Patent Publication Number: US-2023163690-A1

Title: Dual polarity power supply device

Description:
BACKGROUND 
     Lower power consumption and smaller form factor designs are desirable in mixed reality (MR), augmented reality (AR), and virtual reality (VR) devices for longer battery life, portability, and comfort. Liquid Crystal on Silicon (LCoS) is one type of display technology that can be employed in such MR, AR, and VR devices to contribute to a small form factor and lower power consumption. Typically, an LCoS display is powered by a power supply that provides a dual polarity voltage—i.e., a positive bias voltage and a negative bias voltage. 
     SUMMARY 
     A power supply device includes a switching converter, an inductor, and a linear voltage regulator. The inductor is electrically connected between a first switching node and a second switching node of the switching converter. The power supply device is configured such that when the switching converter is in an ON state the inductor is charged with a charging current. The power supply device is further configured such that when the switching converter is in an OFF state, (1) the switching converter modulates an input voltage to generate a positive-bias output voltage at a positive-bias output node, (2) the charging current flows from the inductor such that a negative input voltage is generated at a linear voltage regulator input node, and (3) the linear voltage regulator regulates the negative input voltage to generate a negative-bias output voltage at a negative-bias output node. 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    shows an example head-mounted display device that may include a liquid crystal on silicon (LCoS) display that receives power from a dual polarity power supply device. 
         FIG.  2    shows a block diagram of an example display device including an LCoS display that is powered by a dual polarity power supply device. 
         FIG.  3    shows a circuit diagram of an example dual polarity power supply device. 
         FIG.  4    shows a flowchart of an example method for controlling a dual polarity power supply device. 
         FIG.  5    shows an example computing system. 
     
    
    
     DETAILED DESCRIPTION 
     Liquid Crystal on Silicon (LCoS) display technology can be employed in mixed reality (MR), augmented reality (AR), and virtual reality (VR) devices to contribute to a small form factor design and low power consumption. Typically, an LCoS display is powered by a power supply that provides a dual polarity voltage—i.e., a positive bias voltage and a negative bias voltage. In one example, such a power supply device includes two separate switching converters that charge two discrete inductors to generate a positive bias voltage and a negative bias voltage for an LCoS display. The two discrete inductors are large and bulky relative to the other electronic components in the device, such that the two discrete inductors significantly contribute to an increase in size, weight, and power consumption of an MR, AR, or VR device that employs such a power supply device. Further, the two separate switching converters also contribute to such increases in size, weight, and power consumption. 
     Accordingly, the present description is directed to a dual polarity power supply device for generating a positive bias voltage and a negative bias voltage for an LCoS display (or another type of display that is powered using positive and negative bias voltages). The power supply device includes a single switching converter, a single discrete inductor, a low dropout voltage regulator, and other passive electronic components. The power supply device has a reduced size, weight, and power consumption relative to power supplies with two separate switching converters and two discrete inductors. In some implementations, the power supply device may be small enough to be integrated as part of an LCoS display module, as opposed to a separate discrete integrated circuit (IC). This integration into LCoS can further reduce the form factor, weight, and power consumption of an MR, AR, or VR device that employs such a display configuration. 
       FIG.  1    shows an example near-eye display device  100  worn by a user  102 . The near-eye display device  100  includes an LCoS display  104  configured to present virtual imagery to provide the user  102  with a MR/AR/VR experience. The near-eye display device  100  is provided as a non-limiting example of a display device having an LCoS display powered by a dual polarity power supply device. The disclosed examples of LCoS displays and dual polarity power supply devices may be implemented in any suitable type of display device. 
       FIG.  2    shows a block diagram of an example display device  200  including an LCoS display  202 . In one example, the display device  200  is representative of the near-eye display device  100  shown in  FIG.  1   . In other examples, the display device  200  may be representative of another type of display device. The display device  200  be representative of any suitable type of display device. The LCoS display  202  is mounted on a display panel  204 . The display panel  204  may include various electronic hardware modules and other electronic components that enable operation of the LCoS display  202 . In some examples, such electronic hardware modules may include different integrated circuits (ICs) that are configured to perform display-specific operations. 
