Abstract: An improved self-oscillation system for a linear oscillatory actuator composed of a stator and a reciprocator. The stator carries a winding to which an electric current is periodically supplied for making a resonant oscillation of the reciprocator. The system includes a self-oscillation circuit for continuing the resonant oscillation of the actuator by a positive feedback manner based upon a back electromotive force (Vbemf) appearing across the winding. The system further includes a PWM control for increasing the electric current in response to a decreasing oscillation amplitude due to an increasing load applied to the reciprocator. A detector circuit is included to monitor the oscillation amplitude of the reciprocator and provides a corresponding detector output in response to which the self-oscillation circuit provides a drive pulse of varying pulse width for making the PWM control.

Abstract: Vibrating linear actuator and method of operating same. The actuator of the invention includes a stator, a spring vibration system having a moving portion with a magnet and further having a spring configured to support the moving portion. The actuator further includes an electromagnetic coil configured to receive an electrical current, whereupon the coil moves the moving portion against a load supplied by the spring to reciprocally move the moving portion, a frequency detector configured to detect a natural frequency of the spring vibration system, and a frequency controller configured to determine a frequency of an electrical current pulse, the pulse to be received by the coil, in accordance with a detection result of the detector.

Abstract: A control system for a linear vibration motor capable of eliminating necessity of a separate sensor of detecting the motion of the motor. The linear vibration motor includes a stator provided with a winding, and a vibrator provided with a permanent magnet. The winding is fed with a drive current to generate a magnetic field which interacts with the permanent magnet to cause the vibrator to reciprocate linearly relative to the stator for producing a vibration. The control system includes a controller which detects an ongoing amplitude, i.e., the motion represented by the displacement, speed, or acceleration of the vibrator and provides ON-periods of feeding the driving current to the winding in a varying amount based upon the ongoing amplitude detected in order to keep a vibration amplitude of the vibrator constant.

Abstract: An improved self-oscillation system for a linear oscillatory actuator composed of a stator and a reciprocator. The stator carries a winding to which an electric current is periodically supplied for making a resonant oscillation of the reciprocator. The system includes a self-oscillation circuit for continuing the resonant oscillation of the actuator by a positive feedback manner based upon a back electromotive force (Vbemf) appearing across the winding. The system further includes a PWM control for increasing the electric current in response to a decreasing oscillation amplitude due to an increasing load applied to the reciprocator. A detector circuit is included to monitor the oscillation amplitude of the reciprocator and provides a corresponding detector output in response to which the self-oscillation circuit provides a drive pulse of varying pulse width for making the PWM control.

Abstract: A method for driving a linear oscillating motor and a linear oscillating motor are provided. The motor includes a fixed magnetic member, a movable member having a magnet and being supported to oscillate relative to the fixed magnetic member, a detector that detects displacement of the movable member, and a control that oscillates the movable member by sending drive current to a coil of the fixed magnetic member. The method includes controlling, during a first half-period that occurs within a full amplitude period of the movable member, the drive current based upon the output of the detector. The method also includes controlling, during a second half-period that occurs within a fill amplitude period of the movable member, the drive current based upon a fixed drive current waveform.

Abstract: An actuator driving circuit is provided for a positive feedback amplification, through an amplifier, of a counter electromotive force generated in a stator coil of a linear actuator, for continuating a reciprocating movement of a moving element by self-oscillation of the linear actuator, and for an application of a periodic voltage to the stator coil, while the voltage is made sinusoidal if required, so as to render the driving circuit to be high in the driving efficiency and small in dimensions.

Abstract: A linear vibration motor which includes a vibration system, an electromagnetic driver, a detection system, and a control system. The vibration system includes a driven member or reciprocator which is mounted to a magnetic member for reciprocating movement. The amplitude of the reciprocating movement varies as an inverse function of load on the motor. The electromagnetic driver includes a coil and drives the vibration system by applying an electromagnetic force to the magnetic member, the electromagnetic force being produced by a driving current flowing through the coil. The detection system detects at least one characteristic of the vibration system that is related to a characteristic frequency of the vibration system, and produces a feedback signal indicative of a value of the at least one characteristic.

Abstract: A linear oscillating motor capable of assuring a consistent and effective feedback control of keeping a constant oscillation amplitude with varying load conditions. The linear oscillating motor comprises an oscillator carrying a permanent magnet, and a stator with an electromagnet. The electromagnet is supplied with an electric power to develop an electromagnetic drive force of moving the oscillator in a linear direction relative to the stator. A spring is provided to apply a restoring force to the oscillator for providing a linear oscillating motion to the oscillator. A photo-sensor monitors the linear motion of the oscillator and outputs a signal to a reverse-point detector which determines right and left reverse points of the oscillator. A controller applies the electric power to the electromagnet at the drive points respectively defined subsequent in time to the reverse points and in a varying amount for keeping a constant oscillation amplitude of the oscillator.

Abstract: A constant dc current supplying circuit comprises a dc voltage supply, an inverter providing an ac voltage from said dc voltage, and an ac-to-dc converter providing a dc current from the inverter output and supplying the resulting dc current to a load. The inverter includes a switching element driven to turn on and off in order to repetitively interrupt the dc voltage for producing the dc current of which level is determined by on-off time ratio of the switching element. A comparator is included to compare a level of the dc current supplied to the load with a predetermined reference level so as to provide a first output and a second output when the dc current level is below and above the reference level. Also included in the circuit is a feedback controller which generates first and second feedback control signals, respectively in response to the first and second outputs from the comparator.