Motor controller
First Claim
Patent Images
1. A control circuit to control a speed of a motor, comprising:
- a PWM oscillator configured to generate a PWM output signal having a duty cycle, wherein the speed of the motor is controlled by the PWM output signal to be proportional to the duty cycle; and
a duty cycle control circuit responsive to a duty cycle selection signal and coupled to the PWM oscillator, the duty cycle control circuit being configured to compare a voltage reference and a supply voltage,wherein the duty cycle control circuit controls the duty cycle of the PWM output signal to be inversely proportional to the supply voltage, andwherein the speed of the motor is substantially constant with respect to variations in the supply voltage.
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Abstract
In one aspect, a control circuit to control a speed of a motor includes a PWM oscillator configured to generate a PWM output signal having a duty cycle. The speed of the motor is controlled by the PWM output signal to be proportional to the duty cycle. The control circuit also includes a duty cycle control circuit responsive to a duty cycle selection signal and coupled to the PWM oscillator. The duty cycle control circuit is configured to compare a voltage reference and a supply voltage. The duty cycle control circuit controls the duty cycle of the PWM output signal to be inversely proportional to the supply voltage.
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Citations
25 Claims
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1. A control circuit to control a speed of a motor, comprising:
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a PWM oscillator configured to generate a PWM output signal having a duty cycle, wherein the speed of the motor is controlled by the PWM output signal to be proportional to the duty cycle; and a duty cycle control circuit responsive to a duty cycle selection signal and coupled to the PWM oscillator, the duty cycle control circuit being configured to compare a voltage reference and a supply voltage, wherein the duty cycle control circuit controls the duty cycle of the PWM output signal to be inversely proportional to the supply voltage, and wherein the speed of the motor is substantially constant with respect to variations in the supply voltage. - View Dependent Claims (2, 3, 4, 5)
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6. A control circuit to control a speed of a motor, comprising:
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a timer configured to measure from a first time based on an activation signal and to provide an enable signal based on the timer reaching a second time, wherein the second time occurs after a predetermined amount of time has elapsed following the first time; and a PWM sequencer responsive to a duty cycle selection signal and configured to generate a PWM output signal having a duty cycle, wherein the speed of the motor is controlled by the PWM output signal to be proportional to the duty cycle, wherein the PWM output signal is generated in response to the enable signal and the duty cycle selection signal. - View Dependent Claims (7, 8, 9, 10, 11)
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12. A control circuit configured to control a speed of a motor, comprising:
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comparator circuitry configured to evaluate a rotor commutation signal having a frequency proportional to the speed of the motor using a clock reference signal having a fixed frequency and to provide an enable signal in response to the evaluation; and a PWM sequencer configured to generate a PWM output signal having a duty cycle, wherein the speed of the motor is controlled by the PWM output signal to be proportional to the duty cycle, and wherein the PWM output signal is determined by the duty cycle selection signal in response to a transition of the enable signal. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A control circuit to control a speed of a motor, comprising:
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speed detection circuitry to detect the speed of the motor, comprising; comparator circuitry configured to receive a clock reference signal having a fixed frequency and a rotor commutation signal having a frequency proportional to the speed of the motor and to provide a brake enable signal in response to the speed of the motor being below a predetermined threshold; and power control circuitry configured to place transistors in an H-bridge circuit in an off state based on the brake enable signal. - View Dependent Claims (23, 24, 25)
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Specification