Switching assemblies using bidirectional double-base bipolar junction transistors and their operation methods

Abstract

This disclosure relates to a switching assembly using a bidirectional double-base bipolar junction transistor and a method of operating thereof. One example is a method comprising: injecting charge carriers into the upper base of the transistor at a first rate, the injection at the first rate causing a current to flow through the transistor from an upper collector-emitter to a lower collector-emitter, and the current flow causing a first voltage drop measured across the upper collector-emitter and the lower collector-emitter; and then, during a predetermined time period prior to the end of a first conduction cycle of the transistor, injecting charge carriers into the upper base at a second rate lower than the first rate, the injection at the second rate causing a second voltage drop measured across the upper collector-emitter and the lower collector-emitter, the second voltage drop being higher than the first voltage drop; and then deconducting the transistor at the end of the conduction cycle.

Description

Technical Field

[0001] This application relates to a bidirectional double-base bipolar junction transistor, and, in particular, a switching assembly using a bidirectional double-base bipolar junction transistor. Background Technology

[0002] A bidirectional double-base bipolar junction transistor (B-TRAN) is a junction transistor in which a base and collector-emitter junction are constructed on a first side of the body region, and different and separate base and collector-emitter junctions are constructed on a second side of the body region opposite to the first side. When properly configured by an external driver, current can selectively flow through the B-TRAN in either direction, and therefore the B-TRAN device is considered a bidirectional device. Based on this bidirectionality, whether the collector-emitter junction is considered a collector (e.g., current flowing into the B-TRAN) or an emitter (e.g., current flowing out of the B-TRAN) depends on the direction of the applied external voltage and thus the direction of current flow through the B-TRAN. When a particular collector-emitter junction acts as the collector, the base on the same side of the body region may be referred to as the collector-side base or c-base. Correspondingly, when a particular collector-emitter junction acts as the emitter, the base on the same side of the body region may be referred to as the emitter-side base or e-base. Consider the current flow through a B-TRAN device in a specific direction (e.g., from the upper collector-emitter to the lower collector-emitter). In this case, the upper collector-emitter acts as the collector, and the lower collector-emitter acts as the emitter.

[0003] B-TRAN can have varying conduction modes and corresponding forward voltage drops. For example, in diode conduction mode, the upper base or collector-emitter junction can be directly coupled to the upper collector-emitter junction, and the lower base or emitter junction can be electrically floating. In an example diode conduction mode, the forward voltage drop across the B-TRAN can be approximately the forward voltage drop of a silicon-based diode (e.g., about 1.0V). However, in transistor conduction mode, in an example where current flows from the upper collector-emitter junction to the lower collector-emitter junction, the forward voltage drop can be reduced by increasing the voltage at the upper base relative to the upper collector-emitter junction (e.g., to between about 0.2V and 0.3V, including terminal values). While transistor conduction mode is beneficial for its lower forward voltage drop, it also has an increased turn-off time that makes the B-TRAN non-conductive. Summary of the Invention

[0004] One example is a method of operating a bidirectional double-base bipolar junction transistor, the method comprising: injecting charge carriers into the upper base of the transistor at a first rate, the injection at the first rate causing a current to flow through the transistor from an upper collector-emitter to a lower collector-emitter, and the current flow causing a first voltage drop measured across the upper collector-emitter and the lower collector-emitter; and then, during a predetermined time period prior to the end of a first conduction cycle of the transistor, injecting charge carriers into the upper base at a second rate lower than the first rate, the injection at the second rate causing a second voltage drop measured across the upper collector-emitter and the lower collector-emitter, the second voltage drop being higher than the first voltage drop; and then deconducting the transistor at the end of the first conduction cycle.

[0005] In the example method, making the transistor non-conductive may further include directly coupling the lower base of the transistor to the lower collector-emitter junction of the transistor, and extracting charge carriers from the upper base. After extracting charge carriers from the upper base, the example method may include electrically floating the upper base.

[0006] The example method may further include injecting charge carriers into the upper base at a third rate higher than the first rate before injecting charge carriers at the first rate, thereby reducing the switching time from the off-mode to the conducting state of the transistor.

[0007] In the example method, making the transistor non-conductive may further include: stopping the injection of charge carriers into the upper base; making the upper base electrically float; and directly coupling the lower base of the transistor to the lower collector-emitter of the transistor.

[0008] In the example method, injecting charge carriers through the upper base at the first rate may further include coupling a first voltage source between the upper collector-emitter and the upper base. Injecting charge carriers through the upper base at the second rate may further include coupling a second voltage source between the upper collector-emitter and the upper base, the second voltage source being different from the first voltage source. Injecting charge carriers through the upper base at the second rate may further include reducing the output voltage of the first voltage source.

[0009] In the example method, injecting charge carriers through the upper base at the first rate may further include coupling a first current source between the upper collector-emitter and the upper base. Injecting charge carriers through the upper base at the second rate may further include coupling a second current source between the upper collector-emitter and the upper base. Injecting charge carriers through the upper base at the second rate may further include reducing the current output of the first current source.

[0010] The example method may further include making the transistor conductive by directly coupling the upper collector-emitter to the upper base before injecting charge carriers at the first rate.

[0011] In the example method, the first voltage drop may be less than 0.2 volts or less, and the second voltage drop may be greater than 0.4 volts.

[0012] The example method may further include, after deconducting the transistor: injecting charge carriers into the lower base of the transistor at a third rate, the third rate causing current to flow through the transistor from the lower collector-emitter to the upper collector-emitter, and the current flow causing a third voltage drop across the lower collector-emitter and the upper collector-emitter; and then, during a predetermined time period at the end of the second conduction cycle, injecting charge carriers into the lower base at a fourth rate lower than the third rate, the fourth rate causing a fourth voltage drop measured across the lower collector-emitter and the upper collector-emitter, the fourth voltage drop being higher than the third voltage drop; and then deconducting the transistor at the end of the second conduction cycle.

[0013] Another example is a switching assembly comprising: a bipolar junction transistor defining an upper base, an upper collector-emitter junction, a lower base, and a lower collector-emitter junction; a driver defining an upper base terminal coupled to the upper base, an upper conductive terminal coupled to the upper collector-emitter junction, a lower base terminal coupled to the lower base, and a lower conductive terminal coupled to the lower collector-emitter junction. The driver may be configured to: inject charge carriers into the upper base at a first rate, such injection at the first rate resulting in a first conductivity through the transistor from the upper collector-emitter to the lower collector-emitter junction; predict the end of a first conduction cycle, and, for a predetermined period prior to the end of the first conduction cycle, inject charge carriers into the upper base at a second rate lower than the first rate, such injection at the second rate resulting in a second conductivity through the transistor from the upper collector-emitter to the lower collector-emitter junction, the second conductivity being lower than the first conductivity; and then deconduct the transistor at the end of the first conduction cycle.

[0014] In the example switch assembly, the driver may further include: a controller; a first voltage source defining a first voltage output; and a first electrically controlled switch defining a first connection coupled to the first voltage output, a second connection coupled to the upper base, and a first control input coupled to the controller. When the driver injects charge carriers into the upper base at the first rate, the controller may be configured to conduct the first electrically controlled switch by asserting the first control input.

[0015] The example switch assembly may further include: a second voltage source defining a second voltage output, the second voltage source being different from the first voltage source; and a second electrically controlled switch defining a first connection coupled to the second voltage output, a second connection coupled to the upper base, and a second control input coupled to the controller. When the driver injects charge carriers into the upper base at the second rate, the controller may be configured to conduct the second electrically controlled switch by asserting the second control input.

[0016] The example switch assembly may further include a setpoint input defined by the first voltage source and coupled to the controller. When the driver injects charge carriers through the upper base at the second rate, the controller may be configured to reduce the voltage applied to the first voltage output.

[0017] In the example switch assembly, the driver may further include: a controller; a first current source defining a first current output; and a first electrically controlled switch defining a first connection coupled to the first current output, a second connection coupled to the upper base, and a first control input coupled to the controller. When the driver injects charge carriers into the upper base at the first rate, the controller is configured to conduct the first electrically controlled switch by asserting the first control input.

[0018] The example switch assembly may further include: a second current source defining a second current output, the second current source being different from the first current source; and a second electrically controlled switch defining a first connection coupled to the second current output, a second connection coupled to the upper base, and a second control input coupled to the controller. When the driver injects charge carriers into the upper base at the second rate, the controller may be configured to conduct the second electrically controlled switch by asserting the second control input.

[0019] The example switch assembly may further include a setpoint input defined by the first current source and coupled to the controller. When the driver injects charge carriers through the upper base at the second rate, the controller may be configured to reduce the current applied to the first current output.

[0020] The example switch assembly may further include: a controller; a component for generating charge carriers; a first electrically controlled switch defining a first connection coupled to the component for generating charge carriers, a second connection coupled to the upper base, and a first control input coupled to the controller; and a second electrically controlled switch defining a first connection coupled to the lower collector-emitter, a second connection coupled to the lower base, and a second control input coupled to the controller. When the driver de-conducts the transistor, the controller may be configured to: conduct the first electrically controlled switch to extract charge carriers through the upper base by asserting the first control input; and then de-conduct the first electrically controlled switch by de-asserting the first control input; and conduct the second electrically controlled switch by asserting the second control input.

[0021] In the example switch assembly, when the driver de-conducts the transistor, the driver can be configured to directly couple the lower base of the transistor to the lower collector-emitter of the transistor and extract charge carriers from the upper base. When the driver de-conducts the transistor, the driver can be further configured to allow the upper base to float after extracting charge carriers from the upper base.

