Power supply

Abstract

There is disclosed, by way of example, a reversible power supply includes a polarity correction circuit. The reversible power supply may receive, for example, a battery, which may be inserted with either polarity. An illustrative polarity correction circuit includes a first stage transistor network to bootstrap the circuit, and an amplified second stage to operate the circuit in its steady state. There is also shown a single stage amplified polarity correction circuit. As an illustrative use case, the reversible power supply may supply a high-voltage power supply for an image intensifier.

Description

POWER SUPPLYCross-Reference to Related Application

[0001] This International Application claims the benefit of and priority from U.S. Provisional Patent Application Serial No. 63 / 624,075 titled “REVERSIBLE POWER SUPPLY” filed on January 23, 2024, and is hereby incorporated by reference in its entirety.Field of the Specification

[0002] This International application relates to power engineering, and more particularly to a high-efficiency reversible power supply.Background

[0003] Many microelectronics, including portable microelectronics, use a battery power source. In many cases, these devices are sensitive to battery polarity, meaning that the battery must be inserted correctly for the device to function. If the polarity of the battery is reversed, the device will not power on, or may even suffer an electrical short.Brief Description of the Drawings

[0004] The present disclosure is best understood from the following detailed description when read with the accompanying FIGURES. It is emphasized that, in accordance with the standard practice in the industry, various features are not necessarily drawn to scale, and are used for illustration purposes only. Where a scale is shown, explicitly or implicitly, it provides only one illustrative example. In other embodiments, the dimensions of the various features maybe arbitrarily increased or reduced for clarity of discussion. Furthermore, the various block diagrams illustrated herein disclose only one illustrative arrangement of logical elements. Those elements may be rearranged in different configurations, and elements shown in one block may, in appropriate circumstances, be moved to a different block or configuration.

[0005] FIGURE 1 is a perspective view of selected elements of a night vision device according to one or more examples of the present specification.

[0006] FIGURE 2 is a cutaway perspective view of selected elements of an image intensifier tube according to one or more examples of the present specification.

[0007] FIGURE 3 is a block diagram of selected elements of an assembled image intensifier according to one or more examples of the present specification.

[0008] FIGURE 4 is a block diagram of selected elements of an image intensifier power supply circuit, with accompanying power delivery examples, according to one or more examples of the present specification.

[0009] FIGURE 5 is a block diagram of a polarity correction circuit for providing a reversible power supply.

[0010] FIGURE 6 is a pseudo-circuit illustration of operation of the circuit of FIGURE 5, with a first polarity.

[0011] FIGURE 7 is a pseudo-circuit illustration of operation of the circuit of FIGURE 5, with a second polarity.

[0012] FIGURE 8 is a block diagram of an illustrative single-stage reversible power supply.Summary

[0013] There is disclosed, by way of example, a reversible power supply includes a polarity correction circuit. The reversible power supply may receive, for example, a battery, which may be inserted with either polarity. An illustrative polarity correction circuit includes a first stage transistor network to bootstrap the circuit, and an amplified second stage to operate the circuit in its steady state. There is also shown a single stage amplified polarity correction circuit. As an illustrative use case, the reversible power supply may supply a high-voltage power supply for an image intensifier.Embodiments of the Disclosure

[0014] The following disclosure provides many different embodiments, or examples, for implementing different features of the present disclosure. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. Further, the present disclosure may repeat reference numerals and / or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does notin itself dictate a relationship between the various embodiments and / or configurations discussed. Different embodiments may have different advantages, and no particular advantage is necessarily required of any embodiment.Overview[o 015] This specification describes a reversible power supply circuit with a polarity correction circuit. As used in this specification, a reversible power supply includes a power supply that is insensitive to the polarity of the incoming power source (e.g., a power supply in which the battery can be inserted in either direction, or one in which either source node can have either positive or negative polarity). The reversible power supply is illustrated in the context of a night vision system that includes a high-voltage image intensifier, to illustrate a use case of the polarity correction circuit. However, the teachings of the present specification are generally applicable to any circuit that may benefit from a reversible power supply.

[0016] A night vision system is a useful illustration because portable night vision system commonly operate from a batter source, such as a single AA battery, with a nominal output voltage of approximately 1.5V. By design, night vision system are commonly operated in dark conditions. The conditions may also be stressful. For example, night vision is popular in military applications. Thus, a reasonable use case is a situation in which a soldier in a firefight needs to change out a battery on a night vision system in the dark. In such a situation, it is beneficial for the operator, under stress and in the dark, to not have to be concerned about the correct polarity of the battery.

[0017] Some polarity correction circuits are known, including some single-stage polarity correction circuits that include a transistor network to correctly sense voltage polarity, and route power to the correct source terminals for the load. However, at least some of these circuits suffer from inefficiency. For example, some known polarity correctors include a transistor network similar to first stage 530 of FIGURE 5. However, at least some embodiments of first stage 530 suffer from internal impedance because the supply voltage only weakly turns on the transistors. This internal impedance results in a lower voltage at step-up converter 532. Conservation of energy requires that, to achieve the desired output voltage at the output of step-up converter 532 with a low input voltage, a correspondingly high input current is required. Such increased input current drains thebattery more quickly, thus reducing battery life, which can be an important factor in military and other applications. Furthermore, the configuration may also result in an undesirable positive feedback loop. The more power is drained from the battery, the more weakly the transistor network switches on, the lower the input voltage to step-up converter 532, and the more current is drawn.

[0018] The polarity correction circuit of the present specification addresses this inefficiency by providing an amplified second stage. In the configuration illustrated in FIGURE 5, second stage 540 is amplified to the “rails” of the battery input. Thus, first stage 530 acts to bootstrap second stage 540, and second stage 540 drives the steady-state circuit. Because the two stages operate in parallel, once second stage 540 is operational, first stage 530 (with higher impedance) is effectively bypassed.

[0019] There is also illustrated in FIGURE 8 a polarity correction circuit with a single amplified stage.

