Circuit for retro-lighting a display
AssigneeST-Ericsson SA
InventorsDaniel Ladret, Nawel Bouredji
Life of this patent
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Abstract
There is described a circuit for retro-lighting a display, comprising a group of white light-emitting diodes connected in series between a first node and a second node and a circuit for driving said group of series-coupled light-emitting diodes comprising: a power supply providing a positive voltage supplied to the first node; and a charge pump converter providing a negative voltage obtained from the positive voltage, said negative voltage being supplied to the second node.
Claims7
A circuit for retro-lighting a display, comprising a group of white light-emitting diodes connected in series between a first node and a second node and a circuit for driving said group of series-coupled light-emitting diodes comprising:
- a power supply providing a positive voltage supplied to the first node;
- and
- a charge pump converter providing a negative voltage obtained from the positive voltage, said negative voltage being supplied to the second node,
- wherein the charge pump converter comprises:
- a charge pump capacitor having a first terminal coupled to the first node through a first resistor and a second terminal coupled to the second node and to a ground terminal through a free-wheel diode having an anode and a cathode, said anode being coupled to the second node and said cathode being coupled to the ground terminal;
- and
- a switching element connected between the first terminal of the charge pump capacitor and the ground terminal, and controlled to regulate the voltage across the charge pump capacitor based on the desired value for the negative voltage.
Dependencies are inferred from the claim text.