| 摘要 |
PROBLEM TO BE SOLVED: To prevent drop of the conversion efficiency of a switching power unit, accompanying the increase of the switching loss of the main switching element at waiting, that is at a light load, by performing the intermittent oscillation to stop the main switching element which constitutes the switching power unit for a specified time at waiting of an apparatus. SOLUTION: This is switching power unit is of such a constitution that it converts the DC voltage of a DC power source 11 into high-frequency AC voltage by turning on and off of a main switching element Q1 by the control of a main controller 14, and inputs it into a primary winding 16 of a switching transformer 16, and rectifies and filter the high frequency AC voltage generated in a secondary winding 16b into a prescribed DC output voltage prior to supply to load, and here a sub-controller 30 is connected to the auxiliary winding 16d of the switching transformer 16, and a sub-switching element Q2 is connected to this sub-controller 30 so as to compulsively turn off the main switching element Q1, and the sub-controller 30, when DC output voltage reaches a preset value, turns on the sub-switching element Q2 by a specified time and forcibly turns off the main switching element Q1 by a prescribed time.
|
