Abstract:
A switching mode power supply uses two power source inputs, an alternating current input and a direct current input. A pulse width modulation controller is used to control current from two primary windings of a transformer. The secondary of the transformer has a rectified direct current output. From the direct current output a current/voltage comparator receives a signal across a sensing resistor and through an inverter and in parallel with respect to the direct current output. The current/voltage comparator may communicate through an opto coupler/isolator and then to a pulse width modulation controller. Instructions are received about the voltage and current necessary to be supplied by the direct current output of the power supply from an internal, circuit board mounted selecting network. The selecting network can be resistive, digital, fiber optical, black and white, or color.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of power supplying devices, and more particularly to a discretely switchable variable power supply for enabling conversion of alternating current mains to at least one of a pre-specified voltage characteristic for use with a proper appliance receiver of such power. 
     BACKGROUND OF THE INVENTION 
     Voltage and current controllable electrical power supplies are known. Some of the most expensive and user controllable power supplies have sensitive precise scientific adjustment capabilities. Smaller power supplies are available for inexpensive personal electronics as a battery replacement. However these generic battery replacements have the ability to output discrete voltage based upon a selector switch. The selector switch typically has discrete voltage selection in multiples of battery cell values, such as 3 volts, 4.5 volts, 6 volts, 9 volts and 12 volts. Such user adjustable supplies can damage equipment if the selector switch is improperly set, either too high or too low. The one saving grace of small battery replacement supplies is the low current capability. An improper setting will cause damage typically limited by the low current capability of the device. 
     Personal computers, however, have a much higher current demand. Most personal computer and lap top power supplies are specialized with specific voltage and current requirements. It is especially because the power capability is higher, that the results of placing a choice of voltage and current capability in the user&#39;s hands can cause such significant damage. Further, the destruction and damage would be expensive as the destruction of components of personal computers and laptops are much more costly than the destruction of most personal electronic equipment. 
     An earlier power converter for personal electronics equipment was seen in U.S. Pat. No. 5,347,211, incorporated by reference herein. In the scheme set forth in this reference, users were provided with a key which had an electrical component which was sensed by the main control circuitry. The voltage output was proportional to the value of a resistor in an insertable structure. Since the output of the power supply was proportional to the value of resistance, the isolation of control could be circumvented by providing an insertion structure with a variable resistance, isolation could easily be circumvented. 
     Given the value and importance of personal computers and lap tops, what is needed is a system by which control of the voltage and current output of a power supply may be effectively isolated. The mechanism of isolation should not be amenable to easy circumvention. 
     SUMMARY OF THE INVENTION 
     A switching mode power supply uses two power source inputs, an alternating current input and a direct current input. A pulse width modulation controller is used to control current from two primary windings of a transformer. The secondary of the transformer has a rectified direct current output. From the direct current output a current/voltage comparator receives a signal across a sensing resistor and through an inverter and in parallel with respect to the direct current output. The current/voltage comparator may communicate through an opto coupler/isolator and then to a pulse width modulation controller. 
     The current/voltage comparator receives its instruction about the voltage and current necessary to be supplied by the direct current output of the power supply from an internal, circuit board mounted resistor selecting network. The resistor selecting network has a number of electrical connection to a switches actuator block. The switches actuator block can have a number of switches which connect certain ones of the number of electrical connections together. The wiring inside the switches actuator block can be connected in a manner that they cannot be seen. The switch settings for certain personal computer and lap top can be given in the form of a code for setting the switches. Since the switches actuator block can be constructed to conceal which of the resistor selecting network wires are being connected, the user supplies a setting which is supplied to correspond to the voltage and current requirements for their personal computer, lap top, or other personal electronic device. For a circuit in which the voltage output is to be completely specified and controlled by the user, the switches actuator block can be wired to correspond to a binary value. In this case, the user can more easily have complete control of the power supply, and a conversion table between the binary settings on a series of dip switches and voltage outputs can be supplied. 
     As an alternative to providing dip switches and a resistor selecting network for sensing the dip switch settings, a multi conductor structure can be provided in which certain ones of the conductors are connected to multiple other conductors while some conductors are not connected. Further, the resistor sensing network can utilize multiple numbers of internal resistors along with the conductor logic in the conductor structure to supply an ultimate resistance to the current/voltage comparator. In this case, the “code” for the selector can involve conductors whose connection to each other is not known, in combination with an internal “resistor sense” network which will supply a total resistance based upon the network and the connections in the conductor structure. Physically, the conductor structure can be well covered and possibly potted to help prevent a visual discovery of the built in logic. The logic can be discerned by an extended test of the conductors in the conductor structure, but even this can be blunted by physically limiting the exposure of the conductors on the structure. 
