FCC算法叙述.docVIP

Compensated EDV (CEDV) Theory and Operation for bq2063 TI Confidential June 26, 2001 Introduction: Methods that use battery voltage to determine a near empty battery condition have existed from the earliest day of battery power electronics. The simplest form consisted of a voltage comparator that tested a voltage proportional to the battery voltage against a reference that represented a near empty battery. When the battery voltage was found to be at or below the near empty condition, a warning was given to the user followed by the eventual shut down of the equipment. There are several issues with this method. The battery voltage varies under load and temperature especially near the end of capacity. This is the good news. This allows a small change in capacity to change the battery voltage by a very measurable amount. Therefore, detecting the end of capacity condition is just a matter of monitoring battery voltage. However, the method can generate early or late warnings. For example, when the battery is discharged to near the warning level at a light load and then the load is increased to high load; the battery voltage may drop much below the empty warning. In this situation, the warning will not provide adequate time for the user or system to respond. A similar problem exists for temperature. If the battery temperature is lowered near the end of capacity and a large load applied, the warning of low battery may not give adequate time for the system or user to gracefully shut down the system. So what can be done? Smart Battery System (SBS) Solution: The Smart Battery System solution was derived by evaluating the battery management issues, the relevant issue here being an adequate and dependable warning of a near empty battery. Many battery types have fairly flat discharge profiles with sharp knees at the end of capacity. The actual problem is providing a dependable warning of a near empty battery that does not warn too early or too late. Warning too ea