| 摘要 |
PURPOSE: To prevent a rush current completely by connecting by thyristor for switching short-circuit or opening of a discharge resistor discharging the charge in a smoothing capacitor for the purpose of smoothing an output waveform in series to the discharge resistor. CONSTITUTION: A DC power supply circuit 50 provided with a rush current prevention circuit is made up of a thyristor 51 connecting in series to a discharge resistor 19 to open the discharge resistor 19 till the voltage across a smoothing capacitor 17 reaches the maximum output voltage Vdmax of rectifier diodes 15a-15d and to connect the discharge resistor 19 when the voltage across the capacitor 17 reaches the maximum output voltage Vdmax and up of a driver 53 controlling ON/OFF of the thyristor 51. Then a switch 33 is used to conduct a current limit resistor 31, and when the output voltage of the smoothing capacitor 17 detected by a comparator 37 exceeds a prescribed value, the thyristor 51 activates the discharge resistor 19 and the switch 33 short circuits the current limit resistor. Thus, a rush current caused by charging the smoothing capacitor 17 is completely prevented when power is applied. |
