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EP-4738992-A1 - MODULAR AND CONFIGURABLE RESONANT INVERTER SYSTEM WITH DYNAMIC TRANSFORMER RATIO SWITCHING AND AUTOMATIC LOAD MATCHING FOR MULTI-OUTPUT INDUCTION HEATING AND WIRELESS POWER TRANSFER APPLICATIONS

EP4738992A1EP 4738992 A1EP4738992 A1EP 4738992A1EP-4738992-A1

Abstract

A modular resonant inverter system for induction heating or wireless power transfer, including a plurality of power inverter modules each configured to convert an input voltage into a resonant high-frequency output; a plurality of matching transformers, each transformer connected to the output of a respective module, the transformers including switchable primary and secondary windings; a distributed tank capacitor bank associated with each module, wherein the capacitors are configurable in series, parallel, or series-parallel configurations based on the connection of the modules; an electronic switching circuit coupled to the primary windings of each transformer, wherein the switching circuit adjusts the number of primary turns to modify the transformer ratio and achieve load impedance matching; and a control system configured to monitor and control the switching circuit and the tank capacitor configuration to dynamically match the impedance of the load, wherein the control system reconfigures the transformer winding ratios and capacitance values in the distributed tank capacitor bank in response to varying load conditions.

Inventors

  • METODIEV, MARIO
  • Bonev, Stanimir

Assignees

  • Ultraflex International, Inc.

Dates

Publication Date
20260506
Application Date
20251031

Claims (10)

  1. A modular resonant inverter system for induction heating or wireless power transfer, comprising: a plurality of power inverter modules each configured to convert an input voltage into a resonant high-frequency output; a plurality of matching transformers, each transformer connected to the output of a respective power inverter module, the transformers comprising switchable primary and secondary windings; a distributed tank capacitor bank associated with each power inverter module, wherein the capacitors are configurable in series, parallel, or series-parallel configurations based on the connection of the power inverter modules; an electronic switching circuit coupled to the primary windings of each transformer, wherein the switching circuit adjusts the number of primary turns to modify the transformer ratio to match load impedance; and a control system configured to monitor and control the switching circuit and the tank capacitor configuration to dynamically match the impedance of the load, wherein the control system reconfigures the transformer winding ratios and capacitance values in the distributed tank capacitor bank in response to varying load conditions.
  2. The system of Claim 1, wherein the electronic switching circuit for adjusting the transformer winding ratios comprises a single transistor and a series capacitor for each winding, thereby reducing the number of switching components required for each transformer.
  3. The system of Claim 1, further comprising at least one redundant power inverter module that is automatically enabled by the control system when one or more modules fail, wherein the at least one redundant module is connected in parallel with the failed module's matching transformer.
  4. The system of Claim 1, wherein the control system uses feedback from voltage, current, and phase detectors to adjust the transformer ratios and tank capacitor configurations, providing real-time impedance matching and maintaining resonance under dynamically changing load conditions.
  5. A method for automatic load matching in a modular resonant inverter system, comprising: providing a plurality of power amplification modules each having an associated matching transformer with switchable primary and secondary windings; connecting the outputs of the power amplification modules to a distributed tank capacitor bank that is configurable in series, parallel, or series-parallel configurations; measuring the voltage, current, and phase of the load and determining the load impedance; dynamically adjusting the primary winding turns of the matching transformers using an electronic switching circuit to modify the transformer ratio based on the measured load impedance; reconfiguring the connections of the tank capacitor banks to adjust the resonant frequency of the output circuits; and automatically matching the impedance of the system to the impedance of the load based on the measured voltage, current and phase of the load and load impedance.
  6. The method of Claim 5, wherein the control system dynamically adjusts the configuration of the tank capacitor banks to alter the resonant frequency of the output, ensuring optimal power transfer efficiency at different operating frequencies.
  7. The method of Claim 5, wherein the reconfiguration of the power inverter modules and capacitor banks is achieved through a combination of electronic switching circuits and relays, allowing for high-speed reconfiguration without the need for mechanical contactors or pneumatic switches.
  8. A modular resonant inverter system comprising: a plurality of modules, each connected to a matching transformer and a distributed tank capacitor bank; a set of electronic switches configured to interconnect the primary and secondary windings of the matching transformers in series, parallel, or series-parallel configurations; a control system that monitors the operating parameters of each module and automatically reconfigures the connections of the modules and capacitor banks based on load conditions; wherein the control system further comprises a failure detector that isolates a failed module by shorting the primary winding of the associated matching transformer, allowing the remaining modules to continue operating without interruption.
  9. The system of Claim 8, wherein the modules are configured to be powered by either AC or DC sources, with the system capable of operating with a 1-phase or 3-phase AC power source, or a DC input power source.
  10. The system of Claim 8, further comprising a user interface that displays real-time operating parameters of each module and allows manual override of the automatic load matching and configuration settings.

