Circuit arrangement

A circuit for supplying a DC voltage to a load that includes a discharge lamp from an AC supply voltage source and at a high power factor, comprising:

• input terminals for connection to an AC supply voltage source;
• rectifying means coupled to the input terminals for rectifying an AC voltage supplied by the AC supply voltage source;
• output terminals for connection to the load that includes a discharge lamp;
• a DC-DC boost converter connected between the rectifying means and the output terminals and provided with a first inductive means, a first unidirectional element and a switching element;
• a series arrangement of an impedance and a first capacitive means connected across the output terminals, the impedance being shunted at least in part by a further unidirectional element, and
• means for controlling the operation of the switching element such that the current taken up from the AC supply voltage source is approximately sinusoidal in shape and approximately in phase with the AC voltage.

A circuit for supplying a DC voltage to a load that includes a discharge lamp from an AC supply voltage source and at a high power factor, comprising:

• input terminals for connection to an AC supply voltage source;
• rectifying means coupled to the input terminals for full-wave rectifying an AC voltage supplied by the AC supply voltage source, the AC voltage supplied by the AC supply voltage source having a maximum amplitude;
• output terminals for connection to a load that includes a discharge lamp;
• a series arrangement of an impedance and a first capacitive means connected across the output terminals, the impedance being shunted at least in part by a unidirectional element, the first capacitive means receiving charging current from said rectifying means;
• and
• a DC-DC boost converter connected between the rectifying means and the output terminals for receiving the full-wave rectified AC voltage and converting the full-wave rectified AC voltage to a substantially constant DC voltage across said first capacitive means with an approximately sinusoidal voltage superimposed thereon, the substantially constant DC voltage across the first capacitive means being higher during stationary lamp operation than the maximum amplitude of the AC voltage supplied by the AC supply voltage source,
• said impedance acting to limit inrush of charging current to said first capacitive means upon turn-on of said circuit and being effectively bypassed by said first unidirectional element during stationary lamp operation to minimize power dissipation from said impedance during stationary lamp operation,
• whereby the current taken up from the AC supply voltage source is approximately sinusoidal in shape and approximately in phase with the AC voltage.