Toshiba develops wide load range efficient multi-output DC converters for iot applications

     Toshiba Corporation has announced the development of an on-chip single inductance Multiple Output (SIMO) direct current (DC-DC) converter for Internet of Things (IoT) devices powered by button-down lithium-ion batteries. The new converters will not only achieve 65-86% efficiency in the load range from 1μW to 50mW, which is more than 100 times the breadth of traditional SIMO DC converters, but will also extend the battery life of iot devices. The technological advance was announced on November 9 at the 2016 Asian Solid State Circuits Conference (A-SSCC) hosted by the Institute of Electrical and Electronics Engineers (IEEE) in Toyama, Japan.

     Integrated circuits (ics) powered by small capacity button lithium-ion batteries are increasingly used in a variety of iot applications and need to operate at the minimum supply voltage in each circuit to save energy. In the past, to supply multiple voltages, it was necessary to install multiple external inductors inside the DC converter, but SIMO DC converters require only one external inductor. This advantage of reduced equipment cost and capacity has inspired extensive SIMO DC converter development.

     Since iot devices operate most of the time in standby mode (power consumption below 1mW) and only a small part of the time in active mode (power consumption in the tens of milliwatts), SIMO DC converters must support a wide load range and high conversion efficiency. However, traditional SIMO DC converters are not designed for iot applications and cannot support such a wide load range and practical efficiency.

     Toshiba has improved the efficiency of SIMO DC converters in the light load range. The highly sensitive comparator of the traditional control circuit will be replaced by a new control circuit 1 consisting only of logic gates to reduce its power consumption. In addition, the proposed operation mode can reduce the switching frequency of current distribution to each output channel. As a result, Toshiba's new SIMO DC converter achieves more than 80% efficiency at load power above 5μW, and about 65% efficiency at load power of 1μW.

     Toshiba has also improved efficiency in the tens of milliwatts load range. To prevent interference between the output channels of SIMO DC converters, traditional analog controls have to wait a relatively long time before the channel is converted, resulting in reduced efficiency in this load range. The newly introduced SIMO DC converter utilizes digital feedback control to minimize waiting times.

     This architecture supports Toshiba's SIMO DC converter in achieving 65-86% actual efficiency over a wide load range from 1 μW to 50 mW . Conversion efficiencies of more than 60% operate over 100 times the load range of traditional SIMO DC converters, and the new SIMO DC converters extend the battery life of iot devices powered by button-down lithium-ion batteries.