BLDC motor noise reduction using constant bus current control commutation
First Claim
1. A control system for a motor including a plurality of phases, comprising:
- a voltage source for providing a DC bus current; and
an inverter having a switching circuit for regulating the DC bus current to a fixed current level, wherein the switching circuit defines alternating overlapping periods and non-overlapping periods and delivers the fixed current level to one of the phases during the non-overlapping periods, and wherein the switching circuit supplies a decreasing current level to a first phase and an increasing current level to a second phase during an overlapping period such that said first and second phases share the fixed current level and a sum of current that is supplied to said first phase and said second phase is substantially equal to said fixed current level.
4 Assignments
0 Petitions
Accused Products
Abstract
A motor control system creates a rounding effect on square wave phase currents which results in reduced acoustic noise. The control system includes a voltage source for providing a DC bus current, and an inverter. The inverter has a switching circuit for regulating the DC bus current to a fixed level. The switching circuit also forces consecutive phases of the motor to share the bus current at commutation. Forcing consecutive phases of the motor to share a desired amount of the DC bus current creates a “rounding” effect on the phase currents, which results in reduced acoustic noise. The preferred inverter has a plurality of transistors, and a control module. The control module selectively engages the transistors such that each phase of the motor has a phase turn-on point that occurs before a phase turn-off point of a preceding phase. The control module also pulse width modulates the transistors such that the DC bus current is regulated to the fixed level. The result is a motor control system and method that is less expensive and produces less acoustic noise than conventional noise.
-
Citations
16 Claims
-
1. A control system for a motor including a plurality of phases, comprising:
-
a voltage source for providing a DC bus current; and
an inverter having a switching circuit for regulating the DC bus current to a fixed current level, wherein the switching circuit defines alternating overlapping periods and non-overlapping periods and delivers the fixed current level to one of the phases during the non-overlapping periods, and wherein the switching circuit supplies a decreasing current level to a first phase and an increasing current level to a second phase during an overlapping period such that said first and second phases share the fixed current level and a sum of current that is supplied to said first phase and said second phase is substantially equal to said fixed current level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
a plurality of transistors coupled to the motor and the voltage source; and
a control module coupled to the transistors.
-
-
3. The control system of claim 2 wherein the control module selectively enables the transistors such that each phase of the motor has a phase turn on point that occurs before a phase turn off point of a preceding phase.
-
4. The control system of claim 2 wherein the control module pulse width modulates the transistors such that the DC bus current is regulated to the fixed level.
-
5. The control system of claim 4 wherein the inverter further includes a current measurement device for measuring the DC bus current, the control module pulse width modulating the transistors based on the measured DC bus current.
-
6. The control system of claim 5 wherein the current measurement device includes a resistor connected in series with a negative rail of the voltage source, the control module pulse width modulating the transistors based on a voltage drop across the resistor.
-
7. The control system of claim 1 wherein the motor is a three-phase DC motor.
-
8. The control system of claim 7 wherein the DC motor is a brushless motor.
-
9. An inverter for a motor control system, the inverter comprising:
-
a plurality of transistors;
a control module for selectively enabling the transistors such that each phase of the motor has a phase turn on point that occurs before a phase turn off point of a preceding phase, wherein said control module pulse width modulates the transistors such that the DC bus current is regulated to a fixed current level, wherein the control module defines alternating overlapping periods and non-overlapping periods and delivers the fixed current level to one of the phases during the non-overlapping periods, and wherein the control module supplies a decreasing current level to a first phase and an increasing current level to a second phase during an overlapping period such that said first and second phases share the fixed current level and a sum of current that is supplied to said first phase and said second phase is substantially equal to said fixed current level. - View Dependent Claims (10, 11)
-
-
12. A method for controlling a motor including a plurality of phases, comprising:
-
providing a DC bus current;
regulating the DC bus current to a fixed current level;
defining alternating overlapping periods and non-overlapping periods;
delivering the fixed current level to one of the phases during the non-overlapping periods; and
supplying a decreasing current level to a first phase and an increasing current level to a second phase during an overlapping period such that said first and second phases share the fixed current level and a sum of current that is supplied to said first phase and said second phase is substantially equal to said fixed current level. - View Dependent Claims (13, 14, 15, 16)
measuring the DC bus current; and
comparing the measured DC bus current to the fixed level.
-
-
16. The method of claim 15 further including the step of measuring a voltage drop across a resistor in series with a negative rail of the DC bus.
Specification