Electricity: motor control systems – Closed loop speed control system for dc motor with commutator – Field control – or field and armature control – by analog...
Reexamination Certificate
1999-02-08
2001-03-13
Nappi, Robert E. (Department: 2837)
Electricity: motor control systems
Closed loop speed control system for dc motor with commutator
Field control, or field and armature control, by analog...
C388S827000, C318S268000
Reexamination Certificate
active
06201929
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a multistage rotating speed control circuit for a DC motor.
Concerning the rotating speed control of a DC motor, there are two kinds of control circuits: (1) the first kind of control circuit can provide only fixed rotating speed of a DC motor; (2) the second kind of control circuit can provide multistage rotating speed of a DC motor. Since the rotating speed of a DC motor cannot be adjusted using the former control circuit, an additional speed change device is necessary to enable multistage rotating speed of a DC motor, which is not convenient. On the other hand, the latter utilizes the 8255A interface circuit used in the 8-bit microprocessor 8085A and Z80 to achieve the function of multistage rotating speed control of a DC motor, which requires complicated circuitry and high cost.
FIG. 1
is a block diagram showing the digital rotating speed control circuit for a DC motor of the U.S. patent application. Ser. No. 08/988,051, wherein a digital circuit is used to control the rotating speed of a DC motor. The digital circuit receives an input digital signal set (CONl~CONn) which can be generated by, for example, a microcomputer accompanied with an A/D interface card. However, it requires high cost because the system is complicated.
In view of the above, the purpose of the present invention is to provide a circuit composed of simple electric elements, by which an input digital signal set (CONl~CONn) for a digital control circuit can be generated.
SUMMARY OF THE INVENTION
In order to solve the aforementioned problem, the present invention provides a simple and low cost circuit with a small volume, by which multistage rotating speed control for a DC motor is possible.
In accordance with the first aspect of the present invention, there is provided a multistage rotating speed control circuit of a DC motor which is connected between a positive and a negative DC supply voltages and controls the rotating speed of the motor, comprising: a digital control circuit which receives a digital signal set and delivers a corresponding current based on the digital signal set; and a driving circuit connected to the digital control circuit, which controls the rotating speed of the DC motor based on the output current of the digital control circuit. It is characterized by further comprising: an input voltage modifying circuit which delivers an output voltage; a reference voltage generating circuit which provides a fixed number of reference voltage; and a comparing circuit consisting of the fixed number of comparators, each of which receives the output voltage from the input voltage modifying circuit at its first end and a different reference voltage generated by the reference voltage generating circuit at its second end, and delivers an output digital signal based on the comparison result of the two input signals, these output digital signals collectively making up an input digital signal set of the digital control circuit.
The second aspect of the present invention is directed to the multistage rotating speed control circuit for a DC motor according to the first aspect of the invention, wherein the input voltage modifying circuit comprises: a fixed resistor with the first terminal connected to the positive DC supply voltage; and a variable resistor wherein the first terminal, which is the output terminal of the input voltage modifying circuit, is connected to the second terminal of the fixed resistor and its second terminal is connected to the negative DC supply voltage.
The third aspect of the invention is directed to the multistage rotating speed control circuit for a DC motor according to the first aspect of the invention, wherein the input voltage modifying circuit is composed of an external voltage source.
The fourth aspect of the invention is directed to the multistage rotating speed control circuit for a DC motor according the first aspect of the invention, wherein the reference voltage generating circuit comprises: a first resistor set consisting of the fixed number of resistors wherein the first terminal of each resistor is connected to the positive DC supply voltage; and a second resistor set consisting of the fixed number of resistors wherein the first terminal of each resistor is connected to the second terminal of a different one of the first resistor set and its second terminal is connected to the negative DC supply voltage.
The fifth aspect of the invention is directed to the multistage rotating speed control circuit for a DC motor according the first aspect of the invention, wherein the reference voltage generating circuit is composed of a plurality of external voltage sources.
REFERENCES:
patent: 4250437 (1981-02-01), Morton et al.
patent: 4771845 (1988-09-01), Shimizu
patent: 5197858 (1993-03-01), Cheng
patent: 5525881 (1996-06-01), Desrus
patent: 5818379 (1998-10-01), Kim
patent: 5880678 (1999-03-01), Yu
patent: 5929581 (1999-07-01), Brocklin et al.
patent: 6002356 (1999-12-01), Cooper
Delta Electronics , Inc.
Duda Rina I.
Nappi Robert E.
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