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US005130620A
United States Patent [19] [li] Patent Number: 5,130,620
Inaji et al. [45] Date of Patent: Jul. 14, 1992
[54] BRUSHLESS DC MOTOR WITHOUT A POSITION SENSOR
[75] Inventors: Toshio Inaji, Minoo; Kenichi Honjo, Kobe; Makoto Gotou, Nishinomiya, all of Japan
[73] Assignee: Matsushita Electric Industrial Co., Ltd., Osaka, Japan
[21] Appl. No.: 646,548
[22] Filed: Jan. 29, 1991
[51] Int CI.* H02P 6/00
[52] U.S. CI 318/254; 318/439
[58] Field of Search 318/254, 254 A, 138,
318/439, 685, 696, 628, 615, 616, 618, 500;
388/804, 805, 811, 816, 817, 911
[56] References Cited
U.S. PATENT DOCUMENTS
4,103,216 7/1978 Hayes 318/685
4,119,901 10/1978 Leenhouts 318/685
4,220,904 9/1980 Leenhouts et al 318/696
4,429,268 1/1984 Yajima et al 318/696
4,480,218 10/1984 Hair 318/696
4,684,866 8/1987 Vehmer et al 318/696
4,780,651 10/1988 Nakano et al 318/254
4,874,993 10/1989 Tanaka et al 318/254
COUNTER ELECTROMOTIVE
FORCE DETECTING CIRCUIT
