Patent Publication Number: US-2003222503-A1

Title: Automatic voltage selection in a DC power distribution apparatus

Description:
CROSS-RELATED APPLICATIONS  
     [0001] This application is a continuation-in-part of application Ser. No. 09/891,926 filed Jun. 26, 2001. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] 1. Field of the Invention  
       [0003] This invention relates to DC power distribution from a source to a peripheral device wherein the appropriate voltage level is selected automatically.  
       [0004] 2. Prior Art  
       [0005] The market is replete with electronic equipment to which peripheral equipment is connected for cooperative action. The personal computer is one example of equipment to which peripheral equipment such as a FAX/modem and a LABEL scanner are connected for communication purposes. Another example is the television set to which a video cassette recorder (VCR) is connected; another, a stereo system. A tape drive, which might be connected to any of the above hosts, is a particularly familiar peripheral. Each piece of peripheral equipment is connected separately to an in-the-wall socket for power, as well as to the host, leading to a tangle of cords characteristic of any PC installation, stereo system or video system.  
       [0006] The peripherals often require different voltage levels for operation. Thus, five volt, nine volt, and 12 volt requirements are not uncommon. Consequently, not only are the power cords common, but they typically also require transformers. The transformers, in turn, not only further complicate the tangle of cords, but they also are expensive and not entirely reliable. Most individuals with systems of this type often find themselves complaining about the plethora of wires providing further impetus for the significant effort now being expended to develop wireless communication links between components. Still the tangle of power cords and transformers remains.  
       [0007] The most significant prior art known to the inventor hereof, consists of related disclosures of this inventor, namely, U.S. Pat. Nos. 5,838,554; 6,091,611; and 6,172,884. However, each of these patents requires installation of a resistor in a connector which significantly increases the cost of the connector. On the other hand, the present invention employs a simple connector configuration without any resistors.  
       SUMMARY OF THE INVENTION  
       [0008] The invention is based on the recognition that host equipment such as a personal computer, a television set or a stereo tuner has an internal power supply and a voltage regulator which already provides low voltage requirements for internal components and can be adapted to permit the requisite low voltage power to be supplied to the peripheral equipment directly from the host equipment rather than separately through transformers to an in-the-wall supply. In this manner, the tangle of cords, characteristic of such systems, is considerably simplified. To this end, provision is made in the housing of a host to provide a socket, or sockets, to which a peripheral piece of equipment can be connected for receiving directly from the host the low voltage DC power it requires. The socket(s) are connected electrically to the outputs of the internal power supply (or regulator) of the host for providing the low voltage needed to power the peripheral. The power supply may be mounted on the rear face of the computer. The power supply may alternatively be internal with a DC power cable connected to a slot at the rear face of the computer providing for at least one DC socket there. In each such configuration, the principal feature of the invention resides in the use of a connector for connecting the host DC power to the peripheral DC power usage device. The connector comprises a selected resistor installed therein. The resistor value (i.e., resistance) is selected to produce a pre-determined control voltage which is fed back to a DC to DC converter in the host&#39;s internal power supply. The converter comprises a pulse width modulation control device. The control voltage determines the duty cycle (i.e., pulse width) of the modulation to reduce the output from a maximum voltage to an appropriate voltage suitable for the particular peripheral power usage device. Thus, by simply selecting the appropriate connector having a correlated resistor previously installed in the connector to the host rear panel, the voltage level for the corresponding peripheral device is automatically selected. Thus, the present invention obviates the prior art requirement for using separate power supplies for each peripheral. Moreover, the invention obviates the prior art requirement for fixed DC output voltage levels and for alterable levels which require manual selection such as by switch or jumper.  
       [0009] In one alternative embodiment, the DC power distribution apparatus of the present invention comprises a stand-alone unit having one or more universal ports for receiving a cable connector containing the appropriate pins for a selected DC power usage device. In another alternative embodiment, the cable is universal, but a unique connector attached to the cable, employs only the appropriate pins for a selected voltage. Each distinct voltage utilizes a unique connector.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0010] The aforementioned objects and advantages of the present invention, as well as additional objects and advantages thereof, will be more fully understood hereinafter as a result of a detailed description of a preferred embodiment when taken in conjunction with the following drawings in which:  
     [0011]FIG. 1 is a block diagram illustrating the principals of the series of inventions which includes the present invention;  
     [0012]FIG. 2 is a rear panel drawing of a prior art apparatus;  
     [0013]FIG. 3 is a rear panel drawing of another prior art apparatus;  
     [0014]FIG. 4 is a schematic illustration of an internal power supply providing a DC power to an external cable having a resistor which determines the DC voltage at a rear panel in accordance with the invention;  
     [0015]FIG. 5, comprising FIGS. 5 a  and  5   b , is a block diagram illustrating a preferred embodiment of the invention;  
     [0016]FIG. 6 is a simplified schematic illustration of the resistor selection feature of the invention;  
     [0017]FIG. 7 is a rear panel drawing of a preferred embodiment of the invention;  
     [0018]FIG. 8 is a drawing of an alternative embodiment comprising a stand-alone unit;  
     [0019]FIG. 9, comprising FIGS. 9 a  and  9   b , is a detailed schematic drawing of a preferred embodiment;  
     [0020]FIG. 10 illustrates another alternative embodiment in which a cable having only selected pin connections determines the voltage at the power usage device;  
     [0021]FIG. 11 depicts the pin selections of FIG. 10 for various voltage selections; and  
     [0022]FIGS. 12 and 13 illustrate still another embodiment wherein the cable between the power supply and power usage device is universal, but a connector at the power usage device has selected pin connections to select a particular voltage.  
