Abstract:
Two embodiments for distributing DC power in a building are provided. In the first embodiment, a centralized DC power converter is connected to the building&#39;s standard AC power wiring. The centralized DC power converter generates DC power for at least one DC-powered electronic device. The DC power is routed to DC outlets throughout the building over DC conductor sets. A second embodiment embeds a DC power converter in the outlet, which connects to standard AC power wiring. The embedded DC power converter then generates DC power for at least one DC-powered electronic device. A DC power outlet is also provided which may comprise one or more DC power receptacles or DC power cords and plugs, one or more status indicator LEDs, a retraction mechanism for each of the DC power cords, a cooling fan, and an embedded DC power converter. The DC power converters may be universal DC power converters.

Description:
REFERENCE TO RELATED APPLICATION  
       [0001]     Copending U.S. patent application Ser. No. 11/101,036, entitled “Universal DC Power,” filed on Apr. 6, 2005, is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention relates, generally, to DC power distribution and, more particularly, to distributing and providing connection points for DC power, including universal DC power, in buildings.  
         [0004]     2. Description of the Related Art  
         [0005]     Currently, most digital devices (especially, personal digital appliances) use DC power as their primary power source. These digital devices also tend to require DC power to be supplied at various voltage levels. However, contrary to AC power, DC power is not directly provided by a power distribution network in buildings. Thus, a digital device must be shipped with its own power source. Typically, the power source is in the form of a “brick” or “wall wart” style supply that converts standard AC power already distributed in a building (120VAC or 220VAC) to the specific DC power required by the particular digital device.  
         [0006]     Providing a power supply with each digital device has many disadvantages. (1) Including a DC power supply with each device increases manufacturing costs and, thus, increases the cost to end-users. (2) Extra solid waste is created when a digital device is discarded. Although it may still be functional, the power supply cannot be used with other digital devices since it is specific to the device. (3) Consumers must keep track of which power supply goes with each digital device they own. (4) Dangerous situations may arise when a confused consumer attempts to use the incorrect power supply with the digital device.  
         [0007]     Universal DC power solves these problems by providing a way for the digital device to communicate its power requirements to a universal DC power converter. The universal DC power converter then supplies the requested power. However, the universal converter still exists in a separate external “brick” or “wall wart” style supply.  
         [0008]     Thus, there is a need for a DC power distribution network in a building and for standard outlets to connect DC-powered devices into this distribution network.  
       SUMMARY OF THE INVENTION  
       [0009]     In one embodiment of the invention, a power converter capable of providing DC power to one or more DC-powered devices is located in a centralized location in the building. The power converter receives standard AC power (120V or 220V) wired directly from the AC breaker box on its own breaker. The centralized power converter has one or more DC power output terminals. Each one of the terminals is capable of supplying a single DC-powered electronic device. Conductors are connected to the output terminals of the centralized power converter, and the conductors are then routed throughout the building to power outlets located at various convenient points in the building. Upon reaching the power outlets, the conductor is connected to a DC receptacle or DC plug and cord accessible from the face of the power outlet. DC-powered devices are then connected into these outlets.  
         [0010]     In another embodiment of the invention, a DC power converter capable of providing DC power to one or more DC-powered electronic devices is embedded in a power outlet. The power converter receives standard AC power (120VAC or 220VAC) directly from the AC conductors normally routed throughout a building to standard AC outlets. The power converter has at least one output receptacle or plug and cord to enable DC-powered devices to connect directly into the power converter through the face of the outlet.  
         [0011]     In either embodiment, the power converters may be universal power converters that have the ability to communicate with DC-powered electronic devices and receive power requirements from those devices. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The above and other features and advantages of embodiments of the invention will become readily apparent by reference to the following detailed description when considered in conjunction with the accompanying drawings.  
         [0013]      FIG. 1  is a diagram showing a distribution of DC power in a building using a centralized power converter.  
         [0014]      FIG. 2  is a block diagram of a central power converter.  
         [0015]      FIG. 3  is a drawing of a faceplate for an outlet containing one standard AC receptacle and a DC receptacle.  
         [0016]      FIGS. 4A and 4B  are diagrams illustrating front and side views, respectively, of an outlet containing one standard AC receptacle and one retractable DC power plug and cord.  