     The LCoS display  202  is configured to be powered by a dual polarity power supply device  206 . The dual polarity power supply device  206  is configured to output a positive bias voltage  208  and a negative bias voltage  210  to control operation of the LCoS display  202 . As discussed above, the dual polarity power supply device  206  has a configuration that is optimized for low power consumption and a small form factor in by employing a single switching converter and a single discrete inductor. Such gains may be realized relative to a dual converter power supply configuration that includes a first switching converter and a first discrete inductor to generate a positive bias voltage and a second switching converter and a second discrete inductor to generate a negative bias voltage. 
     In some implementations, the dual polarity power supply device  206  may have a small enough form factor to be integrated into a power management IC  212  that is mounted on-board the display panel  204  itself. Such integration may allow for an overall reduction in form factor of the display device  200  and reduced power consumption relative to an off-board configuration in which the dual polarity power supply device  206  is mounted on a separate off-board hardware panel. In other implementations, the dual polarity power supply device  206  may be mounted on a separate hardware panel that is electrically connected to the display panel  204  and the LCoS display  202 . 
       FIG.  3    shows a circuit diagram of an example dual polarity power supply device  300 . In one example, the dual polarity power supply device  300  is representative of the dual polarity power supply device  206  shown in  FIG.  2   . The dual polarity power supply device  300  is configured to drive an LCoS display (or any other suitable display or system load) with different polarity bias voltages. The dual polarity power supply device  300  comprises a voltage source  302  configured to generate an input voltage (V IN ) at a switching converter input node  304  of a switching converter  310 . The voltage source  302  may take any suitable form. For example, the voltage source  302  may be a direct current (DC) voltage source. In some examples, the voltage source may comprise an output of a digital micro-controller. In other examples, the voltage source may comprise a discrete electronic component. In yet another example, the voltage source may comprise one or more batteries. 
     A switching converter input capacitor  306  is electrically intermediate the switching converter input node  304  and a ground node  308 . The switching converter input capacitor  306  has a capacitance (C IN1 ). In one example, the capacitance (C IN1 ) is selected to minimize effects of voltage ripple at the switching converter input node  304 . The ground node  308  may be set to any suitable reference voltage. In one example, the reference voltage of the ground node is set to zero volts. 
     The switching converter  310  is electrically connected to the switching converter input node  304 , which is electrically connected to the voltage source  302 . The switching converter  310  is further electrically connected to a first switching node  311 , a second switching node  312 , a positive-bias output node  314 , and a switching converter feedback node  316 . An inductor  318  is electrically connected between the first switching node  311  and the second switching node  312 . The inductor  318  has an inductance (L 1 ). A positive bias output capacitor  320  is electrically intermediate the positive-bias output node  314  and the ground node  308 . The positive bias output capacitor  320  has a capacitance (C OUT1 ). In one example, the capacitance (C OUT1 ) is selected to minimize effects of voltage ripple at the positive-bias output node  314 . 
     The switching converter  310  is configured to modulate voltage generated by the voltage source  302  from one voltage level (i.e., V IN ) to another voltage level by periodically storing energy in the inductor  318  and then releasing the stored energy to the positive-bias output node  314  at a different voltage level than the input voltage. 
     The switching converter  310  can include any suitable type of switching converter depending on the operational specifications of the device in which the dual polarity power supply device  300  is implemented. In some implementations, the switching converter  310  may include a buck switching converter that is configured to step down a higher input voltage (V IN ) to a lower positive-bias output voltage (V POS_BIAS ). In some implementations, the switching converter  310  may include a boost switching converter that is configured to step up a lower input voltage (V IN ) to a higher positive-bias output voltage (V POS_BIAS ). In some implementations, the switching converter  310  may include a buck-boost switching converter that is configured to reverse a polarity of the input voltage (V IN ) and either step up or step down the input voltage to the positive-bias output voltage (V POS_BIAS ). 
     In some examples, the inductance (L 1 ) of the inductor  318  and the capacitance (C OUT1 ) of the positive bias output capacitor  320  may be selected based on the input voltage (V N ) and the positive-bias output voltage (V POS_BIAS ) that are designated based on the design of the device in which the dual polarity power supply device  300  is implemented. Further, these passive components can be arranged in a variety of ways to realize the buck, boost, or buck-boost types of switching converter configurations. 
