LED backlight controller tuning way
LED backlight controller tuning way
Turn LED string light switch component ellipsis, the biggest advantages of this application can save the cost, but to provide a rough brightness adjustment, use eye persistence of vision slower response characteristics as a filter function, circuit switching frequency SuiDiao opened and closed, the light frequency in the frequency that move light Off, LED is still flowing current, output voltage drop, when ON the move light frequency, output voltage will be enough to make the LED string completely conduction, driver IC internal error amplifier is bound to increase the inductance energy, make the output voltage rise. In this way, line characteristics will be sacrificed, LED output voltage ripple will obviously increase, LED output current is neither pulse output nor nonlinear output, so the linearity of LED dimming current, LED average current and brightness will be poor. During the dimmer period, there may be flicker, so the dimmer period range will be limited, and the contrast of the dimmer will be significantly worse. EMI, audio interference, and water ripples on panel displays are all still present, so this is not a good way to dimmer.
LED has been almost fully used in backlight, and its penetration rate in lighting has been getting higher and higher. According to the application requirements of different systems, PWM and analog dimming methods are applicable to different fields respectively, and each has its own advantages and disadvantages. But now the development of the world's panels require low power consumption and high resolution, in order to save the light guide plate, the light storage decreases, making the panel more sensitive to noise interference, and PWM dimming light belongs to low frequency dimming, so the quality change of the panel brightness is more easily affected. The analog dimming belongs to amplitude dimming, and the adjustment of current compared with brightness is linear control, so the quality of panel brightness will not be disturbed by dimming. In order to completely improve other problems caused by PWM dimming, some panel manufacturers have gradually adopted analog dimming instead of pulse width dimming. In response to this trend, the newly launched LD5857 driver of Tonga has excellent dimming linearity in 0% ~100% dimming range. As for simulating dimming color bias, panel manufacturers have also actively improved the relationship between LED current and color offset, and have achieved good results.
Because modern people generally use the computer for long, easy to cause eye fatigue problems, the reason for backlit display panel is used in PWM dimming, although PWM dimming frequency is higher than the human eye persistence of vision, so feel LED flashing phenomenon, but the PWM dimming is still belong to a low frequency switch LED to move light, long time use, PWM dimming way is a burden to her eyes still, so eye fatigue problem of easy, simulate the dimmer way can solve the general computer screen flicker on the eyes caused by fatigue, also provides a good display performance. Although at present in terms of higher order LCD TV, due to demand a higher contrast features, so still adopts PWM dimming, LCD TV and display, but usually have also started to assessment and adopts analog dimming method, believe in the near future, analog dimming way will gradually widely used in the monitor and LCD TV backlight.
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