Patent Publication Number: US-2020288588-A1

Title: Portable power supply

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/120,574 filed Apr. 24, 2020 titled “Portable Power Supply,” which claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 62/553,693, filed Sep. 1, 2017, titled “Portable Power Supply.” 
     This application is related to U.S. patent application Ser. No. 14/876,458 which is incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This application relates to a portable power supply system and method for providing portable power. In one implementation, the system is configured to receive DC power from a DC power source and AC power from an AC power source. The system is configured to output power from the DC power source and/or the AC power source. 
     BACKGROUND 
     Various types of electric power tools are commonly used in construction, home improvement, outdoor, and do-it-yourself projects. Conventional power tools generally fall into two categories—corded power tools that are powered by an AC power source, e.g., an AC mains line, and cordless power tools that are powered by one or more DC power sources, e.g., a rechargeable battery pack. 
     Corded power tools generally are used for heavy duty applications that require high power and/or long runtimes, such as heavy duty sawing, heavy duty drilling and hammering, and heavy duty metal working. However, as their name implies, corded power tools require the use of a cord that can be connected to an AC power source. In many applications, such as on construction sites, it is not convenient or practical to find a continuously available AC power source and/or AC power must be generated by a portable power supply such as a generator, e.g. gas powered generator. 
     Cordless power tools generally are used for lighter duty applications that require low or medium power and/or short runtimes, such as light duty sawing, light duty drilling, and fastening. As cordless tools tend to be more limited in their power and/or runtime, they have not generally been accepted by the industry for all applications. They are also limited by weight since the higher capacity batteries tend to have greater weight, creating an ergonomic disadvantage. 
     Generally, conventional power tool battery packs may not be able to run conventional corded power tools or other corded electrical devices, while untransformed AC power may not be able to be used to run cordless power tools. Further, the battery packs for cordless power tools may require frequent recharging, may be expensive to purchase, and may be cumbersome to manage on a large construction site. 
     There are portable power supplies (sometimes referred to as inverters) that utilize batteries to provide power to an inverter which in turn provides AC output power to operate corded power tools designed to operate from wall/AC mains line power. These conventional battery based portable power supplies utilize integral batteries or conventional sealed lead acid (SLA) batteries. Although this allows the user to operate the corded power tool without having access to wall/AC mains line power, it does not allow the user to remove the battery from the portable power supply and use the battery to operate a set of cordless power tools. In other words, conventional systems provide for a battery pack for operating a set of cordless power tools and a battery for operating the battery based portable power supply wherein the battery pack for operating the set of cordless power tools cannot supply power to the portable power supply and the battery for operating the portable power supply cannot supply power to the cordless power tools. In the power tool industry, it is desirable to be able to use cordless power tool battery packs to drive the corded power tools. In addition, it is desirable to use cordless power tool battery packs to run non-power tool electrical device that are also designed to operate from wall (AC, mains line) power. 
     Another aspect of this disclosure is operating electrical devices that normally operate on mains line power, for example corded power tools, to simultaneously use the mains line power and battery power to increase the power available to perform work. 
     Traditionally the mains line power supply in the US is limited to 15 or 20 amps from a 120 volt AC power receptacle. Because the 15 amp branch circuit is relatively common conventional devices that plug into a standard 120 volt AC power receptacle are designed around this 15 amp limit. Such a design limits the input power from the AC mains line to about 1800 watts and thus the output power of a typical motor will be about 1200 watts, taking into account various system efficiencies. For short durations these power levels may be exceeded, but at the risk of opening the circuit protection device associated with the branch circuit supplying the load. There are many power tool applications that would benefit from the power beyond what can be effectively delivered through the 120 volt AC power receptacle. Currently the only options for these applications are to utilize a special receptacle, a generator with special receptacles or alternative motive power such as an internal combustion engine. This aspect presents a method and system to deliver higher operating power without special receptacles or internal combustion engines attached to the electrical device. 
     SUMMARY 
     According to an embodiment, a power supply apparatus is provided including a housing, at least one battery receptacle provided on the housing for receiving at least one removable battery pack, an inverter configured convert a direct-current (DC) signal from the at least one battery pack to an alternating-current (AC) signal, and a controller configured to apply a pulse-width modulation (PWM) signal to the inverter to shape the AC signal with a lower harmonic distortion relative to a square wave. In an embodiment, for each full cycle of the AC signal, the controller is configured to set the duty cycle to approximately 100% within a first period corresponding to a peak area of the AC signal, set the duty cycle to less than approximately 100% but greater than approximately 0% within a second period in which the AC signal transitions from the peak to a zero-cross following the first period, and set the duty cycle to approximately 0% within a third period corresponding to the zero-cross of the AC signal following the second period. 
     According to an embodiment, the power supply apparatus further includes a filter configured to shape the AC signal by integrating high frequency components thereof. The AC signal, after modulation and filtering, includes a first period corresponding to a peak area of the AC signal within which the AC signal is maintained at a peak voltage, a second period in which the AC signal is sloped to transition from the peak to a zero-cross following the first period, and a third period corresponding to the zero-cross of the AC signal following the second period within which the AC signal is maintained at zero. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front elevation view of an exemplary embodiment of a portable power supply of the present disclosure. 
