# US 5,703,449 A · Controller for brushless DC motor without position sensor

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- Number: US 5,703,449 A
- Document ID: US5703449A
- Status: Granted
- Kind: A
- Application number: 08/615,073
- Filed: 1996-03-14
- Granted: 1997-12-30
- Earliest claimed: 1990-10-19
- Assignees: Seiko Epson Corporation
- Inventors: Takashi Nagate; Akihito Uetake; Yoshikazu Koike; Kunio Tabata
- Web page: https://patentgrep.com/patent/US5703449A

## CPC

- H02K 1/2746: the rotor consisting of magnets arranged with the same polarity, e.g. consequent pole type
- H02K 29/12: using detecting coils {using the machine windings as detecting coil}
- H02P 6/14: Electronic commutators
- H02P 6/18: without separate position detecting elements
- H02P 6/21: Open loop start
- H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53})
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS

## Abstract

A controller according to one embodiment restarts the motor when a commutation timing signal is mismatched with an output pattern mode. A controller according to another embodiment compares the motor speed with the reference signal to change the chopper frequency in accordance with the compared value. A controller according to still another embodiment continuously changes the chopper frequency in accordance with the motor speed. A controller according to yet another embodiment inhibits the position detection immediately after commutation in accordance with the current flowing through the motor. A controller according to another embodiment detects the position of the rotor in accordance with the waveform of the current flowing through the motor.

## Claims

### Claim 1

A controller for a brushless DC motor without a position sensor including an inverter for driving the motor under chopper control and utilizing a counter electromotive force generated in stator coils of respective phases as a rotor is rotated in order to detect a position of the rotor and thereby to generate a commutation signal, said controller comprising
a mode detector connected to the inverter for detecting
a commutation timing signal detector connected to said mode detector to generate a commutation timing signal,
an output pattern mode generator connected to said commutation timing signal detector to generate output patterns of several types with which said stator coils are excited,
a pattern coincidence detector connected to said commutation timing signal detector and said output pattern mode generator to detect a coincidence that signals output from said commutation timing signal detector and said output pattern mode generator match each other and
a starting controller connected to said pattern coincidence detector to stop a motor drive output once when no coincidence is detected by said pattern coincidence detector and to cause a restarting.

### Claim 2 (depends on 1)

A controller according to claim 1, wherein said pattern coincidence detector comprises an EX-OR gate connected to said output pattern mode generator and said commutation timing signal detector and a NAND gate connected to said EX-OR gate and said commutation timing signal detector to output a signal to said starting controller.