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS OF THE INVENTION  
     [0023] Reference will be made first to prior art FIGS.  1 - 3  to provide a basis for understanding the unique improvement of the invention.  
     [0024]FIG. 1 shows a personal computer  10  having a housing  11 . A power supply  13  (with a voltage regulator (not shown)) is located within the housing. The power supply is connected to an in-the-wall socket (or equivalent) as indicated by cord  19  and plug  20 . Power supply  13  is connected electrically to components (not shown) within the housing which constitute typical components for a computer for supplying power to those components as shown by wires  21 . Typical peripherals for a computer are, for example, a LABEL scanner  22 , a FAX/MODEM  23 , and a tape drive (or CD ROM)  25  shown also connected to internal power supply  13 .  
     [0025]FIG. 2 shows a face of a typical power supply for a personal computer. The power supply typically is secured within housing  11  with face  30  visible at an aperture in the computer housing.  
     [0026] The power supply includes a fan which is secured behind the pattern of curved openings  32 . Also, plugs  34  and  35  are available for connection to the computer monitor and to wall power, respectively.  
     [0027] Additional sockets  40  are provided in the computer housing, or in the face of the internal power supply if exposed at the computer housing, for direct connection of wires  41 ,  42  and  43  connecting the LABEL scanner, FAX/MODEM and tape drive respectively of FIG. 1 for supplying the low voltage requirements for those peripherals in the absence of connection to in-the-wall sockets and in the absence of associated power supplies.  
     [0028] Each of sockets  40 , illustratively, is shown as circular with a central pin for conforming to popular connector shapes for the illustrative peripherals. Of course, other connector shapes could be provided for connection to cables of alternative configurations. What is necessary, is that low voltage outputs from a host&#39;s internal power supply are connected to newly provided sockets at the housing face of the host.  
     [0029]FIG. 3 illustrates an example of the prior art wherein a power supply configuration is of the type shown in FIG. 2 except that the voltage at each socket is variable. Specifically, the power supply includes a fan which occupies a position behind the pattern of curved openings  82 . Also, plugs or sockets  84  and  85  are available for connection for the computer monitor and to wall power respectively.  
     [0030] In the configuration of FIG. 3, each of the sockets  87 ,  88  and  89 , for the external connection of peripheral equipment, is associated with a variable voltage control  90 ,  91  and  92 , respectively, for selecting an appropriate voltage at the associated socket.  
     [0031] Although the aforementioned prior art is described in connection with a personal computer, FIG. 1 could also represent a stereo system with associated peripherals or a television system with a video cassette and the like. In each instance, additional sockets, or connectors, are provided at the housing face for external connection of peripherals for supplying power thereto.  
     [0032] Referring to FIGS.  4 - 7 , it will be seen that unlike the aforementioned prior art, the present invention provides for automatic selection of the appropriate DC voltage by employing a selected resistor in the connector of the cable which mates with the host&#39;s power supply. The value of the resistor determines the voltage by applying a proportional control voltage V control  to an input of a pulse width modulator (PWM) which may for example, be a Texas Instruments TL 494 Pulse-Width-Modulation Control Circuits integrated circuit chip. The PWM controls the pulse width and thus the duty cycle of a switching signal in a DC to DC converter, the input to which is a regulated maximum DC voltage (i.e., 23 Volts). The higher the pulse duty cycle, the closer the output voltage to the maximum available and the lower the duty cycle, the closer the output voltage to the minimum. In the illustrated embodiments, the available output DC power is provided at two distinct ports or connectors, one for a higher range of voltage (i.e., 9 Volts to 19 Volts) and another for a lower range (i.e., 3 Volts to 9 Volts). Thus, the illustrated embodiments have two separate pulse-width modulation control circuit chips connected into two distance circuits, one for each range of output voltage.  
