| 摘要 |
PROBLEM TO BE SOLVED: To prevent the breakdown of a circuit element by providing a control means for making voltages supplied to heaters a prescribed value or below, when a switching means switches the connection of the heaters and a power supplying means. SOLUTION: Halogen heaters 1 and 2 are connected to a constant voltage output circuit 3 through triac 4 and 5 and they are used to switch the connection of the halogen heaters 1 and 2 and the constant voltage circuit 3. A voltage detecting circuit 21 outputs the output voltage of the constant voltage output circuit 3 and a control IC 20 controls the ON duty of a chopping FET 17 for executing turning on/off, so as to make the output voltage constant or output and input current waveforms similar ones. Since the connection of the halogen heaters 1 and 2 and the constant current output circuit 3 is switched only when a normal voltage value or below is obtained, counter electromotive force generated by an inductor 18 is made small to prevent the breakdown of the circuit element. |