[0020] To illustrate a use case, FIGURES 1 - 4 provide an night vision system and an associated high-voltage power supply. The polarity correction circuit of FIGURE 5 provides a 2.2V output, to power certain elements of the night vision system, and a doubled 4.4V output that can be provided to the control circuit (which may itself amplify the voltage to the range of plus or minus hundreds of volts).Selected Examples

[0021] The foregoing can be used to build or embody several example implementations, according to the teachings of the present specification. Some example implementations are included here as nonlimiting illustrations of these teachings.

[0022] One example includes polarity correction circuit, comprising: a supply input having a first input terminal and a second input terminal, the supply input comprising circuitry to provide a floating voltage with a magnitude and an unknown polarity; a first stage transistor network, comprising transistors configured to receive the supply input and output a voltage Vinwith a fixed polarity; an amplifier circuit to amplify Vln, the amplifier circuit to provide an amplified input voltage Vamp; a second stage transistor network; and a comparator network in a feedback configuration with the first stage transistor network, the comparator network configured to provide Vampto gates oftransistors of the second stage transistor network, wherein the second stage transistor network comprises circuitry to pull up Vinto substantially the same magnitude as the supply input.

[0023] Another example includes the correction circuit, wherein Vamphas a magnitude greater than a nominal turn-on voltage for transistors within the first stage transistor network or second-stage transistor network.

[0024] Another example includes the polarity correction circuit, wherein the supply input has a voltage is less than a nominal turn-on voltage for transistors within the first stage transistor network, whereby the transistors of the first stage transistor network have an internal impedance, whereby Vin, as supplied only by the first stage transistor network, has a magnitude less than the magnitude of the supply input.

[0025] Another example includes the polarity correction circuit, wherein the supply input is a direct current battery supply input.

[0026] Another example includes the polarity correction circuit, wherein the battery supply input has a magnitude of substantially 0.9 volts to 1.5 volts.

[0027] Another example includes the polarity correction, wherein the battery supply input is a single battery.

[0028] Another example includes the polarity correction circuit, wherein the first stage transistor network comprises two p-channel field-effect transistors (FETs) and two n-channel FETs.

[0029] Another example includes the polarity correction circuit, wherein the second input terminal is electrically coupled to gate nodes of the p-channel FETs and to drain nodes of the n-channel FETs, and the second input terminal is electrically coupled to gates nodes of the n-channel FETs and source nodes of the p-channel FETs.

[0030] Another example includes the polarity correction circuit, wherein the comparator network comprises a first operational amplifier and second operational amplifier (op amp), wherein a noninverting input of the first op amp is electrically connected to an inverting input of the second op amp and to the first input terminal, an inverting input of the first op amp is electrically connected to a noninverting input of the second op amp and the second input terminal, positive supply inputs of both op amps areelectrically connected to Vamp, and negative supply inputs of both op amps are electrically connected to a negative or system ground terminal.

[0031] Another example includes the polarity correction circuit, wherein the second stage transistor network substantially mirrors the first stage transistor network.

[0032] Another example includes the polarity correction circuit, wherein Vampis approximately 4.4. volts.

[0033] Another example includes the polarity correction circuit, wherein the amplifier circuit comprises a step-up converter with a 2.2V output.

[0034] Another example includes the polarity correction circuit, wherein the amplifier circuit further comprises a voltage doubler with a 4.4V output.

[0035] Another example includes an integrated circuit comprising the polarity correction circuit.

[0036] Another example includes an image intensifier comprising the polarity correction circuit.

[0037] Another example includes a night vision system comprising the image intensifier.

[0038] Another example includes a camera comprising the polarity correction circuit.

[0039] Another example includes a camera comprising the polarity correction circuit.

[0040] Another example includes a flashlight comprising the polarity correction circuit.

[0041] Another example includes a portable medical apparatus comprising the polarity correction circuit.

[0042] Another example includes a mobile telephone comprising the polarity correction circuit.

[0043] Another example includes a portable computer comprising the polarity correction circuit.

[0044] Another example includes a portable radio comprising the polarity correction circuit.

[0045] Another example includes a mobile weather station comprising the polarity correction circuit.

[0046] Another example includes a toy comprising the polarity correction circuit.

[0047] Another example includes a portable electronic device comprising the polarity correction circuit.

[0048] Another example includes a night vision system, comprising: an image intensification circuit, including a high-voltage power supply to receive a source voltage and step the source voltage up to one or more high voltages; a battery supply having a supply voltage, wherein the high-voltage power supply receives an input voltage from the supply voltage; a control circuit; a voltage amplifier to receive an input voltage and provide an amplified voltage to the control circuit; and polarity correction means to receive the supply voltage and provide the input voltage with a known polarity and a magnitude of the absolute value of the supply voltage, regardless of a polarity of the supply voltage.

[0049] Another example includes the night vision system, wherein the polarity correction means comprise a two-stage polarity correction circuit.

[0050] Another example includes the night vision system, wherein the polarity correction means comprise a one-stage amplified polarity correction circuit.

[0051] Another example includes the night vision system, wherein the amplifier circuit comprises a two-stage amplifier, comprising a step-up converter to 2.2V and a voltage doubler with a 4.4V output.

[0052] Another example includes a single-stage polarity correction circuit, comprising: a power source Vbatt, wherein Vbattprovides a voltage with a magnitude and a first floating terminal and second floating terminal; a field effect transistor (FET) network, comprising FETs having respective gate, drain, and source nodes, comprising a first p-channel FET (p-FET), a first n-channel FET (n-FET), a second p-FET, and a second n-FET, arranged to receive Vbattand an amplified voltage Vamp, and to provide a voltage Vinhaving a known polarity with respect to a system ground and a magnitude substantially equal to the magnitude of Vbatt; a first diode parallel to the second p-FET and a second diode parallel to the first n-FET; and an amplifier network to receive Vinand provide Vamp; and a comparator network to receive Vampand to a first amplified terminaland a second amplified terminal, wherein the first amplified terminal has a same polarity as the first floating terminal, and the second amplified terminal has a same polarity as the second floating terminal.

[0053] Another example includes the single-stage polarity correction circuit, wherein the first diode and second diode are Schottky diodes.

