Control device for low-pressure fluorescent lamp
AssigneeSGS-Thomson Microelectronics S.A.
InventorMarco Bildgen
Life of this patent
Estimating the term…
Abstract
To control low-pressure fluorescent lamps, there is provided a device comprising a first change-over switch circuit and a second change-over switch circuit, respectively including a first power transistor and a second power transistor. The first change-over switch circuit first of all measures the period of time when the second power transistor is on. Then, secondly, it turns the first power transistor on for a period equal to the period measured.
Claims42
A control device for a low-pressure fluorescent lamp comprising a first change-over switch circuit and a second change-over switch circuit series-connected between a high voltage and the ground, a first change-over switch circuit comprising a first power transistor, the second change-over switch circuit comprising a second power transistor, an inductor being series-connected with the low-pressure fluorescent lamp and with a capacitor between the midpoint of the two change-over switch circuits and the ground,
- wherein the first change-over switch circuit comprises:
- a circuit for measuring the period during which the second power transistor is on to measure a first period;
- and
- a switching-on circuit to turn the first power transistor on during a second period that is consecutive and equal to the first period.
A control device for a fluorescent lamp comprising:
- a first change-over switch circuit;
- a second change-over switch circuit;
- a high-voltage supply;
- said first and second change-over switches being connected in series across said high-voltage supply;
- said first change-over switch circuit comprising a first power transistor;
- said second change-over switch circuit comprising a second power transistor;
- a fluorescent drive circuit intercoupling the fluorescent lamp and the connection points of the first and second change-over switch circuits;
- said first change-over switch circuit comprising:
- a circuit for measuring a period during which the second power transistor is on for a first period, and
- a switch-on circuit to turn on the first power transistor during a second period that is consecutive and substantially equal to the first period.
A control device for a fluorescent lamp comprising:
- a first change-over switch means;
- a second change-over switch means;
- means interconnecting said first and second change-over switch means in series at a connection point and across said high-voltage supply;
- each said change-over switch means comprising a power transistor;
- means for intercoupling the connection point of the switch means to said fluorescent lamp;
- said first change-over switch means each comprising:
- a circuit means for measuring a period during which the second power transistor is on for a first period, and
- a switch-on circuit means to turn on the first power transistor during a second period that is consecutive and substantially equal to the first period.
A method of controlling the operation of a fluorescent lamp comprisingthe steps of:
- providing first and second change-over switch circuits each having respective first and second power transistors;
- coupling said change-over switch circuits to said fluorescent lamp;
- said first change-over switch circuit performing steps of:
- measuring a period during which the second power transistor is on to define a first period, and
- turning the first power transistor on during a second period that is consecutive and substantially equal to the first period.
Dependencies are inferred from the claim text.