Patents by Inventor David S. Lo

David S. Lo has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 5132888
    Abstract: A DC to DC power converter is implemented which includes an input switching circuit, an input capacitor, a transformer and an output rectifying switching circuit coupled to the transformer. The input switching circuit consists of a minimum of four transistors which are operated in a timed relationship such that bi-directional currents are developed in both primary windings. The output rectifying switching circuit is operated with switching transistors that provide zero-voltage resonant transition (ZVRT) switching. Timing relationships between the input signals control the ZVRT with switching of the transistors. Bidirectional currents in the primary windings of the single transformer element permit a reduction in volume of the magnetic element and the coils of the transformer for a given level of output power.
    Type: Grant
    Filed: January 7, 1991
    Date of Patent: July 21, 1992
    Assignee: Unisys Corporation
    Inventors: David S. Lo, Joseph H. Mulkern
  • Patent number: 5057986
    Abstract: A single-ended DC-to-DC power converter which is operative at very high switching frequencies with zero-voltage resonant transition switching. A single magnetic element functions as both a storage inductor and a transformer. A charging capacitor is switched to induce a reversal current through the inductor for providing the zero-voltage switching function. Control to output characteristics are identical to those of conventional buck and buck-boost converters. The invention provides efficient, high-frequency operation and isolation of the output from the input power source with minimal component volume. The control system is adaptable to constant frequency pulse width modulation for voltage regulation.
    Type: Grant
    Filed: March 12, 1990
    Date of Patent: October 15, 1991
    Assignee: Unisys Corporation
    Inventors: Christopher P. Henze, David S. Lo, Hubert C. Martin, Jr.
  • Patent number: 4692899
    Abstract: Stabilization of the propagation of storage bits around the storage loops of a Vertical Bloch Line (VBL) memory is obtained by the vapor-deposition of a nickel-iron film over the VBL structure. The film has a composition range of 65-90% nickel and a thickness of 1,000 to 10,000 Angstroms, and is deposited in a vacuum of 10.sup.-4 to 10.sup.-6 Torr to provide parallel, periodic, magnetic stripe domains, and thus potential well domains, that have a periodicity in the range of 0.1 to 1 micron. The stripe domains are oriented perpendicular to the direction of data propagation and form potential wells along the elongated direction of the storage loops.
    Type: Grant
    Filed: December 12, 1985
    Date of Patent: September 8, 1987
    Assignee: Sperry Corporation
    Inventors: David S. Lo, Stanley J. Lins
  • Patent number: 4587636
    Abstract: The memory system incorporates a memory element storing binary digital data in the presence, vel non, of a Y-domain cross-tie. The memory element has a planar contour that is substantially symmetrical about a longitudinal axis and that has edge portions that are nowhere perpendicular or parallel to the longitudinal axis. A stabilizing magnetic field applied perpendicular to the longitudinal axis and in the plane of the memory element forms a first Neel wall along the longitudinal axis and causes the magnetization in the memory element to be formed into first and second domains on opposite sides of the Neel wall. When a writing magnetic field oriented in the plane of the memory element and perpendicular to the longitudinal axis but opposite to the stabilizing magnetic field orientation is coupled to the memory element, there is formed in the memory element a third domain separated from the first and second domains by second and third Neel walls having a join with one end of the first Neel wall.
    Type: Grant
    Filed: February 8, 1985
    Date of Patent: May 6, 1986
    Assignee: Sperry Corporation
    Inventors: Gregory J. Cosimini, David S. Lo, Lawrence G. Zierhut
  • Patent number: 4473893
    Abstract: A nondestructive readout, random access memory system is disclosed. The memory is formed of a plurality of discrete thin ferromagnetic film memory elements in which binary data are stored as the presence, or absence, of cross-tie, Bloch-line pairs. Column lines and row lines form a matrix array of the memory elements, one at each column line, row line intersection. Cross-tie, Bloch-line pairs are formed in the memory elements by the selective coincidence of row line and column line write drive fields while readout of the presence, or absence, of the cross-tie, Bloch-line pair is by a coincident row line read drive field and a column read current signal that flows through the memory elements aligned along a selected column. A read amplifier is differentially coupled across the one fully selected memory element to detect a first, or second, opposite polarity output signal that is indicative of the presence, or absence, of a cross-tie, Bloch-line pair at the one fully selected memory element.