[0054] Another example includes the single-stage polarity correction circuit, wherein: the gate of the first p-FET is tied to the first amplified terminal, the source of the first p-FET is tied to source of the first n-FET, and the drain of the first p-FET is tied to Vin; the gate of first n-FET is tied to first amplified terminal, and the drain of the first n- FET is tied to the system ground; the gate of the second p-FET is tied to the second amplified terminal, the drain of the second p-FET is tied to the drain of the second n-FET, and the source of the first p-FET is tied to Vin; the gate of the second n-FET is tied to the second amplified terminal, and the source of the second n-FET is tied to the system ground.

[0055] Another example includes the single-stage polarity correction circuit, wherein the comparator network comprises a first operational amplifier and second operational amplifier (op amp), wherein a noninverting input of the first op amp is electrically connected to an inverting input of the second op amp and to a positive node of Vin, an inverting input of the first op amp is electrically connected to a noninverting input of the second op amp and a negative node of Vin, positive supply inputs of both op amps are electrically connected to a positive node of Vamp, and negative supply inputs of both op amps are electrically connected to a negative or system ground terminal

[0056] Another example includes the single-stage polarity correction circuit, wherein the power source comprises a battery.

[0057] Another example includes the single-stage polarity correction circuit, wherein the battery is a single battery.

[0058] Another example includes the single-stage polarity correction circuit, wherein the battery is a single AA battery.

[0059] Another example includes the single-stage polarity correction circuit, wherein the magnitude of Vbattis between substantially 0.9V and 1.5V.Detailed Description of the Drawings

[0060] A system and method for providing an night vision system with a photodiode switched power supply will now be described with more particular reference to the attached FIGURES. It should be noted that throughout the FIGURES, certain reference numerals may be repeated to indicate that a particular device or block is referenced multiple times across several FIGURES. In other cases, similar elements may be given new numbers in different FIGURES. Neither of these practices is intended to require a particular relationship between the various embodiments disclosed. In certain examples, a genus or class of elements maybe referred to by a reference numeral (“widget 10”), while individual species or examples of the element may be referred to by a hyphenated numeral (“first specific widget 10-1” and “second specific widget 10-2”).

[0061] FIGURE 1 is a perspective view of a standalone night vision system 100 according to one or more examples of the present specification. Night vision system 100 may be configured for independent use, such as in a night vision monocular, or it may be mounted on a rifle for use as a nighttime-capable scope, night vision goggle, or night vision binoculars. Night vision system 100 includes a lens 110 allowing ambient light to enter, an eyepiece 120 where a user may see the enhanced image, and focus housing 104 for adjusting the focus of the image.

[0062] FIGURE 2 is a cutaway perspective view of an image intensifier tube (IIT) 200 for use in a night vision system 100 according to one or more examples of the present specification. IIT 200 comprises a photocathode 220, a microchannel plate (MCP) 230, and phosphor screen 260. Photocathode 220 is a very thin light-sensitive film that is bonded or deposited to the back side of a glass input face plate 210. When a photon image is applied through the input face plate 210 onto photocathode 220, photocathode 220 emits photoelectrons into the vacuum space between photocathode 220 and MCP 230. The pattern of photoelectrons emitted by photocathode 220 is a replica of the photon image. The photoelectrons are accelerated from photocathode 220 by a negative voltage applied to photocathode 220 with respect to the input face of MCP 230.

[0063] MCP 230 is a thin glass wafer with many microscopic channels running through it. A large negative voltage is applied to the input face of MCP 230 with respect to the output face of MCP 230. Each channel functions as a dynode multiplier with electronic gain dependent on the magnitude of the voltage applied across MCP 230.Photoelectrons enter and strike the walls of the channels and through the process of secondary electron emission, the incident electron flux is amplified by up to thousands of times.

[0064] Because the spatial relationship of the photoelectrons entering the channels of MCP 230 is preserved throughout the gain process, the resulting electron beam exiting MCP 230 is an intensified replica of the original image incident on photocathode 220. This electronic image is then accelerated toward phosphor screen 260 by a high voltage applied between the exit face of MCP 230 and phosphor screen 260, where the electron energy is converted into light. Phosphor screen 260 is deposited onto the input side of a fiber optic bundle 240, which directs the intensified image to its output surface for viewing by the user.

[0065] FIGURE 3 is a perspective view of an image intensifier assembly (IIA) 300 according to one or more examples of the present specification. IIA 300 comprises image intensifier tube 200 and high voltage power supply 250, encapsulated into plastic housing 330 using a suitable high dielectric material 312 such as RTV. Dielectric material 312 is placed to completely fill the space between plastic housing 330 and the outer edge 314 of IIT 200. An aperture 332 is provided to expose face plate 210. The encapsulating material provides electrical isolation to prevent dielectric breakdown and mechanical support for maintaining proper positioning within the plastic housing.

[0066] Photocathode 220, MCP 230, and screen 260 (as seen in FIGURE 2) may be provided as a pre-manufactured IIT 200. These elements are seated in close proximity to each other using a series of concentric ceramic and metal rings for electrical and hermetic isolation. A high voltage power supply 250 provides the necessary voltages to IIA 300. In some embodiments, high-voltage power supply 250 is provided as a circuit board that wraps around IIT 200. In other embodiments, power supply 250 may be provided as a more standard circuit board, such as a flat circuit board, which may have small dimensions such as a square of less than 1 inch on each side.

[0067] FIGURE 4 a is a block diagram of selected elements of a power supply system 400. The circuit illustrated in FIGURE 4 may provide a switched power supply, such as to increase efficiency. Some of the elements shown may be embodied in a single, discrete circuit board.[oo68] Power supply system 400 interfaces with a photocathode 414, which receives incident light at a high negative voltage, and converts the incident photons to an electron stream. Photocathode 414 is coupled via a vacuum with MCP 412. MCP 412 includes a bundle of very small fiberoptic cables, called microchannels. A large negative voltage between input face 411 and output face 413 of MCP 412 accelerates the electrons, and further causes collisions that intensify the electron stream (e.g., each individual electron entering MCP 412 is amplified into a stream of many electrons at the output face). The multiplication of input electrons results in an intensified image at output side 413.

[0069] The stream of electrons then hits phosphorous screen 408, with the output stream from each microchannel forming a single pixel of the image. On screen 408, the incident electrons are converted back to a visual image.

