Abstract: A voltage waveform similar to a waveform of a magnetizing current of an isolation transformer and immune to high frequency oscillatory resonant behavior is developed across a capacitor of a series resistor and capacitor connection connected in parallel with a synchronous rectifier. A simple logic circuit produces a waveform for controlling the synchronous rectifier which is not subject to significant turn on delay or early turn off caused by oscillatory resonances among parasitic inductances and capacitances. Improved timing accuracy of a synchronous converter provides improved power converter accuracy, particularly for flyback converters which are commonly used in converters for supplying power to offline electrical devices but are subject to oscillatory resonant behaviors that cannot be adequately damped at switching frequencies sufficiently high to support miniaturization of adapters.

Abstract: A power factor correction (PFC) power converter, particularly of a multiphase totem-pole or other topology presenting a switching bridge that can potentially provide bi-directional power transfer control, reduces a nominal switching frequency and achieves zero voltage switching over an increased portion of a half line cycle by providing positive or inverse coupling of inductors in an inductor structure that can be formed of a multi-layer printed circuit board such that at least three different inductances are presented during each half line cycle period; allowing increased switching frequency and simplifying EMI filtering arrangements. Parasitic capacitances can be balanced with additional coupled windings to reduce differential mode and common mode noise. The PFC power converter is particularly applicable to provide bi-directional power control from an on-board battery charger in an electrically powered vehicle.

Abstract: In a cascode switching device, avalanche breakdown of a control transistor and loss of soft switching or zero voltage switching in a high voltage normally-on depletion mode transistor having a negative switching threshold voltage and the corresponding losses are avoided by providing additional capacitance in parallel with a parallel connection of drain-source parasitic capacitance of the control transistor and gate-source parasitic capacitance of the high voltage, normally-on transistor to form a capacitive voltage divider with the drain-source parasitic capacitance of the high voltage, normally-on transistor such that the avalanche breakdown voltage of the control transistor cannot be reached. The increased capacitance also assures that the drain source parasitic capacitance of the high voltage, normally-on transistor is fully discharged before internal turn-on can occur.

Abstract: In one example, an omnidirectional wireless power transfer system includes high frequency power generator configured to generate a supply of high frequency oscillating power, a number of transmitter-side resonant tank circuits electrically coupled to the high frequency power generator, a receptacle including a number of coils arranged for omnidirectional power transfer to an electronic device placed in the receptacle, and a controller configured to activate individual ones of the transmitter-side resonant tank circuits to wirelessly transmit power to the electronic device through near-field resonant inductive coupling. In one example, the receptacle can be embodied as a bowl, and the controller can activate individual ones of the transmitter-side resonant tank circuits over time to generate an omnidirectional field distribution for wireless power transmission. In other aspects, various transmitter-side and receiver-side tank circuits for coupling independent resonance and ZVS operation are described.

Abstract: Approximately one-half of the loss of delivered power from a solar panel having photovoltaic (PV) cells connected in series to form sub-panels due to shading is recovered at low hardware cost by connecting sub-panels in series and providing maximum power point tracking control in common for the series connected sub-panels such that the respective sub-panels produce equal voltages even in the presence of shading of a portion of one or more sub-panels. By doing so, the input voltage of respective power converters which control the voltage at which each sub-panel is operated can be placed close to the maximum power point of each sub-panel regardless of shading and maximum total power harvested even though the respective sub-panels are not operated at optimum voltages.

Abstract: Peak current, valley current or average current mode controlled power converters in either digital or analog implementations obtain a stabilized feedback loop and allow high system bandwidth design by use of an external ramp generator using a slope computation equation or design parameters based on fixing the quality factor of a double pole at one-half of the switching frequency at a desired value The slope of the external ramp waveform is tuned automatically with knowledge of the slope change in the waveform of inductor current of a power converter derived by differentiating a waveform in the current feedback loop. This autotuning of the external ramp generator provides immunity of quality factor change under variations of duty cycle, component values of topological change of the power converter.

