Power supply circuit for driving liquid crystal display
First Claim
1. A power supply circuit that generates a plurality of drive voltages having intermediate voltage levels with respect to a peak voltage level, the intermediate voltage levels being grouped into a first group of voltage levels comprising intermediate voltage levels that are low level with respect to the peak voltage level and a second group of voltage levels comprising intermediate voltage levels that are high level with respect to the peak voltage level, said power supply circuit comprising:
- an amplifier having a voltage follower configuration;
at least one capacitor connected to the amplifier, said at least one capacitor and said amplifier generating a first voltage level included in the first group of voltage levels; and
a switch circuit controlled at a predetermined timing to switch said at least one capacitor to generate a second voltage level included in the second group of voltage levels with a discharge voltage of said at least one capacitor and the peak voltage level.
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Accused Products
Abstract
A drive power supply circuit for driving liquid crystal display of the present invention generates necessary levels in an LCD drive power supply circuit that generates drive levels for LCDs in an LCD controller/driver IC by means of switching connection to capacitors in a constant manner or in synchronism with the timing of LCD driving. It allows reduction in number of the components such as amplifiers for level generation and external capacitors, which in turn reduces current consumption of the entire system, chip areas, and mounting areas.
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Citations
16 Claims
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1. A power supply circuit that generates a plurality of drive voltages having intermediate voltage levels with respect to a peak voltage level, the intermediate voltage levels being grouped into a first group of voltage levels comprising intermediate voltage levels that are low level with respect to the peak voltage level and a second group of voltage levels comprising intermediate voltage levels that are high level with respect to the peak voltage level, said power supply circuit comprising:
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an amplifier having a voltage follower configuration; at least one capacitor connected to the amplifier, said at least one capacitor and said amplifier generating a first voltage level included in the first group of voltage levels; and a switch circuit controlled at a predetermined timing to switch said at least one capacitor to generate a second voltage level included in the second group of voltage levels with a discharge voltage of said at least one capacitor and the peak voltage level. - View Dependent Claims (2, 3, 7, 8, 9, 10, 11, 12, 13)
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4. A power supply circuit that generates four intermediate voltage levels with respect to a peak voltage level, said power supply circuit comprising two amplifiers each having a voltage follower configuration, two series-connected capacitors, and a switching means, wherein a first group of voltage levels comprises two intermediate voltage levels that are low level with respect to the peak voltage level and a second group of voltage levels comprises the remaining two intermediate voltage levels, wherein:
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said amplifiers and said series-connected capacitors generate the two voltage levels of the first group of voltage levels, and said switching means, controlled at a predetermined timing, switch said series-connected capacitors to generate the two voltage levels of the second group of voltage levels using a discharge voltage from each of said capacitors and the peak voltage level. - View Dependent Claims (5)
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6. A power supply circuit that generates four intermediate voltage levels with respect to a peak voltage level, said power supply circuit comprising one amplifier having a voltage follower configuration, at least three capacitors, and a switching means, wherein a first group of voltage levels comprises two intermediate voltage levels that are low level with respect to the peak voltage level and a second group of voltage levels comprises the remaining two intermediate voltage levels, wherein:
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said amplifier and one of said capacitors generate a first voltage level included in the first group of voltage levels, and said switching means, controlled at a predetermined timing, switches said one of said capacitors to generate a voltage level included in the second group of voltage levels using a discharge voltage of said capacitor and the peak voltage level, and said switching means, controlled at a predetermined timing, series-connects the remaining capacitors to generate the other voltage level included in the second group of voltage levels using discharge voltages of each of said remaining capacitors and the peak voltage level.
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14. A power supply circuit that generates four intermediate voltage levels with respect to a peak voltage level, said power supply circuit comprising one amplifier having a voltage follower configuration, three capacitors, and a switching means, wherein a first group of voltage levels comprises two intermediate voltage levels that are low level with respect to the peak voltage level and a second group of voltage levels comprises the remaining two intermediate voltage levels, wherein:
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said amplifier and two of said capacitors generate the two voltage levels included in the first group of voltage levels, wherein an output voltage of said amplifier and a discharge voltage of one of said capacitors is used to generate a first output voltage level that is greater than the output voltage of said amplifier and said first output voltage charges an external capacitance; and said switching means, controlled at a predetermined timing, switches one of said capacitors to generate a voltage level included in the second group of voltage levels using a discharge voltage of said capacitor and the peak voltage level, and said switching means, controlled at a predetermined timing, switches said external capacitance to charge another one of said capacitors for generating the other voltage level included in the second group of voltage levels. - View Dependent Claims (15)
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16. A power supply circuit for driving a display, comprising:
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a first power source terminal; a second power source terminal; a plurality of resistors connected in series between said first and second power source terminals; a first amplifier having its input coupled to a connecting point of adjacent resistors among said resistors and its output coupled to a first intermediate voltage output terminal outputting a first intermediate voltage level; a first capacitor having a first electrode and a second electrode; a first switch electrically connecting said first electrode with said output of said first amplifier in a first mode connecting said first electrode with and said first power source terminal in a second mode; and a second switch electrically connecting said second electrode with said second power source terminal in said first mode and connecting said second electrode with a second intermediate voltage output terminal outputting a second intermediate voltage level in said second mode.
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Specification