| 摘要 |
PROBLEM TO BE SOLVED: To provide a phase control dimmer constituted to be able to accurately control power supplied to a lamp, and to accurately control the dimming operation of the lamp, even if there is influence due to noise. SOLUTION: A photocoupler PH is turned off, while the value of a power voltage Vb is below a predetermined voltage level Vth0 and becomes sufficiently low to turn the photocoupler PH off, for example, it is lower than 15 V. During this period, a current outputted from a diode bridge circuit DB1 through a resistor R2 flows into a resistor R1 because a switching element SW1 is turned on. Thus, a noise current is bypassed to the resistor R1, even if a noise generating device is connected to the same commercial power supply AC and the noise generated at the noise generating device is superposed onto a power voltage Vc'. Accordingly, the photocoupler PH is turned off, without fail, even if the power voltage Vc reaches a zero-cross point, even though the waveform of the power voltage Vc' at a point c' fluctuates around the zero-cross point, when the noise generating device is connected to the same commercial power supply AC. COPYRIGHT: (C)2011,JPO&INPIT |