         [0017]      FIGS. 5A and 5B  are diagrams illustrating front and side views, respectively, of a retraction mechanism.  
         [0018]      FIG. 6  shows a distribution of DC power in a building using one or more power converters embedded in the power outlet.  
         [0019]      FIG. 7  is a drawing of a faceplate for an outlet containing one standard AC receptacle, one DC receptacle, and ventilation grating.  
         [0020]      FIGS. 8A and 8B  are drawings illustrating front and side views, respectively, of an outlet containing one standard AC receptacle, a DC power converter and one DC receptacle.  
         [0021]      FIG. 9  is a schematic diagram of an AC-DC converter used in the DC power converter of  FIG. 8 .  
         [0022]      FIGS. 10A, 10B , and  10 C illustrate the circuit boards used in the DC power converter of  FIG. 8 . 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0023]     The invention will be described below with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.  
         [0024]      FIG. 1  is a diagram of one embodiment of the invention  100 , which comprises a DC power converter  200  that receives standard AC power (e.g., single-phase 120VAC or two-phase 220VAC)  103  directly from a breaker box  102  in a building. The breaker box  102  receives power  101 , two-phase 220VAC in this embodiment, from the utility company. The DC power converter  200 , which may be a universal DC power converter, converts the AC power  103  into DC power for the one or more DC-powered electronic devices  108 . U.S. patent application Ser. No. 11/101,036 describes a universal DC power converter. If the DC power converter  200  is a universal DC power converter, power is supplied according to the parameters communicated by the DC-powered electronic devices  108 . One or more conductor sets  105  connect the DC power converter  200  to the outlets  106 ,  107 , and  400 . Each conductor set  105  contains a first conductor for conveying positive DC voltage; a second conductor for conveying a common voltage reference; if the DC power converter  200  is a universal DC power converter, a third conductor for communicating DC power parameters from the devices  108  to the DC power converter  200 ; and a fourth conductor to power a status indicator LED. The DC-powered electronic devices  108  are then plugged into the outlets  106 ,  107 , and  400  to receive DC-power. Faceplate  300  covers the outlet  400 .  
         [0025]      FIG. 2  is a block diagram of an embodiment of the centralized DC power converter  200  in  FIG. 1 , using universal DC power converters. First, an AC-DC power converter  201  generates a DC input voltage  202  from standard AC power  203 . The DC input voltage  202  powers one or more universal power converters  204  that each generates output power  205  for use by a single DC-powered electronic device. These universal power converters  204  are capable of supplying a range of DC voltages and power levels as requested by the device  108 . Universal controller  206  controls communication with the DC-powered electronic devices  108  and controls the output power of the universal power converters  204  with signals  207 .  
         [0026]      FIG. 3  is a drawing of the faceplate  300  for use with an outlet with one standard AC receptacle and a DC receptacle or power cord. The faceplate comprises a cutout  301  for a standard AC receptacle, a cutout  303  for a DC receptacle or power cord, a cutout  304  for an optional status indicator LED, and a cutout  302  to mount the faceplate to the outlet with a screw.  
         [0027]      FIGS. 4A and 4B  are diagrams showing the front and right sides, respectively, of an outlet  400  with one AC receptacle  401  and one DC receptacle  403 . The outlet  400  contains a standard AC receptacle  401 . Standard AC power, single phase 120VAC in this embodiment, is connected to the outlet  400  to power the AC receptacle  401 : the hot line is connected to lug screws  408 ; the neutral line is connected to lug screws  410 ; and the earth ground is connected to lug screw  411 . A conductive plate  409  allows AC current to flow between lug screws  408  and  410 , respectively, so that outlets  400  can be daisy-chained.  
         [0028]     The DC receptacle  403  of outlet  400  comprises a DC power cord  407  attached to a DC power plug  406 . A universal DC power conductor set  105  ( FIG. 1 ) is connected to the outlet  400  to power the DC power cord  407  and DC power plug  406 : the first positive conductor is connected to lug screw  412 ; the common conductor is connected to lug screw  413 ; an optional third conductor for communications is connected to lug screw  414 ; and the fourth conductor is connected to lug screw  415  to power a status indicator LED  404 . The outlet  400  may also comprise a bulk capacitor (not shown) with its positive terminal electrically connected to the lug screw  412  for the first conductor and its negative terminal electrically connected to the lug screw  413  for the common conductor. The bulk capacitor, which may be situated between the lug screws  412  and  413  and the DC power cord  407 , mitigates the effects of inductance in the conductor set  105  connecting the outlet  400  to the centralized DC power converter  200  when the loading of the DC-powered electronic device changes quickly. Mounting brackets  416  allow the outlet  400  to be mounted in a standard mounting box, and screw hole  402  allows a faceplate  300  to be mounted to the outlet  400 .  