         FIG. 2  is a rear elevation view of the portable power supply of  FIG. 1 . 
         FIG. 3  is a first side elevation view of the portable power supply of  FIG. 1 . 
         FIG. 4  is a second side elevation view of the portable power supply of  FIG. 1 . 
         FIG. 5  is a top plan view of the portable power supply of  FIG. 1 . 
         FIG. 6  is a bottom plan view of the portable power supply of  FIG. 1 . 
         FIG. 7  is a section view along  7 - 7  of the portable power supply of  FIG. 1 . 
         FIG. 8  is a section view along  8 - 8  of the portable power supply of  FIG. 1 . 
         FIG. 9  is a section view along  9 - 9  of the portable power supply of  FIG. 4 . 
         FIG. 10  is a perspective exploded view of the portable power supply of  FIG. 1 . 
         FIG. 11  is another perspective exploded view of the portable power supply of  FIG. 1 . 
         FIG. 12  is another perspective exploded view of the portable power supply of  FIG. 1 . 
         FIG. 13  is another perspective exploded view of the portable power supply of  FIG. 1 . 
         FIG. 14  is another perspective exploded view of the portable power supply of  FIG. 1 . 
         FIG. 15  is a top plan view of the interior of the portable power supply of  FIG. 1 . 
         FIG. 16  is a graph illustrating an exemplary sine wave. 
         FIG. 17  is a graph illustrating an exemplary square wave. 
         FIG. 18  is a graph illustrating an exemplary modified sine wave. 
         FIG. 19  is a block diagram of an exemplary portable power supply and a corded electrical device. 
         FIG. 20  is a graph illustrating an exemplary enhanced modified sine wave (PWM enhanced). 
         FIG. 21  is a graph illustrating an exemplary filtered enhanced modified sine wave. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 through 6  illustrate an exemplary embodiment of a portable power supply (PPS) system  100  of the present invention. The PPS system  100  includes a housing  12 . The housing  12  may include an upper housing portion  14  and a lower housing portion  16 . The PPS system  100  may also include two side handles  18 ,  20  and a front handle  22 . In the exemplary embodiment of the PPS system  100 , there are four battery pack receptacles  24   a ,  24   b ,  24   c ,  24   d  (BPR 1 , BPR 2 , BPR 3 , BPR 4 ). The battery pack receptacles  24  may also be referred to as battery interfaces or battery ports. The PPS system  100  may also include a battery pack indicator  32 . The battery pack indicator  32  may be an LED or other type of light emitting device. The battery pack indicators  32  indicate the status of a battery pack  26  coupled to the associated battery pack receptacle  24 . The PPS system housing  12  may also include an airflow input port  34  and an airflow output port  36  to enable air to flow into and out of the PPS system  100 . The PPS system  100  may also include an alternating current (AC) output connector  38 . The AC output connector  38  may take the form of a three-prong receptacle. The PPS system  100  may also include an inverter start (or activation) switch  40 . The PPS system  100  may also include an inverter operation indicator  42 . The inverter operation indicator  42  may be in the form of an LED. The inverter operation indicator  42  will be illuminated when an inverter  44  of the PPS system  100  is active. The PPS system  100  may also include an AC input connector  46 . The AC input connector may take the form of a three-prong plug. 
       FIG. 7  illustrates a first section view of the PPS along lines  7 - 7  of  FIG. 1 .  FIG. 8  illustrates a second section view of the PPS along lines  8 - 8  of  FIG. 1 .  FIG. 9  illustrates a third section view of the PPS along lines  9 - 9  of  FIG. 4 .  FIG. 15  illustrates a fourth section view of the PPS along lines  15 - 15  of  FIG. 1 . These section views illustrate many of the internal components of the PPS. 
       FIGS. 10-14  illustrate exploded views of the PPS system  100 . As illustrated in the figures, the PPS system  100  may include a first printed circuit board PCB 1   48  and a second printed circuit board PCB 2   50  for mounting various components of the PPS system  100 . The PCB 1   48  is used primarily to mount components related to the inverter  44  and the PCB 2   50  is used primarily to mount components related to the charging system. 
     The PPS system  100  includes a heat sink  52  mounted on the PCB 1   48 . The heat sink  52  may be an elongated tube having a longitudinal axis and an internal passage or channel extending along the longitudinal axis from a first end  58  of the heat sink  52  to a second end  62  of the heat sink  52 . The PPS system  100  includes, for example, a plurality of inductors  53  and FETs  54  mounted to the heat sink  52 . The inductors  53  and FETs  54  generate heat during operation of the inverter  44 . The heat sink  52  sinks the heat generated by the inductors  53  and FETs  54 . The PPS system  100  includes a fan  56  positioned between the airflow input  34  and a first end  58  of the heat sink  52 . The PPS system  100  includes a first heat sink coupler  60  connecting the first end  58  of the heat sink  52  to the fan  56  and an opening in the lower housing portion  16  and a second heat sink coupler  61  connecting a second end  62  of the heat sink  52  to the airflow output  36 . The heat sink  52  and the heat sink couplers  60 ,  61  provide a sealed path for air to flow from the airflow input  34 , through the internal passage of the heat sink  52  and to the airflow output  36  to move heat generated by the inductors  53  and FETs  54 . The PPS system  100  includes an inverter microprocessor or microcontroller circuit  64  mounted to the PCB 1   48  for monitoring and controlling the inverter  44 . 
