Method and apparatus for driving CCFL at low burst duty cycle rates
First Claim
1. A cold cathode fluorescent lamp controller comprising:
- a pulse generator exhibiting a cycle period;
a burst dimming control input lead coupled to said pulse generator, said pulse generator responsive to a signal received on said burst dimming control input lead to set a burst dimming duty cycle;
a comparator, arranged to;
receive a signal indicative of a value of current through a load driven by said pulse generator, andcompare said received signal to a reference signal;
an error detection circuit operative to shut down said pulse generator responsive to an output of said comparator indicating that said received signal is less than said reference signal for a predetermined number of cycles of said pulse generator; and
a disable circuit arranged to prevent, when said set burst dimming duty cycle is less than a predetermined value, said shut down of said pulse generator responsive to said output of said comparator indicating said received signal is less than said reference signal.
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Accused Products
Abstract
A cold cathode fluorescent lamp controller constituted of a pulse generator exhibiting a cycle period; a burst dimming control operative to set a burst dimming duty cycle for the pulse generator; a comparator arranged to receive a signal indicative of the value of current through a load driven by the pulse generator and compare the received signal to a reference signal; an error detection circuit operative to shut down the pulse generator responsive to an output of the comparator indicating that the received signal is less than the reference signal for a predetermined number of cycles of the pulse generator; and a disable circuit arranged to prevent, when the set burst dimming duty cycle is less than a predetermined value, the shut down of the pulse generator responsive to the output of the comparator indicating the received signal is less than the reference signal.
420 Citations
20 Claims
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1. A cold cathode fluorescent lamp controller comprising:
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a pulse generator exhibiting a cycle period; a burst dimming control input lead coupled to said pulse generator, said pulse generator responsive to a signal received on said burst dimming control input lead to set a burst dimming duty cycle; a comparator, arranged to; receive a signal indicative of a value of current through a load driven by said pulse generator, and compare said received signal to a reference signal; an error detection circuit operative to shut down said pulse generator responsive to an output of said comparator indicating that said received signal is less than said reference signal for a predetermined number of cycles of said pulse generator; and a disable circuit arranged to prevent, when said set burst dimming duty cycle is less than a predetermined value, said shut down of said pulse generator responsive to said output of said comparator indicating said received signal is less than said reference signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of preventing shut down due to a ramping burst signal, the method comprising:
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comparing a representation of a current through a load with a reference signal, the current through the load supplied responsive to a power source, and in the event that said current through the load is less than said reference signal for a first predetermined period, at least partially shutting down the power source; detecting that a burst dimming duty cycle for the current through the load is less than a predetermined value; and disabling said at least partially shutting down of the power source, when said burst dimming duty cycle is less than said predetermined value. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
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18. A cold cathode fluorescent lamp controller comprising:
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a pulse generator exhibiting a cycle period; a means for receiving a burst dimming control, said pulse generator responsive to a signal received on said means for receiving a burst dimming control to set a burst dimming duty cycle; a means for comparing arranged to; receive a signal indicative of a value of current through a load driven by said pulse generator, and compare said received signal to a reference signal; a means for detecting error arranged to shut down said pulse generator responsive to an output of said means for comparing indicating that said received signal is less than said reference signal for a predetermined number of cycles of said pulse generator; and a means for disabling said means for comparing arranged to prevent, when said set burst dimming duty cycle is less than a predetermined value, said shut down of said pulse generator responsive to said output of said means for comparing indicating said received signal is less than said reference signal. - View Dependent Claims (19, 20)
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Specification