Matsushita Electric Works R&d Laboratory, Inc.

Matsushita Electric Works, Ltd.

Da Feng Weng

A circuit to start an HID lamp in a high-frequency start mode and, after starting, to operate the lamp in a low-frequency operating mode is controlled, during the high-frequency start mode, to drive the lamps with a voltage that includes a high-frequency component to ignite the lamp and a unipolar or bipolar offset component to keep the lamp ignited during a transition from the high-frequency start mode to the low-frequency operating mode.

Method and apparatus for controlling the operation of a lamp

An electronic ballast circuit includes an input section which rectifies, power factor corrects and filters an AC input voltage to provide a rectified signal. The electronic ballast circuit also includes an inverter section which receives the rectified voltage and switches the rectified voltage to provide an AC signal to a resonant load circuit. The input section includes a resonant tank circuit which provides a high frequency current to the inverter to soft switch the switches within the inverter. In the input section, an inductor is placed on the AC side of a diode bridge rectifier advantageously allowing the removal of several prior art ballast circuit components since placing this portion of the power factor correction (PFC) circuit within the input circuit on the AC side of the diode bridge rectifier allows the bridge rectifier to perform both the rectification and current blocking functions. Advantageously, this reduces the cost of the electronic ballast circuit and increases its reliability since less components are required. In addition, the switching frequency of the switches is controlled to regulate the input current, while the switching duty cycle is independently controlled to regulate the output power.

Electronic ballast circuit

A power factor correction circuit, usable with, for example, a switching power supply of a discharge lamp. The power factor correction circuit includes a shaping system that shapes an input current of a power line during a predetermined period proximate a zero line crossing point of the input current; and a minimizing system that minimizes a pulsating of the input current.

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Winchester, MA, United States of America

Da Feng Weng