Abstract:
Methods and apparatus are presented which converts a DC voltage into both a regulated boost voltage and a regulated inverter by means of switch-capacitors with feedback. Methods and apparatus may be fabricated as an integrated circuit, and/or may be fabricated with one and/or multiple communication line transceivers on a single silicon substrate.

Description:
FIELD OF INVENTION  
       [0001]     The present invention relates generally to the field of voltage conversion, and particular to a regulated voltage boost (step-up) and a regulated inverter DC to DC converter, that executes the bi-polar voltage conversions by means of switching capacitors.  
       DISCUSSION OF RELATED ART  
       [0002]     Most electronic components require at least one single power source such as batteries to power up its circuitries. Within a system, a large number of electronic components perform different functions that might require different power supply voltages to reduce overall system power consumption. DC to DC converters have long provided different voltages for different groups of electronic components. For example, in a computer system, the data communication might require two differential voltages to optimize performance and maximize transmission distance.  
         [0003]     In general, DC to DC conversion can be classified into either boost (step-up) converter, in which the input voltage will be stepped-up to an output voltage that is higher than its input voltage, or buck (step-down) converter, in which the input voltage will be stepped-down to an output voltage that is lower than its input voltage. Depending on electrical requirements, converters can be implemented by means of an external inductor coil, or by some external capacitors. DC to DC conversion can be implemented in integrated circuits by a wide variety of commonly available means.  
         [0004]     For example, U.S. Patent (U.S. Pat. No. 5,649,210) assigned to Maxim discloses a charge pump having all MOS transistors as switching elements to generate both boost and buck voltages. Unfortunately, its amplitude of buck voltages always falls short of its amplitude of boost voltage, compromising the buck voltage over the boost voltage.  
         [0005]     Also, U.S. Patent to Chan (U.S. Pat. No. 5,306,954) discloses a charge pump using all MOS transistors as switching elements and four phases of shifting, but this device suffers from power inefficiency.  
       OBJECTS OF THE INVENTION  
       [0006]     The present invention relates to a voltage converter that generates both higher than input voltage (boost) and regulated inverter voltage, by means of external capacitors. The amplitude of the regulated inverter voltage is even higher than the boost voltage so as to optimize the performance of the switching capacitors and improve the overall power efficiency. Since stability of the generated voltages, either boost voltage or inverter voltage, is critical to the functionality and reliability of electronic components, the present invention provides a mean of regulating both the boost and the inverter voltages to achieve compliant voltage levels when used in data communication line drivers and receivers regardless of power supply fluctuations.  
       SUMMARY OF THE INVENTION  
       [0007]     Methods and apparatus are presented which converts a DC voltage into both a regulated boost voltage and a regulated Inverter by means of switch-capacitors. When used with data communication line drivers and receivers, it provides true compliant voltage levels regardless of power supply fluctuation, and provides a better power efficiency and super low power consumption. Embodiments for this bi-polar voltages generation, regulation, and implementation are disclosed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a block diagram illustrating a preferred embodiment of a switch-capacitor regulated boost converter and inverter in accordance with the invention.  
         [0009]      FIG. 2  is a schematic drawing illustrating a preferred embodiment of switching capacitors going through two clock phase-shifting in accordance with the invention.  
         [0010]      FIG. 3  is a schematic diagram illustrating a preferred embodiment of circuit implementation of switching capacitors in accordance with the invention.  
         [0011]      FIG. 4  is a block diagram illustrating a preferred embodiment of an intelligent bi-directional switch symbol in accordance with  FIG. 3 .  
         [0012]      FIG. 5  is a schematic diagram illustrating a preferred embodiment of circuit implementation in accordance with  FIG. 4 .  
         [0013]      FIG. 6  is a schematic drawing illustrating a preferred embodiment of an equivalence in accordance with  FIG. 5 .  
         [0014]      FIG. 7  is a block diagram illustrating a preferred embodiment of voltage regulation in accordance with the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]     Referring to  FIG. 1 , an embodiment of a switch-capacitor regulated boost converter and Inverter block  100  of the invention is illustrated. In the embodiment shown, the converter block  100  consists of a regulated oscillator block  110 , a 2-phase cycling block  120 , and a switch capacitors block  130 . It is possible to integrate the converter block  100  with other electronics in a single substrate silicon, for example, data communication line drivers and receivers such as EIA-232.  
         [0016]     In one embodiment, the regulated oscillator block  110  provides a pre-determined oscillation frequency to the 2-phase cycling block  120 , such that its oscillation frequency  135  is in response to the boosted voltage level feedback  115  and the inverted voltage level feedback  125 . The oscillation frequency  135  output from the regulated oscillator block  110  becomes the input of the 2-phase cycling block  120 . The 2-phase cycling block  120  exhibits a repetitive two phases of oscillation and output a set of control signals  145  to control the switching of capacitors in the switch capacitors block  130 . The switch capacitor block  130  provides a mean of current sourcing  155  with a boosted voltage level  175 , and a mean of current sinking  165  with an inverted voltage level  185 . The converter block  100  takes in a range input voltages  195 , and boost up an output voltage  175  capable of sourcing a pre-determined amount of current  155 , and an inverter output voltage  185  capable of sinking a pre-determined amount of current  165 . For example, the input voltage  195  can range from 3.0V to 5.5V, the boosted output voltage  175  is at +5.4V capable of sourcing a pre-determined amount of current to ground, and the regulated inverter output voltage  185  is at −5.6V capable of sinking a pre-determined amount of current to ground. The amount of source or sink current is inter-related to the oscillation frequency, switch capacitor capacity and their respective controlling switches and devices.  
