Abstract: A high frequency dimming ballast dims to about 1 percent of rated output in a repeatable way so that parallel connected dimming ballasts will all produce the same light illumination when dimmed to a very low percentage of their rated light output. A first current sensor is connected in series with a semiconductor power switching device which is coupled to and controls power to the ballast. A second current sensor is connected directly to the lamp circuit to detect actual lamp current, particularly at low illumination conditions, for example at less than 10 percent of the rated light output. Lamp control under low illumination conditions is derived from the lamp current sensor and overrides control by the sensor in series with the transistor switch means.

Abstract: A power control system for gas discharge lamps and other loads. According to a preferred embodiment, the system includes a main divertor in series or parallel with the load, and a variable divertor, which includes a controllably conductive device controlled by a control circuit, the variable divertor being selectively inserted in series with the load during each half cycle of the output voltage signal. The system obtains an improved load voltage waveform giving superior performance under reduced power output conditions. This system can be applied to a fluorescent lighting circuit having a plurality of conventional ballasts, achieving a dimming ratio of greater than 4 to 1, and can also be applied to other gas discharge lamp circuits, including high intensity discharge lamp circuits, to incandescent lamps, and to motors such as fan motors. It can further be applied to control the power supplied to solid-state switching units, including those having capacitive inputs.

Abstract: A high frequency gas discharge lamp dimming ballast with good line power factor is disclosed. The unit is controlled by a current sensing loop which senses control switch current rather than lamp current and employs simple circuitry with sufficiently rapid control response necessary to maintain high line power factor and stable lamp operating characteristics over a very wide range of light output. An isolated output transformer provides protection against most common miswire conditions and accurately regulates lamp energy over a wide range of input and lamp arc voltage conditions. A pulse width modulated control input provides an isolated control input for easier wiring and reduces the susceptibility of the control to noise interference.

Abstract: Individual banks of gas discharge lamps are provided with a common dimming control system. If a bank of lights is turned on while others are on and in a dimmed condition, the voltage applied to all lamps is increased over a relatively short period of time to full voltage to ensure the proper striking of the new bank of lamps but over a sufficiently long time period that users of the dimmed banks of lamps will not be noticeably affected by the change in lamp output. Full power is then maintained for a sufficiently long time to ensure proper lamp striking and stabilization and all banks are then very gradually returned to the original dimmed illumination condition which was set before the new lamp bank was energized. A long time delay and a short time delay are applied to respective inputs of a comparator to enable the initiation of the lamp striking sequence for the new lamp bank and prevents the initiation of the lamp striking sequence due to short time disturbances on the line.

Abstract: A gas discharge lamp control circuit for an inductive ballast includes anti-parallel connected controlled rectifiers connected in series with the a.c. source and the ballast and anti-parallel connected controlled rectifiers which are connected in series with a current limiting and energy diversion capacitor and in shunt with the ballast. The controlled rectifiers of the series and shunt switching assemblies are controlled so that, in any given half wave, the related controlled rectifier of the shunt switching means turns on to discharge a capacitor into the normally conducting controlled rectifier of the series switching means to produce a notch in the voltage wave form applied to the inductive ballast. The capacitor acts as a current limiting impedance and acts to permit reversal of the voltage during the notch interval in the input voltage to the ballast, thereby to increase the RMS content of the voltage wave form.

Abstract: The input energy to a gas discharge lamp is controlled over a given range to obtain output light regulation in a controlled fashion for different kinds of gas discharge lamps, including fluorescent lamps, high intensity discharge lamps and others associated with any type ballast, including conventional non-dimming type ballasts. A suitable circuit switches each half wave of an input a-c wave form from some instantaneous value greater than zero to a substantially zero value and then back to a value greater than zero one or more times in each half cycle. The time duration of the substantially zero energy interval is varied to vary the total energy applied to the gas discharge lamps. In a preferred embodiment, a first high speed electronic switch is connected in series with the a-c source and lamp ballast and a high speed electronic shunt switch is connected across the a-c line and ballast input. The series switch is opened to produce the zero energy interval.

Abstract: A d-c power supply is described which is energized from a relatively low frequency power source and produces a d-c output voltage with low ripple and high power factor. An inductance-capacitance circuit is connected in series with the a-c source and the a-c side of the rectifying element. A filter capacitor is connected to the d-c side of the rectifying element. The inductance-capacitance circuit resonates at a frequency of about three to six times the frequency of the input power supply. A plurality of circuits for carrying out the invention are disclosed.

Abstract: An illumination control system for gas discharge lamps which can be dimmed is provided in which a central inverter produces a sinusoidal output voltage at about 23 kHz. The amplitude of the inverter output is adjustable to dim the lamps. A transmission line consisting of spaced wires having respective thick insulation sheaths distributes the high frequency power to remotely located assemblies of ballasts and lamps. The ballasts consist of passive linear components. A high power factor rectifier network is disclosed for providing a d-c input to the inverter from the 50/60 Hz mains. The inverter circuit is provided with novel controls for gradual start-up and turn-off and is protected against load fault currents and internal fault currents. Automatic and manual resets are provided for internal fault current and load fault current, respectively. The basic inverter circuit consists of two alternately conducting controllably conductive power switching devices.

Abstract: An illumination control system for gas discharge lamps which can be dimmed is provided in which a central inverter produces sinusoidal output voltage at about 23 kHz. The amplitude of the inverter output is adjustable to dim the lamps. A transmission line consisting of spaced wires having respective thick insulation sheaths distributes the high frequency power to remotely located assemblies of ballasts and lamps. A high power factor rectifier network is disclosed for providing a d-c input to the inverter from the 50/60 Hz mains. Several ballasts are disclosed, which consist principally of circuits using passive linear components. Some of the ballasts disclosed are conjugate ballasts which are those made of complex conjugate impedances which resonate with or near the input power frequency. Some ballasts disclosed are non-linear when the lamp is out in order to limit the open circuit voltage. The ballasts disclosed all have the following characteristics:(a) good power factor (above 0.

Abstract: An illumination control system for gas discharge lamps which can be dimmed is provided in which a central inverter produces an output voltage at a high frequency which can be about 23 kHz. The amplitude of the inverter output is adjustable to dim the lamps. A transmission line consisting of spaced wires having respective thick insulation sheaths distributes the high frequency power to remotely located assemblies of ballasts and lamps. The ballasts consist of passive linear components. A high power factor rectifier network is disclosed for providing a d-c input to the inverter from the 50/60 Hz mains.