Driving circuit for brushless DC motor

• US 20030102830A1
• Filed: 11/04/2002
• Published: 06/05/2003
• Est. Priority Date: 11/05/2001
• Status: Abandoned Application

• Current Assignee: Japan Servo Co., Ltd. (Nidec Corporation)
• Original Assignee: Japan Servo Co., Ltd. (Nidec Corporation)
• Inventors: Mizukami, Koji, Kubozuka, Eiji
• Application Number:
  US10/286,858
• Publication Number:
  US 20030102830A1
• Time in Patent Office: Days
• US Class Current: 318/254
• CPC Class Codes: H02P 6/16 Circuit arrangements for detecting position
• CPC Class Codes: H02P 6/28 Arrangements for controlling current H02P6/10 takes precedence

Abstract

The driving circuit comprises a current control signal generator means and a current switching circuit. The current control signal generator means comprises a current mode switching circuit and a current mode switching time setting means that counts reference clock pulses and outputs a counter signal until the number of pulses counted reaches a predetermined value. The current mode switching circuit chooses a three-phase current mode or a two-phase current mode according to the counter signal being transmitted or not and transmits the current mode chosen to the current switching circuit as current control signals.

Claims

1. A driving circuit for a brushless DC motor comprising;

a current control signal generator means that receives output signals of three magnetic pole position detection means for detecting a magnetic pole position of a permanent magnet of a rotor of the motor and generates current control signals, and

a current switching circuit that receives said current control signals and supplies exciting currents to three-phase stator windings of said motor;

wherein said current control signal generator means comprises a combination circuit, a two-phase current mode generator, a three-phase current mode generator and a current mode switching time setting means,

said combination circuit combines said output signals of said magnetic pole position detection means and generates composite signal waves,

said two-phase current mode generator receives said composite signal waves and generates a two-phase current mode to be transmitted to the current switching circuit when exciting currents are to be supplied to two windings of said three stator windings,

said three-phase current mode generator receives said composite signal waves and generates a three-phase current mode to be transmitted to the current switching circuit when exciting currents are to be supplied to all three windings of said stator windings,

said current mode switching time setting means receives said composite signal waves, detects an edge of said composite signal wave, generates an edge signal, counts reference clock pulses starting from said edge signal, continues to output a counter signal until the number of pulses counted reaches a predetermined value, and stops outputting said counter signal at the time when said number of pulses counted reaches said predetermined value and is reset, and

said current mode switching circuit receives said two-phase current mode, said three-phase current mode and said counter signal, chooses said three-phase current mode while receiving said counter signal from said current mode switching time setting means and transmits said three-phase current mode to said current switching circuit as said current control signals, and chooses said two-phase current mode when said counter signal is not received from said current mode switching time setting means and transmits said two-phase current mode to said current switching circuit as said current control signals.

2. The driving circuit for a brushless DC motor according to claim 1 wherein said current mode switching time setting means comprises;

an edge detection circuit that receives said composite signal waves from said combination circuit, detects said edge of said composite signal wave and generates said edge signal,

a reference clock signal generator that generates said reference clock pulses, and

a counter that is started by said edge signal, counts a number of said reference clock pulses, outputs said counter signal until said number of pulses reaches said predetermined value, and stops outputting said counter signal and is reset when said number of pulses reaches said predetermined value.

3. The driving circuit for a brushless DC motor according to claim 1 wherein said current mode switching time setting means comprises a digital control circuit.

4. The driving circuit for a brushless DC motor according to claim 1 wherein said current mode switching time setting means comprises a microcomputer.

5. The driving circuit for a brushless DC motor according to claim 1 wherein said current mode switching time setting means comprises a logical circuit.