PWM ILLUMINATION CONTROL CIRCUIT WITH LOW VISUAL NOISE FOR DRIVING LED

• US 20070114949A1
• Filed: 01/16/2007
• Published: 05/24/2007
• Est. Priority Date: 12/08/2003
• Status: Abandoned Application

• Current Assignee: Beyond Innovation Technology Co Ltd
• Original Assignee: Beyond Innovation Technology Co Ltd
• Inventors: Yu, Chung-Che, Huang, Shih-Chung, Chang, Bor-Yuh
• Application Number:
  US11/623,326
• Publication Number:
  US 20070114949A1
• Time in Patent Office: Days
• US Class Current: 315/247
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A pulse width modulation (PWM) illumination control circuit with low visual noise for driving a light-emitting diode (LED) is provided. An illumination control pulse-generating unit is used to generate an illumination control pulse signal according to an illumination-adjusting signal. The duty cycle or frequency of the illumination control pulse signal varies within a predetermined scope for controlling a DC/DC converter to drive the light-emitting diode so that overall visual noise level of the PWM illumination control circuit is improved.

Claims

1. A pulse width modulation illumination control circuit for controlling the illumination of light-emitting diodes inside a liquid crystal display, comprising:

an illumination control pulse-generating unit, for receiving an illumination-adjusting signal and generating an illumination control pulse signal according to the illumination-adjusting signal, wherein a frequency of the illumination control pulse signal varies with time within a predetermined range; and

a DC/DC converter, coupled to the illumination control pulse-generating unit for driving the light-emitting diodes according to the illumination control pulse signal.

2. The control circuit of claim 1, wherein the illumination control pulse-generating unit is implemented using a microprocessor.

3. A pulse width modulation illumination control circuit for controlling the illumination of light-emitting diodes inside a liquid crystal display, comprising:

an illumination control pulse-generating unit, for receiving an illumination-adjusting signal and generating an illumination control pulse signal according to the illumination-adjusting signal, wherein a phase shift of the illumination control pulse signal varies with time within a predetermined range; and

a DC/DC converter, coupled to the illumination control pulse-generating unit for driving the light-emitting diodes according to the illumination control pulse signal.

4. An illumination control pulse generating device for receiving an illumination adjusting signal, the illumination control pulse generating device comprising:

a random signal generating unit, for generating a random signal;

a combine unit, coupled to the random signal generating unit for combining the random signal with the illumination adjusting signal to form a random signal combining illumination adjusting signal; and

a comparator, coupled to the combine unit for comparing the random signal combining illumination adjusting signal with a comparing signal to produce a illumination control pulse signal, wherein a frequency of the illumination control pulse signal varies with time within a predetermined range.

5. The illumination control pulse generating device of claim 4, wherein the random signal generating unit is a noise generator.

6. The illumination control pulse generating device of claim 4, wherein the combine unit is an analogue adder.

7. The illumination control pulse generating device of claim 4, wherein the comparing signal is a triangular wave.