US 2002/0000850 A1 · Drive circuit of capacitive load and integrated circuit for driving capacitive load

Abstract

A drive circuit capable of adjusting a capacitive load operation, for example, respective brightness of an electroluminescence (EL) element. The drive circuit is a constant current drive system and causes a plurality of capacitive loads, for example, EL elements, to emit light. This is done by setting a coil drive signal applied to the gate of a transistor Tr1. The transistor generates a surge pulse by intermittently connecting a direct current power source to a coil L1 of a step-up circuit 1. The coil drive signal is set to a frequency in accordance with an EL element as a capacitive load driven alone or a combination of EL elements simultaneously driven. Power generated by the step-up circuit 1 can be selected, brightness of a driven EL element E1 or E2 can individually be set or brightness of the EL elements E1 and E2 simultaneously driven can be set.

Claims7

Dependent claims

A drive circuit of a 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 a second potential lower than the first potential;
a diode and a condenser are connected in series between a point connecting the coil and the transistor and the terminal at the second potential;
a surge pulse is generated at the coil by switching on and off the transistor in accordance with a coil drive signal;
and said surge pulse is applied to the condenser via the diode to charge the condenser and generate an output voltage at a connecting point between the diode and the condenser;
a high voltage switch output circuit for selectively driving a plurality of capacitive loads by constant current by receiving the output voltage from the step-up circuit;
and
a coil drive signal generating circuit for generating the coil drive signal at a frequency in correspondence with a single one of the capacitive loads driven or a combination of the capacitive loads simultaneously driven by the high voltage switch output circuit.

4 more elements

An integrated circuit for driving a capacitive load comprising:

a step-up circuit in which by externally attaching a plurality of capacitive loads, a coil and a transistor that are connected in series between a terminal at a first potential and a terminal at a second potential lower than the first potential;
a diode and a condenser that are connected in series between a point connecting the coil and the transistor and the terminal at the second potential;
a surge pulse is generated at the coil by switching on and off the transistor in accordance with a coil drive signal;
and said surge pulse is applied to the condenser via the diode to charge the condenser and generate an output voltage at a connecting point between the diode and the condenser;
a high voltage switch output circuit for selectively driving the plurality of capacitive loads by constant current by receiving the output voltage from the step-up circuit;
and
a coil drive signal generating circuit for generating the coil drive signal at a frequency in correspondence with the capacitive loads driven or a combination of the capacitive loads simultaneously driven by the high voltage switch output circuit.

4 more elements

Dependencies are inferred from the claim text.

Drive circuit of capacitive load and integrated circuit for driving capacitive load

Life of this patent

Drive circuit of capacitive load and integrated circuit for driving capacitive load

Life of this patent

Abstract

Claims7