Patent ID: 6342782
Filing Date: 2002-01-29
Classification: G09G

Abstract:
A power supply device for driving liquid crystal that generates N numbers of liquid crystal drive voltages between first and second reference voltages, the power supply device comprising:a voltage division circuit that divides a voltage between the first and second reference voltages to generate N pairs of first and second voltages including N numbers of first voltages each of which is equal to or higher than each of the N numbers of liquid crystal drive voltages, and N numbers of second voltages each of which is equal to or lower than each of the N numbers of liquid crystal drive voltages, when the first voltage is not equal to the second voltage in each pair; and N numbers of impedance conversion circuits that generate N numbers of impedance converted liquid crystal drive voltages based on the N pairs of the first and second voltages; wherein each of the N numbers of impedance conversion circuits comprises: a voltage follower type of differential amplification circuit to which a pair of first and second voltages among the N pairs of first and second voltages is input and which generates a first output voltage based on the first input voltage and further generates a second output voltage based on the second input voltage; and an output circuit including a P-type transistor and N-type transistor connected in series between a first power supply line for the first reference voltage and a second power supply line for the second reference voltage, and having an output terminal which is connected between the P-type transistor and N-type transistor and outputs one of the N numbers of liquid crystal drive voltages; and wherein operation of the N-type transistor is controlled by the first output voltage from the differential amplification circuit, and operation of the P-type transistor is controlled by the second output voltage from the differential amplification circuit.