converter. The current control circuit is connected to the secondary coil of the current transformer, and detects whether the current flowing through the primary coil is an overcurrent. 
     In the above-described embodiments, the switching element  144  has been described as the P-channel type MOSFET. However, the switching element  144  may be a PNP-type bipolar transistor or any other device. 
     In the case where the value of the amplified voltage is higher than a predetermined value, the current control circuit  146  has been described as one generating a control signal S 1  at a high level. However, when the value of the amplified voltage is higher than a predetermined value, the current control circuit  146  may generate a control signal S 1  at a low level, and when the value of the amplified voltage is lower than the predetermined value, the current control circuit  146  may generate a control signal S 1  at a low level. In this case, the switching device  144  is formed of an N-channel type MOSFET, for example. 
     The battery  145  has been explained as one usually generating a detection signal at a low level, and generating a detection signal at a high level when the secondary battery reaches a predetermined charged-electricity level. However, when the battery generates a detection signal at a high level and when the secondary battery reaches a predetermined charged-electricity level, the battery may generate a detection signal at a low level. 
     In the above-described embodiments, the electric power supplier has been explained as one installed in a personal computer. However, the electric power supplier may be installed in a portable information terminal, a information processing device, or the like. Further, the electric power supplier is not limited to one installed in the target electric device, and thus can externally be prepared on the electric device. The above-described embodiments are intended to illustrate the present invention, not to limit the scope of the present invention. The scope of the present invention is shown by the attached claims rather than the embodiments. Various modifications made within the meaning of an equivalent of the claims of the invention and within the claims are to be regarded to be in the scope of the present invention. 
     This application is based on Japanese Patent Application No. 2000-141225 filed on May 15, 2000, and including specification, claims, drawings and summary. The disclosure of the above Japanese Patent Application is incorporated herein by reference in its entirety.