| 摘要 |
<p>PURPOSE:To reduce a noise by providing a dividing circuit for dividing a rectangular wave signal, and lighting an illumination load by a frequency equal to an output frequency of the dividing circuit, so as to reduce a shift component of the frequency. CONSTITUTION:Voltage input from a power supply line is converted into DC power in a rectifying circuit 15, to produce an output in accordance with load voltage of an illumination load 3 by a step down chopper circuit. Then, since a step down chopper circuit output, appearing in both ends of a smoothing capacitor, is DC power, it is reversed to be changed into AC power, in a full- bridge type inverter mainly composed of transistors(Tr) 9 to 12, and supplied to the load 3. Thus, the load 3 is lighted by rectangular wave power of frequency corresponding to an operating frequency of the Tr 9 to 12. This operating frequency is generated by inputting a lighting signal, in which a dimming signal from a duty ratio variable rectangular wave signal generator 6 is converted in a dividing circuit 7, to a control circuit 8. Then by selecting dividing ratio, when the load 3 is lighted by a signal synchronized with each other, noise generation to a duty ratio part of the dimming signal is eliminated.</p> |