[0022] In the example switch assembly, the driver may be further configured to inject charge carriers into the upper base at a third rate higher than the first rate before injecting charge carriers at the first rate, thereby reducing the switching time from the transistor's off-mode to the conducting state. Attached Figure Description

[0023] For a detailed description of the exemplary embodiments, reference will now be made to the accompanying drawings, in which:

[0024] Figure 1 A cross-sectional front view of a B-TRAN according to at least some embodiments is shown;

[0025] Figure 2 An example model of a B-TRAN according to at least some embodiments is shown, along with an electrical schematic diagram of a conceptual driver circuit.

[0026] Figure 3A An example model and driver circuit are shown, in which the B-TRAN is non-conductive, according to an example embodiment.

[0027] Figure 3B An example model and driver circuit arranged for diode conduction according to at least some embodiments are shown;

[0028] Figure 3C An example model and driver circuit arranged for conduction according to at least some embodiments are shown;

[0029] Figure 3D An example model and driver circuit arranged for pre-shutdown according to at least some embodiments are shown;

[0030] Figure 4 A graph showing the voltage drop across a B-TRAN device over time;

[0031] Figure 5 A graph showing the voltage drop over time of a cross-B-TRAN device according to at least some embodiments;

[0032] Figure 6 Partial block diagrams and partial electrical schematic diagrams of a switch assembly according to at least some embodiments are shown;

[0033] Figure 7 Partial block diagrams and partial electrical schematic diagrams of a switch assembly according to at least some embodiments are shown;

[0034] Figure 8 A graph showing the voltage drop over time of a cross-B-TRAN device according to at least some embodiments;

[0035] Figure 9 A partial electrical schematic diagram of a switch assembly according to at least some embodiments is shown;

[0036] Figure 10 A partial electrical schematic diagram of a switch assembly according to at least some embodiments is shown; and

[0037] Figure 11 The method is illustrated according to at least some embodiments.

[0038] definition

[0039] Various terms are used to refer to specific system components. Different companies may use different names to refer to components—this document is not intended to distinguish between components with different names but the same function. In the following discussion and claims, the terms "comprising" and "including" are used in an open-ended manner and should therefore be interpreted as meaning "including but not limited to...". Moreover, the term "coupled" is intended to indicate indirect or direct connection. Thus, if a first device is coupled to a second device, that connection can be either a direct connection or an indirect connection via other devices and connections.

[0040] The word "about" in relation to the referenced parameter should mean the referenced parameter plus or minus 10 percent (+ / - 10%).

[0041] "Assert" indicates a change in the state of a Boolean signal. Based on the circuit designer's judgment, a Boolean signal can be asserted as high or having a higher voltage, and a Boolean signal can be asserted as low or having a lower voltage. Similarly, "Cancel Assert" should indicate changing the state of a Boolean signal to a voltage level opposite to the asserted state.

[0042] A "bidirectional double-base bipolar junction transistor" should refer to a junction transistor having a base and collector-emitter junction on a first face or side of the body region and a base and collector-emitter junction on a second face or side of the body region. The base and collector-emitter junction on the first side are different from those on the second side. An outward-pointing vector orthogonal to the first side points in the opposite direction to an outward-pointing vector orthogonal to the second side.

[0043] "Upper base" should refer to the base of a bidirectional double-base bipolar junction transistor on the first side of the main body region of the transistor, and should not be interpreted as implying the position of the base relative to gravity.

[0044] "Lower base" should refer to the base of a bidirectional double-base bipolar junction transistor on the second side of the main body region of the transistor, opposite to the first side, and should not be interpreted as implying the position of the base relative to gravity.

[0045] "Upper collector-emitter" should refer to the collector-emitter of a bidirectional double-base bipolar junction transistor on the first side of the main body region of the transistor, and should not be interpreted as implying the position of the collector-emitter relative to gravity.

[0046] "Lower collector-emitter" should refer to the collector-emitter of a bidirectional double-base bipolar junction transistor on the second side of the main body region of the transistor, opposite to the first side, and should not be interpreted as implying the position of the collector-emitter relative to gravity.

[0047] "Injecting charge carriers into the base of a transistor" (e.g., upper base, lower base) should not include directly coupling the base (e.g., through the transistor) to the collector-emitter on the same side of the transistor.

[0048] "Drawing charge from the base of a transistor (e.g., upper base, lower base)" should not include directly coupling the base (e.g., through the transistor) to the collector-emitter on the same side of the transistor.

[0049] The terms “input” and “output” as nouns refer to connections (e.g., electrical, software) and should not be interpreted as verbs requiring action. For example, a timer circuit may define a clock output. An example timer circuit may create or drive a clock signal on the clock output. In systems implemented directly in hardware (e.g., on a semiconductor substrate), these “inputs” and “outputs” define electrical connections. In systems implemented in software, these “inputs” and “outputs” define parameters that are read or written by instructions that perform the function.

[0050] "Controller" should be used individually or in combination to refer to an individual circuit component configured to read inputs and drive outputs in response to inputs, an application-specific integrated circuit (ASIC), a microcontroller with control software, a reduced instruction set computer (RISC), a digital signal processor (DSP), a process with control software, a processor with control software, a programmable logic device (PLD), or a field-programmable gate array (FPGA). Detailed Implementation

[0051] This application claims the benefit of U.S. Provisional Application No. 63 / 026,597, filed May 18, 2020, entitled "Modulation of External Power Supply to Improve B-TRANP Performance," which is incorporated herein by reference in its entirety as reproduced below.

[0052] The following discussion relates to various embodiments of the invention. While one or more of these embodiments may be preferred, the disclosed embodiments should not be construed as or otherwise used to limit the scope of this disclosure (including the claims). Furthermore, those skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is merely an example of that embodiment and is not intended to imply that the scope of this disclosure (including the claims) is limited to that embodiment.

[0053] Various examples relate to methods and systems for operating a bidirectional double-base bipolar junction transistor (B-TRAN). Specifically, various examples relate to controlling the collector-emitter forward voltage drop across the B-TRAN such that the forward voltage drop is low (e.g., 0.1V to 0.2V, including the terminal value) for most of the conduction cycle and increases during a predetermined period before the end of the conduction cycle (e.g., to between 0.4V and 1.0V, including the terminal value). Regarding conductivity, various examples relate to controlling the collector-emitter conductivity through the B-TRAN such that the conductivity is high for most of the conduction cycle and decreases during a predetermined period before the end of the conduction cycle. Increasing the forward voltage drop near the end of the conduction cycle slightly increases the conduction losses across the B-TRAN; however, increasing the forward voltage drop near the end of the conduction cycle reduces the switching time and therefore the switching losses when transitioning the B-TRAN to a non-conductive state. The net effect is a better overall operating efficiency of the B-TRAN. The specification first turns to exemplary B-TRAN devices to guide the reader.

[0054] Figure 1 A cross-sectional front view of a B-TRAN according to at least some embodiments is shown. Specifically, Figure 1 The B-TRAN 100 is shown with an upper or upper side 102 and a lower or lower side 104. The designations "upper" and "lower" are arbitrary and used only for convenience. The upper side 102 faces the opposite direction to the lower side 104. In other words, an outward-pointing vector orthogonal to the upper side 102 (not specifically shown) will point in the opposite direction to an outward-pointing vector orthogonal to the lower side 104 (not specifically shown).

[0055] The upper side 102 includes a collector-emitter contact region 106 that forms a junction with the drift region or the host substrate 108. The upper side 102 further defines a base contact region 110 disposed between the collector-emitter contact regions 106. The collector-emitter contact regions 106 are coupled together to form an upper collector-emitter 112. The base contact regions 110 are coupled together to form an upper base 114. Similarly, the lower side 104 includes a collector-emitter contact region 116 that forms a junction with the host substrate 108. The lower side 104 further defines a base contact region 118 disposed between the lower collector-emitter contact regions 116. The collector-emitter contact regions 116 are coupled together to form a lower collector-emitter 120. The lower base contact regions 118 are coupled together to form a lower base 122.

[0056] Example B-TRAN 100 is an NPN structure; therefore, collector-emitter contact regions 106 and 116 are N-type, and base contact regions 110 and 118 are P-type. In the example system, a shallow N+ region provides ohmic contact from collector-emitter contact regions 106 and 116 to the corresponding collector-emitter regions 112 and 120. Furthermore, in the example system, shallow P+ contact doping provides ohmic contact from base contact regions 110 and 118 to the corresponding base regions 114 and 122. In this example, a dielectric-filled trench 124 provides lateral separation between the base contact regions and the collector-emitter contact regions. It should be noted that PNP-type B-TRAN devices can also be considered; however, to avoid making the discussion too lengthy, PNP-type B-TRAN devices are not specifically shown.

[0057] In the example, the various structures and doping associated with the upper side 102 are intended to be mirror images of the various structures and doping associated with the lower side 104. However, in some cases, the various structures and doping associated with the upper side 102 are constructed at different times than those on the lower side 104, and therefore slight differences in structure and doping may exist between the two sides. These differences may be attributed to manufacturing tolerances, but they will not adversely affect the operation of the device as a bidirectional double-base bipolar junction transistor. To describe the operation of the example B-TRAN device, the specification now turns to an example model of the B-TRAN device along with a simplified driver circuit.

[0058] Figure 2 Electrical schematics of an example model of B-TRAN, along with electrical schematics of a conceptual driver circuit. Specifically, Figure 2 A model 200 of the B-TRAN is shown, along with an upper driver section 202 for the B-TRAN and a lower driver section 204 for the B-TRAN. First, turning to model 200, the example model 200 defines the upper collector-emitter 112 and the upper base 114 (although in...). Figure 2In the middle, the upper base 114 is shown on the upper left). The driver section 202 is coupled to the upper collector-emitter 112 and the upper base 114. The example model 200 further defines the lower collector-emitter 120 and the lower base 122 (although in Figure 2 In the middle, the lower base 122 is shown on the upper right). The driver 204 is coupled to the lower collector-emitter 120 and the lower base 122.

