Jai P. Agrawal

Determination of cross regulation in multioutput resonant converters

The determination of the cross-regulation characteristics in multioutput resonant converters is examined. The steady-state cross-regulation characteristics are derived using the state-plane techniques, illustrated by the example of a two-output clamped series resonant converter with clamped capacitor voltage. This technique can be applied to any multioutput resonant converter, thus it can serve as an important design tool and a criterion for selecting the optimal topology. The intuition gained from the analysis can be used to reduce the cross regulation in the multioutput power supplies. The theoretical results are verified by simulations and experimental measurements.<<ETX>>

Improving the dynamic and static cross regulation in multi-output resonant converters

The cross regulation error in multi-output resonant converters consists of dynamic and static components. The static component is caused by the leakage inductances in the multi-winding output transformer, whereas the dynamic component depends on the filter components. The dynamic cross regulation is investigated using a two-output parallel resonant converter. It is shown that the dynamic cross regulation error can be reduced by careful design of output filters. The design procedure is given for optimizing both dynamic and static cross regulation. The concepts are verified by computer simulation.<<ETX>>

RF Energy Harvesting

This paper presents the results of a project in RF Energy Harvesting for scavenging energy from the ubiquitous radio-frequency (RF) electromagnetic waves. Such a device can be very useful to charge mobile phone in jungles and in remote areas or where the electric utility is not available or not reliable. In comparison to other methods of energy harvesting, RF has the smallest energy density and therefore poses big challenges. Based on the experiments, we find that the most efficient range of operation lies in the medium wave frequency band: 531-1,611 kHz. The experiment uses an antenna, LC tuning circuit, 5-stage of Villard voltage multiplier circuit and super-capacitor as energy storage. The experiment could harvest a RF signal from 1-mile distant transmitter that generates a field-strength of 103.724 dBu at the location of the receiver. The maximum charge on storage capacitor achieved was recorded 2.8V. A limitation of using this band of frequency is the large size of antenna that limits its portability.

A 100 watt power supply using ZVS boost converter

This paper presents the analysis, design and experimental data of a power supply based on the boost power converter topology using the zero-voltage switching technique. The topology uses two switches. Zero-voltage turn-on is accomplished on both switches with the capacitor across only one switch. The converter operates at 100 kHz. This power converter has a wide range of zero-voltage switching capability. Theoretical performance is determined by using the state-plane analysis.<<ETX>>

Software controller for PWM converters

A software controller is realized for DC-DC switching power converters. The software is capable of implementing several real-time control schemes such as the continuous/discrete switching frequency control, continuous/discrete pulse-width control and phase control of PWM converters. Implementation in software provides the capability of executing complex control schemes and supervisory functions which are easy to implement, update and adapt to different applications without much overhead.<<ETX>>

Effects of output filter on cross regulation in SRC

Cross regulation performance of multioutput series resonant converter (SRC) topologies using capacitive or inductive filters is analyzed. The steady state cross regulation characteristics are derived using the state-plane techniques and are illustrated by the examples of two-output SRCs with capacitive and inductive filters. The characteristic curves show that over some range of output currents, the cross regulation performance of an SRC with an inductive filter is much improved over the SRC with capacitance filter and less dependent on the tolerances in leakage inductances and the loading on unregulated outputs. It is shown that the converter control characteristics of an SRC with an inductive filter are relatively unaffected by the addition of the second output. The theoretical results are verified by simulation. >

Modeling and simulation of low duty ratio buck synchronous converter under large load current switching

This paper presents the spice simulation of low duty ratio synchronous Buck converter under large load switching conditions. The voltage regulator module (VRM) in this category uses multiphase synchronous Buck converter for supplying large load currents. The low duty ratio Buck converter causes larger peak-peak ripple, therefore, the two-loop control scheme is used for achieving desired voltage and current performance. The input and output voltages in the VRM simulation are respectively 8.5 V and 1V respectively. The simulation circuit uses a single phase equivalent circuit for simulation with double capacitors in the input and output circuits to account for actual values used per phase. The simulation circuit uses a parasitic inductor at the input side to account for the copper trace and the module connector pin. The output circuit uses an inductor L2 of 0.38 uH to reduce The dc average equivalent circuit of a single phase converter (also known as the dc transformer) is shown in Fig. 2.D is the duty ratio. IO is the load current. Figure 3 shows the two phases of the Buck converter with all parasitic components. the output current ripple. The load current swing is considered 12 A which is equivalent to 24 Amp switching in the actual 2-phase module. The simulation shows that by selecting low ESR capacitors a 0.06% output voltage transient can be achieved for 13-25 Amp load switching.

A high efficiency and high power factor electronic ballast using ZVS-PLR inverter

This paper presents the analysis, design and implementation of a high frequency (maximum 75 kHz) resonant inverter with power factor correction for driving fluorescent lamps. The inverter is based on parallel resonant half-bridge topology. The inverter employs a boost-derived power factor correction scheme. The switches turn-on at zero voltage. Experimental results from a laboratory prototype are presented and compared with the performance of conventional 60 Hz and high frequency commercial units.