Patent Publication Number: US-2007097577-A1

Title: Electric power supplying apparatus and image forming apparatus

Description:
This application is based on Japanese Patent Application No. 2005-312745 filed on Oct. 27, 2005 in Japanese Patent Office, the entire content of which is hereby incorporated by reference.  
     BACKGROUND OF THE INVENTION  
      The present invention relates to an electric power supplying apparatus that supplies alternate current electric power (hereinafter, referred to as AC electric power for simplicity), supplied from a plurality of alternate current electric power sources (hereinafter, referred to as AC power sources for simplicity), to an electric power loading section, and an image forming apparatus that is provided with an electric power supplying section concerned.  
      Generally speaking, when the image forming apparatus, such as a laser printer, a copier, etc., outputs a print based on image data, a toner image developed on a photoreceptor drum based on the image data is transferred onto a recording medium, such as a paper sheet, etc., and then, the transferred toner image is fixed onto the recording medium by applying heat and pressure to the toner image by employing a fixing device heated by a heating section, so as to form the image on the recording medium concerned. In the image forming apparatus provided with the fixing device mentioned in the above, the electric power consumption for heating the heating device (the electric power loading section), such as an induction coil, etc., is getting large, and associated with the large-sizing trend of image forming apparatus having a high-speed capability and an enhanced functions, the electric power consumption of such the image forming apparatus has been increasing rapidly in recent years. Generally speaking, an amount of the electric power available for the image forming apparatus (rated electric power) is determined at a predetermined value, and an amount of the electric power to be supplied to the heating device and other electric power loading sections is limited within a range of the available amount of the electric power (the predetermined rated electric power).  
      Conventionally, a method for increasing an input voltage or an input current, or an electric power code, having a large capacity of the electric current to be flew per one code, is employed for the power supply section of the electric apparatus whose electric power consumption is relatively large, such as the image forming apparatus mentioned in the above. In the abovementioned cases, however, since the input terminal and/or the electric power code should be changed to larger capacity one, the scale of the modification of the electric power facility would be getting larger at the place where the electric apparatus is to be installed, resulting in the adverse problem for changing the apparatus to new one. To solve the abovementioned problem, for instance, Patent document  1  and Patent document 2 (Tokkai 2003-244359 and Tokkai 2005-121681, both are Japanese Non-Examined Patent Publications) set forth the technology for dividing the plural electric power loading sections, which are provided in the image forming apparatus proper, into several blocks corresponding to the functions, so as to independently supply the AC electric power, fed from each of the plural commercial power sources (AC electric power sources), to each of the blocks.  
      According to the technology set forth in Patent document 1 and Patent document 2 (Tokkai 2003-244359 and Tokkai 2005-121681), however, since the AC electric power, fed from each of the plural commercial power sources, is independently supplied to each of the blocks, the amount of the electric power consumption of the block concerned cannot exceed the maximum electric power to be fed from one of the plural commercial power sources, sometimes, resulting in an inability of supplying a sufficient electric power necessary for the electric power loading section concerned.  
     SUMMARY OF THE INVENTION  
      To overcome the abovementioned drawbacks in conventional image forming apparatus, it is an object of the present invention to provide an electric power supplying apparatus and an image forming apparatus, which supply AC electric powers fed from a plurality of commercial electric power sources to an electric power loading section, while make it possible to supply an amount of electric power exceeding a maximum rated electric power fed from one of the plurality of commercial electric power sources.  
      Accordingly, to overcome the cited shortcomings, the abovementioned object of the present invention can be attained by electric power supplying apparatus and image forming apparatus described as follow. 
      (1) An electric power supplying apparatus, comprising: a plurality of AC power inputting ports that are respectively coupled to a plurality of AC power sources, so as to simultaneously introduce various kinds of AC electric power units from the plurality of AC power sources; an electric power combining section to combine the AC electric power units, supplied from the plurality of AC power sources, with each other, so as to generate a combined electric power, serving as a single electric power source; and a combined electric power outputting port that is coupled to an electric power load section in order to supply the combined electric power to the electric power load section.     (2) An image forming apparatus, comprising: a fixing section to fix a toner image formed on a recording medium; an electromagnetic induction heating device to heat the fixing section by employing an electromagnetic induction heating action; and an electric power supplying section to supply electric powers fed from a plurality of AC power sources, serving as commercial electric power sources, to the electro-magnetic induction heating device and another electric power load section; wherein the electric power supplying section includes: a plurality of AC power inputting ports that are respectively coupled to the plurality of AC power sources, so as to simultaneously introduce various kinds of AC electric power units from the plurality of AC power sources; and an electric power combining section to combine the AC electric power units, supplied from the plurality of AC power sources, with each other, so as to generate a combined electric power, serving as a single electric power source; and a combined electric power outputting port that is coupled to the electric power load section in order to supply the combined electric power to the electric power load section.     (3) An electric power supplying apparatus, characterized in that the electric power supplying apparatus is provided with an electric power combining section to combine AC electric powers supplied from a plurality of AC power sources into a single electric power so as to supply the single electric power to an electric power load section.   

