Gate Energy Recovery

Abstract

Embodiments of the present invention relate to gate energy recovery. Embodiments of the subject matter of the present invention include an apparatus comprising a first switch, a second switch, a third switch, and a transistor. The first switch is coupled to a first voltage device and the transistor to selectively electrically connect the first voltage device to the transistor to provide a first charge to the transistor. The second switch is coupled to a second voltage device and the transistor to selectively electrically connect the second voltage device to the transistor to remove charge from the transistor. The third switch is coupled to the third voltage device and the transistor to selectively couple the third voltage device to the transistor to provide a second charge to the transistor.

Description

[0001] This application is a divisional application of the invention patent application with the application date of December 13, 2016, application number "201611144001.9", and invention name "Gate Energy Recovery".

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This continuation-in application claims priority to U.S. Patent Application No. 14 / 970,694, filed on December 16, 2015, which is incorporated herein by reference in its entirety. Technical Field

[0004] The present invention relates generally to circuits, and more particularly, to supplying and draining charge to and from transistors. Background Art

[0005] Transistors are often used as switches in circuits and for amplifying electrical signals, among other uses. Many transistors, such as field effect transistors and bipolar junction transistors, have three terminals: a gate, a source, and a drain. The source and drain terminals may be coupled to a first potential supplied by, for example, a voltage device such as a battery. The gate terminal may be connected to a second potential supplied by, for example, a second voltage device. Supplying the second potential to the gate of the transistor applies a charge to the gate. Once the applied charge increases beyond a threshold, the gate opens to allow current to flow through the source and drain terminals as provided by the first potential. When current is flowing through the source and drain terminals, the transistor may be referred to as being "on". When the second potential is no longer applied to the gate terminal and the charge is removed from the gate, the current stops flowing through the source and drain terminals. When current does not flow through the source and drain terminals, the transistor may be referred to as being "off".

[0006] Typically, when a transistor is switched from on to off, the charge applied to the gate is actively drawn from the gate. For example, an electrical ground may be electrically connected to the gate, which pulls the charge applied to the gate from the gate. This charge is then lost, effectively becoming lost energy. In applications where transistors are rapidly switched between on and off states, the energy lost by drawing charge can be significant. Summary of the invention

[0007] In general, and in accordance with these various embodiments, a circuit and method for sequentially applying charge to and / or removing charge from a transistor as part of turning a gate on and off, respectively, is provided. When the charge applied to the gate is removed from the gate of a switch, at least a portion of the charge may be removed to a storage device and reused rather than being drawn to ground. For example, a capacitor may be used to provide an electrical potential by which charge is applied to the gate of a transistor. When the charge is drawn, the charge may be at least partially drawn back to the capacitor before the gate is connected to electrical ground, which removes enough charge to completely turn the transistor off. So configured, the charge drawn to the capacitor rather than drawn to ground may be reused the next time the transistor is switched back on. These and other advantages may be understood with reference to the drawings and the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Embodiments of the invention are illustrated in the drawings of the accompanying drawings, in which:

[0009] Figure 1 An example circuit 100 is depicted in which a potential is applied to and / or charge is drawn from a gate 116 of a transistor 114 in stages, wherein charge is recovered from the gate 116 of the transistor 114 , in accordance with some embodiments of the present subject matter.

[0010] Figure 2 is a graph 200 depicting the potential difference across the gate of a transistor as a function of time as potentials are applied to and drawn from the gate of the transistor in stages, in accordance with some embodiments of the present subject matter.

[0011] Figure 3 An example circuit 300 is depicted according to some embodiments of the present subject matter, comprising a first transistor 304, a second transistor 306, and a third transistor 302, the third transistor 302 being coupled to a gate 318 of a driven transistor 308, wherein a potential may be applied to and / or drawn from and recovered from the gate 318 of the driven transistor 308 in steps.

[0012] Figure 4 is a flow chart of example operations for supplying charge to the gate of a transistor in accordance with some embodiments of the present subject matter.