[0059] Internally, instance model 200 includes a first NPN transistor 206 having an emitter E1 coupled to the upper collector-emitter 112, a collector C1 coupled to the lower collector-emitter 120, and a base B1 defining the upper base 114. Instance model 200 further includes a second NPN transistor 208 having an emitter E2 coupled to the lower collector-emitter 120, a collector C2 coupled to the upper collector-emitter 112, and a base B2 defining the lower base 122. Bases B1 and B2 are coupled together by series resistors 210 and 212 (representing drift regions of the host substrate), which define a node 214 between them. A diode 216 is coupled between node 214 and the upper collector-emitter 112, and the diode 216 represents the upper PN junction between the upper base 114 and the upper collector-emitter 112. Similarly, diode 218 is coupled between node 214 and lower collector-emitter 120, and diode 218 represents the lower PN junction between lower base 122 and lower collector-emitter 120.

[0060] Externally, model 200 includes an electrically controlled switch 222 (hereinafter referred to as switch 222) with a first lead coupled to the upper collector-emitter 112 and a second lead coupled to the upper base 114. Example switch 222 is shown as a single-pole, single-throw switch in an open or non-conductive configuration, but in practice, switch 222 could be a field-effect transistor (FET). Therefore, when switch 222 is conductive, the upper base 114 is coupled to the upper collector-emitter 112. Example driver 202 further includes a charge carrier source 220, illustratively shown as a battery. Charge carrier source 220 has a negative lead coupled to the upper collector-emitter 112. Another electrically controlled switch 224 (hereinafter referred to as switch 224) has a first lead coupled to the positive terminal of charge carrier source 220 and a second lead coupled to the upper base 114. Example switch 224 is shown as a single-pole, single-throw switch, but in practice, switch 224 could be a FET. Therefore, when switch 224 is conductive, charge carrier source 220 is coupled between upper collector-emitter 112 and upper base 114.

[0061] Still referencing Figure 2The electrically controlled switch 228 (hereinafter referred to as switch 228 only) has a first lead coupled to the lower collector-emitter 120 and a second lead coupled to the lower base 122. Example switch 228 is shown as a single-pole, single-throw switch, but in practice, switch 228 can be a FET. Therefore, when switch 228 is conducting, the lower base 122 is coupled to the lower collector-emitter 120. Example driver 204 further includes another charge carrier source 226, illustratively shown as a battery. Charge carrier source 226 has a negative lead coupled to the lower collector-emitter 120. Electrically controlled switch 230 (hereinafter referred to as switch 230 only) has a first lead coupled to the positive terminal of battery 226 and a second lead coupled to the lower base 122. Switch 230 is shown as a single-pole, single-throw switch, but in practice, switch 230 can be a FET. Therefore, when switch 230 is conductive, charge carrier source 226 is coupled between lower collector-emitter 120 and lower base 122.

[0062] Figure 3A An example model and driver circuitry are shown in the non-conductive mode of the B-TRAN. Non-conductive switches are shown as open circuits, while conductive switches are shown as short circuits. Specifically, an external voltage is applied across the upper collector-emitter 112 and the lower collector-emitter 120, with positive polarity at the upper collector-emitter 112. Figure 3A In the configuration shown, switch 228 is conductive and all other switches 228 are non-conductive. The conductive switch 228 directly couples the lower collector-emitter 120 to the lower base 122, effectively bypassing or shorting the lower PN junction illustrated by diode 218 and ensuring that the upper PN junction illustrated by diode 216 is reverse-biased. Furthermore, the upper base 114 is electrically floating. Therefore, no current flows through the B-TRAN and the entire B-TRAN is non-conductive for the applied polarity. Therefore, Figure 3A The arrangement can be referred to as the shutdown mode.

[0063] Now consider making B-TRAN conductive. Figure 3BAn example model and driver circuitry arranged for an optional diode conduction mode are shown. Specifically, to initially make the B-TRAN conduct in the shown polarity under an external voltage, switch 222 is made conductive and switch 228 is made non-conductive. Switches 224 and 230 remain non-conductive. In the shown configuration, the upper PN junction illustrated by diode 216 is bypassed, and the lower PN junction illustrated by diode 218 is forward biased. Therefore, in the so-called diode conduction mode, current flows from the upper collector-emitter 112 and the upper base 114 to the lower collector-emitter 120. When in use, the diode conduction mode can last for a predetermined period of time (e.g., about 1 μs to 5 μs, including the terminal value). In the shown configuration, the forward voltage drop is relatively low. In one example, at a current density of about 200 A / cm², the forward voltage drop is about 1.0 V. However, the forward voltage drop can be driven even lower.

[0064] Figure 3C This demonstrates an example model and driver circuit arranged for conduction. In the case where diode conduction mode is used, to further reduce the forward voltage drop across the B-TRAN, switch 222 is de-conducted, switch 224 is conducted, and switches 228 and 230 remain de-conducted. In the case where diode conduction mode is omitted, from the off-mode ( Figure 3A Switch 228 is deconductive, switch 224 is conductive, and switches 222 and 230 remain nonconductive. In the illustrated configuration, charge carrier source 220 is coupled between upper collector-emitter 112 and upper base 114. As a result, the voltage on upper base 114 is driven higher than the voltage on upper collector-emitter 112. Although lower base 122 is not externally connected and is electrically floating, it is internally connected via the drift region of the B-TRAN, and therefore lower base 122 can (depending on the instance voltage of charge carrier source 220) be driven higher than the voltage on upper collector-emitter 112. Thus, the two instance transistors of model 200 are partially or fully conductive, and this arrangement is referred to as the transistor on-mode. Furthermore, charge carriers (holes in this case) are injected into upper base 114. The combination of additional holes in the drift region increases the conductivity of the drift region, which reduces the forward voltage drop across the B-TRAN device. In one example, when a voltage of about 0.7V to about 1.0V (inclusive of the terminal value) is applied across the upper collector-emitter 112 and the upper base 114 (e.g., through the charge carrier source 220), the forward voltage drop can be reduced to between about 0.1V and about 0.2V (inclusive of the terminal value). The discussion now turns to make the B-TRAN non-conductive.

[0065] Figure 3DExample models and driver circuits arranged for an optional pre-shutdown mode are shown. Specifically, in some examples of the process of starting to deconduct the B-TRAN (e.g., for a 1200V device, approximately 0.1μs to 5μs before complete shutdown), switches 222 and 228 are turned on, and switch 224 is turned off. Switch 230 remains off. Turning switch 224 off and turning switch 222 on stops the injection of charge carriers from charge carrier source 220 into the drift region. Furthermore, turning switch 228 on causes a large current draw or flow from the drift region. It is thus determined that these actions remove charge carriers from the drift region, desaturating the B-TRAN and increasing the forward voltage drop. Therefore, this configuration is referred to as the pre-shutdown mode. In one example, in the pre-shutdown mode, the forward voltage drop can rise to between approximately 0.9V and 3V, including the terminal values. Then, by reimplementation... Figure 3A The arrangement, for instance polarity of the external voltage, can make Figures 3A to 3D The example shown is an example where the B-TRAN is completely non-conductive. In other cases, particularly when the B-TRAN conduction abruptly ends (e.g., circuit breaker service), the pre-shutdown mode can be omitted, and the driver circuit can directly switch the B-TRAN from the transistor's on-mode ( Figure 3C Switch to shutdown mode. Figure 3A ).

[0066] about Figures 3A to 3D The example is for the case where an external voltage applies a positive voltage to the upper collector-emitter 112. However, the example B-TRAN is a symmetrical device, and now it is understood how to control the current flow through the B-TRAN with the example polarity, and then it is understood how to control the current flow in the opposite direction. In this case where the current flow is in the opposite direction, charge carrier source 226 and switch 230 are used to exclude charge carrier source 220 and switch 224.

[0067] Figure 4 This plot shows the voltage drop across the B-TRAN over time. Specifically, Figure 4 Shows the forward voltage drop (Vf) across instance B-TRAN during a single conduction cycle, and labeled with respect to... Figures 3A to 3D The various modes discussed. Between instance times t0 and t1, the B-TRAN may be completely non-conductive and therefore off. Therefore, the voltage across the B-TRAN during the off-time or off-mode can be the applied voltage across the collector-emitter junction (e.g., 1200V). Between instance times t1 and t2, the B-TRAN device can be placed in an optional diode-on mode, as discussed regarding... Figure 3BAs discussed above. During the optional diode conduction mode, the forward voltage drop across the B-TRAN can be approximately 1.0V. Between example times t2 and t3, the B-TRAN device can be placed in transistor conduction mode, as discussed above. Figure 3C As discussed. During the transistor's on-mode, based on the voltage applied between the collector-emitter junction (acting as the collector) and the base on the same side of the B-TRAN, the forward voltage drop across the B-TRAN device can be approximately 0.2V to 0.3V, including the terminal value. Between instance times t3 and t4, the B-TRAN device can be placed in an optional pre-shutdown mode, as discussed regarding Figure 3D As discussed. During the optional pre-shutdown mode, the forward voltage drop across the B-TRAN device can rise to between 0.9V and 3.0V. Finally, after time t4, the B-TRAN device is again arranged for non-conductivity, as... Figure 3A As shown in the image.