Description

TECHNICAL FIELD The present invention relates to the technical field of electromagnetic energy transfer, with a particular focus on induction heating and melting systems. It also pertains to load-matching and tuning of compensation networks in wireless power transmission systems, such as those used for battery charging or energy transfer applications. BACKGROUND Induction heating power supplies typically employ resonant inverter circuits to generate high-frequency electromagnetic fields. Their performance and efficiency largely depend on the ability to match the output circuit to the load conditions, which can vary significantly during operation. Such challenges include the change in electrical impedance as materials heat up, undergo phase transitions, or alter their physical properties. For example, during the heating of ferromagnetic materials, a change in impedance occurs when the material passes through its Curie point temperature, causing a significant shift in the load conditions. Existing methods for load matching in resonant inverters rely primarily on switching the primary or secondary turns of a matching transformer or configuring capacitors in the tank circuit to achieve resonance at different frequencies. Traditionally, such adjustments are performed manually, by using electromechanical contactors or relays, or through bulky and slow pneumatic switches. These methods are not suitable for applications requiring rapid or dynamic changes to the load configuration, resulting in reduced efficiency, increased energy consumption, and potential system instability and failures. Automatic load matching solutions have been explored but often involve complex control circuits and multiple switching devices, leading to increased system complexity, higher cost, and potential reliability concerns. Furthermore, existing solutions lack the modularity and scalability of the presented system, making them challenging to adapt for multi-load applications or to expand power levels by adding additional inverter modules. In the field of induction heating and power conversion, resonant inverters are commonly used to generate high-frequency electromagnetic fields for efficient energy transfer. The effectiveness of these systems is highly dependent on the ability to match the impedance of the output circuit with the impedance of the load. Various methods have been developed to achieve load matching, with each having its limitations and drawbacks. One common approach to load matching is by switching the number of primary or secondary turns in the matching transformer, thereby altering the voltage and current ratios at the transformer's output. This method is traditionally achieved using electromechanical switches, relays, or contactors, which can be manually adjusted or automatically controlled. Although effective, these methods are typically slow, prone to mechanical wear, and require substantial space for installation, making them unsuitable for applications that require quick reconfiguration or systems with limited physical space. Another prevalent technique involves varying the capacitance of the tank circuit in the resonant inverter. This is often accomplished by configuring capacitor banks in series, parallel, or series-parallel combinations to change the overall resonant frequency of the circuit. While this method provides some flexibility in tuning the circuit to different load conditions, it is generally implemented using bulky capacitors, such as oil-filled film capacitors, which add cost and size constraints to the system. There have been efforts to incorporate electronic switches, such as MOSFETs or IGBTs, to achieve faster switching and more precise control of load-matching components. However, such implementations often require multiple switches per transformer winding, resulting in increased circuit complexity, higher power losses, and the need for sophisticated control algorithms. Furthermore, these solutions are not inherently modular, making it difficult to scale the system or reconfigure the output circuits without significant redesign. Moreover, existing induction heating systems typically lack flexibility in handling multiple independent load circuits simultaneously. Configurations are typically limited to a single output or require complex hardware changes to accommodate additional loads, which can be time-consuming and costly. The lack of dynamic reconfigurability restricts the application of these systems in scenarios where loads change rapidly, such as in the heating of materials that undergo phase changes or in wireless power transmission systems with varying positioning or number of receiving devices. Therefore, there is a need for a more versatile, modular, and dynamic approach to load matching and power conversion in induction heating and similar systems. The related art does not provide a solution that can flexibly and seamlessly adjust the system's output parameters to varying load conditions