[0013] Figure 5 is a flow chart of example operations for draining charge from a gate of a transistor in accordance with some embodiments of the present subject matter. DETAILED DESCRIPTION

[0014] This section provides an introduction to some embodiments of the subject matter of the present invention. Embodiments of the subject matter of the present invention effectively drive transistors through a staged process of applying charge to the transistors and / or extracting charge from the transistors. In addition, in some embodiments, charge is recovered from the gate of the driven transistor during this process. Through this process, the recovered charge can be used to at least partially drive the gate of the transistor in a subsequent drive cycle. Figure 1 One such example of a circuit is depicted in FIG.

[0015] Figure 1 An example circuit 100 is depicted in which charge is applied to and / or drawn from a gate 116 of a transistor 114 in stages, wherein charge is recovered from the gate 116 of the transistor 114 , in accordance with some embodiments of the present subject matter. Figure 1 The circuit 100 includes a first switch 110, a second switch 112, a third switch 108, and a transistor 114. The circuit 100 also includes a first voltage device 104, a second voltage device 106, and a third voltage device 102. The first switch 110 is coupled to the first voltage device 104 (which has a potential difference “V high ”) and the gate 116 of the transistor 114. The second switch 112 is coupled to the second voltage device 106 (which has a potential difference “V low ”) and the gate 116 of the transistor 114. The third switch 108 is coupled to the third voltage device 102 (which has a potential difference “V int ”) and the gate 116 of transistor 114.

[0016] Each of the voltage devices (i.e., the first voltage device 104, the second voltage device 106, and the third voltage device 102) is operable to provide a potential difference (i.e., supply charge and / or draw charge) to the gate 116 of the transistor 114. For example, the voltage device may be an AC voltage source, a DC voltage source (e.g., a battery, a capacitor, etc.), a ground, or any other device capable of providing a potential difference. Thus, each of the voltage devices may be used to drive the transistor 114 via the gate 116 to allow current to flow through the source and drain of the transistor 114. Although each of the voltage devices may be used to drive the transistor 114, in some embodiments, only the first voltage device 104 (i.e., V high ) is capable of providing a potential to the gate 116 of the transistor 114 sufficient to allow current to flow through the source and drain of the transistor 114. In some embodiments, the second voltage device 106 (i.e., V low ) and the third voltage device 102 (ie, V int) cannot provide a potential to the gate 116 of the transistor 114 sufficient to allow current to flow through the source and drain of the transistor 114. In addition, in the example provided, the third voltage device 102 (ie, V int ) is greater than the potential difference of the second voltage device 106 (ie, V low ) potential difference.

[0017] Because the third voltage device 102 may not be able to provide a potential sufficient to allow current to flow through the source and drain of the transistor 114, the third switch 108 may be closed (while the first switch 110 and the second switch 112 are open) to divide the potential difference V int applied to the gate 116 of transistor 114 to partially drive the transistor. That is, the potential difference V int 14. The third switch 108 may be applied to the gate 116 of the transistor 114 without turning on the transistor 114. In other embodiments, the third voltage device 102 may be capable of providing a potential sufficient to allow current to flow through the source and drain of the transistor 114. In either case, the third switch 108 may be considered a pre-charge switch because, although closing the pre-charge switch applies some charge from the third voltage device 102 to the transistor 114, the charge is less than the final charge applied to the transistor 114. Then, the third switch 108 may be opened and the first switch 110 may be closed. Closing the first switch 110 applies the potential difference V high is applied to the gate 116 of the transistor 114. Whether the third voltage device 102 is able to provide a potential sufficient to allow current to flow through the source and drain of the transistor 114, the potential difference V high is sufficient to allow current to flow through the source and drain of transistor 114. Because the potential difference V high is sufficient to allow current to flow through the source and drain of transistor 114, so when the potential difference V high When applied to the gate 116 of transistor 114, transistor 114 is turned on. Thus, in this sense, first switch 110 may be considered an "on switch" because closing the on switch applies charge from first voltage device 104 to transistor 114 sufficient to allow current to flow through transistor 114.

