Device and method for light-modulating control of fluorescent lamp

Abstract

A circuit structure and control method for controlling the light modulation of fluorescent lamp is disclosed. Said fluorescent lamp is driven by a semi-bridge resonant inverter type ballast working in constant frequency and constant duty ratio. Changing the DC input voltage of said ballast can modulate the light. Its variable DC power supply is taken from AC-DC converter for AC input power supply or DC-DC converter for DC input power supply.

Description

technical field [0001] The invention relates to the related problems of the dimming control method and equipment of the electronic ballast for fluorescent lamps, and particularly relates to the advantages of low electromagnetic interference and low switch stress brought by the equipment and the control method. Background technique [0002] As an energy-saving measure for residential, commercial and industrial lighting, high-frequency electronic ballasts for fluorescent lamps are gradually being widely used. Electronic ballasts have many advantages such as: increased efficiency, higher output luminosity and longer life of fluorescent lamps. Electronic ballasts are switch-mode power circuits, generally using series resonant power converters. [0003] figure 1 The basic principle of the traditional electronic ballast is drawn. At a higher frequency (usually 25kHz ~ 50kHz), the resonant capacitor C r The voltage on will turn the lamp on. Due to the high frequency of the driv...

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Problems solved by technology

[0015] 1. Frequency conversion control is more complicated and expensive than constant frequency control;

[0016] 2. If the inverter is not operated with soft switching, the switching loss of the inverter will increase, thereby reducing the system efficiency;

[0017] 3. In order to adjust the lamp to low power output, the switching frequency range may be very large (for example: 25kHz ~ 65kHz), but in fact the frequency range of the magnetic core, the gate drive circuit and the electronic control circuit will limit the dimming frequency range;

[0018] 4. It is difficult to realize soft switching in the whole frequency modulation range

[0019] 5. If the switching frequency range is small, the power adjustment range is small

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