Scholarly Works, Center for Power Electronics Systems

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https://hdl.handle.net/10919/111744

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Zero-current transition PWM converters
(United States Patent and Trademark Office, 1996-01-23)
A zero-current transition pulse-width modulated (ZCT-PWM) d.c.-d.c. converter allows minority-carrier semiconductor devices such as, for example, bipolar junction transistors (BJTs), insulated gate bipolar transistors (IGBTs), MOSFET controlled thyristors (MCTs), and gate turn-off thyristors (GTOs), to be used as switches for high-power, high frequency applications. The ZCT-PWM converter comprises a shunt resonant branch inserted into a conventional PWM converter circuit. The resonant branch comprises a resonant inductor (Lr), a resonant capacitor (Cr), an auxiliary switch (S1), and an auxiliary diode (D1). The resonant branch is only active during a relatively short switching time in order to create a zero-current switch condition for the main pulse-modulating switch (S) without substantially increasing voltage or current stresses.
A diffusion-viscous analysis and experimental verification of defect formation in sintered silver bond-line
Xiao, Kewei; Ngo, Khai D. T.; Lu, Guo-Quan (Cambridge University Press, 2014-04-01)
The low-temperature joining technique (LTJT) by silver sintering is being implemented by major manufacturers of power electronic devices and modules for bonding power semiconductor chips. A common die-attach material used with LTJT is a silver paste consisting of silver powder (micrometer- or nanometer-sized particles) mixed in organic solvent and binder formulation. It is believed that the drying of the paste during the bonding process plays a critical role in determining the quality of the sintered bond-line. In this study, a model based on the diffusion of solvent molecules and viscous mechanics of the paste was introduced to determine the stress and strain states of the silver bond-line. A numerical simulation algorithm of the model was developed and coded in the C++ programming language. The numerical simulation allows determination of the time-dependent physical properties of the silver bond-line as the paste is being dried with a heating profile. The properties studied were solvent concentration, weight loss, shrinkage, stress, and strain. The stress is the cause of cracks in the bond-line and bond-line delamination. The simulated results were verified by experiments in which the formation of bond-line cracks and interface delamination was observed during the pressure-free drying of a die-attach nanosilver paste. The simulated results were consistent with our earlier experimental findings that the use of uniaxial pressure of a few mega-Pascals during the drying stage of a nanosilver paste was sufficient to produce high-quality sintered joints. The insight offered by this modeling study can be used to develop new paste formulations that enable pressure-free, low-temperature sintering of the die-attach material to significantly lower the cost of implementing the LTJT in manufacturing.
Structural Resemblance Between Droop Controllers and Phase-Locked Loops
Zhong, Qing-Chang; Boroyevich, Dushan (IEEE, 2016)
It is well known that droop control is fundamental to the operation of power systems and now the parallel operation of inverters, while phase-locked loops (PLLs) are widely adopted in modern electrical engineering. In this paper, it is shown at first that droop control and PLLs structurally resemble each other. This bridges the gap between the two communities working on droop control and PLLs. As a result, droop controllers and PLLs can be improved and further developed via adopting the advancements in the other field. This finding is then applied to operate the conventional droop controller for inverters with inductive output impedance to achieve the function of PLLs, without having a dedicated synchronization unit. Extensive experimental results are provided to validate the theoretical analysis.
Optimal trajectory control for LLC resonant converter for LED PWM dimming
(United States Patent and Trademark Office, 2016-03-01)
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.
Optimal trajectory control for LLC resonant converter for soft start-up
(United States Patent and Trademark Office, 2016-04-19)
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.
Iaverage current mode (ACM) control for switching power converters
(United States Patent and Trademark Office, 2016-05-17)
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.
Method and apparatus for driving a power device
(United States Patent and Trademark Office, 2016-12-27)
Aspects of the disclosure provide a circuit for driving a power switch. The circuit includes a first circuit configured to provide a charging current to charge a control terminal of the power switch, a second circuit configured to provide a discharging current to discharge the control terminal of the power switch, and a control circuit configured to provide control signals to the first circuit and the second circuit to activate/deactivate the first circuit and the second circuit. At least one of the charging current and the discharging current ramps from a first level to a second level at a rate.
Two-stage multichannel LED driver with CLL resonant circuit
(United States Patent and Trademark Office, 2017-01-10)
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.
High frequency integrated point-of-load power converter with embedded inductor substrate
(United States Patent and Trademark Office, 2017-02-07)
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.
System and method for impedance measurement using series and shunt injection
(United States Patent and Trademark Office, 2017-02-07)
