Abstract: Examples are disclosed herein that relate to driving a resonant scanning mirror system using a linear LC resonant driving scheme. In one example, a resonant scanning mirror system includes a scanning mirror, first and second mirror drive elements, and a drive circuit to drive the scanning mirror at a resonant frequency. The drive circuit includes one or more signal sources configured to create a first source signal and a second source signal that is 180 degrees out of phase with the first source signal. The drive circuit further includes a buffer stage configured to receive the first and second source signals and output first and second drive signals, a first resonant LC stage configured to amplify the first drive signal for provision to the first mirror drive element, and a second resonant LC stage configured to amplify the second drive signal for provision to the second mirror drive element.

Abstract: A system includes a first sense circuit configured to provide a first output representative of sensed current provided by a first battery coupled to a first load. A second sense circuit is configured to provide a second output representative of sensed current provided by a second battery coupled to the first load. An input current controller is coupled to receive the respective first and second outputs and to couple between the second battery and the first load to control the current provided by the second battery.

Abstract: 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, the switching converter modulates an input voltage to generate a positive-bias output voltage at a positive-bias output node, the charging current flows from the inductor such that a negative input voltage is generated at a linear voltage regulator input node, and the linear voltage regulator regulates the negative input voltage to generate a negative-bias output voltage at a negative-bias output node.

Abstract: A system for facial movement detection with reduced size and reduced cost by employing a novel resonant drive and sampling scheme is disclosed. An example battery operated system includes a driver circuit, an LC resonance circuit formed by an inductor circuit and a capacitance from an antenna, and a sample and hold circuit. The driver circuit can be configured by a controller to generate a drive signal for the LC resonance circuit, which has a resonant frequency that changes as the capacitance of the antenna varies responsive to facial movements of the user. The sample and hold circuit samples the output of the LC resonance circuit responsive to a falling edge of the drive signal for the LC resonance circuit, wherein an output of the sample and hold circuit is a sampled sense signal that may be further processed to detect facial movements of the user.

Abstract: Examples are disclosed that relate to monitoring an emission state of light sources. One example provides a light emitting circuit comprising a power source, one or more light sources connected to an output of the power source, and a control circuit comprising a pulsed voltage source and a control transistor configured to regulate a current through the light sources based upon an output of the pulsed voltage source. The light emitting circuit further comprises a monitor transistor comprising a gate connected to an output of the light sources such that a voltage at the output of the light sources controls an output of the monitor transistor, and a monitor transistor detector connected to the output of the monitor transistor. The monitor transistor detector is configured to monitor a state of the one or more light sources based upon a state of the output of the monitor transistor.

Abstract: A time-multiplexing resonant drive scheme is described that reuses an inductor circuit for multiple functional purposes in a Mixed Reality (MR) device. A driver circuit and a multiplexer circuit are dynamically configured by a controller circuit for three operating modes. In the first mode, energy is coupled from a battery to the inductor circuit in a forward direction to charge the inductor circuit and generate a positive power supply voltage. In the second mode, energy is coupled from to the inductor circuit in a reverse direction to charge the inductor circuit and generate a negative power supply voltage. In the third mode, the inductor is operated with an antenna as part of a resonance drive circuit, where facial movements of the user can be detected based on the response. Reduced component count and reduced cost requirements are achieved by the described scheme.

Abstract: A system and method generate an alternating current (AC) input signal by a digitally controlled resonant drive circuit. The method includes driving a face tracking sensor with the input signal. An output signal is received from the face tracking sensor and an amplitude of the output signal is compared to a target amplitude. A duty cycle of the resonant drive circuit is modified based on the comparison to control the amplitude of the output signal about the target amplitude.

Abstract: A system includes a first sense circuit configured to provide a first output representative of sensed current provided by a first battery coupled to a first load. A second sense circuit is configured to provide a second output representative of sensed current provided by a second battery coupled to the first load. An input current controller is coupled to receive the respective first and second outputs and to couple between the second battery and the first load to control the current provided by the second battery.

Abstract: A time-multiplexing resonant drive scheme is described that reuses an inductor circuit for multiple functional purposes in a Mixed Reality (MR) device. A driver circuit and a multiplexer circuit are dynamically configured by a controller circuit for three operating modes. In the first mode, energy is coupled from a battery to the inductor circuit in a forward direction to charge the inductor circuit and generate a positive power supply voltage. In the second mode, energy is coupled from to the inductor circuit in a reverse direction to charge the inductor circuit and generate a negative power supply voltage. In the third mode, the inductor is operated with an antenna as part of a resonance drive circuit, where facial movements of the user can be detected based on the response. Reduced component count and reduced cost requirements are achieved by the described scheme.

Abstract: A resonant drive circuit for a capacitive sensor device includes a resonant LC stage, a signal source, and an amplifier stage. The resonant LC stage includes an inductorless floating gyrator circuit electrically connected to a sense capacitor. The inductorless floating gyrator circuit is configured to synthesize a fixed inductance. The resonant LC stage is configured to output a sensed capacitance signal based on the fixed inductance and a change in capacitance of the sense capacitor. The signal source is configured to output a reference signal. The amplifier stage is configured to receive the sensed capacitance signal and the reference signal and output a measured capacitance signal that indicates a difference in one or more of amplitude and phase between the sensed capacitance signal and the reference signal.

