| 摘要 |
PURPOSE:To prevent the burning of a switching element in a power source circuit by generating a predetermined constant voltage higher than the voltage of a DC power source from a smoothing capacitor and varying the ON-time of the switching element when the voltage of the DC power source varies, thereby reducing the saturation of a coil. CONSTITUTION:A switching element 6 connected through a coil 5 to a DC power source 1 is switched by an oscillator circuit 3 for oscillating by comparing the voltage of a capacitor 3f charged by the power source 1 with a reference voltage produced from the output of a constant-voltage circuit 2 for maintaining the voltage of the power source 1 at a constant voltage. Since a predetermined voltage higher than the voltage of the power source can be produced at a smoothing capacitor 10 by stopping the switching operation of the switching element 6 through a reverse current preventing element 9 only when the voltage of the capacitor 10 becomes higher than a predetermined value and the on time of the switching element is varied when the voltage of the power source varies, the saturation of the coil can be reduced to prevent the burning of the switching element. |