     The PPS system  100  includes a plurality of battery terminal blocks  66  mounted on the PCB 2   50 . There is one battery terminal block  66  for each battery pack receptacle  24 . The PPS system  100  includes a plurality of chargers  68  and associated components mounted on the PCB 2   50 . There is one charger  68  and associated components for each battery pack receptacle  24 . 
     Floating Middle Mounting Plate 
     In order to provide a compact system that provides both a charging system for charging a plurality of removable battery packs and an inverter system for converting DC power to AC power it is imperative to provide a compact printed circuit board system. The present invention presents a method for suspending a first printed circuit board above a second printed circuit board. An objective is to allow the two printed circuit boards inside the PPS system to each extend horizontally and yet be stacked vertically relative to each other. The printed circuit boards also need to be separated from each other enough to allow for heat dissipation and the mounting of the various necessary components. 
     The exemplary PPS system  100  is an electronic device having two main functions: 1) charge a plurality of removable battery packs  26  simultaneously (the exemplary embodiment includes the ability to charge four (4) battery packs simultaneously) and 2) convert the DC power of the removable battery packs  26  into 120V AC power. 
     To accomplish these functions, the unit contains two primary large printed circuit boards—one for the charging function and one for the inverter function. The system is similar to existing battery pack chargers in that there is a printed circuit board that includes components to convert the incoming AC power to DC power to charge and monitor the battery packs. For the PPS system  100 , the unit can charge up to four (4) battery packs  26  simultaneously. The charging printed circuit board  50  is therefore much larger than a circuit board of a charger designed to charge a single battery pack. Including an inverter function in the PPS requires a second printed circuit board  48 . Due to the layout and requirements of the PPS system  100 , the inverter printed circuit board  48  is positioned below and parallel to the charging printed circuit board  50 . 
     A floating middle plate  70  supports the charging printed circuit board PCB 2   50 . The middle plate  70  rests on a set of supports  72  that are part of the lower housing portion  16 . The middle plate  70  is supported around its perimeter only. The shape and size of the inverter printed circuit board PCB 1   48  is such that the inverter printed circuit board PCB 1   48  sits within the geometric shape defined by the set of supports  72  to enable the set of supports  72  to support the middle plate  70 . The middle plate  70  includes screw hole features for both the charging printed circuit board  50  on the top surface as well as screw hole features for a smaller AC filter board to be suspended underneath the middle plate  70 . Additional screw hole features are included to attach various devices used for securing and locating wires. In addition to the pad features on the lower housing portion  16  that support the middle plate  70 , there are two pins that protrude downward from the upper housing portion to locate the middle plate in the proper relationship to the upper housing portion. The middle plate  70  is termed “floating” because it rests on the set of supports  72  and is not rigidly fastened to the lower housing portion  16 . The charger printed board  50  supports the battery pack terminal blocks  66 . In order to position the battery pack terminal blocks  66  relative to the upper housing portion  14  and the battery pack receptacles  24 , the middle plate  70  is not secured to the lower housing portion  16  and the locating pins for the middle plate  70  come from the upper housing portion  14 . The middle plate  70  is responsible for maintaining the shape of the charger printed circuit board  50  during drop and vibration events in order to prevent damage to the components of the charger printed circuit board  50 . As it is not possible to support the center of the middle plate  70  from below (due to the positioning of the inverter printed circuit board PCB 1   48 ), the middle plate  70  includes a plurality of “U” shaped channels  80  that run parallel to a long axis  82  of the middle plate  70  to prevent flexing and bending of the middle plate  70  and the charger printed circuit board  50 , as much as possible. 
     The floating middle plate  700  allows location features to be added to upper housing portion  14 . When the upper housing portion  14  is coupled to the lower housing portion  16  the middle plate  70  can move to align the terminal blocks  66  (mounted to middle plate  70 ) with the battery pack receptacle  24  of the upper housing portion  14 . 
     Heat Sink as Structural Element 
     Due to the size of the PPS system  100  and the internal printed circuit boards  48 ,  50 , it is preferred to include a system to support the printed circuit boards housed inside the PPS system to prevent them from becoming damaged. The printed circuit boards  48 ,  50  and the components mounted thereon, need to withstand standard product requirements including drop and vibration standards. If the printed circuit boards  48 ,  50  are subjected to large amounts of vertical deflection during these events, the mounted components could break off or become damaged and hinder the operation of the system. The PPS housing is a relatively large, open five sided box constructed from plastic materials and is limited in the amount of structure it can provide. 
