| 摘要 |
PURPOSE:To finely control the brightness of a discharge lamp regardless of the brightness of the discharge lamp. CONSTITUTION:A microcomputer 4 is provided with a control section 4a, a data set section 4b, and a D/A conversion section 4c. The point where the signal A becomes the half 1.5V of the maximum output 3.0V is set as the switching output level. When the signal A is the switching output level or below, the data set section 4b sets the level of control data to a value double the value of the control data in the mode 1. the resolution in the D/A converter 4c becomes 1.5V/255=5.88mV, and the resolution double that in the mode 1 can be obtained. The level of the analog signal of the control data outputted from the D/A converter 4c is decreased to 1/2 by a level shifting circuit 6. The primary analog signal level of the control data is resumed. When it is inputted to an inverter control circuit 5, the output of an inverter circuit 2 can be correctly controlled. |