    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Other objects and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:  
       FIG. 1  shows an internal configuration of an electric apparatus embodied in the present invention;  
       FIG. 2  shows a configuration of an image forming section and a fixing device of the image forming apparatus embodied in the present invention;  
       FIG. 3  shows an IH heater incorporated in an inside space of a fixing roller;  
       FIG. 4  shows an internal configuration of an image forming apparatus embodied in the present invention;  
       FIG. 5  shows an internal configuration of AC/DC converters provided in an electric power combining section as a first embodiment of the present invention;  
       FIG. 6  shows an internal configuration of AC/DC converters provided in an electric power combining section as a second embodiment of the present invention;  
       FIG. 7  shows a flowchart of an electric power limit controlling operation embodied in the present invention; and  
       FIG. 8  shows an example of an electric power controlling sequence conducted during the warm-up operating period. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Referring to the drawings, as the best mode of the present invention, the preferred embodiment will be detailed in the following. However, the scope of the present invention is not limited to the examples shown in the drawings.  
     First Embodiment  
      Initially, referring to  FIG. 1 , the internal configuration of an electric apparatus  100  provided with an electric power supplying apparatus embodied in the present invention.  
      As shown in  FIG. 1 , the electric apparatus  100 , serving as the electric power supplying apparatus, is provided with an electric power combining section  10 , a control section  21 , a DC power source  22 , electric power loading sections  23 , etc.  
      The electric power combining section  10  combines AC electric powers, fed from a plurality of commercial power sources (AC power sources) E 1 -En (where, “n” represents a natural number), with each other so as to generate a single electric power to be supplied into the DC power source  22  and the electric power loading sections  23 . Incidentally, in the present embodiment, the maximum amount of electric power fed from each of the plurality of commercial power sources E 1 -En is assumed at 100V/15 Amax. However, the value of the maximum amount of electric power is not limited to the above.  
      The control section  21  is constituted by a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc., in order to totally control the whole system of the electric apparatus  100  by executing the system programs stored in the ROM based on the various kinds of setting values read from the ROM. Further, the control section  21  also controls amounts of electric powers to be supplied into the electric power loading sections  23  corresponding to the operating statuses of the electric power loading sections  23 .  
      The DC power source  22  converts the voltage of the DC electric power, generated by combining the plural AC electric powers in the electric power combining section  10 , to a predetermined voltage value, so as to supply the DC electric power having the converted voltage to the control section  21 .  
      The electric power loading sections  23  corresponds to various kinds of functional sections, each of which consumes electric power to achieve a predetermined functional goal (for instance, such as a heating device for raising a temperature, etc.), and is constituted by a plurality of electric power loading sections  23   a - 23   n.  Hereinafter, the plurality of electric power loading sections  23   a - 23   n  are totally called the electric power loading sections  23 . Incidentally, although the electric power loading sections  23  includes the plurality of electric power loading sections  23   a - 23   n  in the present embodiment, the scope of the present invention is not limited to the above, and a single electric power loading section is also applicable in the present invention.  
      The case in which an image forming apparatus is exemplified as the electric apparatus  100  will be detailed in the following. However, it is needless to say that the scope of the electric apparatus  100  is not limited to the above.  
      At first, referring to  FIG. 2  and  FIG. 3 , brief configurations of an image forming section  40  and a fixing device  50  equipped in an image forming apparatus  200  will be explained in the following.  
      As shown in  FIG. 2 , the image forming section  40  is provided with a photoreceptor drum  41 , a charging device  42  for charging the photoreceptor drum  41 , an exposing section  43  for applying an exposing operation onto the photoreceptor drum  41 , a developing device  44  for developing a latent image formed on the photoreceptor drum  41  with toner, a transferring section  45  for transferring the toner image developed on the photoreceptor drum  41  onto a paper sheet P and a cleaning device  46  for cleaning residual toner remained on the surface of the photoreceptor drum  41 .  
      When the paper sheet P is conveyed to the image forming section  40 , the circumferential surface of the photoreceptor drum  41  is uniformly charged at a predetermined electric potential by the charging device  42 , and then, exposed by the exposing section  43  so as to form a latent image on the circumferential surface of the photoreceptor drum  41 . Then, the latent image is developed with toner, so as to form a toner image, serving as a visible image, on the photoreceptor drum  41 . Further, the transferring section  45  transfers the toner image formed on the photoreceptor drum  41  onto the paper sheet P conveyed to the photoreceptor drum  41 , and after the transferring operation is completed, the residual toner remained on the photoreceptor drum  41  are removed by the cleaning device  46 , in order to reuse the photoreceptor drum  41  for the next image forming operation.  
      On the other hand, the paper sheet P, bearing the toner image through the abovementioned process, is conveyed from the photoreceptor drum  41  to the fixing device  50  in which the unfixed toner image is fixed onto the paper sheet P, so as to form a print image on the paper sheet P.  
      The fixing device  50  is provided with a fixing roller  51  serving as a heating member including an induction heating heater  321  (electro-magnetic Induction Heating: hereinafter, referred to as an IH heater  321 , for simplicity) and a pressure roller  52  serving as a pressing member that press-contacts the fixing roller  51  so as to form a fixing nip portion.  
