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 device but are subject to oscillatory resonant behaviors that cannot be adequately damped at switching frequencies sufficiently high to support miniaturization of adapters.

Abstract: Output current ripple is reduced in a three-level DC-DC power converter by connecting a plurality of phase legs in parallel between a source of input power and an output of the power converter and conducting power from the source of input power to the power converter output in an interleaved manner. The large current that results from such interleaved operation is reduced to acceptable levels, potentially less than the output current ripple of the power converter by providing inversely coupled inductors having a mutual inductance preferably greater than the inductor of the power converter in respective phase legs and in series in the circulating current path to avoid any need to increase the power converter inductance due to the circulating current. The inductor and inversely coupled inductors are preferably integrated into a single magnetic element of compact design.

Abstract: Providing a fast current sensor direct feedback path to a modulator for controlling switching of a switched power converter in addition to an integrating feedback path which monitors average current for control of a modulator provides fast dynamic response consistent with system stability and average current mode control. Feedback of output voltage for voltage regulation can be combined with current information in the integrating feedback path to limit bandwidth of the voltage feedback signal.

Abstract: By setting switching instants of a switching circuit of a resonant power converter based on current in a resonant circuit reaching a current limit of a current limitation band, soft start-up of the power converter can be achieved to avoid or limit electrical stress with full control over a trade-off between time required to settle to a full load steady-state mode of operation and the amount of electrical stress permitted while soft start up switching frequency is automatically optimized.

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: A low profile inductor structure suitable for use in a high power density power converter has one or more windings formed by vias through a thin, generally planar body of magnetic material forming the inductor core and conductive cladding on the body of magnetic material or material covering the magnetic material body. Variation of inductance with load current and other operational or environmental parameters is reduced to any desired degree by forming a slot that removes all or a portion of the magnetic material between the locations of the vias.

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: Pulse width modulation is provided for controlling a resonant power converter, particularly for dimming of light emitting diode arrays without loss of efficiency. Dynamic oscillation due to the beginning of a pulse width modulated pulse burst is limited by shortening of the first and/or last pulse of a pulse bust such that the first pulse of a subsequent pulse burst close to or to connect with a full load steady-state voltage/current trajectory of the power converter. Pulse shortening made be made substantially exact to virtually eliminate dynamic oscillation but substantial reduction in dynamic oscillation is provided if inexact or even performed randomly.

Abstract: Zero voltage switching (ZVS) is provided in switches of a switching circuit in a second stage of a power converter by an inductor of a CLL resonant circuit connected in parallel with both a primary winding of one or more transformers connected in series and an output of the switching circuit so that the parasitic output capacitances of the switches can be charged and discharged, respectively, during the dead-time of the switching circuit by current in the 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 that may be unbalanced as is particularly desirable for driving a plurality of LED strings for illumination and is consistent with controlled dimming of the LED strings.

Abstract: In a multi-phase power converter using a phase-locked loop (PLL) arrangement for interleaving of pulse frequency modulated (PFM) pulses of the respective phases, improved transient response, improved stability of high bandwidth output voltage feedback loop, guaranteed stability of the PLL loop and avoidance of jittering and phase cancellation issues are achieved by anchoring the bandwidth at the frequency of peak phase margin. This methodology is applicable to multi-phase power conveners of any number of phases and any known or foreseeable topology for individual phases and is not only applicable to power converters operating under constant on-time control, but is extendable to ramp pulse modulation (RPM) control and hysteresis control. Interleaving of pulses from all phases is simplified through use of phase managers with a reduced number of PLLS using hybrid interleaving arrangements that do not exhibit jittering even when ripple is completely canceled.

Abstract: Response of a variable frequency switching constant on-time or adaptive on-time controlled power converter to a large step-up or step-down change in load is improved with a simple circuit that detects magnitude and polarity of a change in output voltage and initiates, extends or terminates conduction of power pulses from an input source through said power converter. Both the amplitude and duration of undershoot or overshoot of the transient response are reduced or, alternatively, the capacitance of an output filter may be significantly reduced and still provide comparable transient performance. The fast adaptive on-time control is applicable to multi-phase power converters using phase managers or one or more phase-locked loops for interleaving of power pulses.

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: A multi-channel constant current source particularly suitable for driving an array of light-emitting diodes as an illumination apparatus provides a power source stage voltage regulator for providing a variable voltage using pulse width modulation as an input to a plurality of constant current driver channels to regulate the constant current provided. Pulse width modulation thus allows both the power source stage and the constant current driver operating frequencies to be decoupled and individually optimized to maintain efficiency while emulating dimming effects of, for example, incandescent bulbs, over a full range of light output flux. Pulse width modulation can also be employed in the constant current channel drivers to avoid chromaticity shift during dimming.

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: 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: By setting switching instants of a switching circuit of a resonant power converter based on current in a resonant circuit reaching a current limit of a current limitation band, soft start-up of the power converter can be achieved to avoid or limit electrical stress with full control over a trade-off between time required to settle to a full load steady-state mode of operation and the amount of electrical stress permitted while soft start up switching frequency is automatically optimized.

Abstract: Pulse width modulation is provided for controlling a resonant power converter, particularly for dimming of light emitting diode arrays without loss of efficiency. Dynamic oscillation due to the beginning of a pulse width modulated pulse burst is limited by shortening of the first and/or last pulse of a pulse bust such that the first pulse of a subsequent pulse burst close to or to connect with a full load steady-state voltage/current trajectory of the power converter. Pulse shortening made be made substantially exact to virtually eliminate dynamic oscillation but substantial reduction in dynamic oscillation is provided if inexact or even performed randomly.

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: 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: 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.