Design Of Negative Voltage DC-DC Converter For OLED-on-silicon

In recent years,micro display technology has developed rapidly.Especially the organic light-emitting diode(OLED)technology,because it uses a more complete CMOS process,the pixel matrix and the corresponding drive circuit are made on the same monocrystalline silicon substrate.With the advantages of small size,fast response speed,easy to carry,low power consumption,high resolution,wide operating temperature range and so on,it has become a hot research field of micro display,and has a wide range of applications in military,medical,industrial and consumer electronics fields.OLED-on-silicon needs negative voltage all the way to drive the pixel circuit,so providing negative voltage all the way is one of the important topics in the research of OLED-on-silicon.The purpose of this paper is to design a negative voltage DC-DC converter to provide a negative voltage to the common cathode of OLED-on-silicon micro-display driver chip.In this paper,a negative pressure Cuk converter is designed.The content of this paper is mainly divided into two parts.The first part describes the topology of Cuk.The main device parameters,including capacitance,inductance,current detection resistor,power MOSFET and diode,were obtained by calculating Cuk topology structure with opposite polarity of input and output.The second part is pulse width modulation(PWM)circuit,based on pulse width modulation,the peak current mode control method combining inner loop current feedback and outer loop voltage feedback is selected for the switching control circuit of negative voltage DC-DC converter.When the peak current mode control method is used,the inductor current must be detected.In this paper,the proportional tube method is used to detect the inductor current,which makes the power loss smaller and the accuracy is higher.After the overall structure is determined,the stability of the system is discussed.The problem of subharmonic oscillation exists in the inner loop current feedback,and slope compensation circuit is needed.The outer loop is voltage feedback,and the resistor-capacitor compensation network is used to ensure that the circuit has sufficient phase margin.Then the PWM sub-module circuit is designed,including band gap reference,slope compensation circuit,integral circuit,error amplifier,comparator,oscillator,RS trigger and drive circuit.The drive circuit adopts a low power consumption non-overlapping drive circuit to reduce the transmission current loss.The oscillator module uses a new low-temperature drift-ring oscillator structure with a frequency offset rate of 3.2% in the temperature range from-40? to 125?.Finally,the simulation and layout design were carried out under 0.18?m BCD process.The simulation results show that the output voltage is dynamically adjustable in the range of-1?-6.495 V under the switching frequency of 2MHz and the supply voltage of 5V,the ripple of the output negative pressure is stable within 3m V,the line regulation rate is less than 20 m V/V,the load regulation rate is less than 1m V/m A,and the conversion efficiency reaches 88%.