| 摘要 |
The present invention discloses a method and an apparatus for power demand load leveling of a power supply driving a plurality of LED's through the use of pulse width modulation. A first modulating signal provided from a pulse width modulator is applied to a delay means for generating second, third and fourth modulating signals each delayed from the previous modulating signal by a predetermined time. The modulating signals are used to modulate control signals corresponding to four groups of associated LED's in order to permit only one group of LED's to be turned on at any one time, although more than twenty five percent of the LED's may be active at any one time. Each of the first, second, third and fourth modulating signals are applied to a different group of four groups of activation switches along with their respective control signals to enable the switches and activate an associated group of LED's. The predetermined time, representing a time delay between each of the modulating signals, is chosen to correspond to twenty five percent of the period of the first modulating signal. Due to the time delay between the inputs of the different modulating signals, only one group of LED's will change state from off to on at any one time even though each group of LED's may be activated during a period and more than twenty five percent of the LED's may be active at any one time.
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