| 摘要 |
PURPOSE:To suppress the fluctuation of the electric power supplied to a load by providing a duty setting means which can set the digital value corresponding to the duty of a switching element at every period of the switching element. CONSTITUTION:The voltage corresponding to a lamp voltage VC detected by means of a lamp voltage detection circuit 1 is inputted to an A/D converter 4 and further inputted to a ROM 5 after the voltage is converted into a digital signal. Then the digital signal is converted into digital data corresponding to the duty corresponding to the value of the lamp voltage VC and inputted to a digital PWM circuit 6. In addition, signals having duties corresponding to the lamp voltage VC are inputted to the switching elements Q1-Q4 of an inverter circuit and low-frequency square-wave power is supplied to an electric discharge lamp Z. As a result, the occurrence of such a drift, etc., that occurs in an analog PWM circuit can be prevented and the fundamental frequency of the digital PWM circuit does not unnecessarily become higher even when the duty resolution is improved. Therefore, this inverter device can stably supply electric power. |