[0070] In an illustrative use case, a CMOS detector is affixed directly to screen 408, and digitizes the incident image. A digital camera 402 processes the image and displays it to a user. Digital camera 402 may also provide a pulse width modulation (PWM) output signal, which can be used for switching.[o 071] An automatic brightness control (ABC) circuit 425 may keep the gain within a certain range, depending on ambient conditions. For example, as night transitions into day, more light is incident on photocathode 414, so that less gain is required to provide the same brightness of image. Similarly, if a user is in a room in which the lights are suddenly switched on, the flood of brightness maybe uncomfortable for the user, but ABC 425 can reduce the gain so that the image brightness remains relatively constant.

[0072] Digital camera 402 may also provide a user-selected brightness signal, which corresponds to the user’s desired brightness level. As described above, ABC 425 may provide feedback to help keep the actual brightness in line with the user’s selected brightness.

[0073] At a given incident light level, the circuit can adjust the observed brightness as a function of two factors: average duty cycle of the gated high-voltage input to photocathode 414, and DC voltage supplied to MCP 412.

[0074] In the case of photocathode 414, a voltage Fl is applied. If a DC voltage is supplied, then brightness varies directly with voltage. But it may be desirable to supply the maximum available voltage, as this provides greater clarity or “crispness” (i.e.,resolution) to the image. To vary brightness, voltage VI may be switched between an “active” or “on” voltage and a “passive” or “off’ voltage. Because common photocathodes operate on a large negative voltage, the “on” voltage maybe a high negative voltage (e.g., between —800 and —1200 Vdc), or at least greater in magnitude than —250 Vdc. The “off’ voltage maybe a zero voltage with respect to the MCP input face (i.e., 72), or a relatively small positive voltage, such as +40Vdc. Making the voltage slightly positive relative to the MCP input face provides better isolation between the photocathode and the MCP, as the positive voltage gates the electrons from continuing to flow through the MCP. To regulate the duty cycle of the input supplied to photocathode 414, a pair of switches 416-1 and 416- 2 are slaved to the PWM signal from digital camera 402. When switch 416-1 flips on, switch 416-2 flips off. Switch 416-1 is connected to a positive “off” voltage, and switch 416- 2 is connected to a negative “on” voltage, so this configuration is a passive or off configuration. On the next pulse, the PWM signal causes switch 416-1 to flip off, and switch 416-2 to flip on. This puts the circuit in the active or on configuration.

[0075] Thus, on each duty cycle, photocathode 414 is driven by the maximum available negative voltage, providing a clean image. Brightness is varied by increasing or decreasing the duty cycle. A higher duty results in greater brightness. A lower duty cycle results in less brightness, while maintaining the clarity of the image. In other embodiments, photocathode 414 can also be driven by a variable DC signal, which may result in degraded image clarity. Such degradation may be desirable in some cases, such as for export compliance.

[0076] In a commonly known configuration, high-power field-effect transistors (FETs) are used for switches 416. The power FETs may have a rating on the order of —20007, and provide very low impedance in their “on” state, on the order of ohms or milliohms of impedance. Power FETs are also relatively large and expensive. In some cases, it may be desirable to build a power supply circuit that is much smaller, such as a profile of approximately one inch by one inch, with a thickness of a quarter inch or less. It may also be desirable to use components that are less expensive than power FETs.

[0077] In this example, an optocoupler is used as the switch. Switches 416 may comprise an LED that is driven by the input signal. The LED is placed very close to photodiode, which in an illustration is an ordinary diode with a high-voltage rating (e.g.,greater than —2000V) that is initially left unpotted or unencapsulated. To ensure an optical path between the LED and the photodiode, a transparent separator (such as clear plastic, glass, or acrylic) maybe disposed between the two. The diode is inherently photo sensitive in this state, as photons incident on the semiconductor substrate will allow more current to flow through the diode. Thus, the LED and the unencapsulated diode may be potted together in an opaque potting material. This may help to ensure that the only light incident on the diode is the light from the LED. The optocoupler can then be switched by alternately turning the diode on and off. When the diode is on, current flows (active state). When the diode is off, current does not flow (passive state).

[0078] One reason photodiode-based optocouplers, such as optocouplers 416, may not be common in switched power supplies is that even in the active state, they may have a relatively high impedance. For example, in the configuration described herein, an active-state optical switch or optocoupler may have an internal reactive impedance on the order of kiloohms or megaohms. Such high impedance may be traditionally viewed as undesirable or even unacceptable for an active state switching element. But in the inactive state, the optocouplers have much greater impedance, on the order of giga-ohms or teraohms. Thus, the impedance between the two elements, which are designed to operate in opposite states, is orders of magnitude difference. Furthermore, the current into the photocathode photocathode is large enough that the impedance through the switches, even in the kiloohms to megaohms range, is relatively negligible.

[0079] It may also be desirable to control the negative voltage applied to the input side of MCP 412 to control gain. While it is possible to apply a switched signal to MCP 412, it is more common to provide a variable DC voltage, illustrated here as V2. The magnitude of V2 varies directly with brightness, and is mostly independent of the duty cycle of Vi. Although both Vi and V2 affect brightness, they are generally controlled independently of one another.

[0080] Because V2 is supplied by the same large DC voltage as the active voltage for photocathode 414, a linear element 417 is provided in series with MCP 412. MCP 412 itself has an internal impedance, RMCp,onthe order of 100 megaohms. Thus, the photodiode of linear element 417 forms a voltage divider with RMCP, thus providing a variable DC input voltage at input side 411 of MCP 412.[oo8i] Linear element 417 is controlled by voltage _V2ref from microcontroller 424, with low-pass filter 427 to filter out DC or near-DC elements. In this example, V2ref is illustrated as being derived from a signal provided by camera 402, which may be analog or digital. Any other suitable reference voltage may also be used.

[0082] An error integrator 420 provides negative feedback to self-regulate the voltage, keeping the drive current (which controls the brightness of the LED of linear element 417) within a nominal range, such as between (e.g., between o and 10 mA). Many variable impedance elements are known in the art. In this example, another optocoupler is used for similar considerations: to keep the power supply relatively small and relatively inexpensive. In this case, linear element 417 includes an LED, whose brightness depends on the magnitude of the LED current, as regulated by error integrator 420. A higher drive current makes the LED brighter, thus lowering the impedance of the photodiode of linear element 417. The lower the impedance of the photodiode, the higher the magnitude of V2 supplied to MCP 412, and the greater the gain through MCP 412.

