Patent Application
20070145906
The present invention relates to a backlight module actuation method and particularly to an actuation method that regulates an unsaturated luminance cycle in a saturated luminance condition of a backlight module to generate switch kinetic energy for a transformer to eliminate parasite capacitance.
In the technology of display devices, the backlight module plays an important role. It generates a uniform luminance to present more crisp colors for a display panel. However, the backlight module generally is driven by high voltage. In the event that the current of the backlight module is not stable or maintains a saturated luminance for a long period of time, a scattering parasite capacitance effect occurs. This not only affects the entire luminance, the displaying picture of the display panel also fluctuates. This is not desirable to viewer's vision.
To remedy the problem of parasite capacitance, U.S. Pat. No. 6,798,151 discloses a technique to neutralize the leaking current and charges generated by parasite capacitance between the display device and the backlight module so that the phenomenon of unbalanced current flowing through lamp tubes caused by the leaking current is eliminated. And the light source of the lamp tubes can be maintained evenly to enable the display panel to get a uniform luminance in a wider range. That patent has an external metal mask on a display panel module to receive directly or through a linking element a signal, or a plastic middle layer in the external metal mask to receive the signal, thereby to eliminate, neutralize or offset the residual charges on the display panel.
But the aforesaid approach merely partly solves the problem. When the scattering parasite capacitance is generated, the display panel is already being interfered. And when the display luminance is saturated in normal conditions, the parasite capacitance exists almost constantly. Hence the aforesaid patent cannot neutralize or eliminate the parasite capacitance instantly. As a result, the picture quality suffers.
Therefore the primary object of the present invention is to solve the aforesaid disadvantages. The present invention provides a modulated unsaturated luminance cycle in a dimming cycle of a backlight module in a saturated luminance condition. And an oscillation amplitude time series of the duty cycle of a transformer at the rear end is set according to the dimming cycle and a switch kinetic energy is formed in the unsaturated luminance cycle. The switch kinetic energy can eliminate the parasite capacitance while the backlight module is in the saturated luminance condition.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.
Please referring to
setting a saturated luminance 10 of a backlight module: The saturated luminance generally means the maximum setting brightness presentable on the backlight module. Presenting of the brightness usually is defined by the kinetic energy outputable by a transformer at the rear end or the maximum driving kinetic energy sustainable by the backlight module. The maximum saturated luminance has varying limitations based on different material characteristics of the backlight module. In this invention the saturated luminance is defined by the scattering parasite capacitance occurred in the maximum driving kinetic energy sustainable by the backlight module;
determining a dimming cycle 20 of the saturated luminance and modulating a unsaturated luminance cycle E2 in a dimming cycle E1: The dimming cycle E1 is the maximum brightness value set for the backlight module. In the present techniques, the dimming cycle E1 defines every pulse signal to oscillate at the maximum amplitude of the same voltage. Output is mostly in the form of square waves output by a pulse-width modulator (PWM). To facilitate discussion of the technical features of the invention, the dimming cycle E1 and duty cycle are presented in sinusoidal waves; and
determining a duty cycle 30 of the saturated luminance: The present invention sets an oscillation amplitude time series of the duty cycle of the transformer at the rear end based on the dimming cycle E1 to output kinetic energy to drive the backlight module. As the unsaturated luminance cycle E2 is modulated in the dimming cycle E1 of the saturated luminance, a switch kinetic energy is formed in the unsaturated luminance cycle E2 of the duty cycle of the transformer. Based on different width of the unsaturated luminance cycle E2 (or so called pulse wave composition), (such as the unsaturated luminance cycle E2 of a single pulse wave shown in
While the preferred embodiments of the invention have been set forth for the purpose of disclosure, modifications of the disclosed embodiments of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the invention.