         [0017]      FIG. 2  shows an embodiment of the switching capacitors block in two clock phase-shifting in accordance with the invention. In the embodiment shown, during phase 1, one of the terminals of the switch capacitor  140  is connected to the supply voltage VCC through a switching device  150 , while the other terminal of the switch capacitor  140  is connected to Ground through a switching device  200 . This connectivity allows the switching capacitor  140  to accumulate charges with an electric potential in equivalence to VCC. One of the terminals of the switch capacitor  170  is connected to Ground through a switching device  180 , while the other terminal of the switch capacitor  170  is connected to VSS through a switching device  160 . VSS is an electric potential more negative than Ground and its charges are stored by a VSS storage capacitor  190 . This connectivity allows charges accumulated on the switching capacitor  170  be transferred onto the VSS storage capacitor  190 .  
         [0018]     In phase 2, one of the terminals of the switch capacitor  140  is now connected to VDD through a switching device  210 . VDD is an electric potential more positive than VCC and its charges are stored by a VDD storage capacitor  260 . The other terminal of the switching capacitor  140  is connected to VCC through a switching device  230 . At the same time, one of the terminals of the switch capacitor  170  is also connected to VDD through a switching device  240 , while the other terminal of the switching capacitor  170  is connected to Ground through a switching device  270 . This connectivity allows charges accumulated on switching capacitor  140  be transferred onto both the switching capacitor  170  and VDD storage capacitor  260 .  
         [0019]     These two phases of shifting continues on to allow charges be accumulated and transferred to VDD and VSS storage capacitors alternately.  
         [0020]     Referring to  FIG. 3 , an embodiment of circuit implementation of the switching capacitors in accordance with the invention is illustrated. The switching devices described previously are represented here as  280 ,  350 ,  360 ,  310 ,  300 ,  290 ,  370 , and  380 . The switching device  310  in the figure is drawn as a passive diode, and can be also implemented as a switching device. The switching capacitors  340  and  320 , as well as the VDD storage capacitor  330  and the VSS storage capacitor  390  can be implemented using discrete components. Size of these capacitors is also related to the amount of source or sink current that VDD or VSS can provide, respectively.  
         [0021]     In  FIG. 4 , a block diagram illustrating a preferred embodiment of a symbol in accordance with  FIG. 3  is shown. The circuit implementation in accordance with  FIG. 4  is illustrated in  FIG. 5 , with its equivalence illustrated in  FIG. 6 . The switching device symbol  400  can be unidirectional such as a passive diode, or can be bidirectional as implemented in  FIG. 5 . In  FIG. 5 , the PMOS  410  and NMOS  420 , together forms a transmission gate, in which an inverter  430  controls its conduction in either direction. The amount of charges allow to go through this switching device  400  can be controlled by the oscillation frequency, VCC, or other logical operation. This variation of charges conduction can be modeled as a variable resistor  440 , as illustrated in  FIG. 6 .  
         [0022]     Referring to  FIG. 7 , an embodiment of voltage regulation in accordance with the invention is illustrated. Both the VDD and VSS voltage level are compared with a reference voltage level to determine if VDD or VSS voltage level reaches the pre-determined level. In an alternative embodiment, the actual amount of the source current and sink current can be compared with the reference voltage through some resistance.  
         [0023]     The comparing function  450  outputs a voltage level to control the current sourcing source  460 , which in turns regulates both the VDD voltage level and the amount of source current  470 . The comparing function  450  also outputs a voltage level to control the current sinking source  480 , which in turns regulates both the VSS voltage level and the amount of sink current  490 .  
         [0000]     Call Out List  
         [0024]      100  Inverter Block  
         [0025]      110  Regulated Oscillator Block  
         [0026]      120  Two-Phase Cycling Block  
         [0027]      130  Switch Capacitors Block  
         [0028]      135  Oscillation Frequency  
         [0029]      115  Boosted voltage Level Feedback  
         [0030]      125  Inverted Voltage Level Feedback  
         [0031]      145  Control Signals  
         [0032]      155  Current Sourcing  
         [0033]      165  Current Sinking  
         [0034]      140   170  Switch Capacitors  
         [0035]      150   160   180   200  Switching Devices  
         [0036]      175  Boosted Voltage Level  
         [0037]      185  Inverted Voltage Level  
         [0038]      190  VSS Storage Capacitor  
         [0039]      195  Input Voltages  
         [0040]      210   230   240   270  Switching Device  
         [0041]      260  VDD Storage Capacitor  
         [0042]      280   290   300   310   350   360   370   380  Switching Devices  
         [0043]      320   340  Switching Capacitors  
         [0044]      330  VDD Storage Capacitor  
         [0045]      390  VSS Storage Capacitor  
         [0046]      400  Switching Device Symbol  
         [0047]      410  PMOS  
         [0048]      420  NMOS  
         [0049]      430  Inverter  
         [0050]      440  Variable Resistor  
         [0051]      450  Comparing Function  
         [0052]      460   470  Current Source  
         [0053]      480  Current Sinking Source  
         [0054]      490  Sinking Current