     [0033]FIG. 4 illustrates a version of the preferred embodiment wherein a host system such as a desk-top computer  100  having a chassis  101 , provides a DC power source  102 , the output of which is connected by an internal cable  104  to a panel connector  106 . A cable  108  has a mating connector  110  in which there is a selected value resistor  112  installed. Cable  108  transfers the DC power to a peripheral apparatus (not shown) where the cable may have a second connector or may be hard wired into the peripheral apparatus.  
     [0034] In FIGS. 5 a  and  5   b , the aforementioned dual range DC output configuration is illustrate in block diagram form. Each of the two available DC outputs  115  and  117  derives power from a corresponding DC to DC converter  120  and  122 . The input to each DC to DC converter is derived from a standard AC to DC converter (not shown) which, in the illustrated embodiment, provides a regulated 23V DC at V IN . Each DC to DC converter  120  and  122  provides three lines, namely V A  (V B ), V OUT  and GND (ground). These three lines are connected to corresponding connectors  124  and  126  at inputs V SA  (V SB ), V OUT  and GND. A resistor RES is connected across V SA  (V SB ) and GND while V OUT  and GND provide the output of each connector  115  and  117 , respectively. The resistor RES has a selected value of resistance which provides a feedback signal from V SA  of the connectors  124  and  126  to the V A  line of the converters  120  and  122 . This feedback signal is the control voltage (V CONTROL ) which determines the voltage level of V OUT .  
     [0035] As shown in FIG. 6, the control voltage is applied to a pulse width modulation circuit and controls the duty cycle of the modulator by altering the pulse width in accordance with the selected value of RES.  
     [0036] The invention herein may be implemented in a variety of different configurations. The embodiment of FIG. 7 illustrates an implementation in the chassis of a computer wherein the DC voltage outputs are available at a rear panel for use by computer peripherals. The embodiment of FIG. 8 illustrates an implementation as a stand-alone; “Universal” DC power source  114  having a plurality of connectors  126 , each having its own selected resistor RES for use with a particular DC power usage device by connection at output  117 .  
     [0037] In order to provide ample details of the disclosed embodiment, a schematic of an actual operational configuration of the invention is shown in FIGS. 9A and 9B and the significant components thereof are listed in Table 1 below.  
                                   TABLE I                       NUM-                           BER   PART   VALUE   SIZE   LOCATION   USE                                                        34   MOSFET   IRFZ24N                   35   transistor   2N7000   SOT-220   Q6, 12   2       36   DIODE   3 A/50 V   TO-252   Q11, 16   2       37   RES.   1.2K   0603   R3   1       38   RES   22K   0603   R4   1       39   RES   2.2K   0603   R5   1       40   RES   ?   0603   R6   1       41   RES   330 OHM   0603   R7   1       42   RES   10K   0603   R2, 8.9.30,   8                       32, 35, 55, 67       43   RES   330K   0603   R11A, B, C   3       44   RES   10 OHM   0603   R1, 33   2       45   RES   470 OHM   0603   R10   1       46   RES   47K/3 W   DIP   R12   1       47   RES   20K   0603   R14   1       48   RES   10/.25 W   DIP   R15   1       49   RES   120K/13 W   DIP   R65   1       50   RES   0.02/3 W   DIP   R41   1       51   RES   100K   0603   R19, 44   2       52   RES   33K   0603   R20   1       53   RES   150 OHM   0603   R22, 24, 29,   6                       47, 49, 54       54   RES   47 OHM   0603   R23, 48   2       55   RES   620 OHM   0603   R18   1       56   RES   15K   0603   R21, 46   2       57   RES   1.5K   0603   R25, 50   2       58   RES   4.7K   0603   RR26, 27,   11                       28, 37, 39,                       51, 52, 53,                       57, 59, 63       59   RES   0.12   DIP   R31   1               OHM/2 W       60   RES   680 OHM   0603   R34   1       61   RES   250K   0603   R37   1       62   RES   39K   0603   R40, 60   2       63   RES   1K/2 W   0805   R41A, B, C,   6                       R61A, B, C       64   RES   0.22/2 W   DIP   R61   1       65   RES   1K   0603   R43, 62, 64   3       66   RES   12K   0603   R45   1       67   RES   1M   0603   R58   1       68   RES   6.8K   0603   R66   1       69   transformer   ERL28       T1   1       70   TR1   LMO3       TR1   1       71   IC   UC3842       U1   1       72   IC   TL494       U2, U3   2       73   ZENER   25 V   SMD   ZD1   1       74   ZENER   22 V   SMD   ZD2   1       75   AC   0712-2-PP       CN2   1           SOCKET       76   PCB               1                  
 
     [0038]FIG. 9 shows a block  200  which comprises a standard AC/DC converter. FIG. 9 also shows a block  201  representing a control chip which is commercially available from Texas Instruments as Part Number TL 494 CNS the organization and operation of which is represented in the functional block diagram of FIG. 5 available from the manufacture.  
