Tft-lcd Gate Drive Power Supply Circuit Design

Recently, driven by the extensive applications of the TFT-LCD (Thin-Film Transistor Liquid-Crystal-Display) panel monitors, integration technologies related to TFT-LCD panel monitors such as the power supply components have been developed rapidly. Currently, those power supply components, which are capable of providing complete and high-integrated solutions in small sizes, are aggravated by the growing market. Therefore, a complete power supply solution realized by charge pump circuits is analyzed and designed according to the requirements of TFT-LCD gate driving systems. Using 0.6μm BCD process, two charge-pumps and a voltage reference are integrated to provide 27V, -5V and 5V outputs from 12V inputs. Furthermore, over-thermal and under-voltage protections are provided.In this paper, TFT-LCD driving principles are first introduced, and then theories as well as key parameters of charge pump are analyzed. Based on them, a multi-output system is designed for the TFT-LCD gate driving IC. Then, according to requirements of the system and the BCD process, the author pays great attention to the design of the typical practical sub-blocks, including a reference block, a level-shift block, an amplifier circuit, protection circuits and a ring oscillator. These sub-block circuits and the dc-dc system are simulated in HSPICE. The simulation results indicate that the system fulfills all system requirements, both in function targets and electrical characteristics. In the end, ESD(Electro-Static discharge,ESD) is analyzed and an ESD protection solution for this system is designed.Multi-output integration design and ESD protection design are the key points of this paper.3X positive charge-pump and -1X negative charge-pump are integrated, which allow the same inner-controlled circuits. This provides a significant simplified design project for the whole-circuit design, especially for back-end design. Meanwhile, power-switch circuit provides intelligent control on the positive charge-pump.This paper focuses on simplifying design process and lowering down the power dissipation. A voltage reference is introduced to convert 12V-input to 5V-output, which provides a lower power voltage for inner-circuits, in order to avoid higher power loss because of higher power voltage.According to the system's requirement and the process's capability, a complete ESD protection strategy is designed for mixed-voltage system. Diode and LDMOS are chosen either for low-voltage circuits or for high-voltage circuits and artful layout of the ESD devises is done to satisfy the special need. This protect solution provides pin-to-pin protecting circuits for the whole chip.