Collective dimming of discharge lamps with improved input power factor using MERS-PFC converter

Discharge lamps which include HID lamps (High intensity discharge lamps) and fluorescent lamps take up more than 90% of the lighting market. Traditional thyristor voltage control is difficult for discharge lamps dimming due to their negative impedance characteristics. Especially, it is common to operate the HID lamps in 100% lighting state even unnecessary. Simple dimming control is desired to meet users´ requirements and achieve energy saving as well. This paper proposes a collective dimming method for discharge lamps based on a principle of frequency control. The energy saving effect have been proved by experimental results. Then, a new configuration for the frequency converter is proposed with a power factor correction circuit which is named MERS-PFC (Magnetic Energy Recovery Switch-Power Factor Correction) converter. This method has the following advantages: 1) collective control for paralleled lamp groups by one power device; 2) simple control mechanism and easy to realize; 3) soft-switching current continuous mode power factor correction being realized by MERS-PFC converter.