Mutual inductance voltage offset compensation for brushless DC sensorless motors
First Claim
1. A control circuit for controlling operation of a brushless DC (BLDC) sensorless motor having a first terminal connected to a first winding, a second terminal connected to a second winding and a third terminal connected to a third winding, comprising:
- a drive control circuit configured to control the generation of a winding current between the first and second terminals and place the third terminal in a high-impedance state;
wherein the winding current includes a first current at a first non-zero current magnitude and a second current at a second non-zero current magnitude different from the first non-zero current magnitude; and
a differencing circuit comprising;
an amplifier circuit configured to sense a first mutual inductance voltage at the third terminal in response to the first current, said first mutual inductance voltage including a mutual inductance offset voltage component, and sense a second mutual inductance voltage at the third terminal in response to the second current, said second mutual inductance voltage including the same mutual inductance offset voltage component;
a sample and hold circuit coupled to an output of the amplifier circuit to save one of the first and second mutual inductance voltages; and
a comparator circuit having a first input coupled to an output of the sample and hold circuit to receive the saved one of the first and second mutual inductance voltages and a second input coupled to an output of the amplifier circuit to receive the another one of the first and second mutual inductance voltages, said comparator circuit configured to determine a difference between the first and second mutual inductance voltages and produce a difference signal which cancels said mutual inductance offset voltage component.
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Accused Products
Abstract
A control circuit controls the operation of a brushless DC (BLDC) sensorless motor having a first terminal connected to a first winding, a second terminal connected to a second winding and a third terminal connected to a third winding. A driver circuit applies drive signals to the first and second terminals and places the third terminal in a high-impedance state. The drive signals include first drive signals at a first current amplitude and second drive signals at a second, different, current amplitude. A differencing circuit senses a first mutual inductance voltage at the third terminal in response to the first drive signals and senses a second mutual inductance voltage at the third terminal in response to the second drive signals. The differencing circuit further determines a difference between the first and second mutual inductance voltages and produces a difference signal that is used for zero-crossing detection and rotor position sensing.
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Citations
44 Claims
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1. A control circuit for controlling operation of a brushless DC (BLDC) sensorless motor having a first terminal connected to a first winding, a second terminal connected to a second winding and a third terminal connected to a third winding, comprising:
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a drive control circuit configured to control the generation of a winding current between the first and second terminals and place the third terminal in a high-impedance state; wherein the winding current includes a first current at a first non-zero current magnitude and a second current at a second non-zero current magnitude different from the first non-zero current magnitude; and a differencing circuit comprising; an amplifier circuit configured to sense a first mutual inductance voltage at the third terminal in response to the first current, said first mutual inductance voltage including a mutual inductance offset voltage component, and sense a second mutual inductance voltage at the third terminal in response to the second current, said second mutual inductance voltage including the same mutual inductance offset voltage component; a sample and hold circuit coupled to an output of the amplifier circuit to save one of the first and second mutual inductance voltages; and a comparator circuit having a first input coupled to an output of the sample and hold circuit to receive the saved one of the first and second mutual inductance voltages and a second input coupled to an output of the amplifier circuit to receive the another one of the first and second mutual inductance voltages, said comparator circuit configured to determine a difference between the first and second mutual inductance voltages and produce a difference signal which cancels said mutual inductance offset voltage component. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A control circuit for controlling operation of a brushless DC (BLDC) sensorless motor having a first terminal connected to a first winding, a second terminal connected to a second winding and a third terminal connected to a third winding, comprising:
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a drive control circuit configured to control the generation of a winding current between the first and second terminals and place the third terminal in a high-impedance state; wherein the winding current includes a first current at a first non-zero current magnitude and a second current at a second non-zero current magnitude different from the first non-zero current magnitude; and a differencing circuit comprising; an amplifier circuit configured to sense a first mutual inductance voltage at the third terminal in response to the first current, said first mutual inductance voltage including a mutual inductance offset voltage component, and sense a second mutual inductance voltage at the third terminal in response to the second current, said second mutual inductance voltage including the same mutual inductance offset voltage component; an analog to digital converter circuit having an input coupled to an output of the amplifier circuit, said analog to digital converter circuit configured to convert the sensed first and second mutual inductance voltages to digital values; and wherein said drive control circuit comprises a logic circuit configured to process the digital values to produce a difference signal indicative of a difference between the first and second mutual inductance voltages which cancels said mutual inductance offset voltage component. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A control circuit for controlling operation of a brushless DC (BLDC) sensorless motor having a first terminal connected to a first winding, a second terminal connected to a second winding and a third terminal connected to a third winding, comprising:
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a drive control circuit configured to control the generation of a winding current between the first and second terminals and place the third terminal in a high-impedance state; wherein the winding current includes a first current at a first non-zero current magnitude and a second current at a second non-zero current magnitude different from the first non-zero current magnitude; and a differencing circuit comprising; an analog to digital converter circuit having a first input coupled to the third terminal and a second input coupled to a reference signal, said analog to digital converter circuit configured to convert the voltages at the third terminal and reference signal to digital values, wherein the voltages at the third terminal include a first mutual inductance voltage generated in response to the first current, said first mutual inductance voltage including a mutual inductance offset voltage component, and a second mutual inductance voltage generated in response to the second current, said second mutual inductance voltage including the same mutual inductance offset voltage component; and wherein the drive control circuit comprises a logic circuit configured to process the digital values to produce a difference signal which cancels said mutual inductance offset voltage component. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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25. A control circuit for controlling operation of a brushless DC (BLDC) sensorless motor having a first terminal connected to a first winding, a second terminal connected to a second winding and a third terminal connected to a third winding, comprising:
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a drive control circuit configured to control the generation of a winding current between the first and second terminals and place the third terminal in a high-impedance state; wherein the winding current includes a first current at a first non-zero current magnitude and a second current at a second non-zero current magnitude different from the first non-zero current magnitude; and a differencing circuit comprising; a multiplexing circuit having a first input coupled to said third terminal and a second input coupled to a reference signal; an analog to digital converter circuit having an input coupled to an output of the multiplexing circuit, said analog to digital converter circuit configured to convert the voltages at the third terminal and the reference signal to digital values, wherein the voltages at the third terminal include a first mutual inductance voltage generated in response to the first current, said first mutual inductance voltage including a mutual inductance offset voltage component, and a second mutual inductance voltage generated in response to the second current, said second mutual inductance voltage including the same mutual inductance offset voltage component; and wherein the drive control circuit comprises a logic circuit configured to process the digital values to produce a difference signal which cancels said mutual inductance offset voltage component. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32)
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33. A control circuit for controlling operation of a brushless DC (BLDC) sensorless motor having a first terminal connected to a first winding, a second terminal connected to a second winding and a third terminal connected to a third winding, comprising:
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a drive control circuit configured to control the generation of a winding current between the first and second terminals and place the third terminal in a high-impedance state; wherein the winding current includes a first current at a first non-zero current magnitude and a second current at a second non-zero current magnitude different from the first non-zero current magnitude; and a differencing circuit configured to sense a first mutual inductance voltage at the third terminal in response to the first current at the first non-zero current magnitude, said first mutual inductance voltage including a mutual inductance offset voltage component, and sense a second mutual inductance voltage at the third terminal in response to the second current at the second non-zero current magnitude, said second mutual inductance voltage including the same mutual inductance offset voltage component, said differencing circuit further configured to determine a difference between the first and second mutual inductance voltages and produce a difference signal which cancels said mutual inductance offset voltage component. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44)
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Specification