Sensorless trapezoidal motor control
A method includes receiving a first measurement signal representing a first time between transitions of a motor commutation state. The method further includes receiving a second measurement signal representing a second time between transitions of a motor floating terminal voltage. The method further includes determining a motor speed state based on a combination of the first and second measurement signals, determining a motor commutation state based on the motor speed state and the motor floating terminal voltage; and providing a control signal to a motor inverter based on the motor commutations state.
1 . An apparatus comprising:
a time measurement circuit having a first voltage transition input, a commutation state input, a first time measurement output, and a second time measurement output;
a motor commutation controller having a signal measurement input, a second voltage transition input, a speed state input, and a commutation state output, the second voltage transition input coupled to the first voltage transition input, the commutation state output coupled to the commutation state input;
a motor speed circuit having a first time measurement input, a second time measurement input, and a speed state output, the first time measurement input coupled to the first time measurement output, the second time measurement input coupled to the second time measurement output, and the speed state output coupled to the speed state input; and
a motor inverter driver circuit having a motor control input coupled to the commutation state output of the motor commutation controller.
2 . The apparatus of claim 1 , further comprising a voltage processing circuit having voltage processing inputs, a control input, a first motor voltage output, and a second motor voltage output, wherein the motor inverter driver circuit has motor control outputs coupled to the voltage processing inputs, and wherein at least one of the first motor voltage output or the second motor voltage output is coupled to the signal measurement input of the motor commutation controller.
3 . The apparatus of claim 2 , wherein the voltage processing circuit includes:
a voltage multiplexer circuit having multiplexer inputs, a selection input, and a multiplexor output, the multiplexer inputs coupled to the voltage processing inputs, the selection input coupled to the control input, and the multiplexor output coupled to the first motor voltage output; and
a voltage summation circuit having summation inputs and a summation output, the summation inputs coupled to the voltage processing inputs, and the summation output coupled to the second motor voltage output.
4 . The apparatus of claim 2 , further comprising a comparator having a first comparator input, a second comparator input, and a comparator output, the first comparator input coupled to the first motor voltage output, the second comparator input coupled to the second motor voltage output, and the comparator output coupled to the first voltage transition input and the second voltage transition input.
5 . The apparatus of claim 2 , further comprising an analog-to-digital converter (ADC) having an ADC input and an ADC output, the ADC output coupled to the signal measurement input of the motor commutation controller, and the ADC input coupled to at least one of the first motor voltage output, the second motor voltage output, the voltage processing inputs, or a motor current sensing terminal coupled to the motor inverter driver circuit.
6 . The apparatus of claim 1 , wherein the motor commutation controller includes a is configured to:
responsive to a first speed state received at the speed state input, determine a commutation state based on a first signal at the signal measurement input;
responsive to a second speed state received at the speed state input, determine the commutation state based on a second signal at the second voltage transition input; and
provide an indication of the commutation state at the commutation state output.
7 . The apparatus of claim 6 , wherein the communication state is a first commutation state, the motor commutation controller is configured to transition between commutation states, the commutation states include the first commutation state and at least a second commutations state, and the motor commutation controller is configured to:
withhold transition from the first commutation state to the second commutation state within a blanking window that begins at an end of the first commutation state; and
transition from the first commutation state to the second commutation state after expiration of the blanking window.
8 . The apparatus of claim 7 , wherein:
the motor commutation controller is configured to receive a current measurement signal at the signal measurement input and adjust the blanking window based on the current measurement signal.
9 . The apparatus of claim 7 , wherein the motor commutation controller has a blanking time output, and the motor speed circuit has a blanking time input, the motor commutation controller configured to provide a timing signal representing a start time and a duration of a blanking timing window at the blanking time output, and the motor speed circuit is configured to withhold transition to a next speed state within the blanking timing window responsive to the timing signal.
10 . The apparatus of claim 1 , wherein the time measurement circuit includes:
a first counter having a first counter control input and a first counter output, the first counter control input coupled to the first voltage transition input, and the first counter output coupled to the first time measurement output; and
a second counter having a second counter control input and a second counter output, the second counter control input coupled to the commutation state input, and the second counter output coupled to the second time measurement output.
11 . The apparatus of claim 10 , wherein the motor speed circuit has multiple speed states including a first speed state and a second speed state, and the motor speed circuit is configured to:
transition between the first speed state and the second speed state based on a combination of a first signal at the first time measurement input and a second signal at the second time measurement input; and
provide an indication of the first or second speed state at the speed state output.
12 . The apparatus of claim 11 , wherein the first speed state is associated with a first speed range, the second speed state is associated with a second speed range, and the second speed range has larger maximum and minimum magnitudes than the first speed range.
13 . The apparatus of claim 12 , wherein the multiple speed states include an idle state and an initial position detection (IPD) state, and the first speed range starts at zero.
14 . The apparatus of claim 13 , wherein the motor speed circuit has a trigger input and is configured to transition from the idle state to the IPD state responsive to a state of the trigger input.
15 . The apparatus of claim 14 , wherein the motor speed circuit includes a de-glitch circuit coupled to the trigger input, and the motor speed circuit is configured to transition from the idle state to the IPD state responsive to a state of an output of the de-glitch circuit.
16 . The apparatus of claim 14 , wherein the motor speed circuit has a current sensing input and is configured to transition from the IPD state back to the idle state responsive to a current measurement signal at the current sensing input exceeding a threshold.
17 . The apparatus of claim 12 , wherein the motor speed circuit has a motor speed output, and the motor speed circuit is configured to:
in the first speed state, provide a motor speed signal at the motor speed output based on the second signal at the second time measurement input; and
in the second speed state, provide the motor speed signal at the motor speed output based on the first signal at the first time measurement input.
18 . The apparatus of claim 17 , wherein the combination of the first signal and the second signal is a combination of a scaled version of the first signal and a scaled version of the second signal, in which the first signal is scaled by a first scaling factor and the second signal is scaled by a second scaling factor.
19 . The apparatus of claim 18 , wherein the multiple speed states include a third speed state associated with a third speed range, the third speed range being between the first and second speed ranges.
20 . The apparatus of claim 19 , wherein the motor speed circuit is configured to exit the first speed state and enter the third speed state responsive to the combination exceeding a first threshold.
21 . The apparatus of claim 20 , wherein the motor speed circuit is configured to exit the first speed state and enter the third speed state responsive to the motor speed circuit having been in the first speed state for a number of motor rotation cycles exceeding a second threshold.
22 . The apparatus of claim 20 , wherein the motor speed circuit is configured to exit the second speed state and enter the third speed state responsive to the combination being below a threshold, in which the second scaling factor is zero.
23 . The apparatus of claim 17 , wherein the motor inverter driver circuit includes a motor speed controller and a pulse width modulation (PWM) controller, the motor speed controller having a first speed input, a reference speed input, and a speed control output, the PWM controller having a PWM input and a PWM output, the first speed input coupled to the motor speed output, and the PWM input coupled to the motor control input and the commutation state output,
wherein the motor inverter driver circuit further includes an inverter driver having an inverter driver input coupled to the PWM output.