Electrical circuit for operating a fluorescent lamp and for measuring the lamp current
First Claim
1. An electrical circuit with an inverted rectifier connected to a voltage source, having a resonant circuit for operating at least one fluorescent lamp, and having means for measuring the lamp current, wherein said resonant circuit, which comprises a first one of the cathodes of said at least one lamp and a first coil of an isolating transformer, is connected between the output of said inverted rectifier and one terminal of a voltage supply source, with a second cathode of said at least one lamp being coupled to the resonant circuit through a second coil of said isolating transformer, wherein said second coil is connected in parallel to said second cathode, with said means for measuring the lamp current being means separate from said isolating transformer and being located between said second cathode of said at least one lamp and said voltage supply source.
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Accused Products
Abstract
In an electrical circuit for feeding a fluorescent lamp, a serial resonant circuit is comprised of a first coil of a feedback-transformer, a resonant inductor, a coupling condenser, a first lamp cathode, a resonant condenser, and a first coil of an isolating transformer, this serial resonant circuit being connected between the output of an inverted rectifier, connected to a voltage supply source and one terminal of said voltage supply source, with a second coil of the isolating transformer being connected in parallel with the second lamp cathode. If the coils of the isolating transformer have the same number of loops, this connection of the second lamp cathode ensures that the same heating current will flow through both lamp cathodes, so that these will be heated equally. The parallel circuit of the second lamp cathode with the second coil of the isolating transformer is connected through a resistance with a terminal of the supply voltage. The lamp current flows through this resistor, thus the voltage across the resistor is proportional to the actual current of the lamp and it can therefore be transmitted to the main circuit which regulates the lamp current.
15 Citations
15 Claims
- 1. An electrical circuit with an inverted rectifier connected to a voltage source, having a resonant circuit for operating at least one fluorescent lamp, and having means for measuring the lamp current, wherein said resonant circuit, which comprises a first one of the cathodes of said at least one lamp and a first coil of an isolating transformer, is connected between the output of said inverted rectifier and one terminal of a voltage supply source, with a second cathode of said at least one lamp being coupled to the resonant circuit through a second coil of said isolating transformer, wherein said second coil is connected in parallel to said second cathode, with said means for measuring the lamp current being means separate from said isolating transformer and being located between said second cathode of said at least one lamp and said voltage supply source.
Specification