[0018] Depending on the components of the circuit, when the first switch 110 is turned off, the flow of current through the source and drain of the transistor 114 may stop. That is, in some embodiments, turning off the first switch 110 may cause the transistor 114 to turn off, while in other embodiments, the transistor 114 may not turn off until the charge from the gate 116 of the transistor 114 is actively drawn. Regardless of whether the current flows through the source and drain of the transistor 114 after the first switch 110 is turned off, there is still a potential difference across the gate 116 of the transistor 114 (i.e., the charge accumulated on the gate 116 of the transistor 114). In some embodiments, the third voltage device 102 is operable to draw this potential difference from the gate 116 of the transistor 114. In such embodiments, the third switch 108 is closed while the first switch 110 and the second switch 112 are still open. If the potential of the third voltage device 102 is less than the potential difference that exists across the gate 116 of the transistor 114, then the third voltage device 102 will draw charge from the gate 116 of the transistor 114. After the charge from the gate 116 of the transistor 114 is drawn to the third voltage device 102, any remaining charge may be drawn to the second voltage device 106. Any remaining charge may be drawn to the second voltage device 106 by opening the third switch 108 and then closing the second switch 112. In this sense, the second switch 112 may be considered an off switch because closing the off switch allows any charge remaining on the transistor 114 to dissipate, thereby completely shutting off the movement of current through the transistor 114.

[0019] Although the above description only uses one voltage device (i.e., the third voltage device 102) to apply pre-charge, some embodiments are not so limited. In some embodiments, multiple voltage devices can be used to apply pre-charge. For example, Figure 1 As depicted using dashed lines in FIG. 1 , two additional voltage devices (ie, fourth voltage device 122 and fifth voltage device 124) may be used. In such embodiments, the fifth switch 120 may be closed first, thereby increasing the potential difference V int-2 is applied to the gate 116 of the transistor 114. Once the potential across the gate 116 of the transistor 114 has stabilized, the fifth switch 120 is opened and the fourth switch 118 is closed. Closing the fourth switch 118 reduces the potential difference V int-1 is applied to the gate 116 of the transistor 114. Once the potential difference across the gate 116 of the transistor 114 has stabilized, the fourth switch 118 can be opened and the third switch 108 can be closed. As can be seen, any number of voltage devices can be used as pre-charge voltage devices. For ease of reading, portions of this specification will only refer to a single pre-charge switch and pre-charge voltage device, however, it should be noted that embodiments of the subject matter of the present invention can utilize a greater number of pre-charge switches and pre-charge voltage devices.

[0020] although Figure 1 The discussion of describes driving a transistor via its gate, but in some embodiments, the transistor may be driven by a terminal other than the gate. For example, in some embodiments, the transistor may be driven by a back gate (or any other terminal) as an alternative or in addition to the gate.

[0021] Figure 1 Depicts an example circuit for increasing the efficiency of the gate of a drive transistor, while Figure 2 Depicted in e.g. Figure 1 The potential difference across the gate of a transistor in an example circuit described in FIG.

[0022] Figure 2 2 is a graph 200 depicting a potential difference across a gate of a transistor as a function of time as a potential is applied to and drawn from the gate of the transistor in stages, in accordance with some embodiments of the present subject matter. The potential difference across the gate of the transistor (i.e., the voltage across the gate of the transistor) is denoted as “V gate " and plot the potential difference on the Y axis of the graph. Plot time on the X axis of the graph. Figure 1 As described in the discussion of the invention, the gate of the transistor is coupled to three voltage devices: high The first voltage device has a potential difference V low The second voltage device has a potential difference V int At a time before t=0, V gate ≤V low , and the first switch, the second switch and the third switch are all disconnected.

[0023] At t=0, the third switch is closed and the potential difference V int During the first time period 202, the potential difference across the gate of the transistor and the potential difference of the third voltage device move towards equilibrium, so that at the end of the first time period 202, V gate =V int At the end of the first time period 202, the third switch is opened.

[0024] At the beginning of the second time period 204, the first switch is closed. When the first switch is closed, the potential difference V high During the second time period 204, the potential difference across the gate of the transistor moves towards equilibrium with the potential difference of the first voltage device, so that at the end of the second time period 204, V gate =V high At the end of the second time period 204 (ie, when V gate =V high), the potential difference across the gate of the transistor is sufficient to allow current to flow through the source and drain of the transistor (ie, the transistor is “on”). It should be noted that in some embodiments, V high can be large enough (and the source / drain voltage small enough) so that V high is greater than the minimum voltage necessary to achieve the threshold voltage of the transistor. In such embodiments, V gate May never reach V high However, assuming that V high is sufficient to allow current to flow through the drain and source of the transistor, and at the end of the second time period 204, V gate May not be equal to V high , then V gate The first switch 206 is connected to the transistor gate 208 and the first switch 208 is connected to the transistor gate 209. ... drain 209.

