The discharge lamps, used in the Golive and Golux series of gobo projectors, need auxiliary electronics, to supply the correct ignition voltages and to regulate the electrical flow inside the bulb during operation, consisting of ballast and ignitor.
The igniter initially starts the electric arc, supplying a high voltage pulse (1-5 kV peak) and the ballast acts as a current regulator / limiter within the circuit, when the lamp is in steady state.
The ballast is necessary in all those devices that have a negative resistance differential with respect to the power supply, such as discharge lamps. In such devices, the electrical resistance of the lamp decreases as the flow of current passing through it increases, with the consequence that an even greater current flow is produced in the lamp. If such a device were connected to a constant voltage source of electricity, it would draw an ever-increasing amount of current, eventually destroying itself. The ballast provides a positive differential resistance which stabilizes the current flow within the bulb at an appropriate level.
Ballasts can also be used to reduce the current flow in a normal positive resistance circuit: this is the case with LED lamps. Although LED-based luminaires have a positive resistance differential, they cannot regulate their current consumption when connected to a voltage controlled power source, making it necessary to use ballasts to control flow. of current through the LED.
In the past, in addition to the two electrodes between which the electric arc forms, some lamps contained a third electrode which provided the initial impulse when the lamp was turned on. As already mentioned at the beginning, the initial high voltage impulse can be generated by a special igniter (or starter) which causes the lamp electrodes to heat up to a temperature of about 1000 ° C, creating an overvoltage such as to generate an electric discharge with consequent ionization of the gas, until the complete ignition of the lamp.
In addition to the presence of an igniter, the appliances of the past were equipped with the widespread magnetic ballasts, while in the last decade electronic ones have become more popular and affordable. Magnetic ballasts are simpler and cheaper than electronic ones, but much bulkier and heavier. They also emit a slight hum and have the defect of causing a flicker in the emitted light.
Electronic ballasts use solid-state electronic circuits to transform the operating frequency from the standard residential frequency (50 Hz in Italy) to a frequency of 20,000 Hz or higher, eliminating any flickering of the lamp. Electronic ballasts are more accurate and lighter than magnetic ones. Compared to magnetic ballasts, electronic ones also save energy and maintenance costs, produce up to 40% more lumen / watt, increase lamp life and generate less heat.
Finally, digital ballasts have become popular, which use a microprocessor to control and regulate the HID lamp. The firmware of the digital ballast contains control algorithms to provide the correct initial impulse during the ignition of the lamp and then the necessary electrical flow during the full regime.
Goboservice has chosen to equip the Golive 400, a simple and economical projector, with magnetic ballast. The whole Golux series instead (600 and 1000) uses the most efficient electronic ballasts which, in the face of a higher cost, guarantee lightness and better performance.