A Voltage Mode PWM Inverting Buck-Boost Converter for OLED Display

Abstract

In global display market, the preference of Organic light emitting diode (OLED) panel is gradually increased due to the properties of OLED such as improved image quality and design merits. To drive OLED panel, bipolar supplies are required. And these voltages can be generated by boost converter and inverting buck-boost converter. Among them, inverting buck-boost converter is needed to be used high voltage MOSFETs (HVMOS) due to the voltage stress of power MOSFETs. By the size of HVMOS, the efficiency of inverting buck-boost converter is decreased. And the efficiency of inverting buck- boost converter needs to be increased for driving pixel circuit at light load condition. In this thesis, voltage mode PWM inverting buck-boost converter for OLED is proposed. Through type-3 compensation, the converter is stable with wide range of variable voltage, and variable load current. And the system can achieve low line regulation and load regulation by well-controlled PWM loop. And then, without HVMOS, negative level shifter is designed, which is small size and short delay time. That negative level shifter delay is shorter than delay of other negative level shifter that uses HVMOS. Through these blocks, power consumption of the converter is decreased during switching time, and the efficiency of the converter is increased.