Abstract:
A device and method are provided for saving power and electricity in a charging device such for external power supplies and battery chargers having a primary circuit and a secondary circuit where a switch is located in the primary circuit and a current sensing device in the secondary circuit to sense when there is a drop in current in the secondary circuit or no current in the secondary circuit because the load or a cell phone is charged and when this occurs the switch in the primary circuit is opened and the primary circuit no longer draws power from the source of power until the switch in the primary circuit is closed by activation of a user of the charging device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in part-application of co-pending U.S. patent application Ser. No. 12/843,151 filed Jul. 26, 2010, entitled Current Sensing Circuit Disconnect Device and Method, which claims priority from U.S. Provisional Application No. 61/228,213 filed on Jul. 24, 2009, the disclosures of those applications being incorporated herein, by reference, in their entireties. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to battery charging devices and external power supplies, hereinafter also jointly referred to as “charging devices”, and methods for disconnecting these charging devices from the mains or the electrical power source in order to eliminate or minimize the flow of current into the charging device when these charging devices and power supplies are still plugged in or connected to the mains, but are no longer charging or providing power to a load. In accordance with the present invention, the charging device is effectively disconnected from the mains when there is a reduction or cessation of current flow sensed in the load circuit. 
     DESCRIPTION OF THE RELATED ART 
     Recently, significant concerns have been raised regarding the environmental impact of wasted electricity. In particular the use of energy by devices standing in idle mode or standby mode has been criticized as using electricity to no purpose, and thus wasting electricity and the valuable resources used to generate it. 
     One particular example of wasted energy occurs with battery chargers and external power supplies (hereinafter charging devices) of all kinds, including those associated with such devices as laptop computers, tablet computers, power tools, electric toothbrushes and portable, mobile and/or cellular telephones, as well as other devices that include a battery to be charged. These charging devices exhibit two distinct low power modes that utilize energy even when there is no load connected to the charging device or battery to be charged. These modes are generally referred to as “standby” and “idle”. “Standby” mode occurs when a charging device is plugged into an outlet or the mains, but there are no batteries or load connected to the charger (i.e., no load connected to the charging device). For example, this occurs when a cell phone charging device is plugged into the wall or the mains, but the cell phone is not connected to the charger. 
     “Idle” mode occurs when no charging is taking place because the battery attached to the charging device is fully charged. In this situation, the charging device is connected between the mains and the load or device to be charged, and the load or device, typically a smart device, is charged and, therefore, is no longer charging. As a result the load draws no current from the charging circuit, but the charging device is still connected to the mains and there is typically power wasted in the primary circuit of the charging device. It is believed that billions of kW hours are currently wasted by battery charging devices running in the standby and idle modes. At present, people, users of charging devices, are being encouraged to physically unplug these charging devices from the mains when not in use, so as to reduce the amount of electricity wasted. 
     What is needed is a device that can be used to cut-off the electricity usage of devices, and in particular, of charging devices, operating in the standby and idle modes or similar modes of operation. 
     What is also needed is a way to reconnect a disconnected charging device when the primary circuit has been disconnected, or is open. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the present invention to provide a device that can be added to, or incorporated in, battery charging devices to disconnect or mechanically break the primary circuit connected to the mains when the charging device is determined to be in a standby or idle mode of operation. 
     It is another object of the invention to reconnect the charging device to the mains after it has been disconnected. 
     In one particular embodiment of the invention, the charging circuit includes a circuit interrupter in the primary circuit and a switch to reconnect the primary circuit to the mains after it is has been interrupted. Such a switch can be located either in the portion of the charging device plugged into the mains, or in or near the portion of the charging device that is plugged into (i.e., mated with) the load or the device to be charged. 
     In one particular embodiment of the invention, the switch is a manual switch that reconnects the charging device to the mains after the charging device circuit has been interrupted, thus effectively disconnecting the charging device from the mains. 
     In another embodiment of the invention, the switch does not require electrical power to close the circuit and reconnect the charging device. 
     In another particular embodiment of the invention, a switch is provided to reconnect the charging device to the mains after the charging device has been disconnected, which switch is closed using a fluidic tube in communication with the switch that interrupts or reconnects the primary circuit. 
     In a further particular embodiment of the invention, a switch is provided to reconnect the primary circuit of the charging device to the mains after the circuit has been interrupted, which switch uses a power source to reconnect the charging device where that power source is either a battery at the charging device or any residual battery power remaining in the load. 
