Takayuki Ouchi

9.1: A 3.5-inch OLED Display using a 4-TFT Pixel Circuit with an Innovative Pixel Driving Scheme

A new pixel circuit for the “clamped inverter driving method” reported previously is developed. The pixel circuit is composed of four TFTs, one capacitor and five signal lines including power supply. A 3.5-inch OLED display with the proposed new pixel circuit has been fabricated by LTPS processing and COG of an existing LCD driver chip. A vertical scanning circuit and selector switches are integrated in the panel. The proposed driving scheme is confirmed as OLED display to produce 6-bit gray-scale, gamma correction, and peak luminance with clear full-color images.

51.1: A 2.5‐inch OLED Display with a Three‐TFT Pixel Circuit for Clamped Inverter Driving

A new pixel circuit for “clamped inverter driving” was developed. Since a PMOS inverter is applied instead of the conventional CMOS for the pixel circuit, the circuit is simplified and is composed of only three TFTs. A simulation of gray-scale characteristics verified that this pixel circuit can compensate variation in Vth and carrier mobility. A 2.5-inch OLED display based on the new pixel circuit was fabricated by LTPS processing and achieves 6-bit gray-scale and good uniformity.

Parallel Bi-directional DC-DC converter for energy storage system

A scalable parallel bidirectional DC-DC converter system has been developed and evaluated. Fast and efficient seamless control is achieved by using an H-bridge topology. Although the control structure is simple, four drive modes can be handled. It was extended for use in simple parallel converter management. A parallel function auto-rotation scheme is used to control which units are active on the basis of tracked power. This method achieves high efficiency over a wide load range, especially for light loads. The automatic rotation of which converter acts as the output master distributes the load more evenly, resulting in less load damage. The only hardware required are a power line and communication cable connection. All other functions are provided by software and operate autonomously. A 5-kW prototype converter was constructed and evaluated in a three-unit parallel converter system. The estimated efficiency for 15-kW rated discharge was 97.8% for 333-V battery pack power and 380-V DC-link power.

Stable startup of seamless controlled parallel bidirectional DC-DC converter

A smart control method for Bidirectional DC-DC Converter has been developed. Both charge and discharge with buck / boost mode transition are achieved by common control structure without mode judgment. This simple structure is also extended to a parallel system, and controls multiple output power for both directions. The function has some exceptional case at the period of start-up and stop, because introduced complementary switching flows unexpected reverse current. To avoid the unexpected reverse current, we introduced the selective disable function of complementary switching and achieved stable start and stop control. This improvement also equipped the system additional charge only operation. Improved control structure was evaluated at the four-parallel converter system.

Seamless controlled parallel bi-directional DC-DC converter for energy storage system

A scalable parallel bidirectional DC-DC converter system, which enables efficient seamless control using an H-bridge topology, was developed and evaluated. Although the unified control structure is simple, four drive-mode, both charge and discharge with buck/boost, can be handled. The proposed system was extended for use in simple parallel converter management. This scheme achieves high efficiency over a wide load range, especially for light loads. The only hardware required is a power line and communication cable connection. All other functions are provided by software and operate autonomously. A 5-kW prototype converter was constructed and evaluated, and a four-unit parallel converter system was tested and confirmed to work well, changing load between 20-kW discharge and 20-kW charge.

A new driving method introducing a display period for AMOLEDs

— We have proposed an Advanced-Clamped-Inverter driving method for the fabrication of AMOLEDs, in which one frame period is divided into an addressing period and a display period. This driving method enables the AMOLEDs to produce excellent moving images without motion blur and false pixels, and has peak-luminance characteristics because of its unique light-emission scheme of the OLED elements. Good inter-pixel uniformity was also achieved in a previous clamped-inverter driving method. We fabricated AMOLEDs and experimentally confirmed their characteristics.