      As shown in  FIG. 3 , the fixing roller  51  incorporates the IH heater  321  in its inside space. The IH heater  321  includes an induction coil  321 a and a core member  321 b made of the magnetic material and disposed at a center of the inside space, so as to serve as a heating source for the fixing roller  51 . Concretely speaking, the induction coil  321 a is activated by the AC current supplied from an IH heater driving power source  322 , so as to diverge alternate magnetic fluxes, being periodically changing, from the induction coil  321   a.  The generated alternate magnetic fluxes induce induction currents in the fixing roller  51  so that Joule losses of the induction currents generate heat for heating the fixing roller  51 . Incidentally, it is also applicable that the IH heater  321  includes a plurality of induction coils.  
      A temperature sensor  323   a  and a temperature sensor  323   b  (hereinafter, also referred to as a temperature sensor  323 , as a total name for both of them) are disposed at the fixing roller  51  in a contacting state, or in the vicinity of the fixing roller  51 , and temperature detecting signals outputted from the temperature sensor  323  are inputted into the control section  21 .  
       FIG. 4  shows an internal configuration of the image forming apparatus  200 . Incidentally, for the sake of the simplicity of the explanation, the same reference numbers are attached to the elements being same as those shown in  FIG. 1 , and detailed explanations of them will be omitted as needed, in the following.  
      As shown in  FIG. 4 , the image forming apparatus  200  is provided with the electric power combining section  10 , the control section  21 , the DC power source  22 , the electric power loading sections  23 , a power switch  24 , a supplemental power source  25 , a relay controlling section  26 , a relay  27 , a relay  28 , a capacitor  29 , a rechargeable power source  30 , an apparatus internal heater  31 , a fixing section  32 , a display section  33 , etc.  
      The a power switch  24  is used for turning ON/OFF the flow of AC electric power from the commercial power sources El and E 2  into the image forming apparatus  200  by the operator. The supplemental power source  25  converts the AC electric power fed from the commercial power sources El to the DC electric power, so as to output the converted DC electric power to the relay controlling section  26 . The relay controlling section  26  turns ON the relay  27  and the relay  28  when the electric power is supplied from the supplemental power source  25 . The relay  27  outputs the AC electric power, fed from the commercial power source El under the controlling operation of the relay controlling section  26 , to an AC/DC converter  11  in the electric power combining section  10 . Further, the relay  28  outputs the AC electric power, fed from the commercial power source E 2  under the controlling operation of the relay controlling section  26 , to a AC/DC converter  13  in the electric power combining section  10 .  
      The electric power combining section  10  is constituted by the AC/DC converter  11 , the AC/DC converter  13 , a rectifying diode  15 , a rectifying diode  16  and a capacitor  17 . The a AC/DC converter  11  converts the AC electric power fed from the commercial power sources El through the relay  27  to the DC electric power, so as to output the converted DC electric power through the rectifying diode  15 . The a AC/DC converter  13  converts the AC electric power fed from the commercial power sources El through the relay  28  to the DC electric power, so as to output the converted DC electric power through the rectifying diode  16 . The capacitor  17  is used for smoothing the DC electric powers outputted from the AC/DC converter  11  and the AC/DC converter  13  through the rectifying diode  15  and the rectifying diode  16 . The DC electric powers, outputted from the AC/DC converter  11  and the AC/DC converter  13  through the rectifying diode  15  and the rectifying diode  16 , are combined with each other at a DC output port “A” of the AC/DC converter  11  and the AC/DC converter  13 , so as to output a single DC electric power Vout to the DC power source  22  and the fixing section  32 .  
      The control section  21  is constituted by a CPU, a ROM, a RAM, etc. in order to totally control the whole system of the image forming apparatus  200  by executing the system programs stored in the ROM based on the various kinds of setting values read from the ROM.  
      The control section  21  outputs a control signal (IH_CONT signal) for instructing the supply of the driving electric power for heating the IH heater  321  to the IH heater driving power source  322  and another control signal (IH_POWER command signal) for instructing the amount of electric power to be supplied. Concretely speaking, the control section  21  generates the IH_POWER command signal for adjusting the heating temperature, based on the temperature detecting signals inputted from the temperature sensor  323 , and outputs the IH_POWER command signal to the IH heater driving power source  322 . Then, the IH heater driving power source  322  supplies an amount of electric power corresponding to the control signals sent from the control section  21 , so as to adjusts the heating temperature of the IH heater  321 .  
      The DC power source  22  converts a current voltage value of the single DC electric power Vout combined in the electric power combining section  10  to the predetermined voltage value, and supplies the converted single DC electric power Vout to the control section  21 , the electric power loading sections  23  and the rechargeable power source  30 . The electric power loading sections  23  includes a plurality of functional sections for implementing the total operation of the image forming apparatus  200 , which are driven by the single DC electric power Vout. Incidentally, a grounding port of the capacitor  17  (common grounding) is coupled to a grounding port of the DC power source  22  (connected to the outside case) through the capacitor  29 .  
      The rechargeable power source  30  is constituted by an electric double layer capacitor, etc., to charge a predetermined amount of the DC electric power fed from the DC power source  22 , so as to supply the charged DC electric power to the apparatus internal heater  31 . The apparatus internal heater  31 , serving as a heating device, such as a heating lump, etc., heats the predetermined portion in the image forming apparatus  200  corresponding to the DC electric power supplied from the rechargeable power source  30 .  