     Other features which are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in a current sensing circuit disconnect device and method, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
     The construction of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of the specific embodiment when read in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which like reference numerals refer to similar elements and in which: 
         FIG. 1  is an isometric view of a charging device in accordance with one particular embodiment of the instant invention and a load, such as a portable cell phone; 
         FIG. 2  is a partial circuit diagram illustrating one particular embodiment of the instant invention wherein current is flowing in the primary side and secondary side of a transformer with the switches in a closed position as long as current flow is above a threshold in the secondary side of the transformer; 
         FIG. 3  shows the partial circuit diagram of  FIG. 2 , having the switches in an open position in accordance with one particular embodiment of the instant invention and no current flowing on the primary side or secondary side of the transformer because the coil does not sense current above a threshold in the secondary side of the transformer; 
         FIG. 4  is a circuit diagram showing one embodiment of the present invention wherein the mechanical switch is an electro-mechanical switch that interrupts the primary side circuit of the charging device in order to open and disconnect the primary side circuit from the mains and a momentary switch in the primary side circuit to reconnect the charging device once disconnected; 
         FIG. 4A  is a circuit diagram substantially similar to that of  FIG. 4 , wherein the switch  325  of  FIG. 4  is represented generically by box  325 ′, which includes an electrical arrangement that can perform the same function as the switch  325  and/or switch  320  of  FIG. 4 ; 
         FIG. 5  is a circuit diagram showing one particular embodiment utilizing an electro-mechanical switch to interrupt the primary side circuit of the charging device in order to open and disconnect the primary side circuit from the mains and a momentary switch in the secondary side circuit to that initiates closing of the electro-mechanical switch to restore current flow to the primary side circuit from the mains; 
         FIG. 6  is a circuit diagram showing a further particular embodiment of the invention wherein the mechanical switch is an electro-mechanical switch in the primary side circuit of the charging device to open and effectively disconnect the primary side circuit from the mains, and a momentary switch in the secondary side circuit to initiate closing of the electromechanical switch in the primary circuit to reconnect the charging device once interrupted and wherein the power for the momentary switch in the secondary side circuit is from a power source in the secondary circuit. 
         FIG. 6A  is an alternative embodiment similar to  FIG. 6 , where the power source in the secondary circuit is a rechargeable battery. 
         FIG. 7  is an isometric view of an alternate embodiment of the charging device of the instant invention wherein the manual switch to activate the closing of the electro-mechanical switch in the primary circuit is located at or near the connector jack that mates with the load. 
         FIG. 8  is a diagram showing a circuit of one embodiment having an electro-mechanical switch in the primary side of the charging device to open and disconnect the primary side circuit from the mains and a fluid pusher at or near the location of the load or the connection jack to activate the closing of the electro-mechanical switch in the primary circuit to reconnect the charging device once disconnected where the fluid pusher connects to a fluidics tube to activate and communicate with the electro-mechanical switch located in the primary side of the charging device. 
         FIG. 9  is a cross section of fluidics tube useful with the circuit of  FIG. 8 . 
         FIG. 10  is a cross section of a charging cord with the fluidics tube there-within. 
         FIG. 11  shows a further embodiment of the invention wherein a charging device is provided for charging a laptop computer. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to  FIGS. 1 to 3 , there is shown an illustration of a charging device  100  made in accordance with one particular embodiment of the instant invention. In the particular example shown in  FIG. 1 , the charging device  100  is a cell phone charger incorporating the traditional mobile phone charger elements. This is not meant to be limiting, as it will be seen how the present invention can be adapted for other kinds of charging devices (i.e., for rechargeable batteries, laptop computers, tablet devices, power tools, rechargeable toothbrushes, etc.) that may operate in standby and idle modes. 
     Referring back to  FIGS. 1 to 3 , the charger  100  includes a plug  110  that permits the charging device  100  to be plugged into, and coupled with, and charged through, a wall outlet (not shown in this Fig. shown in  FIG. 11  wall socket  525 ). Thus, the charging device  100  is connected to mains, which in the United States is 110/120V AC. In the present particular embodiment, a charging device  100 , as shown, takes the 120 AC and down converts it, using a transformer  200  having a magnetic core with a primary coil  202  for connection to the 110/120 volt alternating current in the wall outlet or mains and a secondary coil  204 . The charging device  100  further includes a jack or connector  120 , such as a micro USB connector that connects to a load or cell phone  130 , that provides a DC charging voltage to a load device, which, in the present example, is phone  130 , when the connector  120  is connected in mating receptacle  131  at the base of phone  130 . As such, the charging circuit of the charging device  100  also includes an AC/DC converter (not shown) connected to the secondary of the transformer  200 , to convert the down-converted AC to DC, so as to provide a DC charging current from the connector  120  to the load device—phone  130 . 
