A Wide-Range Negative Output DC-DC Converter with Adaptive Drive Technique for Active-Matrix OLED Microdisplays

This paper presents a DC-DC converter with wide-range negative output for active-matrix organic light-emitting diode (AMOLED). The generated negative voltage Vout is connected to the negative terminal of the organic light-emitting diode (OLED), and the luminous brightness is adjusted by changing the value of Vout. The negative output voltage of the DC-DC converter is regulated by a Buck–Boost topology structure with a dual-loop control (DLC) system composed of a voltage loop and a current loop. The proposed compensatory peak-current-sensing technique (PCST) and switch MOSFETs adaptive drive technique (ADT) successfully support the implementation of the converter topology and enable the converter to work in continuous conduction mode (CCM). In addition, with the DLC system, the converter can guarantee a negative output voltage that enables both a fast transient response such as excellent load/line regulation, and a small output voltage ripple of the pulse width modulation (PWM) control. The proposed chip is implemented in a 0.18 μm CMOS process that operates at an operating frequency of 2 MHz with a maximum efficiency of 85.82%. The output voltage ripple is 1.5 mV at typical loading of Vout=−4 V and Iout=100 mA.