      The fixing section  32  is constituted by the IH heater  321  for heating the fixing roller  51 , the IH heater driving power source  322  for supplying the driving electric power to the IH heater  321  based on the single DC electric power Vout supplied from the electric power combining section  10 , the temperature sensor  323  for detecting the temperatures of the fixing roller  51  so as to output the detected results to the control section  21 , etc.  
      The display section  33  is constituted by a display device, such as a CRT (Cathode Ray Tube), a LCD (Liquid Crystal Display), an organic or inorganic ELD (Electro Luminescence Display), etc., so as to display various kinds of images, based on the various kinds of display data inputted under the controlling operations conducted by the control section  21 , on its screen.  
       FIG. 5  shows an internal configuration of the AC/DC converter  11  and the AC/DC converter  13 . Initially, the AC/DC converter  11  will be detailed in the following.  
      As shown in  FIG. 5 , the AC/DC converter  11  is constituted by a rectifying bridge  111 , a capacitor  112 , a resistor  113 , a resistor  114 , a switching element  115 , a boosting coil  116 , a rectifying diode  117 , a resistor  118 , a resistor  119 , a capacitor  120 , and a control IC  121 , etc.  
      The rectifying bridge  111  rectifies the AC electric power fed from the commercial power source E 1  so as to output the rectified DC electric power to the boosting coil  116 . The capacitor  112  is coupled in parallel to the output ports of the rectifying bridge  111  so as to smooth the back electromotive force generated by the boosting coil  116  and apply it to the output ports of the rectifying bridge  111 . A potential divider constituted by the resistor  113  and the resistor  114  is coupled to the output ports of the rectifying bridge  111  so as to output a divided voltage (hereinafter, referred to as a divided voltage  1 ) to an adding device  1211  of the control IC  121 , detailed later.  
      The switching element  115  intermittently interrupts the DC electric power to be inputted into the boosting coil  116  under the controlling operation of the control IC  121  detailed later. The back electromotive force, generated in the boosting coil  116  by the electric power controlling action of the switching element  115 , is rectified by the rectifying diode  117 , and then, smoothed by the capacitor  120 , so as to output it through the rectifying diode  15 . A potential divider constituted by the resistor  118  and the resistor  119  is coupled to the output ports of the rectifying diode  117  so as to output a divided voltage (hereinafter, referred to as a divided voltage  2 ) to both the adding device  1211  of the control IC  121  detailed later and an adding device  1411  of a control IC  141  detailed later.  
      The control IC  121  is constituted by the adding device  1211 , an oscillator  1212 , a comparator  1213 , a resistor  1214 , etc. The adding device  1211  adds the divided voltage  1 , the divided voltage  2  and a divided voltage  4  sent from the AC/DC converter  13  detailed later to output the added voltage to the comparator  1213 . The oscillator  1212  generates (oscillates) signals having a pulse-like waveform, such as a triangle waveform, a rectangular waveform, etc., and output the generated signals to the comparator  1213 . The comparator  1213  compares the signals outputted by the oscillator  1212  with the added voltage inputted from the adding device  1211  so as to generate PWM (Pulse Width Modulation) waveform signals. Since the output port of the comparator  1213  is coupled to the switching element  115  through the resistor  1214 , the intermittent interrupting actions performed by the switching element  115  are controlled on the basis of the PWM (Pulse Width Modulation) waveform signals so as to control the electric power flew into the boosting coil  116 . In this operation, the control IC  121  controls the switching element  115  so that a voltage value V 1  of the DC electric power boosted by the boosting coil  116  becomes equal to a voltage value V 2  of the DC electric power outputted from the AC/DC converter  13 .  
      Next, the AC/DC converter  13  will be detailed in the following.  
      As shown in  FIG. 5 , the AC/DC converter  13  is constituted by a rectifying bridge  131 , a capacitor  132 , a resistor  133 , a resistor  134 , a switching element  135 , a boosting coil  136 , a rectifying diode  137 , a resistor  138 , a resistor  139 , a capacitor  140 , the control IC  141 , etc., and has the configuration same as that of the AC/DC converter  11 .  
      The rectifying bridge  131  rectifies the AC electric power fed from the commercial power source E 2  so as to output the rectified DC electric power to the boosting coil  136 . The capacitor  132  is coupled in parallel to the output ports of the rectifying bridge  131  so as to smooth the back electromotive force generated by the boosting coil  136  and apply it to the output ports of the rectifying bridge  131 . A potential divider constituted by the resistor  133  and the resistor  134  is coupled to the output ports of the rectifying bridge  131  so as to output a divided voltage (hereinafter, referred to as a divided voltage  3 ) to the adding device  1411  of the control IC  141 , detailed later.  
      The switching element  135  intermittently interrupts the DC electric power to be inputted into the boosting coil  136  under the controlling operation of the control IC  141  detailed later. The back electromotive force, generated in the boosting coil  136  by the electric power controlling action of the switching element  135 , is rectified by the rectifying diode  137 , and then, smoothed by the capacitor  140 , so as to output it through the rectifying diode  16 . A potential divider constituted by the resistor  138  and the resistor  139  is coupled to the output ports of the rectifying diode  137  so as to output a divided voltage (hereinafter, referred to as a divided voltage  4 ) to both the adding device  1411  of the control IC  141  detailed later and the adding device  1211  of a control IC  121  mentioned in the above.  
