Philips Electronics North America Corporation

Raj Jayaraman

Yongping Xia

Sreeraman Venkitasubrahmanian

Thomas Farkas

Gert W Bruning

Paul R Veldman

Joshua S Zhu

Paul Leyton

Paul Leyten

A communication method particularly suited for lighting control employs encoding of perturbations in a voltage signal having a fundamental period with a nominal waveform. A control period includes a pre-selected number of fundamental periods of the voltage signal. Different control commands are indicated by imposing a selected perturbation, such as a phase cut, on the nominal waveform with a respective occurrence signature within the control period. The control commands are decoded from the voltage signal by detecting the occurrence signature of the perturbations within each control period. Decoding is accomplished by differentiating the nominal waveform to detect encoded perturbations. The technique is particularly suited for two-wire dimming applications for gas discharge lamps, in which the voltage signal carrying the encoded commands is the sinusoidal mains voltage powering the ballast, since the encoded perturbations may be small enough so that lamp flicker is avoided even with encoded signals on the line voltage. In a favorable embodiment for dimming, no perturbations are introduced on the line voltage unless a change in the operating characteristic, for example the light level, of the electric lamp is desired. This has the advantage that when lamp operation is to be kept constant, no distortions are imposed on the mains voltage, so that flicker of the lamp(s) is completely avoided and there are no adverse effects to the power factor, THD or component stress.

Coded communication system and method for controlling an electric lamp

A ballast includes safety circuitry which senses lamp status through various phases of ballast operation. According to one feature, the ballast is prevented from supplying an output voltage upon initial energization of the ballast when a lamp is not present at the output terminals. The presence of a filament is sensed via a DC path extending through the filament heater windings of an output transformer. When the DC path is not complete, a control input, for example the power supply input of the ballast controller, is not provided with a voltage to start ballast operation. The DC path is also used to restart the ballast if a defective lamp is replaced with a good one. Over-voltage and capacitive mode detection is also disclosed to shut down ballast output upon lamp failure/removal.

Lamp controller with lamp status detection and safety circuitry

A lamp controller includes an interface circuit, or receiver, which receives an input signal and decodes control signals supplied from a transmitting device, such as a power line wall controller, according to at least two of the following communication techniques: phase angle control, step control, and coded control. The receiver tests the input signal and identifies which type of control technique is employed by the wall controller connected to the lamp controller. The receiver then decodes the control command from the input signal. In a disclosed embodiment, the lamp controller is gas discharge lamp dimming ballast having a two wire input for connection to the hot dimmed and neutral leads of the power line controller. The ballast has an improved topology in which a pre-conditioner supplies a substantially constant DC voltage to a ballast stage including an inverter, a resonant tank output and a control circuit. The dim signal output by the receiver is independent of the DC rail voltage and, in combination with the maintenance of a substantially constant DC rail voltage, permits of improved dimming control while providing the ease of installation of a two wire ballast.

Electronic ballast with interface circuitry for multiple dimming inputs

A dimming ballast for use with a phase control dimmer, and particularly a triac dimmer, includes an EMI filter selected with a high impedance to avoid excessive voltage and peak currents in the filter due to resonance with the phase controlled AC waveform at low conduction angles, when the load presented by the lamp is low. The EMI filter includes a filter capacitor connected at the output of a rectifier. The ballast also includes circuitry to sense the rectified DC voltage and to discharge the filter capacitor when the rectified voltage is at or near zero, to thereby keep the EMI filter loaded and prevent misfiring of the triac dimmer. In a favorable embodiment, the sensing and discharge function is carried out by a pre-conditioner of the switched-mode type.

Electronic ballast having a triac dimming filter with preconditioner

A gas discharge lamp dimming ballast has a two wire input for connection to the hot dimmed and neutral leads of a phase control dimmer. The ballast has an improved topology in which a pre-conditioner supplies a substantially constant DC voltage to a ballast stage including an inverter, a resonant tank output and a control circuit. A dimming interface circuit derives a dimming signal having a voltage equal to the average value of the rectified output voltage of a full-bridge rectifier feeding the pre-conditioner circuit. The dim signal is independent of the DC rail voltage and, in combination with the maintenance of a substantially constant DC rail voltage, permits of improved dimming control while providing the ease of installation of a two wire ballast. The response time of the interface circuit relative to the pre-conditioner is selected to avoid power imbalances. The ballast also includes an EMI filter and circuitry to prevent capacitive hold-up by the EMI filter of the rectified voltage to preserve the conduction angle for the interface circuit.

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Rancho Palos Verdes, CA, United States of America

Raj Jayaraman