US Patent 7193368 Parallel lamps with instant program start electronic ballast

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.