[0025] After the first switch is opened, the potential difference across the gate of the transistor may be non-zero. According to some embodiments of the present subject matter, just as the potential difference across the gate of the transistor is applied in steps, the potential difference across the gate of the transistor may be drawn in steps. For example, after the first switch is opened, the third switch may be closed. Figure 2 As depicted in FIG. 2 , the third switch is closed at the beginning of the fourth time period 208. During the fourth time period 208, charge from the gate of the transistor is drawn to the third voltage device. In simple terms, during the fourth time period 208, the potential difference across the gate of the transistor and the potential difference of the third voltage device move toward equilibrium, such that at the end of the fourth time period 208, V gate =V int At the end of the fourth time period 208, the third switch is opened.

[0026] At the beginning of the fifth time period 210, the second switch is closed. During the fifth time period, the charge from the gate of the transistor is drawn to the second voltage device. In some embodiments, the second voltage device is grounded. In such embodiments, all (or most) of the remaining charge is drawn to the second voltage device, and the potential difference across the gate of the transistor reaches zero at the end of the fifth time period 210.

[0027] Example Circuit

[0028] Figure 1 and 2 Provides introductory information on a general circuit having multiple switches and voltage devices for driving the gate of a transistor, and Figure 3 and the accompanying text describe more specific exemplary circuits in which several transistors are used as switches to control the application of potential differences from multiple voltage devices to the gate of a drive transistor.

[0029] Figure 3 An example circuit 300 is depicted according to some embodiments of the present subject matter, comprising a first transistor 304, a second transistor 306, and a third transistor 302, the third transistor 302 being coupled to a gate 318 of a driven transistor 308, wherein a potential can be applied to and / or drawn from the gate 318 of the driven transistor 308 and allowed to be recovered from the gate 318 of the driven transistor 308 in steps. The source of the first transistor 304 is coupled to a first voltage device 316, the drain of the first transistor 304 is coupled to the gate 318 of a switch transistor 308, and the gate of the first transistor is coupled to a controller 310. The source of the second transistor 306 is coupled to the gate 318 of the driven transistor 308, the drain of the second transistor 306 is coupled to a second voltage device (in this example, ground), and the gate of the second transistor 306 is coupled to the controller 310. The source of the third transistor 302 is coupled to a third voltage device 320 (e.g., a capacitor, such as Figure 3 ), the drain of the third transistor 302 is coupled to the gate 318 of the driven transistor, and the gate of the third transistor 302 is coupled to the controller 310. The third voltage device 320 is used to both apply charge to the gate 318 of the driven transistor 308 and to draw charge from the gate 318 of the driven transistor 308. Therefore, the charge remaining on the gate 318 of the driven transistor 308 that would otherwise be drawn to ground is recovered by the third voltage device 320 and applied to the gate 318 of the driven transistor 308 in a subsequent cycle to assist in driving the gate 318 of the driven transistor 308.

[0030] When a potential difference is applied to the gate 318 of the driving transistor 308, the controller 310 applies a potential difference to the gate of the third transistor 302 so as to allow current from the third voltage device 320 to flow through the source and drain of the third transistor 302 and to the gate 318 of the driven transistor 308. In simple terms, the controller 310 turns on the third transistor 302. After the third voltage device 320 has applied its potential difference to the gate 318 of the driven transistor 308, the controller 310 turns off the third transistor 302. In one embodiment, the controller 310 may monitor the potential of the third voltage device 320 and turn off the third transistor 302 when the third voltage device 320 has been discharged. Additionally or alternatively, the controller 310 may monitor the potential difference across the gate 318 of the driven transistor 308. For example, the sensor 322 may be electrically coupled to the gate 318 of the driven transistor 308 and communicate with the controller 310. In such embodiments, the controller 310 may monitor the sensor 322 to determine when the third transistor 302 should be turned off. For example, the controller 310 may turn off the third transistor 302 when the potential difference across the gate 318 of the driven transistor 318 has stabilized. Figure 3 In the embodiment depicted in , the potential difference of the third voltage device 320 is insufficient to allow current to flow through the source and drain of the driven transistor 308 .