     The inverter printed circuit board PCB 1   48  includes many heavy electronic components that are susceptible to damage due to flex when dropped. In addition, many of the various electronic components necessary to implement an inverter generate significant amounts of heat during operation. As such, the PPS system  100  requires a heat sink to collect and dissipate the generated heat. In the exemplary embodiment disclosed in this application a heat sink  52  is included that is mounted on the inverter printed circuit board PCB 1   48 . The heat sink  52  may be made of aluminum. 
     The inverter printed circuit board PCB 1   48  has a generally planar shape (forms a plane). The heat sink is positioned relative to the inverter printed circuit board PCB 1   48  such that the longitudinal axis of the heat sink is parallel to the plane formed by the inverter printed circuit board PCB 1   48 . The electronic components that generate heat, such as the inductors  53  and the FETs  54  are attached to the heat sink  52 . The heat sink  52  may have a rectangular cross section with a hollow center  86 . The heat sink  52  may include a plurality of ribs  88  crossing the hollow center. An electric fan  56  draws air from outside the PPS system  100  into the PPS system  100  through the airflow input  34  and forces it into one end of the heat sink  52 . The air flows though the heat sink  52 , collects heat from the electronic components and is then exhausted out the other end of the PPS system  100  through the airflow output  36  to outside the PPS system  100 . 
     The structural/physical shape and material of the heat sink  52  provide rigidity to the inverter printed circuit board PCB 1   48 . The heat sink  52  is first attached to the inverter printed circuit board PCB 1   48  using a plurality of screws through the printed circuit board PCB 1   48 . Once the heat sink  52  and the inverter printed circuit board  48  have been installed into the lower housing portion  16 , a second set of screws are used to secure the heat sink  52  to the lower housing portion  16 . This provides a direct structural link between the lower housing portion  16  and metal heat sink  52 . This is in addition to rubber mounting points used elsewhere to mount the inverter printed circuit board  48  to the lower housing portion  16 . In the event of a drop or vibration, the structural heat sink  52  reduces the amount of deflection in the lower housing portion  16  and the inverter printed circuit board  48 . This in turn limits the movement of the components mounted to the inverter printed circuit board PCB 1   48  and the charger printed circuit board PCB 2   50  and helps protects them from damage. 
     As such, the heat sink  52  serves the dual purpose of heat sink and structural element. No additional components need to be added to provide rigidity to the assembled PPS system  100  to prevent flexing of the lower housing portion  16 . Mounting the heat sink  52  to the inverter printed circuit board  48  and the lower housing portion  16  also provides an improved rigidity to the middle plate  70  above the heat sink  52  to limit deflection of the charger printed circuit board PCB 2   50 . 
     Enhanced Modified Sine Wave Control of Inverter 
     There are multiple hardware and software control methodologies employed in conventional power inverters to produce alternating current output waveforms. The most common of these methodologies produce several types of wave forms including, but not limited to, a pure sine wave, a square wave, and a modified sine wave (sometimes referred to as modified square wave). It is well known that AC line power (power provided by public utilities) is typically sinusoidal, an inverter which produces a sine wave output, as illustrated in  FIG. 16 , would be considered optimal. However, pure sine output inverters are expensive to produce and are relatively heavy as they generally employ costly and heavy transformers. Less expensive inverters that produce square waves or modified sine waves are limited by the sensitivities of the potential coupled loads to non-sinusoidal power waveforms. An enhancement to these inverter configurations is desirable, to allow for economical production, while minimizing load sensitivity to output waveforms. 
     The simplest power inverter to produce and control employs a square wave topology. The output of a square wave inverter switches on and off symmetrically about a zero potential point (see  FIG. 17 ). While this design is relatively inexpensive and easy to implement, it has the greatest potential for problems. Sophisticated loads with sensitivity to wave shape and to detection of zero-crossing are subject to problems when coupled with a square wave inverter. 
     An improvement over the square wave inverter is the modified sine wave inverter. A modified sine wave inverter produces an output waveform that is an incremental improvement over the square wave, in that it provides a significant dwell time at the zero potential, instead of a direct switching from the highest to lowest potential. (see  FIG. 18 ) This provides a lower harmonic distortion relative to a square wave, and allows for higher peak voltage output, given the same RMS voltage output. 
     However, the modified sine wave can still present a challenge to some loads which are sensitive to the wave shape of the line source. Among these, are DeWALT AC power tools which include GACC intelligent control. These loads are sensitive to wave shape (and in the case of DeWALT GACC tools, are particularly sensitive to the characteristics of the zero-crossing of the output waveform). An enhancement to traditional modified sine wave control is therefore needed, to provide a more gradual zero crossing, allowing such loads to function on the more economically-produced Modified Sine technology. 
