| 摘要 |
PURPOSE:To prevent the discharge voltage change caused by the ambient temperature change by detecting and feeding back the change of the current flowing in a cathode discharge tube, and feeding a constant current to the transformer secondary winding with the output in response to it. CONSTITUTION:The current I flowing in a cathode discharge tube L is detected by a current detecting circuit 3 connected in series to the discharge tube L, and this detection quantity (change quantity due to the external condition change such as temperature) is fed back to a voltage control circuit 1. The circuit 1 compares the feedback quantity with the reference voltage Vref, applies the result to a transformer T via a switching circuit 2, and generates voltage V so that the preset current I in the secondary winding of a transformer T is made constant. The intensity of multiple discharge tubes can be stabilized. The reference voltage Vref is made the same for each cathode discharge tube driving circuit. The feedback quantity can be changed when only the reference voltage Vref is changed, and the intensity for individual tubes can be concurrently changed by the same quantity or at the same rate. |
