| 摘要 |
PROBLEM TO BE SOLVED: To make the use of a switching power supply convenient and to improve working efficiency by feeding back at least a constant-voltage control signal to a control means until output power becomes rated power and feeding back a constant-power signal to the control means when the output power exceeds rated power. SOLUTION: When output power is smaller than rated power, a switching transistor TR1 is turned on or off so that an output voltage becomes a constant voltage since a voltage comparison signal is inputted from an addition circuit part 11 to a control circuit 7. More specifically, a switching power supply becomes a constant voltage control mode. When the output power is larger than the rated power, the switching transistor TR1 is turned on or off within a range where the output power is equal to or less than the rated power since an addition signal of a voltage comparison signal and a power comparison signal is inputted. Accordingly the switching power supply becomes a constant power control mode, an output current is limited and a constant voltage is maintained, thus continuing the constant voltage control mode.
|