[0083] Using optocouplers for both linear element 417 and switches 416 may result in a very small power supply circuit, on the order of 1 inch square, with a thickness of a quarter inch or less.

[0084] FIGURE 5 is a schematic illustration of a polarity correction circuit 500. When switch 501 closes, polarity correction circuit 500 receives a floating differential voltage, Vbattfrom battery 504. Because the battery can be inserted in either direction, Vbatthas an unknown polarity. The positive terminal of battery 504 maybe connected to either first terminal 502 of polarity correction circuit 500, or it may be connected to second terminal 503. Polarity correction circuit 500 is configured to provide a voltage, Vin, with the same magnitude as Vbatt, but with a known polarity that the circuit receiving Vincan operate with.

[0085] In circuit 500, a two-stage correction circuit is provided. First stage 530 bootstraps the circuit but may draw an undesirable excess current from the battery. Thus, a second stage 540, with lower impedance, provides the operational voltage after first stage 530 bootstraps the circuit.

[0086] First stage 530 receives Vbatt, which in the illustrative case of a single AA battery, has a magnitude of between approximately 0.9V and approximately 1.5V. Otherbatteries or other power sources may have different voltage magnitudes. First stage 530 provides initial polarity correction so that voltage Vinhas a known polarity with the absolute value of Vbatt. First stage 530 and second stage 540 both provide respective transistor networks, with several metal oxide semiconductor field-effect transistors (MOSFETs), including both p-channel FETs (p-FET) and n-channel FETs (n-FET). Each FET has a gate, a source, and a drain. For a p-FET, when the gate goes low with respect to the source node, the FET “turns on,” or more precisely begins conducting current between the source and the drain. When the turn-on voltage is above a threshold, then the current path between source and drain has very low impedance, and effectively works as an electrical short. When the voltage applied at the gate is less than the threshold, the FET may activate “weakly,” meaning that current may flow between the source and the drain, but the FET will have an internal impedance that varies inversely with the magnitude of the gate voltage. Thus, if a low voltage is applied to the gate, the FET will experience a relatively high impedance.

[0087] An n-FET works with opposite polarity to a p-FET. When the gate voltage goes high with respect to the source node, the n-FET activates and begins conducting current. As with a p-FET, an n-FET will experience an internal impedance that varies inversely with the gate voltage, up to the nominal turn-on voltage.

[0088] First stage 530 operates by applying Vbattto two pairs of FETs, each pair comprising a p-FET and an n-FET. These are shown here as p-FET 508-1 and n-FET 510- 1 in the first pair, and p-FET 508-2 AND n-FET 510-2 in the second pair, which mirror the first pair. The polarity of Vbattis unknown, but with the same pole tied to both 508-1 and 510-1, because they have opposite polarity, exactly one of the two will turn on when switch 501 is closed. The second pair mirrors the first pair, with the opposite pole of Vbatttied to both 508-2 and 510-2. When switch 501 is closed, exactly one of 508-2 and 510-2 will turn on. Furthermore, p-FETs 508-1, 508-2 and n-FETs 510-1, 510-2 each receive an opposite pole of Vbattfrom its companion. Thus, whatever the polarity of Vbatt, exactly one transistor in each pair will turn on. Either p-FET 508-1 and n-FET 510-2 will activate, with n-FET 510-1 and p-FET 508-2 inactive, or n-FET 510-1 and p-FET 508-2 will activate, with p-FET 508-1 and n-FET 510-2 inactive. The result is that Vinhas (nominally) the same magnitude as Vbatt, with a known polarity.

[0089] However, first stage 530 may experience inefficiency because the transistors turn on only weakly. For example, transistors 508, 510 may have a preferred gate turn-on voltage on the order of 2.2V or more, while Vbattprovides an input of at most 1.5V (the nominal voltage of common batteries such as AA, AAA, C, or D batteries). And even at the full nominal voltage of Vbat, Vinmay not provide the necessary voltages for control circuit 536, which may need operational voltages such as 2.2V and / or 4.4V. The amplified voltage (e.g., 2.2V or 4.4V, or some other amplified voltage) may be referred to as Vamp. Thus, an amplifier circuit comprising step-up converter 532 and voltage doubler 534 is also provided. Step-up converter 532 has an output voltage of 2.2V, and voltage doubler 534 has an output voltage of 4.4V, so that polarity correction circuit 500 is able to provide both 2.2V and 4.4V to the power supply. If Vinis below 1.5V, step-up converter 532 may still provide 2.2V at its output terminal, but because of conservation of energy, may need to draw more current to do so. As the battery drains and the output voltage drops, the transistor gate voltage correspondingly drops, making the transistors turn on even more weakly, thus providing an undesirable positive feedback loop, wherein the more the battery drains, the more Vbattdrops, and thus the more Vindrops, and the more current step-up converter 532 needs to drive 2.2V.

[0090] To address this inefficiency, a second stage 540 is provided, with gate voltages that are not provided directly by Vbatt, but rather by a comparator network 518, which receives 4.4V from voltage doubler 534, and provides 4.4V to transistors 508, 510 in second stage 540.

[0091] Comparator network 518 sits in a feedback configuration with first stage 530. Comparator network 518 includes two operational amplifiers, 520-1 and 520-2, which receive substantially 4.4V from voltage doubler 534. The inverting input of op amp 520-1 is tied to the noninverting input of op amp 520-2, and the noninverting input of op amp 520-1 is tied to the inverting input of op amp 520-2. Furthermore, the noninverting input of op amp 520-1 and inverting input of op amp 520-2 are tied to a first pole of Vbatt, while the inverting input of op amp 520-1 and the noninverting input of op amp 520-2 are tied to the opposite pole Vbatt. The positive supply pins of both op amps 520 are tied to 4.4V output of voltage doubler 534, while the negative supply pins are tied to system ground 516. Thus, after switch 501 is closed, comparator network 518 boosts any inputfrom battery 504 to respective rails of substantially +4.4V with respect to system ground 516.