      The control IC  141  is constituted by the adding device  1411 , an oscillator  1412 , a comparator  1413 , a resistor  1414 , etc. The adding device  1411  adds the divided voltage  3 , the divided voltage  4  and a divided voltage  2  sent from the AC/DC converter  11  mentioned in the above to output the added voltage to the comparator  1413 . The oscillator  1412  generates (oscillates) signals having a pulse-like waveform, such as a triangle waveform, a rectangular waveform, etc., and output the generated signals to the comparator  1413 . The comparator  1413  compares the signals outputted by the oscillator  1412  with the added voltage inputted from the adding device  1411  so as to generate PWM (Pulse Width Modulation) waveform signals. Since the output port of the comparator  1413  is coupled to the switching element  135  through the resistor  1414 , the intermittent interrupting actions performed by the switching element  135  are controlled on the basis of the PWM (Pulse Width Modulation) waveform signals so as to control the electric power flew into the boosting coil  136 . In this operation, the control IC  141  controls the switching element  1350 so that the voltage value V 2  of the DC electric power boosted by the boosting coil  136  becomes equal to the voltage value V 1  of the DC electric power outputted from the AC/DC converter  11 .  
      The DC electric powers outputted from the AC/DC converter  11  and the AC/DC converter  13  are combined at the DC output port “A” of the both converters, and inputted as the single DC electric power Vout into the DC power source  22  and the fixing section  32 .  
      In the abovementioned configuration, the AC electric powers fed from the commercial power sources E 1  and E 2  are converted to the DC electric powers whose voltages are equal to each other under the controlling actions conducted by the control IC  121  of the AC/DC converter  11  and the control IC  141  of the AC/DC converter  13 , both of which are provided in the electric power combining section  10 . Then, the converted DC electric powers are combined into the single DC electric power Vout at the DC output port “A” of both the AC/DC converter  11  and the AC/DC converter  13 , so that the single DC electric power Vout is supplied to each of the electric power loading sections (such as the DC power source  22 , the electric power loading sections  23 , the apparatus internal heater  31 , the fixing section  32 , etc.). Further, the control section  21  controls the operations of each of the electric power loading sections, in order to achieve the total operation of the image forming apparatus  200 . Incidentally, it is preferable that the control section  21  conducts a power controlling operation, so as to keep a total amount of the electric power to be supplied to each of the electric power loading sections at a level lower than the rated voltage established in advance.  
      As described in the foregoing, according to the embodiment of the present invention, since the AC electric powers fed from the plurality of commercial power sources can be combined into a single electric power so as to supply the combined single electric power to the electric power loading sections, it becomes possible to supply the electric power, exceeding the maximum electric power being suppliable from one of the plurality of commercial power sources, to the electromagnetic induction heating device and the other electric power loading sections, provided in the image forming apparatus.  
     Second Embodiment  
      Next, the second embodiment of the present invention will be detailed in the following. Incidentally, for the sake of the simplicity of the explanation, the same reference numbers are attached to the elements being same as those of the first embodiment, and detailed explanations of them will be omitted in the following as needed.  
      At first, referring to  FIG. 6 , the internal configuration of the electric power combining section  10  in the second embodiment will be detailed in the following.  
      As shown in  FIG. 6 , in addition to the aforementioned configuration shown in  FIG. 5 , the AC/DC converter  11  is further provided with a current detecting section  122 , a current controlling section  123  and a converting circuit  124 .  
      The current detecting section  122  includes a current transformer, etc., to detect an electric current of the AC electric power fed from the commercial power source El and output the current detected signal to both the current controlling section  123  and the converting circuit  124 .  
      The current controlling section  123  compares a current value I 1  of the current detected signal inputted from the current detecting section  122  with a current limit value established in advance and stored in the current controlling section  123  (for instance,  15 A), to output a comparison result voltage based on the comparison result to the adding device  1211 . The comparison result voltage as well as the divided voltage  1 , the divided voltage  2 , the divided voltage  4  mentioned in the above, is inputted into the adding device  1211 , so as to add them each other and to output the added voltage to the comparator  1213 . The comparator  1213  compares the signals outputted by the oscillator  1212  with the added voltage inputted from the adding device  1211  so as to generate PWM (Pulse Width Modulation) waveform signals. By driving the switching element based on the generated PWM waveform signals, the current value of the input current is adjusted to the current limit value mentioned in the above.  
      In the above configuration, the current limit value of the current controlling section  123  can be established corresponding to a control signal sent from the control section  21 . For instance, it is applicable that that the current limit value can be established corresponding to the operating statuses of the electric power loading sections  23 , the apparatus internal heater  31 , the fixing section  32 , etc. For instance, the maximum current value of the electric power fed from the commercial power source E 1  ( 15 A) or a predetermined current value lower than the maximum current value (hereinafter, referred to as a limiter current value) can be established as the current limit value to be established in the current controlling section  123 .  
      The converting circuit  124  includes an analogue-to-digital converter, a photo-interrupter, etc., in order to convert the current detected signal inputted from the current detecting section  122  to a predetermined instruction signal, and outputs it to the control section  21 . Based on the current value instructed by the instruction signal, the control section  21  controls the amount of electric power to be supplied from the DC power source  22  and the fixing section  32  (IH heater driving power source  322 ).  