[0068] The inventors of this specification have determined that higher overall efficiency can be achieved. That is, while increasing the base voltage relative to its collector-emitter configuration (which acts as the collector) reduces the forward voltage drop across the device, this increased base voltage relative to its collector-emitter configuration also increases the time required to transition the B-TRAN to a non-conductive state, and therefore also increases switching losses. In other words, while injecting charge carriers into the base associated with the collector-emitter configuration (which acts as the collector) reduces the forward voltage drop, the injection of charge carriers increases turn-off time and associated losses.

[0069] Various examples involve controlling the forward voltage drop across the B-TRAN such that it is low (e.g., 0.1V to 0.2V, including the terminal value) for most of the conduction cycle, and increases (e.g., to between 0.4V and 1.0V, including the terminal value) for a predetermined period before the end of the conduction cycle (e.g., about 4μs) and before the pre-shutdown mode. Regarding conductivity, various examples involve controlling the conductivity through the B-TRAN such that it is high for most of the conduction cycle and decreases for a predetermined period before the end of the conduction cycle. Increasing the forward voltage drop near the end of the conduction cycle slightly increases the conduction losses across the B-TRAN; however, increasing the forward voltage drop near the end of the conduction cycle reduces the switching losses when transitioning the B-TRAN to a non-conductive state. The net effect is a better overall operating efficiency of the B-TRAN.

[0070] Figure 5 This plot shows the voltage drop across the B-TRAN over time. Specifically, Figure 5This demonstrates the voltage drop across the instance B-TRAN during a single conduction cycle, using both optional diode on-mode and optional pre-off-mode. Between instance times t0 and t1, the B-TRAN can be completely non-conductive and therefore off. Therefore, the voltage across the B-TRAN during the off-mode can be the applied voltage (e.g., 1200V). Between instance times t1 and t2, the B-TRAN device can be placed in the optional diode on-mode, as shown regarding... Figure 3B As discussed above. During diode conduction mode, the forward voltage drop across the B-TRAN can drop to approximately 1.0V. Between example times t2 and t3, the B-TRAN can be placed in transistor conduction mode, as discussed above. Figure 3C As discussed. During the transistor's on-mode, based on the voltage applied between the collector-emitter junction (acting as the collector) and the base on the same side of the B-TRAN, the forward voltage drop across the B-TRAN can decrease to approximately 0.2V. However, compared to... Figure 4 Unlike other methods and systems, in the example method and system, before transitioning to the optional pre-shutdown mode or directly to the shutdown mode, the B-TRAN is placed in the transistor on-mode, where the forward voltage drop is between the forward voltage drop associated with device saturation and the forward voltage drop associated with diode on-mode. Therefore, between example times t3 and t4, the B-TRAN remains in transistor on-mode, but the reduction in saturation causes the forward voltage to increase (e.g., to between 0.2V and 1.0V, including the terminal value, and in many cases approximately 0.6V). Subsequently, and between example times t4 and t5, the example B-TRAN enters the optional pre-shutdown mode, and the forward voltage drop across the B-TRAN device can again rise to between 0.9V and 3.0V. Finally, after time t5, the B-TRAN device is again arranged for non-conductivity, as... Figure 3A As shown in the image.

[0071] Based on the state of the driver driving the B-TRAN, the time period between t2 and t4 can be conceptually divided into two time periods. As an example, consider an arrangement where the upper collector-emitter has been applied with a positive polarity voltage. Between time periods t2 and t3, the driver may be injecting charge carriers into the upper base at a first rate. Injecting charge carriers at the first rate causes current to flow through the transistor from the upper collector-emitter to the lower collector-emitter, and this current flow results in a first positive voltage drop as shown between time periods t2 and t3. According to the example system, the charge carrier injection rate can be changed within a predetermined time period (e.g., approximately 4 μs) before the end of the conduction cycle, and in this example, the injection of charge carriers into the upper base is changed to a second rate lower than the first rate. Injecting charge carriers at the second rate results in a second positive voltage drop higher than the first positive voltage drop, as shown between time periods t3 and t4. Thereafter, an optional pre-shutdown mode can be implemented, followed by a shutdown mode after time t5, as shown. The instruction manual now turns to an example switching device designed and constructed to implement the example method.

[0072] Figure 6 Partial block diagrams and partial electrical schematics of a switch assembly according to at least some embodiments are shown. Specifically, example switch assembly 600 includes a B-TRAN 100 and a driver 602. In an NPN configuration, the B-TRAN 100 is shown by example circuit symbols having two emitters and two bases. The circuit symbols show an upper collector-emitter 112, an upper base 114, a lower collector-emitter 120, and a lower base 122. The upper collector-emitter 112 is coupled to an upper conductive terminal 604 of the switch assembly 600. The lower collector-emitter 120 is coupled to a lower conductive terminal 606 of the switch assembly 600. Example driver 602 defines an upper base terminal 608 coupled to the upper base 114, an upper conductive terminal 610 coupled to the upper collector-emitter 112, a lower base terminal 612 coupled to the lower base 122, and a lower conductive terminal 614 coupled to the lower collector-emitter 120.

[0073] Example driver 602 includes a controller 616, an electrical isolator 618, and an isolation transformer 620. To place the B-TRAN 100 into various conductive and non-conductive states, example driver 602 includes multiple electrically controlled switches and sources of charge carriers for injection into the upper base 114 and lower base 122. Specifically, driver 602 includes switch 222 having a first lead coupled to the upper collector-emitter 112, a second lead coupled to the upper base 114, and a control input coupled to the controller 616. As previously described, example switch 222 is shown as a single-pole, single-throw switch; however, switch 222 can actually be a field-effect transistor (FET), where the control input is the gate of the FET. Therefore, when switch 222 is made conductive by asserting the control input of switch 222, the upper base 114 is coupled to the upper collector-emitter 112.

[0074] The driver 602 further includes a charge carrier source 622, illustratively shown as a battery. The charge carrier source 622 has a negative lead coupled to the upper collector-emitter 112. Another electrically controlled switch 624 (hereinafter, switch 624 only) has a first lead coupled to the positive terminal of the charge carrier source 622, a second lead coupled to the upper base 114, and a control input coupled to the controller 616. The example switch 624 is also shown as a single-pole, single-throw switch, but in practice, switch 624 could be a FET, where the control input is the gate of the FET. Therefore, when switch 624 is conductive, the charge carrier source 622 is coupled between the upper collector-emitter 112 and the upper base 114. The driver 602 further includes another charge carrier source 626, illustratively shown as a battery. The charge carrier source 626 has a negative lead coupled to the upper collector-emitter 112. Another electrically controlled switch 628 (hereinafter referred to as switch 628 only) has a first lead coupled to the positive terminal of the charge carrier source 626, a second lead coupled to the upper base 114, and a control input coupled to the controller 616. Example switch 628 is also shown as a single-pole, single-throw switch, but in practice, switch 628 can be a FET, where the control input is the gate of the FET. Therefore, when switch 628 is conducting, the charge carrier source 626 is coupled between the upper collector-emitter 112 and the upper base 114.

[0075] Turning now to the lower side of B-TRAN 100, example driver 602 further includes a switch 228 having a first lead coupled to the lower collector-emitter 120, a second lead coupled to the lower base 122, and a control input coupled to controller 616. As above, example switch 228 is shown as a single-pole, single-throw switch, but in practice, switch 228 could be a FET, where the control input is the gate of the FET. Therefore, when switch 228 is made conductive by asserting the control input of switch 228, the lower base 122 is coupled to the lower collector-emitter 120. Driver 602 further includes a charge carrier source 630, illustratively shown as a battery. Charge carrier source 630 has a negative lead coupled to the lower collector-emitter 120. Another electrically controlled switch 632 (hereinafter referred to as switch 632 only) has a first lead coupled to the positive terminal of the charge carrier source 630, a second lead coupled to the lower base 122, and a control input coupled to the controller 616. Example switch 632 is also shown as a single-pole, single-throw switch, but in practice, switch 632 can be a FET, where the control input is the gate of the FET. Therefore, when switch 632 is conductive, the charge carrier source 630 is coupled between the lower collector-emitter 120 and the lower base 122.

[0076] The driver 602 further includes another charge carrier source 634, illustratively shown as a battery. The charge carrier source 634 has a negative lead coupled to the lower collector-emitter 120. Another electrically controlled switch 636 (hereinafter, switch 636 only) has a first lead coupled to the positive terminal of the charge carrier source 634, a second lead coupled to the lower base 122, and a control input coupled to the controller 616. The example switch 636 is also shown as a single-pole, single-throw switch, but in practice, switch 636 could be a FET, where the control input is the gate of the FET. Therefore, when switch 636 is conductive, the charge carrier source 634 is coupled between the lower collector-emitter 120 and the lower base 122.

[0077] Controller 616 defines a control input 638 and control outputs 640, 642, 644, 646, 648, and 650, respectively, coupled to the control inputs of switches 628, 624, 222, 228, 632, and 636. When control input 638 is asserted, controller 616 is designed and configured to place B-TRAN 100 in a conductive state by controlling the various switches. Conversely, when control input 638 is deasserted, controller 616 is designed and configured to place B-TRAN 100 in a non-conductive state by controlling the various switches. The arrangement of B-TRAN 100 in the non-conductive state depends on the polarity of the applied voltage. Therefore, example controller 616 further defines a polarity input 652 that receives a Boolean indication of the applied polarity. In example driver 602, comparator 654 has a first input coupled to upper conductive terminal 604 (connection shown by bubble "A") and a second input coupled to lower conductive terminal 606. Comparator 654 defines the comparison output coupled to the polarity input 652. Although Figure 6 The first and second inputs are shown to be directly coupled to their respective conductive terminals, but in practice, the voltage across B-TRAN 100 in its non-conductive state can be large (e.g., 1200V), and therefore each of the first and second inputs can be coupled to its respective conductive terminal via a corresponding voltage divider circuit. In a further embodiment, the applied polarity can be determined by a Boolean signal sent by external systems and devices to the switching assembly 600 and the trans-isolator 618.