Abstract: A method for operating a display comprising a plurality of emission diodes. For each emission diode, an output brightness of the emission diode is monitored over a range of compliance voltages. Based on the monitored output brightness of the emission diode, an inflection voltage is determined. At the inflection voltage, increasing a commanded compliance voltage does not yield an above-threshold increase in output brightness. Further, decreasing the commanded compliance voltage from the inflection voltage yields an above-threshold decrease in output brightness. In response to receiving a request for the emission diode to operate at a peak output brightness, an applied compliance voltage is commanded that is within a threshold voltage of the inflection point voltage.

Abstract: The techniques disclosed herein provide low power, efficient systems, devices and circuits that detect facial movements of a user of a Mixed Reality (MR) device. An example battery operated system includes a pulse driver that generates pulse signals at a set frequency, while operated below the battery voltage. An LC filter receives the pulse signals and generates a transient response based on a capacitance value associated with an antenna. The capacitance of the antenna varies responsive to facial movements of the user based on the varying distance of the antenna to the users skin. A coupling capacitor AC couples the output of the LC filter to other system components, where the AC coupled output of the LC filter includes a detected signal amplitude and a detected signal phase of the LC filter responsive to facial movements of the user.

Abstract: Examples are disclosed that relate to monitoring an emission state of light sources. One example provides a light emitting circuit comprising a power source, one or more light sources connected to an output of the power source, and a control circuit comprising a pulsed voltage source and a control transistor configured to regulate a current through the light sources based upon an output of the pulsed voltage source. The light emitting circuit further comprises a monitor transistor comprising a gate connected to an output of the light sources such that a voltage at the output of the light sources controls an output of the monitor transistor, and a monitor transistor detector connected to the output of the monitor transistor. The monitor transistor detector is configured to monitor a state of the one or more light sources based upon a state of the output of the monitor transistor.

Abstract: Examples are disclosed herein that relate to driving a resonant scanning mirror system using a linear LC resonant driving scheme. In one example, a resonant scanning mirror system includes a scanning mirror, first and second mirror drive elements, and a drive circuit to drive the scanning mirror at a resonant frequency. The drive circuit includes one or more signal sources configured to create a first source signal and a second source signal that is 180 degrees out of phase with the first source signal. The drive circuit further includes a buffer stage configured to receive the first and second source signals and output first and second drive signals, a first resonant LC stage configured to amplify the first drive signal for provision to the first mirror drive element, and a second resonant LC stage configured to amplify the second drive signal for provision to the second mirror drive element.

Abstract: Examples are disclosed herein related to controlling a scanning display system. One example provides a display device comprising a light source, a scanning mirror system configured to scan light from the light source, and a controller configured to control the scanning mirror system to scan the light by synthesizing in a time domain a mirror control waveform that comprises a linear scan portion and a retrace portion stitched to the linear scan portion, the mirror control waveform being continuous and having an arbitrary timing that is adjustable by the controller between scan cycles.

Abstract: Examples are disclosed herein related to controlling a scanning display system. One example provides a display device comprising a light source, a scanning mirror system configured to scan light from the light source, and a controller configured to control the scanning mirror system to scan the light by synthesizing in a time domain a mirror control waveform that comprises a linear scan portion and a retrace portion stitched to the linear scan portion, the mirror control waveform being continuous and having an arbitrary timing that is adjustable by the controller between scan cycles.

Abstract: A piezo MEMS mirror system that includes a drive system that drives a piezo MEMS mirror that generates an image on a portable device display. The drive system includes a DC-AC converter that operates to convert the DC power provided by the battery to AC power. The DC-AC converter may generate the AC power having a peak voltage that is at an intermediate level—being between the DC voltage of the battery, and the peak AC voltage generated by the drive system. The drive system also includes an output filter that uses a series-coupled inductance system (perhaps inductively coupled inductors in a differential mode circuit) in conjunction with a capacitance of the piezo MEMS mirror (and perhaps tuning capacitors to account for mirror fabrication deviations) to amplify the AC voltage of the AC power at a mechanical resonant frequency of the piezo MEMS mirror.

Abstract: A piezo MEMS mirror system that includes a drive system that drives a piezo MEMS mirror that generates an image on a portable device display. The drive system includes a DC-AC converter that operates to convert the DC power provided by the battery to AC power. The DC-AC converter may generate the AC power having a peak voltage that is at an intermediate level—being between the DC voltage of the battery, and the peak AC voltage generated by the drive system. The drive system also includes an output filter that uses a series-coupled inductance system (perhaps inductively coupled inductors in a differential mode circuit) in conjunction with a capacitance of the piezo MEMS mirror (and perhaps tuning capacitors to account for mirror fabrication deviations) to amplify the AC voltage of the AC power at a mechanical resonant frequency of the piezo MEMS mirror.