Digital driver circuit for electro-optical device and electro-optical device having the digital driver circuit

• US 6,384,806 B1
• Filed: 03/18/1999
• Issued: 05/07/2002
• Est. Priority Date: 03/24/1998
• Status: Expired due to Term

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Quinn, Michael J., Matsueda, Yojiro
• Primary Examiner(s): Lao, Lun-Yi
• Application Number:
  US09/271,335
• Time in Patent Office: 1,146 Days
• Field of Search: 345/147, 345/148, 345/89, 345/92, 345/94-95, 345/208-209, 345/99, 345/691-693
• US Class Current: 345/89
• CPC Class Codes: G09G 2310/0259 with use of an analog or digital ramp generator in the column driver or in the pixel circuit
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/3688 suitable for active matrices only

Abstract

A digital driver circuit and method for driving a liquid-crystal device or other electro-optical display device. Drive performance of the electro-optical device is improved while keeping power consumption low. The digital driver circuit receives a digital image signal as an input and generates an analog drive signal. A series selection circuit selects one series from plural series of standard multi-ramp waves having voltages that change in steps with the passage of time depending on the value of a low-order bit of the digital image signal. A time selection circuit selects, on a time axis, a voltage that changes in steps in at least the selected series of standbard multi-ramp waves depending on the value of a high-order bit of the digital image signal.

Claims

1. A driver circuit for an electro-optical device that receives an n-bit (n is a natural number not less than 2) digital image signal supplied from n bit lines, generates an analog drive signal corresponding to the digital image signal, and outputs the analog drive signal to a signal line comprising:

a series selection circuit that selects at least one series from plural series of standard multi-ramp waves, having voltages that change in steps with a passage of time, according to the n-bit digital image signal; and

a time selection circuit that selects a time of at least one of the selected series of standard multi-ramp waves and a wave based on the selected series of standard multi-ramp waves to generate at least one voltage, the time selection circuit having a PWM circuit that generates pulse signals having different pulse widths, and the series selection circuit having a decoder that decodes at least one portion of the digital image signal.

2. A driver circuit for an electro-optical device that receives an n-bit (n is a natural number not less than 2) digital image signal supplied from n bit lines, generates an analog drive signal corresponding to the digital image signal, and outputs the analog drive signal to a signal line comprising:

a series selection circuit that selects at least one series from plural series of standard multi-ramp waves, having voltages that change in steps with a passage of time, according to the n-bit digital image signal;

a time selection circuit that selects a time of at least one of the selected series of standard multi-ramp waves and a wave based on the selected series of standard multi-ramp waves to generate at least one voltage;

a voltage change circuit that changes at least one of the generated voltage and a voltage based on the generated voltage, the voltage change circuit comprising an SC-DAC (Switched Capacitor−

Digital to Analog Converter) circuit;

an inversion circuit that inverts a digital value of at least one portion of the digital image signal for input to the SC-DAC circuit, the SC-DAC circuit performing voltage subtraction by charge sharing depending on the inverted portion.

3. A method for driving an electro-optical device, comprising:

selecting at least one series from plural series of standard multi-ramp waves, having voltages that change in steps with a passage of time, according to an n-bit digital image signal; and

selecting a time of at least one of the selected series of standard multi-ramp waves and a wave based on the selected series of standard multi-ramp wave to generate at least one voltage; and

generating a pulse width modulated signal.

4. A method for driving an electro-optical device, comprising:

selecting at least one series from plural series of standard multi-ramp waves, having voltages that change in steps with a passage of time, according to an n-bit digital image signal;

selecting a time of at least one of the selected series of standard multi-ramp waves and a wave based on the selected series of standard multi-ramp wave to generate at least one voltage;

changing the generated voltage;

inverting a digital value of at least one portion of the digital image signal; and

performing voltage subtraction by charge sharing based on the inverted value.

5. A method for driving an electro-optical device, comprising:

selecting at least one series from plural series of standard multi-ramp waves, having voltages that change in steps with a passage of time, according to an n-bit digital image signal;

selecting a time of at least one of the selected series of standard multi-ramp waves and a wave based on the selected series of standard multi-ramp wave to generate at least one voltage;

changing the generated voltage; and

performing one of charge sharing and charge pumping using the generated voltage and a selected reference voltage.

6. A driver circuit for an electro-optical device that receives an n-bit (n is a natural number not less than 2) digital image signal supplied from n bit lines, generates an analog drive signal corresponding to the digital image signal, and outputs the analog drive signal to a signal line comprising:

a series selection circuit that selects at least one series from plural series of standard multi-ramp waves, having voltages that change in steps with a passage of time, according to the n-bit digital image signal;

a time selection circuit that selects a time of at least one of the selected series of standard multi-ramp waves and a wave based on the selected series of standard multi-ramp waves to generate at least one voltage;

a voltage change circuit that changes at least one of the generated voltage and a voltage based on the generated voltage, the time selection circuit receiving digital values corresponding to a first bit to an m-th bit (1≦

m<

p<

n, m and p are natural numbers), the series selection circuit receiving digital values corresponding to an m+1-th bit to a p-th bit, and the voltage change circuit receiving digital values corresponding to a p+1-th bit to the n-th bit.