NTT Corp, Seiko Instruments Inc and Seiko Epson Corp jointly developed a wireless system that runs on a small thermal generator.
They revealed the new system at the IEEE International Solid-State Circuits Conference in 2003 (ISSCC 2003).
In a ubiquitous environment in which all locations including human bodies are to be connected via a network, one of the important issues is to secure a power source. Because it is expected that such an environment can be realized in the near future, the three companies’ research attracted substantial attention. The ISSCC 2003 had to set up another room where the overflowing audience could watch the presentation through video-cast.
The newly developed system uses “thermolelectric” (TE) as a power generator to produce a voltage from a temperature difference. It is equipped with two panels. One panel is cooled down to 10 degrees centigrade with cold water and the other panel is warmed with body heat up to 30 to 40 degrees centigrade. The temperature difference between the two panels produces a potential difference of hundreds of mV. In the demonstration, a 1V potential difference was brought about five seconds after a person started to warm one panel of the system in his hand, which lasted for 60 seconds.
The power produced drives a receiving circuit and a control circuit of the wireless appliances via a DC-DC converter of a switched-capacitor type. The receiving circuit uses a weak electric wave of 300MHz. The DC-DC converter provides a voltage of about 1V. The digital circuit for control is provided with 0.5V.
In addition, the three companies developed a transmitter without any power source except for an internal solar battery. They conducted a communication test with the receiver and the transmitter, and succeeded in communicating within five meters.
The newly developed system requires semiconductor technology for low voltage and low-power consumption. It was realized through the integration of NTT’s MT-CMOS technology and silicon on insulator (SOI) know-how, and low-power consumption technology, which was originally for wristwatches of Seiko Instruments and Seiko Epson.
Seiko Instruments developed the technology of the thermal electricity generator.