[0031] After the third transistor 302 is turned off, the controller 310 applies a potential difference to the gate of the first transistor 304 to turn on the first transistor 304. When the first transistor 304 is turned on, the potential difference from the first voltage device 316 is applied to the gate 318 of the driven transistor 308. Figure 3 , the potential difference of the first voltage device 316 is sufficient to allow current to flow through the source and drain of the driven transistor 308. The controller 310 continues to provide the potential difference to the gate of the first transistor 304 until it is time to turn off the driven transistor 308. When it is time to turn off the driven transistor 308, the controller 310 stops providing the potential difference to the gate of the first transistor 304. That is, the controller 310 turns off the first transistor 304.

[0032] After turning off the first transistor 304, the controller 310 provides a potential difference to the gate of the third transistor 302. This turns the third transistor 302 on. If the potential difference across the gate 318 of the driven transistor 308 is greater than the potential difference of the third voltage device 320 (i.e., the potential difference across the gate 318 of the driven transistor 308 is greater than the potential difference across the capacitor plates), charge is drawn from the gate 318 of the driven transistor 308 to the third voltage device 320. This charge is recovered by the third voltage device 320 and can be used in a subsequent drive cycle to at least partially drive the gate 318 of the driven transistor 308. After the third voltage device 320 draws the charge from the gate 318 of the driven transistor 308, the controller 310 turns off the third transistor 302. While drawing charge from the gate 318 of the driven transistor 308 to the third voltage device 320, the controller 310 can monitor the potential of the third voltage device 320 and / or the potential difference across the gate 318 of the driving transistor 308. For example, controller 310 may monitor the potential difference across gate 318 of drive transistor 308 via sensor 322. In some embodiments, controller 310 turns off third transistor 302 when the potential difference of third voltage device 320 is equal to the potential difference across gate 318 of drive transistor 308.

[0033] After turning off the third transistor 302, the controller 310 applies a potential difference to the gate of the second transistor 306 to turn on the second transistor 306. When the second transistor 306 is turned on, some or all of the charge remaining on the gate 318 of the driven transistor 308 (if any) may be drawn to the second voltage device. Figure 3 In the embodiment depicted in , the second voltage device is ground.

[0034] Example Operation

[0035] Figure 3 Depicts example circuits according to some embodiments of the present subject matter, while Figure 4 and 5 is a flow chart of example operations for supplying charge to and drawing charge from a transistor. Specifically, Figure 4 is a flow chart of an example operation for supplying charge to a transistor in stages, and Figure 5 is a flow chart of an example operation for drawing charge from a transistor in stages. Figure 4 and 5 The flowchart is based on something similar to Figure 1 and 3 For example, Figure 4 and 5The flowchart is based on a circuit having a first switch, a second switch, a third switch and a driven transistor. The first switch is coupled to a first voltage device (which has a potential difference V high ) and the gate of the transistor. The second switch is coupled to a second voltage device (which has a potential difference V low ) and the gate of the transistor. The third switch is coupled to a third voltage device (which has a potential difference V int ) and the gate of the transistor. Potential difference V high Greater than the potential difference V int , and the potential difference V int Greater than the potential difference V low . Potential difference V high Large enough so that when it is applied to the gate of a transistor, current can flow through the drain and supply of the transistor.

[0036] Figure 4 is a flow chart of example operations for supplying charge to the gate of a transistor in accordance with some embodiments of the present subject matter. Figure 4 At the beginning of the process, all three switches are open. The process starts at box 402.