         [0029]     A retraction mechanism can be employed to retract and coil the DC power cord  407  into the outlet  400  for storage. A user can pull the DC power cord  407  out of the outlet  400  for connection to a DC powered electronic device. When the connection is no longer need, the user can push a retraction button  405 , which causes the DC power cord  407  to be pulled back into the outlet  400 .  
         [0030]      FIGS. 5A and 5B  show front and side views, respectively, of the retraction mechanism  500  used to retract a power plug  506  and cord  507  into the outlet  400  ( FIG. 4 ).  
         [0031]     The DC power cord  507  (40″ long in one embodiment) is coiled around a spool consisting of an axle  503  and side plates  501  (1″ in diameter in one embodiment). In one embodiment, the axle  503  and side plates  501  are mechanically connected in a rigid manner to form a solid piece. As shown in  FIG. 5B , the side plates  501  contain triangular ratchet grooves  502  along the outside edge in a regular pattern, and conductive strips  504  to convey the electrical power from the stationary conductors  512 ,  513 , and  514  to the rotating DC power cord  507 . The stationary conductor  512  is the positive DC voltage; the stationary conductor  513  is the common DC voltage; and the stationary conductor  514  is an optional third conductor for communicating with the DC device.  
         [0032]     One end of each of the stationary conductors  512 ,  513 , and  514  is connected to a small pass-through board  515  to which stationary fingers  516  are mounted. The stationary fingers  516 , in turn, make mechanical contact with the conductive strips  504  providing an electrical connection from stationary conductors  512 ,  513 , and  514  to the power cord  507 . The other end of the stationary conductors  512 ,  513 , and  514  is electrically connected to a threaded base into which the lugs  412 ,  413  and  414  are screwed into, respectively.  
         [0033]     The pass-through board  515  is mounted to the body of the outlet  400 , and the axle  503  mounts into concave indentions in the body of the outlet  400 .  
         [0034]     As shown in  FIG. 5A , axle  503  contains a wider (0.25″ in this embodiment) diameter output drum  510 . The loose end of an extension spring  508  is attached to the output drum  510  with a small screw  511 . As the power cord  507  is pulled from the outlet  400 , the extension spring  508  is wound around the output drum  510 , storing energy for retraction. Referring back to  FIG. 5B , ratchet arm  517  is held in place by a small rod placed through pivot hole  519  and mounted to the body of the outlet  400  and is pushed into ratchet grooves  502  by coil spring  518 . When the user has pulled the desired length of power cord  507  from outlet  400 , the cord is held at that length when the ratchet arm  517  catches a ratchet groove  502  and prevents the axle  503  and side plates  501  from turning. When the user pushes retraction button  505 , the ratchet arm  517  pivots away from the side plate  501  and disengages from ratchet groove  502 . The cord is now free to retract powered by the energy stored in the extension spring  508 . The extension spring  508  is mounted to the body of the outlet  400  by an axle  520  running through mount  509  and extension spring  508 , upon which extension spring  508  can rotate.  FIG. 6  is a diagram of another embodiment of the invention  600 . In this embodiment, standard AC power is received from the utility company (two-phase 220VAC) via conductor  601  into a breaker box  602 . From the breaker box  602 , AC power is routed to outlets  606  and  700  via conductors  603  (single-phase 110VAC in one embodiment or two-phase 220VAC in another embodiment). The outlets  606  and  700  comprise DC power converters to convert the AC power received from conductor  603  into the DC power requested by the DC-powered electronic devices  608 . The DC power converters embedded in the outlets  606  and  700  may be standard DC power converters or universal DC power converters. Where a DC-powered electronic device is not compatible with universal DC power standards, the user may select the appropriate voltage level from a slide switch accessible from the faceplate  800 . The faceplate  800  covers the outlet  700 .  
