Introduction
The demand for low-cost, portable welders is on the rise, especially in developing regions where affordability and mobility are key. These devices often use discrete IGBTs and MOSFETs for manual metal arc (MMA) and tungsten inert gas (TIG) welding, operating within a power range of 1.5 kW to 6 kW. Traditional designs rely on current mode PWM control with topologies such as double-tube forward (TTF), half-bridge (HB), and full-bridge (FB). Most of these systems operate with hard switching, which can lead to higher losses and larger components. However, increasing the switching frequency has become a major trend to improve efficiency and reduce costs. Infineon’s TRENCHSTOP 5 IGBT technology offers significant improvements in turn-off losses, making it an ideal choice for next-generation welders.
Compared to earlier generations, TRENCHSTOP 5 IGBTs offer better performance and support higher switching frequencies—up to 100kHz. This allows for smaller magnetic components and fewer capacitors, improving overall system efficiency. However, replacing older IGBTs isn’t always straightforward. Higher di/dt and dv/dt can cause voltage overshoots during turn-off or oscillations during turn-on, leading to potential EMI issues. Proper layout and design adjustments are essential to fully leverage the benefits of this technology.
Improving the Half-Bridge Topology
Reducing turn-off losses opens up new possibilities for primary side converter designs, simplifying the system and enabling more compact PCB layouts and gate driver configurations. As a result, the overall size and weight of the welder can be significantly reduced. For example, a single-phase 4.5kW half-bridge MMA/TIG welder was redesigned using TRENCHSTOP 5 IGBTs. By optimizing the power supply loop and layout, two 40A/600V IGBTs were replaced with a single IKW50N65H5 TRENCHSTOP 5 IGBT per switch.
Additionally, the lower switching and conduction losses lead to reduced device temperatures. In some cases, even insulating foils can be used instead of traditional cooling methods. A comparison of case temperatures between different Infineon IGBT technologies shows that TRENCHSTOP 5 operates 40K cooler than its predecessor, enhancing reliability and thermal management.
To ensure safe operation, tests were conducted to determine the optimal gate resistance RG(off) that keeps voltage overshoot below 80% of the breakdown voltage. Lower stray inductance allows for a smaller RG(off), reducing overshoot risks. The test also monitored collector-emitter voltage oscillations, ensuring they remain within acceptable limits—below -200ns, with a maximum of -25V.
Even in unoptimized layouts, TRENCHSTOP 5 can still perform well if the passive gate network is properly adjusted. Introducing a turn-off gate resistor and a CGE/RCE clamp structure helps maintain voltage levels within safe ranges. However, this may limit the full potential of the IGBT, highlighting the importance of proper PCB design and layout optimization.
To further reduce stray inductance, TRENCHSTOP 5 IGBTs can be mounted on insulated substrates using surface mount technology. This approach enables a more compact design, allowing both high-side and low-side IGBTs to share a common heat sink. While advanced insulation materials like IMS or Al₂O₃ ceramics are still required, the overall system becomes much smaller and lighter.
This design concept achieves a stray inductance of around 40nH, which can be reduced to 20nH by combining different package types and adopting a full-bridge topology. Lower inductance allows for higher switching frequencies, improving power density while reducing the number of DC bus capacitors and transformer size. This makes the system more efficient and cost-effective.
Improving the Full-Bridge Topology
Figure 4 presents another example—a 3.5kW full-bridge high-frequency welder designed to replace traditional MOSFETs with TRENCHSTOP 5 IGBTs. This design offers lower costs, better manufacturability, and higher reliability. The low turn-off losses of TRENCHSTOP 5 allow one IGBT to replace three conventional high-voltage MOSFETs, simplifying the circuit and reducing component count.
By integrating the power and drive stages onto a single board, the overall board area is reduced by one-third compared to traditional setups. Additionally, minimized parasitic inductance enables faster switching with controlled voltage overshoots. This results in a more compact, reliable, and cost-effective solution.
This demonstration model was developed to simplify the system and increase power density. It reduces assembly workload, improves manufacturability, and supports mass production. Compared to commercial solutions, the new design cuts material costs by about 30%, reduces size by 30%, and lowers weight by 35%. These improvements make TRENCHSTOP 5 a compelling choice for next-generation portable welders.
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