ENERGY SAVING, SELF-REGULATING BACKUP CELL RECHARGER
Original Publication Date: 1988-Oct-01
Included in the Prior Art Database: 2001-Nov-02
This circuit meets the need of a backup cell to be quickly recharged without excessively loading the charg- ing source, and without wasting main cell charge once the backup cell is fully recharged. Referring to Figure 1, a backup cell (BT2) supplies retention voltage to an IC when the main source (VW) is off. During this time, the Vm source drops to just below one cell voltage, minus a diode drop, as in a paging receiver. When Vdd comes back on, we desire to recharge BT2 through Vda. The backup cell is prevented from discharging during reten- tion mode through any path other than the IC, hence extending retention time for a given cell capacity.