Abstract: A display device include a first light emitting diode (LED), a second LED, and at least one processor of a driver. The processor drives the first LED and the second LED. The processor determines a first pulse width associated with the first LED and a second pulse width associated with the second LED based on a level of brightness to be emitted by the first LED and the second LED. The processor also receives a gap clock and determines a first pulse start time and a first pulse end time for the first LED based on the first pulse width. Moreover, the processor determines a second pulse start time and a second pulse end time for the second LED based on the first pulse end time, the second pulse width, and/or the gap clock, in which the first pulse end time and the second pulse end time are different.

Abstract: Systems and methods for preserving a pulse width modulation (PWM) resolution while increasing the frequency of a pulse width modulation (PWM) clock are provided. An electronic display backlight system may include a backlight element and backlight dimming circuitry. The backlight element may be driven according to a pulse width modulation (PWM) signal over a PWM clock cycle equal to a multiple M of a baseline PWM clock frequency associated with a baseline PWM resolution. The backlight dimming circuitry may receive a brightness code of the baseline PWM resolution and generate the PWM signal at least in part by dividing the brightness code by M.

Abstract: Systems and methods for preserving a pulse width modulation (PWM) resolution while increasing the frequency of a pulse width modulation (PWM) clock are provided. An electronic display backlight system may include a backlight element and backlight dimming circuitry. The backlight element may be driven according to a pulse width modulation (PWM) signal over a PWM clock cycle equal to a multiple M of a baseline PWM clock frequency associated with a baseline PWM resolution. The backlight dimming circuitry may receive a brightness code of the baseline PWM resolution and generate the PWM signal at least in part by dividing the brightness code by M.

Abstract: A display device include a first light emitting diode (LED), a second LED, and at least one processor of a driver. The processor drives the first LED and the second LED. The processor determines a first pulse width associated with the first LED and a second pulse width associated with the second LED based on a level of brightness to be emitted by the first LED and the second LED. The processor also receives a gap clock and determines a first pulse start time and a first pulse end time for the first LED based on the first pulse width. Moreover, the processor determines a second pulse start time and a second pulse end time for the second LED based on the first pulse end time, the second pulse width, and/or the gap clock, in which the first pulse end time and the second pulse end time are different.

Abstract: Aspects of the subject technology relate to electronic devices having a display. The display includes a channel of light emitting diodes (LEDs) having controllable brightness levels and control circuitry coupled to the channel of LEDs. The control circuitry provides a pulse width modulated (PWM) signal having a duty cycle to control the brightness levels. An adaptive headroom control circuitry is configured to sense a headroom voltage signal for the channel of LEDs and apply a first time period for blanking the headroom voltage signal during the first time period that is associated with a settling time for the headroom voltage signal.

Abstract: Aspects of the subject technology relate to an electronic device with a display. The display includes a plurality of light-emitting diodes and first and second driver circuits coupled to the plurality of light-emitting diodes. The first driver circuit is configured to receive a first pulse-width modulated (PWM) signal to control a first current mirror branch and the second driver circuit to receive a second PWM signal to control a second current mirror branch to provide an extra N bits of resolution for controlling the plurality of the light-emitting diodes.

Abstract: Embodiments relate to sensing a current provided by a power supply circuit. The current sensing circuit includes a sense transistor for sensing the current provided by a main transistor, a driver for controlling a bias provided to the sense transistor and the main transistor, and a sense resistor for converting the sensed current to a voltage value. Moreover, the current sensing circuit includes a controller that modifies at least one of: (a) a resistance of the main transistor by adjusting the bias voltage provided by the driver, (b) a gain ratio between a load current and a sensing current by adjusting a number of individual devices that are active in the sense transistor, and (c) a resistance of the sense resistor.

