Patent Application
20060262479
Electromagnetic actuators typically include a coil and a controller for controlling the amount of electric current passing through the coil. The current passing through the coil may generate a magnetic flux and the magnetic flux may be proportional to the amount of force generated by the actuator. Therefore, the force generated by an actuator may be controlled by controlling the current passing through the coil, which in turn may be a function of the applied voltage.
Typically, steady state current is controlled using pulse width modulation (“PWM”) techniques. Referring to
Accordingly, when the controller 14 actuates the switch 16, current passes from the power source 12, through the switch 16, through the load 20 and back to the power source 12 by way of the ground 26, thereby increasing the current in the load 20 at a positive rate. However, when the switch 16 is de-actuated, current in the inductive component 22 of the load 20 will pass through the resistive component 24, through the diode 18 by way of the ground 26 and back to the inductive component 22, thereby decreasing the current in the load 20 at a negative rate.
As the current in the load 20 decreases, energy is dissipated from the diode 18 as heat, thereby increasing the power consumption of the system 10 and increasing the temperature of the associated controller assembly.
Accordingly, there is a need for a current control system capable of recovering energy and returning the recovered energy to the power source, thereby facilitating a rapid reduction of current in the load. There is also a need for a current control system capable of operating at high frequencies without detriment to the performance of the system
In one aspect, a current control system may include a load, a power source in selective communication with the load and an energy management regulator adapted to receive electrical energy from the load and transfer the electrical energy to the power source.
In another aspect, a current control system may include a load in electrical communication with a power source by way of a power switch, a high frequency controller adapted to control the actuation of the power switch and a low pass filter system disposed between the power switch and the load.
In another aspect, a method for controlling a current passing through a load may include the steps of electrically connecting the load to a power source, thereby supplying energy to the load, disconnecting the load from the power source, after the disconnecting step, transferring at least a portion of the energy in the load to a capacitor, and, upon reaching a predetermined voltage across the capacitor, transferring at least a portion of the energy from the capacitor to the power source.
Other aspects of the disclosed current control system will become apparent from the following description, the accompanying drawings and the appended claims.
As shown in
The power source 102, the load 110 and the regulator 112 may be connected to ground 132, such as a vehicle chassis or the like.
The controller 104 may control the power switch 106 to achieve the desired current flow through the load 100. In particular, when the controller 104 actuates the switch 106, current may flow from the power source 102, through the switch 106, through the load 110 and back to the power source 102 by way of the ground 132. However, when the switch 106 is de-actuated, the current in the inductive component 114 of the load 110 may flow through the resistive component 116 of the load 110, to the capacitor 122 by way of the ground 132, then through the diode 108 and back to the inductive component 114. As the current passes through the capacitor 122, the current may charge the capacitor 122, thereby storing energy in the capacitor 122 as a voltage across the capacitor 122.
The voltage VLload across the inductive component 114 of the load 110 may be represented as follows:
VLload=IloadRload+VD+VC (Eq. 1)
wherein Iload is the load current, Rload is the resistance of the resistive component 116, VD is the voltage across the diode 108 and VC is the voltage across the capacitor 122. Therefore, as the voltage VC across the capacitor increases, the load current Iload may decrease a corresponding amount.
Thus, the capacitor 122 of the regulator 112 may facilitate a faster reduction of load current, thereby facilitating a more robust control response.
As the voltage across the capacitor 122 increases, the controller 128 may determine that a threshold voltage across the capacitor 122 has been reached and may actuate the power switch 130 of the regulator 112 to facilitate the removal of stored energy, thereby reducing the risk of damage to the components of the system 100. In particular, the controller 128 may actuate switch 130 such that current may flow from the capacitor 122, through the inductor 124 and the switch 130 and back to the capacitor 122. However, when the switch 130 is de-actuated, the current in the inductor 124 may flow through the diode 126 and the power source 102 and back to the inductor 124 by way of the ground 132.
