US 6,747,423 B2 · Circuit configuration to operate a gas discharge lamp

Abstract

In a circuit configuration to operate a gas discharge lamp (LA) the lamp (LA) is arranged in a full bridge circuit. A control circuit in normal operation actuates the four switches (S1-S4) in such a way that it changes over with a first frequency (f1) alternately between a first and a second state (T1, T2), whereby in the first state (T1) the two switches (S2, S3) of a first bridge diagonal are opened, one switch (S1) of the second bridge diagonal is closed and the other switch (S4) with a second frequency (f2), which is higher than the first frequency (f1), is alternately opened and closed. In the second state (T2) the four switches (S1-S4) are actuated in such a way that the lamp (LA) is pole reversed. In a start phase (TS) on the contrary the switch connected to the DC voltage source (S4) of a half-bridge is opened, the second switch (S3) of this half-bridge is closed, and the two switches (S1, S2) of the other half-bridge are with a third frequency (f3) alternately opened and closed. As a result reliable lamp starting is rendered possible and at the same time the generation of high-frequent alternating fields in normal operation is reduced.

Claims13

Dependent claims

A circuit for operating a gas discharge lamp from a DC voltage supply, said circuit comprising:

first, second, third and fourth controllable switches, said first and second switches being arranged in series with each other between DC voltage supply terminals, and said second and fourth switches being arranged in series with each other between said DC voltage supply terminals;
a first nodal point between said first and second switches and a second nodal point between said nodal point between said third and fourth switches being connectable to opposite terminals of a gas discharge lamp;
a control circuit connected to open and close said switches according to a first state, a second state and a start state, wherein
said first state and said second state occur alternately to each other at first frequency, and wherein
in said first state, said second and third switches remain open and said first switch remains closed while said fourth switch opens and closes at a second frequency which is higher than said first frequency,
in said second state, said first and fourth switches remain open and said third switch remains closed while said second switch opens and closes at said second frequency, and
in said start state, said fourth switch remains closed, said third switch remains open and said first and second switches open and close alternately at a third frequency.

4 more elements

Dependencies are inferred from the claim text.

Circuit configuration to operate a gas discharge lamp

Life of this patent

Circuit configuration to operate a gas discharge lamp

Life of this patent

Abstract

Claims13