Rechargeable battery and charging technology - Power Circuit - Circuit Diagram

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Advances in fast charging and contactless charging technologies can dramatically change product designs, including industrial equipment and electric vehicles, and create new markets (Figure 1). Lithium-ion rechargeable batteries that can be quickly recharged are propelled in areas such as electric vehicles, or will promote the introduction of non-contact charging.



Figure 1: The combination of fast charging and non-contact charging will expand the market

The market for power tools with fast-charging batteries is growing rapidly. It is troublesome to use electric wires for industrial equipment and electric vehicles, and the combination with non-contact charging is the key to expanding the market.

Specifically, industrial equipment such as unmanned aerial vehicles and industrial robots, and electric vehicles operating on fixed lines such as new-generation trams, buses, and commercial vehicles will promote the application of non-contact charging. This is determined by the improvement in charging safety and the convenience of convenience.

Resonance method is highly anticipated

At present, the development of high-power non-contact charging technology that can charge electric vehicles and the like is more prosperous than ever. Among them, the non-contact charging technology of the resonance mode has attracted great attention. At the Massachusetts Institute of Technology (MIT) in June 2007, Intel in the United States published a technique using magnetic field coupled resonance in August 2008, which became a hot topic and is still fresh in memory. Although the transmission efficiency is only about 40%, the use of this technology is expected to charge the car in motion, and its related research and development is becoming more and more active.

The non-contact charging of the new resonance mode has also appeared. This is the technique of using electric field coupled resonance in the development of the Zhuzhong Public Works (Figure 2). Although this technology needs to make the power transmitting end and the power receiving end close to each other, it can also supply power in a state where the horizontal direction is misaligned, and the advantage is that it does not occur as in the electromagnetic induction type non-contact charging technology which has been applied now, when foreign matter invades. At the time, there are problems such as overheating and leakage of electromagnetic waves and high-frequency waves.


Figure 2: Powered by electric field coupling

The Zhuzhong Works Office is developing a power supply system (a) that utilizes the principle of electric field coupling. The power supply system using series resonance successfully supplied 100W of power to the incandescent bulb with 90% efficiency.

Moreover, unlike the electromagnetic induction method, the resonance method does not use ferrite and Leeds coils, so the weight and cost of the device can be reduced. In addition, it is only a matter of expanding the contact area to power a high-power appliance.

Kazuo Hara, a researcher at the Materials Engineering Department of the Institute of Advanced Technology at the Bamboo Institute of Technology, said that “the future is expected to embed non-contact charging in the walls and floors of factories, offices and apartments”. The current envisaged use is combined with a DC power supply system to provide power for industrial robots, construction machinery, medical equipment, and home appliances. Moreover, it will strive to realize an electric vehicle charging system that is quickly charged by the floor extending the boom and contacting the vehicle body during parking.

The power supply system using electric field coupled resonance developed by Takenaka Works is divided into two modes: series resonance and parallel resonance. Both have their own strengths: the structure of the series resonance mode is relatively simple, and the parallel resonance mode can efficiently transmit power even if the applied voltage is lowered. Both of them have a transmission efficiency target value of 95%.

Regarding the series resonance, a test for transmitting 100 W of electric power to an incandescent bulb has been carried out (Fig. 2(b)). The current transmission efficiency is 90%. The frequency is about 600 kHz, and the insulating film of the contact portion is 300 μm. In order to make the primary side and the secondary side closely adhere, a conductive silicon wafer is attached to the contact portion on the secondary side. The advantage of series resonance is that not only is the circuit configuration simple, but also the method of changing the driving frequency can be dealt with when the junction capacitance changes. Only this method has a tendency to increase the applied voltage.

On the other hand, parallel resonance is reported to be in the trial stage of repeated simulation studies. The advantage of the parallel resonance is that the power can be efficiently transmitted even if the junction capacitance is lowered, and the applied voltage can be suppressed to a low level even when the output power is high. However, this method has a complicated problem of circuit configuration. Takenaka’s work shop said, “The goal is to achieve practical use around 2012”

Fast charging is a big success in the field of power tools

Although the non-contact charging technology has a great rise, the early stage of its application is the adoption of fast-charging lithium-ion batteries. In fact, existing products have increased sales by using fast-charging lithium-ion batteries, which has increased sales. This is the power tool.

The adoption of power tools for lithium-ion rechargeable batteries began in 2004-2005 and has expanded rapidly in recent years. MAKITA, one of the largest manufacturers of power tools, said that the global supply of lithium-ion rechargeable battery packs for power tools is increasing rapidly. It was only 1 million units in the first quarter of 2005 and increased to 4 million in the first quarter of 2006. The unit increased to 9 million units in the first quarter of 2007 and further increased to 13 million units in the first quarter of 2008.

Goto Zongli, the head of the development planning department of the technical management department of Makita Development Technology, said frankly, "We have been dubious about whether to replace the nickel-metal hydride rechargeable battery with a lithium-ion rechargeable battery." The main reason for the rapid expansion of market demand is that lithium-ion rechargeable batteries have the advantages of light weight and almost the same output power characteristics as plug-in type, plus fast charging function that can be fully charged in as little as 15 minutes (Figure 3). ).

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