Patent Application
20070103103
Not Applicable
Not Applicable
Not Applicable
1. Field of the Invention
This invention relates in general to a motor supply circuit, and more specifically, to a bipolar voltage conversion motor supply circuit.
2. Description of the Related Art
Bi-directional small motors are commonly used for vehicle applications devices that require bidirectional movement such as a power seating system. These motors operate in a forward rotational direction and a reverse rotational direction. To operate the motor in a first rotational direction, a bipolar input voltage is provided to the input terminals of the motor to drive the motor in the first rotational direction (e.g., clockwise). To operate the motor in the reverse direction, the polarity of supply voltage is switched so that an opposite bipolar voltage input is provided to the input terminals for driving the motor in a second rotational direction (e.g., counterclockwise).
With respect to seat motors, and in particular for applications having seat memory, a seat controller maintains a current rotational position of the motor via a rotational position sensor so that when a stored memory seat button is actuated, the seat controller can control the polarity of the power supplied to the motor for directionally driving the motor to the position correlating to the seat position stored in memory.
The rotational position sensor is used to sense the rotational position of a gear member within the motor. The gear member is coupled to the gear output shaft at a first end of the shaft and is coupled to the accessory device gear output shaft at a second end. By knowing the direction and degree of rotational movement that the gear member of the motor has rotated, the seat controller can correlate the rotational position of the gear member to the positional movement of the seat (e.g., forward/backward motion). Other movements such as recline, tilt, and up/down may be correlated in a similar manner.
The rotational position sensor is typically powered by a unipolar voltage. The rotational position sensor receives the unipolar voltage (typically 5 volts) via a circuit separate than the circuit used to energize the electromagnetic armature. Since the motor requires that the polarity be switched for driving the motor between a forward or reverse direction, polarity on a respective circuit will vary. For this reason, a circuit providing power to energize the electromagnetic armature is used separately from the circuit used to power the rotational position sensor. As a result, additional cost and packaging space is required for the additional circuits required to energize the rotational position sensor and electromagnetic armature within the motor.
The present invention has the advantage of powering both the position encoder and the electromagnetic armature utilizing the same voltage supply circuit input to the motor.
In one aspect of the present invention, a DC motor circuit is provided for an automobile accessory that includes biplolar input lines for driving an accessory motor. A bridge rectifier coupled to the bipolar input lines generates a unipolar output. A transient voltage suppressor is connected in parallel with the bridge rectifier. A voltage regulator is coupled to the unipolar output for generating a regulated DC voltage. A position encoder is powered by the regulated DC voltage.
Referring now to the drawings, there is illustrated in
In operation, the input voltage 42 supplied by the external power source is input to the H-bridge circuit 41. H-Bridge circuits are commonly known in the art and are typically constructed using relays and switches, bipolar transistors, MOSFET transistors, power MOSFET's, FET transistors, or microchips that draw low current. The H-bridge circuit can be used for driving a motor forward or backward. This is typically accomplished by switching the voltage between positive to negative (or ground) on the motor leads for reversing the direction of a motor. The voltage is thereafter switched again to drive the motor in the forward direction when required.
The switched output voltage generated by the H-bridge circuit 41 is provided to the connector 26 typically mounted on the motor housing 12 (i.e., gear cover 20). The connector 34, as discussed earlier, includes the first and third contact terminals 34 and 36 for receiving the switched bi-polar voltage from the H-bridge circuit 41 and providing it to the bipolar input lines 44 within the motor 40. Junction nodes 43a and 43b divides the bipolar input lines 44 for energizing the electromagnetic armature 14 and for providing the bipolar voltage to the conversion circuit 45. The bipolar input voltage is provided to the electrical subcomponents for energizing the electromagnetic armature 14. The various types of motors and electrical subcomponents used to energize the armature are commonly known. The type of motor used will determine which electrical subcomponents are supplied with the bipolar voltage for energizing the electromagnetic armature. The various types of motors include, but are not limited to, a DC brush motor that includes a permanent magnet motor, separately excited DC motor, a series-wound DC motor, brushless motors, AC motors, or switch reluctance motors.