     In the present invention, the sustained dwell at zero potential in a traditional modified sine wave inverter configuration is enhanced by intelligent control to more closely approximate the characteristics of a true sine waveform. This is achieved by employing pulse-width modulation to produce an intermediate proportional output at various points of the output wave, to provide more gradual transition at the zero crossing. 
     While it would be possible to employ pulse width modulation (PWM) to synthesize a large number of different modulation points throughout the wave, producing in essence, a continuum that very closely approximates the sinusoidal wave, there are several disadvantages to this approach. Firstly, the higher the number of synthesized points in the wave, the higher the necessary PWM frequency. The higher the PWM frequency, the greater the number of switching events per unit time (and therefore the higher the switching losses for the system as a whole). Switching losses produce higher temperatures in the system power semiconductors. Secondly, it is advantageous to provide the switching events which synthesize the necessary gradual transitions, only at lower potentials, producing less electrical switching noise. 
     For these reasons, it is advantageous to minimize the switching to only that which is necessary to maximize the desired effect (more gradual transitions where the velocity of the wave is highest). 
       FIG. 19  illustrates schematic block diagram of an exemplary PPS system  100 . The PPS system  100  includes four battery pack receptacles BPR 1 , BPR 2 , BPR 3 , BPR 4   24   a ,  24   b ,  24   c ,  24   d . Each of the battery pack receptacles  24  is configured to receive a removable battery pack  26 . The removable battery pack  26  couples to the battery pack receptacle  24  to electrically and mechanically couple the battery pack  26  to the PPS system  100 . The PPS system  100  includes an inverter  44 . The inverter  44  is an electrical/electronic circuit configured to convert a DC power signal to an AC power signal. The PPS system  100  also includes a booster  134 . The booster  134  is an electrical/electronic circuit configured to boost a DC power signal from a first voltage level to a second voltage level. For example, the booster  134  may boost an 80 volt DC signal to a 170 volt DC signal. The PPS system  100  also includes an inverter microcontroller circuit  64 . The inverter microcontroller circuit  64  monitors and controls the booster  134  and the inverter  44 . 
     Each of the battery pack receptacles  24  is electrically coupled to a PPS voltage bus. The battery pack receptacles  24  are coupled to each other in series on the voltage bus. As such, when the removable battery packs  26  are coupled to the battery pack receptacles  24 , the battery packs  26  are coupled in series. In other words, for example, if four 20 volt battery packs  26  are coupled to the PPS system  100 , then the voltage bus is at 80 volts DC. The voltage V 1  is the series voltage of the battery packs  26  coupled to the PPS system  100 . In this instance V 1  equals 80 volts. 
     The voltage bus is coupled to the booster  134 . As such, the booster  134  can boost the input voltage (from the voltage bus) to the required voltage for the inverter  44 , for example 170 volts DC. The inverter  44  receives the boosted DC voltage from the booster  134 . In the exemplary embodiment, the inverter  44  generates a modified sign wave, as illustrate in  FIG. 18 . 
     The inverter microcontroller circuit  64  provides a PWM signal to the inverter  44  to generate an enhanced modified sine wave, as illustrated in  FIG. 20 . 
     In a preferred, exemplary embodiment of an enhanced modified sine wave the inverter microcontroller circuit  64  employs PWM at 0%, 20%, 80%, and 100% to synthesize gradual transitions at highest velocity portions of the wave, while leaving the maximum possible unswitched portion (providing a good balance of wave fidelity and thermal performance). 
     As illustrated in the exemplary waveform of  FIG. 20 , the waveform produced by the inverter  44  has a period Z. During a portion A of the period Z, the inverter microcontroller circuit  64  employs a 0% PWM. During a portion B of the period Z, the inverter microcontroller circuit  64  employs a 20% PWM. During a portion C of the period Z, the inverter microcontroller circuit  64  employs an 80% PWM. During a portion D of the period Z, the inverter microcontroller circuit  64  employs a 100% PWM. During a portion E of the period Z, the inverter microcontroller circuit  64  employs an 80% PWM. During a portion F of the period Z, the inverter microcontroller circuit  64  employs a 20% PWM. During a portion G of the period Z, the inverter microcontroller circuit  64  employs a 0% PWM. During a portion H of the period Z, the inverter microcontroller circuit  64  employs a 20% PWM. During a portion I of the period Z, the inverter microcontroller circuit  64  employs an 80% PWM. During a portion J of the period Z, the inverter microcontroller circuit  64  employs a 100% PWM. During a portion K of the period Z, the inverter microcontroller circuit  64  employs an 80% PWM. During a portion L of the period Z, the inverter microcontroller circuit  64  employs a 20% PWM. And during a portion M of the period Z, the inverter microcontroller circuit  64  employs a 0% PWM. 
     The PWM waveform as seen in  FIG. 20 , when produced by the PPS system  100  as a whole, is subjected to a hardware output filter  138 . The filter  138  effectively integrates the comparatively higher frequency components of the PWM′d waveform of  FIG. 20 , providing a final output waveform that effectively approximates a sine wave. A first order filtered PWM waveform can be seen in  FIG. 21 . 
