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In a motor control system for a DC motor, a modulation circuit provides a plurality of pulse width modulated signals to control the current applied to the motor. The motor is coupled to a current sensing resistor and a plurality of switches responsive to the pulse width modulated control signals. Th

In a motor control system for a DC motor, a modulation circuit provides a plurality of pulse width modulated signals to control the current applied to the motor. The motor is coupled to a current sensing resistor and a plurality of switches responsive to the pulse width modulated control signals. The output of the current sensing resistor is summed with an input current command to provide an error signal. A modulation circuit which includes a waveform generator generates a plurality of interposed triangular waves adjustably offset by a predetermined amount. The triangular waves are compared to the error signal to provide pulse width modulated control signals which cause a "dither" current to be applied to the motor when there is substantially no input command and currents having substantially decreasing form factors to be applied as the input command increases.

대표청구항 ▼

1. A system for energizing a DC load, which comprises: a load circuit including the load, said load circuit being inductive and having a plurality of switches responsive to pulse width modulated control signals for applying a current to the load; means for generating at least a first pair of tria

1. A system for energizing a DC load, which comprises: a load circuit including the load, said load circuit being inductive and having a plurality of switches responsive to pulse width modulated control signals for applying a current to the load; means for generating at least a first pair of triangular waves, said first pair of triangular waves being adjustably offset from a baseline and each other by an amount proportional to the absolute value of the load current; means for generating at least one triangular wave which is interposed between said first pair of triangular waves and which has a fixed offset from the baseline; means for comparing the triangular waves to a signal indicative of the difference between a desired current and the actual load current, thereby generating pulse width modulated control signals which apply a dithered current to the load when the desired current is relatively low and a current having a substantially decreasing form factor as the desired current is increased. 2. The system according to claim 1 wherein said load is a DC motor and providing the inductance of said inductive load. 3. The system according to claim 2 wherein said load is a DC motor and said load circuit includes a separate inductor. 4. The system according to claim 1 wherein said means for generating at least one triangular wave generates two triangular waves having a fixed offset. 5. The system according to claim 4 wherein the comparator means includes time delay means for preventing the pulse width modulated control signals from simultaneously turning on switches of said load circuit which are coupled between a power supply and ground. 6. The system according to claim 5 which further includes logic means for inhibiting the flow of current. 7. The system according to claim 6 wherein the load circuit includes a DC motor connected to the switches in a bridge circuit configuration. 8. The system according to claim 7 wherein the load circuit further includes a current sensing resistor for providing a signal representative of the actual load current. 9. The system according to claim 8 which further includes a summing junction for comparing the actual load current signal to the desired current signal, thereby providing an error signal representative of the difference therebetween. 10. The system according to claim 1 wherein the load circuit includes a DC motor connected to bipolar transistors in a bridge circuit configuration. 11. The system according to claim 1 wherein the load circuit includes a DC motor connected to field effect transistors in a bridge circuit configuration.