Abstract: An apparatus and methods for balancing current in multiple negative impedance gas discharge lamp loads. Embodiments advantageously include balancing transformer configurations that are relatively cost-effective, reliable, efficient, and good performing. Embodiments include configurations that are applicable to any number of gas discharge tubes, such as cold cathode fluorescent lamps. The balancing transformer configuration techniques permit a relatively small number of power inverters, such as one power inverter, to power multiple lamps in parallel. One embodiment of a balancing transformer includes a safety winding which can be used to protect the balancing transformer in the event of a lamp failure and can be used to provide an indication of a failed lamp.

Abstract: A backlight system drives multiple lamps using balanced groups of serially-connected lamp transformers. A plurality of lamp transformers is divided into multiple transformer groups. Primary windings of the lamp transformers are coupled in series in each transformer group. Lamps are coupled to secondary windings of the lamp transformers. The transformer groups are arranged in a parallel configuration. One or more balancing transformers couple the transformer groups to a common power source. The balancing transformers divide a common current from the common power source into multiple balanced currents for the respective transformer groups.

Abstract: A method and apparatus for notifying an end user of a powered device on an Ethernet based network that the powered device will not be reliably powered due to an excess demand condition comprising: detecting an attached powered device; identifying the class of the attached powered device, the class comprising the power requirements of the attached powered device; identifying an excess demand condition; and temporarily supplying power to the attached powered device for a time interval thereby notifying an end user that the powered device is not being reliably powered because of an excess demand condition.

Abstract: A ring balancer comprising a plurality of balancing transformers facilitates current sharing in a multi-lamp backlight system. The balancing transformers have respective primary windings separately coupled in series with designated lamps and have respective secondary windings coupled together in a closed loop. The secondary windings conduct a common current and the respective primary windings conduct proportional currents to balance currents among the lamps. The ring balancer facilitates automatic lamp striking and the lamps can be advantageously driven by a common voltage source.

Abstract: An efficient and flexible current-mode driver delivers power to one or more light sources in a backlight system. In one application, the current-mode driver is configured as an inverter with an input current regulator, a non-resonant polarity-switching network, and a closely-coupled output transformer. The input current regulator can output a regulated current source in a variety of programmable wave shapes. The current-mode driver may further include a rectifier circuit and a second polarity-switching network between the closely-coupled output transformer and a lamp load. In another application, the current-mode driver delivers power to a plurality of light sources in substantially one polarity by providing a regulated current to a network of time-sharing semiconductor switches coupled in series with different light sources coupled across each semiconductor switch.

Abstract: An apparatus and method for driving a lamp are provided. In one embodiment, an inverter having four switching elements is split into two inverter arms that are deployed at separate terminals of a floating lamp structure to achieve even light output. A controller drives both inverter arms such that power switching lines do not cross the floating lamp structure. In one embodiment, the controller adjusts the brightness of the lamp structure by adjusting the phase difference between outputs of a first inverter arm relative to a second inverter arm. In one embodiment, the controller adjusts the brightness by symmetrically pulse width modulating the outputs of the first inverter arm and the second inverter arm.

Abstract: An illumination control circuit allows a user to set a desired brightness level and maintains the desired brightness level over temperature and life of a light source. The illumination control circuit uses a dual feedback loop with both optical and thermal feedbacks. The optical feedback loop controls power to the light source during normal operations. The thermal feedback loop overrides the optical feedback loop when the temperature of the light source becomes excessive.

Abstract: Methods for forming a SiC BJT having a low base resistance and minimal emitter width are provided. The methods incorporate a plated shadow metal layer overhanging the emitter mesa. The mushroom-shaped shadow metal layer can then act as either a deposition shadow mask or an ion implantation mask in subsequent steps for forming base contacts. In this way, base contacts can be formed with a variable and controllable distance from the emitter mesa defined by the lateral extent of overhang of the shadow metal layer. The same shadow masking effect can also be used to form self-aligned emitter and base wiring metals for reduction of resistance. Plating of the emitter contact layer allows avoiding subsequent photolithography steps on the top of emitter mesa; thus emitter mesa width could be minimized.

Abstract: An efficient and flexible current-mode driver delivers power to one or more light sources in a backlight system. In one application, the current-mode driver is configured as an inverter with an input current regulator, a non-resonant polarity-switching network, and a closely-coupled output transformer. The input current regulator can output a regulated current source in a variety of programmable wave shapes. The current-mode driver may further include a rectifier circuit and a second polarity-switching network between the closely-coupled output transformer and a lamp load. In another application, the current-mode driver delivers power to a plurality of light sources in substantially one polarity by providing a regulated current to a network of time-sharing semiconductor switches coupled in series with different light sources coupled across each semiconductor switch.

Abstract: A device for protecting I/O lines using low capacitance steering diodes (1200) and PIN or NIP diodes (1202), (1203) is disclosed. A low capacitance diode arrangement configured as steering diodes protect a signal line or input/output (I/O) port (1201) from high voltage transients by diverting or directing the transient to either the positive side of the power supply line (1204) or to ground (1205).

