The present invention relates to a device for operating a high-pressure discharge lamp, comprising a switched mode power supply circuit (SMPS) for supplying power to the high pressure discharge lamp from a supply voltage, the power supply circuit comprising a half bridge commutating forward (HBCF) circuit including an inductance{character pullout}.sup.(L hbcf?), a capacitor circuit of a first capacitor (C.sub.s1) and a second capacitor (C.sub.s2) in series, the lamp (LA) being connectable between the inductance (L.sub.hbcf) and a point (M) between the first and second capacitor (C.sub.s1,C.sub.s2); wherein overvoltage protection means are connected parallel to the lamp, which switch from an off-state with a high resistance operation to an on-state with a low resistance operation when the voltage difference across the protection means exceeds a breakover voltage (V.sub.bo), the breakover voltage (V.sub.bo) being selected to correspond to a predetermined maximum voltage across the first or the second capacitor (C.sub.s1,C.sub.s2).

The invention relates to a continuous current control circuit module of series string bulbs type (II), which can maintain the normal current and voltage across each of the bulbs when any of series connected bulbs burn out. The string includes a shunt in every bulb assemblies, which has an auxiliary conductive apparatus including an SCR (silicon controlled rectifier), a TRIAC (THYristor), a DIAC (trigger diode), or a Transistor with resistors and is parallel connecting related to the bulb. The shunt will thus provide a secure electrical connection of the light string whenever any bulb is burn out or broken.

In a current fed electronic ballast multiple lamps are operated in a parallel circuit arrangement. The ballast provides pre-heating to the cathodes of the lamps for a period of time before an open circuit voltage is ramped up to the preferred starting voltage of the lamps. An open circuit voltage controller times coordinates the pre-heating and the operating voltage. After the pre-heating phase, current is removed from the cathodes of the lamps so that electricity is not wasted to the cathodes while the lamps are lit. A single switch is used to switch cathode pre-heating on and off, regardless of how many lamps the ballast operates. A decoupling array of diodes allows the single switch to coordinate pre-heating to all the lamps.

An ultra bright, low wattage inductively coupled electrodeless aperture lamp is powered by a solid state RF source in the range of several tens to several hundreds of watts at various frequencies in the range of 400 to 900 MHz. Numerous novel lamp circuits and components are disclosed including a wedding ring shaped coil having one axial and one radial lead, a high accuracy capacitor stack, a high thermal conductivity aperture cup and various other aperture bulb configurations, a coaxial capacitor arrangement, and an integrated coil and capacitor assembly. Numerous novel RF circuits are also disclosed including a high power oscillator circuit with reduced complexity resonant pole configuration, parallel RF power FET transistors with soft gate switching, a continuously variable frequency tuning circuit, a six port directional coupler, an impedance switching RF source, and an RF source with controlled frequency-load characteristics. Numerous novel RF control methods are disclosed including controlled adjustment of the operating frequency to find a resonant frequency and reduce reflected RF power, controlled switching of an impedance switched lamp system, active power control and active gate bias control.

The embodiment disclosed herein relates to systems and methods to provide improvements to power delivery systems employed with lamps in general and fluorescent lamps in particular. In accordance with one exemplary embodiment, cathode current is controlled to a maximum level to quickly bring the cathode temperature up to thermionic emission temperature. After lamp ignition, a cathode voltage reduction circuit is employed to reduce voltage of the external cathode heating. Power is supplied to a power factor correction circuit via an IC, in accordance with a second exemplary embodiment. Finally, a third disclosed embodiment addresses desensitizing the lamp from various deleterious parasitic capacitive effects associated with the power delivery to one or more lamps.