      As shown in  FIG. 6 , in addition to the aforementioned configuration shown in  FIG. 5 , the AC/DC converter  13  is further provided with a current detecting section  142 , a current controlling section  143  and a converting circuit  144 .  
      The current detecting section  142  includes a current transformer, etc., to detect an electric current of the AC electric power fed from the commercial power source E 2  and output the current detected signal to both the current controlling section  143  and the converting circuit  144 .  
      The current controlling section  143  compares a current value I 2  of the current detected signal inputted from the current detecting section  142  with a current limit value established in advance (for instance,  5 A), to output a comparison result voltage based on the comparison result to the adding device  1411 . The comparison result voltage as well as the divided voltage  3 , the divided voltage  4 , the divided voltage  2  mentioned in the above, is inputted into the adding device  1411 , so as to add them each other and to output the added voltage to the comparator  1413 . The comparator  1413  compares the signals outputted by the oscillator  1412  with the added voltage inputted from the adding device  1411  so as to generate PWM (Pulse Width Modulation) waveform signals. By driving the switching element based on the generated PWM waveform signals, the current value of the input current is adjusted to the current limit value mentioned in the above.  
      In the above configuration, the current limit value of the current controlling section  143  can be established corresponding to a control signal sent from the control section  21 . For instance, it is applicable that that the current limit value can be established corresponding to the operating statuses of the electric power loading sections  23 , the apparatus internal heater  31 , the fixing section  32 , etc.  
      The converting circuit  144  includes an analogue-to-digital converter, a photo-interrupter, etc., in order to convert the current detected signal inputted from the current detecting section  142  to a predetermined instruction signal, and outputs it to the control section  21 . Based on the current value instructed by the instruction signal, the control section  21  controls the amount of electric power to be supplied from the DC power source  22  and the fixing section  32  (IH heater driving power source  322 ). In addition, when the input current exceeds the current limit value established in the converting circuit  144 , the control section  21  deactivates the whole operation of the image forming apparatus  200 .  
      Next, referring to  FIG. 7  and  FIG. 8 , the electric power limit controlling operation to be conducted at a starting time (during a warm-up period) of the image forming apparatus  200  will be detailed in the following. Incidentally, as a premise of this operation, it is assumed that the maximum current value of  15 A and the limiter current value of  5 A are established in the current controlling section  123  and the current controlling section  143 , respectively. Further, it is also assumed that the rated electric power of the image forming apparatus  200  is AC100V/20 Amax.  
       FIG. 7  shows a flowchart of the electric power limit controlling operation in regard to the electric power to be supplied into the IH heater driving power source  322  (hereinafter, referred to as an IH fixing electric power). Incidentally, in this flowchart, the control section  21  conducts each of the actions included in the electric power limit controlling operation. Further, this operation is conducted either continuously or periodically at predetermined intervals during the activating time of the image forming apparatus  200 .  
      The flowchart of the electric power limit controlling operation, shown in  FIG. 7 , includes the steps of: setting the IH fixing electric power as a predetermined value (Step S 11 ); confirming the current value I 2  based on the instruction signal sent from the converting circuit  144  (Step S 12 ); determining whether or not the current value I 2  is equal to or lower than the limiter current value of  5 A (Step S 13 ); deactivating the whole operation of the image forming apparatus  200  and displaying a message indicating “OCCURRENCE OF ERROR” on a screen of the display section (Step S 14 ), when determining that the current value I 2  exceeds the limiter current value of  5 A (Step S 13 , No); and finalizing the electric power limit controlling operation (END). Incidentally, it is preferable that the value of the IH fixing electric power to be established in Step S 11  is the maximum amount of electric power being suppliable under a current status, considering the electric power consumptions in the electric power loading sections  23 , etc.  
      The flowchart of the electric power limit controlling operation, shown in  FIG. 7 , further includes the steps of: confirming the current value I 1  based on the instruction signal sent from the converting circuit  124  (Step S 15 ), when determining that the current value  12  is equal to or lower than the limiter current value of  5 A (Step S 13 , Yes); determining whether or not the current value I 1  is lower than the maximum current value of  15 A (Step S 16 ); reducing the IH fixing electric power by a predetermined amount (Step S 17 ), when determining that the current value I 1  is equal to or higher than the maximum current value of  15 A (Step S 16 , No); determining whether or not the IH fixing electric power could be reduced while maintaining the normal operating state of the image forming apparatus  200  (Step S 18 ); returning to Step S 12 , when determining that the IH fixing electric power could be successfully reduced in Step S 18 ; deactivating the whole operation of the image forming apparatus  200  and displaying a message indicating “OCCURRENCE OF ERROR” on a screen of the display section (Step S 19 ), when determining that the IH fixing electric power could not be successfully reduced (Step S 18 , No); and finalizing the electric power limit controlling operation (END).  
      The flowchart of the electric power limit controlling operation, shown in  FIG. 7 , further includes the steps of: increasing the IH fixing electric power by a predetermined amount (Step S 20 ), when determining that the current value I 1  is lower than the maximum current value of  15 A (Step S 16 , Yes); determining whether or not the IH fixing electric power could be increased (Step S 21 ); returning to Step S 12 , when determining that the IH fixing electric power could be successfully increased in Step S 21 ; and finalizing the electric power limit controlling operation (END) and outputting the IH electric power instruction signal for instructing the amount of electric power established in Step S 20  to the IH heater driving power source  322 , when determining that the IH fixing electric power could not be successfully increased in Step S 21 .  
