A. Ferreres

Improving the Efficiency of IGBT Series-Resonant Inverters Using Pulse Density Modulation

This paper analyzes a high-power (50 kW) high-frequency (150 kHz) voltage-fed inverter with a series-resonant load circuit for industrial induction heating applications, which is characterized by a full bridge inverter made of insulated-gate bipolar transistor and a power control based on pulse density modulation (PDM). This power control strategy allows the inverter to work close to the resonance frequency for all output-power levels. In this situation, zero-voltage switching and zero-current switching conditions are performed, and the switching losses are minimized. An additional improvement of inverter efficiency is achieved by choosing appropriate values of the modulation index. Results are verified experimentally using a prototype for induction hardening applications. A comparative study between the PDM and the classical power control by frequency variation will be made.

Improving the Reliability of Series Resonant Inverters for Induction Heating Applications

This paper analyzes a high-power (100-kW) high-frequency (50-kHz) voltage-fed inverter with a series resonant load circuit for industrial induction heating applications which is characterized by a full-bridge inverter composed of isolated-gate bipolar transistors and a new power control based on phase-shift (PS) control. This power control circuit incorporates a load-adaptive variable-frequency controller and automated blanking time management in order to allow the inverter to work in zero-voltage switching for all output power levels and load conditions. An important improvement of the inverter reliability is achieved by choosing an appropriate and novel switching sequence for the PS inverter. The results are verified experimentally using a prototype for induction hardening applications. A comparative study between the proposed and standard PS power control will be made.

Soft switching bidirectional converter for battery discharging-charging

This paper presents the results of a project that looked after a high efficiency bidirectional converter which could be used as a battery discharge/charge regulator when the bus voltage is above the battery voltage. High efficiency, high stability and simplicity are the main goals, no galvanic isolation is required. Taking into account all these parameters, our proposed solution has been a new topology based on a boost converter with coupled inductors. The use of a bidirectional converter reduces the mass of the overall charge/discharge subsystem and lowers cost and component count. In the project, its use is intended for space applications, but telecom, automotive or similar applications can also benefit of this new concept.

Comparative Study of a Single Inverter Bridge for Dual-Frequency Induction Heating Using Si and SiC MOSFETs

The induction surface hardening of parts with nonuniform cylindrical shape requires a multifrequency process in order to obtain a uniform surface hardened depth. This paper presents an induction heating high power supply composed by a single inverter circuit and a specially designed output resonant circuit. The whole circuit supplies simultaneously both medium- and high-frequency power signals to the heating inductor. An initial study is made to select the most appropriated topology for this application. The resonant output circuit is analyzed, and a design procedure is presented. The selected inverter operation is described and simulated. Simulations are experimentally verified on a 10-kW dual-frequency resonant inverter operating at 10 and 100 kHz using MOSFETs of silicon (Si) and silicon carbide (SiC) technology. A comparative study is presented based on the measurements of power losses and the energy efficiency of the inverter using both types of MOSFETs.

Small-signal modeling of a controlled transformer parallel regulator as a multiple output converter high efficient post-regulator

This paper presents a post-regulator based on the use of a controlled transformer, which adds or subtracts an additional voltage to the output filter of a converter in order to regulate its output voltage. So, their actuation is complementary to that of more known post-regulators, such as the magnetic amplifier (magamp) and synchronous switch post-regulator (SSPR), because the regulation is achieved by controlling the voltage across the filter inductor instead of its charge time. Besides, the post-regulator processes the power in parallel to the one flowing from input to output and only handles a percentage of it. The post-regulation by controlled transformer is suitable of being employed in any isolated PWM power converter and combines a good efficiency and the easiness of design of classical switched power supplies. The work describes the post-regulation strategy for obtaining two outputs independently regulated, and presents a model to obtain the control transfer function and the cross-impedance expressions.

Application of a novel parallel regulation technique in a two output forward converter

Techniques based in parallel post-regulation eliminate cross-regulation between the different outputs of multi-output converters and achieve good efficiency by handling only a percentage of the power delivered to the output. This work describes a simple implementation of such a regulation mechanism in a two output forward converter. Moreover, the development of a complete steady state and low signal model ensures proper design and implementation. The model shows the inherent simplicity of the regulation procedure, similar to that of classical PWM regulators.

Bidirectional High-Efficiency Nonisolated Step-Up Battery Regulator

The design and results of a high-efficiency high-power (5 kW) nonisolated bidirectional dc-dc converter is presented. High stability due to minimum phase behavior is an additional benefit of the topology. The converter is a new boost with output filter where input and output inductors are coupled. This converter is useful with any system that needs to charge and discharge backup batteries and can be applied in space, automotive, and telecom power systems.

Bidirectional Coupled Inductors Step-up Converter for Battery Discharging-Charging

The present paper shows the preliminary results of a project that looks for a high power, high efficiency bidirectional step-up converter which could be used as a battery discharge/charge regulator. High efficiency and low mass are the main goals, no galvanic isolation is required and MTBF should be as large as possible. Taking into account all these parameters our proposed solution has been a new topology based on a boost converter with output filter and that couples input and output inductor. The use of a bidirectional converter reduces the mass of the overall charge/discharge subsystem and lowers cost and component count. Stability has been studied theoretically and verified experimentally

High power passive soft switched interleaved boost converters

The present project was developed in order to find a high power (/spl ges/5 kW), high efficiency step-up converter which could be used as a battery discharge regulator. Efficiency should be higher than 97%, mass should be lower than 2.5 kg, no galvanic isolation was required and MTBF should be as large as possible. Taking into account all these parameters our proposed solution has been two interleaved boost converters with passive soft switching.

High-Power Battery Discharge Regulator for Space Applications

This paper presents a new solution for a battery discharge regulator for high-power space applications (power-per-module ≥ 5 kW) using a high-efficiency step-up converter. Basic requirements are efficiency that is higher than 97%, mass that is lower than 2.5 kg, no galvanic isolation necessary, and a high mean time between failures. By taking into account all these parameters, the selected topology has been two interleaved boost converters with passive soft switching. Small-signal analysis of these two interleaved boost converters is also presented.