Reversed-operation power converter startup circuit and method

Abstract

Circuits and methods for providing at least a startup voltage for reversed-operation unidirectional power converters or bi-modal power converters sufficient to power at least an auxiliary circuit of such power converters while the normal supply voltage to at least the auxiliary circuit is insufficient to enable operation of the auxiliary circuit. Embodiments of the invention utilize an initial startup charge pump circuit to create a suitable startup voltage while the normal supply voltage to the auxiliary circuit is less than a specified voltage V.sub.MIN. Embodiments of the present invention also provide additional benefits, including small size since the initial startup charge pump circuit omits the use of an inductor, and high efficiency since the initial startup charge pump circuit may be disabled when the normal supply voltage to the auxiliary circuit is equal to or greater than V.sub.MIN.

Claims

1. An initial startup charge pump circuit, configured to be coupled to a power converter that includes (1) a converter circuit configured to convert an applied voltage at a node to an output voltage at an output node and (2) an auxiliary circuit coupled to the output node and configured to provide control signals to the converter circuit, the initial startup charge pump circuit configured to be coupled to the node and output a voltage to the auxiliary circuit in part capable of enabling operation of the auxiliary circuit while the output voltage from the converter circuit is insufficient to enable operation of the auxiliary circuit; wherein the power converter is one of a bidirectional power converter or a unidirectional power converter capable of operation in a reverse configuration.

2. The invention of claim 1, wherein the initial startup charge pump circuit can be selectively disabled after the output voltage from the converter circuit to the auxiliary circuit is sufficient to enable operation of the auxiliary circuit.

3. The invention of claim 1, wherein the initial startup charge pump circuit outputs the voltage to the auxiliary circuit in response to an enable signal while the output voltage from the converter circuit to the auxiliary circuit is less than a selected minimum voltage.

4. The invention of claim 1, wherein the power converter includes a charge pump.

5. The invention of claim 1, further including a current in-rush protection circuit coupled in series between the node and the power converter, and coupled to and controlled by the voltage output by the initial startup charge pump circuit, the current in-rush protection circuit configured to limit current flow from the applied voltage for a period of time.

6. The invention of claim 1, wherein the initial startup charge pump circuit includes: (a) a charge pump oscillator having an output that includes a train of pulses; and (b) a charge pump core, coupled to the train of pulses from the charge pump oscillator and to an input voltage source, the charge pump core configured to output the voltage to the auxiliary circuit.

7. The invention of claim 1, wherein the initial startup charge pump circuit can be selectively disabled after the output voltage from the converter circuit to the auxiliary circuit is sufficient to enable operation of the auxiliary circuit and wherein the initial startup charge pump circuit can be selectively enabled if the output voltage from the converter circuit to the auxiliary circuit is less than a selected minimum voltage.

8. An initial startup charge pump circuit, configured to be coupled to a power converter that includes (1) a converter circuit configured to convert an input voltage V.sub.IN to a stepped-up voltage V.sub.OUT and (2) an auxiliary circuit coupled to V.sub.OUT and configured to provide control signals to the converter circuit, including: (a) a charge pump oscillator having an output that includes a train of pulses; (b) a charge pump core, coupled to the output of the charge pump oscillator and to V.sub.IN and configured to output a stepped-up voltage V.sub.PUMP greater than V.sub.IN, wherein V.sub.PUMP is coupled to the auxiliary circuit of the power converter and is sufficient to enable operation of the auxiliary circuit while V.sub.OUT is insufficient to enable operation of the auxiliary circuitry; wherein the power converter is one of a bidirectional power converter or a unidirectional power converter capable of operation in a reverse configuration.

9. The invention of claim 8, wherein the initial startup charge pump circuit can be selectively disabled after V.sub.OUT is sufficient to enable operation of the auxiliary circuit.

10. The invention of claim 8, wherein the initial startup charge pump circuit outputs V.sub.PUMP to the auxiliary circuit in response to an enable signal while V.sub.OUT from the converter circuit to the auxiliary circuit is less than a minimum voltage V.sub.MIN.

11. The invention of claim 8, wherein the power converter includes a charge pump.

12. The invention of claim 8, further including a current in-rush protection circuit coupled in series between V.sub.IN and the power converter, and coupled to and controlled by V.sub.PUMP, the current in-rush protection circuit configured to limit current flow from V.sub.IN to the power converter for a period of time.

13. The invention of claim 8, wherein the initial startup charge pump circuit can be selectively disabled after V.sub.OUT is sufficient to enable operation of the auxiliary circuit but outputs V.sub.PUMP to the auxiliary circuit in response to an enable signal while V.sub.OUT from the converter circuit to the auxiliary circuit is less than a minimum voltage V.sub.MIN.

14. A power converter including: (a) a converter circuit configured to be coupled between a voltage source and a load, and to convert a voltage from the voltage source to an output voltage; (b) a controller, coupled to the converter circuit and configured to operate the converter circuit in either a boost or buck configuration; (c) an auxiliary circuit, coupled to the controller and to the converter circuit, the auxiliary circuit configured to provide one or more voltages and/or signals to the controller; and (d) an initial startup charge pump circuit, coupled to the voltage source and to the auxiliary circuit and configured to output a voltage V.sub.PUMP to the auxiliary circuit sufficient to enable operation of the auxiliary circuit while the output voltage from the converter circuit is insufficient to enable operation of the auxiliary circuit; wherein the power converter is one of a bidirectional power converter or a unidirectional power converter capable of operation in a reverse configuration.

15. The invention of claim 14, wherein the initial startup charge pump circuit can be selectively disabled after the output voltage from the converter circuit to the auxiliary circuit is sufficient to enable operation of the auxiliary circuit.

16. The invention of claim 14, wherein the initial startup charge pump circuit outputs V.sub.PUMP to the auxiliary circuit in response to an enable signal while the output voltage from the converter circuit to the auxiliary circuit is less than a selected minimum voltage.

17. The invention of claim 14, further including a current in-rush protection circuit coupled in series between the voltage source and the converter circuit, and coupled to and controlled by V.sub.PUMP, the current in-rush protection circuit configured to limit current flow from the voltage source to the converter circuit for a period of time.

18. The invention of claim 14, wherein the converter circuit includes a charge pump.

19. The invention of claim 14, wherein the initial startup charge pump circuit includes: (a) a charge pump oscillator having an output that includes a train of pulses; and (b) a charge pump core, coupled to the output of the charge pump oscillator and to the input voltage source, configured to output the voltage V.sub.PUMP.

20. The invention of claim 19, wherein the initial startup charge pump circuit can be selectively disabled after the output voltage from the converter circuit to the auxiliary circuit is sufficient to enable operation of the auxiliary circuit.

21. The invention of claim 19, wherein the initial startup charge pump circuit outputs V.sub.PUMP to the auxiliary circuit in response to an enable signal while the output voltage from the converter circuit to the auxiliary circuit is less than a selected minimum voltage.

22. The invention of claim 19, further including a current in-rush protection circuit coupled in series between the voltage source and the converter circuit, and coupled to and controlled by V.sub.PUMP, the current in-rush protection circuit configured to limit current flow from the voltage source to the converter circuit for a period of time.

23. The invention of claim 19, wherein the converter circuit includes a charge pump.

24. The invention of claim 14, wherein the initial startup charge pump circuit can be selectively disabled after the output voltage from the converter circuit to the auxiliary circuit is sufficient to enable operation of the auxiliary circuit but outputs V.sub.PUMP to the auxiliary circuit in response to an enable signal while the output voltage from the converter circuit to the auxiliary circuit is less than a selected minimum voltage.

Description

DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a block diagram of a prior art unidirectional power converter.

(2) FIG. 2 is a block diagram showing one example of an auxiliary circuit for the power converter of FIG. 1.

(3) FIG. 3 shows a block diagram of a non-operational configuration of the unidirectional power converter of FIG. 1 in which the voltage source and load are swapped.

(4) FIG. 4 is a block diagram of a generalized initial startup charge pump coupled to a power converter, which may be a reversed unidirectional power converter or a bi-modal power converter.

(5) FIG. 5 is a block diagram of a more detailed portion of one embodiment of the circuit shown in FIG. 4.

(6) FIG. 6 is a more detailed schematic view of one example embodiment of the block diagram circuit of FIG. 5.

(7) FIG. 7 is a process flow chart showing a first method for starting up a power converter.

(8) FIG. 8 is a process flow chart showing a second method for starting up a power converter.

(9) FIG. 9 is a process flow chart showing a third method for starting up a power converter.

(10) FIG. 10 is a process flow chart showing a fourth method for starting up a power converter.

(11) Like reference numbers and designations in the various drawings indicate like elements.

DETAILED DESCRIPTION

(12) The present invention encompasses circuits and methods for providing at least a startup voltage for reversed-operation unidirectional power converters or bi-modal power converters sufficient to power an auxiliary circuit of such power converters while the normal supply voltage to the auxiliary circuit is insufficient to enable operation of the auxiliary circuit. Embodiments of the invention utilize an initial startup charge pump circuit to create a suitable startup voltage while the normal supply voltage to the auxiliary circuit is less than a specified voltage V.sub.MIN. Embodiments of the present invention also provide additional benefits, including higher efficiency and smaller size compared to conventional solutions, since the initial startup charge pump circuit omits the use of an inductor.

(13) FIG. 4 is a block diagram 400 of a generalized initial startup charge pump 402 coupled to a power converter 404, which may be a reversed unidirectional power converter or a bi-modal power converter. The configuration of the power converter 404 is the same as the non-operational configuration shown in FIG. 3, but made operational by the addition of the initial startup charge pump (ISCP) 402. The ISCP 402 has an input coupled to V.sub.IN from the voltage source 104 (e.g., a battery, such as a 4.25 V cell) and an output V.sub.PUMP coupled to V.sub.INPUT of the auxiliary circuit 110 (as well as to the input terminal T1 of the converter circuit 102).

(14) In operation, the ISCP 402 is powered by V.sub.IN suppled from the voltage source 104. Operating as a boost charge pump, the ISCP 402 receives V.sub.IN and outputs an increased voltage V.sub.PUMP (i.e., such that V.sub.PUMP>V.sub.IN) to the auxiliary circuit 110 that is designed to equal or exceed V.sub.MIN, the minimum voltage needed to sufficiently power the particular auxiliary circuit 110. V.sub.MIN may vary in different circuit configurations, depending on the voltage requirements of the components within the auxiliary circuit 110. Accordingly, the ISCP 402 should be designed to boost V.sub.IN by a suitable multiplier.

(15) In the illustrated embodiment, the ISCP 402 also has an optional ENABLE control input that selectively enables the ISCP 402 (e.g., for startup of the power converter 404) or disables the ISCP 402 (e.g., after the power converter 404 is fully operational). A benefit of the optional ENABLE control input is higher efficiency compared to conventional solutions, since the ISCP 402 may be disabled when the output voltage V.sub.OUT from the converter circuit 102 is sufficient to power the auxiliary circuit 110. The ENABLE control input may be generated in a number of ways. For example, a clocking circuit (not shown) set for a specified period of startup time may be used to enable the ISCP 402 until the period times out, at which point the ISCP 402 is disabled and draws no power. As another example, a voltage output monitoring circuit (not shown) may be configured to enable ISCP 402 only when V.sub.OUT<V.sub.MIN, and otherwise disable the ISCP 402.

(16) As should be clear, when V.sub.IN from the voltage source 104 is coupled to terminals T1/T1′ rather than to terminals T2/T2′ (for example, as happens from time to time with a bi-modal power converter, or when a nominally unidirectional power converter is operated in normal forward mode rather than in a reversed mode), the auxiliary circuit 110 is directly powered by V.sub.IN and the ISCP 402 may be disabled.

(17) FIG. 5 is a block diagram 500 of a more detailed portion of one embodiment of the circuit shown in FIG. 4. In the illustrated example, the ISCP 402 comprises a charge pump (CP) oscillator 502 coupled to a charge pump (CP) core 504. The CP oscillator 502 provides a train of pulses, such as square wave pulses, to the CP core 504. The CP core 504 is a boost power converter designed to increase V.sub.IN to V.sub.PUMP (i.e., such that V.sub.PUMP>V.sub.IN). As one example, the CP core 504 may be a Dickson charge pump. As noted above, the optional ENABLE control input selectively enables or disables the ISCP 402, such as by starting or stopping the CP oscillator 502.

(18) Also shown in FIG. 5 is an optional current in-rush protection circuit 506 designed to limit current to the converter circuit 102 from the voltage source 104 until the converter circuit 102 becomes operational. In the illustrated example, the current in-rush protection circuit 506 is designed to be controlled by V.sub.PUMP and limit current flow from the voltage source 104 to the converter circuit 102 for a period of time at startup.

(19) FIG. 6 is a more detailed schematic view 600 of one example embodiment of the block diagram circuit of FIG. 5. In the illustrated example, the CP oscillator 502 is a relaxation oscillator that includes series-connected NAND gates N1, N2. The NAND gates N1, N2 output a periodic waveform, such as a train of square wave pulses. The NAND gates N1, N2 may comprise low-voltage FETs (particularly MOSFETs) powered by V.sub.IN and are enabled or disabled by the state of the ENABLE control input (e.g., a logic “0”=DISABLE, and a logic “1”=ENABLE). The capacitor C couples the output of the CP oscillator 502 back into NAND gates N1, N2 through respective resistors R.sub.N1, R.sub.N2; in one example circuit, the capacitor C has a value of about 1 μF, the resistor R.sub.N1 has a value of about 50 kΩ, and the resistor R.sub.N2 has a value of about 5 kΩ. The capacitor C together with resistors R.sub.N1, R.sub.N2 form a time constant that sets the frequency of oscillation of the circuit. The frequency of oscillation is determined by the inverse of (2.2×R.sub.N2×C) if R.sub.N1 is 10 times R.sub.N2. As should be clear, other circuits may be used to output a periodic waveform suitable for driving the CP core 504, including a ring oscillator.

(20) The CP core 504 shown in FIG. 6 is a simple Dickson charge pump comprising, in this example, two series-connected diodes D1, D2 and a transfer capacitor C.sub.T. The input of diode D1 is coupled to V.sub.IN while the output of diode D1 is coupled to the input of diode D2. The transfer capacitor C.sub.T is coupled between the output of the CP oscillator 502 and a node between the output of diode D1 and the input of diode D2. The output of diode D2 is V.sub.PUMP. In operation, as V.sub.IN is applied to diode D1, the periodic waveform output by the CP oscillator 502 is applied to one terminal of the transfer capacitor C.sub.T. The alternating charge across transfer capacitor C.sub.T is added to V.sub.IN to generate V.sub.PUMP, and thus V.sub.PUMP is greater than V.sub.IN.

(21) In one example embodiment, the transfer capacitor C.sub.T has a value of about 10 μF. An optional smoothing capacitor C.sub.S removes ripple content from V.sub.PUMP; in one example embodiment, the smoothing capacitor C.sub.S has a value of about 10 μF. In some embodiments, the smoothing capacitor C.sub.S is not necessary if the load 106 has a large output capacitance. The smoothing capacitor C.sub.S is also useful for local bypassing relative to the current in-rush protection circuit 506 and if both the CP core 504 and the current in-rush protection circuit 506 (if present) are located far away from the load 106.

(22) For the circuit shown in FIG. 6, if V.sub.IN is about 4.25V, such as from some types of lithium-ion batteries, the CP core 504 can generate an output V.sub.PUMP of about 5V (after accounting for the voltage drops across diodes D1, D2), which may be sufficient to power a low-voltage auxiliary circuit 110. More generally, the component values and number of charge pump stages of the CP core 504 should be sized to generate V.sub.PUMP at a voltage of at least V.sub.MIN. As should be clear, other charge pump topologies, such as series-parallel, ladder, or Fibonacci, may be used to convert V.sub.IN up to V.sub.PUMP.

(23) In the example illustrated in FIG. 6, the current in-rush protection circuit 506 includes a transistor M in series between the voltage source 104 and the converter circuit 102. The gate of the transistor M is controlled by an RC circuit including a resistor R1 coupled between V.sub.PUMP and the gate, with a shunt capacitor C1 coupled between the gate and circuit ground; the time constant of the RC circuit controls the conductivity of the transistor M, slowly biasing the transistor M from an OFF (non-conductive) state to an ON (conductive) state as V.sub.PUMP ramps up. Accordingly, the current in-rush protection circuit 506 limits current flow from the voltage source 104 to the converter circuit 102 for a period of time. In one example circuit, resistor R1 has a value of about 1 kΩ and capacitor C1 has a value of about 10 μF.

(24) As should be apparent from FIGS. 4-6, the ISCP 402 is effectively an auxiliary charge pump coupled in parallel with the converter circuit 102, but needed only under certain circumstances. For example, as noted above, the ISCP 402 enables utilization of an existing unidirectional power converter in a reversed configuration, such that the connections of V.sub.IN and V.sub.OUT to the terminals T1/T1′, T2/T2′ of the converter circuit 102 are switched, as shown in FIGS. 4-6. In such an application, it may only be necessary to enable the ISCP 402 at circuit startup until V.sub.OUT from the converter circuit 102 is sufficient to operate the auxiliary circuit 110 (i.e., is equal to or greater than V.sub.MIN). Thereafter, the ISCP 402 may be disabled using the ENABLE control input. However, if V.sub.OUT should fall to less than V.sub.MIN, the ISCP 402 may be re-enabled by the ENABLE control input so as to generate V.sub.PUMP to supply power to the auxiliary circuit 110. For example, a voltage output monitoring circuit (not shown) coupled to V.sub.OUT in FIG. 4 may detect occasions when V.sub.OUT<V.sub.MIN, and provide an input to control circuitry that sets an “enabled” state for the ENABLE control input to the ISCP 402.

(25) As another example, the ISCP 402 may also be used with a bi-modal power converter, in which the voltage source 104 may be coupled to terminals T1/T1′ in a first mode of operation, while the voltage source 104 may be coupled to terminals T2/T2′ in a second mode of operation. In such an application, it may be necessary to enable the ISCP 402 during each switch to the second mode of operation until the voltage supplied to V.sub.INPUT is sufficient to operate the auxiliary circuit 110 (i.e., is equal to or greater than V.sub.MIN). Accordingly, in such applications, the ISCP 402 may be occasionally enabled or disabled using the ENABLE control input. Thus, if V.sub.OUT should fall to less than V.sub.MIN, the ISCP 402 may be enabled by the ENABLE control input so as to generate V.sub.PUMP to supply power to the auxiliary circuit 110. For example, a voltage output monitoring circuit (not shown) coupled to V.sub.OUT in FIG. 4 may detect occasions when V.sub.OUT<V.sub.MIN and provide an input to control circuitry that generates an “enabled” state for the ENABLE control input. As another example, the ENABLE control input may be set to the “enabled” state by control circuitry (not shown) that actively switches the mode of operation for a bi-modal power converter.

(26) As noted above, most or all components of a power converter, such as the converter circuit 102, the controller 108, and the auxiliary circuit 110, may be integrated within a single integrated circuit or circuit module (noting that some relatively large components, such as capacitors, may be external). An ISCP 402 may also be integrated within the same single integrated circuit or circuit module, or may be fabricated as part of a separate integrated circuit or circuit module configured to be coupled to the other components of a power converter.

(27) Methods

(28) Another aspect of the invention includes methods for starting up a power converter, and more particularly methods for providing at least a startup voltage for reversed unidirectional power converters or bi-modal power converters sufficient to power the auxiliary circuit of such power converters while the normal supply voltage to the auxiliary circuit is insufficient. For example, FIG. 7 is a process flow chart 700 showing a first method for starting up a power converter. The method includes: coupling an initial startup charge pump circuit in parallel with a converter circuit of a power converter having an auxiliary circuit and configured to be coupled to an input voltage V.sub.IN (Block 702); and configuring the initial startup charge pump circuit to output a stepped-up voltage V.sub.PUMP greater than V.sub.IN, wherein V.sub.PUMP is coupled to the auxiliary circuit and is sufficient to power the auxiliary circuit (Block 704).

(29) As another example, FIG. 8 is a process flow chart 800 showing a second method for starting up a power converter. The method includes: providing the initial startup charge pump circuit with a charge pump oscillator having an output that includes a train of pulses and a charge pump core coupled to the output of the charge pump oscillator and to an input voltage V.sub.IN coupled to a power converter circuit (Block 802); and configuring the charge pump core to output a stepped-up voltage V.sub.PUMP greater than V.sub.IN, wherein V.sub.PUMP is coupled to an auxiliary circuit of the power converter and is sufficient to power the auxiliary circuit (Block 804).

(30) As yet another example, FIG. 9 is a process flow chart 900 showing a third method for starting up a power converter. The method includes: configuring a power converter circuit to include (1) a converter circuit configured to be coupled to an input voltage V.sub.IN and output a voltage V.sub.OUT to a load; (2) a controller, coupled to the converter circuit and configured to control the converter circuit to cause the converter circuit to either boost or buck V.sub.IN to V.sub.OUT; and (3) an auxiliary circuit, coupled to the controller and configured to provide various voltages and/or signals to the controller (Block 902); coupling an initial startup charge pump circuit to V.sub.IN and to the auxiliary circuit (Block 904); and configuring the initial startup charge pump circuit to output a stepped-up voltage V.sub.PUMP greater than V.sub.IN, wherein V.sub.PUMP is coupled to the auxiliary circuit and is sufficient to power the auxiliary circuit (Block 906).

(31) As still another example, FIG. 10 is a process flow chart 1000 showing a fourth method for starting up a power converter. The method includes: configuring a power converter circuit to include (1) a converter configured to be coupled to an input voltage V.sub.IN and output a voltage V.sub.OUT to a load; (2) a controller, coupled to the converter circuit and configured to control the converter circuit to cause the converter circuit to either boost or buck V.sub.IN to V.sub.OUT; and (3) an auxiliary circuit, coupled to the controller and configured to provide various voltages and/or signals to the controller (Block 1002); and coupling an initial startup charge pump circuit to V.sub.IN and to the auxiliary circuit, the initial startup charge pump circuit including (1) a charge pump oscillator having an output that includes a train of pulses; and (2) a charge pump core, coupled to the output of the charge pump oscillator and to V.sub.IN, configured to output a stepped-up voltage V.sub.PUMP greater than V.sub.IN, wherein V.sub.PUMP is coupled to the auxiliary circuit and is sufficient to power the auxiliary circuit (Block 1004).

(32) Additional aspects of the above methods may include one or more of the following: disabling the initial startup charge pump circuit after a normal supply voltage from the power converter or the converter circuit to the auxiliary circuit is sufficient to enable operation of the auxiliary circuit; enabling the initial startup charge pump circuit while a normal supply voltage from the converter circuit of the power converter or the converter circuit to the auxiliary circuit is insufficient to enable operation of the auxiliary circuit; configuring the initial startup charge pump circuit to be coupled to and provide V.sub.PUMP to one of a reversed unidirectional power converter or a bi-modal power converter; coupling a current in-rush protection circuit in series between the input source and the power converter or the converter circuit, powering the current in-rush protection circuit by V.sub.PUMP, and configuring the current in-rush protection circuit to limit current flow from the input source to the power converter or the converter circuit for a period of time.