       FIG. 8  shows an example of the electric power controlling sequence conducted by the IH heater driving power source  322  during the warm-up operating period.  
      As shown in  FIG. 8 , when the operator turns ON the power switch  24 , the electric power supply from the DC power source  22  is enabled so that the electric power is supplied to the control section  21  from the DC power source  22 . Then, the control section  21  outputs the IH_CONT signal, for commencing the operation for supplying the electric power to the IH heater  321 , and the IH electric power instruction signal, for instructing the amount of the electric power derived from the electric power limit controlling operation mentioned in the above, to the IH heater driving power source  322  as the control signals.  
      At first, the control section  21  commences a pre-operation (start-up term in the drawing) prior to the initializing operation, and outputs the control signal for instructing the IH fixing electric power (1800 W), derived from the electric power limit controlling operation mentioned in the above as the IH fixing electric power to be supplied to the IH heater, to the IH heater driving power source  322 . In response to the control signal, the IH heater driving power source  322  supplies the corresponding amount of electric power to the IH heater  321 . Incidentally, hereinafter, the term of a “process correction” is defined as various kinds of correcting operations for obtaining a stable image, such as a registration correction of an image to be formed, a density correction of the image, etc.  FIG. 8  indicates that the current value I 1 , which is detected during the pre-operation prior to the initializing operation, is 14.7 A, while the current value I 2  is  5 A.  
      During the implementation of the initializing operation and the process correction operation after the pre-operation prior to the initializing operation is completed (during the ON state of them), based on an amount of electric power derived by substituting the amount of electric power necessary for the initializing operation and the process correction operation, the control section  21  outputs the control signal for instructing the IH fixing electric power (1600 W), derived from the electric power limit controlling operation mentioned in the above, to the IH heater driving power source  322 , so that the IH heater driving power source  322  supplies the amount of electric power corresponding to the control signal to the IH heater  321 .  FIG. 8  indicates that the current value I 1 , which is detected during the pre-operation prior to the initializing operation, is 14.3 A, while the current value I 2  is 5 A.  
      During the implementation of only the process correction operation after the initializing operation is completed (during the ON state of the process correction operation and the OFF state of the initializing operation), based on an amount of electric power derived by substituting the amount of electric power necessary for the process correction operation, the control section  21  outputs the control signal for instructing the IH fixing electric power (1700 W), derived from the electric power limit controlling operation mentioned in the above, to the IH heater driving power source  322 , so that the IH heater driving power source  322  supplies the amount of electric power corresponding to the above control signal to the IH heater  321 .  FIG. 8  indicates that the current value I 1 , which is detected during the pre-operation prior to the initializing operation, is 14.5 A, while the current value I 2  is  5 A.  
      Since then, at the time when the IH heater  321  has heated the fixing roller  51  up to the predetermined temperature set as the target value in the mid-course of supplying the IH fixing electric power (1700 W), the control section  21  outputs the control signal for turning OFF the IH_CONT signal to the IH heater driving power source  322 , so as to deactivate the operation for supplying the electric power to the IH heater  321 . Successively from the warm-up mode, the image forming apparatus  200  enters into a standby mode in which the control section  21  intermittently outputs the control signal, for supplying the predetermined IH fixing electric power (950 W) into the IH heater  321 , to the IH heater driving power source  322 .  FIG. 8  indicates that the current value I 1 , which is detected during the pre-operation prior to the initializing operation, is 6.5 A, while the current value I 2  is 5 A.  
      In the configuration described in the foregoing, the AC electric powers fed from the commercial power sources E 1  and E 2  are converted to the DC electric powers having the same voltage under the controlling operations of the control ICs  121 ,  141  of the AC/DC converters  11 ,  13  provided in the electric power combining section  10 , respectively. Then, the DC electric powers having the same voltage are combined into the single DC electric power Vout, which is supplied to each of the electric power loading sections including the DC power source  22 , the electric power loading sections  23 , the apparatus internal heater  31 , the fixing section  32 , etc. Further, the total operation of the image forming apparatus  200  is achieved by supplying an appropriate amount of electric power to each of the electric power loading sections, corresponding to a current operating status of each of the electric power loading sections, under the controlling operations conducted by the control section  21 .  
      As described in the foregoing, according to the embodiments of the present invention, since the AC electric powers supplied from the plurality of commercial power sources can be combined into the single electric power, which is supplied to the electric power loading sections, it becomes possible to supply the amount of electric power, which exceeds the maximum electric power being suppliable from one of the plurality of commercial power sources (AC power sources), to the electromagnetic induction heating device and the other electric power loading sections, which are provided in the image forming apparatus. Specifically, although the electromagnetic induction heating device consumes a relatively large amount of electric power, it becomes possible to stably supply the electric power to the electromagnetic induction heating device, resulting in a stable implementation of the image forming operations.  