     In an exemplary embodiment, the fan  56  operates as follows. If the output of the PPS system  100  is greater than 1000 watts then the fan  56  is turned ON or if the heat sink  52  temperature is greater than 42 degree Celsius then the fan  56  is turned ON. 
     In alternate embodiments, the inverter microcontroller circuit  64  and/or booster  134  may sense the voltage on the voltage bus (based on the number of battery packs  26  coupled to the PPS system  100 ) and adjust the boost of the booster  134  to achieve the voltage required by the inverter  44 . For example, if there are only three 20 volt battery packs  26  coupled to the PPS system  100 , the booster  134  will have to boost the voltage bus more than if there were four 20 volt battery packs  26  coupled to the PPS system  100 . 
     The inverter  44  will begin operation when the inverter activation switch (IAS)  40  is activated by a user. The IAS  40  is coupled to the first battery pack receptacle BPR 1   24   a . If a battery pack  26  is coupled to the BPR 1   24   a , a voltage will be presented to a latch  140 . The latch  140  will close the converter switch SW 2 . By closing the converter switch SW 2 , a voltage will be presented to an inverter DC-DC converter  142 . The inverter DC-DC converter  142  will present a voltage to the inverter microcontroller circuit  64 , thereby “waking up” the inverter microcontroller circuit  64  enabling the inverter microcontroller circuit  64  to operate. The inverter DC-DC converter  142  also presents an operation voltage to the fan  56 , the booster  134  and the inverter  44 . Once the inverter microcontroller circuit  64  receives the wake up voltage, the inverter microcontroller circuit  64  sends a signal to the latch  140  to keep the latch  140  closed and thereby keep the converter switch SW 2  closed to maintain operation of the inverter microcontroller circuit  64 . 
     No Charge while Discharge or No Discharge while Charge 
     In systems that include at least one charger for charging at least one battery pack—wherein the at least one charger receives charging power from an AC source—and an inverter for providing an AC output power signal derived from the at least one battery pack, it is preferred that the at least one charger and the inverter do not operate simultaneously. To this end, the instant application discloses a system that (1) prevents the charger from operating when the inverter is active and continues to operate the inverter and/or (2) disables the inverter when the inverter is active when a user attempts to use the charger and allows the charger to begin charging and/or (3) prevents the inverter from operating when the charger is active and continues to operate the charger and/or (4) disables the charger when the charger is active when a user attempts to use the inverter and allows the inverter to begin operation. 
     Referring to  FIG. 19 , as noted above, the portable power supply system  100  includes a plurality of battery pack receptacles  24  (BPR). The embodiment of  FIG. 19  includes four battery pack receptacles  24   a ,  24   b ,  24   c ,  24   d —BPR 1 , BPR 2 , BPR 3 , BPR 4 . Alternate exemplary embodiments of a portable power supply system  100  may include more or fewer battery pack receptacles  24 .  FIG. 19  also illustrates four removable battery packs  26   a ,  26   b ,  26   c ,  26   d . The removable battery packs  26  are designed and configured to mechanically and electrically mate with the battery pack receptacles  24 .  FIG. 19  illustrates a removable battery pack  26  coupled to each battery pack receptacle  24 . In practice, one or more of the battery pack receptacles  24  may be occupied by a removable battery pack  26 . 
     The portable power supply system  100  includes at least one charger  68 . In the exemplary embodiment illustrated in  FIG. 19 , the portable power supply system  100  includes four chargers  68   a ,  68   b ,  68   c ,  68   d , one coupled to each battery pack receptacle  24 . Alternate embodiments may include fewer chargers, either because there are fewer battery pack receptacles or such that a single charger is coupled to more than one battery pack receptacle. For example, a portable power supply system  100  having four battery pack receptacles may include two chargers such that each charger is coupled to two of the battery pack receptacles. In such an embodiment, each charger may provide a charge to its associated battery pack receptacles simultaneously or sequentially. 
     The portable power supply system  100  includes an AC input port (AC in )  46  for receiving an alternating current (AC) power signal from an AC power supply. The mains line of a utility grid is an example of an AC power supply. The AC input port  46  may be a male three pronged plug. The AC input port  46  is electrically coupled to each of the chargers  68  to provide the AC power signal to each of the chargers  68  for charging a removable battery pack  26  coupled to the battery pack receptacle  24 . 
