Sharp Kabushiki Kaisha Corporation

Daniel Oliveira

Haruo Nishiyama

Hiranaga Yamamoto

Yoshifumi Maitani

David Isner

When the phase control is effected on a supply voltage to a load having positive resistance characteristics with respect to temperatures before a current is allowed to pass, a voltage is supplied for a current passing time T1, and the voltage is supplied for a current passing time T2 longer than the current passing time T1, and the voltage is supplied for a current passing time T3 shorter than the current passing time T2. Also, a second control pattern is effected at least once, in which the current is passed while the current passing time is kept substantially constant, then the current passing time is extended before the attenuation rate of the peak value of the resulting load current saturates, and then the current is passed while the extended current passing time is kept substantially constant. Consequently, a voltage drop can be reduced effectively without causing large distortion of the current waveform or large conduction noise by omitting an expensive noise filter or special hardware.

Power control unit having switching phase control for reducing voltage

In a power control unit for controlling a power supply to a load connected to an AC power source by switching on half cycles, following three modes are carried out in the order of presented: a first control mode for continuously supplying a power which is composed of a plurality of half cycle switching waveforms of a first polarity to said load; a second control mode for continuously supplying a power which is composed of a plurality of half cycle switching waveforms of a second polarity to said load, said second polarity being different from said first polarity; and a third control mode for supplying a power of a half cycle of said first polarity and a power of a half cycle of said second polarity to said load in turn. This arrangement can attain an effect that both the harmonic noises and the flickers caused by a rush current are reduced.

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Soultz, France

Daniel Oliveira