Abstract: A vitrectomy apparatus is provided, including a pressure source, a cut valve connected to the pressure source, the cut valve configured to be turned on and off to provide pressure to selectively extend and retract a vitrectomy cutting device, a sensor configured to sense pressure provided from the cut valve, and a controller configured to control operation of the cut valve based on pressure sensed by the sensor. The controller is configured to monitor an amount of dwell time the vitrectomy cutting device remains open and monitor aspiration rate, and control a rate of material processed by the vitrectomy cutting device based on amount of dwell time and aspiration rate.

Abstract: Operation of a switching power converter having an output capacitor having a small equivalent series resistance (ESR) is stabilized and jitter reduced by sensing capacitor current with gain and combining the resulting signal with the output voltage signal to provide a feedback signal to control switching of the power converter. capacitor current can be sensed without interfering with operation of the filter capacitor by providing a branch circuit having a time constant matched to the output or filter capacitor but an arbitrarily high impedance so as to be effectively lossless. The gain provided in the capacitor current signal can be tuned to provide optimally short settling time after load transients; generally within one switching cycle. Matching of time constants and/or tuning of gain can be performed automatically.

Abstract: A vitrectomy apparatus is provided, including a pressure source, a cut valve connected to the pressure source, the cut valve configured to be turned on and off to provide pressure to selectively extend and retract a vitrectomy cutting device, a sensor configured to sense pressure provided from the cut valve, and a controller configured to control operation of the cut valve based on pressure sensed by the sensor.

Abstract: A vitrectomy apparatus is provided, including a pressure source, a cut valve connected to the pressure source, the cut valve configured to be turned on and off to provide pressure to selectively extend and retract a vitrectomy cutting device, a sensor configured to sense pressure provided from the cut valve, and a controller configured to control operation of the cut valve based on pressure sensed by the sensor. The controller is configured to monitor pressures encountered and alter cut valve timing based on pressure conditions previously encountered.

Abstract: At least one shield member interposed between primary and secondary windings of a transformer and connected to the primary and/or secondary windings forms a distributed parasitic capacitance between the shield member and either the winding to which it is not connected or another shield member connected to that winding. Connections are made to the respective transformer windings such that the voltage distributions thus developed cause complementary common mode noise to be conducted in opposite directions in respective portions of the parasitic capacitance such that net common mode current can be made arbitrarily small without requiring that both sides of the distributed parasitic capacitance have complementary or equal voltage distributions. Such complementary common mode currents can be achieved by dividing opposing shield members or developing a voltage distribution in a single shield member in accordance with Faraday's Law.

Abstract: Aspects of capacitor voltage ripple reduction in modular multilevel converters are described herein. In one embodiment, a power converter system includes a modular multilevel converter (MMC) electrically coupled and configured to convert power between two different power systems. The MMC includes one or more phase legs having a cascade arrangement of switching submodules, where the switching submodules include an arrangement of switching power transistors and capacitors. The MMC further includes a control loop including a differential mode control loop and a common mode control loop. The differential control loop is configured to generate a differential control signal based on a target modulation index to reduce fundamental components of voltage ripple on the capacitors, and the common mode control loop is configured to inject 2nd order harmonic current into a common mode control signal to reduce 2nd order harmonic components of the voltage ripple on the capacitors.

Abstract: A low profile power converter structure is provide wherein volume is reduced and power density is increased to approach 1 KW/in3 by at least one of forming an inductor as a body of magnetic material embedded in a substrate formed by a plurality of printed circuit board (PCB) lamina and forming inductor windings of PCB cladding and vias which may be of any desired number of turns and may include inversely coupled windings and which provide a lateral flux path, forming the body of magnetic material from high aspect ratio flakes of magnetic material which are aligned with the inductor magnetic field in an insulating organic binder and hot-pressed and providing a four-layer architecture comprising two layers of PCB lamina including the embedded body of magnetic material, a shield layer and an additional layer of PCB lamina, including cladding for supporting and connecting a switching circuit, a capacitor and the inductor.

