| 摘要 |
PURPOSE:To change the brightness of an incandescent lamp with a simple circuit and little noise and to miniaturize a device by connecting the incandescent lamp and a TRIAC in series with an AC power supply, and supplying one of half waves constantly and the other intermittently. CONSTITUTION:When voltage output from an oscillation circuit 5 is at H level, pulses output from a zero-cross detection circuit 3 are applied directly to a transistor 6 and a TRIAC 2 supplys full waves to an incandescent lamp 1 so that a bright full-wave lighting state is started. When voltage output from the circuit 5 is at L level, pulses output from the circuit 3 are divided into halves and are applied to the transistor 6 and the TRIAC 2 is ignited with half waves and half waves are supplied to the incandescent lamp 1 so that a dark half-wave lighting state is started. Since the lighting states are switched from one to the other near the zero cross point of an AC power supply, switching noise is hardly produced and variable illumination control is enabled by changing the period and waveform of output square waves. |