     When a removable battery pack  26  is coupled to the battery pack receptacle  24  and the portable power supply system  100  is coupled to an AC power supply, the charger  68  associated with that battery pack receptacle  24  will provide a charging current to the coupled removable battery pack  26 , assuming conditions are within predefined parameters. Each charger  68  may include a processor for implementing a charging scheme based on the type of battery pack  26  coupled to the associated battery pack receptacle  24  and the conditions of the battery pack  26 , e.g., temperature, voltage level, etc. As illustrated in  FIG. 19 , each charger  68  includes a connection to the associated battery pack  26 . This connection may allow for charging current between the charger  68  and the battery pack  26  and for communications between the charger  68  and the battery pack  26  regarding the status of the battery pack  26 . The status of the battery pack  26  may affect the charging current supplied from the charger  68 . A charger DC-DC converter  158  is coupled to the voltage bus and provides a wake-up voltage signal and power to the charger microcontroller circuit  152   
     Alternatively or additionally, a charger microcontroller circuit  152  may be coupled to each charger  68 . In the illustrated embodiment, a set of charger optocouplers  154  provides information from the chargers  68  to the charger microcontroller circuit  152 . The charger optocouplers  154  may relay the charge status of an associated battery pack  26  to the charger microcontroller circuit  152 . This information may be used to control the individual chargers  150 . This information may also be used to illuminate a set of power supply LEDs  156  to indicate the status of the battery packs  26 . There may be a distinct set of LEDs  156  for each battery pack receptacle  24  or a single set of LEDs  156  for the whole portable power supply system  100 . 
     As noted above, the portable power supply system  100  includes an inverter  44 . The inverter  44  converts the direct current (DC) signal from the removable battery packs  26  into an AC signal for powering electrical devices  160 , such as corded AC power tools. The inverter  44  may be any of a variety of inverters. For example, the inverter  44  may be a pure sine wave inverter. The portable power supply system  100  may also include a booster  134  for increasing the DC signal level from the battery packs  26 . For example, if each of the removable battery packs  26  is a 20 volt battery pack and there are four battery packs  26  coupled to the portable power supply system  100  and the battery packs  26  are coupled to each other in series and then coupled to the booster  134 , then an 80 volt DC signal (V 1 ) is supplied to the booster  134 . The booster  134  may then increase the DC signal to a 120 DC signal or a 170 volt DC signal (V 2 ), as is needed by the particular inverter  44 . The output (V 3 ) of the inverter  44  may be provided directly to an AC output port  38  (AC out ). Alternatively, the output of the inverter  44  may be provided to a filter  138  to clean or otherwise shape the AC signal. The output (V 4 ) of the filter  138  may then be provided to the AC output port  38 . The AC output port  38  may be, for example, a female three prong electrical receptacle. The AC output port  38  may receive a plug from an electrical device  160 , for example, a corded power tool or a corded appliance. The inverter  44  and the booster  132  may be controlled by an inverter microcontroller circuit  64 . 
     In practice, the booster  134  receives the DC signal from the battery packs  26 . The booster  134  generates a boosted DC signal and provides the boosted DC signal to the inverter  44 . The inverter  44  receives the boosted DC signal from the booster  134  and provides an AC signal to the filter  138 . The filter  138  receives the AC signal from the inverter  44  and provides a shaped AC signal to the AC output port  38 . The inverter microcontroller circuit  64  is coupled to the booster  134  and to the inverter  44 . The connection between the inverter microcontroller circuit  64  and the booster  134  and the inverter  44  may be a two way communication connection. This connection allows the inverter microcontroller circuit  64  to receive information from the booster  134  and inverter  44  and to provide control instructions to the booster  134  and the inverter  44 . 
     For the inverter  44  to operate, at least one removable battery pack  26  must be coupled to the portable power supply system  100 . Preferably, more than one removable battery pack  26  is coupled to the portable power supply system  100 . If and how the inverter  44  is able to provide a viable AC signal to the AC output port  38  depends upon the type and number of removable battery packs  26 , the booster  134  and the inverter  44 . For example, a preferred portable power supply system  100  will include a booster  134  and an inverter  44  that will require at least 60 volts DC to provide a 120 volt AC signal to the AC output port  38 . As such, a single 60 volt battery pack  26  could be coupled to the portable power supply system  100  or three 20 volt battery packs  26  could be coupled to the portable power supply system  100 . An alternate, preferred portable power supply system  100  will include a booster  134  and an inverter  44  that will require at least 80 volts DC to provide a 120 volt AC signal to the AC output port  38 . As such, four 20 volt battery packs  26  could be coupled to the portable power supply system  100 . 
     In order to provide the AC signal to the AC output port  38 , a user activates (depresses) the inverter activation switch (IAS)  40 . The IAS  40  is coupled to a first battery pack receptacle  24   a  (BPR 1 ). If a battery pack  26  is coupled to the BPR 1   24   a , an activation signal is coupled to a latch  140 . The latch  140  temporarily closes a converter switch (SW 2 ). When the converter switch SW 2  is closed a power signal from the DC bus is provided to an inverter DC-DC converter  142 . The inverter DC-DC converter  142  provides a DC signal to the inverter microcontroller circuit  64 . This signal “wakes up” the inverter microcontroller circuit  64 . Thereafter, the inverter microcontroller circuit  64  sends a signal to the latch  140  to hold the latch  140  closed, thereby maintaining a DC signal (power) to the inverter DC-DC converter  142 . This allows the inverter microcontroller circuit  64 , the booster  134  and the inverter  44  to continuously operate (assuming there is a sufficient charge on the removable battery packs  26  coupled to the portable power supply system  100 ). 