     Other means of transmitting logic can be done fiber optically or optically by color. For fiber optics, a light conductor structure can be provided which selectively promulgates light along certain channels in the light conductor structure. For example light entering at port  1  might show up at ports  3  and  9 . Light attempting to enter ports  2  and  3  may be blocked. 
     The same logic can be implemented with black and white areas on a reflectivity and absorbance structure. The same logic can also be implemented on a color structure, or by having a series of color filters in a light filter structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention, its configuration, construction, and operation will be best further described in the following detailed description, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic block diagram of one possible configuration of a power supply system utilizing output feedback measurement, and shown with a switches actuator block control input of a current/voltage comparator; 
         FIG. 2  is a variation on the input related to the resistor selecting network and illustrating a series of conductors which make selective connection of the resistors in the resistor network; and 
         FIG. 3  is a schematic block diagram of another possible configuration of a power supply system utilizing a transformer having a pair of secondary output windings capable of supplying separate power outputs. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The power supply of the present invention can be best described initially by reference to  FIG. 1 .  FIG. 1  is a schematic block diagram of one possible configuration of a power supply system  21  utilizing output feedback measurement, and shown with one possible input device, a switches actuator block  23 . Other input devices will be shown. 
     At the upper left side of  FIG. 1 , an alternating current input line  31  may derive power from conventional mains, such as 120 volt AC mains in the U.S. &amp; Canada, or 240 volt mains in Europe. An alternating input circuit  33  takes alternating current power from the alternating current input line  31  and performs appropriate reduction, induction, resistance or other treatment as appropriate to make the power available to a diode D 2 . The output of diode D 2  is connected to a first dotted input of a first winding N 1  of a transformer L 6 . 
     At the upper left side of  FIG. 1 , and below alternating current input line  31 , a direct current input line  35  is seen. Direct current input line  35  may derive power from another smaller power supply from rectification of alternating current input line  31 , or it may derive power from a battery or other direct current source. A direct current input circuit  37  takes direct current power from the direct current input line  35  and performs appropriate reduction, induction, resistance or other treatment as appropriate to make the correct level power available to a diode D 3 . The output of diode D 2  is connected to a second dotted input of a second winding N 2  of a transformer L 6 . The output of diode D 2  is also connected to the non-dotted end of first winding N 1  of transformer L 6 . 
     Transformer L 6  has a secondary winding N 3  having a dotted terminal which is grounded with respect to the output section of the power supply system  21 . The dotted terminal of secondary winding N 3  is connected through a resistor R 9  and to a grounded output terminal  39 . The other, non dotted terminal of winding N 3  is connected through a diode D 4  and becomes a direct current output terminal  41 . 
     The dotted and non-dotted terminals of winding N 3  are connected in parallel with a capacitor C 1 . The output terminals  39  and  41  are connected by a series connected pair of resistors R 10  and R 11 . One end of Resistor R 9  is connected to one input of an comparator  43 . The other end of resistor R 9  is connected to a second input of comparator  43 . An output of the comparator  43  is connected into a current/voltage comparator  45 . 
     A control output of the current/voltage comparator  45  is fed into an opto coupler  47  which isolates the secondary winding N 3 , and its associated circuitry, of transformer L 6  from the primary windings N 1  and N 2  and their associated circuitry. 
     An output of the opto coupler  47  is fed into a pulse width modulation PWM Controller  49 . PWM controller  49  is operably connected to the gate of a MOSFET transistor Q 1 . The drain of the transistor Q 1  is connected to the non dotted lead of winding N 2  of transformer L 6 . The source of transistor Q 1  is grounded through a resistor R 13 . The source of transistor Q 1 , and its voltage, is made available to PWM controller  49  so that the PWM controller will have some feedback as to the current passing through transistor Q 1 . 
     Referring to the lower right of the diagram of  FIG. 1 , the switches actuator block has a number of conductors, which are represented by only 6 in order to not overburden the drawing. In its physical realization, the switches actuator block may be a series of dip switches  51 . The dip switches  51  may be manually actuated to a fixed position, or may be spring loaded and activated by a configuration actuator. One such configuration actuator may be a piece of plastic having a configuration of stepped surfaces so that which pushed over the switches actuator block  23 , certain of the individual switches immediately assume a configuration matching the setting of the dip switches  51  necessary to give the desired voltage and current output characteristics. 
     Regardless of the physical configuration of the switches actuator block, a series of conductors  53  are made available to a selecting network  55 . The selecting network interprets which of the conductors  53  put into contact with each other and translates the state of its conductor  53  inputs to a command output which is connected to the current/voltage comparator  45 . 
