| 摘要 |
PROBLEM TO BE SOLVED: To effectively dim the discharge lamp by executing variable control for the amplitude of a high frequency power supply in proportion to a command value by a chopper circuit part, and also executing variable control for the frequency of a high frequency power supply in proportion to a command value by an inverter circuit part. SOLUTION: A chopper circuit part 9 allows the output of a switching transistor Q1 for electric power to be smoothed out by a smoothing actor L2 and a smoothing capacitor C2 so as to allow variable control for the amplitude of a DC power supply to be executed. The aforesaid output is returned to an error operator 13, the difference between the output and the amplitude command value Vref of an amplitude command producing part is thereby obtained, and the difference is sent to a drive circuit 15. The circuit 15 allows the input electric power of an inverter circuit part 10 to be controlled to be the amplitude command value Vref. Besides, the frequency command value Fref of a frequency side command value producing part 7 is fed to a drive pulse generator 20, and drive pulses each amplitude of which is changed in proportion to the command value, are generated in drive circuits 16 through 19. And the circuit 10 converts an input DC power supply to a high frequency power supply based on the command value Fref by pulse amplitude control so as to be sent to a feeder line 2 through a transformer 21 and output terminals 22a and 22b. |
