| 摘要 |
PURPOSE: To obtain the rapid discharge characteristics of a capacitor by connecting a resistor in series with a field effect transistor for connecting a gate terminal to a resistor voltage dividing point in a discharge circuit connected in parallel with the capacitor by inserting the capacitor charging diode in series between the voltage dividing point and the capacitor. CONSTITUTION: When turning on a power source, a capacitor C1 is charged through resistor R1 and a diode D. In this state, an FET Q3 is reversely biased by a voltage between its source and its gate, and turned off. Accordingly, soft starting characteristics are obtained. The source voltage of the FET Q3 at the time of turning off the power source is the charging voltage of the capacitor C1 , and a gate voltage = 0V. Accordingly, the maximum source-drain current responsive to the charge voltage can flow to the FET Q3 from the initial. That is, the discharging of the capacitor C1 of this case is conducted by the time constant of C1 and R1 . If the resistor R1 is selected to a small value, sufficiently fast discharging characteristic is obtained. Thus, stable rush current preventing operation can be always obtained. |
