| 摘要 |
PROBLEM TO BE SOLVED: To eliminate use of a switching transistor having a higher dielectric strength to realize reduction in size and low cost of the power supply apparatus as a whole by changing pulse width modulation control frequency with a pulse width modulation control frequency setting means on the basis of a detecting signal from a resonance detecting means. SOLUTION: An increase of resonance voltage when a fluorescent lamp 31 lights under the condition that the ON time is widened is detected with a coil 67 of a transformer, this detected signal is sent to a control circuit 52 and the control circuit 52 writes, on the basis of the detected signal, a value of an ON time subtraction register 66 to an ON time register for the first PWM circuit 63, fixes the ON time of the first PWM circuit 63 to a constant value and executes the control under this condition. |