Thus, the energy removed from the load 110 when the switch 106 is de-actuated may be recovered and returned to the power source 102 by way of the regulator 112.
As shown in
The power source 202, the load 210 and the regulator 212 may be connected to ground 230, such as a vehicle chassis or the like.
Thus, when switch 206 is actuated, current may flow (e.g., positive current flow) from the power source 202, through the switch 206 and the load 210 and back to the power source 202 by way of the ground 230. When the switch 206 is de-actuated, current may flow from the load 210, to the capacitor 218 by way of the ground 230, through the diode 228B of the switch 208 and back to the load 210, thereby accumulating a voltage across the capacitor 218 such that the node −Vsource becomes more negative.
When the controller 226 of the regulator 212 determines that the voltage across the capacitor 218 has reached and/or exceeded a predetermined threshold value, the switch 222 may be actuated such that current may flow from the capacitor 218, through the inductor 220 and back to the capacitor 218 by way of the switch 222. When the switch 222 is de-actuated, the current may flow from the inductor 220, through the diode 228C of the switch 224, to the power source 202 and back to the inductor 220 by way of the ground 230, thereby returning energy recovered by the regulator 212 to the power source 202.
An opposite current flow may be achieved by actuating switch 208 such that current may flow from the capacitor 218, through the load 210 by way of the ground 230, through the switch 208 and back to the capacitor 218 by way of the node −Vsource, thereby decreasing the voltage across the capacitor 218. When switch 208 is de-actuated, the current may flow from the load 210, through the diode 228A of the switch 206, through the power source 202 and back to the load 210 by way of the ground 230.
The switch 224 may be actuated such that current may flow from the power source 202, through the switch 224 and the inductor 220 and back to the power source 202 by way of the ground 230. When the switch 224 is de-actuated, current may flow from the inductor 220, through the capacitor 218 and the diode 228D of the switch 222 and back to the inductor 220, thereby accumulating a voltage across the capacitor 218.
Thus, the voltage of the node −Vsource may be controlled by controlling the actuation and de-actuation of switches 206, 208, 222, 224, which may facilitate the recovery and return of electrical energy to the power source 202, while facilitating bidirectional current flow.
As shown in
The current feedback system 312 may include a sense resistor 320 and an amplifier 322, such as a differential amplifier or the like. The amplifier 322 may detect a voltage drop across the resistor 320 and may communicate a corresponding current signal to the controller 304 (e.g., by way of communication line 326). Therefore, the controller 304 may generate a control signal for controlling the switch 306 based upon an input command 328 and current feedback 326 from the current feedback system 312. In one aspect, the controller 304 may operate at high frequencies, such as about 50 to about 150 kHz, for example.
The low pass filter system 310 may include an inductor 316 and a capacitor 318 and may be adapted to filter high frequency signals. In one aspect, the low pass filter system 310 may reduce the bandwidth of the signals that reach the sense resistor 320 and ultimately the load 314. For example, filtered signals may have a frequency of about 0 to about 5 kHz.
Thus, by incorporating the low pass filter 310, the controller 304 may be a high frequency controller (e.g., a high frequency PWM controller) and may control the switch 306 at a high frequency without some or all of the disadvantages (e.g., EMC problems) associated with a high frequency signal passing through the wire harness 315, which may be relatively long, to the load 314.
Referring to
Thus, the system 400 may achieve bidirectional current flow, as described above, in response to an input signal 418 and a current feedback signal 420 from the current feedback system 416. Furthermore, the energy management regulator may facilitate the recovery and return of electrical energy to the power supply. Still furthermore, with the addition of the low pass filter system 414, the controller 404 may operate the switches 406, 408 at a high frequency without negative downstream effects.
Although various aspects of the disclosed current control system have been shown and described, modifications may occur to those skilled in the art upon reading the specification. This application includes such modifications and is limited only by the scope of the claims.
This application claims priority from U.S. Ser. No. 60/682,784 filed on May 19, 2005, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60682784 | May 2005 | US |