(33) Fabrication Technologies & Options

(34) The term “MOSFET”, as used in this disclosure, includes any field effect transistor (FET) having an insulated gate whose voltage determines the conductivity of the transistor, and encompasses insulated gates having a metal or metal-like, insulator, and/or semiconductor structure. The terms “metal” or “metal-like” include at least one electrically conductive material (such as aluminum, copper, or other metal, or highly doped polysilicon, graphene, or other electrical conductor), “insulator” includes at least one insulating material (such as silicon oxide or other dielectric material), and “semiconductor” includes at least one semiconductor material.

(35) Various embodiments of the invention can be implemented to meet a wide variety of specifications. Unless otherwise noted above, selection of suitable component values is a matter of design choice. Various embodiments of the invention may be implemented in any suitable integrated circuit (IC) technology (including but not limited to MOSFET structures), or in hybrid or discrete circuit forms. Integrated circuit embodiments may be fabricated using any suitable substrates and processes, including but not limited to standard bulk silicon, silicon-on-insulator (SOI), and silicon-on-sapphire (SOS). Unless otherwise noted above, embodiments of the invention may be implemented in other transistor technologies such as bipolar, LDMOS, BCD, and MESFET technologies. However, embodiments of the invention are particularly useful when fabricated using an SOI or SOS based process, or when fabricated with processes having similar characteristics. Fabrication in CMOS using SOI or SOS processes enables circuits with low power consumption, the ability to withstand high power signals during operation due to FET stacking, good linearity, and high frequency operation (i.e., radio frequencies up to and exceeding 50 GHz). Monolithic IC implementation is particularly useful since parasitic capacitances generally can be kept low (or at a minimum, kept uniform across all units, permitting them to be compensated) by careful design.

(36) Voltage levels may be adjusted, and/or voltage and/or logic signal polarities reversed, depending on a particular specification and/or implementing technology (e.g., NMOS, PMOS, or CMOS, and enhancement mode or depletion mode transistor devices). Component voltage, current, and power handling capabilities may be adapted as needed, for example, by adjusting device sizes, serially “stacking” components (particularly FETs) to withstand greater voltages, and/or using multiple components in parallel to handle greater currents. Additional circuit components may be added to enhance the capabilities of the disclosed circuits and/or to provide additional functionality without significantly altering the functionality of the disclosed circuits.

(37) Circuits and devices in accordance with the present invention may be used alone or in combination with other components, circuits, and devices. Embodiments of the present invention may be fabricated as integrated circuits (ICs), which may be encased in IC packages and/or or modules for ease of handling, manufacture, and/or improved performance. In particular, IC embodiments of this invention are often used in modules in which one or more of such ICs are combined with other circuit blocks (e.g., filters, passive components, and possibly additional ICs) into one package. The ICs and/or modules are then typically combined with other components, often on a printed circuit board, to form an end product such as a cellular telephone, laptop computer, or electronic tablet, or to form a higher level module which may be used in a wide variety of products, such as vehicles, test equipment, medical devices, etc. Through various configurations of modules and assemblies, such ICs typically enable a mode of communication, often wireless communication.

(38) Conclusion

(39) A number of embodiments of the invention have been described. It is to be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, some of the steps described above may be order independent, and thus can be performed in an order different from that described. Further, some of the steps described above may be optional. Various activities described with respect to the methods identified above can be executed in repetitive, serial, or parallel fashion.

(40) It is to be understood that the foregoing description is intended to illustrate and not to limit the scope of the invention, which is defined by the scope of the following claims, and that other embodiments are within the scope of the claims. In particular, the scope of the invention includes any and all feasible combinations of one or more of the processes, machines, manufactures, or compositions of matter set forth in the claims below. (Note that the parenthetical labels for claim elements are for ease of referring to such elements, and do not in themselves indicate a particular required ordering or enumeration of elements; further, such labels may be reused in dependent claims as references to additional elements without being regarded as starting a conflicting labeling sequence).