High Intensity Discharge (High Intensity Discharge) lam […]
High Intensity Discharge (High Intensity Discharge) lamp has become a highly competitive new light source in the field of lighting due to its high luminous flux, high luminous efficiency, long life and small discharge tube. Due to the defects of large size, noise and strobe, inductive ballasts cannot meet the requirements of green lighting. With the development of power electronic technology and the understanding of high-intensity gas discharge, the development of electronic ballasts based on high-frequency conversion has begun, but HID lamps are prone to acoustic resonance phenomena such as arc flicker and distortion when working at high frequencies. If the light intensity is unstable, the arc may be extinguished in severe cases, or even cause damage to the lamp. In this paper, the principle of gas discharge, microscopic motion and macroscopic properties of plasma are studied, and the characteristic equation of plasma oscillation in high-intensity gas discharge lamp is deduced in detail to reveal the excitation mechanism and determinants of the oscillation phenomenon of plasma.
The external manifestation of plasma oscillation-the acoustic resonance phenomenon of arc, sound wave and electrical characteristics are studied. The conventional acoustic resonance suppression methods are intensively analyzed, and the spectral characteristics and application characteristics of various frequency modulation techniques are emphatically studied. The researched HID lamp electronic ballast adopts a two-stage topology, and the active power factor correction Boost circuit of the input stage and the bridge inverter circuit of the output stage both adopt PWM control technology. The PWM output contains the harmonic component of the amount of fire, and the frequency and amplitude are the same. It is an energy source that generates electromagnetic interference and acoustic resonance. The relationship between input current harmonics and power factor is analyzed. Active power factor correction technology is discussed. According to actual application requirements, an improved design of active power factor correction circuit is proposed. Various variable frequency driving and self-oscillation are studied. Drive technology. According to the conclusion that the generation of acoustic resonance requires a specific frequency and sufficient energy and the electromagnetic interference generated by harmonics, it is proposed to use the spectrum dispersion method to disperse the frequency of the PWM output ripple to a wider range to reduce the total harmonic distortion of the input current. Reduce electromagnetic interference: avoid the formation of a standing wave at the fixed frequency point by the driving signal of the output stage HID lamp, and suppress the generation of acoustic resonance.
The chaotic phenomena, characteristics and control methods in the Boost circuit and plasma are studied. Tishan uses a feedback-free chaos control method-parameter resonance perturbation method, which reduces or even eliminates the excitation parameters by perturbing them with specific frequencies. Chaotic Motion: Simultaneously obtain continuous broadband spectrum. Finally, for the Boost circuit and the output inverter circuit, different resonance parameters are used for chaos control, and real-time online chaotic modulation of the PWM wave is realized. More frequency components are obtained, the frequency of the PWM output harmonics is dispersed to a wider range, and the quasi-peak value of each harmonic frequency is reduced: and the driving frequency is continuously nonlinearly drifted around the center frequency, reducing the harmonic amplitude average value. The chaotic modulation circuit is simple and practical. The test waveforms and data show that: the chaotic modulation technology can effectively reduce the harmonics generated by the PWM circuit, reduce the electromagnetic interference generated by the input stage circuit, and suppress the acoustic resonance phenomenon of the output stage.