Patent ID: 6515522
Filing Date: 2003-02-04
Classification: G09G

Abstract:
A drive circuit of capacitive load comprising:a step-up circuit in which a coil and a transistor are connected in series between a terminal at a first potential and a terminal at second potential lower than said first potential; a diode and a condenser are connected in series between a point of connecting said coil and said transistor and said terminal at said second potential; and a surge pulse generated at said coil by switching on and off said transistor by a coil drive signal, is applied to said condenser via said diode to thereby charge said condenser by which output voltage is generated at a point of connecting said diode and said condenser; a high voltage switch output circuit for selectively driving a plurality of capacitive loads by selectively supplying said output voltage from said step-up circuit as driving voltage with constant current to said capacitive loads under control of selecting circuit; and a coil drive signal generating circuit for generating said coil drive signal at a frequency in correspondence with a single one of said capacitive loads driven or a combination of said capacitive loads simultaneously driven by said high voltage switch output circuit, wherein said coil drive signal generating circuit comprises said selecting circuit and a plurality of oscillators, said plurality of oscillators are set to generate an oscillation output at a predetermined frequency in correspondence with either one of said plurality of capacitive loads and a combination of said capacitive loads, said selecting circuit selects said capacitive load to be driven and selects said oscillators for generating a frequency in correspondence with said selected capacitive load or said combination of said capacitive loads simultaneously selected, and said coil drive signal is generated based on said oscillation output from said selected oscillator.