Matsushita Electric Works, Ltd.

Virginia Tech Intellectual Properties, Inc.

Koji Nishiura

Fred C Lee

Minoru Maehara

Yoshinobu Murakami

Hiroyuki Sako

Tokushi Yamauchi

Akinori Hiramatsu

Toshiya Kanja

Nobukazu Miki

Masahiro Yamanaka

Wei Chen

High voltage stress on the semiconductor devices at light load conditions, high total harmonic distortion (THD) of the line current, and poor crest factor (CF) of lamp current of 'charge pump' electronic ballast circuits make them difficult to manufacture cost-effectively. To overcome these deficiencies, the DC bus voltage is reduced at light loads by providing a second resonance. One technique, high-frequency second-stage resonance, provides sufficient preheating at low V.sub.dc. Combined with the instant startup and the proper restart scheme, this technique can greatly reduce the maximum V.sub.dc at ignition. Another technique, low-frequency second-stage resonance, can reduce the steady state V.sub.dc at light loads, including during start-up. Consequently, high ignition voltage can be continuously impressed on the lamp without increasing V.sub.dc. Further, a diode clamping technique smooths the envelope of V.sub.a, thereby achieving near unity power factor, low THD and low CF without close-loop control.

Power supply for supplying AC output power

A power supply device in which an inverter circuit is supplied with power directly from a rectification circuit, the inverter circuit has a pair of switching elements connected in series with each other and connected between both ends of the rectification circuit through an impedance element, a series circuit of the impedance element, two capacitors and an inductor is connected in parallel to one of the switching elements of the inverter circuit connected to positive polarity one of the both ends of the rectification circuit, a load is connected across one of the capacitor, a valley filling circuit receives an output of the inverter circuit through a diode provided in the valley filling circuit and supplies it to a power supply capacitor provided therein and, when a DC output voltage of the rectification circuit drops, the valley filling circuit supplies power to the inverter circuit via the power supply capacitor and another diode provided therein. Thereby, fluctuations in a current supplied to the load can be effectively reduced.

Power supply device

A inverter AC power supply comprises a chopper connected to receive an AC voltage from a low frequency AC voltage source to provide a smoothed DC voltage, and an inverter providing a high frequency AC voltage from the smoothed DC voltage for driving a load. The chopper includes an inductor and a series connected pair of first and second switching elements which alternately turn on and off for periodically interrupting an input AC voltage to store a resulting energy to the inductor which is subsequently released to charge a smoothing capacitor to give a smoothed DC voltage there across. The inverter shares the first and second switching elements with the chopper and comprises a L-C resonant circuit which is connected across one of the first and second switching elements together with the load to provide an oscillating voltage as the high frequency AC voltage to the load. A self-excitation control circuit is included in the inverter to acknowledge a change in the oscillating voltage. The self-excitation control circuit is connected to control terminals of the first and second switching elements in order to alternately turn on and off the first and second switching elements in response to the change in the oscillating voltage.

Inverter AC power supply

Growing community of inventors

Osaka, Japan

Koji Nishiura