| 摘要 |
PURPOSE:To match an electric apparatus to environmental conditions or the like to drive it in an optimum state by changing the rate of power supply to a load in two steps and making it possible to regulate one power supply rate at least. CONSTITUTION:A load 2 and a switching element 3 such as a TRIAC are connected in series to a commercial AC power source 1. When the operation time of a latch circuit 11 does not reach a prescribed time, a control circuit 9 supplies power interruptedly to the load 2 by 100% power supply rate to hold the load 2 at a maximum temperature. After the operation time of the latch circuit 11 reaches the prescribed time, the control circuit 9 supplies power interruptedly to the load 2 by the power supply rate determined by a duty ratio of a multivibrator 10 to hold the load 2 at a set temperature. The duty ratio of the multivibrator 10 is varied to drive the electric apparatus in an optimum state in accordance with environmental conditions or the like. |
