Maximum power regulated battery charger

[54] MAXIMUM POWER REGULATED BATTERY CHARGER

[75] Inventor: Kris P. Dehnel, Cypress, Tex.

[73] Assignee: Compaq Computer Corporation, Houston, Tex.

[21] Appl. No.: 701,657

[22] Filed: May 16,1991

[51] Int.Cl.« H02J7/00

[52] UJS. CI 320/32; 320/35;

307/66

[58] Field of Search 320/32, 13, 14, 31,

320/35, 39; 363/21, 92; 307/66

[56] References Cited

U.S. PATENT DOCUMENTS

3,599,073 8/1971 Wilson et al 320/39

4,006,397 2/1977 Catotti et al 320/31

4,075,504 2/1978 Gnaedinger 307/66

4,276,591 6/1981 Quick 363/92

4,433,277 2/1984 Carollo et al 320/24

4,503,378 3/1985 Jones et al 320/20

4,677,363 6/1987 Kopmann 320/44

4,933,825 6/1990 Allington et al 363/16

5,021,679 6/1991 Fairbanks et al 307/66

5,055,703 10/1991 Scharnack 307/64

5,087,870 2/1992 Salesky et al 323/276

5,136,231 8/1992 Faulk 320/31

OTHER PUBLICATIONS Middlebrook, "Input Filter Considerations in Design

An AC adapter that allows a lower power rating while still providing the necessary power to a load which is substantially constant over a varying voltage range and to charge a discharged Ni-Cad battery in a desired time. The AC adapter regulates its output power to a maximum level just greater than the maximum of the load rather than providing a controlled current until a predetermined fully charged voltage is attained. In this manner, the output voltage and current are allowed to vary inversely with respect to each other in order to maintain the desired power level, allowing the output current level to be reduced as the voltage level increases. A regulated voltage mode is also provided to keep the output voltage from rising above a predetermined maximum level should the Ni-Cad battery be disconnected. One preferred embodiment includes a regulated current mode wherein the current through the Ni-Cad battery is maintained at the desired trickle level once the battery is fully charged.

30 Claims, 6 Drawing Sheets