Circuit and method for speed monitoring of an electric motor
View Patent ↗A method for determining a phase angle between voltage applied to a winding of the electric motor and an electric current flowing through the winding may include receiving a signal from the electric motor, including a value of a voltage applied to a winding of the electric motor. The method may also include determining a value of an electric current flowing through the winding and determining a phase angle between the voltage applied to the winding and the electric current flowing through the winding. The method may also include determining a speed or a stall state of the electric motor.
1. A circuit for monitoring of an electric motor, wherein the circuit comprises:
a power control circuit including a transistor with a transistor output, the transistor output configured to apply a voltage to a winding input of a winding of the electric motor, and the transistor configured to operate in a free-wheeling mode to cause the winding input to receive an electric current traversing the winding to provide a free-wheeling current circle through the winding;
a circuit for receiving a signal from the power control circuit, wherein the signal indicates a value of a voltage applied to the winding input of the winding of the electric motor by the power control circuit;
a circuit for receiving a value of the electric current traversing the winding, wherein the value of the electric current is determined from an electric coupling to the winding output;
a circuit for determining a phase angle between the voltage applied to the winding input of the winding and the value of the electric current traversing the winding; and
a circuit for outputting and evaluating the phase angle.
2. The circuit of claim 1 , wherein the signal is received from a chopper driver circuit for the electric motor.
3. The circuit of claim 1 , wherein the value of the voltage is a value of a peak voltage and wherein the value of the electric current is a value of a peak current.
4. The circuit of claim 1 , wherein the circuit for determining the phase angle is for determining the phase angle based upon a delay between zero crossings of the voltage and the electric current.
5. The circuit of claim 1 , wherein the circuit for monitoring of the electric motor is for detecting a stall state of the electric motor.
6. The circuit of claim 1 , wherein the circuit for monitoring of the electric motor is for determining a speed of the electric motor.
7. The circuit of claim 1 , wherein the circuit for monitoring of the electric motor for determining the phase angle is for determining the phase angle continuously.
8. A system comprising:
an electric motor having a winding with a winding input and a winding output, wherein a transistor output of a power control circuit is coupled to the winding input and the winding input is configured to receive an electric current traversing the winding via the winding output to provide a free-wheeling current circle through the winding; and
a motor control unit comprising:
a circuit for receiving a signal from the power control circuit, wherein the signal indicates a value of a voltage applied to a winding of the electric motor;
a circuit for receiving a value of the electric current traversing the winding, wherein the value of the electric current is determined from an electric coupling to the winding output;
a circuit for determining a phase angle between the voltage applied to the winding and the value of the electric current traversing the winding; and
a circuit for outputting and evaluating the phase angle.
9. The system of claim 8 , wherein the electric motor comprises a DC stepper motor.
10. The system of claim 8 , wherein the motor control unit comprises an on-chip motor controller or a dedicated motor controller.
11. A method for monitoring of an electric motor, the method comprising the following steps:
receiving a signal from the electric motor, wherein the signal indicates a value of a voltage applied to a winding of the electric motor;
determining a value of an electric current flowing through the winding; and
determining a phase angle between the voltage applied to the winding and the electric current flowing through the winding;
generating a time-frame signal that indicates when a time-frame of predefined length changes from an inactive state of counting chopper pulses to an active state of counting chopper pulses, and which indicates when the time-frame changes back from the active state to the inactive state;
receiving another signal from a chopper driver circuit controlling the electric motor;
detecting chopper pulses in the another signal;
counting the detected chopper pulses while the active state is indicated; and
at least one of outputting and evaluating a count value, after the inactive state of the time-frame has been indicated.
12. The method of claim 11 , wherein the receiving comprises receiving the signal from a chopper driver circuit driving the electric motor.
13. The method of claim 11 , wherein the value of the voltage is a value of a peak voltage and wherein the value of the electric current is a value of a peak current.
14. The method of claim 11 , wherein determining the phase angle comprises determining the phase angle based upon a delay between zero crossings of the voltage and the electric current.
15. The method of claim 11 , further comprising determining a speed of the electric motor.
16. The method of claim 11 , further comprising determining a stall state of the electric motor.
17. The method of claim 11 , further comprising generating the voltage applied to the winding of the electric motor by providing pulse-width modulation (PWM) signals.
18. The method of claim 17 , further comprising microstepping the electric motor.
19. The method of claim 11 , wherein the determining the phase angle comprises continuously determining the phase angle.