Patent ID: 6239558
Filing Date: 2001-05-29
Classification: C02F,H01L,H05B,Y10S

Abstract:
A piezoelectric transformer control circuit for driving a cold-cathode fluorescent lamp connected to a piezoelectric transformer, the control circuit comprising:oscillation means for generating an oscillation signal in accordance with a control voltage;driving means for driving said piezoelectric transformer by an AC voltage generated in accordance with the oscillation signal from said oscillation means;load current detecting means for detecting a current flowing in the cold-cathode fluorescent lamp connected to an output terminal of said piezoelectric transformer;sample-and-hold means for sampling and holding the output from said load current detecting means in accordance with a predetermined control signal;load current error output means for comparing an output from said sample-and-hold means with a predetermined value and outputting the control voltage in accordance with a result of the comparison; andintermittent oscillating means for intermittently driving said driving means by pulse-modulating a pulse signal, for intermittently driving said piezoelectric transformer, to be supplied to said driving means,wherein said sample-and-hold means outputs, to said load current error output means, a held voltage corresponding to the output from said load current detecting means during oscillation period of said intermittent oscillating means when said intermittent oscillating means does not oscillate, andsaid intermittent oscillating means can adjust a duty ratio of the pulse signal to be generated.