| 摘要 |
PURPOSE: To remove ripple components of discharge current without using an LC filter circuit by controlling a ripple component signal after rectification based on the quantity of discharge current, adding the signal to a discharge current return signal, and controlling a DC/DC converter. CONSTITUTION: A ripple component of d.c. output rectified by a rectifying part 2 is detected through a coupling capacitor C and an insulated transformer TR and amplified by an amplifier OP1. Then, the component reaches an input terminal P of a control part 6 through limiting resistors R1-R6. After that, in the input terminal P, addition of the component and a discharge current feed back signal in order to make discharge current constant is carried out. Based on the signal obtained by the addition, a switching width of a DC/DC converter part 4 is controlled and a discharge lamp is lighted stably, At that time, switching elements SW1-SW5 connected with respective limiting resistors R2-R6 in parallel are controlled corresponding to the quantity of the discharge current and the intensity of the ripple component signal can be controlled. |