    Type: Grant
    Filed: June 1, 1982
    Date of Patent: September 25, 1984
    Assignee: Sperry Corporation
    Inventors: Lawrence G. Zierhut, David S. Lo
  • Patent number: 4418400
    Abstract: An improved magnetic memory system in which binary data are stored as cross-tie, Bloch-line pairs, which are serially propagated downstream along a cross-tie wall in a magnetizable layer by appropriate drive fields. The magnetizable layer is configured into a data track whose two opposing edges are formed into patterns of asymmetrically shaped edges which form successive narrow portions with wide portions therebetween, and which are formed about the geometric centerline of the data track. The improvement comprises forming a plurality of energy wells along the geometric centerline of the data track and, transverse to the geometric centerline of the data track in the areas of the narrow portions where the cross-ties are stored but not in the areas of the geometric centerline.
    Type: Grant
    Filed: December 22, 1980
    Date of Patent: November 29, 1983
    Assignee: Sperry Corporation
    Inventors: Gregory J. Cosimini, David S. Lo, Maynard C. Paul
  • Patent number: 4410963
    Abstract: An improved magnetic memory system in which binary data are stored as cross-tie, Bloch-line pairs, which are serially propagated downstream along a cross-tie wall and a magnetizable layer by appropriate drive fields. The magnetizable layer is configured into a data track whose two mirror-image, opposing edges are formed into patterns of asymmetrically shaped edges which form successive narrow portions, or necks, with wide portions therebetween, and which shaped edges are formed about the geometric central line of the data track. The cross-ties are structured in the data track by opposite-edge necks at which the ends of the cross-tie are magnetically stable.
    Type: Grant
    Filed: October 5, 1981
    Date of Patent: October 18, 1983
    Assignee: Sperry Corporation
    Inventors: David S. Lo, Maynard C. Paul, Lawrence G. Zierhut
  • Patent number: 4253160
    Abstract: Disclosed is a cross-tie wall memory system for the generating, propagating and detecting of binary data represented by the presence or absence of cross-tie, Bloch-line pairs along a cross-tie wall in a thin magnetic layer. The system includes a three-level structure comprised of the following superposed layers: a straight-edged current conductive stripline; a serrated-edged thin magnetic layer data track, and a wide-narrow-edged current conductive stripline terminated on one end by a cross-tie, Bloch-line pair generator. A cross-tie detector is positioned intermediate the ends of the data track and is sandwiched between the data track and the wide-narrow-edged current conductive stripline. An N-bit data word is stored in the data track between the generator and the detector, is shifted through the detector for readout of the stored data word and is then restored into its original stored position by being shifted in a reverse manner along the data track and back through the detector.
    Type: Grant
    Filed: September 6, 1979
    Date of Patent: February 24, 1981
    Assignee: Sperry Corporation
    Inventors: Maynard C. Paul, Stanley J. Lins, David S. Lo
  • Patent number: 4253161
    Abstract: Disclosed is a cross-tie wall memory system for the generating, propagating and detecting of binary data represented by the presence or absence of cross-tie, Bloch-line pairs along a cross-tie wall in a thin magnetic data track. The system includes a three-level shift register structure comprised of the following layers: first and second substantially similar, serrated-edged current conductive striplines and a serrated-edged thin magnetic layer data track. The shift register is terminated on one end by a cross-tie, Bloch-line pair generator and on the other end by a cross-tie detector. A data word is stored in the data track between the generator and the detector and is shifted through the detector for readout of the stored data word. The first and second serrated-edged striplines are formed of alternate wide-narrow portions with the wide portion of one stripline oriented above/below the narrow portion of the other stripline.
