Lamp bulb having integrated RFI suppression and method of restricting RFI to selected level

A method of restricting emitted radio frequency interference emitted from an incandescent lamp having a translucent housing and a filament within the housing for emitting light when the lamp is energized by electrical current from an AC power source passing through the filament, comprising the steps of:

• locating a current change limiting element, comprising of an inductor assembly, within the lamp;
• electrically connecting the filament to the current change limiting element;
• limiting a rate of change in current per change in time (di/dt) passing through the filament by
• selecting the current change limiting element to have characteristics to establish the rate of change in current per change in time (di/dt) passing through the filament to a predetermined di/dt value in response to a substantially instantaneous change in voltage from the AC power source applied substantially instantaneously across the filament;
• establishing the predetermined di/dt value to limit radio frequency interference (RFI) inherently emitted as a result of the di/dt in the filament in response to the substantially instantaneous change in voltage applied across the filament;
• and
• mathematically calculating a maximum value for the predetermined di/dt value according to the equation:
• ##EQU17## where:
• C is a maximum permitted current amplitude;
• N.sub.n is 120 times an integer, n, where n represents the n.sup.th harmonic of the signal;
• .omega. is a value of the frequency at which electrical current is passed through the filament;
• t.sub.2 -t.sub.1 is a time differential between the time point t.sub.1 when the substantially instantaneous change in voltage is applied across the current change limiting element and the time point t.sub.2 when the di/dt reaches a maximum magnitude;
• and
• I.sub.p is a value of a peak current level of the electrical current passing through the filament, established by the maximum value of the voltage of the AC power source and a resistance of the filament.

In an incandescent lamp bulb having a light-generative filament for generating light when the lamp bulb is powered with electrical energy generated at an electrical power source and a longitudinally-extending lamp exhaust tube, a combination with the light-generative filament of a current change limiting element positionable in electrical connection with the light-generative filament for limiting rates of current level change of electrical energy applied to the light-generative filament, said current change limiting element comprising:

• a core of ferromagnetic material having a central aperture extending therethrough to permit positioning of the core of ferromagnetic material about the lamp exhaust tube, the central aperture defining a top opening at a top surface of the core of ferromagnetic material and a bottom opening at a bottom surface of the core of ferromagnetic material;
• a winding wrapped about the core of ferromagnetic material;
• and
• a magnetic flux path positioned about at least a portion of the winding between the top surface of the core and the bottom surface of the core wherein the core of ferromagnetic material, the winding, and the magnetic flux path together define part of an inductor assembly of a selected inductance.