[0092] The output of op amp 520-1 is tied to the gates of p-FET 508-4 and n-FET 510-4, while the output of op amp 520-2 is tied to the gates of p-FET 508-3 and n-FET 510-4. The result is a second stage circuit 540 that operates very similar to first stage 530, with the exception that whichever gates are turned on are driven with a strong 4.4V input signal, which a very low impedance (effectively an electrical short) through the FETs 508, 510 that are active within second stage 540.

[0093] The output of second stage 540 is also tied to Vin, so that second stage 540 pulls up Vin(with respect to system ground) to the full supplied magnitude of Vbatt, with positive polarity regardless of the orientation of the battery, so that the step-up converter does not need to draw extra current to source 2.2V.

[0094] As a result, control circuit 536 receives both 2.2V and 4.4V supply inputs with very low impedance. Control circuit 536 may provide operational voltage, for example, to switched power supply 400 of FIGURE 4 for use in a night vision system, or to any other circuit that may benefit from having a reversible polarity input. Applications that may benefit include many portable devices, such as night vision goggles, flashlights, still cameras (digital or analog), video cameras (digital or analog), portable medical apparatus, mobile phones, laptop computers, tablet computers, mobile weather stations, portable radios, toys, or others.

[0095] Turning to FIGURE 6, a pseudo-circuit illustrates a use case where the battery is inserted with the positive terminal of battery 504 connected to first terminal 602 of the battery input, and the negative terminal of battery 504 connected to second terminal 603 of the battery input. For convenience, this is referred to as a “positive” battery orientation, although Vbattshould be understood to be a floating potential difference.

[0096] In this configuration, a positive voltage is applied to the gates of p-FET 508- 2 and n-FET 508-1. A negative voltage is applied to the gates of p-FET 508-1 and n-FET 510-1. In this configuration, p-FET 508-2 and n-FET 510-1 act as open switches. These are illustrated as switch SWi and switch SW2, both of which are shown as open.

[0097] P-FET 508-1 and n-FET 510-2 are active in this configuration, and ideally would act as a short-circuit. However, because the voltage applied at the gates of these transistors is only in the range of 0.9 to 1.5V, the FETs may not turn on completely. Thus, the FETs will experience some internal impedance, which is modeled here as switch SW3 in series with resistor R3 for p-FET 508-1, and switch SW4 in series with resistor R4 for n-FET 510-2. These internal impedances will cause some voltage drop so that the full 0.9V to 1.5V is not applied at Vin. Thus, stepup converter 532 will draw extra current, and efficiency will be decreased.

[0098] To increase efficiency, second stage 540 is also provided, with the gate voltages provided by comparator network 518, which sits in a feedback configuration with first stage 530. In the case of positive polarity, the noninverting input of op amp 520-1 receives a positive voltage, while the inverting input of op amp 520-2 receives the same positive voltage. The inverting input of op amp 520-1 receives a negative voltage, while the noninverting input of op amp 520-2 receives the same negative voltage. Thus, the voltage output of op amp 520-1 is positive 4.4V, while the output of op amp 520-2 is oV or system ground 516. Applying the 4.4V output of op amp 520-1 to the gates of p-FET 508-4 and n-FET 510-3, both act as short-circuits. These are illustrated as switch SW5 and switch SW7, both of which are closed to allow current to flow.

[0099] Conversely, op amp 520-2 provides ground to p-FET 508-3 and n-FET 510- 4. This causes them to act as open switches, modeled here as switch SW6 and switch SW8, both of which are open.

[0100] Notably, the impedance of second stage 540 is substantially less than the impedance of first stage 530. Thus, the voltage from second stage 540 will supply Vin, and once first stage 530 has bootstrapped the circuit, the gates of the first-stage transistors will be starved of voltage, so that first stage 530 is effectively bypassed.

[0101] FIGURE 7 is a pseudo circuit schematic that illustrates operation of polarity correction circuit 500 in the opposite or “negative” polarity of Vbatt. In this case, the positive terminal of battery 504 is connected to second terminal 503 of polarity correction circuit 500, and the negative terminal of battery 504 is connected to first terminal 502 of polarity correction circuit 500. The theory of operation is the same, but in this case, the polarities are reversed for each transistor 508, 510. Thus, resistors Ri andR.2 model the internal impedance of 508-2 and 510-1 respectively, while switches SW3 and SW4 model transistors 508-1 and 510-2 respectively. In this example, switches SW1 and SW2 are closed, while switches SW3 and SW4 are open.

[0102] In second stage 540, switches SW6 (n-FET 510-4) and SW8 (p-FET 508-3) are closed, while switches SW5 (p-FET 508-4) and SW7 (n-FET 510-3) are open. The result is the same voltage, with the same known polarity, is applied at Vin, with the full magnitude of Vbatt.

[0103] FIGURE 8 is a schematic diagram of a single stage polarity correction circuit 800. Single stage polarity correction circuit 800 is similar to second stage 540 of polarity correction circuit 500 of FIGURE 5. In the example of FIGURE 8, first stage polarity correction circuit 530 is omitted. In this case, transistors 508-3, 508-4, 510-3, and 510-4, do not have the first stage to bootstrap their operation. Thus, in this example, Schottky diodes 812-1 and 812-2 are connected in parallel to transistors 508-4 and 510-3 respectively. In other respects, circuit 800 operates similar to polarity correction circuit 500 of FIGURE 5.

[0104] Schottky diodes 812-1 and 812-2 help here to bootstrap the single stage of polarity correction circuit 800, similar to how first stage 530 bootstraps second stage 540 of polarity correction circuit 500 (FIGURE 5). Schottky diodes are characterized by a low turn-on voltage (typically less than 450 millivolts, and in some cases as little as 150 millivolts). When switch 501 is closed, depending on the polarity, either Schottky diode 812-1 or 812-2 will be forward biased, and will bypass either transistor 508-4 or 510-3 respectively, so that the circuit begins drawing current from battery 504. This current draw is sufficient to boost Vininto an active range, activating the amplifier circuit to begin feeding back to comparator network 518. In this configuration, the circuit may experience momentary excess current draw as circuit 800 bootstraps, but once the circuit is operational, the excess current drops off, similar to bypassing first stage 530 of FIGURE 5-

[0105] In the operational mode, when transistor 508-4 is active, it provides a low- impedance current path, which starves diode 812-1 of the necessary turn-on voltage to conduct current, so that diode 812-1 acts as an open circuit. When transistor 510-3 is active, it provides a low-impedance current path, which starves diode 812-2 of thenecessary turn-on voltage to conduct current, so that once again, diode 812-2 acts as an open circuit.

