DC motor speed control system
AssigneeBriggs & Stratton Corporation
InventorsRichard A. Dykstra, Robert K. Mitchell
Life of this patent
Estimating the term…
Abstract
A speed controller for a DC motor minimizes speed droop and load droop through pulse width or frequency modulation. The controller provides an extra power increase upon engine starting or whenever a heavier load is temporarily encountered. The control circuit also has a current limiter, overload indicators, and a battery recharger. The controller is very inexpensive, primarily because all of the timing components are contained on a single integrated circuit timer chip such as a 556 timer. The controller contains other features, including a circuit for limiting the pulse width of the control signal from the pulse width modulator.
Claims50
A control system for controlling an electric motor in lawn or garden equipment, said electric motor being interconnected with a load, said motor drawing current from and being powered by a battery that outputs a supply signal, said supply signal continuously decreasing as said battery discharges, comprising:
- means for generating a frequency signal at a predetermined frequency;
- means for generating a supply feedback signal functionally related to said supply signal;
- means for sensing the current being drawn by said motor;
- means for generating a load feedback signal functionally related to the magnitude of said sensed motor current;
- pulse width modulation means for receiving said frequency signal, said supply feedback signal, and said load feedback signal, and for outputting a switch control signal at said predetermined frequency whose pulse width is both inversely proportional to said supply signal and directly proportional to the magnitude of said sensed motor current;
- switch means for switching current to said motor in response to said switch control signal;
- and
- means for increasing the power to said motor when the sensed motor current is greater than a predetermined level.
A control system for controlling an electric motor in lawn or garden equipment, said electric motor being interconnected with a load, said motor drawing current from and being powered by a battery that outputs a supply signal, said supply signal continuously decreasing as said battery discharges, said control system comprising:
- means for generating a frequency signal;
- means for generating a supply feedback signal functionally related to said supply signal;
- means for sensing the current being drawn by said motor;
- means for generating a load feedback signal functionally related to the magnitude of said sensed motor current;
- frequency modulation means for receiving said frequency signal, said supply feedback signal, and said load feedback signal, and for outputting a switch control signal having a set pulse width whose frequency is both inversely proportional to said supply signal and directly proportional to the magnitude of said sensed motor current;
- switch means for switching current to said motor in response to said switch control signal;
- and
- means for increasing the power to said motor when the sensed motor current is greater than a predetermined level.
A control system for controlling an electric motor in lawn or garden equipment, said motor being interconnected with a load, said motor drawing current from and being powered by a battery that outputs a supply signal, said supply signal continuously decreasing as said battery discharges, said control system comprising:
- means for generating a supply feedback signal functionally related to said supply signal;
- means for sensing the current being drawn by said motor;
- means for generating a load feedback signal functionally related to the magnitude of said sensed motor current;
- a timer means, including:
- means for generating a frequency signal at a predetermined frequency;
- pulse width modulation means for receiving said frequency signal, said supply feedback signal, and said load feedback signal, and for outputting a switch control signal at said predetermined frequency whose pulse width is both inversely proportional to said supply signal and directly proportional to the magnitude of said sensed motor current;
- and
- switch means for switching current to said motor in response to said switch control signal.
A control system for controlling an electric motor in lawn or garden equipment, said motor being interconnected with a load, said motor drawing current from and being powered by a battery that outputs a supply signal, said supply signal continuously decreasing as said battery discharges, said control system comprising:
- means for generating a supply feedback signal functionally related to said supply signal;
- means for sensing the current being drawn by said motor;
- means for generating a load feedback signal functionally related to the magnitude of said sensed motor current;
- a timer means, including:
- means for generating a frequency signal;
- frequency modulation means for receiving said frequency signal, said supply feedback signal, and said load feedback signal, and for outputting a switch control signal having a set pulse width whose frequency is both inversely proportional to said supply signal and directly proportional to the magnitude of said sensed motor current;
- and
- switch means for switching current to said motor in response to said switch control signal.
Dependencies are inferred from the claim text.