| 摘要 |
<p>PURPOSE:To decide whether the contents held by a memory, etc., are correct or not when the power failure is recovered in case a battery back-up circuit works at power failure, by measuring the voltage of a capacitor storing the voltage value of a battery at the time of recovering the power failure. CONSTITUTION:In a normal state a power supply +VCB of a memory, etc., is supplied by +VC and at the same time a battery Ba undergoes the tricle charging by +VD. Thus a capacitor C is charged. If a power failure occurs under such conditions, both +VD and +VC are not available, and therefore the +VCB is supplied from the battery Ba. Hereafter, the voltage of the Ba and the both-terminal voltage of the capacitor C drop gradually. When the power failure is recovered, both +VD and +VC are applied. As a result, both +EB and +EC rise up quickly together with the +VCB. Thus the voltage level set before occurrence of the power failure is obtained. Then the both-terminal voltage of the capacitor C rises up gradually, therefore the +VCB set right before recovery of the power failure is obtained by measuring the both-terminal voltage EA of the capacitor C after recovery of the power failure.</p> |
