Circuits and methods for driving eccentric rotating mass motors

A method for operating an Eccentric Rotating Mass (“ERM”) motor, the method comprising:

• operating, with a controller, a driver circuit for the motor in a closed loop mode when a back electromechanical force (EMF) signal from the motor is less than a lower threshold value and a difference between a value of an input signal and the back EMF signal is positive;
• operating, with the controller, the driver circuit in an open loop mode when the back EMF signal is greater than a higher threshold value and the difference between the value of the input signal and the back EMF signal is positive;
• operating, with the controller, the driver circuit in a previous one of the open loop and closed loop modes when the back EMF signal is between the higher and lower threshold values and the difference between the value of the input signal and the back EMF signal is positive;
• operating, with the controller, the driver circuit in the closed loop mode when the difference between the value of the input signal and the back EMF signal is negative;
• and
• wherein the driver circuit includes a summer circuit coupled between an input terminal of the driver circuit and an input of a driver, a feedback amplifier having an input coupled to an output of the driver, a first switch coupled between a first input of the summer circuit and an output of the summer circuit, and a second switch coupled between an output of the feedback amplifier and a second input of the summer circuit, wherein operating the driver circuit in the closed loop mode includes opening the first switch and closing the second switch, and wherein operating the driver circuit in the open loop mode includes closing the first switch and opening the second switch.

A circuit for driving an Eccentric Rotating Mass (“ERM”) motor, the circuit comprising:

• an input terminal;
• a driver having an input and an output;
• a feedback amplifier having an input coupled to the output of the driver, and an output;
• a summer circuit having first and second inputs, the first input coupled to the input terminal, the summer circuit further having an output coupled to the input of the driver;
• a first switch having a first terminal coupled to the first input of the summer circuit, and a second terminal coupled to the output of the summer circuit;
• a second switch having a first terminal coupled to the output of the feedback amplifier, and a second terminal coupled to the second input of the summer circuit;
• and
• a controller having a first input coupled to the output of the driver, a second input coupled to the input terminal, and an output coupled to respective control inputs of the first and second switches.