The Study Of Dimmable Electronic Ballast For Ultraviolet Lamps

As the development of "Green Lighting Project", gas discharge lamps are preferred to their counterparts, incandescent lamps, due to its energy saving and high lighting efficiency, although they require their own match ballast equipments.Solid-state high-frequency electronic ballasts for fluorescent lamps offer considerable advantages if compared with the electromagnetic ballasts commonly in use, such as some higher lumen output, lower starting voltage, no audible noise and flicker level.The power factor correction (PFC) and half-bridge inverter circuit topology are commonly used in modern high power factor electronic ballasts. However, as the development of power integrated circuit (PIC), many integrated circuit chips are produced in order to get rid of the disadvantages of pulse transformer and simplify the design.Ultraviolet lamps are a type of low pressure mercury vapor discharge lamps, which belong to special type fluorescent lamps and are widely applied in sewage disposal and water purification. It has the same principle of the common fluorescent lamps. And electronic ballast for the fluorescent lamp has been developed for a long time and obtained many mature technology achievements. The task is introduced electronic ballast for fluorescent lamps into ultraviolet lamps, instead of the traditional power supply which consists of electromagnetic ballast.The proposed electronic ballast is the cascade operation of electro magnetic interference (EMI) filter, AC/DC rectifier, PFC, half-bridge inverter and dimmable control circuit. In order to shape the input line current and to reduce the harmonic currents, the active power factor correction circuitry (APFC), consists of APFC controller TDA4863, is required in front of the electronic ballast. The dimming feature is carried out by the variation of the switching frequency, and the driver circuit is made with self-oscillating half-bridge driver UBA2014.A circuitry prototype based on the proposed electronic ballast is built in the laboratory. And the experimental measurements show that it has the feature of continuous line current, adequate power factor correction and reasonable total harmonic distortion (THD).