The switchable bipolar voltage provided to the conversion circuit 45 is received by the bridge rectifier 46. The bridge rectifier 46, commonly known as a full-wave rectifier, provides a same polarity output voltage and current for any respective input voltage. That is, whether a positive or negative input voltage is applied across the bipolar input lines 44, the bridge rectifier 46 rectifies the input voltage so that a same polarity voltage is output from the bridge rectifier 46 each time current flows therethrough regardless of the plurality of the bipolar input voltage.
The transient voltage suppressor 48 is connected in parallel to the output of the bridge rectifier 46. The transient voltage suppressor 48 is a clamping device that suppresses sudden voltage increases (i.e., such as voltage spikes) generated by the motor 40. Typically, large transient spikes are generated when dynamic braking occurs within the motor 40. Dynamic braking of a motor involves connecting both fields of a motor to a same polarity input/output (i.e., both fields tied to ground, or both to positive). Connecting both sides of the field to the same polarity causes the motor to stop instantaneously as opposed to coasting to a stop. The energy leaving both sides of the field electromagnetically locks the armature in place since there is a same electromagnetic force exerted on each respective field of the motor. When this occurs, back emf generated within the motor 40 can typically range upwards of 100 Volts. Large transient spikes can damage the electrical circuitry of the motor 40 , more specifically, the position encoder 32. The transient voltage suppressor 46 suppresses voltage increases above a predetermined voltage (e.g. clamping voltage above 23 Volts), and as a result, limits the voltage spikes to safe operating levels while directing damaging currents away from the position encoder 32.
The first capacitor 50 is connected in parallel with the bridge rectifier 46 and the transient voltage suppressor 48 for reducing electrical noise during low operating voltage operations and for reducing voltage spikes that occur below that which the transient voltage suppressor 48 is rated for. Furthermore, the energy stored and output by the capacitor 50 may lessen any variation of the output of the bridge rectifier 46 caused from any voltage drops in the output voltage or current output from the rectifier bridge 46.
The voltage regulator 52 receives the unipolar output voltage of the bridge rectifier 46 for regulating the DC voltage that is provided to the position encoder 32. The voltage regulator 52 receives the unipolar output voltage from the bridge rectifier 46, which may potentially vary, and converts it to a constant regulated voltage. Preferably, the unipolar output voltage from the bridge rectifier 46 is stepped down and regulated to 5 volts for powering the position encoder 32. Alternatively, voltages other than 5 volts may be used (e.g., 5-15 volts) depending on the operating input voltages of the position encoder utilized. The regulated voltage is provided to the position encoder 32 via circuits 60 and 62.
An energy storage device 54, such as a second capacitor, may be connected in parallel to the position encoder 32 for storing the regulated voltage output from the voltage regulator 52. The energy storage device 54 may be used to store and supply voltage to the position encoder 32 when voltage variances occur in the voltage output from the voltage regulator 52.
The position encoder 32 is preferably a non-contact sensor, such as a hall-effect sensor or potentiometer. The position encoder 32 monitors the rotational position of the gear member 16 within the gear housing 18. A position signal is generated identifying the rotational position of the gear member 14 within the gear housing 18 and is then output via circuit 61 to the connector 26. Based on the type position encoder 32 used, the position signal may be a relative position signal based on the alignment of sensed device to the magnetic field as it rotates in and out of a magnetic field or may be an absolute position where the absolute position of the sensed device on the rotating gear member 14 is known at all times. The position signal is then output from the connector 26 via terminal contact 35 to a controller (not shown) for correlating the rotational position of the gear member 14 to a position of an attaching accessory device being driven by the motor 40.
The output of the position encoder 32 is an open collector transistor requiring pull-up resister 63 (e.g., 1.8 kohms) to provide an output position signal between 0 and 5 volts. For example, if the position encoder 32 is a Hall-effect sensor (digital), then the output position signal will be either 0 or 5 volts. If the position encoder 32 is a potentiometer, then the output position signal can vary between 0 and 5 volts Alternatively, a 5 volt power source with the pull-up resistor may be connected to the circuit (external to the motor 40) extending from contact terminal 35 to the controller in place of pull-up resistor 63 connected between circuit 60 and 61.
In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. For example, the present invention may be used within an AC motor with minor modifications without departing from the scope of the invention. It must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.