Abstract: Embodiments relate to sensing a current provided by a power supply circuit. The current sensing circuit includes a sense transistor for sensing the current provided by a main transistor, a driver for controlling a bias provided to the sense transistor and the main transistor, and a sense resistor for converting the sensed current to a voltage value. Moreover, the current sensing circuit includes a controller that modifies at least one of: (a) a resistance of the main transistor by adjusting the bias voltage provided by the driver, (b) a gain ratio between a load current and a sensing current by adjusting a number of individual devices that are active in the sense transistor, and (c) a resistance of the sense resistor.

Abstract: A display may have display layers that form an array of pixels. The array of pixels may be illuminated using a backlight unit. The backlight unit may include multiple strings of light-emitting diodes (LEDs). The multiple LED strings may be controlled by one or more backlight driver integrated circuits (ICs). In a multi-driver IC architecture, an enable signal may be used to set a desired phase delay between the multiple ICs. One or more of the LED strings may exhibit a short fault. Depending on the number of faulty LED strings, the backlight unit can selectively throttle the maximum brightness of the display. The LED strings may receive an output voltage from a DC/DC converter and may be driven using a current driver. The DC/DC converter may be controlled by a headroom feedforward control circuit to ensure sufficient headroom for the current driver while suppressing acoustic noise.

Abstract: Embodiments relate to sensing a current provided by a power supply circuit. The current sensing circuit includes a sense transistor for sensing the current provided by a main transistor, a driver for controlling a bias provided to the sense transistor and the main transistor, and a sense resistor for converting the sensed current to a voltage value. Moreover, the current sensing circuit includes a controller that modifies at least one of: (a) a resistance of the main transistor by adjusting the bias voltage provided by the driver, (b) a gain ratio between a load current and a sensing current by adjusting a number of individual devices that are active in the sense transistor, and (c) a resistance of the sense resistor.

Abstract: A display may have an array of pixels illuminated using a backlight unit. The backlight unit may include multiple strings of light-emitting diodes (LEDs) and a boost converter for providing an output voltage to the multiple LED strings. The boost converter may have a single-phase single-switch, single-phase multi-switch, and/or multi-phase multi-switch configuration, where the switches are turned off when the peak current is reached. When transitioning from a single phase to a dual phase operation, the second (slave) phase current may be slowly ramped up. When transition from the dual phase to the single phase operation, the output voltage may be elevated while slowing ramping down the slave phase current. The boost converter may include a current detection circuit for adjusting the peak current of each phase to balance the average current levels. The boost converter may also include an in-rush current controller configured to sense a short fault.

Abstract: A display may have display layers that form an array of pixels. The array of pixels may be illuminated using a backlight unit. The backlight unit may include multiple strings of light-emitting diodes (LEDs). The multiple LED strings may be controlled by one or more backlight driver integrated circuits (ICs). In a multi-driver IC architecture, an enable signal may be used to set a desired phase delay between the multiple ICs. One or more of the LED strings may exhibit a short fault. Depending on the number of faulty LED strings, the backlight unit can selectively throttle the maximum brightness of the display. The LED strings may receive an output voltage from a DC/DC converter and may be driven using a current driver. The DC/DC converter may be controlled by a headroom feedforward control circuit to ensure sufficient headroom for the current driver while suppressing acoustic noise.

Abstract: A display may have an array of pixels illuminated using a backlight unit. The backlight unit may include multiple strings of light-emitting diodes (LEDs) and a boost converter for providing an output voltage to the multiple LED strings. The boost converter may have a single-phase single-switch, single-phase multi-switch, and/or multi-phase multi-switch configuration, where the switches are turned off when the peak current is reached. When transitioning from a single phase to a dual phase operation, the second (slave) phase current may be slowly ramped up. When transition from the dual phase to the single phase operation, the output voltage may be elevated while slowing ramping down the slave phase current. The boost converter may include a current detection circuit for adjusting the peak current of each phase to balance the average current levels. The boost converter may also include an in-rush current controller configured to sense a short fault.