     The switching converter  310  is configured to switch between an ON state and an OFF state to modulate the input voltage (V N ) and generate the positive-bias output voltage (V POS_BIAS ). The dual polarity power supply device  300  is configured such that when the switching converter  310  is in the ON state the inductor  318  is charged with a charging current (I C ) that is stored in a magnetic field of the inductor  318 . The power supply device is further configured such that when the switching converter is in the OFF state, the magnetic field of the inductor  318  collapses such that the switching converter  310  modulates the input voltage (V N ) to generate the positive-bias output voltage (V POS_BIAS ) at the positive-bias output node  314 . 
     The switching converter  310  includes a first switch (not shown) electrically connected to the first switching node  311  and a second switch (not shown) electrically connected to the second switching node  312 . In some implementations, the second switch of the switching converter  310  may include a transistor and the switching converter  310  may be synchronously rectified via the transistor. In other implementations, the switching converter  310  may employ a diode as the second switch. 
     The switching converter  310  may be configured to switch between the ON state and the OFF state via any suitable control scheme. In some implementations, the switching converter  310  may be controlled with a duty cycle that dictates a percentage of time that the switching converter  310  operates in the ON state relative to the OFF state. In other implementations, the switching converter  310  may be controlled based on a frequency of a control signal, such that an amount of time that the switching converter operates in the ON state and the OFF state is adjusted by adjusting the frequency of the control signal. In some implementations, two or more of the above example control schemes may be used in conjunction to control operation of the switching converter  310 . In yet other examples, a different control scheme may be employed. 
     The power supply device  300  further comprises a switching converter feedback resistor divider  322  electrically connected between the positive-bias output node  314  and the switching converter feedback node  316 . The resistor divider  322  includes a first resistor  324  electrically connected in series with a second resistor  326 . The first resistor  324  is electrically connected between the positive-bias output node  314  and the switching converter feedback node  316 . The first resistor  324  has a resistance (R TOP1 ). The second resistor  326  is electrically connected between the switching converter feedback node  316  and the ground node  308 . The second resistor  326  has a resistance (R BOTTOM ). The switching converter feedback resistor divider  322  produces a feedback voltage (V FB ) that is proportional to the positive-bias output voltage (V POS_BIAS ) based on the resistances (R TOP1 ) and (R BOTTOM ). The switching converter  310  is configured to modulate the positive-bias output voltage (V POS_BIAs ) based on the feedback voltage (V FB ) measured via the resistor divider  322 . For example, the switching converter  310  may increase the duty cycle based on the positive-bias output voltage (V POS_BIAS ) being less than a desired voltage level and vice versa. In this way, the switching converter  310  modulates the input voltage (V IN ) to generate the positive-bias output voltage (V POS_BIAS ) at the positive-bias output node  314 . 
     The dual polarity power supply device  300  further comprises an inverting charge pump  325  electrically intermediate the second switching node  312  of the switching converter  310  and a linear voltage regulator input node  334  of a linear voltage regulator  338 . The inverting charge pump  325  is configured to generate a negative input voltage (NV IN ) at the linear voltage regulator input node  334  of the linear voltage regulator  338 . 
     The inverting charge pump  325  includes a flying capacitor  326  that is electrically connected between the second switching node  312  and an inverting charge pump node  328 . The flying capacitor  326  has a capacitance (C F ). A first diode  330  is electrically connected between the inverting charge pump node  328  and the ground node  308 . The first diode  330  is biased toward the ground node  308 . A second diode  332  is electrically connected between the inverting charge pump node  328  and a linear voltage regulator input node  334  of a linear voltage regulator  338 . The second diode  332  is biased toward the inverting charge pump node  328 . A linear voltage regulator input capacitor  336  is electrically connected between the linear voltage regulator input node  334  and the ground node  308 . The linear voltage regulator input capacitor  336  has a capacitance (C IN2 ) In one example, the capacitance (C IN2 ) is selected to minimize effects of voltage ripple at the linear voltage regulator input node  334 . 