         [0035]      FIG. 7  is a drawing of faceplate  700  for use with an outlet with one standard AC receptacle and a DC receptacle or power cord. Cutout  701  is for a standard AC receptacle; cutout  703  is for a DC receptacle or power cord; cutout  704  is for an optional status indicator LED; and cutout  702  is to mount the faceplate  700  to the outlet with a screw. The faceplate  700  also comprises ventilation gratings  706  and  707  to allow airflow through the faceplate  700  and outlet  800 . Cutout  708  is for a voltage selector switch and embossing  709  indicates the voltage levels of various switch settings.  
         [0036]      FIGS. 8A and 8B  are drawings illustrating front and side views, respectively, of outlet  800  comprising one AC receptacle, one DC receptacle, and a DC power converter. The outlet  800  comprises a standard AC receptacle  801 . Standard AC power, single phase 120VAC in this embodiment, is connected to the outlet  800  to power the AC receptacle  801  and a DC power converter  1000 : the hot line is connected to lug screws  808 ; the neutral line is connected to lug screws  810 ; and the earth ground is connected to lug screw  811 . A conductive plate  809  allows AC current to flow between lug screws  808  and  810 , respectively, so that outlets can be daisy-chained.  
         [0037]     The outlet  800  comprises a DC power converter (universal or otherwise)  1000  ( FIG. 10 ) and a DC receptacle  1022 . DC power is connected from the DC power converter  1000  to the DC receptacle  1022 : the conductors comprise a first positive conductor, a second common conductor, and an optional third conductor for communication with the DC-powered electronic device. The DC power converter  1000  also connects to a status indicator LED  1023 . Mounting brackets  816  allow the outlet  800  to be mounted in a standard mounting box, and screw hole  802  allows a faceplate  700  to be mounted to the outlet  800 . Exhaust fan  1024  is controlled by the DC power converter  1000  to provide airflow in outlet  800 . Fresh ambient air is pulled into the outlet  800  through air intake  806 . Slide switch  1025  selects a voltage level for the DC power converter to supply in case the DC-powered electronic device is not universal DC compatible.  
         [0038]      FIG. 9  is a schematic diagram of the AC-DC converter portion of the DC power converter  1000  embedded in outlet  800 . Because of the space limitations of outlet  800 , the implementation of the AC-DC converter cannot use a standard 60 Hz AC transformer. A 60 Hz transformer providing reasonable power would be too large or a smaller one would not provide sufficient power to be useful. Therefore, the standard 60 Hz AC power must be rectified into a primary DC voltage, modulated at a higher frequency (approximately 100 KHz in this embodiment), stepped-down and isolated through a smaller transformer made for higher frequency operation, and then rectified and filtered for use by the DC power converter.  
         [0039]     The AC-DC converter  900  receives AC power (120VAC in one embodiment) from a hot conductor  901  and a neutral conductor  902 . The AC power is rectified by bridge rectifier  903  and filtered by capacitor  904  to form a primary DC voltage (160 volts nominal in one embodiment). This primary DC voltage is fed into the center tap of the primary winding of a high frequency power transformer  905 . Transformer  905 , NMOS transistors  906  and  907 , and capacitors  908  and  909  form a tuned, high efficiency class-C push-pull power converter. Transistors  906  and  907  conduct when their gates are driven high (+5V in one embodiment) through conductors  910  and  911 , respectively, by a class-C power converter controller (integrated into a universal DC power converter in one embodiment). The secondary winding of transformer  905  induces an AC voltage across bridge rectifier  912  whose output is filtered by capacitor  913  to product the DC input voltage  914 . Dampening diodes  915  and  916  protect the transistors  906  and  907 , respectively, from negative voltage spikes that would otherwise damage the transistors&#39;  906  and  907  gate oxide.  
