Invention Application
US20150145439A1 PRE-CHARGING INDUCTOR IN SWITCHING CONVERTER TO ACHIEVE HIGH PWM DIMMING RATIO IN LED DRIVERS 有权
切换转换器中的预充电电感器可实现LED驱动器中的高PWM调光比

PRE-CHARGING INDUCTOR IN SWITCHING CONVERTER TO ACHIEVE HIGH PWM DIMMING RATIO IN LED DRIVERS
Abstract:
In a method for controlling a current regulator for dimming an LED load, a dimming signal has a duty cycle that controls the LED ON-time and LED OFF time at a fixed frequency. The regulator is controlled by the dimming signal to only supply current to the LED load during the LED ON-time. The regulator includes an inductor. The inductor current at the end of an ON-time is detected and its value is stored. During the OFF-time, the inductor is pre-charged to the current level matching the stored value, while the regulator's feedback loop is frozen during the OFF-time to not change its feedback control signal. Upon the next ON-time, the regulator begins supplying current to the LED load with the pre-charged inductor current, so there is no initial decrease in the delivered LED current. Therefore, the current pulse magnitudes are constant even with very low duty cycles.
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