| TFT-LCD (Thin-Film Transistor Liquid-Crystal-Display) has been developed fastly and applied widely in recent years. Due to its high definition, high resolution, low power dissipation and easy to large-scale production, the TFT technology has become the mainstream of flat panel display manufacturing. Thus the power management solution for TFT-LCD must be improved to meet higher requirements.A monolithic multi-output integrated power management system XD1475 with high efficiency and low cost is presented in this paper. XD1475 could be used to power large screen TFT-LCD panel and its drive chips. The circuits, such as soft-start, perfect fault detection and protection circuits are also included. The positive and negative charge pumps with high system efficiency based on linear and skip control mode are focused on in this paper. The positive charge pump with 3 times output and the negative charge pump with -1 time output provide gate voltages to turn on or off the TFT.Firstly, the development and research status of LCD and TFT-LCD technology are briefly introduced in the paper. The drive principle and power requirements are described in detail, and then a reasonable power supply scheme is proposed. Secondly, the operation principle, main parameters and control mode are described systematically. Based on loop stability research of current mode charge pump, an effective small signal model is proposed for the system stability design. Finally, the system architecture of XD1475 and some main sub-circuits are introduced. The auto-zeroing error amplifier is designed particular to cancel the offset dynamically.Based on 0.6μm 40V BCD process, the sub-blocks and whole circuits have been simulated by Cadence. The simulation results show that all functions and performances can meet the design requirements. |
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