     The inverting charge pump  325  is configured such that when the switching converter  310  is in the ON state, the flying capacitor  326  is charged with the charging current (I C ). Further, when the switching converter  310  is in the OFF state, the charging current (I C ) flows from the flying capacitor  326  and is pulled through the second diode  332  to the linear voltage regulator input capacitor  336  to generate the negative input voltage (NV IN ) at the linear voltage regulator input node  334 . In particular, the negative input voltage (NV IN ) is generated at the linear voltage regulator input node  334 , because the absolute voltage level is less than the absolute voltage level at the first diode  330 . Accordingly, the negative input voltage (NV IN ) is generated based on a signal output from the second switching node  312  of the switching converter  310 . In other words, operation of the switching converter  310  controls generation of both the positive-bias output voltage (V POS_BIAS ) and the negative input voltage (NV IN ) at the linear voltage regulator input node  334 . Due to such an arrangement, a linear voltage regulator may be employed to regulate the negative input voltage (NV IN ) to generate the negative-bias output voltage (V NEG_BIAS ) at the negative-bias output node  340 . 
     The linear voltage regulator  338  is electrically connected to the linear voltage regulator input node  334 . Further, the linear voltage regulator  338  is electrically connected to a negative-bias output node  340 , and a linear voltage regulator feedback node  346 . The linear voltage regulator  338  is configured to use a resistive voltage drop to regulate the negative input voltage (NV IN ) generated at the linear voltage regulator input node  334  to a desired negative-bias output voltage (V NEG_BIAS ) at the negative-bias output node  340 . 
     Unlike the switching converter  310 , the linear voltage regulator  338  can only generate an output voltage that is lower than an input voltage of the linear voltage regulator. In some cases, such behavior could cause issues within a power supply device. However, in the case of the power supply device  300 , the positive-bias output voltage (V POS_BIAS ) is configured to have a greater absolute value than that of the negative-bias output voltage (V NEG_BIAS ), so such issues do not factor into operation of the power supply device  300 . Further, such behavior allows a linear voltage regulator to be used instead of a second switching converter to regulate the negative-bias output voltage. By employing a linear voltage regulator instead of a second switching converter, additional size and weight reductions may be realized for the dual polarity power supply device  300  as such a linear voltage regulator does not require an inductor or transformer. Likewise, a linear voltage regulator may have greater design simplicity relative to a switching converter. Moreover, a linear voltage regulator may operate with reduced signal noise relative to a switching converter (as no switching takes place in a linear voltage regulator). In some implementations, the linear voltage regulator  338  may include a low-dropout voltage regulator. A low-dropout voltage regulator may be configured to regulate a volage even when the supply voltage level is very close to the output voltage level. 
     A negative bias output capacitor  342  is electrically intermediate the negative-bias output node  340  and the ground node  308 . The negative bias output capacitor  342  has a capacitance (C OUT2 ). In one example, the capacitance (C OUT2 ) is selected to minimize effects of voltage ripple at the negative-bias output node  340 . 
     The power supply device  300  further comprises a linear voltage regulator feedback resistor divider  344  electrically connected between the negative-bias output node  340  and the linear voltage regulator feedback node  346 . The resistor divider  344  includes a first resistor  348  electrically connected in series with a second resistor  350 . The first resistor  348  is electrically connected between the negative-bias output node  340  and the linear voltage regulator feedback node  346 . The first resistor  348  has a resistance (R TOP2 ). A second resistor  350  is electrically connected between the linear voltage regulator feedback node  346  and the ground node  308 . The second resistor  350  has a resistance (R BOTTOM2 ). The linear voltage regulator feedback resistor divider  344  produces a feedback voltage (V FB ) that is proportional to the negative-bias output voltage (V NEG_BIAS ) based on the resistances (R TOP2 ) and (R BOTTOM2 ). The linear voltage regulator  338  is configured to regulate the negative-bias output voltage (V NEG_BIAS ) based on the feedback voltage (V FB ) measured via the resistor divider  344 . In this way, the linear voltage regulator  338  regulates the negative input voltage (NV IN ) to generate the negative-bias output voltage (V NEG_BIAS ) at the negative-bias output node  340 . 