     Where the selecting network is a resistance network, the numbers and identity of conductors  53  connected together are translated to a voltage which is provided to the current/voltage comparator  45 . Where the selecting network is digital, the configuration of the conductors  53  which are connected an not connected are translated to a digital number or signal and made available to the current/voltage comparator  45 . 
     Rather than physical switches, the mating of conductors can be used to accomplish the same type of connectivity. Referring to  FIG. 2 , an alternative configuration of the structure associated with the selecting network  55  is shown. A connector  61  has a housing with internal contacts  63  and will typically be provided to the user of the power supply system  21 . The contacts  63  can be recessed inside the housing and the connectivity of the contacts by which some of the contacts  63  are shown interconnected and others are not can be hidden from view. The user connects the connector  61  into a mating connector  65  having contacts  67  connected to the previously seen conductors  53 . Thus the equivalent connectivity as would have been had with the dip switches  51  is now had with the connectivity of selected ones of the contacts  63  which is transmitted to contacts  67  upon connection. 
     Referring to  FIG. 3 , a schematic block diagram of another possible configuration of a power supply system utilizing a transformer having a pair of secondary output windings capable of supplying separate power outputs is shown. The other components seen in the circuit of  FIG. 1  are labeled as seen in  FIG. 1  and a discussion will be had with respect to the components which have changed or which have been added. 
     At the middle of  FIG. 3 , an additional winding N 4  is added to the transformer L 6 . Rectified direct current which may be of a lower value than the output current available from terminals  39  and  41  may be provided with winding N 4 . A dotted end of winding N 4  terminates at a terminal  73 . The non-dotted end of winding N 4  is supplied through a diode D 5  and through a low volt regulator  75  to become terminal  77 . Terminals  77  and  73  form one separate direct current output, while terminals  39  and  41  form another separate direct current output. 
     The low volt regulator  75  has an input connected to the dotted end of the winding N 4  in order to measure and regulate the voltage between terminals  77  and  73 . The relative currents and voltages available to the windings N 3  and N 4  will depend upon the input voltage and current and the number of turns between windings N 3  and N 4 . The low volt regulator can assist in maintaining the voltage between terminals  77  and  73  to a point below that appearing at winding N 4 . As such the design of the power supply system  21  should contemplate the relative voltages which will be needed at terminals  77  and  73 , versus the likely voltage which is expected to be needed at terminals  39  and  41 . 
     A sense lead is connected between the low volt regulator  75  and the current/voltage comparator  45  to enable the current/voltage comparator  45  to make adjustments to help maintain the relative voltages which will be needed at terminals  77  and  73  versus the likely voltage which is expected to be needed at terminals  39  and  41 , as well as to help regulate the operation of transistor Q 1  for the highest efficiency in supplying both the voltages appearing at terminals  77  and  73 , as well as at terminals  39  and  41 . 
     At the lower right side of  FIG. 3 , a fiber optic selecting network  81  is shown. A connector  83  has a series of fiber optic connectors  85  for receiving light energy, and it has fiber optic source line  87  for supplying fiber optic energy away from the connector  83 . A passive fiber optic set  89  has a series of fiber optic transmitting connectors  91  for re-directing the light supplied through fiber optic source line  87  into a corresponding series of fiber optic receiving connectors  91 . As seen not all of the fiber optic transmitting connectors  91  are connected to the line supplied by fiber optic source line  87 . Only those fiber optic connectors  85  will be illuminated which are in alignment with those of the fiber optic transmitting connectors  91  which are connected to the line receiving light from fiber optic source line  87 . In this configuration, a user simply attaches a passive fiber optic set  89  to the connector  83  which carries the fiber optic source line  87  in order to operate. The proper configuration indication for the voltages which must appear at terminals  77  and  73 , and at terminals  39  and  41  will be carried in accord with the fiber optic connectivity held within the passive fiber optic set  89 . As a result, the power supply system  21  is controlled by a logic of connectivity or optical return, and this instruction need not be linear or logical where it is desired to make average user unable to circumvent the ability to control the power supply system  21  without possession of the correct instructing structure. 
     While the present invention has been described in terms of a power supply system using a pulse width modulation controller and a coded structure to prohibit unauthorized tampering and control of the power supply (and possibly using conductivity and optical connectivity as techniques as a control mode for the coded structure), the present invention may be applied in any situation where some limited degree of control is to be given to users, but where untrammeled control, play, and experimentation on the appliance is to be prohibited. 
     Although the invention has been derived with reference to particular illustrative embodiments thereof, many changes and modifications of the invention may become apparent to those skilled in the art without departing from the spirit and scope of the invention. Therefore, included within the patent warranted hereon are all such changes and modifications as may reasonably and properly be included within the scope of this contribution to the art.