Murata Manufacturing Co Ltd developed the "direct current resonance" method as a new technology for wireless power transmission.
The direct current resonance method converts direct-current (DC) electrical energy into electromagnetic field energy and transmits electricity by using a physical phenomenon called "electromagnetic resonance field."
Murata has been engaged in the development of the new technology based on a research on the "magnetic resonance" method, which the company announced at an international academic conference in 1994, in cooperation with Doshisha University since 2009. For the future, it aims to commercialize the technology for supplying power to relatively low-power-consumption devices such as smartphones, tablet computers, battery-powered compact electronic devices and data communication cards.
The magnetic resonance method amplifies electricity from an alternating-current (AC) power source and converts it into DC electricity on the power-receiving side. On the other hand, the new method forms a resonance field directly from a DC power source, improving energy conversion efficiency.
Also, while the old method requires converting electricity four to six times, Murata aims to reduce the number of conversions to one (from electrical energy into electromagnetic field energy) with the new method so that the sizes, weights and power consumptions of devices can be reduced.
Furthermore, it becomes possible to feed electricity to multiple devices by making improvements to the power-transmitting, power-receiving and resonance devices to expand a resonance field, the company said.
According to Murata, the advantages of the direct current resonance method over other methods are as follows. First, unlike the magnetic resonance method, it does not require a complicated architecture and can reduce the size and weight of a device and improve the power efficiency of a system.
Second, unlike the electromagnetic induction method, the new method allows to more freely place power-transmitting and power-receiving devices and does not require a heavy magnetic material (iron) or coil (copper). Third, unlike the electric field coupling method, it realizes a longer transmission range and does not require a physical contact.
Fourth, compared with the radio transmission method, the new method can transmit a larger amount of power and enables to use smaller power-transmitting and power-receiving devices.
Murata has applied for 12 patents related to the direct current resonance method including basic patents and is preparing to apply 20 more. The company aims to commercialize the technology for relatively low-power-consumption applications in house and considers licensing it or providing technical support for relatively large-power-consumption applications such as electric vehicles.