Patents by Inventor David A. Cross
David A. Cross 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).
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Publication number: 20140138359Abstract: A method of processing an optical element includes providing the optical element. A surface region of the optical element includes one or more pre-cursors. The method also includes raster scanning a laser beam across the optical element. The laser beam comprises a plurality of laser pulses, each of the laser pulses being characterized by a pulse length less than 1 ns. The method further includes exposing the one or more pre-cursors to the laser beam and observing a light emission event from one of the one or more pre-cursors.Type: ApplicationFiled: November 20, 2012Publication date: May 22, 2014Applicant: LAWRENCE LIVERMORE NATIONAL SECURITY, LLCInventors: Christopher Wren Carr, Raluca A. Negres, Mary A. Norton, David A. Cross
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Patent number: 6249444Abstract: A forward converter circuit that includes elements capable of generating a zero volt switching (ZVS) signal across the power switch. The ZVS generating elements include a series combination of a switch and shunt inductance, which are connected in parallel across the primary winding of the power transformer. An offset capacitor is placed in series with the shunt inductance and is operated in conjunction with a control circuit to couple the magnetizing current from the primary winding of the power transformer and use it to charge the offset capacitor. This provides zero volt switching of the power switch at turn-on and turn-off, and reset of the core of the power transformer without the use of a tertiary winding. The circuit also achieves added protection of the power switch without the use of an active clamp.Type: GrantFiled: November 1, 1999Date of Patent: June 19, 2001Assignee: Astec International LimitedInventor: David A. Cross
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Patent number: 6069800Abstract: Effective harmonic correction without frequency, power or voltage limitations is achieved in a single-stage DC-to-DC converter by disconnecting the bulk capacitor of a typical single-stage converter during low voltage conditions, and by using various phase and cycle modulation techniques associated with a switchable auxiliary transformer winding which charges the bulk capacitor to control its voltage. A means is thus provided to control the level of harmonics generated depending upon the level of the AC output voltage. When the auxiliary winding is used as a clamp winding, full ZVS conditions are provided for both the auxiliary winding switch and the converter's primary winding switch. Energy can then also be directed, under independent control of the switched auxiliary winding, to independent power nodes, i.e., either the output capacitance and load, or the bulk capacitor. This ensures that the output voltage will not be affected during any period needed to recharge the bulk capacitor.Type: GrantFiled: July 31, 1998Date of Patent: May 30, 2000Assignee: Astec International LimitedInventors: David A. Cross, Neal George Stewart
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Patent number: 6069803Abstract: A continuous mode flyback converter circuit which includes elements capable of generating a zero volt switching (ZVS) signal across the power switch. The ZVS generating elements include a switched shunt inductance coupled in parallel with active clamp components and connected across the primary winding of the power transformer. The circuit reduces the reverse recovery current through the secondary stage rectifier and the current through the active clamp switch during operation of the converter. The ZVS generating elements may also be used for flyback converters which do not utilize an active clamp.Type: GrantFiled: February 12, 1999Date of Patent: May 30, 2000Assignee: Astec International LimitedInventor: David A. Cross
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Patent number: 5977754Abstract: A boost converter circuit which includes elements capable of generating a zero volt switching (ZVS) signal across the power switch. The ZVS generating elements include a switched shunt inductance which is referenced to the positive rectified supply voltage instead of to the output voltage as with other ZVS techniques. This causes a reduction in the inductance value required for generating the ZVS signal, and a resulting reduction in the power loss associated with operation of the converter. The inventive circuit permits operation of the boost converter using high frequency FET devices or slower switching insulated gate bipolar junction transistors as the power switch.Type: GrantFiled: February 1, 1999Date of Patent: November 2, 1999Assignee: Astec International LimitedInventor: David A. Cross
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Patent number: 5905645Abstract: A thermally regulated power system, where the extent to which the temperature of a power module causes a change in the output power of the module depends on the output current of the module. Similarly, the extent to which the output current of the power module causes a change in the output power of the module depends on the temperature of the module. In one embodiment, a thermally regulated down slope power sharing system without a share line includes N+1 power modules coupled in parallel to the same output port, where N is an integer greater than one. The slope of the down slope curve of a power module is changed in response to the temperature of the power module such that a power module operating at a higher temperature outputs less current for a given bus voltage than a power module operating at a lower temperature.Type: GrantFiled: December 2, 1996Date of Patent: May 18, 1999Assignee: Astec International LimitedInventor: David A. Cross
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Patent number: 5796595Abstract: An interleaved flyback electrical power converter system having a plurality of flyback power converters operated in continuous mode, each converter utilizing a power switch operated under zero voltage switching conditions. The interleaved flyback power converter system is highly efficient and compact, and is suitable for use in high power, high frequency applications.Type: GrantFiled: September 5, 1997Date of Patent: August 18, 1998Assignee: Astec International LimitedInventor: David A. Cross
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Patent number: 5615097Abstract: A transient voltage protection circuit includes a normally closed switch connected between a rectifier circuit and a DC to DC converter. This switch is caused to switch to a current limit state when the voltage input to the DC to DC converter exceeds a first predetermined value, thereby protecting the DC to DC converter from voltages that exceed the converter's operational limits. The switch is returned to its normally closed state when the voltage input to the converter drops below a second predetermined lower value. A capacitor connected across the input terminals of the converter is charged up when the switch is closed and functions to supply power to the DC to DC converter when the switch is in its current limit state.Type: GrantFiled: September 20, 1994Date of Patent: March 25, 1997Assignee: Astec International, Ltd.Inventor: David A. Cross
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Patent number: 5600549Abstract: An electrical power converter system having a power factor correction circuit and a switching power converter. The power factor correction circuit converts the AC line voltage into an unregulated DC voltage referred to as the PFC voltage, which supplies an unregulated DC input voltage to the switching power converter. The switching power converter converts the unregulated DC input voltage into one or more regulated DC output voltages. The PFC voltage automatically adjusts to an appropriate value for achieving the desired power factor correction, converter efficiency, and converter temperature. In a preferred embodiment, the value of the PFC voltage is adjustable in response to a control signal produced by a PFC control circuit. The PFC control circuit measures the peak value of the input line current to determine whether the power factor is acceptable. If the power factor is acceptable, the PFC voltage will be maintained at a relatively low value.Type: GrantFiled: September 20, 1994Date of Patent: February 4, 1997Assignee: Astec International, Ltd.Inventor: David A. Cross
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Patent number: 5570278Abstract: Size reduction in a clamped power converter can be achieved, and stability of the converter under no-load and transient loads can be substantially improved, by operating the converter in a continuous flyback mode.Type: GrantFiled: February 25, 1994Date of Patent: October 29, 1996Assignee: Astec International, Ltd.Inventor: David A. Cross
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Patent number: 4353080Abstract: In a matrix array for the supply of an electrographic stylus writing apparatus, a plurality of styli are driven by short pulses through R/C networks. The styli are divided into subgroups and parallel capacitors connect the styli of each subgroup to a high voltage switch which is responsive to a capacitor pulse driver. Each stylus is also driven through a resistive line which completes the R/C circuit. The resistive lines are connected in parallel for similar styli of each group to a resistor enable pulsing circuit and all resistive lines are connected via isolation diodes to a resistor reset means. In operation, a short pulse from the capacitor driver circuit is applied to all the capacitors of a single group and an enabling pulse is applied to a predetermined single resistive line of each group so that the combined, enabled R/C circuit for a single stylus within one of groups is activated.Type: GrantFiled: December 20, 1979Date of Patent: October 5, 1982Assignee: Xerox CorporationInventor: David A. Cross