Cyclic speed motor control circuit
First Claim
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1. A motor control circuit for controlling the supply of electrical power to a motor, said circuit comprising:
- a source of electrical power;
switching circuit means for connecting said source and the motor to form a complete electrical path for the supply of power to the motor, said switching circuit means comprising means for controlling the speed of operation of the motor;
a control circuit for generating a control signal coupled to said switching circuit means, wherein the speed of the motor is controlled by said switching circuit means in response to the value of said control signal, and wherein said control circuit automatically changes said control signal alternately and continuously between one value and another to operate the motor alternately at a first speed and at a second speed lower than said first speed, for thereby providing intermittent speed changes to the motor; and
means for detecting the occurrence of a motor current overload and the occurrence of resultant ripple current, and means responsive to detection of said ripple current for inhibiting said switching circuit means from forming said complete electrical path.
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Abstract
A motor control circuit comprising a switching circuit which controls the supply of power from a source thereof to a motor responsive to a control signal, and a speed control circuit which generates the control signal. The speed control circuit can vary the motor speed cyclically, operating as an stable multi-vibrator. An overload protection circuit detects the occurrence of a current overload condition and either reduces to a low level the power delivered to the motor or inhibits the switching circuit'"'"'s operation altogether.
23 Citations
13 Claims
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1. A motor control circuit for controlling the supply of electrical power to a motor, said circuit comprising:
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a source of electrical power; switching circuit means for connecting said source and the motor to form a complete electrical path for the supply of power to the motor, said switching circuit means comprising means for controlling the speed of operation of the motor; a control circuit for generating a control signal coupled to said switching circuit means, wherein the speed of the motor is controlled by said switching circuit means in response to the value of said control signal, and wherein said control circuit automatically changes said control signal alternately and continuously between one value and another to operate the motor alternately at a first speed and at a second speed lower than said first speed, for thereby providing intermittent speed changes to the motor; and means for detecting the occurrence of a motor current overload and the occurrence of resultant ripple current, and means responsive to detection of said ripple current for inhibiting said switching circuit means from forming said complete electrical path. - View Dependent Claims (2, 3, 4, 5)
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6. A motor control circuit for supplying power to a motor, said circuit comprising:
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a source of electrical power; switching circuit means for alternatingly completing and breaking an electrical circuit including said source and the motor to apply electrical power from said source to the motor, and to interrupt the supply of electrical power from said source to the motor, said switching circuit means controlling the application of power to the motor responsive to a first control signal; and speed control circuit means for generating the first control signal for controlling said switching circuit means, said speed control circuit means being operable in a first mode, in which said speed control circuit means generates the first control signal to have first and second time-dependent driving values for providing intermittent speed changes to the motor, thereby continuously driving said motor alternately at two different speeds. - View Dependent Claims (7, 8, 9, 10, 11, 12)
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13. A motor control circuit for controlling the supply of electrical power to a motor, said circuit comprising:
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a source of electrical power; switching circuit means for alternatingly connecting said source to the motor for completing an electrical path to supply electrical power from said source to the motor, and interrupting said electrical path to interrupt the supply of power to the motor; a speed control circuit for generating a control signal to control said switching circuit means to control the supply of power to the motor; and a current overload protection circuit comprising means for detecting when the motor is overloaded and for causing said switching circuit means, responsive to detection of the overload, to reduce the electric power being applied to the motor, said current overload protection circuit means comprising means for detecting and rectifying a ripple voltage and for inhibiting, responsive to said rectified ripple voltage exceeding a predetermined level, said switching circuit means from completing said electrical path.
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Specification