         [0040]     In one embodiment, each half of the primary winding of transformer  905  has a 1 mH inductance and capacitors  908  and  909  have a 0.01 μF capacitance. The gate conductors  910  and  911  are pulsed with 1 μs wide pulse at a varying frequency. The phase of the pulses on  910  and  911  are 180 degrees out of phase. As the load seen by the DC input voltage  914  increases, the period of the pulses on gate conductors  910  and  911  is decreased until it is at 6 μs. If the period of gate conductors  910  and  911  is reduced below 6 μs, the efficiency of circuit  900  is reduced. If the load seen by the DC input voltage  914  is reduced, the period of the pulses on gate conductors  910  and  911  is increased in increments of 2 μs to maintain class-C efficiency. If a load is such that it falls between two 2 μs increments, the controller that drives gate conductors  910  and  911  may switch between the two increments in such a way that the average of all the pulse periods matches the load.  
         [0041]      FIGS. 10A, 10B , and  10 C are drawings of the two circuit boards  1001  and  1002  comprising a universal DC power converter embedded in the outlet  800  including major components. A top view of  1001  and  1002  is shown in  FIGS. 10A and 10B , respectively, and a side view of the circuit boards as they are connected together  1000  is shown in  FIG. 10C . Circuit board  1001  implements most of the AC-DC converter  900 . A first bridge rectifier  1003  and filter capacitor  1004  create a primary DC voltage from standard AC power (single-phase 120VAC in one embodiment). This voltage is used to create a modulated current through transformer  1005 , which is gated by NMOS transistors  1006  and  1007 . The two terminals of the secondary windings are connected to a second circuit board  1002 , along with the control signals for the gates of transistors  1006  and  1007  and a ground conductor, through connector  1015  and terminals  1016 .  
         [0042]     Circuit board  1002  converts the power provided from the secondary winding of transformer  1005  into the DC input voltage of the power converter. Circuit board  1002  also converts the DC input voltage to a voltage level usable by an attached DC-powered electronic device. A second rectifier  1012  and filter capacitor  1013  rectify the current and voltage from the secondary of transformer  1005  into the DC input voltage for the universal DC power controller chip  1017 . A universal DC power controller chip  1017  comprises: a controller for the gates of transistors  1006  and  1007  to maintain the DC input voltage at a constant level (32V in one embodiment) under varying loads; a universal DC controller for communicating with an external DC-powered electronic device; a DC-DC buck converter for converting the DC input voltage to the voltage requested by the DC-powered electronic device using transistors  1018  and  1019 , inductor  1020 , and capacitor  1021 ; a current monitor that uses current sense resistors  1014  to measure the amount of current delivered to the DC-powered electronic device; an LED driver circuit to control a status LED  1023 ; a temperature monitor to measure the temperature of the board; and a fan controller to regulate the speed of a DC fan  1024  based on the board temperature. DC fan  1024  expels heated air from the outlet  800  while cooler air is drawn into the outlet  800  through air intake  806 . In one embodiment, the DC fan  1024  is not mounted directly to the circuit board  1002 ; rather, the DC fan  1024  mounts to the body of the outlet  800 . The two wires from DC fan  1024  connect to the circuit board  1002 . The external DC-powered electronic device connects to the outlet  800  through the DC receptacle  1022 . An indicator LED  1023  indicates status to the user. In the case that the connected DC-powered electronic device is not compatible with universal DC standards, the user may select an appropriate voltage level using slide switch  1025 .  
         [0043]     All components comprising the circuit boards of the universal power converter  1000  are currently available from common electronics vendors, except for the universal DC power controller chip  1017 .  
         [0044]     Referring to  FIGS. 1, 4A ,  4 B,  5 A,  5 B,  8 A, and  8 B, if the universal DC power algorithm does not need the third conductor for communication between the converter  200  or  1000  and the device  108  or  608 , the DC receptacle  1023  and DC power jack/cord  406 / 407  and  506 / 507  can be a commonly available DC power jack, cord or plug, or another two conductor DC power jack, cord or plug designed specifically for that universal DC standard. If the universal DC power algorithm does require the third conductor for communication between the converter  200  or  1000  and the device  108  or  608 , the DC receptacle  1023  and DC plug/cord  406 / 407   506 / 507  will require a third contact to connect the communication conductor from the device  108  or  608  to the converter  200  or  1000 .  
         [0045]     Having described exemplary embodiments of the invention, it is noted that modifications and variations can be made by persons skilled in the art in light of the above teachings. Therefore, it is to be understood that changes may be made to embodiments of the invention disclosed that are nevertheless still within the scope and the spirit of the invention as defined by the appended claims.