     [0039] Block  203  in FIG. 9 represents the resistor network segment or incomplete resistor network in accordance with the principles of this invention.  
     [0040] The converter  200  of FIG. 9 is essentially a standard AC/DC converter comprising an AC side  210  and a DC side  211 . Any standard AC/DC converter could be used herein. The converter shown has an input control arrangement  212  for providing a shaped response to the AC input signal on line  213 . Input control arrangement  212  includes a transistor  214  with the emitters connected between a capacitor  215  and a resistor  216 . The collector of transistor  214  is connected via resistor  218  and capacitor  219  to the output  220  of an AC/DC connector chip  221 . Chip  221  is commercially available from UNITRON Corporation as Part Number U2UC3842 AN. The input control arrangement also includes a diode  223  and a ZENER diode  224  connected in series between resistor  216  and an input to (reverse) diode  226  and to transformer  230 . The input control arrangement  212  is operative to protect against start up overvoltages. The remainder of the AC/DC circuit is entirely standard.  
     [0041] Network  203  (along with chip  201 ) occurs in each of two essentially identical arrangements, one for a relatively high voltage output (for example 19 Volts) and one for a relatively low voltage output (for example 9 Volts) illustratively useful for different classes of portable electronic equipment such as cell phones, pagers, portable game devices and laptops, PDA&#39;s, portable DVD/CD players for high &amp; relatively low voltage requirement respectively. Only one of these arrangements is described below.  
     [0042] Resistor network segment  203  of FIG. 9 comprises a parallel arrangement of resistors  300 ,  301 ,  302  and  303  connected via a capacitor  304  and a resistor  305  to the V2+ input of control chip  201 . Resistor  303  also is connected to inputs V REF  and OC of chip  201 ; resistor  302  is connected to input VI− and resistor  301  is connected via a capacitor  310  also to input VI−. Resistor  300  is connected between-input DTC of chip  201  and ground  313 . Resistor  303  also is connected to ground  313  via resistor  320  and resistor  301  is connected via capacitor  310 , resistor  302 , capacitor  304  and resistor  305  to the V2+ port of chip  201  and V OUT    220 .  
     [0043] A voltage selector module in the form of a connector, connects to the control chip at C1-E1 (or C2-E2) depending on whether a high or relatively low voltage is required. The voltage selector module includes a resistor which determines the voltage for a connected piece of equipment corresponding to the resistor in the module.  
     [0044] When the selector module is connected, it signals the control chip to provide the specified voltage. That voltage is supplied at the V OUT  port  322 .  
     [0045] The diode and circuit arrangement to the right of chip  201  in FIG. 9B is standard configuration for controlling heat loss with components selected for that purpose.  
     [0046] Reference will now be made to FIGS.  10  to  13  which depict two alternative embodiments wherein the voltage selection resistors are retained in the power supply while pins in the cable or in the connector to the power usage device, determine the voltage. By way of illustration in FIGS. 10 and 11, a power supply connector  510  provides seven distinct DC voltages and a ground. The voltages are determined by a network  512  of differently valued resistors in the power supply. The voltage at the power usage device  522  is determined by which of the pins in connector  510  is connected to a usage device connector  520 . This, in turn, is determined by cable  516  by means of connector  515 . Depending on which configuration of pins is employed, i.e.,  515   a ,  515   b  . . .  515   g , one of the resistors  512 , and only one, is selected to set the voltage. In FIG. 11, the  515   a  cable connector selects 5.0 volts; the  515   b  cable connector selects 6.5 volts; and the  515   g  cable connector selects 15 volts. A key  517  in the cable connector  515  and  519  in the power supply connector  510 , prevents erroneous voltage selection. Similar keys  521  and  523  are in the connectors  518  and  520 .  
     [0047] Another version of this automatic voltage selection technique is shown in FIGS. 12 and 13. In this version a universal cable  532  has all pins in respective connectors  530  and  534 . A conversion device  536  has a mating connector  538  and a two-pin voltage selection connector  540 , the latter being comparable to connector  515  of FIGS. 10 and 11.  
     [0048] Having thus disclosed preferred illustrative embodiments of the invention, it being understood that various modifications, additions and alternative applications are contemplated and that the scope of protection hereof is limited only by the appended claims and their equivalents, what is claimed is: