High Efficiency And Low Ripple Positive And Negative Charge Pump Design Based On Linear/Skip Mixed Modulation Mode

With the developing of the display technology, TFT-LCD has become themainstream of the LCD or even the entire flat panel display technology, and this put therequirement of TFT-LCD integrated power supply solution forward higher. This paperbased on the design of the cooperation subject―the Theoretical Research and Design ofPower Management Unit’s Key Technology for LCD TVs―of Huazhong University ofScience&Technology, and the author take the major responsibility of the Design ofPositive and Negative Charge Pump Based on Linear/Skip Mixed Modulation Mode.This paper gives a comprehensive and systematic introduction to TFT-LCD gatedriving and power supply demands, then a reasonable power supply solution is presented.According to the widely used working methods and modulation mode of the TFT-LCDgate driver, at first we do a system analysis of the working principle, control theory andtechnical parameters of the charge pump, we proposed a modulation method combine“Linear” and “Skip” mode as to reduce the output ripple and improve system efficiency.The set-up and set-down circuit adopt the same control mode and symmetrical structures,this will greatly simplified the design work. Fixed dead time in between the two outputdriving clock prevent the high-side PMOS and the low-side NMOS power transistors fromturning on at the same time, which will result in a larger leakage current and lowerconversion efficiency. In addition, internal soft-start and complete fault protection circuitare integrated to ensure the system working stable.After the analysis and design of the circuit, based on the0.5μm mixed high and lowvoltage CMOS process, the design of this paper has been simulated and verified byHSPICE. The simulation results of performance and electrical characteristics indicate thecharge pump proposed in this paper perfectly meet the prospective specification.