A method for impedance measurement in a three-phase AC system is provided. The method includes injecting a shunt perturbation signal into the three-phase AC system and collecting a response to the shunt perturbation signal, and injecting a series perturbation signal into the three-phase AC system and collecting a response to the series perturbation signal. The response to the shunt perturbation signal and the response to the series perturbation signal are then transferred from abc coordinate to dq coordinates. At least one impedance of the three-phase AC system is calculated based on the response to the shunt perturbation signal and the response to the series perturbation signal.
Method and apparatus for current/power balancing
(United States Patent and Trademark Office, 2017-02-28)
Aspects of the disclosure provide a power circuit that includes a first switch circuit in parallel with a second switch circuit. The first switch circuit and the second switch circuit are coupled to a first driving node, a second driving node, a source node and a drain node via interconnections. The power circuit receives a control signal between the first driving node and the second driving node to control a current flowing from the drain node to the source node through the first switch circuit and the second switch circuit. In the power circuit, a first interconnection and a second interconnection of the interconnections are inductively coupled to balance the current flowing through the first switch circuit and the second switch circuit.
Method for reducing or eliminating conducted common mode noise in a transformer
(United States Patent and Trademark Office, 2017-03-07)
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.
V^2 power converter control with capacitor current ramp compensation
(United States Patent and Trademark Office, 2017-03-21)
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.
System and method for impedance measurement using chirp signal injection
(United States Patent and Trademark Office, 2017-04-11)
A method for impedance measurement using chirp signal injection is provided. The method includes injecting at least one chirp signal into the three-phase AC system, and collecting at least one response to the at least one chirp signal. The method further includes transferring the at least one response from abc coordinates to dq coordinates. At least one impedance is calculated based on the at least one response to the at least one chirp signal.
Anti-islanding detection for three-phase distributed generation
(United States Patent and Trademark Office, 2017-04-25)
Wobbling the operating frequency of a phase-locked loop (PLL), preferably by adding a periodic variation is feedback gain or delay in reference signal phase allows the avoidance of any non-detection zone that might occur due to exact synchronization of the phase locked loop operating frequency with a reference signal. If the change in PLL operating frequency is periodic, it can be made of adequate speed variation to accommodate and time requirement for islanding detection or the like when a reference signal being tracked by the PLL is lost. Such wobbling of the PLL operating frequency is preferably achieved by addition a periodic variable gain in a feedback loop and/or adding a periodically varying phase delay in a reference signal and/or PLL output.
Method and apparatus to improve power device reliability
(United States Patent and Trademark Office, 2017-05-23)
Aspects of the disclosure provide a power device that includes an upper power module and a lower power module. The upper power module and the lower power module are coupled in series between two supply voltages, and are respectively controlled by a first control signal and a second control signal. Interconnections of the power device are inductively coupled to prevent reliability issues, such as crosstalk, self turn on, self sustained oscillation, and the like.
External ramp autotuning for current mode control of switching converter
(United States Patent and Trademark Office, 2017-06-13)
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.
Maximum power point tracking for solar panels
(United States Patent and Trademark Office, 2017-06-20)
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.
Avoiding internal switching loss in soft switching cascode structure device
(United States Patent and Trademark Office, 2017-08-15)
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.
Correlation between tunability and anisotropy in magnetoelectric voltage tunable inductor (VTI)
Yan, Yongke; Geng, Liwei D.; Zhang, Lujie; Gao, Xiangyu; Gollapudi, Sreenivasulu; Song, Hyun-Cheol; Dong, Shuxiang; Sanghadasa, Mohan; Ngo, Khai D. T.; Wang, Yu U.; Priya, Shashank (Springer Nature, 2017-11-22)
Electric field modulation of magnetic properties via magnetoelectric coupling in composite materials is of fundamental and technological importance for realizing tunable energy efficient electronics. Here we provide foundational analysis on magnetoelectric voltage tunable inductor (VTI) that exhibits extremely large inductance tunability of up to 1150% under moderate electric fields. This field dependence of inductance arises from the change of permeability, which correlates with the stress dependence of magnetic anisotropy. Through combination of analytical models that were validated by experimental results, comprehensive understanding of various anisotropies on the tunability of VTI is provided. Results indicate that inclusion of magnetic materials with low magnetocrystalline anisotropy is one of the most effective ways to achieve high VTI tunability. This study opens pathway towards design of tunable circuit components that exhibit field-dependent electronic behavior.

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