     Note that the connector  120  may be any form of connector or jack, as desired to connect the phone  130  to the charger  100 . However, in the presently described embodiment, the connector  120  is illustrated as a micro-USB connector, in accordance with the recently introduced universal cell phone charger agreement. The connector  120  is shown as being at a distance from the body  105  of the charging device  100 , but note that such distance can be as small or as large as desired. In particular, in one embodiment, the cord  115  is only a few inches, and it is envisioned that the plug  110  will be connected to a wall outlet via an extension cord. Alternately, the cord  115  can be several feet in length, so that the plug  110  can be directly plugged into an outlet, while the connector  120  is spaced from the outlet. 
     In accordance with one particular embodiment of the instant invention, the body  105  of the charging device  100  additionally includes a manually actuable, mechanical reset button  140 , that may include an indicator light that the charger is active, that is used to manually reset a switch  145  triggered by the circuit of the instant invention. Referring more particularly to  FIGS. 2 and 3 , the instant invention operates on the principle of mechanically breaking or opening (i.e., interrupting) the electrical circuit between the wall outlet and the primary coil  202  of the transformer  200  when it is determined that no, very low current or a threshold current is being drawn by the secondary coil  204  of the transformer  200 . Once the electrical circuit is interrupted at this location, the circuit will not be able to draw any more current until the mechanical button  140  is manually reset, thus closing the switch  145 . In other words, while the primary circuit is interrupted, no current will be drawn by the charging device  100  until the primary circuit connection is restored by manual actuation of the button  140 . Alternatively, the disconnection and then reconnection of the load can trigger the reconnection or closing of the primary circuit. 
     In the present particular embodiment, a current sensing device such as a current sensing coil  210  or resistance, is placed in close proximity to, or in the path from, the output wires of the secondary coil  204  of the transformer  200 . Alternately, the current sensing device  210  can be placed after the AC/DC converter, if desired. When a mobile phone or cell phone  130  is initially connected to the connector  120 , the charging device  100  is in or will be in the active mode, and current is drawn from the secondary until the battery  135  of the mobile phone  130  connected to the charging device  100  is fully charged. The current sensing device  210  measures the current being drawn over the cord  115  and, for so long as current is being drawn via the connector  120 , the current sensing device  210  provides an output that maintains the switch  145  closed. However, once the battery  135  is fully charged, or the phone  130  is disconnected from the connector  120 , current ceases to be drawn from the secondary coil  204  of the transformer  200  over the cord  115 . Once the current sensing device  210  senses that the current draw has dropped off significantly or even that no current is being drawn by the load device at the connector  120 , the current sensing device  210  signals the switch  145  to open. Thus opening the connection between the primary coil  202  of the transformer  200  and the plug  110 , and interrupting the primary-side circuit. When the switch  145  is open, the charger  100  has an open circuit and no power is used thereby. To restart or close the circuit, the user must reconnect the load device—i.e., phone  130 —in need of a charge by connecting the load device to the jack  120  if not already connected, and manually actuating the reset button  140 , thus closing the switch  145  and reconnecting the primary coil  202  to the household AC mains. The switch  145  breaks or opens the circuit connection between the household mains and the primary coil  202  of the transformer  200  without necessitating the charger  100  being unplugged from the wall or the mains. 
     Additionally, the switch  145  is illustrated as double-pole double-throw mechanical switch in  FIGS. 2 and 3 , but any type of switch or relay that can be operated to open the circuit between the primary coil  202  of the transformer  200  and the plug  110  can be used. For example, a relay can be provided in place of switch  145 , which relay is energized by the output of the current sensing device  210 , and which normally opens when current is not provided from the current sensing device  210  (i.e., when there is no current drawn from the secondary coil  204 ). Further, additional circuitry can be provided to open the switch  145  once the current sensed by the current sensing device  210  drops below a predetermined level. 
