Toshiba Lighting & Technology Corporation

Kabushiki Kaisha Toshiba

Hirokazu Ohtake

Takuro Hiramatsu

Mitsuhiko Nishiie

Hiroshi Terasaka

In a power supply unit, if a dimmer rate is changed within a range of k, k, . . . kby a dimmer signal k of a dimmer signal generator, light-emitting diodes are controlled to be lighted by a constant current characteristic in an area where the dimmer rate is small according to a load characteristic corresponding to the dimmer rates k, k, . . . k. As the dimmer rate becomes larger, a tendency of a constant voltage characteristic is gradually strengthened from a constant current characteristic so that the light-emitting diodes are lighted at the larger dimmer rate.

Power supply unit having dimmer function and lighting unit

The present invention provides an improved power factor and lower harmonic distortion in the power supply circuit of a high frequency discharge lamp. An 'extra' circuit path is provided so that the driving power to the lamp will 'see' a load that significantly reduces the harmonic distortion and tends to cause the power factor to approach '1'. In a preferred embodiment of the invention this is accomplished by providing a third capacitor with which the load circuit forms an in-series resonance circuit with the discharge lamp and its associated current-limiting inductance. The new circuit arrangement provides a high frequency current passage not provided in known lighting circuits of this type that raises the power factor and lowers harmonic distortion.

Growing community of inventors

Yokosuka, Japan

Hirokazu Ohtake