Book contents
- Frontmatter
- Contents
- Preface
- 1 Introduction
- 2 Design considerations
- 3 Hybrid voltage–current programming
- 4 Enhanced-settling current programming
- 5 Charge-based driving scheme
- 6 High-resolution architectures
- 7 Summary and outlook
- Appendix A Enhanced voltage driving schemes
- Appendix B OLED electrical calibration
- References
- Index
3 - Hybrid voltage–current programming
Published online by Cambridge University Press: 05 September 2013
- Frontmatter
- Contents
- Preface
- 1 Introduction
- 2 Design considerations
- 3 Hybrid voltage–current programming
- 4 Enhanced-settling current programming
- 5 Charge-based driving scheme
- 6 High-resolution architectures
- 7 Summary and outlook
- Appendix A Enhanced voltage driving schemes
- Appendix B OLED electrical calibration
- References
- Index
Summary
This chapter presents accelerated programming/resetting of active pixel circuits based on bias currents presented in [87]. The settling time in current programming depends strongly on the VT of the drive transistor and initial line voltage (V0). Figure 3.1 shows the settling time of the pixel circuit depicted in Figure 2.5(a) as a function of the initial voltage. It is evident that the settling time changes as the initial voltage changes. As a result, since the voltage of the previous pixel remains on the data line, the programming of the new pixel is affected. Pre-charging the data lines to a specific voltage can control the effect of the initial voltage, but this can increase the power consumption considerably. Moreover, initial voltage is a function of the VT. Thus, the settling time cannot be managed by a fixed pre-charging voltage, because the value of VT is varying.
Thus, a dynamic line pre-charging scheme, coupled with a large current, is required to improve the settling time. To develop this driving scheme, a fix current is required to program the pixels so that the initial voltage becomes independent of the pixel content. Also, in-pixel current reduction/division is used to adjust the pixel current accordingly. This driving scheme is called the current-biased voltage-programmed (CBVP) scheme [86, 87].
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- Information
- Thin Film Transistor Circuits and Systems , pp. 46 - 73Publisher: Cambridge University PressPrint publication year: 2013