Circuit arrangement with improved power-factor for feeding a discharge lamp

A circuit arrangement for feeding a discharge lamp, comprising

• input terminals to be connected to a pourer supply source supplying a low-frequency alternating voltage,
• rectifier means coupled to the input terminals for rectifying the low-frequency alternating voltage, and provided with a first output terminal and a second output terminal,
• a first branch comprising a series arrargement of a first buffer capacitance and a second buffer capacitance, and which interconnects said output terminals,
• a load branch comprising a series arrangement of a first inductive element and lamp clamps for electrically contacting a discharge lamp, and having a first end coupled to a common point of the two buffer capacitances,
• a first switching element coupled to the load branch,
• a second switching element coupled to the load branch,
• a control circuit coupled to a control electrode of the first switching element and to a control electrode of the second switching element for rendering the first switching element alternately conducting and non-conducting, while the second switching element is non-conducting, and for rendering the second switching element alternately conducting and non-conducting, while the first switching element is non-conducting,
• a first unidirectional element and a second unidirectional element coupled to the load branch,
• a third unidirectional element coupled between the first output terminal and the first buffer capacitance,
• a fourth unidirectional element coupled between the second output terminal and the second buffer capacitance,
• a second inductive element having a first end coupled to a first end of the first inductive element,
• a first capacitive element coupled between a first tapping point of the first inductive element and the second output terminal,
• a second capacitive element coupled between a tapping point of the second inductive element and the first output terminal, and wherein the first switching element is coupled between a second end of the first inductive element and a common point of the third unidirectional element and the first buffer capacitance, wherein the second switching element is coupled between a second end of the second inductive element and a common point of the fourth unidirectional element and the second buffer Capacitance, and wherein the first unidirectional element is coupled between the second end of the first inductive element and a common point of the fourth unidirectional element and the second buffer capacitance, and the second unidirectional element is coupled between the second end of the second inductive element and a common point of the third unidirectional element and the first buffer capacitance.