Electric motor speed controller and method

Claim 1

A direct current electric motor speed controller circuit between the motor and a power supply sufficient to drive the motor which controller consists essentially of: (a) at least one power transistor connected through its emitter and collector in series between the motor and the power supply to form a power circuit such that current flows between the power supply and the motor through the transistor only when a signal current is supplied to the base of the transistor; (b) a speed control which provides a variable resistance, inductance or capacitance within a control circuit; (c) a control circuit having a power requirement substantially lower than the power requirement to operate the motor, said control circuit supplying pulses of a pulse width modulated signal current to the base of the power transistor, the width of the pulse being proportional to the value of the variable resistance, inductance or capacitance of the speed control, said control circuit comprising: (i) means for generating a constant frequency saw toothed electrical voltage wave form biased so that the lowest voltage of the wave is greater than zero; (ii) a means for generating a voltage proportional to the variable resistance, inductance or capacitance; and (iii) a means for comparing the voltage of the saw toothed wave form with the generated proportional voltage and for outputting a direct current pulse width modulated signal to the base of the power transistor when the generated proportional voltage is greater than the voltage of the electrical wave form, the width of the pulses of said pulse width modulated signal being directly proportional to the generated proportional voltage; (d) means for stopping available signal currents to the base of the power transistor when current through the power circuit is greater than a maximum desired level and for restoring available signal currents when the current through the power circuit is again below the maximum desired level; and (e) means for stopping available signal currents to the base of the power transistor when power supply voltage falls below the desired minimum voltage to drive the motor; the means for generating a constant frequency saw toothed wave, the means for generating a proportional voltage, the means for comparing the voltage of the saw toothed wave form with the proportional voltage, the means for stopping available signal currents to the base of the power transistor when current through the power circuit is greater than a maximum desired level and the means for stopping available signal currents to the base of the power transistor when the power supply voltage falls below the desired minimum voltage to drive the motor each comprising at least a part of at least one integrated circuit.

Claim 13

A method for controlling the speed of a direct current electric motor which consists essentially of: (a) varying a variable resistance, inductance or capacitance of a speed control; (b) providing a constant frequency saw toothed electrical voltage wave form biased so that the lowest voltage of the wave is greater than zero, utilizing at least a part of an integrated circuit; (c) providing a voltage proportional to the value of the variable resistance, inductance or capacitance, utilizing at least a part of an integrated circuit; (d) comparing the voltage of the saw toothed wave form with the voltage proportional to the resistance, inductance or capacitance, utilizing at least a part of an integrated circuit; (e) outputing a direct current pulse width modulated signal when the proportional voltage is greater than the voltage of the electrical voltage wave form; the width of the pulses of said pulse width modulated signal being directly proportional to the generated proportional voltage, utilizing at least a part of an integrated circuit; (f) supplying said pulse width modulated signal current, to the base of at least one power transistor to activate the transistor which is connected by its emitter and collector, as an electrical switch in series between the motor and a power supply; (g) stopping available signal currents to the base of the power transistor when current through the motor is greater than a maximum desired level and for restoring available signal currents when the current through the motor is again below the maximum desired level, utilizing at least a part of an integrated circuit; and (h) stopping available signal currents to the base of the power transistor when battery voltage falls below the desired minimum voltage to drive the motor, utilizing at least a part of an integrated circuit.

Claim 14

A method for controlling the speed of a direct current electric motor which consists essentially of: (a) varying a variable resistance, inductance or capacitance of a speed control; (b) providing a constant frequency saw toothed electrical voltage wave form biased so that the lowest voltage of the wave is greater than zero, utilizing at least a part of an integrated circuit; (c) providing a voltage proportional to the value of the variable resistance, inductance or capacitance, utilizing at least a part of an integrated circuit; (d) comparing the voltage of the saw toothed wave form with the voltage proportional to the resistance, inductance or capacitance, utilizing at least a part of an integrated circuit; (e) outputing a direct current pulse width modulated signal when the proportional voltage is greater than the voltage of the electrical voltage wave form; the width of the pulses of said pulse width modulated signal being directly proportional to the generated proportional voltage, utilizing at least a part of an integrated circuit; (f) supplying said pulse width modulated signal current, to the base of at least one power transistor to activate the transistor which is connected by its emitter and collector, as an electrical switch in series between the motor and a power supply; (g) stopping available signal currents to the base of the power transistor when current through the motor is greater than a maximum desired level and for restoring available signal currents when the current through the motor is again below the maximum desired level, utilizing at least a part of an integrated circuit; and (h) stopping available signal currents to the base of the power transistor when battery voltage falls below the desired minimum voltage to drive the motor, utilizing at least a part of an integrated circuit.