[0078] As discussed above, transitioning B-TRAN 100 from a non-conductive state to a conductive state and then back to a non-conductive state can be a multi-step process. Therefore, in some instances, controller 616 can be configured to read control input 638 and polarity input 652 and drive control outputs to implement, for example, regarding... Figure 5 The individual circuit components for state or mode transitions of the B-TRAN 100 discussed include application-specific integrated circuits (ASICs), microcontrollers with control software, reduced instruction set computers (RISCs), digital signal processors (DSPs), processes with control software, processors with control software, programmable logic devices (PLDs), or field-programmable gate arrays (FPGAs).

[0079] In the example system, the switch assembly 600 is electrically floating. To receive control input 638 in the electrical domain of the switch assembly 600, the example driver 602 implements an electrical isolator 618. The example electrical isolator 618 can take any suitable form, such as an optocoupler or a capacitive isolation device. Regardless of the precise nature of the electrical isolator 618, external control signals (e.g., Boolean signals indicating that B-TRAN 100 should be placed in a conductive state when asserted) can be coupled to the control input 656 of the electrical isolator 618. The electrical isolator 618 then passes the control signal through to the electrical domain of the switch assembly 600. In this example, the external control signal is passed through to become the control input 638 of the controller 616.

[0080] Turning now to isolation transformer 620. Various devices within the switching assembly 600 can utilize operating power. For example, controller 616 can utilize bus voltage and power to implement various operating modes of B-TRAN. Furthermore, charge carrier sources within the system can be implemented as individual voltage sources in the form of switching power converters, or individual current sources can be implemented using switching power converters. Switching power converters implementing charge carrier sources can utilize bus voltage and power. Isolation transformer 620 is provided to provide operating power within the electrical domain of switching assembly 600. An external system (not specifically shown) can provide an alternating current (AC) signal (e.g., 15V AC) across the primary leads 658 and 660 of isolation transformer 620. Isolation transformer 620 generates AC voltage on secondary leads 662 and 664. The AC voltage on the secondary side of isolation transformer 620 can be provided to AC-DC power converter 668, which rectifies the AC voltage and transmits it through bus voltage V. BUS Power is provided relative to the common terminal 670 (e.g., 3.3V, 5V, 12V). The power provided by the AC-DC power converter 668 can be used by various components of the switching assembly 600. In other cases, multiple isolation transformers may be present (e.g., one on each side of the B-TRAN). Alternatively, a single isolation transformer with multiple secondary windings can be used.

[0081] As an example, consider the case where the applied voltage across conductive terminals 604 and 606 has a positive polarity at the upper conductive terminal 604. Further consider the case where the control signal applied to control input 656 of the isolator 618 is deasserted, and therefore the control signal applied to control input 638 of the controller 616 is also deasserted. Based on the deasserted state of control input 638, the controller 616 is designed and configured to take into account the applied polarity (as read by the controller 616 via polarity input 652) placing B-TRAN 100 in a non-conductive state. Therefore, in the example arrangement, the controller 616 can be designed and configured to assert control output 646 to conduct switch 228, and all other control outputs are deasserted to deconduct all other switches, causing the upper base 114 to float.

[0082] In the example arrangement where the polarity is still positive at the upper conductive terminal 604, it is now considered that the control signal applied to the control input 656 of the electrical isolator 618 is asserted, and therefore the control signal applied to the control input 638 of the controller 616 is asserted. Based on this assertion, in Figure 6In the example switch assembly 600, the controller 616 can be designed and configured to first place the B-TRAN 100 in an optional diode conduction mode by canceling assertion control output 646 (thus deconducting switch 228) and assertion control output 644 (thus conducting switch 222). Conducting switch 222 couples the upper collector-emitter 112 to the upper base 114. This arrangement results in current flow through the B-TRAN 100 and a forward voltage drop comparable to the diode conduction mode. When used, the diode conduction mode can last for a predetermined period of time (e.g., from about 0.1 μs to 5 μs). The controller 616 can then be designed and configured to place the B-TRAN in a transistor conduction mode by injecting charge carriers into the upper base 114 at a first rate. During the transition from diode conduction mode, controller 616 can be designed and constructed to cancel assertion control output 644 (making switch 222 non-conductive) and, after ensuring switch 222 is non-conductive for a sufficient period of time, assert control output 642 (making switch 624 conductive). In the absence of diode conduction mode, controller 616 can be designed and constructed to cancel assertion control output 646 (thus making switch 228 non-conductive) and assert control output 642 (thus making switch 624 conductive). In any case, making switch 624 conductive couples charge carrier source 622 between upper collector-emitter 112 and upper base 114. In some example systems, charge carrier source 622 generates a controlled voltage of approximately 1.0V applied across upper collector-emitter 112 and upper base 114, which causes current to flow in upper base 114. As discussed above, in the arrangement, the current flow to the upper base 114 increases the number of charge carriers in the drift region of the B-TRAN 100, which drives the B-TRAN 100 to a saturated state.

[0083] In many cases, the control signal applied to the switching assembly 600 to control the conduction state of the B-TRAN 100 is a periodic signal with a relatively stable frequency. For example, when the switching assembly 600 is used in a power converter between a solar panel generating direct current (DC) and an AC power source, the control signal applied to the switching assembly 600 may have a fixed frequency (e.g., 50 Hz, 60 Hz) related to the frequency of the AC power source and a duty cycle proportional to the amount of solar energy collected by the solar panel. Therefore, the length of each conduction cycle can be relatively stable over a long period of time (e.g., minutes to hours). It is thus concluded that in many cases, the controller 616 may be able to predict when the control signal will be deprecated, and therefore when the conduction cycle may end. In such cases, during a predetermined period of time before the end of the current conduction cycle, the example controller 616 may be designed and constructed to increase the forward voltage drop and correspondingly reduce the conductivity through the B-TRAN 100 by injecting charge carriers into the upper base 114 at a second, lower rate. Figure 6 In one example, to inject charge carriers at a lower rate, controller 616 may be designed and constructed to de-assert control output 642 (making switch 624 non-conductive) and assert control output 640 (making switch 628 conductive). Conducting switch 628 couples charge carrier source 626 between upper collector-emitter 112 and upper base 114. In some example systems, charge carrier 626 generates a controlled voltage of approximately 0.5V applied across upper collector-emitter 112 and upper base 114, resulting in a reduced current flow to upper base 114 compared to the higher voltage associated with example charge carrier source 622. This reduced current flow to upper base 114 decreases the number of charge carriers in the drift region of B-TRAN 100, driving B-TRAN 100 into a less saturated state (compared to previous saturation). Although the increased forward voltage drop and decreased conductivity increase conduction losses, the increased conduction losses are largely offset by the reduced switching losses of the B-TRAN 100 due to the reduced switching time. In one instance, when the forward voltage is increased in the second part of the transistor's conduction mode, the forward voltage drop can increase by between 10% and 20% of the lower forward voltage drop, including the terminal value. Regarding charge carrier injection, injecting charge carriers at a second, lower rate can reduce the charge carrier injection rate by 40% or more, and in one instance, by approximately 50%.

[0084] Subsequently, instance controller 616 can switch B-TRAN 100 to an optional pre-shutdown mode. Specifically, instance controller 616 can be designed and constructed to cancel assertion control output 640 (making switch 628 non-conductive) and assertion control outputs 644 and 646 (making switches 222 and 228 conductive). Conducting switches 222 and 228 will directly couple the upper collector-emitter 112 to the upper base 114 and the lower collector-emitter 120 to the lower base 122, respectively. When the control signal applied to control input 656 is canceled, indicating that B-TRAN 100 should be completely non-conductive, the instance controller can place B-TRAN 100 in a shutdown mode, which is accomplished in instance polarity by canceling assertion control output 646 (making switch 228 non-conductive) and asserting control output 644 (making switch 222 conductive). In cases where a pre-shutdown mode is not used (e.g., circuit breaker operation), controller 616 can be designed and constructed to directly transition the B-TRAN from transistor on-mode to off-mode by canceling assertion control output 640 (making switch 628 non-conductive) and assertion control output 646 (making switch 228 conductive). Making switch 628 non-conductive causes the upper base 114 to float, and making switch 228 conductive shorts the lower collector-emitter 120 to the lower base 122.

[0085] about Figure 6 The example operation discussed concerns the assumed polarity applied by an external voltage. However, similarly, example B-TRAN 100 is a symmetrical device, and it is now understood how to control the injection of charge carriers at different rates during transistor conduction mode, followed by understanding how to control the current flow in opposite directions relative to charge carrier sources 630 and 634 and their corresponding switches 632 and 636.

[0086] Regarding the two injection modes of charge carriers, Figure 6 The switch assembly 600 utilizes separate and independent charge carrier sources associated with each side. For example, charge carrier sources 622 and 626 are illustratively used on the upper side, and charge carrier sources 630 and 634 are illustratively used on the lower side. However, in other cases, each side of the B-TRAN 100 may use a single but variable charge carrier source to drive the charge carriers.