    Type: Grant
    Filed: October 15, 1979
    Date of Patent: February 24, 1981
    Assignee: Sperry Corporation
    Inventors: Maynard C. Paul, David S. Lo, Ernest J. Torok
  • Patent number: 4250565
    Abstract: Disclosed is a cross-tie wall memory system for the generating, propagating and detecting of binary data represented by the presence or absence of cross-tie, Bloch-line pairs along a cross-tie wall in a thin magnetic layer. The system includes a three-level structure comprised of the following superposed layers: a straight-edged current conductive stripline; a serrated-edged thin magnetic layer data track, and a wide-narrow-edged current conductive stripline terminated on one end by a cross-tie, Bloch-line pair generator and on the other end by a cross-tie detector.
    Type: Grant
    Filed: February 23, 1979
    Date of Patent: February 10, 1981
    Assignee: Sperry Corporation
    Inventors: Gregory J. Cosimini, Leslie H. Johnson, David S. Lo, George F. Nelson, Maynard C. Paul
  • Patent number: 4208725
    Abstract: A method of and a detector for magneto-resistively reading out the information that is stored in a cross-tie wall memory system. The detector includes two current conductive elements that are positioned along and across the cross-tie wall in a magnetic film that is configured into a data track for sandwiching a plurality of memory cells therebetween. A separate current conductive element is centered over each of the sandwiched memory cells for conducting the read current drive signal out of the data track in the area of the Bloch-line, but forcing the read current drive signal through the data track in the area of the cross-tie. A stored binary 1, represented by a cross-tie, Bloch-line pair, is propagated into one end of the detector and is replicated in all of the sandwiched memory cells; conversely, a stored binary O, represented by the absence of a cross-tie, Bloch-line pair, would be replicated in all of the sandwiched memory cells.
    Type: Grant
    Filed: February 23, 1979
    Date of Patent: June 17, 1980
    Assignee: Sperry Corporation
    Inventors: Maynard C. Paul, David S. Lo
  • Patent number: 4198686
    Abstract: A method of and an apparatus for counting is disclosed. The counter includes a generator of cross-tie, Bloch-line pairs and a shift register of N stages or memory cells along which the cross-tie, Bloch-line pairs are propagated or replicated into a detector. The method includes coupling a series of bipolar push-nucleate replicate signals, each one of which produces a cross-tie, Bloch-line pair in the adjacent downstream memory cell along the shift register. When the shift register is filled, a cross-tie will appear in the detector. This provides an output signal indicating that the N memory cells have been filled by the N replicate signals.
    Type: Grant
    Filed: February 23, 1979
    Date of Patent: April 15, 1980
    Assignee: Sperry Corporation
    Inventors: George F. Nelson, Gregory J. Cosimini, Leslie H. Johnson, David S. Lo, Maynard C. Paul, Ernest J. Torok
  • Patent number: 4161789
    Abstract: A method of and an apparatus for reading out the information that is stored in a magnetizable layer that is formed of a thin film in which data are stored as inverted Neel wall sections about associated Bloch-lines along a cross-tie wall. The apparatus utilizes a magnetizable layer which is configured into a strip whose two opposing edges are, along its longitudinal axis, formed into mirror-imaged, spaced-apart, repetitive, asymmetrically-shaped patterns which repetitive patterns are formed of successive narrow portions that form wide portions therebetween. The repetitive patterns, when suitable magnetic fields are coupled thereto, form a cross-tie wall along the longitudinal axis of the strip while structuring the cross-ties along the cross-tie wall at the narrow portions and the Bloch-lines along the cross-tie walls and between the adjacent narrow portions.
    Type: Grant
    Filed: July 3, 1978
    Date of Patent: July 17, 1979
    Assignee: Sperry Rand Corporation
    Inventors: Ernest J. Torok, Maynard C. Paul, David S. Lo
  • Patent number: 4146930
    Abstract: An apparatus for and a method of optically recording or writing data into a thermoplastic layer is disclosed. The recording medium is fabricated as an integral part of the face of a cathode ray tube (CRT) and includes a layer of thermoplastic material that is thermoplastically responsive to a heating light beam having a wavelength within the infrared (IR) range and that is a dielectric capable of storing charges corresponding to a data-containing charging (electron) beam. The thermoplastic layer is first selectively exposed to the charging (electron) beam for spatially selectively electrically charging the exposed surface of the thermoplastic layer and is then softened by the heating (IR) beam causing the charged, softened surface to distort under the forces of the data-bearing charge.