     Referring now to  FIG. 4 , there is shown another embodiment of the present invention, wherein the mechanical switch ( 145  of  FIGS. 2 to 3 ) is represented by the electro-mechanical switch/relay K 1 . More particularly,  FIG. 4  is a partial circuit diagram for a charging device  300 , which is substantially similar to the operation of the heretofore described circuit and charging device  100  of  FIG. 1 . Transformer  310  has a primary side  315  and a secondary side  317 . Plug  320  connects the primary side  315  of transformer  310  to the mains (110 volt wall outlet or other wall outlet voltages, such as 220 volts, see a wall outlet as shown in  FIG. 11 ). On the primary side  315 , the primary side circuit  321  includes a primary coil  316 , a manually actuable button  322 , a relay or other electro-mechanical switch K 1  including a relay contact  325 , and plug  320 . 
     The secondary side  317  of transformer  310 , includes a secondary coil  318 , a diode rectifier  330 , a connector or jack J 1  for connection to a load  340 , having a first pin  341  and a second pin  342 , a first resistor  350 , a second resistor  355 , a transistor  360 , a coil  370 , part of the relay K 1 , a secondary side circuit  331  and a filter capacitor  380 . Transistor  360  is configured to operate as a solid-state switch that controls the state of the relay K 1 . For example, when current is being drawn by a load  340 , the transistor  360  is saturated and current flows through the coil  370 , closing the relay contact  325  in the primary side circuit  321 . Please note that the use of a transistor for the switch  360  is not meant to be limiting, as the relay K 1  can be controlled by another type of solid state switch or other similar electrical devices, such as, but not limited to, an FET switch, a zener diode or other switching logic device. 
     Transformer  310  can be a high frequency transformer or a 60 cycle line voltage step down transformer from 110 volts to 5 to 6 volts alternating current. From the secondary side  317  of transformer  310  the current is rectified by diode rectifier  330 . The current then flows through load/device  340  such as a cell phone and the bulk of the current flows through shunt resister  350 . Capacitor  380  filters the rectified DC current to the load  340 . 
     When the voltage is the same across resistor  350  and resistor  355  then at the Q 1  junction of transistor  360  the emitter is on and current flows and magnetic coil  370  is energized, holding contact or switch  325  in a closed position. Coil  370  includes an internal spring that causes the switch  325  to open when current ceases to flow through coil  370 . When switch  325  opens, the primary circuit  321  is interrupted and current no longer flows through the primary side circuit  321 . Current flows in the primary circuit  321  when plug  320  is connected to the mains and when switch or contact  325  is closed due to the relay coil  370  being energized. To start current flow in charging device  300 , plug  320  will be plugged into a power source (i.e., typically a household outlet such as a wall socket  525  shown in  FIG. 11 ). With a load  340  attached to charging device  300  the manual switch  322  (i.e., a momentary switch, in the present example, corresponding to push button  140  of  FIG. 1 ) is engaged with some force or actuation from a user which starts or allows current to flow through the primary side circuit  321 . This primary side current flow will cause current to also flow through the secondary coil  318 . With a load  340  attached to a connector or jack J 1 , current will flow to the load  340  and through the secondary-side circuit  331 , saturating the solid state switch (i.e., transistor  360 ) and energizing the relay K 1 . Current flowing through coil  370  closes the contact or switch  325  and restores current flow through the primary-side circuit  321 , even after momentary switch  322  has reopened. 
     Once current flow in the primary side circuit  321  and secondary-side circuits  331 , has been restored, the transistor  360  will remain in saturation as long as the load  340  continues to be connected to the secondary circuit  331  and the plug  320  is connected to the mains, thus charging the load  340 . Once the load device  340  stops drawing enough current to turn-on the transistor  360  (or drops out of the circuit entirely), the transistor  360  turns off, current stops flowing through the coil  370 , the contact  325  opens and current flow through the primary-side circuit  321  is interrupted until a load  340  is again attached and switch  322  is manually pressed. 
     More particularly, when load  340  is disconnected or there is a drop in current flow in the secondary circuit  331  that meets a threshold current level (i.e., below the turn-on threshold of the transistor  360 ) transistor  360  turns off, causing the magnetic coil  370  to lose power, and switch/contact  325  opens. When switch  325  opens there is no longer current flow in primary-side circuit  321  and power is no longer taken or drawn from the mains. Though charging device  300  is still connected to the power source or plugged into the wall or other power source, there is no current flow in the primary circuit  321  because switch  325  is open and the circuit  321  has been effectively disconnected from the mains. 
     As discussed above, to reconnect the charging device  300  to the mains, switch  325  in primary-side circuit  321  must be re-closed by restoring current flow in the primary-side circuit  321 , via a manual actuation, required from a user, of button  322 . 
