DC Motor soft-start circuit

• US 4,510,422 A
• Filed: 02/06/1984
• Issued: 04/09/1985
• Est. Priority Date: 02/09/1983
• Status: Expired due to Term

• Current Assignee: Tokyo Shibaura Denki Kabushiki Kaisha (Toshiba Corporation)
• Original Assignee: Tokyo Shibaura Denki Kabushiki Kaisha (Toshiba Corporation)
• Inventors: Ogura, Masahiko
• Primary Examiner(s): Witkowski, Stanley J.
• Assistant Examiner(s): Ro, Bentsu
• Application Number:
  US06/577,337
• Time in Patent Office: 428 Days
• Field of Search: 318/254, 318/254 A, 318/138, 318/439, 363/49
• US Class Current: 318/400.1
• CPC Class Codes: H02P 6/20 Arrangements for starting H02P6/08 takes precedence

Abstract

A DC motor driving circuit includes an exciting coil switching circuit for selecting from among polyphase exciting coils of a brushless motor those coils to be excited and their excitation directions. An excitation current control transistor is connected between a DC excitation current supply line and a DC power supply. A timing signal producing circuit including a time constant circuit is produced so as to limit starting current at the time of starting of the motor. The excitation current control transistor is controlled by the timing signal at the time of starting of the motor.

Claims

1. A DC motor driving circuit comprising:

a motor having polyphase exciting coils;

a DC power supply;

an excitation current supply line for supplying excitation current from the DC power supply to the polyphase exciting coils;

exciting coil switching means connected to the excitation current supply line and the polyphase exciting coils, for sequentially switching the polyphase exciting coils;

excitation current control means for controlling the magnitude of the excitation currents to be supplied to the exciting coils; and

timing signal producing means for producing a timing signal which, when the motor is started, is supplied to the excitation current control means so as to suppress the magnitude of the excitation current, said timing signal producing means including a start switch adapted to be turned ON when the motor is started;

a time constant circuit for producing a signal which is lowered from a predetermined level to a ground level during a predetermined period of time following the turning on of the start switch;

a triangular wave producing circuit; and

a comparator connected to receive an output signal of the time constant circuit and an output signal of the triangular wave producing circuit and supply pulses which successively decrease in their widths, to the excitation current control means.

2. A DC motor driving circuit according to claim 1, in which said excitation current control means includes a semiconductor switch which is connected between the DC power supply and the excitation current supply line and controlled by an output signal of the timing signal producing means.

3. A DC motor driving circuit according to claim 1, in which said excitation current control means includes a plurality of transistors which constitute part of said exciting coil switching means.

4. A DC motor driving circuit according to claim 1, in which said motor is a brushless motor.