     In some implementations, the positive-bias output node  314  may be electrically connected to a positive-bias input node of a LCoS display  202  (shown in  FIG.  2   ). Likewise, the negative-bias output node  340  may be electrically connected to a negative-bias input node of the LCoS display  202  (shown in  FIG.  2   ). In this way, the dual polarity power supply device  300  may be configured to output the positive-bias output voltage (V POS_BIAS ) and the negative-bias output voltage (V NEG_BIAS ) to the LCoS display  202  (shown in  FIG.  2   ). In some implementations, the positive-bias output voltage (V POS_BIAS ) has a greater absolute value than that of the negative-bias output voltage (V NEG_BIAS ) based on the operation requirements of the LCoS display  202  (shown in  FIG.  2   ). In one example, the positive-bias output voltage may be 6 volts and the negative-bias output voltage may be −3 volts. The positive-bias output voltage (V POS_BIAS ) and the negative-bias output voltage (V NEG_BIAS ) may be set to any suitable voltage levels. 
     The use of the single switching converter with the single inductor and the single linear voltage regulator in the dual polarity power supply device provides power efficient operation while also having a small form factor. In some implementations, such a configuration allows for the dual polarity power supply device to be incorporated into an I C , such as a power management I C  that can be incorporated into a display panel of a near-eye display device. Also, in some implementations, such a configuration allows for the linear voltage regulator to be realized without an off-chip capacitor if the load current is not significant, as is typically the case for a LCoS display. 
     Although the dual polarity power supply device is discussed herein in the context of being used to power an LCoS display, the concepts discussed herein are broadly applicable to using the dual polarity power supply device to output dual polarity voltages to any suitable system load in an any suitable electronic device. 
       FIG.  4    shows an example method  400  of operating a power supply device. For example, the method  400  may be performed to operate the dual polarity power supply device  300  shown in  FIG.  3   . 
     At  402 , the method  400  includes generating an input voltage via a voltage source electrically connected to a switching converter input node of a switching converter. For example, the switching converter may include a buck switching converter, a boost switching converter, or a buck-boost switching converter depending on the input voltage and a desired positive-bias output voltage. In some implementations, the switching converter may be synchronously rectified. 
     At  404 , the method  400  includes operating the switching converter in an ON state based on an operational duty cycle of the power supply device. The power supply device may be configured such that when the switching converter is in the ON state an inductor electrically connected between a first switching converter node and a second switching node of the switching converter is charged with a charging current. 
     At  406 , the method  400  includes operating the switching converter in an OFF state based on the operational duty cycle of the power supply device. The power supply device may be configured such that when the switching converter is in the OFF state, the switching converter modulates the input voltage to generate a positive-bias output voltage at a positive-bias output node of the power supply device. Further, in the OFF state, the charging current flows from the inductor such that a negative input voltage is generated at a linear voltage regulator input node. A linear voltage regulator regulates the negative input voltage to generate a negative-bias output voltage at a negative-bias output node of the power supply device. 
     In some implementations, the positive-bias output voltage and the negative-bias output voltage may be output to an LCoS display. In some implementations, the positive-bias output voltage and the negative-bias output voltage may be output to a different type of display that is configured to be powered using dual polarity voltages. In some implementations, the positive-bias output voltage may have a greater absolute value than that of the negative-bias output voltage. In one example, the positive-bias output voltage may be 6 volts and the negative-bias output voltage may be −3 volts. In one example, the magnitudes of the bias voltages may be set based on the requirements of the display and/or other system load requirements. 
     In some implementations, the method may be performed repeatedly (or continuously) to output the positive bias voltage and the negative bias voltage according to the operational duty cycle of the switching converter. Further, in some implementations, the operational duty cycle of the switching converter may be adjusted based on feedback from a switching converter feedback resistor divider. Further, in some implementations, the linear voltage regulator may regulate the negative-bias output voltage based on feedback from a linear voltage regulator feedback resistor divider. In some implementations, the switching converter may be controlled by a different control scheme, such as a frequency-based control scheme. 
     In some implementations, the methods and processes described herein may be tied to a computing system of one or more computing devices. In particular, such methods and processes may be implemented as computer hardware, a computer-application program or service, an application-programming interface (API), a library, and/or other computer-program product. 
