A new electrical energy converter design developed by Kobe University provides significantly increased efficiency at lower cost and less maintenance. This accelerated DC voltage converter is expected to significantly impact the development of electrical and electronic components in various industries, including power generation, healthcare, mobility and information technology.

Devices that harvest energy from sunlight or vibrations, or medical devices or hydrogen-powered cars, have a common basic component. This so-called “boost converter” converts a low-voltage DC input into a high-voltage DC output. Since it is a ubiquitous and essential component, it is desirable that it use as few parts as possible to reduce maintenance and costs, while also operating at the highest possible efficiency without generating electromagnetic noise or heat. The basic principle of boost converters is to quickly switch between two states in a circuit, one storing energy and the other releasing it. The faster the switching, the smaller the components can be, thus reducing the size of the entire device. However, it also increases electromagnetic noise and heat generation, reducing the performance of the power converter.

Kobe University power electronics researcher Mishima Tomokazu’s team has made significant progress in developing a new DC power conversion circuit. They managed to combine high-frequency switching (about 10 times higher than before) with a technique called “soft switching”, which reduces electromagnetic noise and power losses due to heat dissipation, while at the same time reducing the number of components and therefore keeping the cost low. complexity.

“When a circuit transitions between two states, there is a brief period during which the switch is not fully closed, and at that moment there is both voltage and current across the switch. This means that during this time the switch acts like a resistor and therefore dissipates heat. The more frequently the state of the switch changes, the more this dispersion occurs. “Soft switching is a technique that allows switching to occur at zero voltage, thus minimizing heat loss,” explains Dr. Mishima. Traditionally this has been achieved with “dampers”, which are components that provide alternative energy absorbers during the transient state, resulting in subsequent energy losses.

Release and development of a prototype

Kobe University team presented their new circuit designs and evaluations in the magazine IEEE Transactions on Power Electronics. The key to achieving these is the use of “resonant tank” circuits, which can store energy for the duration of the switching period and therefore have much lower losses. In addition, they use a component-saving design with flat components printed on a printed circuit board, called “planar transformer”, which is very compact and has both good efficiency and thermal performance.

Mishima and his colleagues also created a prototype of the circuit and measured its performance. “We have verified that our damping-free design significantly reduces electromagnetic noise and delivers high power efficiency of up to 91.3 percent; This is an unprecedented rate for a MHz drive with high voltage conversion. “This rate is also more than 1.5 times higher than current designs.” However, they want to further increase efficiency by reducing the power dissipation of the magnetic components used.

Considering how common electrical devices are in our society, it is extremely important for high-efficiency, low-noise operation of high-voltage multiplier DC power supplies. This development at Kobe University will have important applications in electric power, renewable energy, transportation, information and telecommunications, and healthcare. Mishima explains his future plans: “The current development is a low-power prototype in the 100W class, but we aim to increase the power to a higher power in the kW class in the future by improving the electronic board and other components.”