| 摘要 |
PURPOSE:To make it possible to precisely control illumination with a small and light device by providing a first illuminance setting unit supplying a first illuminance setting signal for a first illuminance pattern, a second illuminance setting unit supplying a second illuminance setting signal for a second illuminance pattern, and an output signal generation circuit having a pulse width in proportional to a set signal. CONSTITUTION:A DC exciting power source 28 has a transformer 80, connected to an input side of an autotransformer type voltage regulator 24, and a rectifier 82, connected to an output side of the fransformer 80 and converting AC current to DC output current; the DC output current is smoothed with a condenser 84 and used as a DC exciting current I of a control winding 26, is controlling the magnetic flux of a first series winding 46 shifted to a magnetic shunt iron core 44 and of a shunt winding 48 with a differential joining condition of a second series winding 50 to an output winding composed of the windings 46 and 48 made to change, and can variably controlling output voltage in an output end. In this case, an illuminance setting signal from a first or a second illuminance setting unit 106 or 108 is compared with a standard power source, and a comparing signal C1 corresponding to a difference signal is supplied to a minus input end of a comparator 114. The comparator 114 compares a triangular wave signal S1, supplied from a triangular wave generator 116 to a plug input end, with the signal C1, and supplies an output signal P1 having a pulse width in proportional to a difference to the base of a drive transistor 89. Energy loss can be minimized since the illuminance in a first stage and that in a second stage can be set. |