       FIG.  5    schematically shows a non-limiting implementation of a computing system  500  that can enact one or more of the methods and processes described above. Computing system  500  is shown in simplified form. Computing system  500  may embody the near-eye display device  100  shown in  FIG.  1   , the display device  200  shown in  FIG.  2   , and any other suitable device that include the dual polarity power supply device described herein. Computing system  500  may take the form of one personal computers, server computers, tablet computers, home-entertainment computers, network computing devices, gaming devices, mobile computing devices, mobile communication devices (e.g., smart phone), and/or other computing devices, and wearable computing devices such as head-mounted, near-eye augmented/mixed/virtual reality devices. 
     Computing system  500  includes a logic processor  502 , volatile memory  504 , and a non-volatile storage device  506 . Computing system  500  may optionally include a display subsystem  508 , input subsystem  510 , communication subsystem  512 , and/or other components not shown in  FIG.  5   . 
     Logic processor  502  includes one or more physical devices configured to execute instructions. For example, the logic processor may be configured to execute instructions that are part of one or more applications, programs, routines, libraries, objects, components, data structures, or other logical constructs. Such instructions may be implemented to perform a task, implement a data type, transform the state of one or more components, achieve a technical effect, or otherwise arrive at a desired result. 
     The logic processor  502  may include one or more physical processors (hardware) configured to execute software instructions. Additionally or alternatively, the logic processor may include one or more hardware logic circuits or firmware devices configured to execute hardware-implemented logic or firmware instructions. Processors of the logic processor  502  may be single-core or multi-core, and the instructions executed thereon may be configured for sequential, parallel, and/or distributed processing. Individual components of the logic processor optionally may be distributed among two or more separate devices, which may be remotely located and/or configured for coordinated processing. Aspects of the logic processor may be virtualized and executed by remotely accessible, networked computing devices configured in a cloud-computing configuration. In such a case, these virtualized aspects are run on different physical logic processors of various different machines, it will be understood. 
     Non-volatile storage device  506  includes one or more physical devices configured to hold instructions executable by the logic processors to implement the methods and processes described herein. When such methods and processes are implemented, the state of non-volatile storage device  506  may be transformed—e.g., to hold different data. 
     Non-volatile storage device  506  may include physical devices that are removable and/or built-in. Non-volatile storage device  506  may include optical memory (e.g., CD, DVD, HD-DVD, Blu-Ray Disc, etc.), semiconductor memory (e.g., ROM, EPROM, EEPROM, FLASH memory, etc.), and/or magnetic memory (e.g., hard-disk drive, floppy-disk drive, tape drive, MRAM, etc.), or other mass storage device technology. Non-volatile storage device  506  may include nonvolatile, dynamic, static, read/write, read-only, sequential-access, location-addressable, file-addressable, and/or content-addressable devices. It will be appreciated that non-volatile storage device  506  is configured to hold instructions even when power is cut to the non-volatile storage device  506 . 
     Volatile memory  504  may include physical devices that include random access memory. Volatile memory  504  is typically utilized by logic processor  502  to temporarily store information during processing of software instructions. It will be appreciated that volatile memory  504  typically does not continue to store instructions when power is cut to the volatile memory  504 . 
     Aspects of logic processor  502 , volatile memory  504 , and non-volatile storage device  506  may be integrated together into one or more hardware-logic components. Such hardware-logic components may include field-programmable gate arrays (FPGAs), program- and application-specific integrated circuits (PASIC/ASICs), program- and application-specific standard products (PSSP/ASSPs), system-on-a-chip (SOC), and complex programmable logic devices (CPLDs), for example. 
     When included, display subsystem  508  may be used to present a visual representation of data held by non-volatile storage device  506 . The visual representation may take the form of a graphical user interface (GUI). As the herein described methods and processes change the data held by the non-volatile storage device, and thus transform the state of the non-volatile storage device, the state of display subsystem  508  may likewise be transformed to visually represent changes in the underlying data. Display subsystem  508  may include one or more display devices utilizing virtually any type of technology. Such display devices may be combined with logic processor  502 , volatile memory  504 , and/or non-volatile storage device  506  in a shared enclosure, or such display devices may be peripheral display devices. 
