High-efficiency adaptive DC/AC converter
Assignee02 Micro International Limited
InventorYung-Lin Lin
Life of this patent
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Abstract
A CCFL power converter circuit is provided using a high-efficiency zero-voltage-switching technique that eliminates switching losses associated with the power MOSFETs. An optimal sweeping-frequency technique is used in the CCFL ignition by accounting for the parasitic capacitance in the resonant tank circuit. Additionally, the circuit is self-learning and is adapted to determine the optimum operating frequency for the circuit with a given load. An over-voltage protection circuit can also be provided to ensure that the circuit components are protected in the case of open-lamp condition.
Claims30
A DC to AC cold cathode fluorescent lamp inverter circuit comprising:
- a plurality of switches for selective coupling to a voltage line;
- a transformer having a primary side and a secondary side, said primary side for selective coupling to said voltage line in an alternating fashion through said switches;
- a feedback signal line receiving a feedback signal indicative of an electrical condition at a cold cathode fluorescent lamp load;
- and
- a feedback control circuit coupled to said feedback signal line and said switches for adjusting the power delivered to said load only if said electrical condition is outside a predetermined range.
A DC to AC cold cathode fluorescent lamp inverter controller integrated circuit comprising:
- a plurality of outputs for controlling a plurality of switches to selectively couple said switches to a voltage line;
- a feedback signal input receiving a feedback signal indicative of an electrical condition at a cold cathode fluorescent lamp load;
- and
- a feedback control circuit coupled to said feedback signal input and said outputs for adjusting the power delivered to said load only if said electrical condition is outside a predetermined range.
A liquid crystal display unit comprising:
- a liquid crystal screen;
- a cold cathode fluorescent lamp for illuminating said liquid crystal screen;
- a plurality of switches for selective coupling to a voltage line;
- a transformer having a primary side and a secondary side, said primary side for selective coupling to said voltage line in an alternating fashion through said switches and said secondary side coupled to said cold cathode fluorescent lamp;
- a feedback signal line receiving a feedback signal indicative of an electrical condition at said cold cathode fluorescent lamp;
- and
- a feedback control circuit coupled to said feedback signal line and said switches for adjusting the power delivered to said cold cathode fluorescent lamp only if said electrical condition is outside a predetermined range.
A method for controlling a DC to AC cold cathode fluorescent lamp inverter circuit comprising:
- providing a first pulse signal to a first transistor;
- selectively coupling said first transistor to a voltage;
- providing a second pulse signal to a second transistor;
- selectively coupling said second transistor to said voltage;
- receiving a feedback signal indicative of an electrical condition at a cold cathode fluorescent lamp load;
- and
- adjusting the power delivered to said load only if said electrical condition is outside a predetermined range.
Dependencies are inferred from the claim text.