The invention discloses a design method and light fitting of a utility model of filament lamp, which is supplied power in direct current and frequency conversion modes through two output ends of a rectifier connecting in parallel with switches of a wave filter capacitor and semi-conductor. An oscillating circuit provides square wave signal, sine wave signal and pulse signal to control the switch of the semiconductor, and to control brightness of the filament lamp through regulating the square wave signal, the sine wave signal and the pulse signal to control the duty cycle of the semiconductor switch. The invention is capable of eliminating the 100HZ power frequency composition in the filament lamp while being directly supplied power by commercial power, and making light more gentle; the invention is also capable of conveniently adjusting continuous brightness or darkness of light and has function of stabilizing voltage. |