Electric lamp and discharge devices: systems – Condenser in the supply circuit – Condenser in shunt to the load device and the supply
Patent
1988-05-16
1991-06-11
Mis, David
Electric lamp and discharge devices: systems
Condenser in the supply circuit
Condenser in shunt to the load device and the supply
315219, 315223, 315226, 315243, 315DIG2, 315DIG5, H05B 4124, H05B 4136
Patent
active
050235192
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a circuit for starting and operating a gas discharge lamp.
A gas discharge lamp is a lamp, which emits light in an electric discharge in the gas of the gas discharge lamp. In the present context, the term "gas discharge lamp" is a generic term comprising all lamps different from incandescent lamps, such as conventional gas discharge lamps, fluorescent lamps, halide lamps and arc lamps.
Common to all gas discharge lamps is the distinct shift in the characteristic of the gas discharge lamp, when the lamp is shifted from its off-state to its on-state and further the requirement of the gas discharge lamp of exceeding a threshold of electric energy supply for switching the gas discharge lamp from its off-state to its on-state. In its off-state, the gas discharge lamp represents a high electric impedance, whereas in its on-state the gas discharge lamp represents a basically resistive load or is to be considered equivalent to a resistance of finite value. Since the electric resistance represented by the gas discharge lamp in its on-state is a decreasing function of the RMS (root mean square) current supplied to the lamp, the lamp has to be connected with a ballast impedance in series with the lamp itself in order to limit the current supply to the lamp when the lamp is in its on-state on a constant voltage supply such as a mains supply. From the above, it is further understood that a starting circuit has to be provided in order to supply sufficient energy in excess of the above mentioned threshold for shifting the gas discharge lamp form its off-state to its on-state.
A plurality of ballast and starter circuit configurations of passive and active circuit configurations are known in the art. Common to the passive circuit configurations of the ballast and starter circuits is the well-known ignition problem resulting in the emission of light flashes prior to the shift of the gas discharge lamps from their off-state to their on-state, as the passive circuit configurations are not able to positively shift the gas discharge lamps from their off-state to their on-state, and the unstable emission of light from the gas discharge lamps often perceived as a constant flickering of the light emitted. The active circuit configurations of the ballast and starter circuit known in the art are stated to eliminate the above starting and light flickering problems. However, the active circuit configurations known hitherto, have gained little commercial success. First this is because highly elaborate circuit configurations are expensive as compared to more simple passive circuit configurations. Second, it is because stability problems, e.g. when a burnt out gas discharge lamp is connected to the circuit, may result in excessive current being drawn from the circuit resulting in the destruction of the active high power components of the circuit.
Therefore, there is a need for a circuit for starting and operating a gas discharge lamp in which the circuit on the one hand eliminates the problems associated with the passive circuit configurations, i.e. which is capable of positively shifting the gas discharge lamp from its off-state to its on-state without emitting light flashes. One is further needed, which, hand, is of a fairly simple configuration as compared to the active configurations known hitherto. Finally, one is needed which positively limits the current or power supplied from the active power supply components of the circuit when the circuit is connected to a low impedance load such as a burnt out gas discharge lamp or a defective gas discharge lamp. The above object is obtained by a circuit according to the present invention for starting and operating a gas discharge lamp, comprising: specific oscillator frequency across two output terminals of said oscillator means, having a frequency of resonance substantially identical to said oscillator frequency, connected in a series configuration across said output terminals, and said gas discharge lamp being connected across said parallel-resonance circui
REFERENCES:
patent: 4388562 (1983-06-01), Josephson
patent: 4701673 (1987-10-01), Lagree et al.
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