[0106] The foregoing outlines features of several embodiments so that those skilled in the art may better understand various aspects of the present disclosure. The foregoing detailed description sets forth examples of apparatuses, methods, and systems relating to a system for providing a gated power supply accordance with one or more embodiments of the present disclosure. Features such as structure(s), function(s), and / or characteristic(s), for example, are described with reference to one embodiment as a matter of convenience; various embodiments maybe implemented with any suitable one or more of the described features.

[0107] As used throughout this specification, the phrase “an embodiment” is intended to refer to one or more embodiments. Furthermore, different uses of the phrase “an embodiment” may refer to different embodiments. The phrases “in another embodiment” or “in a different embodiment” refer to am embodiment different from the one previously described, or the same embodiment with additional features. For example, “in an embodiment, features maybe present. In another embodiment, additional features maybe present.” The foregoing example could first refer to an embodiment with features A, B, and C, while the second could refer to an embodiment with features A, B, C, and D, with features, A, B, and D, with features, D, E, and F, or any other variation.

[0108] In the foregoing description, various aspects of the illustrative implementations may be described using terms commonly employed by those skilled in the art to convey the substance of their work to others skilled in the art. It will be apparent to those skilled in the art that the embodiments disclosed herein may be practiced with only some of the described aspects. For purposes of explanation, specific numbers, materials, and configurations are set forth to provide a thorough understanding of the illustrative implementations. In some cases, the embodiments disclosed maybe practiced without the specific details. In other instances, well-known features are omitted or simplified so as not to obscure the illustrated embodiments.

[0109] For the purposes of the present disclosure and the appended claims, the article “a” refers to one or more of an item. The phrase “A or B” is intended to encompass the “inclusive or,” e.g., A, B, or (A and B). “A and / or B” means A, B, or (A and B). For thepurposes of the present disclosure, the phrase “A, B, and / or C” means A, B, C, (A and B), (A and C), (B and C), or (A, B, and C).

[0110] The embodiments disclosed can readily be used as the basis for designing or modifying other processes and structures to carry out the teachings of the present specification. Any equivalent constructions to those disclosed do not depart from the spirit and scope of the present disclosure. Design considerations may result in substitute arrangements, design choices, device possibilities, hardware configurations, software implementations, and equipment options.

[0111] There are also provided herein certain methods, illustrated for example in flow charts and / or signal flow diagrams. The order or operations disclosed in these methods discloses one illustrative ordering that may be used in some embodiments, but this ordering is no intended to be restrictive, unless expressly stated otherwise. In other embodiments, the operations may be carried out in other logical orders. In general, one operation should be deemed to necessarily precede another only if the first operation provides a result required for the second operation to execute. Furthermore, the sequence of operations itself should be understood to be a nonlimiting example. In appropriate embodiments, some operations may be omitted as unnecessary or undesirable. In the same or in different embodiments, other operations not shown may be included in the method to provide additional results.

[0112] In certain embodiments, some of the components illustrated herein may be omitted or consolidated. In a general sense, the arrangements depicted in the FIGURES maybe more logical in their representations, whereas a physical architecture may include various permutations, combinations, and / or hybrids of these elements.

[0113] With the numerous examples provided herein, interaction maybe described in terms of two, three, four, or more electrical components. These descriptions are provided for purposes of clarity and example only. Any of the illustrated components, modules, and elements of the FIGURES may be combined in various configurations, all of which fall within the scope of this specification.

[0114] In certain cases, it may be easier to describe one or more functionalities by disclosing only selected element. Such elements are selected to illustrate specific information to facilitate the description. The inclusion of an element in the FIGURES is not intended to imply that the element must appear in the disclosure, as claimed, and theexclusion of certain elements from the FIGURES is not intended to imply that the element is to be excluded from the disclosure as claimed. Similarly, any methods or flows illustrated herein are provided by way of illustration only. Inclusion or exclusion of operations in such methods or flows should be understood the same as inclusion or exclusion of other elements as described in this paragraph. Where operations are illustrated in a particular order, the order is a nonlimiting example only. Unless expressly specified, the order of operations may be altered to suit a particular embodiment.

[0115] Other changes, substitutions, variations, alterations, and modifications will be apparent to those skilled in the art. All such changes, substitutions, variations, alterations, and modifications fall within the scope of this specification.

[0116] To aid the United States Patent and Trademark Office (USPTO) and, any readers of any patent or publication flowing from this specification, the Applicant: (a) does not intend any of the appended claims to invoke paragraph (f) of 35 U.S.C. section 112, or its equivalent, as it exists on the date of the filing hereof unless the words “means for” or “steps for” are specifically used in the particular claims; and (b) does not intend, by any statement in the specification, to limit this disclosure in any way that is not otherwise expressly reflected in the appended claims, as originally presented or as amended.

Claims

ClaimsWhat is claimed is:

1. A polarity correction circuit, comprising: a supply input having a first input terminal and a second input terminal, the supply input comprising circuitry to provide a floating voltage with a magnitude and an unknown polarity; a first stage transistor network, comprising transistors configured to receive the supply input and output a voltage Vinwith a fixed polarity; an amplifier circuit to amplify Vin, the amplifier circuit to provide an amplified input voltage Vamp; a second stage transistor network; and a comparator network in a feedback configuration with the first stage transistor network, the comparator network configured to provide Vampto gates of transistors of the second stage transistor network, wherein the second stage transistor network comprises circuitry to pull up Vinto substantially the same magnitude as the supply input.

2. The polarity correction circuit of claim 1, wherein Vamphas a magnitude greater than a nominal turn-on voltage for transistors within the first stage transistor network or second-stage transistor network.

