Motor control circuit for supplying a controllable driving current

Abstract

For applying a driving current to a motor, an H-bridge circuit is constructed by a first and a second switching unit and a first and a second linear unit. An error amplifier generates an error signal representative of a difference between the driving current detected by a current detecting circuit and a command current signal. A state control circuit synchronously controls the first and second switching units and a feedback circuit. Through the feedback circuit, the error signal is selectively applied to the first or second linear unit such that one is operated in a linear mode and the other is operated in a nonconductive mode, thereby controlling the driving current to become proportional to the command current signal. The state control circuit further controls a brake circuit for transforming the error signal into a brake signal to operate the first and second linear units simultaneously in a conductive mode.

Description

BACKGROUND OF INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a motor control circuit and, more particularly, to a motor control circuit for supplying a controlling driving current to a motor. [0003] 2. Description of the Related Art [0004] Generally speaking, an H-bridge circuit constructed by four switch transistors may supply a driving current to a motor, such as DC motor, stepping motor, voice coil motor, and the like, for controlling a rotating direction, a rate of rotation, and other operational characteristics. [0005]FIG. 1 is a circuit diagram showing a conventional H-bridge circuit 10 for driving a motor M. Referring to FIG. 1, the motor M is coupled between a supply voltage source Vm and a ground potential through the H-bridge circuit 10. Although the motor M is in practice a complex system consisting of a variety of mechanical and electrical components, the driving current is essentially applied to a winding of the motor M for generating...

AI Technical Summary

Benefits of technology

[0010] Conventionally, a pulse width modulation (PWM) technique is usually adopted to control the absolute value of the driving current applied to the motor. More specifically, in the situation where the NMOS transistor Q4 is turned on and the NMOS transistors Q2 and Q3 are turned off, the control signal G1 may be implemented by a PWM signal such that the ON time of the NMOS transistor Q1 is determined by the duty cycle of the PWM control signal G1, thereby controlling an average value of the driving current. However, the PWM technique inevitably induces excessive disturbances in the supply voltage source Vm and the driving current applied to the motor M. For the application which requires extremely precise control of the motor, the conventional PWM technique may cause several disadvantageous effects. Therefore, it is desired to provide a control circuit capable of supplying a low noise driving current to the motor M.

[0011] An object of the present invention is to provide a motor control circuit capable of controlling a direction and an absolute value of the driving current for a motor.

[0012] Another object of the present invention is to provide a motor control circuit capable of keeping constant an absolute value of a driving current for a motor.

[0013] Still another object of the present invention is to provide a motor control circuit capable of suppressing noise of a driving current for a motor.

[0014] According to the present invention, a motor control circuit is provided for supplying a driving current to a motor. The driving current is applied between a first terminal and a second terminal of the motor. The motor control circuit includes: an H-bridge circuit, a current detection circuit, an error amplifier, a feedback circuit, and a state control circuit.

[0015] The H-bridge circuit has a first switching unit, a second switching unit, a first linear unit, and a second linear unit. The first switching unit and the first linear unit are together coupled to the first terminal. The second switching unit and the second linear unit are together coupled to the second terminal. The current detection circuit generates a current detection signal representative of the driving current of the motor. The error amplifier generates at least one error signal representative of a difference between the current detection signal and a command current signal. The at least one error signal is electrically separate from the first and the second switching units. The feedback circuit is coupled to the error amplifier for receiving the at least one error signal so as to apply the at least one error signal selectively to the first or the second linear unit. The state control circuit synchronously controls the first and the second switching units and the feedback circuit.

Problems solved by technology

However, the PWM technique inevitably induces excessive disturbances in the supply voltage source Vm and the driving current applied to the motor M. For the application which requires extremely precise control of the motor, the conventional PWM technique may cause several disadvantageous effects.

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