Lamp ballast circuit

Claim 2

A circuit arrangement comprising a DC-AC converter for igniting and supplying a lamp, which DC-AC converter is provided with input terminals suitable for being connected to the poles of a DC voltage source, a branch A comprising at least one switching element, a control branch of which one end is connected to a control electrode of the switching element and another end to a first main electrode of the switching element, which control branch comprises inductive means L3, a load branch E comprising inductive means L1 and a load circuit comprising two branches B and C, in which branch B comprises inductive means L2 and branch C comprises capacitive means, one end of branch A being connected to an end of branch E, and another end of branch A being connected to an input terminal, while a further end of branch E is connected to the other input terminal, characterized in that the control branch is shunted by a branch D which comprises capacitive means.

Claim 3

A circuit arrangement as claimed in claim 1 comprising a control transformer which has a primary and a secondary winding, the primary winding being coupled to the load branch E and the secondary winding forming part of the inductive means L3, characterized in that a resonance frequency f1 of a resonant circuit comprising the control branch and the branch D shunting the control branch is higher than a frequency f2, for which a voltage across the load branch E coupled to the lamp is in phase with a current through the load branch E.

Claim 4

A circuit arrangement as claimed in claim 1, characterized in that the circuit arrangement is provided with means for generating a DC voltage, which means are connected to the input terminals, and with further means for adjusting said DC voltage.

Claim 5

A circuit arrangement as claimed in claim 2, characterized in that the circuit arrangement is provided with means for generating a DC voltage, which means are connected to the input terminals, and with further means for adjusting said DC vlotage.

Claim 6

A circuit arrangment comprising a DC/AC converter for igniting and suppling a lamp, said DC/AC converter being provided with two input terminals suitable for being connected to a DC voltage source, a branch circuit A comprising two switching elements each with a control electrode and a first and second main electrode, said first main electrode of one of said switching elements being connected to the second main electrode of the other switching element to form a junction therewith, said branch circuit A also including a separate control branch associated with each switching element, one end of each control branch being connected to the control electrode of its associated switching element and another end of each control branch being connected to the first main electrode of its associated switching element, each control branch comprising inductive means, said circuit arrangement also including a load branch E comprising inductive means and a load circuit comprising two branches B and C, in which branch B comprises inductive means L2 and branch C comprises capacitive means, said junction of branch A being connected to an end of branch E, and an end of branch A being connected to an input terminal, while a further end of branch E is connected to the other input terminal and also to another end of branch A and wherein each control branch is shunted by a branch (D1 or D2) which comprises capacitive means.

Claim 7

A circuit arrangment comprising a DC/AC converter for igniting and suppling a lamp, said DC/AC converter being provided with two input terminals suitable for being connected to a DC voltage source, a branch circuit A comprising two switching elements each with a control electrode and a first and second main electrode, said first main electrode of one of said switching elements being connected to the second main electrode of the other switching element to form a junction therewith, said branch circuit A also including a separate control branch associated with each switching element, one end of each control branch being connected to the control electrode of its associated switching element and another end of each control branch being connected to the first main electrode of its associated switching element, each control branch comprising inductive means, said circuit arrangement also including a load branch E comprising inductive means and a load circuit comprising two branches B and C, in which branch B comprises inductive means L2 and branch C comprises capacitive means, said junction of branch A being connected to an end of branch E, and an end of branch A being connected to an input terminal, while a further end of branch E is connected to the other input terminal and also to another end of branch A and wherein each control branch is shunted by a branch (D1 or D2) which comprises capacitive means.

Claim 8

A circuit arrangement in accordance with claim 5, wherein said load inductive means L1 is connected directly to said junction of branch A.

Claim 9

A circuit arrangement in accordance with claim 6, wherein a diode is connected between the first and second main electrodes of each switching element.

Claim 10

A circuit arrangement in accordance with claim 7, wherein a pair of zener diodes is connected across each branch D1 and D2.

Claim 11

A circuit arrangement in accordance with claim 7, wherein each control branch (L 3A , L 3B ) is a secondary winding of a transformer, said transformer primary winding (L4) being connected in parallel with said branches B and C of said load circuit.

Claim 12

A circuit arrangement in accordance with claim 9, wherein branch C comprises two interconnected capacitors and said load inductive means L1 is connected between said two capacitors.

Claim 13

A circuit arrangement in accordance with claim 10, wherein an additional capacitor is connected in parallel with one of said interconnected capacitors and said inductive means of branch B.

Claim 14

A circuit arrangement in accordance with claim 9, wherein said branch B comprises inductive means with two interconnected sections and said load inductive means L1 is connected between said two sections through a capacitor.

Claim 15

A circuit arrangement in accordance with claim 9, wherein a starter circuit is connected across one of the capacitive means of one of branches D1 or D2.

Claim 16

A circuit arrangement in accordance with claim 5, wherein a resident frequency f1 of each control branch and its associated shunting branch is higher than a frequency f2 for which a voltage across the load branch is in phase with a current through said load branch.

Claim 17

A circuit arrangement in accordance with claim 14, wherein a means for generating a DC voltage is connected across the input terminals and means are included for adjusting the DC voltage whereby the luminous flux of a lamp controlled by the circuit arrangement can be adjusted over a wide range by adjusting said DC voltage.

Claim 18

A circuit arrangement in accorcance with claim 14, wherein said DC/AC converter is so dimensioned that the operating frequency f of the DC/AC converter is smaller than f1 and greater than f2.

Claim 19

A circuit arrangement in accordance with claim 14, wherein a means for generating a DC voltage is connected across the input terminals and means are included for adjusting the DC voltage whereby the amplitude of the high frequency alternating current is changed but the operating frequency f of the DC/AC converter remains substantially unchanged.

Claim 20

A circuit arrangement in acccordance with claim 9, wherein a resistor is connected across said primary winding.