     The circuit of  FIG. 4A  is substantially similar to that of  FIG. 4 , except that switch  325 ′ can be any type of switch actuated by coil  370  of the secondary-side circuit  331 . Thus, switch  325 ′ is shown generically in “black box” form, since the switch  325 ′ can be any number of circuits or solid state devices, including the double-pole double-throw switch  145  described in connection with  FIGS. 2 and 3 . 
     Referring now to  FIGS. 5 and 7 , there is shown a circuit in accordance with another embodiment of the invention. In the circuit of  FIG. 5 , the manually actuated button or momentary switch  450  is located on the connector or jack  420  in close proximity to the load  340 —in the current example, a cell phone  430 , as shown more particularly in  FIG. 7 . Jack  420  plugs into receptacle  421  at the base of phone  430 . In this embodiment, the charging device  300  shown in  FIGS. 5 and 400  in  FIG. 7  has an activation switch  450  that is located at the point of use where the jack  420 , the distal end of the charger cord  415  is engaged or plugged into load  340  for example a cell phone  430  having a rechargeable battery  435 . In this embodiment, the plug  320  can remain plugged into the mains. When the load  340  is disconnected from the connector  420  of the secondary-side circuit  331 , the transistor  360  turns off and the relay K 1  is de-energized (i.e., current stops flowing through coil  370  and contact  325  opens). Thus, the primary-side circuit  321  is interrupted (i.e., opens) when switch  325  opens, as previously described in connection with  FIG. 4 , and the charging device  300  is effectively disconnected from the mains though plug  320  remains plugged into the mains or wall socket. 
     When it is desired to charge the rechargeable batteries  435  of load  430 , the connector  420  is plugged into a mating connector  421  of the load  430 , and activation switch  450  is depressed when the load  340  or phone  430  is connected to the jack  420  and to the secondary circuit  331 . Then the primary circuit  321  will be energized with current flow and the charging device will begin charging the load. 
     In the embodiment illustrated in  FIGS. 5 and 7 , where the activation switch  450  is located at the distal end of charger cord  425 , a circuit includes switch  450  and a third resistor  357 . This circuit obtains power from the device  430  ( FIG. 7 ) or load  340 , via a pin  343  on the connector or jack  420 . For example, residual power in the batteries  435  of a load  340  such as a cell phone  430  is provided to the base of the transistor  360  via a pin  343  of the connector  420  and a wire connection  343 ′ closed by actuation of momentary switch  450 . Though the cell phone  430  may have lost its full charge and may not be usable as a cell phone because the battery  435  has become substantially discharged and no longer a sufficient power threshold to operate the phone  430 . However there is likely in most situations a sufficient threshold or residual voltage remaining in the battery  435  to provide sufficient current for an instant, to the base of the transistor  360  when switch  450  is activated or pressed, so as to activate coil  370  and close switch  325 . This restores the current flow through the primary-side circuit  321  and activates the charging device  300  to charge the load  340  or cell phone  430 . 
     Referring now to  FIGS. 6 and 7 , there is shown a further embodiment of the present invention. In the present embodiment, the activation switch  450  is at the distal end of cord  415 , as shown in  FIG. 7 , but the power provided to the base of transistor  360  by the closing of the switch  450  is provided by a small battery  460 , such as a hearing aid battery or other long life battery in the circuit of  FIG. 6 . This battery  460  can be located in the area of the jack  420  or in the casing or housing  401  for the other electrical components of charger device  400 . In this embodiment, when switch  450  is manually closed, the current in the battery  460  is provided to the base of the transistor switch  360 , for a moment, momentarily energizing the coil  370  and initiating the closing of the switch  325 . Once switch  325  is closed, current flow is restored through the primary-side circuit  321  and, consequently, through the secondary-side circuit  331 , despite the momentary switch  450  opening and the battery  460  dropping out of the circuit. Thus, power to the charging device  300  can be interrupted and restored without ever removing or reinserting the plug  320  into the wall outlet or mains. 
     Referring now to  FIGS. 6A and 7 , there is shown another alternate embodiment of the invention, similar to that of  FIG. 6 , wherein the activation switch  450  is at the distal end of cord  415 , but wherein the power applied to the circuit by manually closing the momentary switch  450  is provided by a rechargeable battery  465 . Additionally, the circuit  331  of  FIG. 6A  includes a charging circuit  462  for recharging the rechargeable battery  465  when current flows through the secondary circuit  331  to the load  340 . In this way, rechargeable battery  461  will have sufficient power at all times to turn-on transistor  360  and energize the coil  370  when switch  450  is activated or closed. 