[0087] Figure 7 Partial block diagrams and partial electrical schematic diagrams of a switch assembly according to at least some embodiments are shown. Specifically, Figure 7 The example shown is B-TRAN 100, and the example driver 602 includes a controller 616. Driver 602 will also have an isolation transformer, AC-DC power converter, electrical isolator, and comparator for polarity determination, but from... Figure 7Those components are omitted to avoid making the diagram too complex. Figure 7 The driver 602 includes an adjustable charge carrier source 700, illustratively shown as a battery-like adjustable voltage source associated with the upper side of the B-TRAN 100. The illustrative charge carrier source 700 may actually be implemented as an individual voltage source in the form of a switching power converter with a controllable or adjustable output voltage, or may be implemented as an individual current source using a switching power converter with a controllable or adjustable output. The charge carrier source 700 has a negative lead coupled to the upper collector-emitter 112, a positive lead coupled to the electronically controlled switch 624, and a setpoint input 702. Thus, when the switch 624 is conductive, the charge carrier source 700 is coupled between the upper collector-emitter 112 and the upper base 114. In this example, controller 616 defines a setpoint output 704 (e.g., an analog or digital output) coupled to setpoint input 702, and therefore controller 616 is designed and constructed to control the injection rate of charge carriers generated by charge carrier source 700 by controlling setpoint output 704.

[0088] Figure 7 The driver 602 also includes an adjustable charge carrier source 706, illustratively shown as a battery-like adjustable voltage source associated with the lower side of the B-TRAN 100. The illustrative charge carrier source 706 may actually be implemented as an individual voltage source in the form of a switching power converter with a controllable or adjustable output voltage, or it may be implemented as an individual current source using a switching power converter with a controllable or adjustable output. The charge carrier source 706 has a negative lead coupled to the lower collector-emitter 120, a positive lead coupled to the electronically controlled switch 632, and a setpoint input 708. Thus, when the switch 632 is conductive, the charge carrier source 706 is coupled between the lower collector-emitter 120 and the lower base 112. In these examples, controller 616 defines a setpoint output 710 (e.g., an analog or digital output) coupled to setpoint input 708, and thus controller 616 is designed and constructed to control the injection rate of charge carriers generated by charge carrier source 706 by controlling setpoint output 710.

[0089] As an example, consider the case where the applied voltage across conductive terminals 604 and 606 has a positive polarity at the upper conductive terminal 604. Further consider the case where the control signal applied to control input 638 is de-asserted. Based on the de-asserted state of control input 638, controller 616 is designed and constructed to assume that B-TRAN100 is placed in a non-conductive state due to the applied polarity. Therefore, in the example arrangement, controller 616 is designed and constructed to assert control output 646 to conduct switch 228, and all other control outputs are de-asserted to make all other switches non-conductive.

[0090] Now consider the control signal applied to the control input 638 of the controller 616, which is asserted to indicate that the B-TRAN 100 should be made conductive. Based on this assertion, in Figure 7 In the example switch assembly 600, the controller 616 can be designed and configured to first place the B-TRAN 100 in an optional diode conduction mode by canceling the assertion control output 646 (thus deconducting switch 228) and the assertion control output 644 (thus conducting switch 222). Conducting switch 222 results in current flow through the B-TRAN 100 and a forward voltage drop equivalent to that in the diode conduction mode. After a predetermined time period, the controller 616 can be designed and configured to switch the B-TRAN 100 into a transistor conduction mode by injecting charge carriers into the upper base 114 at a first rate. Figure 7In this example, to inject charge carriers at a first rate, controller 616 may be designed and constructed to de-assert control output 644 (making switch 222 non-conductive) and, after ensuring a sufficient amount of time that switch 222 is non-conductive, assert control output 642 (making switch 624 conductive). Furthermore, in this example system, controller 616 may drive a setpoint signal to setpoint output 704 and thus to setpoint input 702 of charge carrier source 700. Driving the setpoint signal and making switch 624 conductive will inject charge carriers into upper base 114 at a first rate. In the absence of the optional diode conduction mode, the example controller 616 can be designed and constructed to directly switch the B-TRAN 100 from the off mode to the transistor on mode via the following steps: canceling the assertion control output 646 (thus deconducting switch 228), asserting the control output 642 (conducting switch 624), and driving the setpoint signal to the setpoint output 704 and thus the setpoint input 702 of the charge carrier source 700. However, in some example systems, a controlled voltage of approximately 1.0V is applied to the charge carrier source 700 across the upper collector-emitter 112 and the upper base 114, resulting in current flow to the upper base 114. As discussed above, the current flow to the upper base 114 increases the number of charge carriers in the drift region of the B-TRAN 100, driving the B-TRAN 100 into saturation.

[0091] As above, controller 616 predicts the time when the control signal applied to the control input will be canceled, and therefore the time when the conduction cycle may end. In such cases, during a predetermined period before the end of the current conduction cycle, instance controller 616 can be designed and constructed to increase the forward voltage drop by injecting charge carriers into the upper base 114 at a second, lower rate, and correspondingly reduce the conductivity through B-TRAN 100. Figure 7 In some examples, to inject charge carriers at a lower rate, the controller 616 may be designed and constructed to drive a second, different setpoint signal to the setpoint output 704 and thus the setpoint input 702 of the charge carrier source 700. In some example systems, a controlled voltage of approximately 0.5V is applied across the upper collector-emitter 112 and the upper base 114, resulting in a reduced current flow to the upper base 114 compared to a higher voltage. This reduced current flow to the upper base 114 decreases the number of charge carriers in the drift region of the B-TRAN 100, driving the B-TRAN 100 to a less saturated state (compared to previous saturation). Although the increased forward voltage drop and reduced conductivity increase conduction losses, the increased conduction losses are largely offset by the reduction in switching losses.

[0092] about Figure 7The example operation discussed concerns the assumed polarity applied by an external voltage. However, similarly, example B-TRAN 100 is a symmetrical device, and it is now understood how to control the injection of charge carriers at different rates during transistor conduction mode, and subsequently, how to use a controllable charge carrier source to control the current flow in the opposite direction.

[0093] The various examples discussed so far reduce switching losses by increasing the forward voltage drop during a predetermined period at the end of the conduction cycle, with the net effect being an increase in the overall efficiency of the B-TRAN. In addition to or instead of such techniques, further examples reduce switching time and thus switching losses by actively injecting charge carriers into the drift region during the state transition from a non-conducting or off mode to a conducting mode (e.g., diode on mode, transistor on mode, and / or pre-off mode). Furthermore, other examples reduce switching time and thus switching losses by actively extracting charge carriers from the drift region during the state transition from any conducting mode (e.g., diode on mode, transistor on mode, and / or pre-off mode) to a non-conducting or off mode.

[0094] Figure 8 A graph showing the voltage drop over time across a B-TRAN device. Specifically, Figure 8 This demonstrates the voltage drop across an instance B-TRAN during a single conduction cycle, using both optional diode on-mode and optional pre-off-mode. Figure 8 The transition from off mode to conduction mode at time t1 is also shown by zooming in on segment 800. Figure 8 The transition from conduction mode to shutdown mode at time t5 is also shown by zooming in on segment 802. That is, a larger... Figure 8 The transitions are shown as ideal transitions occurring exactly at a specified time. However, the actual transition from the off mode (e.g., before time t1) to the conduction mode (e.g., to diode conduction mode or transistor conduction mode as shown) at time t1 requires a finite and non-zero amount of time. Similarly, the actual transition from the conduction mode to the off mode (e.g., from pre-off mode or transistor conduction mode as shown) at time t5 requires a finite and non-zero amount of time.

[0095] The inventors of this specification have discovered that the amount of time required to transition from a turn-off mode to a conduction mode can be reduced by injecting charge carriers into the drift region via the collector (C) base during the transition, and in some cases, into both the collector (C) base and the emitter (E) base. In some cases, the charge carriers are injected during the transition at a rate higher than that described above for the transistor conduction mode. Therefore, reducing the switching time reduces switching losses, and although injecting charge carriers itself requires energy, the net effect is a higher overall efficiency considering the lower switching losses. Similarly, the inventors of this specification have discovered that the amount of time required to transition from a conduction mode to a turn-off mode can be reduced by extracting charge carriers from the drift region via the collector (C) base during the transition, and in some cases, from both the collector (C) base and the emitter (E) base. Therefore, reducing the switching time reduces switching losses, and although extracting charge carriers itself requires energy, the net effect is a higher overall efficiency considering the lower switching losses. Before proceeding, it should be noted that although the example embodiments discussed below both inject charge carriers during the transition from the off mode and extract charge carriers during the transition to the off mode, in other cases, it may be possible to inject charge carriers during the transition to the conducting mode and exclude the extraction of charge carriers during the transition to the non-conducting or off mode, and vice versa.

[0096] Still referencing Figure 8 The magnified area 800 illustrates the transition from the off-mode before time t1 to the on-mode of the example diode after time t1. Again, the transition to the on-mode diode is merely illustrative, and in other cases, the transition from the off-mode can be direct to the on-mode transistor. Specifically, according to the example embodiment, the transition from the off-mode begins with the active injection of charge carriers into the base (c) at example time t1-1. The injected charge carriers affect the slope of the forward voltage drop between times t1-1 and t1-2, with a higher injection rate resulting in a steeper downward slope. In other words, the charge carrier injection rate affects the speed at which the B-TRAN transitions to the conducting mode, with a higher injection rate resulting in a faster switching time. At example time t1-2, in the example system, the injection of charge carriers associated with the transition ceases. In cases where an optional on-mode diode is used, the example system can therefore stop the injection of charge carriers and the transition to the on-mode diode configuration, as discussed above. In the absence of an optional diode conduction mode, the example system can thus stop injecting charge carriers at the rate associated with the transition and begin injecting charge carriers at the rate associated with the transistor conduction mode, as discussed above.

