Abstract: A device for converting display screen into touch panel screen includes a projection screen; an image projection unit for projecting an image on the projection screen; a light pointer for emitting a light spot signal of a specific wavelength on the projection screen; an image detecting unit, which includes a fisheye lens for receiving the image on the projection screen to generate a fisheye distorted image; and an optical filter for filtering out the optical energy except the light spot signal of the specific wavelength; an image processing unit, coupled to the image detecting unit, for calculating a first position of the light spot on the projection screen according to the fisheye distorted image; and a message transmitting unit, coupled to the image processing unit, for outputting a touch panel signal according to the calculating result of the image processing unit.

Abstract: A ballast circuit adaptive to changes in the input voltage capable of providing a “floating” high output voltage for the operation of fluorescent lamps. The present invention employs an output voltage “floating” design in adjusting the high output voltage in response to the voltage difference between the output voltage and the rectified input voltage (i.e. error voltage) without using a feedback path from the output voltage.

Abstract: A ballast circuit adaptive to changes in the input voltages capable of providing a "floating" high output voltage for the operation of fluorescent lamps. The present invention employs an output voltage "floating" design in adjusting the voltage gain of the ballast circuit in response to the voltage difference between the output voltage and the rectified input voltage (i.e. error voltage).