| 摘要 |
A system simplification can be achieved by reducing the number of sensors required to detect currents and voltages when an output current is estimated. A switching power supply device 6 includes a current transformer 12, a switching circuit 13, a rectifying circuit 15, a smoothing circuit 16, an input voltage detecting circuit 18, a control part 19, an output voltage detecting circuit 22 and a PWM signal generating part 30. The control part 19 calculates a duty rate and an average value of voltage of the secondary side voltage of the current transformer 12 detected by the input voltage detecting circuit 18 based on a waveform of the detected voltage. The control part 19 calculates an output current lo based on the calculated duty rate, the calculated average value of voltage and an output voltage Vo detected by the output voltage detecting circuit 22. |