Abstract: In a two-stage power converter providing voltage regulation in a first stage, zero voltage switching (ZVS) is provided in switches in an unregulated, constant frequency second stage of a two-stage power converter by an inductor of a CLL resonant circuit connected in parallel with both a series connection of an external inductor and a primary winding of one or more transformers connected in series and an output of the switching circuit so that the output capacitances of the switches can be charged and discharged, respectively, by current in the parallel-connected inductor and independently of current in the magnetizing inductance of the transformer. Therefore, the magnetizing inductance of the transformer can be made sufficiently large to balance currents delivered to respective loads as is particularly desirable for driving a plurality of unbalanced LED strings independently of the value of the parallel-connected inductor which is desirably small.

Abstract: A vitrectomy apparatus is provided, including a pressure source, a cut valve connected to the pressure source, the cut valve configured to be turned on and off to provide pressure to selectively extend and retract a vitrectomy cutting device, a sensor configured to sense pressure provided from the cut valve, and a controller configured to control operation of the cut valve based on pressure sensed by the sensor. The controller is configured to monitor pressures encountered and alter cut valve timing based on pressure conditions previously encountered.

Abstract: A vitrectomy apparatus is provided, including a pressure source, a cut valve connected to the pressure source, the cut valve configured to be turned on and off to provide pressure to selectively extend and retract a vitrectomy cutting device, a sensor configured to sense pressure provided from the cut valve, and a controller configured to control operation of the cut valve based on pressure sensed by the sensor.

Abstract: an amount of charge transferred by a power converter is estimated by developing a signal that is a combination of signals representing an output voltage of a power converter and an inductor current of the power converter, charging a capacitor with a current proportional to that signal and comparing a voltage developed across the capacitor due to that charging to develop a signal for initiating a pulse to control input of power from a voltage source to the power converter. By using a signal developed in this way, response to both step-up and step-down transients can be improved and, in multi-phase embodiments, ripple cancellation problems such as noise susceptibility and loss of pulse generation can be entirely avoided.

Abstract: A two-stage power converter architecture including an isolation transformer and rectification of the isolation transformer output by an LLC resonant circuit and methodology for operating the same feeds an output voltage back to a circuit for generating waveforms for controlling a totem pole circuit to provide output voltage regulation as well as rectification of AC input voltage. The circuit for controlling the totem pole circuit may also be responsive to the AC input power waveform to provide power factor correction (PFC), in which case, the feedback signal provides additional pulse width modulation of the PFC signals. Bus capacitor size may also be reduced by injecting harmonics of the AC input waveform into the feedback signal which also serves to substantially maintain efficiency of the (preferably LLC) resonant second stage.

Abstract: A resonant power converter is disclosed with a driving circuit generating a switching signal connecting power to a resonant tank circuit, with a voltage monitoring circuit measuring a voltage output and a load current. A micro-controller is operable with a control circuit for multiple step sampling with the switching signal at a switching frequency to settle the resonant circuit determined from the voltage output and load current. A fast load transient response at a high frequency with the resonant circuit provides the multiple step sampling to ensure enough time for micro-controller to calculate. Optimal trajectory control facilitates a burst mode of high frequency with the resonant circuit using adaptive multiple step sampling for an on-time to extend the burst operation range. A soft start-up process uses the micro-controller processing in multiple stages.

Abstract: A power converter using constant on-time (COT) or ramp pulse modulation (RPM) control achieves more rapid resumption of steady-state operation after a step-up load transient by extending an on-time of a switching pulse by interrupting a ramp voltage waveform that is compared with a threshold that equals a threshold voltage at the termination of a switching pulse or increasing a voltage with which the ramp voltage is compared. These techniques are applied to both single-phase and multi-phase power converters.