Abstract: A ballast for providing a dimmable fluorescent lamp (42) has a potentiometer (46) connected to AC power source (10). The potentiometer (46) is connected to a dimming circuit (44). In response to changes in the resistance of the potentiometer (46), dimming circuit (44) causes the duty cycle of a pulse width modulator (18) to change, thereby dimming the fluorescent lamp (42). A dimming disable circuit (60) disables the dimming circuit (44) when power is initially applied to the ballast (6) so that the lamp (42) will ignite.

Abstract: A capacitor (16) coupled in series with series coupled gas discharge lamps (11 and 12) will effectively block direct current from flowing through the capacitor (16). A detector circuit including a high impedance resistor (17) and transistor (18) provide an alternate path for a small direct current flow, thereby enabling a direct current voltage across the capacitor (16) to be detected. The presence or absence of this direct current voltage provides a reliable indicia of the existence or absence of a gas discharge fault.

Abstract: A backplane (3101) includes a plurality of connectors (3150, 3250, 3350) mounted on the front (3105), each connector arranged to accept a circuit board (3160, 3260, 3360) having a set of signal receptacles (3140, 3240, 3340). Each connector includes a set of connector holes (3130, 3230, 3330) positioned such that when a circuit board is mounted in the connector the set of connector holes aligns with the set of signal receptacles. Further, the backplane includes a set of backplane holes (3120, 3220, 3320) aligned with the set of connector holes. As a result, when circuit boards are mounted in the connectors, a signal bus (3107) including a plurality of sets of conductive prongs (3110, 3210, 3310) may be affixed to the back (3103) so the prongs extend through the backplane holes and connector holes to make electrical contact with the signal receptacles in the circuit boards.

Abstract: A multi-resonant circuit has a series-resonant circuit coupled to the input of an inverter. The output of the inverter is coupled to a parallel resonant circuit. The output of the parallel resonant circuit energizes a load, which could be gas discharge lamps. The operating frequency of the inverter is between the resonant frequency of the series resonant circuit and the resonant frequency of the parallel resonant circuit.

Abstract: A power supply circuit (100) for use in driving fluorescent lamps (102, 104, 106) has a current mode control voltage boost IC (144) which produces a boosted voltage and has a power control input (pin 3) and a frequency control input (pin 4). The lamps are driven by a self oscillating inverter (178, 180, 196, 198) which is powered from the voltage boost IC and which operates at a frequency independent therefrom. In order to dim the lamps a D.C. bias voltage is applied to the power control input. At the same time a commensurate D.C. bias voltage is applied to the frequency control input so as to provide power factor correction in dependence on the power produced by the voltage boost IC. The circuit thus provides a substantially constant, optimum power factor at both full and dimmed light levels.

Abstract: A ballast circuit uses an optocoupler to provide electrical isolation of the dimming control from the remainder of the ballast. The optocoupler is operated in the linear range to provide continuous dimming of the lamps. The circuit further uses a combination of diodes and a diode bridge to steer current from the current sensor during lamp out conditions so that the inverter will maintain operation at a low frequency, thereby maximizing the output voltage. A clamp winding is used to insure that the voltage does not exceed the DC rail voltage.

Abstract: An electronic ballast 10 includes a single transistor 16 that supports both power factor correction and inverter functionality. To assist in controlling voltages across this transistor 16 during all phases of operation, two dual function diodes 21 and 19 are provided.

Abstract: A first module (10) sends a message comprising a plurality of data characters to a second module (20) provided, however, that upon sending an individual data character, the first module waits to receive an acknowledgement character from the second module before proceeding to send another data character.

Abstract: The network negotiates user protocols, classes, and options between a calling user and a called user using the results to determine an optimal method of user information transport. A strategy for determining the optimal user information transport method from negotiated user protocols, classes and options includes querying the destination edge for destination related PC&O, sending this information back to the source and subsequently proceeding with traditional source to destination call processing.

Abstract: A communication network transports packetized constant bit rate data from a source to a receiver. To improve the transport of the data across the network, a method is used to enqueue the packets in a buffer prior to playing out the constant bit rate data to the receiver.

Abstract: A mechanism and method control software overloads in a communication network system to preserve the throughput capacity of the system in a simple and efficient manner. System load is regulated by accepting, deferring or rejecting work that the system is requested to perform. The criteria used to accept, defer or reject work is based on the relevance of the request and availability of system resources.

Abstract: A circuit with a transistor common to both the inverter and the boost converter powers a gas discharge lamp. In a half-bridge inverter, a boost inductor is coupled between the rectifier and the junction between two switching circuits.

Abstract: A power factor corrected electronic ballast circuit uses two transformer components. An inductively coupled charge pump technique is used for power factor correction while the gates of the transistor switches are driven directly from a resonant inductor.

Abstract: A parallel resonant circuit for powering a gas discharge lamp achieves power factor correction by using a floating power supply having adjustable voltage and impedance level. The floating power supply is powered by a transformer and placed in series with the rectified AC power line.

Abstract: A circuit for powering gas discharge lamps includes a power factor correction inductor coupled to a source of rectified, pulsating AC power. An energy storage circuit is connected to the power factor correction inductor, and a switch is coupled to a junction between the power factor correction inductor and the energy storage circuit. A resonant circuit couples the energy storage circuit to the gas discharge lamps.

Abstract: A protection circuit for electronic ballasts which use charge pump power factor correction includes a switch with an overvoltage sensor, a resistor and a diode. In the event of a fault condition, the switch disables the charge pump power factor correction, while the resistor and diode prevent the switch dissipating unduly large amounts of energy.

Abstract: A data communications device (101, 119) may be controlled from a centrally-located network management system controller (109) located some distance from the device. The data communications device is coupled to the network management system controller by a local channel (155, 157). The device includes a link adapter (133, 143) that communicates with the controller by a protocol that allows the device to exchange messages with the controller. As many as 512 devices may be coupled to the same local channel.