The Research Of Low-Voltage DC Supply Digital Electronic Ballasts For HID Lamps

High intensity discharge (HID) lamp is notable for its high luminous efficacy, long life and energy saving. It is considered as the very ideal light source. With the development of renewable energy source and the actualization of the Green Lighting Project, the research of low-voltage DC supply digital electronic ballast for HID lamp has become more and more important because of its benefits such as environmental protection and energy-saving. Digital electronic ballast based on microprocessor, which has more simple structure and can realize more complex and intelligent control strategy, represents the developing orientation of electronic ballast.In this thesis, categories and electrical characteristics of HID lamps are introduced in brief. The benefits of electronic ballast are analyzed. And the developing status, applying fields as well as developing directions of low-voltage DC supply electronic ballast are given.Related know-how of low-voltage DC supply electronic ballast is summarized. A double power-stage circuit consisted of a DC/DC converter and a half-bridge inverter with LCC resonant circuit is selected as the main circuit of the ballast. The design of high efficiency and high power density are studied deeply. The benefits and working principles of the push-pull converter, which has maximum effect on the efficiency and power density of the system, are analyzed. The effective eliminating method to the magnetic bias of push-pull transformer is proposed, and the parameter design method of the push-pull circuit is given. Control circuit is composed of MCU control system and driving circuits. Different LCC parameters and driving circuits for half-bridge inverter are designed for low power HPS lamp and MH lamps based on their different characteristics.System control circuit is designed based on 8-bit Freescale MCU. The control circuit is simplified and the performance of the electronic ballast is improved greatly. Different control strategies are applied to different lamp operating stages based on the characteristic of HID lamp. Control program can match to different HID lamps. Aiming to the question of the open-loop control of the push-pull converter, a method that can regulate the average input power of the inverter based on the DC bus voltage is proposed in this thesis.Based on the former theoretical analysis and design, prototypes of 24V DC supply digital electronic ballasts for 100W HPS lamp and 70W MH lamp are presented. All experimental results prove that the designed prototypes can satisfy the design requirements.