Abstract: An apparatus and method for driving a lamp are provided. In one embodiment, an inverter having four switching elements is split into two inverter arms that are deployed at separate terminals of a floating lamp structure to achieve even light output. A controller drives both inverter arms such that power switching lines do not cross the floating lamp structure. In one embodiment, the controller adjusts the brightness of the lamp structure by adjusting the phase difference between outputs of a first inverter arm relative to a second inverter arm. In one embodiment, the controller adjusts the brightness by symmetrically pulse width modulating the outputs of the first inverter arm and the second inverter arm.

Abstract: An illumination control circuit allows a user to set a desired brightness level and maintains the desired brightness level over temperature and life of a light source. The illumination control circuit uses a dual feedback loop with both optical and thermal feedbacks. The optical feedback loop controls power to the light source during normal operations. The thermal feedback loop overrides the optical feedback loop when the temperature of the light source becomes excessive.

Abstract: An efficient and flexible current-mode driver delivers power to one or more light sources in a backlight system. In one application, the current-mode driver is configured as an inverter with an input current regulator, a non-resonant polarity-switching network, and a closely-coupled output transformer. The input current regulator can output a regulated current source in a variety of programmable wave shapes. The current-mode driver may further include a rectifier circuit and a second polarity-switching network between the closely-coupled output transformer and a lamp load. In another application, the current-mode driver delivers power to a plurality of light sources in substantially one polarity by providing a regulated current to a network of time-sharing semiconductor switches coupled in series with different light sources coupled across each semiconductor switch.

Abstract: A push-pull driver for powering fluorescent lamps in a backlight system includes a transformer with three primary windings to realize the advantages of both a push-pull switching topology and a full-bridge switching topology. The first and the second primary windings alternately conduct currents in opposite polarities to generate an alternating current signal to power one or more lamps coupled to a secondary winding of the transformer. The third primary winding is short-circuited to preserve energy stored in the transformer in a null state when both the first and the second primary windings are not conducting.

Abstract: An incremental distributed driver divides power delivered to multiple lamps into two power delivery stages. The first power delivery stage operates in voltage-mode to provide a partial operating voltage to the lamps. The second power delivery stage operates in current-mode to regulate current levels for each of the lamps and to provide additional operating voltages for the respective lamps. Each of the power delivery stages includes a polarity-switching network and a common set of driving signals from a controller can be used to drive the polarity-switching networks of both power delivery stages. The first power delivery stage delivers a majority of the power to the lamps and the second power delivery stage facilitates control of individual lamps while providing the remaining power to the lamps.

Abstract: An apparatus and methods for balancing current in multiple negative impedance gas discharge lamp loads. Embodiments advantageously include balancing transformer configurations that are relatively cost-effective, reliable, and efficient. Embodiments include configurations that are applicable to an unrestrained number of gas discharge tubes, such as cold cathode fluorescent lamps. The balancing transformer configuration techniques permit a relatively small number of power inverters, such as one power inverter, to power multiple paralleled lamps or paralleled groups of lamps with balancing transformers coupling the lamps or groups of lamps in a zigzag topology. One embodiment of a balancing transformer includes a safety winding which can be used to protect the balancing transformer in the event of a lamp failure and can be used to provide an indication of a failed lamp.

Abstract: A bi-directional low capacitance TVS using a PIN or NIP diode is disclosed. Bi-directional low capacitance TVS protection circuit (1000) consists of two pairs of TVS diodes (1001), (1003) and LC PIN or NIP diodes (1002), (1004). Diodes (1003) and (1004) are in parallel and in opposite direction from a first series of TVS and LC diode pair. This circuit provides transient protection in both directions for a bi-directional low capacitance TVS.

Abstract: A compensation circuit for protecting a lamp from a large transient current. The compensation circuit may include a saw tooth generator configured to generate a saw tooth signal with an amplitude corresponding to a supply voltage of the lamp. A pulse width modulated signal may be generated by a comparator of the compensation circuit based on the saw tooth signal and a DC signal. The duty cycle of the pulse width modulated signal may be used by a controller to control the duration of time that current flows through the lamp. When the supply voltage of the lamp transitions from a low voltage to a high voltage, the amplitude of the saw tooth signal increases. When the amplitude of the saw tooth signal increases, the duty cycle of the pulse width modulated signal decreases thereby causing the controller to decrease the duration of time that current flows through the lamp.

Abstract: An apparatus and methods for balancing current in multiple negative impedance gas discharge lamp loads. Embodiments advantageously include balancing transformer configurations that are relatively cost-effective, reliable, efficient, and good performing. Embodiments include configurations that are applicable to any number of gas discharge tubes, such as cold cathode fluorescent lamps. The balancing transformer configuration techniques permit a relatively small number of power inverters, such as one power inverter, to power multiple lamps in parallel. One embodiment of a balancing transformer includes a safety winding which can be used to protect the balancing transformer in the event of a lamp failure and can be used to provide an indication of a failed lamp.

Abstract: A driver circuit or controller flexibly drives either a half-bridge or a full-bridge switching network in a backlight inverter without modification, redundant circuitry or additional components. The driver circuit includes four outputs to provide four respective driving signals that establish a periodic timing sequence using a zero-voltage switching technique for semiconductor switches in the switching network.