     When included, input subsystem  510  may comprise or interface with one or more user-input devices such as a keyboard, mouse, touch screen, microphone for speech and/or voice recognition, a camera (e.g., a webcam), or game controller. 
     When included, communication subsystem  512  may be configured to communicatively couple various computing devices described herein with each other, and with other devices. Communication subsystem  512  may include wired and/or wireless communication devices compatible with one or more different communication protocols. As non-limiting examples, the communication subsystem may be configured for communication via a wireless telephone network, or a wired or wireless local- or wide-area network, such as a HDMI over Wi-Fi connection. In some implementations, the communication subsystem may allow computing system  500  to send and/or receive messages to and/or from other devices via a network such as the Internet. 
     In an example, a power supply device comprises a voltage source configured to generate an input voltage, a switching converter electrically connected to a switching converter input node that is electrically connected to the voltage source, a first switching node, a second switching node, and a positive-bias output node, the switching converter being configured to switch between an ON state and an OFF state, an inductor electrically connected between the first switching node and the second switching node, and a linear voltage regulator is electrically connected to a linear voltage regulator input node, and a negative-bias output node, wherein the power supply device is configured such that when the switching converter is in the ON state, the inductor is charged with a charging current, wherein the power supply device is configured such that when the switching converter is in the OFF state, the switching converter modulates the input voltage to generate a positive-bias output voltage at the positive-bias output node, and the charging current flows from the inductor such that a negative input voltage is generated at the linear voltage regulator input node, and the linear voltage regulator regulates the negative input voltage to generate a negative-bias output voltage at the negative-bias output node. In this example and/or other examples, the power supply device may further comprise an inverting charge pump electrically connected to the second switching node and configured such that when the switching converter is in the OFF state, the charging current flows from the inductor to the inverting charge pump such that the inverting charge pump generates the negative input voltage at the linear voltage regulator input node. In this example and/or other examples, the inverting charge pump may include 1) a flying capacitor electrically connected between the second switching node and an inverting charge pump node, 2) a first diode electrically connected between the inverting charge pump node and a ground node, 3) a second diode electrically connected between the inverting charge pump node and the linear voltage regulator input node, and 4) a linear voltage regulator input capacitor electrically connected between the linear voltage regulator input node and the ground node. In this example and/or other examples, the inverting charge pump may be configured such that when the switching converter is in the ON state, the flying capacitor is charged with the charging current, and when the switching converter is in the OFF state, the charging current flows from the flying capacitor through the second diode to the linear voltage regulator input capacitor to generate the negative input voltage at the linear voltage regulator input node. In this example and/or other examples, the switching converter may be electrically connected to a switching converter feedback node, and the power supply device may further comprise a feedback resistor divider electrically connected between the positive-bias output node and the switching converter feedback node, and the switching converter may be configured to modulate the positive-bias output voltage based on a feedback voltage measured via the resistor divider. In this example and/or other examples, the linear voltage regulator may be electrically connected to a linear voltage regulator feedback node, the power supply device may further comprise a feedback resistor divider electrically connected between the negative-bias output node and the linear voltage regulator feedback node, and the linear voltage regulator may be configured to regulate the negative-bias output voltage based on a feedback voltage measured via the resistor divider. In this example and/or other examples, the positive-bias output voltage may have a greater absolute value than that of the negative-bias output voltage. In this example and/or other examples, the switching converter may include a buck switching converter. In this example and/or other examples, the switching converter may include a boost switching converter. In this example and/or other examples, the switching converter may include a buck-boost switching converter. In this example and/or other examples, the linear voltage regulator may include a low-dropout voltage regulator. In this example and/or other examples, the positive-bias output node may be electrically connected to a positive-bias input node of a liquid crystal on silicon (LCoS) display, the negative-bias output node may be electrically connected to a negative-bias input node of the LCoS display, and the power supply device may be configured to output the positive-bias output voltage and the negative-bias output voltage to the LCoS display. 