     Referring now to  FIGS. 7-10 , there is shown a further embodiment of the present invention, wherein the activation switch  450  at the distal end of cord  415  of  FIG. 7  is provided as an activation switch or fluid pusher  403  at the connector to load  340  of  FIG. 8 . In the present particular embodiment, the switch or contact  325  is physically pushed and forced closed by a mechanical pusher  402 , actuated by a fluid within a fluidic tube  401 , initiated by pushing the fluid pusher  403 . The fluid, may be air or a liquid such as oil or other liquids, can be contained in a fluidic tube  401  in fluid communication with the fluid pusher  403 , which could be a bulb or similar device located at a first end of tube  401 . Actuation of the fluid pusher forces the fluid to apply pressure to the mechanical pusher  402  at a second end of tube  401 . Tube  401  can be housed within charging cord  415 ′ as shown in  FIG. 10 . The cross section of tube  401  taken from lines A-A in  FIG. 8  is shown in  FIG. 9  and a cross section of a charging cord  415 ′ with electrical connectors  341  and  342  for the load  340  and the fluidic tube  401  is shown in  FIG. 10 . Bulb  403  and pusher  402  are in fluidic communication through tube  401  such that any movement of fluid caused by squeezing or pressing bulb  403  causes a similar movement at pusher  402  that for example could push switch  325  to a closed position or an arm connected to switch  325  that would close switch  325  and close the circuit  321  to start current flow in primary circuit  321 . 
     Referring now to  FIG. 11 , there is shown a further embodiment of the invention wherein a charging device  505  is provided for charging a laptop computer  500 . The charging device  505  operates substantially similarly to the charging devices described in connection with  FIGS. 4 ,  6  and  6 A, wherein the manually actuable reset button  530  is disposed at the charging device  505 , but wherein the charging device is remote from the wall socket  525 , and thus more accessible. More particularly, button or switch  530  is remote from receptacle  525  in wall socket  525 . Laptop  500  includes a keyboard  501 , a display screen  502  and a receptor or jack  503  for receiving a mating jack  510  from charging device  505 . Charging device  505  includes, at a first side, electrical cable  515  at its distal end  517  connected to an electrical plug  519  and prongs  410  to plug into an electrical source of energy, like a wall outlet  525  having a first receptacle and a second receptacle  526  for receiving plug  519 . Charging device  505  has at its other end, an electrical cable  516  with a jack  510  at its distal end. Jack  510  is configured to mate with receptacle  503  on the laptop computer  500 . 
     Additionally, the charging device  505  includes a manually actuable button  530  that, when depressed, will restore current flow to the primary-side circuit, as described in connection with the embodiments of the invention discussed hereinabove. 
     Generally, the present invention includes a charging device having a plug and a jack for connection to a load such as a cell phone. Initially, the plug will be plugged into a wall outlet or other power source and the jack will be plugged into the load or cell phone and then the switch or button will be depressed in order to cause current to flow in the primary transformer circuit of the charging device. When the load is charged or is disconnected, the current flow in the secondary transformer circuit will drop down to a threshold level causing the switch in the primary circuit to open and the charging device will no longer draw power or current from the electrical source or mains. When it is desired to use the charging device again the above will be repeated. If the plug is still plugged in the wall then that step of plugging in the plug will not have to be repeated and if the load is still connected to the charging device, the plug will not have to be electrically attached again. However, the switch will be required to be activated or pressed in order to cause current to flow in the primary circuit again. 
     Further the present invention is a method for disconnecting a charging device including a transformer, having a first switch in the primary-side circuit of the primary coil of the transformer; and opening the switch when a current sensing device determines there has been a decrease of current flow in the secondary-side circuit of the transformer, and manually actuating a switch to permit current flow in the primary-side circuit. 
     The present invention is also a charging device, having a transformer including a primary-side circuit and a secondary-side circuit, with the primary-side circuit including a first switch having an open state that opens said primary-side circuit to current flow and a closed state that permits current flow through said primary-side circuit, the secondary-side circuit including a connector for connection to a load for charging an energy storage device in said load, and a switching device in said secondary-side circuit for switching the first switch to its open state when the current drawn by said load is below a preset threshold. 
     Note that the above-described embodiments are exemplary and that the above invention is not meant to be limited only to its preferred embodiments. It can be seen that other modifications can be made to the preferred embodiments and still be within the spirit of the present invention.