    Type: Grant
    Filed: December 5, 1977
    Date of Patent: March 27, 1979
    Assignee: Sperry Rand Corporation
    Inventors: Roger W. Honebrink, David S. Lo
  • Patent number: 4141080
    Abstract: A method of and an apparatus for reading out the informaton that is stored in the magnetizable layer of a cross-tie wall memory system is disclosed. A first embodiment of the apparatus utilizes: a conductive probe, that along its length and is conductively coupled to the magnetizable layer and the tip which is centered at or near the Bloch-line position in the memory segment of the cross-tie wall; a conductive crescent that is oriented concentric to the probe tip and that along its length is conductively coupled to the magnetizable layer; and a readout device that is coupled across the probe and crescent for determining the resistance in the magnetizable layer between the probe tip and crescent as an indicaton of the existence or non-existence of a Bloch-line in the memory segment.
    Type: Grant
    Filed: January 16, 1978
    Date of Patent: February 20, 1979
    Assignee: Sperry Rand Corporation
    Inventors: Maynard C. Paul, Leslie H. Johnson, David S. Lo
  • Patent number: 4024515
    Abstract: The method of and a configuration for reading out the information that is stored in a cross-tie wall memory system is disclosed. The apparatus utilizes: a continuously, relatively long, sense line that is aligned along and straddles the cross-tie wall; a first polarity hard axis drive field H.sub.Tt that passes, if in existence, a stored-1-representing-Bloch-line from a memory segment along the cross-tie wall into, along and past the continuous sense line; a second polarity hard axis drive field H.sub.Tn that nucleates many Bloch-lines at once along the cross-tie wall in the area of the sense line for causing the nucleating Bloch-lines to induce in the sense line an output signal that is indicative of the change in polarity of the Neel wall vectors within the cross-tie wall in the area of the sense line and, accordingly, whether or not a stored-1-representing-Bloch-line had been stored previously in the memory segment.
    Type: Grant
    Filed: August 28, 1975
    Date of Patent: May 17, 1977
    Assignee: Sperry Rand Corporation
    Inventors: Ernest J. Torok, David S. Lo
  • Patent number: 4001795
    Abstract: A method of and a configuration for reading out the information that is stored in a cross-tie wall memory system is disclosed. The apparatus utilizes: a cross-tie, Bloch-line pair transfer system for bit-serially moving a bit-defining-Bloch-line along the cross-tie wall into a memory segment; a noise-cancelling figure-8 sense line that straddles the cross-tie wall; a hard axis drive field H.sub.T that passes, if in existence, a bit-defining-Bloch-line out of the memory segment into one of the loops of the sense line and thus inducing in the sense line loop an output signal that is indicative of the passing, or not, of the Bloch-line into the sense line loop.
    Type: Grant
    Filed: August 28, 1975
    Date of Patent: January 4, 1977
    Assignee: Sperry Rand Corporation
    Inventors: David S. Lo, Maynard C. Paul
  • Patent number: 3995280
    Abstract: A method of and an apparatus for achieving consistent recording or writing of optical data in thermoplastic films is disclosed. An empirically determined level of developing energy E is set into a heat controller that applies developing energy E (heat) to the thermoplastic film that had been previously subjected to an electrostatic charge and an optical signal (light). The monitored frost intensity F.sub.m is then compared to an empirically determined desired frost intensity F.sub.d. If F.sub.m .noteq. F.sub.d the developing energy E that is to be applied to the thermoplastic film is adjusted accordingly in preparation for the next writing operation. Control of the writing process is through control of the developing energy E that is applied to the thermoplastic film with all other developing parameters held relatively constant.
    Type: Grant
    Filed: January 2, 1975
    Date of Patent: November 30, 1976
    Assignee: Sperry Rand Corporation
    Inventors: David S. Lo, Leslie H. Johnson, Roger W. Honebrink