| 摘要 |
PURPOSE:To obtain a digital circuit which holds a final operation state before a power failure and recovers into the state before the power failure when fed with a current, by a capacitor for status holding and its charging circuit. CONSTITUTION:In the circuit shown in the figure, capacitor C1 is charged by way of transistor Q1 and diode D1 when terminal A is at level L, and discharged when via transistor Q3 when terminal B is at level H; respective states are outputted to terminal C. Now, if a power failure occurs at point Y with capacitor C1 charged, all transistors turn OFF and charges in the capacitor are being held. Since point P is at level H at point Z when the circuit recovers from the power failure, the circuit turns into the state before the power failure immediately. Adding a discharging circuit with an adequate discharging time constant to this circuit obtains a circuit which holds the state before a power failure for a constant time, so that a circuit can be obtained which is effective for the control of a pot-type petroleum burning system. |