[0097] Similarly, regarding the transition to the turn-off mode, magnification area 802 illustrates the transition from an optional pre-turn-off mode before time t5 to an example turn-off mode after time t5. Again, the transition from the pre-turn-off mode is merely illustrative, and in other cases, the transition to the turn-off mode can proceed directly from the transistor's on-mode (any charge carrier injection method discussed above). According to the example embodiment, the transition from the conduction mode to the turn-off mode begins at example time t5-1 with the active extraction of charge carriers from the c-base (or both c-base and e-base). The extraction of charge carriers affects the slope of the forward voltage drop between times t5-1 and t5-2, with a higher extraction rate resulting in a steeper upward slope. In other words, the charge carrier extraction rate affects the speed at which the B-TRAN transitions to the turn-off mode, with a higher extraction rate resulting in a faster switching time. At example time t5-2, the example B-TRAN may be completely non-conductive. In some cases, when the B-TRAN becomes completely non-conductive, the extraction of charge carriers associated with the transition ceases. However, the timing of stopping extraction is not critical, and the arrangement for extracting charge carriers can extend a non-zero time amount into the period during which the B-TRAN is not conducting. In one instance, the arrangement for extracting charge carriers can extend until the next transition from the off-mode to the conducting mode. In other words, the arrangement for extracting charge carriers can be an alternative off-mode for the B-TRAN.

[0098] Figure 9 A partial electrical schematic diagram of a switch assembly according to at least some embodiments is shown. Specifically, Figure 9 This section showcases Example B-TRAN 100 and a portion of Example Driver 602. Driver 602 will also feature an isolation transformer, AC-DC power converter, electrical isolator, controller, and comparator, but from... Figure 9 The abbreviations omit those components. For the purposes of discussion, Figure 9 Show all as originally stated Figure 6 The present switches 222, 624, 628, 228, 632 and 636, and the example charge carrier sources 622, 626, 630 and 634.

[0099] First, refer to the upper side of B-TRAN 100. Figure 9The driver 602 further includes a charge carrier source 900, illustratively shown as a battery. The charge carrier source 900 has a positive lead coupled to the upper collector-emitter 112. Another electrically controlled switch 902 (hereinafter, switch 902 only) has a first lead coupled to the negative terminal of the charge carrier source 900, a second lead coupled to the upper base 114, and a control input coupled to a controller 616 (not shown). The example switch 902 is shown as a single-pole, single-throw switch, but in practice, switch 902 could be a FET, where the control input is the gate of the FET. Therefore, when switch 902 is conductive, the charge carrier source 900 is coupled between the upper collector-emitter 112 and the upper base 114.

[0100] Still referring to the upper side of B-TRAN 100, Figure 9 The driver 602 further includes a charge carrier source 904, illustratively shown as a battery. The charge carrier source 904 has a negative lead coupled to the upper collector-emitter 112. Another electrically controlled switch 906 (hereinafter, switch 906 only) has a first lead coupled to the positive terminal of the charge carrier source 904, a second lead coupled to the upper base 114, and a control input coupled to a controller 616 (not shown). The example switch 906 is shown as a single-pole, single-throw switch, but in practice, switch 906 could be a FET, where the control input is the gate of the FET. Therefore, when switch 906 is conductive, the charge carrier source 904 is coupled between the upper collector-emitter 112 and the upper base 114.

[0101] Now turn to the lower side of B-TRAN 100, Figure 9 The example driver 602 further includes a charge carrier source 908, illustratively shown as a battery. The charge carrier source 908 has a positive lead coupled to the lower collector-emitter 120. Another electrically controlled switch 910 (hereinafter, switch 910 only) has a first lead coupled to the negative terminal of the charge carrier source 908, a second lead coupled to the lower base 122, and a control input coupled to a controller 616 (not shown). The example switch 910 is shown as a single-pole, single-throw switch, but in practice, switch 910 could be a FET, where the control input is the gate of the FET. Therefore, when switch 910 is conductive, the charge carrier source 908 is coupled between the lower collector-emitter 120 and the lower base 122.

[0102] Still referring to the lower side of B-TRAN 100, Figure 9The example driver 602 further includes a charge carrier source 912, illustratively shown as a battery. The charge carrier source 912 has a negative lead coupled to the lower collector-emitter 120. Another electrically controlled switch 914 (hereinafter, switch 914 only) has a first lead coupled to the positive terminal of the charge carrier source 912, a second lead coupled to the lower base 122, and a control input coupled to a controller 616 (not shown). The example switch 914 is shown as a single-pole, single-throw switch, but in practice, switch 912 could be a FET, where the control input is the gate of the FET. Therefore, when switch 912 is conductive, the charge carrier source 912 is coupled between the lower collector-emitter 120 and the lower base 122.

[0103] As an example, consider the case where the applied voltage across conductive terminals 604 and 606 has a positive polarity at the upper conductive terminal 604. This applies to the turn-off mode, optional diode conduction mode, transistor conduction mode, and optional pre-turn-off mode. Figure 9 The operation of the example switch assembly 600 can be related to... Figures 3A to 3C and / or Figure 6 The same points have been discussed and will not be repeated here to avoid making the discussion too lengthy. However, when the controller 616 (not shown) switches the B-TRAN 100 from a non-conductive mode or a shutdown mode to a conductive mode (e.g., diode conduction mode or directly to transistor conduction mode), Figure 9 A further example system can inject charge carriers into the upper base 114 via switch 906 and charge carrier source 904. Specifically, when controller 616 transitions from an off-mode to a conducting state, controller 616 can be designed and constructed to assert the control input of switch 906, thereby conducting switch 906 and thus coupling charge carrier source 904 between the upper base 114 and the upper collector-emitter 112. The polarity of charge carrier source 904 injects charge carriers (holes in this case) into the drift region through upper base 114, achieving a faster transition to the conducting state compared to, for example, shorting the upper collector-emitter 112 to the upper base 114. In terms of the slope of the forward voltage drop, the example polarity of charge carrier source 904 increases the downward slope of the forward voltage drop (see, for example, Figure 8 The amplification region 800 reduces switching time and thus switching losses. In an example, the charge carrier source 904 can be a voltage source (e.g., between 5.0V and 15V, including the terminal values), and injecting charge carriers can reduce the time to transition from the off mode to the conduction mode by approximately 0.5μs to 2μs, including the terminal values, compared to applying diode conduction mode or directly shifting to transistor conduction mode.

[0104] Now, considering the example of positive polarity at the upper conductive terminal 604, consider the transition from a conductive mode (e.g., transistor on-mode or pre-off-mode) to a non-conductive mode or off-mode. When the controller 616 (not shown) transitions the B-TRAN 100 from a conductive mode to a non-conductive mode, Figure 9 A further example system can extract charge carriers through the upper base 114 using a switch 902 and a charge carrier source 900. Specifically, when the controller 616 transitions from a conducting mode to a non-conducting mode, the controller 616 can be designed and constructed to assert the control input of the switch 902, thereby making the switch 902 conductive and thus coupling the charge carrier source 900 between the upper base 114 and the upper collector-emitter 112. The polarity of the charge carrier source 900 extracts charge carriers from the drift region through the upper base 114, achieving a faster transition to the non-conducting mode compared to, for example, making the upper base 114 electrically floated. In terms of the slope of the forward voltage drop, the example polarity of the charge carrier source 900 increases the upward slope of the forward voltage drop (see, for example, Figure 8 The amplification region 802 reduces switching time and thus switching losses. In an example, the charge carrier source 900 may be a voltage source (e.g., between 5.0V and 15V, including terminal values), and compared to an example turn-off mode in which the upper base 114 is electrically floating and the lower collector-emitter 120 is shorted to the lower base 122, extracting charge carriers can reduce the time from the conducting state to the turn-off mode by approximately 0.5μs to 2μs.

[0105] Similarly, in the case of a positive polarity at the upper conductive terminal 604, consider the transition from a conductive mode (e.g., transistor on-mode or pre-off-mode) to a non-conductive mode or off-mode. When the controller 616 (not shown) transitions the B-TRAN100 from a conductive mode to a non-conductive mode, Figure 9 A further example system can extract charge carriers via switch 910 and charge carrier source 908 through lower base 122. Specifically, when controller 616 transitions from a conducting mode to a non-conducting mode, controller 616 can be designed and constructed to assert the control input of switch 910, thereby making switch 910 conductive and thus coupling charge carrier source 908 between lower base 122 and lower collector-emitter 120. The polarity of charge carrier source 908 extracts charge carriers from the drift region through lower base 122, achieving a faster transition to non-conducting mode compared to, for example, electrically shorting lower collector-emitter 120 to lower base 122. In terms of the slope of the forward voltage drop, the example polarity of charge carrier source 908 increases the upward slope of the forward voltage drop (see, for example, Figure 8The amplification region 802 reduces switching time and thus switching losses. In an example, the charge carrier source 908 may be a voltage source (e.g., between 5.0V and 15V, including terminal values), and compared to an example turn-off mode in which the lower collector-emitter 120 is directly coupled to the lower base 122, extracting charge carriers can reduce the time from the conducting state to the turn-off mode by approximately 0.5μs to 2μs.

[0106] Similarly, in the case of a positive polarity at the upper conductive terminal 604, consider again the transition from a conductive mode (e.g., transistor on-mode or pre-off-mode) to a non-conductive mode or off-mode. When the controller 616 (not shown) transitions the B-TRAN 100 from a conductive mode to a non-conductive mode, Figure 9 A further example system can extract charge carriers through the upper base 114 and simultaneously through the lower base 122, as discussed above in the individual extraction cases.

[0107] Such as about Figure 8 This implies that the timing of stopping extraction is not critical, and the arrangement for extracting charge carriers can extend for a non-zero time amount to enter the non-conducting mode. In one instance, the arrangement for extracting charge carriers can extend until the next transition to the conducting mode. In other words, the arrangement for extracting charge carriers can be an alternative shutdown mode for B-TRAN.