[0037] At block 402, a third switch is closed. The third switch is coupled to the gate of the transistor and a third voltage device. The third voltage device has a potential difference V int Closing the third switch allows charge to flow from the third voltage device to the gate of the transistor. In some embodiments, charge flows from the third voltage device to the gate of the transistor until the potential difference across the gate of the transistor is equalized with the potential difference of the third voltage device. For example, charge may flow from the third voltage device to the gate of the transistor until the potential difference across the gate of the transistor reaches V int The process continues at block 404. In some embodiments, (e.g., Figure 3 4 and described in the associated text), the potential difference across the gate of the transistor may be monitored. For example, a sensor may be used to monitor the potential difference across the gate of the transistor. In such embodiments, the flow proceeds from block 402 to block 408 (before proceeding to block 404). At block 408, the potential difference across the gate of the transistor is monitored. The flow continues at decision diamond 410. At decision diamond 410, if the potential difference across the gate of the transistor has not yet stabilized, the flow continues at block 408 where the potential difference across the gate of the transistor is monitored. If the potential difference across the gate of the transistor has stabilized, the flow continues at block 404.

[0038] At block 404, the third switch is opened. When the third switch is opened, charge stops flowing between the third voltage device and the gate of the transistor. Assuming no losses, the potential difference across the gate of the transistor after the third switch is opened is still V int . Because the potential difference V int There is insufficient current to allow current to flow through the source and drain of the transistor, so the transistor remains off. Flow continues at block 406 .

[0039] At block 406, the first switch is closed. The first switch is coupled to the gate of the transistor and to a first voltage source. The first voltage source has a potential difference V high Closing the first switch allows charge to flow from the first voltage device to the gate of the transistor. Once the potential difference across the gate of the transistor is sufficient to allow current to flow through the source and drain of the transistor, the transistor is turned on. In some embodiments, the potential difference across the gate of the transistor may reach V high , although this is not required.

[0040] In some embodiments, after block 406, the process ends. However, in other embodiments, a cyclic on and off routine for the transistor may be desirable. In such embodiments, Figure 4 The instance operation can be performed by Figure 5 The example operation presented in the following continues, Figure 5 The example operation presented in FIG. 1 turns off the transistor.

[0041] Figure 5 is a flow chart of example operations for drawing charge from a gate of a transistor according to some embodiments of the present subject matter. The flow starts at block 502 .

[0042] At block 502, a first switch is opened. As previously discussed, the first switch is coupled to a first voltage device and a gate of a transistor so that when the first switch is closed, charge can flow from the first voltage device to the gate of the transistor. Flow continues at block 504.

[0043] At block 504, the third switch is closed. Although the first switch is open at block 502, the potential difference across the gate of the transistor is non-zero. When the third switch is closed, charge can flow between the gate of the transistor and the third voltage device. If the potential difference across the gate of the transistor is greater than the potential difference of the third voltage device, then charge can flow from the gate of the transistor to the third voltage device. The charge on the gate of the transistor is recovered by the third voltage device. This charge can be used to at least partially drive the gate of the transistor in a subsequent drive cycle. The process continues at block 506. In some embodiments (e.g., as Figure 3504 and described in the associated text), the potential difference across the gate of the transistor may be monitored. For example, a sensor may be used to monitor the potential difference across the gate of the transistor. In such embodiments, the flow proceeds from block 504 to block 510 (before proceeding to block 506). At block 510, the potential difference across the gate of the transistor is monitored. The flow continues at decision diamond 512. At decision diamond 512, if the potential difference across the gate of the transistor has not yet stabilized, then the flow continues at block 510 where the potential difference across the gate of the transistor is monitored. If the potential difference across the gate of the transistor has stabilized, then the flow continues at block 506.

[0044] At block 506 , the third switch is opened. When the third switch is open, current cannot flow between the third voltage device and the gate of the transistor. Flow continues at block 508 .

[0045] At block 508, the second switch is closed. When the second switch is closed, the second voltage device is coupled to the gate of the transistor. Thus, any charge remaining on the gate of the transistor can be drawn to the second voltage device. In some embodiments, the potential difference of the third voltage device is regulated by the circuit. For example, if the third voltage device currently has a voltage of zero, then during the off cycle (i.e., during Figure 5 During the example operation depicted in FIG. 1 ), when the third switch is closed, charge can flow from the gate of the transistor upward to the capacity of the third voltage device (ie, V int ). At the other extreme, if the potential difference of the third voltage device is equal to or higher than V int , then any excess charge that cannot be drawn from the gate of the transistor to the third voltage device is drawn to the second voltage device. For example, in some embodiments, any excess charge may be drawn to ground via the second switch. After block 508, the process ends. However, in the embodiments described above in which the transistor cycles between the on state and the off state, the process may continue Figure 4 Instance operation of .