     As noted above, it is preferred that the charger(s)  68  and the inverter  44  do not operate simultaneously. As such, if the inverter  44  is operating as noted above and a user couples an AC power supply to the AC input port  46 , the system  100  will attempt to either prevent the charger  68  from operating or stop the inverter  44  from operating. 
     In a first embodiment, the portable power supply system  100  will prevent the charger  68  from charging the removable battery packs  26  and continue operating the inverter  44 —providing AC power to the AC output port  38 . 
     In this embodiment, as the charger microcontroller circuit  152  is coupled to the BPR 1   24   a  a signal is presented to the charger microcontroller circuit  152  that AC power has been coupled to the portable power supply system  100 . Since the charger microcontroller circuit  152  is coupled to the inverter microcontroller circuit  64 , the charger microcontroller circuit  152  is aware that the inverter  44  is operating. As such, the charger microcontroller circuit  152  sends a signal to the chargers  68 , for example through the charger optocouplers  154 , to prevent the chargers  68  from charging any battery pack  26  coupled to the portable power supply system  100 . 
     In a second embodiment, the portable power supply system  100  will stop the inverter  44  from operating and allow the chargers  68  to charge any battery packs  26  coupled to the portable power supply system  100 . 
     In this embodiment, the latch  140  is coupled to the AC input port  46 . The signal from the AC input port  46  to the latch  140  directs the latch  140  to override the signal from the inverter microcontroller circuit  64  that keeps the converter switch SW 2  closed and instructs the converter switch SW 2  to open. As a result, the signal from the DC bus to the inverter DC-DC converter  142  is removed thereby turning off the inverter DC-DC converter  142 . This in turn stops sending power to the booster  134 , inverter  44  and the inverter microcontroller circuit  64 . The inverter  44  will then stop operation and power will no longer be provided to the AC output port  38 . This will allow the chargers  68  to charge any battery packs  26  coupled to the portable power supply system  100 . 
     As an alternate or redundant control, the BPR 1   24   a  is coupled to the charger microcontroller circuit  152 . If the BPR 1   24   a  receives an AC voltage signal, the charger microcontroller circuit  152  sends a control signal to the inverter microcontroller circuit  64  indicating this event. The inverter microcontroller circuit  64  then sends a control signal to the latch  140  to open the converter switch SW 2 . This will remove power from the inverter DC-DC converter  142  which in turn removes power from the booster  134 , the inverter  44  and the inverter microcontroller circuit  64 . The inverter  44  will then stop operation and power will no longer be provided to the AC output port  38 . This will allow the chargers  68  to charge any battery packs  26  coupled to the portable power supply system  100 . 
     Alternatively, if the charger  68  is operating as noted above and a user couples an AC corded device  160  to the AC output port  38 , the system  100  will attempt to either prevent the inverter  44  from operating or stop the charger  68  from operating. 
     In a third embodiment, the portable power supply system is coupled to an AC power supply and is charging any removable battery packs  26  coupled to the portable power supply system  100  and a user attempts to operate the inverter  44  to operate a corded device  160  coupled to the portable power supply system  100  by depressing the IAS  40 . In this embodiment, the portable power supply system  100  is configured to prevent the inverter  44  from operating and continue charging any battery packs  26  coupled to the portable power supply system  100 . This is achieved by the latch  140  being coupled to the AC input port  46 . When AC power is present at the AC input port  46 , the signal to the latch  140  prevents the latch  140  from closing even though a battery pack  26  is coupled to the BPR 1   24   a . As the latch  140  does not close, the converter switch SW 2  is not closed. As such, the inverter DC-DC converter  142  is not activated and a wake up voltage is not presented to the inverter microcontroller circuit  64 . 
     In a fourth embodiment, the portable power supply system  100  is coupled to an AC power supply and is charging any removable battery packs  26  coupled to the portable power supply system  100  and a user attempts to operate the inverter  44  to operate a corded device  160  coupled to the portable power supply system  100  by depressing the IAS  40 . In this embodiment, the portable power supply system  100  is configured to stop charging any battery packs  26  coupled to the portable power supply system  100  and activate the inverter  44 . This is achieved by the latch  140  closing the converter switch SW 2  (even though AC power is present at the AC input port  46 ). The inverter DC-DC converter  142  wakes up the inverter microcontroller circuit  64 . Prior to the inverter microcontroller circuit  64  operating the inverter  44 , the inverter microcontroller circuit  64  checks with the charger microcontroller circuit  152  to determine if the charger  68  is operating. If the charger  68  is operating but the inverter microcontroller circuit  64  is awake it indicates that the user desires to operate the inverter  44  and a corded device  160  over charging the battery packs  26 . As such, the inverter microcontroller circuit  64  sends a signal to the charger microcontroller circuit  152  to shut down the chargers  68 . The charger microcontroller circuit  152  then sends a signal to the chargers  68 , for example through the optocouplers  154 , to stop charging. Thereafter, the inverter microcontroller circuit  64  activates the inverter  44  and the booster  134  to provide an AC signal at the AC output port  38 .