[0108] about Figure 9 The example operation discussed pertains to the assumed polarity applied by an external voltage. Furthermore, however, example B-TRAN 100 is a symmetrical device, and it is now understood how charge carriers are injected during the control transition from the off mode to the conduction mode, and further understood how charge carriers are extracted during the control transition from the conduction mode to the off mode, followed by control of B-TRAN 100 in the opposite direction.

[0109] Still referencing Figure 9 In particular, regarding the charge carrier source associated with the upper side of B-TRAN 100, it should be noted that the polarity of charge carrier source 904 is the same as that of charge carrier sources 622 and 626. Figure 7 Describe an alternative arrangement in which a single, adjustable charge carrier source 700 is associated with the upper side. Now that charge carrier injection is understood to be a mechanism for reducing switching time, it is concluded that... Figure 7 The charge carrier source 700 can also be used to inject charge carriers during the transition from a shutdown mode or a non-conducting mode to a conducting mode by appropriately driving the set point to the charge carrier source 700. A similar discussion is made regarding the charge carrier source 914 and the adjustable charge carrier source 706 associated with the lower side of the B-TRAN100.

[0110] Still considering Figure 9 And especially on the upper side of B-TRAN 100, it should be noted that, although Figure 9 Four separate and distinct charge carrier sources are shown, but in this example, only one charge carrier source is used at any given time. Therefore, it is concluded that in an alternative example, a single, adjustable charge carrier source can be used in conjunction with the upper side of the B-TRAN 100 along with a suitable switching network to control the polarity of coupling the single, adjustable charge carrier source to the upper collector-emitter 112 and the upper base 114. A similar discussion applies to the lower side of the B-TRAN 100. Furthermore, considering both the upper and lower sides, where only one charge carrier source is active at any given time, all the examples discussed herein can be implemented using a single, adjustable charge carrier source and a corresponding switching network.

[0111] Figure 10 A partial electrical schematic diagram of a switch assembly according to at least some embodiments is shown. Specifically, Figure 10 The image shows a portion of instance B-TRAN 100 and instance driver 602, which is shown in abbreviations. Figure 10 Display switches 902, 906, 222, 624, 628, 910, 914, 228, 632, and 636. However, in Figure 10 In the examples, charge carrier sources 900, 904, 622, 626, 908, 912, 630 and 634 are illustratively shown as current sources rather than voltage sources or batteries. Figure 10 The operation of the example implementation and Figure 6 (No charge carrier sources 900, 904, 908, 912) or Figure 9 (Similar to optional charge carrier sources 900, 904, 908, 912). When a current source is used as the charge carrier source instead of applying and maintaining a specific voltage between the base and collector-emitter junction, the charge carrier source modulates the applied voltage to provide a constant current entering or leaving the respective base. For example, for a current source that may be active during the transistor's on-mode, the constant current setpoint could be about 20A to 30A (for a 100A B-TRAN device), but if the load current through the B-TRAN decreases, the setpoint current can also be reduced accordingly. For example, for a 30A load current, the base current could be about 5A to 20A. For the extraction case, the base current could be about 5A to 20A.

[0112] In other cases, although not specifically shown, the constant current source itself can be adjustable, and therefore variations with respect to charge carrier sources in the form of voltage sources also apply to charge carrier sources in the form of current sources.

[0113] Figure 11 A method according to at least some embodiments is illustrated. Specifically, the method begins (block 1100) and includes: injecting charge carriers into the upper base of a transistor at a first rate, the injection at the first rate causing current to flow through the transistor from the upper collector-emitter to the lower collector-emitter, and the current flow causing a first voltage drop measured across the upper and lower collector-emitters (block 1102); injecting charge carriers into the upper base at a second rate lower than the first rate during a predetermined time period prior to the end of a first conduction cycle of the transistor, the injection at the second rate causing a second voltage drop measured across the upper and lower collector-emitters, the second voltage drop being higher than the first voltage drop (block 1104); and deconducting the transistor at the end of the first conduction cycle (block 1106). Thereafter, the method ends (block 1108) and may restart in the next conduction cycle.

[0114] Many of the electrical connections in the accompanying drawings are shown as direct couplings without intermediate means, but this was not explicitly stated in the description above. However, this paragraph should serve as a precondition for the claims to refer to any electrical connection as a “direct coupling” of the electrical connection shown in the drawings without any intermediate means.

[0115] The foregoing discussion is intended to illustrate the principles and various embodiments of the invention. Once the foregoing disclosure is fully understood, many variations and modifications will become apparent to those skilled in the art. The appended claims are intended to be construed as covering all such variations and modifications.

Claims

1. A method of operating a bidirectional double-base bipolar junction transistor, the method comprising: injecting charge carriers into an upper base of the transistor at a first rate, the injection at the first rate causing a current flow through the transistor from an upper collector-emitter to a lower collector-emitter, and the current flow causing a first voltage drop measured across the upper collector-emitter and the lower collector-emitter; and then, within a predetermined period of time before a first conduction cycle of the transistor ends, injecting charge carriers into the upper base at a second rate lower than the first rate, the injection at the second rate causing a second voltage drop measured across the upper collector-emitter and the lower collector-emitter, the second voltage drop being higher than the first voltage drop; and then rendering the transistor non-conductive at the end of the first conduction cycle, then injecting charge carriers into a lower base of the transistor at a third rate, the injection at the third rate causing a current flow through the transistor from the lower collector-emitter to the upper collector-emitter, and the current flow causing a third voltage drop across the lower collector-emitter and the upper collector-emitter; then, within a predetermined period of time at the end of a second conduction cycle, injecting charge carriers into the lower base at a fourth rate lower than the third rate, the injection at the fourth rate causing a fourth voltage drop measured across the lower collector-emitter and the upper collector-emitter, the fourth voltage drop being higher than the third voltage drop; then rendering the transistor non-conductive at the end of the second conduction cycle.

2. The method of claim 1, wherein rendering the transistor non-conductive further comprises coupling a lower base of the transistor directly to the lower collector-emitter of the transistor, and extracting charge carriers from the upper base.

3. The method of claim 1, further comprising, prior to injecting charge carriers at the first rate, injecting charge carriers into the upper base at a third rate higher than the first rate, the injecting charge carriers at the third rate reducing a switching time from the non-conductive state to a conductive state of the transistor.

4. The method of claim 1, wherein injecting charge carriers through the upper base at the first rate further comprises at least one selected from a group comprising: coupling a first voltage source between the upper collector-emitter and the upper base; and coupling a first current source between the upper collector-emitter to the upper base.

5. The method of claim 1, wherein the first voltage drop is 0.2 volts or less than 0.2 volts, and the second voltage drop is greater than 0.4 volts.

6. A switch assembly comprising: a bipolar junction transistor defining an upper base, an upper collector-emitter, a lower base, and a lower collector-emitter; a driver defining an upper base terminal coupled to the upper base, an upper conductive terminal coupled to the upper collector-emitter, a lower base terminal coupled to the lower base, and a lower conductive terminal coupled to the lower collector-emitter, the driver configured to: inject charge carriers into the upper base at a first rate, the injecting the charge carriers at the first rate causing a first conductance through the transistor from the upper collector-emitter to the lower collector-emitter; predict an end of the first conductive period, and within a predetermined period of time before the end of the first conductive period, inject charge carriers into the upper base at a second rate lower than the first rate, the injecting the charge carriers at the second rate causing a second conductance through the transistor from the upper collector-emitter to the lower collector-emitter, the second conductance lower than the first conductance; and then render the transistor non-conductive at the end of the first conductive period.

7. The switch assembly of claim 6, wherein the driver further comprises: a controller; a first charge carrier source defining a first output; a first electronically-controlled switch defining a first connection coupled to the first output, a second connection coupled to the upper base, and a first control input coupled to the controller; and wherein when the driver injects charge carriers into the upper base at the first rate, the controller is configured to render the first electronically-controlled switch conductive by asserting the first control input.

8. The switch assembly of claim 7, further comprising: a second charge carrier source defining a second output, the second charge carrier source different from the first charge carrier source; a second electronically-controlled switch defining a first connection coupled to the second output, a second connection coupled to the upper base, and a second control input coupled to the controller; and wherein when the driver injects charge carriers into the upper base at the second rate, the controller is configured to render the second electronically-controlled switch conductive by asserting the second control input.

9. The switch assembly of claim 7, further comprising: a setpoint input defined by the first charge carrier source, the setpoint input coupled to the controller; and wherein when the driver injects charge carriers through the upper base at the second rate, the controller is configured to reduce the rate of charge carriers supplied by the first charge carrier source.

10. The switch assembly of claim 7, wherein the first charge carrier source is at least one selected from a group comprising: a voltage source; and a current source.

11. The switch assembly of claim 6, further comprising: a controller; a means for generating charge carriers; a first electronically-controlled switch defining a first connection coupled to the means for generating charge carriers, a second connection coupled to the upper base, and a first control input coupled to the controller; wherein when the driver injects charge carriers into the upper base at the first rate, the controller is configured to render the first electronically-controlled switch conductive by asserting the first control input. a second electrically controlled switch defining a first connection coupled to the lower collector-emitter, a second connection coupled to the lower base, and a second control input coupled to the controller; and wherein when the driver renders the transistor non-conductive, the controller is configured to: render the first electrically controlled switch conductive by asserting the first control input to extract charge carriers through the upper base; and then render the first electrically controlled switch non-conductive by de-asserting the first control input; and render the second electrically controlled switch conductive by asserting the second control input.

12. The switch assembly of claim 6, wherein the driver is further configured to inject charge carriers into the upper base at a third rate higher than the first rate prior to injecting charge carriers at the first rate, the injecting charge carriers at the third rate reducing a switching time from an off mode to a conductive state of the transistor.

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