[0046] Overview

[0047] Although the figures and descriptions describe three switches / transistors and three voltage devices coupled to the gate of the driven transistor, the embodiments are not so limited. For example, the third switch / transistor and the third voltage device may be replaced by two or more switches / transistors and voltage devices. In such embodiments, each of the two or more switches / transistors and voltage devices will be coupled to the gate of the driven transistor. Each of the two or more voltage devices will have a capacity that is insufficient to allow current to flow through the source and drain of the driven transistor. Therefore, each of the two or more voltage devices will be able to partially drive the gate of the driven transistor. Similarly, each of the two or more voltage devices will be able to recycle / draw charge from the gate of the driven transistor.

[0048] although Figure 3 A single controller coupled to the gates of the first, second, and third transistors is depicted, but the embodiments are not so limited. In some embodiments, each of the first, second, and third transistors may have a separate and / or independent controller, or both of the transistors may have a common controller. Additionally, in some embodiments, the controller may be able to monitor the potential difference of one or more of the first, second, or third voltage devices and / or the gates of the driven transistors. In such embodiments, the controller may determine when each transistor / switch should be turned on / closed or turned off / opened based on the potential difference readings from one or more of the first, second, or third voltage devices and / or the gates of the driven transistors. Additionally, in some embodiments, the controller may use time as the basis for this determination.

[0049] In some embodiments, the driven transistor is a transistor designed to operate at significant power levels. For example, the transistor may be a power MOSFET. Because of the higher power levels at which the driven transistor operates, the efficiency gain achieved from recycling charge from the gate of the driven transistor may be significant.

Claims

1. A device for grid energy recovery, comprising: a transistor having a control terminal; a first switch coupled between a first voltage device and the control terminal to selectively electrically connect the first voltage device to the control terminal to set the control terminal to a first voltage; a second switch coupled between a second voltage device and the control terminal to selectively electrically connect the second voltage device to the control terminal to set the control terminal to a second voltage; and a third switch coupled between a third voltage device and the control terminal to selectively electrically connect the third voltage device to the control terminal to set the control terminal to a third voltage between the first voltage and the second voltage, wherein the third voltage device is a capacitor configured to apply charge to the control terminal to establish the third voltage and configured to recover charge from the control terminal.

2. The apparatus of claim 1, wherein the first switch, the second switch, and the third switch are all electrically coupled to a gate of the transistor. 3 . The apparatus of claim 1 , wherein the first voltage allows current to flow through the transistor, and the second voltage and the third voltage do not allow current to flow through the transistor.

4. The apparatus of claim 1, wherein one or more of the first switch, the second switch, and the third switch are transistors.

5. The apparatus of claim 1, further comprising: a controller operatively coupled to the first switch, the second switch, and the third switch, wherein the controller is configured to: When the second switch and the first switch are opened, the third switch is closed to apply the third voltage to the control terminal via the third voltage device; After the voltage at the control terminal is stabilized at the third voltage, turning off the third switch; and After the third switch is turned off, the first switch is closed when both the third switch and the second switch are turned off to set the control terminal to the first voltage via the first voltage device.

6. A method of controlling the application of charge to and the removal of charge from a control terminal of a transistor, the method comprising: closing a precharge switch coupled between a capacitor and a control terminal of a transistor, wherein closing the precharge switch sets the control terminal to a first voltage supplied by the capacitor; Disconnecting the pre-charging switch; closing an on switch, wherein closing the on switch sets the control terminal from the first voltage to a second voltage to allow current to flow through the transistor, and the second voltage is greater than the first voltage; and The turn-on switch is opened and the pre-charge switch is closed to allow the capacitor to recover charge from the control terminal.

7. The method according to claim 6, further comprising: Disconnecting the pre-charging switch; and The off switch is closed, wherein closing the off switch sets the control terminal to a third voltage to prevent current from flowing through the transistor.

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