3. The polarity correction circuit of claim 1, wherein the supply input has a voltage is less than a nominal turn-on voltage for transistors within the first stage transistor network, whereby the transistors of the first stage transistor network have an internal impedance, whereby Vin, as supplied only by the first stage transistor network, has a magnitude less than the magnitude of the supply input.

4. The polarity correction circuit of claim 1, wherein the supply input is a direct current battery supply input.

5. The polarity correction circuit of claim 4, wherein the battery supply input has a magnitude of substantially 0.9 volts to 1.5 volts.

6. The polarity correction circuit of claim 4, wherein the battery supply input is a single battery.

7. The polarity correction circuit of claim 1, wherein the first stage transistor network comprises two p-channel field-effect transistors (FETs) and two n-channel FETs.

8. The polarity correction circuit of claim 7, wherein the second input terminal is electrically coupled to gate nodes of the p-channel FETs and to drain nodes of the n-channel FETs, and the second input terminal is electrically coupled to gates nodes of the n-channel FETs and source nodes of the p-channel FETs.

9. The polarity correction circuit of claim 1, wherein the comparator network comprises a first operational amplifier and second operational amplifier (op amp), wherein a noninverting input of the first op amp is electrically connected to an inverting input of the second op amp and to the first input terminal, an inverting input of the first op amp is electrically connected to a noninverting input of the second op amp and the second input terminal, positive supply inputs of both op amps are electrically connected to Vamp, and negative supply inputs of both op amps are electrically connected to a negative or system ground terminal.

10. The polarity correction circuit of claim 1, wherein the second stage transistor network substantially mirrors the first stage transistor network.

11. The polarity correction circuit of claim 1, wherein Vampis approximately 4.

4. volts.

12. The polarity correction circuit of claim 1, wherein the amplifier circuit comprises a step-up converter with a 2.2V output.13- The polarity correction circuit of claim 12, wherein the amplifier circuit further comprises a voltage doubler with a 4.4V output.

14. An integrated circuit comprising the polarity correction circuit of any of claims 1 - 13-15. An image intensifier comprising the polarity correction circuit of any of claims 1 - 13-16. A night vision system comprising the image intensifier of claim 15.

17. A camera comprising the polarity correction circuit of any of claims 1 - 13.

18. A camera comprising the polarity correction circuit of any of claims 1 - 13.

19. A flashlight comprising the polarity correction circuit of any of claims 1 - 13.

20. A portable medical apparatus comprising the polarity correction circuit of any of claims 1 - 13.

21. A mobile telephone comprising the polarity correction circuit of any of claims 1 - 13.

22. A portable computer comprising the polarity correction circuit of any of claims 1 - 13.

23. A portable radio comprising the polarity correction circuit of any of claims 1 - 13.

24. A mobile weather station comprising the polarity correction circuit of any of claims 1 - 13.

25. A toy comprising the polarity correction circuit of any of claims 1 - 13.

26. A portable electronic device comprising the polarity correction circuit of any of claims i - 13.

27. Anight vision system, comprising: an image intensification circuit, including a high-voltage power supply to receive a source voltage and step the source voltage up to one or more high voltages; a battery supply having a supply voltage, wherein the high-voltage power supply receives an input voltage from the supply voltage; a control circuit; a voltage amplifier to receive an input voltage and provide an amplified voltage to the control circuit; and polarity correction means to receive the supply voltage and provide the input voltage with a known polarity and a magnitude of the absolute value of the supply voltage, regardless of a polarity of the supply voltage.

28. The night vision system of claim 27, wherein the polarity correction means comprise a two-stage polarity correction circuit.

29. The night vision system of claim 27, wherein the polarity correction means comprise a one-stage amplified polarity correction circuit.

30. The night vision system of claim 27, wherein the amplifier circuit comprises a two- stage amplifier, comprising a step-up converter to 2.2V and a voltage doubler with a 4.4 V output.

31. A single-stage polarity correction circuit, comprising: a power source Vbatt, wherein Vbattprovides a voltage with a magnitude and a first floating terminal and second floating terminal; a field effect transistor (FET) network, comprising FETs having respective gate, drain, and source nodes, comprising a first p-channel FET (p-FET), a first n-channel FET (n-FET), a second p-FET, and a second n-FET, arranged to receive Vbattand an amplified voltage Vamp, and to provide a voltage Vinhaving a known polarity with respect to a system ground and a magnitude substantially equal to the magnitude of Vbatt; a first diode parallel to the second p-FET and a second diode parallel to the first n-FET; and an amplifier network to receive Vinand provide Vamp; and a comparator network to receive Vampand to a first amplified terminal and a second amplified terminal, wherein the first amplified terminal has a same polarity as the first floating terminal, and the second amplified terminal has a same polarity as the second floating terminal.

32. The single-stage polarity correction circuit of claim 31, wherein the first diode and second diode are Schottky diodes.

33. The single-stage polarity correction circuit of claim 31, wherein: the gate of the first p-FET is tied to the first amplified terminal, the source of the first p-FET is tied to source of the first n-FET, and the drain of the first p-FET is tied to Vin, the gate of first n-FET is tied to first amplified terminal, and the drain of the first n-FET is tied to the system ground; the gate of the second p-FET is tied to the second amplified terminal, the drain of the second p-FET is tied to the drain of the second n-FET, and the source of the first p- FET is tied to Vin; the gate of the second n-FET is tied to the second amplified terminal, and the source of the second n-FET is tied to the system ground.34- The single-stage polarity correction circuit of claim 31, wherein the comparator network comprises a first operational amplifier and second operational amplifier (op amp), wherein a noninverting input of the first op amp is electrically connected to an inverting input of the second op amp and to a positive node of Vin, an inverting input of the first op amp is electrically connected to a noninverting input of the second op amp and a negative node of Vin, positive supply inputs of both op amps are electrically connected to a positive node ofand negative supply inputs of both op amps are electrically connected to a negative or system ground terminal.

35. The single-stage polarity correction circuit of claim 31, wherein the power source comprises a battery.

36. The single-stage polarity correction circuit of claim 35, wherein the battery is a single battery.

37. The single-stage polarity correction circuit of claim 35, wherein the battery is a single AA battery.

38. The single-stage polarity correction circuit of claim 31, wherein the magnitude of Vbatt is between substantially 0.9V and 1.5V.

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