| 摘要 |
PROBLEM TO BE SOLVED: To provide a high performance switching power supply in which generation of power loss due to a dummy resistance is avoided or reduced while suppressing component cost increase, and increase in the output voltage can be suppressed even at the time of low load current.SOLUTION: In a switching power supply including a main switching element Tr1 subjected to duty control based on a control period defined by an oscillation circuit, and a coil L1 for storing the energy while the main switching element Tr1 is turned on, and feeding the stored energy to the load side while the main switching element Tr1 is turned off, a MOS-FET(Tr2) is used as a capacitive element for setting the oscillation frequency of the oscillation circuit, and a frequency switching circuit 3 for switching the oscillation frequency of the oscillation circuit by switching the state of the MOS-FET(Tr2) when entering a predetermined low load current state is provided. |
