Abstract: A control circuit is provided for regulating the rotational speed of a brushless DC motor by pulse width modulating at least one power transistor to pass a motor supply signal to the motor armature. A voltage averaging circuit generates an averaged signal indicative of the average voltage level being supplied to the motor. The averaged voltage signal is compared against a reference voltage to determine motor speed error in order to maintain the rotational speed of the motor at a generally constant level. A sawtooth or other periodic ramp signal is added to a motor current signal, and this composite signal is monitored by a comparator until it overcomes the motor speed error signal. The pwm circuit thereby modulates the power supply to regulate motor speed while maintaining a symmetrical motor armature current waveform.

Abstract: A control circuit is provided for regulating the rotational speed of a brushless DC motor by pulse width modulating at least one power transistor to pass a motor supply signal to the motor armature. A voltage averaging circuit generates an averaged signal indicative of the average voltage level being supplied to the motor. The averaged voltage signal is compared against a reference voltage to determine motor speed error in order to maintain the rotational speed of the motor at a generally constant level. A sawtooth or other periodic ramp signal is added to a motor current signal, and this composite signal is monitored by a comparator until it overcomes the motor speed error signal. The pwm circuit thereby modulates the power supply to regulate motor speed while maintaining a symmetrical motor armature current waveform.

Abstract: A control circuit is provided for regulating the rotational speed of a brushless DC motor by pulse width modulating at least one power transistor to pass a motor supply signal to the motor armature. A voltage averaging circuit generates an averaged signal indicative of the average voltage level being supplied to the motor. The averaged voltage signal is compared against a reference voltage to determine motor speed error in order to maintain the rotational speed of the motor at a generally constant level. A sawtooth or other periodic ramp signal is added to a motor current signal, and this composite signal is monitored by a comparator until it overcomes the motor speed error signal. The pwm circuit thereby modulates the power supply to regulate motor speed while maintaining a symmetrical motor armature current waveform.

Abstract: A control circuit for a pulse width modulation (PWM) driven electric motor is provided for operating a fan or motor at a full duty cycle in the event that the PWM input signal should malfunction or fail. The control circuit includes a pulse width modulation (PWM) source having an output; a switch having a control and being coupled between a voltage source and the motor; a capacitor having an input coupled to the PWM output and an output coupled to the switch control, and a diode coupled between the PWM output and the switch control for maintaining the output of the capacitor at a predetermined minimum voltage level. In response to a substantially direct voltage level at the PWM output indicative of a failure of the PWM source, the capacitor maintains at its output a voltage level sufficient to cause the switch control to connect the voltage source to an input of the electric motor and drive the electric motor at a full duty-cycle. The diode provides d.c.

Abstract: A control circuit for regulating the rotational speed of a DC brushless motor includes an electrical conduction switch having an input, an output and a control terminal for passing a motor supply signal to a DC brushless motor. A voltage averaging circuit generates an averaged signal indicative of the average voltage level being supplied to the motor. The averaging circuit informs an error amplifier to modulate the motor supply signal to compensate for changes in the voltage level of the motor supply signal in order to maintain the rotational speed of the motor at a generally constant rpm. The control circuit takes advantage of the motor windings and rotor mass as a filter circuit to smooth changes in current drawn by the motor, and to further maintain the rotational speed of the motor.

Abstract: A phase regulated power supply is provided for converting alternating current (AC) to direct current (DC) for powering a DC brushless motor, such as a fan. The power supply includes a full wave bridge rectifier and a driver circuit, which may be an IC chip, controlled by standard commutation circuitry. An output capacitor is connected electrically downstream to the switch for supplying a reduced DC ripple voltage to the motor load. The power supply preferably includes a line filter for removing input power surges. The speed of the motor may be varied by changing the values of bias resistors used with the driver circuit.