Abstract: LED backlight circuits for a display and methods for operating the circuits are disclosed. The LED backlight circuit includes a set of drivers and a set of LED strings. A driver can be capable of coupling to any of the LED strings at a given time. Examples of the disclosure can include different configurations of drivers. In some instances, the driver may include an auxiliary transistor that allows the driver to settle before being switched to control a respective LED string. In some examples, the driver can include switches and an idle transistor that can be operated such that a low current path through the driver can exist when the driver is not coupled to a LED string.

Abstract: A power converter includes a buck converter with a low-side switch. During a discharge mode, current passes through the low-side switch to form a current loop. The low-side switch is typically closed synchronously with the opening of a high-side switch coupled to an input voltage level to the buck converter. The power converter also includes a high-side controller and a low-side controller, which together are configured to adjust the timing of the operation mode of the high-side controller between a storage mode and the discharge mode.

Abstract: Various systems, apparatuses, and methods are disclosed herein, which provide a new power conversion topology for isolated systems that does not include a transformer. Embodiments of the inventive systems comprise: a switching system utilizing high voltage, low leakage switches, e.g., Silicon Carbide (SiC) MOS-FETs; a power source; an inductor and a capacitor operating as a link stage resonant LC circuit; and a load. The switching system may be configured to be controlled in a synchronized ‘four phase’ control loop process, wherein the input switches are prevented from being closed at the same time as the output switches, thereby providing electrical isolation between the input power source and the load—without the use of a transformer. The techniques disclosed herein are applicable to any number of isolated systems that supply power to electronic systems such as: digital cameras, mobile phones, watches, personal data assistants (PDAs), portable music players, displays, and computers.

Abstract: Various systems and methods are disclosed herein, which provide isolated systems with an auxiliary, multi-signal digital feedback loop for reporting a plurality of different potential fault conditions in an output system (e.g., output short circuit, output over-voltage, output under-voltage, output over temperature, etc.) to a Primary Controller in an input system. The signals may be sent according to any desired standardized (or proprietary) data transmission protocols. Use of a digital feedback loop allows the signals to be passed to the Primary Controller more quickly than is allowed by traditional analog feedback paths—and while using only a single optocoupler device for the transmission of all fault conditions. The techniques disclosed herein are applicable to any number of isolated systems that supply power to electronic systems such as: digital cameras, mobile phones, watches, personal data assistants (PDAs), portable music players, monitors, as well as desktop, laptop, and tablet computers.

Abstract: This application relates to systems, methods, and apparatus for controlling a switching frequency of a boost or flyback converter to be above an audible frequency range when operating the boost or flyback converter in a pulse frequency modulation (PFM) mode. The boost or flyback converter uses one or more switches for converting power for a display panel. In order to boost the switching frequency when operating in the PFM mode, the boost or flyback converter can selectively implement certain current and/or voltage limits for pulses that are generated as a result of the switching. The current and/or voltage limits can be set according to a load of the boost or flyback converter, and a correspondence between the current and/or voltage limits and the loads can be stored in a lookup table accessible to the boost or flyback converter.

Abstract: A power converter includes a buck converter with a low-side switch. During a discharge mode, current passes through the low-side switch to form a current loop. The low-side switch is typically closed synchronously with the opening of a high-side switch coupled to an input voltage level to the buck converter. The power converter also includes a high-side controller and a low-side controller, which together are configured to adjust the timing of the operation mode of the high-side controller between a storage mode and the discharge mode.

Abstract: This disclosure relates to power converters that are capable of providing smooth transitions between multiple output voltage levels. The converter's output may need to be changed from, e.g., 5V to 12V, 15V, or 20V—based on the charging device's request. By using improved power converter designs comprising both a flyback converter circuit and variable-frequency buck converter circuit that may each be selectively coupled to an output load, a more smooth, e.g., monotonous, transition between output voltage levels may be achieved. In particular, by varying the switching frequency of the buck converter in a controlled way, the output voltage of the power converter may rise monotonically during the transition between output voltage levels. According to some embodiments, once the output of the buck converter has reached its maximum value, the buck converter may be disabled, and the flyback converter may be enabled to begin supplying the output voltage to the load.