| 摘要 |
A dimmer comprises a PWM circuit for driving through pulse width modulation and a switching device formed on the same chip. The switching device has a driving circuit, an overheat cut-off protecting circuit, a main control FETQA to be a semiconductor switch, a first reference FETQB for generating a reference voltage and a resistor. Furthermore, overcurrent detecting means is implemented by a comparator for detecting a difference between the reference voltage and a drain-source voltage of the main control FETQA and an output thereof cuts off and controls the driving circuit so that the main control FETQA is ON/OFF controlled. The overcurrent detecting means and ON/OFF control means have a soft start function of suppressing a rush current flowing to loads of an illuminating system.
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