      Further, since it is possible to control the amount of electric power to be supplied to the fixing section  32  and the electric power loading sections  23 , so that the total amount of electric power consumed in the fixing section  32  and the electric power loading sections  23  is equal to or lower than a predetermined value and the rated electric power of the image forming apparatus  200 , it becomes possible to safely supply the electric power to the electric power loading sections  23  (including the fixing section  32 .).  
      The details of the configurations and the operations of the aforementioned embodiments can be varied by a skilled person without departing from the spirit and scope of the invention.  
      For instance, although two commercial power sources are employed for the image forming apparatus  200  aforementioned as the embodiment of the present invention, the number of commercial power sources to be employed for the image forming apparatus is not limited to the above, but it is applicable to employ an arbitral number of them. In this case, the electric power combining section  10  is provided with a plurality of AC/DC converters, each of which corresponds to each of the commercial power sources.  
      Further, although the boosting coil  116  and the boosting coil  136  are employed as the voltage converting element in the aforementioned embodiment of the present invention, it is also applicable that a step-down coil (step-down transformer) is employed for this purpose, instead of the boosting coil.  
      Further, although the IH heater  321  is employed as the heating device of the fixing roller  51  in the aforementioned embodiment of the present invention, it is also applicable that either a halogen heater or a ceramic heater is employed for this purpose.  
     MODIFIED EXAMPLE  
      Incidentally, in the embodiment described in the foregoing, although the image forming apparatus, which employs the IH heater  321  for the heating device of the fixing roller  51 , is exemplified as the electric apparatus  100 , the scope of the electric apparatus  100  is not limited to the above. For instance, the present invention can be also applied to a medium-sized image forming apparatus (or a medium-sized printing apparatus), which is operated in a normal office environment for producing a relatively small amount of print products. In such the case, by implementing the present invention for the image forming apparatus, namely by supplying the necessary electric power to the image forming apparatus form a plurality of wall outlets equipped in the office, it becomes possible to effectively solve the problem for satisfying the electric power capacity of the image forming apparatus in the office. Further, it is also applicable that the abovementioned image forming apparatus is a color or monochrome printing apparatus or a copier, which employs the electro-photographic method (and/or employs the tandem method or the other method).  
      In the case that a plurality of optional devices, such as paper feeder, etc., serving as a pre-processing apparatus, a stapler, a puncher, a folder, etc., serving as a post-processing apparatus, are coupled to (or included in) the image forming apparatus to form an integrated image forming system, it is possible to combine a plurality of AC electric powers fed from a plurality of commercial power sources, which are respectively coupled to the plurality of optional devices, into a single electric power so as to supply the single electric power to the electric power loading sections of the image forming apparatus concerned. It is needless to say that the abovementioned image forming system is also included in the scope of the present invention.  
      As described in the foregoing, according to the present invention, the following effects can be attained. 
      (1) Since the AC electric powers supplied from a plurality of AC electric power sources can be combined into a single electric power so as to supply the combined single electric power to the electric power loading section, it becomes possible to supply an amount of electric power exceeding a maximum rated electric power fed from one of the plurality of commercial electric power sources.     (2) Since, by respectively converting the AC electric power units, supplied from the plurality of AC power sources, into DC electric power units and by coupling output ports of the DC electric power units to the single electric power line, the AC electric powers supplied from a plurality of AC electric power sources can be combined into a single electric power so as to supply the combined single electric power to the electric power loading section, it becomes possible to supply an amount of electric power exceeding a maximum rated electric power fed from one of the plurality of commercial electric power sources.     (3) Since it is possible to make the DC voltages of the plurality of DC electric power units coincide with each other, it becomes possible to easily combine the plurality of DC electric power units.     (4) Since the AC input current can be controlled so as to limit the AC input current to a value equal to or lower than the current limit value established in advance, it becomes possible to limit the current value of the DC electric power to be outputted from the AC-to-DC converting section to a value equal to or lower than the DC current limit value.     (5) Since the current limit value can be adjusted, it becomes possible to establish the current limit value corresponding to the service conditions, the operating environments, etc.     (6) Since the amount of the combined electric power, corresponding to a current operation status of the electric power load section, can be supplied to the electric power load section, it becomes possible to improve the efficiency of the electric power supply.     (7) Since the combined electric power can be controlled so as to limit a total amount of the combined electric power, to be supplied to the electric power load section, to a value equal to or lower than a predetermined value, when the rated electric power is established, it becomes possible to limit a total amount of the combined electric power to a value equal to or lower than the rated electric power established, and as a result, it also becomes possible to safely supply the electric power to the electric power load section.    

      Since the AC electric powers supplied from a plurality of AC electric power sources can be combined into a single electric power so as to supply the combined single electric power to the electric power loading section, it becomes possible to supply an amount of electric power, exceeding a maximum rated electric power fed from one of the plurality of commercial electric power sources (namely, AC electric power sources), to the electromagnetic induction heating device and the other electric power loading sections provided in the image forming apparatus. Specifically, despite that the electro-magnetic induction heating device consumes a relatively large amount of electric power, it becomes possible to stably supply the electric power to the electro-magnetic induction heating device concerned, resulting in a stable implementation of the image forming operations.  
      While the preferred embodiments of the present invention have been described using specific term, such description is for illustrative purpose only, and it is to be understood that changes and variations may be made without departing from the spirit and scope of the appended claims.