     In another example, a near-eye display device comprises a liquid crystal on silicon (LCoS) display including a positive-bias input node and a negative-bias input node, and a power supply device comprising a voltage source configured to generate an input voltage, a switching converter electrically connected to a switching converter input node that is electrically connected to the voltage source, a first switching node, a second switching node, and a positive-bias output node electrically connected to the positive-bias input node of the LCoS display, the switching converter being configured to switch between an ON state and an OFF state, an inductor electrically connected between the first switching node and the second switching node, and a linear voltage regulator electrically connected to a linear voltage regulator input node and a negative-bias output node that is electrically connected to the negative-bias input node of the LCoS display, wherein the power supply device is configured such that when the switching converter is in the ON state the inductor is charged with a charging current, and wherein the power supply device is configured such that when the switching converter is in the OFF state, the switching converter modulates the input voltage to generate a positive-bias output voltage at the positive-bias output node, and the charging current flows from the inductor such that a negative input voltage is generated at the linear voltage regulator input node, and the linear voltage regulator regulates the negative input voltage to generate a negative-bias output voltage at the negative-bias output node. 
     In this example and/or other examples, the power supply device may include an inverting charge pump electrically connected to the second switching node and configured such that when the switching converter is in the OFF state, the charging current flows from the inductor to the inverting charge pump such that the inverting charge pump generates the negative input voltage at the linear voltage regulator input node. In this example and/or other examples, the inverting charge pump may include 1) a flying capacitor electrically connected between the second switching node and an inverting charge pump node, 2) a first diode electrically connected between the inverting charge pump node and a ground node, 3) a second diode electrically connected between the inverting charge pump node and the linear voltage regulator input node, and 4) a linear voltage regulator input capacitor electrically connected between the linear voltage regulator input node and the ground node. In this example and/or other examples, the inverting charge pump may be configured such that when the switching converter is in the ON state, the flying capacitor is charged with the charging current, and when the switching converter is in the OFF state, the charging current flows from the flying capacitor through the second diode to the linear voltage regulator input capacitor to generate the negative input voltage at the linear voltage regulator input node. In this example and/or other examples, the switching converter may be electrically connected to a switching converter feedback node, the power supply device may further comprise a feedback resistor divider electrically connected between the positive-bias output node and the switching converter feedback node, and the switching converter may be configured to modulate the positive-bias output voltage based on a feedback voltage measured via the resistor divider. In this example and/or other examples, the linear voltage regulator may be electrically connected to a linear voltage regulator feedback node, the power supply device may further comprise a feedback resistor divider electrically connected between the negative-bias output node and the linear voltage regulator feedback node, and the linear voltage regulator may be configured to regulate the negative-bias output voltage based on a feedback voltage measured via the resistor divider. In this example and/or other examples, the positive-bias output voltage may have a greater absolute value than that of the negative-bias output voltage. 
     In yet another example, a method of operating a power supply device, the method comprises generating an input voltage via a voltage source electrically connected to a switching converter input node of a switching converter, operating the switching converter in an ON state based on an operational duty cycle of the power supply device, wherein the power supply device is configured such that when the switching converter is in the ON state an inductor electrically connected between a first switching converter node and a second switching node of the switching converter is charged with a charging current, and operating the switching converter in an OFF state based on the operational duty cycle of the power supply device, wherein the power supply device is configured such that when the switching converter is in the OFF state, the switching converter modulates the input voltage to generate a positive-bias output voltage at a positive-bias output node of the power supply device, and the charging current flows from the inductor such that a negative input voltage is generated at a linear voltage regulator input node of a linear voltage regulator, and the linear voltage regulator regulates the negative input voltage to generate a negative-bias output voltage at a negative-bias output node of the power supply device. 
     It will be understood that the configurations and/or approaches described herein are exemplary in nature, and that these specific embodiments or examples are not to be considered in a limiting sense, because numerous variations are possible. The specific routines or methods described herein may represent one or more of any number of processing strategies. As such, various acts illustrated and/or described may be performed in the sequence illustrated and/or described, in other sequences, in parallel, or omitted. Likewise, the order of the above-described processes may be changed. 
     The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various processes, systems and configurations, and other features, functions, acts, and/or properties disclosed herein, as well as any and all equivalents thereof.