| 摘要 |
PROBLEM TO BE SOLVED: To prevent the voltage across both ends of a capacitor from abnormally rising without detecting a condition of a load. SOLUTION: In a stationary mode, switching elements Q3 , Q4 are turned on/off synchronized with the frequency of an AC power source Ei, and switching elements Q1 , Q2 are turned on/off alternately at a high frequency. During this time, the on-period of the switching elements Q1 , Q2 are controlled so as to the voltage across hold both ends of a capacitor Ce to a reference voltage V11 . When the voltage across both ends of the capacitor Ce reaches a comparative voltage V2 higher than the reference voltage V11 , a nonstationary mode is selected by an action mode switching circuit MD, the switching elements Q1 , Q2 are turned on/off synchronized with the frequency of the AC power source Ei, and the switching elements Q3 , Q4 are tuned on/off at a high frequency. At no-load time, a reference voltage V12 higher than the reference voltage V11 and lower than the relative voltage V2 is selected. |
