Amplifiers – With semiconductor amplifying device – Including particular power supply circuitry
Reexamination Certificate
1999-04-13
2001-03-06
Shingleton, Michael B (Department: 2817)
Amplifiers
With semiconductor amplifying device
Including particular power supply circuitry
C330S256000, C330S298000, C330S009000, C330S010000, C330S310000, C327S307000
Reexamination Certificate
active
06198350
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to signal amplifying circuits, and more specifically to such circuits used for sensing and amplifying motor winding current signals such as those produced by brushless DC motors.
BACKGROUND OF THE INVENTION
Systems for controlling speed, torque and/or position of DC motors are known and have been widely used in a variety of applications including automotive control systems. Generally, such DC motors fall into two broad categories; namely brushed DC motors and brushless DC motors. While brushless DC motors typically offer desirable performance features and certain advantages over brushed DC motors in an automotive environment, such features and advantages may often be offset by the complexity of motor control and motor drive circuits required to accurately control motor operation. For example, controlled stoppage, accurate motor shaft positioning, motor reversal and consistent control of motor output torque are all difficult to achieve with brushless DC motors.
Dedicated systems for controlling and driving brushless DC motors are known. In such systems, a motor control circuit is typically operable to detect motor shaft position as well as motor drive current, and a motor drive circuit is, in turn, responsive to motor control signals supplied by the motor control circuitry to drive the DC motor in a desired manner. In known DC motor drive circuits, the motor control circuit typically includes a number of motor position sensors for providing a corresponding number of signals indicative of motor position as well as a sense amplifier operable to amplify one or more signals corresponding to motor drive current. The motor control circuit is typically responsive to motor position and/or motor drive current to provide the motor control signals to the motor drive circuit. Generally, the resolution of the motor control circuit is dependent upon the performance of the sense amplifier as well as the accuracy of the motor position detection circuitry.
Heretofore, many configurations of analog sense amplifiers have been designed, and some such configurations have been widely used in motor control circuits. However, such sense amplifier circuits suffer from several drawbacks, particularly when used in high voltage automotive applications. For example, known sense amplifiers developed for automotive applications often suffer from slow response time and high power dissipation. Moreover, due to high DC gains required in motor control circuit applications, most known sense amplifier circuits exhibit unacceptably high DC offset voltages, thereby resulting in a reduction of available system bandwidth. What is therefore needed is an improved sense amplifier circuit particularly suited for motor control system applications that is both power efficient and capable of high speed operation in a high voltage automotive environment
SUMMARY OF THE INVENTION
The present invention addresses the foregoing shortcomings in known signal amplifying circuits. In accordance with one aspect of the present invention, a signal amplifying circuit comprises an amplifier having first and second inputs and an amplifier output defining an output of the signal amplifying circuit, a first diode circuit having a cathode defining a first input of the signal amplifying circuit and an anode, a first resistor connected between the anode of the first diode circuit and the first input of the amplifier, a first current source supplying a first current to a common connection of the anode of the first diode circuit and the first resistor, a second diode circuit having a cathode defining a second input of the signal amplifying circuit and an anode, a second resistor connected between the anode of the second diode circuit and the second input of the amplifier, and a second current source supplying a second current to a common connection of the anode of the second diode circuit and the second resistor.
In accordance with another aspect of the present invention, a signal amplifying circuit comprises an amplifier defining a first input, a second input and an output, wherein the amplifier is adapted for connection to a first voltage supply producing a first voltage reference. The amplifier is further adapted to receive a differential input signal at the first and second inputs and produce as an amplifier output signal an amplified representation of the differential input signal at the amplifier output between a range of the first voltage reference and a lower reference potential. Also included is an output buffer having an input stage connected to the output of the amplifier and an output stage, wherein the output stage is adapted for connection to a second voltage supply producing a second voltage reference greater than the first voltage reference. The output buffer receives the amplifier output signal at the output buffer input and produces as a buffered output signal the amplified representation of the differential input signal at the output buffer stage between a range of the second voltage reference and the lower reference potential.
In accordance with a further aspect of the present invention, a signal amplifying circuit comprises an amplifier responsive to an input signal to produce as amplifier output signal an amplified representation of the input signal, and an output buffer having an input stage receiving the amplifier output signal and an output stage responsive to the amplifier output signal to produce a buffered output signal and associated load current at a buffer output. The output buffer includes means for comparing the amplifier output signal with the buffered output signal and modulating the load current as a function of a difference between the amplifier output signal and the buffered output signal.
One object of the present invention is to provide an improved signal amplifier circuit.
Another object of the present invention is to provide such an improved signal amplifier circuit capable of high speed operation in a high voltage environment while also minimizing power dissipation.
Yet another object of the present invention is to provide such an improved signal amplifier circuit capable of cancelling DC offset voltages attributable to the amplifier circuit itself.
Still another object of the present invention is to provide an improved signal amplifier circuit capable of allowing below-ground input voltages and of providing for input fault detection capability.
These and other objects of the present invention will become more apparent from the following description of the preferred embodiment.
REFERENCES:
patent: 3035233 (1962-05-01), Heyser
patent: 3467908 (1969-09-01), Burwen
patent: 3526810 (1970-09-01), Williams et al.
patent: 4027270 (1977-05-01), Pitel
patent: 5008632 (1991-04-01), Sutterlin
patent: 5815040 (1998-09-01), Barbetta
Delphi Technologies Inc.
Funke Jimmy L.
Shingleton Michael B
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