Heater-in-converter (HIC): bringing heating capability to power converters without density penalties
The Heater-in-Converter (HiC) technology allows to bring heating capability into existing power converters.
The Heater-in-Converter (HiC) allows to control the power dissipation of electronic converters orthogonally from their functionality. It can be applied to almost all power converter topologies. Indeed, the heat is generated in a controlled fashion by the converter and it is distributed to the systems components that need a specific temperature. The heat distribution is actuated through the cooling system, preferably a liquid-based one.
This technology can be profitably applied to both hybrid and electric vehicles and boats. Moreover, no power components need to be added to the existing circuitry. This technology can operate in any load condition and converter working point. Even in the absence of the load, it can be used for the cold start of thermal-sensitive parts, such as batteries. Various techniques exist to achieve thermal control of electric and electronic components, but none of them can be used in no-load condition. The HiC technology overcomes this limit using the controlled shoot-through principle. HiC benefits are the unaltered output waveform, null output distortion, complete control in no-load condition. The technology is also cost effective since it requires only a minor modification of the gate driver circuits. The change in the control algorithm demands around 80 hours of converter design time, that can be easily amortized in production. The power stage of the converter, which is the most expensive part, is untouched by the technology implementation. With HiC no added mass nor volume is required, since the technology is completely embedded into the existing power converter. This one is already included in the vehicle, so no penalty is introduced by the technology. Another important advantage is the reduction of e-waste: using HiC and removing the heater reduce the mass of hazardous materials that need to be disposed of at the end of life of the vehicle.
Stage of development
Researchers have experimentally verified the technology by building a prototype out of a traditional power stage (half-bridge DC/AC converter). This prototype presents an innovative gate driver circuit to the converter and implemented a novel modulation. This allows to control the amount of heat generated by the converter. So far researchers studied and modeled the technology from the functional point of view, achieving a good match with their experimental results. However, three potential issues still need to be explored for the industrialization of the technology. The first issue to be studied is the reliability of the power components driven by the presented technology. Secondly, there is the need to test the technology with all the families of power devices available on the market. Ultimately, a test should address the cooling system used to transport heat from the converter to the relevant parts that need to be heated.
Challenge and needs
The potential applications of the proposed technology are in the transport and energy sectors. HiC technology addresses the challenge of proper thermal management of complex systems where at least one power converter is present. HiC can be profitably used wherever fast heating is needed, regardless of the system operating conditions. Some example of applications are: cold start of batteries, warm-up of fluid in hydraulic machinery, thermal excursion reduction in discontinuous service machines and thermostatting of temperature-sensitive appliances.
The hybrid and electric vehicles and boats can get important advantages from HiC, since it preserves both power density and specific power of the system, while guaranteeing a ready-to-use heating source. It can be used to warm up batteries, regardless of the condition of the internal combustion engine, if present. Coupled with an air-cooling system, the HiC can be used to heat cabins/cockpits, seats and for windshield defrosting in cold weather. Other applications involve the use of HiC to reduce the power cycling of components, thus improving reliability of systems that are reliability-critical rather than efficiency-critical. HiC at low heat generation rates can also be employed to characterize the power devices directly into the final circuit assembly, assuming the role of enabling technology for various sensing, diagnostic and prognostic applications.
- Italian Patent NR. IT201700122136 “Metodo di pilotaggio di un mezzo ponte attivo comprendente almeno due transistori, circuito di pilotaggio di ciascun transistore del mezzo ponte e relativo schema di modulazione periodico di segnali di comando”
Potential markets and targets
The HiC technology addresses hybrid and electric vehicles, electrified motorboats, off-road vehicles, more electric aircrafts and operating machines markets. Nevertheless, the technology has a general scope and can be applied also to other markets, provided that a converter with a power stage is already part of the system.
This market is deeply oriented on large production numbers and the major players are huge multinational companies. Those are sided by niche manufacturers that provide very custom and specialized products, mainly for high-end, exclusive vehicles and boats. A simple yet effective technology such as HiC can achieve an important market penetration thanks to the simplification that it can bring to the system design. It adds functionality to a part, the power converter, that is almost ubiquitous in nowadays means of transport.
The key competitors for the technology are the electric heater manufacturers, companies that develop heat exchangers, heat pumps and cogeneration systems.
With respect to the products of electric heater manufacturers, the application of this technology makes it possible to remove the cost and volume of the heater component. Comparing HiC with heat exchangers (such as, for example, those of Denso, Mahle, Valeo, …), volume and weight are saved as well. The heat produced by HiC is obtained at a temperature that can be directly used, without any further conversion in between. Moreover, heat exchangers can be used only in hybrid vehicles, where the internal combustion engine constitutes the primary heat source. HiC can fit both hybrid and electric vehicles and boats, since both require electrical power conversion on-board. A comparison of HiC with the products of the major automotive heat pump manufacturers like Denso or Rheinmetall, shows an increased simplification and number of parts for the presented technology, suggesting an improvement in the lifetime of the heating system and reduced maintenance costs for the end user.
Potential partners to co-develop this technology are:
• System integrators with expertise in powertrains and in internal combustion engines, driveline and heat management.
• Developers of smart battery packs interested in providing an accumulator with conversion capabilities and self-thermal management. Expertise in battery packs, their assembly and battery management systems is necessary.
• Developers of operating machines, to electrify minor loads while making more robust the performance of the hydraulic actuators; expertise in fluid machines and their interaction with other systems.
• Manufacturers of power converters, to evaluate new functionalities enabled by the technology and to industrialize the proposed gate driver unit.