Shangzhi Pan

A Review of High-Frequency Power Distribution Systems: For Space, Telecommunication, and Computer Applications

High-frequency AC (HFAC) power distribution systems have been the subject of great interest over the last several decades. This paper presents a thorough review of different HFAC power distribution architectures on which the authors have worked in the last 30 years. The review is focused on the HFAC power architectures and topologies for space, telecommunications, and computer applications. Detail of each architecture is given and evaluated in terms of performance specific to each application.

Novel Digital Control Architecture with Non-Linear Control Algorithms Exhibiting Very Fast Transient Response

A dual-voltage-loop digital control architecture with non-linear control algorithm is proposed in this paper. An adaptive voltage positioning (AVP) control unit was generalized to achieve adaptive voltage positioning, by generating dynamic voltage reference and dynamic current reference. A dynamic reference step adjustment method lowers the high speed requirement of reference updating clock; a non-linear control minimizes the transient-assertion-to-action delay and maximizes the inductor current slew rate; and a transient detection circuit recognizes the load transient state in a manner adaptive to the amount and slew rate of load current transient. Theoretical, simulation and experimental results prove the effective operation and excellent dynamic performance of the digital controller.

A New Digital Adaptive Voltage Positioning Technique with Dynamically Varying Voltage and Current References

A digital adaptive voltage positioning (digital AVP) technique with fast transient response for voltage regulators (VRs) is proposed in this paper. The proposed digital control architecture operates with fixed-frequency peak current mode control. Two digital-to-analog converters (DACs) are used instead of analog-to-digital converters (ADCs), thus significantly reducing system complexity. The control law is straightforward and no compensator is involved in the control loop, which greatly reduces the computation delay. Both the voltage and current references are changed dynamically at DAC clock frequency to achieve fast transient response. Furthermore, dynamic reference step adjustment method is employed to reduce the high-speed requirement on reference updating clock without compromising steady-state performance. Nonlinear control, including operation state recognition, multimode operation, decision-making and multiturn-on/turn-off control schemes, is used to minimize the transient-assertion-to-action delay and maximize the inductor current slew rate. Steady-state analysis was performed to demonstrate the digital controller operation. Finally, a two-phase 12- to 1-V, 40-A, 250-kHz synchronous buck converter with the proposed digital controller was designed to verify the theoretical analysis by simulation and experimental results.

A New Resonant Gate Driver with Two Half Bridge Structures for Both Top Switch and Bottom Switch

To reduce gate driving losses caused by high switching frequency operation, a new resonant gate driver for driving both top switch and bottom switch is presented in this paper. This new gate drive circuit has a simple two-half-bridge structure. A coupled inductor is used for energy circulation between gates of switches and also works as a voltage-boost transformer. It is more interesting that it also can be extended to drive two MOSFETs with common ground. Theoretical and simulation results prove operation and driving loss saving efficiency of the proposed resonant gate drive circuit.

A Single-Switch Valley-Fill Power-Factor-Corrected Electronic Ballast for Compact Fluorescent Lightings With Improved Lamp Current Crest Factor

Although compact fluorescent lamps (CFLs) have been on the market for a long time, many of them do not achieve the same power factor as the incandescent lamps do, which presents a significant problem for the utility with the current widespread use of CFLs for household lightings. A simple single-switch electronic ballast with passive valley-fill power factor correction is proposed in this paper for CFL application. The proposed single-switch ballast circuit is able to achieve zero current switching to maximize the circuit efficiency. A simple feedback circuit with duty ratio control is also proposed to improve the high lamp current crest factor caused by the valley-fill circuit. Detailed descriptions and analysis of the circuit operating principles are provided in this paper. Simulation and experimental results are given on a 13-W CFL tube from Osram Sylvania to highlight the merits of the proposed work.

Secondary-side adaptive digital controlled series resonant DC-DC converters for low voltage high current applications

It is more difficult for VRMs to supply power to future microprocessors, which need lower supply voltage, large current and large current slew rate. Most of todays VRMs are with inductor-capacitor type output filters. The inductor in the output filter limits the current transient speed. Hence, the secondary-side controlled series resonant converter with capacitor type filter is introduced in this paper to overcome this limitation. The lack of the inductor in its output filter makes it have very quick dynamic response. Also an adaptive control scheme is proposed to control the current-type synchronous MOSFETs, which eliminates the current sensor in the power path. Theoretical analysis and simulation results verify the proposed concept.

A Precisely-Regulated Multiple Output Forward Converter With Automatic Master-Slave Control

An automatic master-slave control scheme for a multiple outputs forward converter is presented in this paper. With this method, the duty cycle is minimized and the efficiency is improved for all load conditions while achieving independent and precise regulations on all outputs. Description of operation and steady state analysis are performed to understand the multiple outputs converter with the automatic master-slave control. Simulation results verify the concept

A Hybrid Phase-Shift Modulation Technique for DC/DC Converters With a Wide Range of Operating Conditions

This paper presents a new hybrid phase-shift modulation technique which is able to provide soft switching for the entire operating conditions of dc/dc converters. The proposed phase-shift modulation technique does not require any extra active/passive circuitry to guarantee soft-switching. In addition, the proposed technique can be applied to the general category of power circuit topologies for dc/dc converters, which use a full-bridge inverter in their power circuit. The proposed hybrid phase-shift modulation technique includes two distinct modulation strategies based on the operating condition of the converter. Thus, it has a variable structure that can optimize the performance for various operating conditions. The main advantages of the proposed technique are the achievement of soft-switching independent of the load condition, and optimized performance. Theoretical analysis and simulation/experimental results demonstrate the superior performance of the proposed hybrid phase-shift modulation technique over the conventional one.

Analysis of a high performance voltage regulator with non-linear multi-mode control: Bandwidth and large transient response

A novel digital adaptive voltage positioning (digital AVP) technique with dual-voltage-loop was proposed in [21]. Good transient performance had been achieved without using complicated control. In this paper, a small signal model is proposed for this mixed-signal digital controller. It is revealed by this small signal model that the inner current loop is in analog and the voltage loop is in digital, thus the controller can benefit from both: having valuable features of digital control but without limitations such as limit cycle. On the other hand, dynamic behavior of the voltage regulator with this digital AVP controller under large load transient is analyzed. Decoupling between bandwidth and large transient response with this novel digital AVP controller is verified.

A ZVS phase-shift full-bridge DC/DC converter with optimized reactive current used for electric vehicles

This paper presents a Zero Voltage Switching (ZVS) phase-shift DC/DC converter, which is able to optimize the amount of reactive current required to guarantee ZVS for the power MOSFETs. The intended application for the proposed DC/DC converter is automotive, in particular a battery charger for an electric vehicle. Since a very wide range of load/line variations is expected in this application, the converter should be able to sustain ZVS under different conditions in order to demonstrate a reliable and efficient performance. The converter utilizes coupled inductors to provide the reactive current for soft-switching. The coupled inductor in conjunction with the specific control system is able to generate the optimal amount of reactive current produced by the auxiliary circuit. This leads to minimized conduction losses in the power MOSFETs, as well as the losses in the coupled inductors. In the proposed approach, the peak value of the reactive current is controlled by the phase-shift between the leading leg and lagging leg of the full-bridge converter to optimize the load impact. In addition, the peak current value is controlled by the switching frequency in order to compensate for the input voltage variations. Experimental results for a 2kW prototype are presented. The results show a significant improvement in efficiency and enhanced performance of the converter particularly for heavy loads.